Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsami.4c19936

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.langmuir.4c03985

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

CdSe/ZnS quantum dots (QDs) that were highly dispersed in porous glass showed a rapid decrease in the intensity of their photoluminescence (PL) in response to ozone at concentrations of 0–200 ppm in air (at room temperature and atmospheric pressure), followed by a similarly rapid recovery to full PL in air with no ozone. The response time of the PL quenching in the presence of ozone, and the recovery time to full PL in air after the ozone was removed, showed little dependence on the ozone concentration. Compared to conventional CdSe/ZnS QD films on planar glass substrates, the speed of ozone-induced decrease in the PL intensity of QDs increased, and the recovery speed of the PL intensity, once the ozone was removed from the air, was even more rapid compared to the recovery on planar glass. The 100% PL intensity recovery time in air was reduced to about 10% for CdSe/ZnS QDs that were dispersed in porous glass compared to CdSe/ZnS QD films on planar glass substrates. We hypothesize that this reflects the fact that ozone molecules that are adsorbed on the QD-layer-lined pore surfaces are quickly desorbed in ozone-free air, because the layer of CdSe/ZnS QDs is much thinner in the pores of porous glass than on a planar glass substrate. Thus, CdSe/ZnS QDs that were dispersed in porous glass showed a rapid response to ozone and a similarly rapid recovery in ozone-free air, which has not been seen in previous QD ozone gas sensors, indicating that they are promising as high-performance optical ozone sensor materials.

File： chemosensors-12-00254-v2.pdf

DOI： 10.3390/chemosensors12120254

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

File： advpub_A0162.pdf

DOI： 10.5702/massspectrometry.A0162

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.apmt.2024.102419

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Gold nanoparticles (AuNPs) possess attractive electronic, optical, and catalytic properties, enabling many potential applications. Poly(N-isopropyl acrylamide) (PNIPAAm) is a temperature-responsive polymer that changes its hydrophilicity upon a slight temperature change, and combining PNIPAAm with AuNPs allows us to modulate the properties of AuNPs by temperature. In a previous study, we proposed a simpler method for designing PNIPAAm–AuNP hybrid microgels, which used an AuNP monomer with polymerizable groups. The size of AuNPs is the most important factor influencing their catalytic performance, and numerous studies have emphasized the importance of controlling the size of AuNPs by adjusting their stabilizer concentration. This paper focuses on the effect of AuNP size on the catalytic activity of PNIPAAm–AuNP hybrid microgels prepared via the copolymerization of N-isopropyl acrylamide and AuNP monomers with different AuNP sizes. To quantitatively evaluate the catalytic activity of the hybrid microgels, we monitored the reduction of 4-nitrophenol to 4-aminophenol using the hybrid microgels with various AuNP sizes. While the hybrid microgels with an AuNP size of 13.0 nm exhibited the highest reaction rate and the apparent reaction rate constant (kapp) of 24.2 × 10−3 s−1, those of 35.9 nm exhibited a small kapp of 1.3 × 10−3 s−1. Thus, the catalytic activity of the PNIPAAm–AuNP hybrid microgel was strongly influenced by the AuNP size. The hybrid microgels with various AuNP sizes enabled the reversibly temperature-responsive on–off regulation of the reduction reaction.

File： gels-10-00357-v3.pdf

DOI： 10.3390/gels10060357

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.matlet.2024.136238

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

The freezing method used to prepare DNA-modified gold nanoparticles (SNA) has the advantages of being fast and simple, but the prepared SNA is easy to aggregate. In this paper, the effects of polyethylene glycol (PEG) as an organic macromolecular crowding agent on the single-strand polyadenylate DNA functionalized gold nanoparticles (polyA-SNA) and the single-strand thiolated DNA functionalized gold nanoparticles (HS-SNA) were systematically studied. The experimental results showed the molecular weight and concentration of PEG significantly affect the dispersion and DNA loading of the two kinds of SNA. An increase in DNA strand length inhibits the adsorption of thiolated DNA and polyA-DNA, and the hydrated particle size of SNA increases at first and then decreases with the length of the DNA strand. These phenomena lay on the speculative principle that PEG improved the energy barrier for gold nanoparticles (AuNPs) aggregation through the long chain of macromolecules, and the modification mode and length of surface DNA also play an auxiliary role. This work provided a systematic study and helpful results on improving the stability of SNA prepared by the freezing method.

DOI： 10.1016/j.colsurfa.2024.133349

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.matchemphys.2023.128844

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society on Water Environment  

File： 22_24-026.pdf

DOI： 10.2965/jwet.24-026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.macromol.3c01659

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DOI： 10.11364/networkedpolymer.44.6_275

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

File： d3ra06571e.pdf

DOI： 10.1039/d3ra06571e

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsabm.3c00518

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Society of Powder Technology, Japan  

DOI： 10.4164/sptj.60.429

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

Hypothesis: Gallium-based room-temperature liquid metals (LMs) have unique physicochemical properties; however, their high surface tension, low flowability, and high corrosiveness to other materials limit their advanced processing (including precise shaping) and application. Consequently, LM-rich free-flowing powders, named “dry LMs” that offer the inherent advantages of dry powders, should play a critical role in expanding the application scope of LMs. Experiments: A general method of preparing silica-nanoparticle-stabilized LMs in the form of LM-rich powders (>95 wt% LM) is developed. Findings: Dry LMs can be simply prepared by mixing LMs with silica nanoparticles in a planetary centrifugal mixer in the absence of solvents. As a sustainable dry-process route alternative to wet-process routes, this ecofriendly and simple method of dry LM fabrication has several advantages, e.g., high throughput, scalability, and low toxicity owing to the lack of organic dispersion agents and milling media. Moreover, the unique photothermal properties of dry LMs are used for photothermal electric power generation. Thus, dry LMs not only pave the way for the use of LMs in powder form but also provide a new opportunity for expanding their application scope in energy conversion systems.

DOI： 10.1016/j.jcis.2023.06.137

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Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Herein, improving the antibacterial activity of a hydrogel system of sodium alginate (SA) and basic chitosan (CS) using sodium hydrogen carbonate by adding AgNPs was investigated. SA-coated AgNPs produced by ascorbic acid or microwave heating were evaluated for their antimicrobial activity. Unlike ascorbic acid, the microwave-assisted method produced uniform and stable SA-AgNPs with an optimal reaction time of 8 min. Transmission electron microscopy (TEM) confirmed the formation of SA-AgNPs with an average particle size of 9 ± 2 nm. Moreover, UV-vis spectroscopy confirmed the optimal conditions for SA-AgNP synthesis (0.5% SA, 50 mM AgNO3, and pH 9 at 80 °C). Fourier transform infrared (FTIR) spectroscopy confirmed that the –COO− group of SA electrostatically interacted with either the Ag+ or –NH3+ of CS. Adding glucono-δ-lactone (GDL) to the mixture of SA-AgNPs/CS resulted in a low pH (below the pKa of CS). An SA-AgNPs/CS gel was formed successfully and retained its shape. This hydrogel exhibited 25 ± 2 mm and 21 ± 1 mm inhibition zones against E. coli and B. subtilis and showed low cytotoxicity. Additionally, the SA-AgNP/CS gel showed higher mechanical strength than SA/CS gels, possibly due to the higher crosslink density. In this work, a novel antibacterial hydrogel system was synthesized via 8 min of microwave heating.

File： jfb-14-00199-v2.pdf

DOI： 10.3390/jfb14040199

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.optmat.2023.113803

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

UNLABELLED: Rice husks are well known for their high silica content, and the RH-derived silica nanoparticles (RH NPs) are amorphous and biocompatible; therefore, they are suitable raw materials for biomedical applications. In this study, rose bengal-impregnated rice husk nanoparticles (RB-RH NPs) were prepared for their potential photosensitization and 1O2 generation as antimicrobial photodynamic inactivation. RB is a halogen-xanthene type's photosensitizer showing high singlet oxygen efficiency, and the superior photophysical properties are desirable for RB in the antimicrobial photodynamic inactivation of bacteria. To enhance the binding of anionic RB to RH NPs, we conducted cationization for the RH NPs using polyethyleneimine (PEI). The control of the RB adsorption state on cationic PEI-modified RH NPs was essential for RB RH-NP photosensitizers to obtain efficient 1O2 generation. Minimizing RB aggregation allowed highly efficient 1O2 production from RB-RH NPs at the molar ratio of RB with the PEI, XRB/PEI. = 0.1. The RB-RH NPs have significant antimicrobial activity against Streptococcus mutans compared to free RB after white light irradiation. The RB-RH NP-based antimicrobial photodynamic inactivation can be employed effectively in treating Streptococcus mutans for dental applications. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10853-023-08194-z.

DOI： 10.1007/s10853-023-08194-z

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Carbon nanodots can function as photosensitizers that have the ability to generate reactive oxygen species such as singlet oxygen, hydroxy (OH) radicals, and superoxide ions. However, most of these can only be generated upon ultraviolet light excitation. Additionally, the mechanism of reactive oxygen species generation by carbon nanodots remains unclear. The development of carbon nanodots that can photosensitize under visible light irradiation is desirable for applications such as photodynamic therapy and pollutant decomposition under visible light. Here, we report novel carbon nanodot‐based photosensitizers that generate reactive oxygen species under visible light; they were synthesized using a solvothermal method with two solvents (formamide and water) and amidol as the carbon source. Carbon nanodots from the solvothermal synthesis in formamide showed blue fluorescence, while those obtained in water showed green fluorescence. The photo‐excited blue‐fluorescent carbon nanodots produced OH radicals, superoxide ions, and singlet oxygen, and therefore could function as both type I and type II photosensitizers. In addition, photo‐excited green‐fluorescent carbon nanodots generated only singlet oxygen, therefore functioning as type II photosensitizers. It is proposed that the two photosensitizers have different origins of reactive oxygen species generation: the enrichment of graphitic N for blue‐fluorescent carbon nanodots and molecular fluorophores for green‐fluorescent carbon nanodots.

DOI： 10.1002/bio.4428

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/bio.4428

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

File： 11_A0107.pdf

DOI： 10.5702/massspectrometry.a0107

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcc.2c05404

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File： chemosensors-10-00482.pdf

DOI： 10.3390/chemosensors10110482

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Antimicrobial surfactants contained in mouthrinse have excellent efficacy, but are not retained on the tooth surface (are rinsed away) due to their low water resistance and thus do not exhibit sustained antibacterial activity. We have developed a new coating method using graphene oxide (GO) that retains the surfactant on the tooth surface even after rinsing with water, thus providing a sustained antibacterial effect. Ultra-thin films of GO and an antimicrobial agent were prepared by (1) applying GO to the substrate surface, drying, and thoroughly rinsing with water to remove excess GO to form an ultrathin film (almost a monolayer, transparent) on the substrate surface, then (2) applying antimicrobial cationic surface active agents (CSAAs) on the GO film to form a composite coating film (GO/CSAA). GO/CSAA formation was verified by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and ζ-potential and contact angle measurements. GO/CSAA was effective at inhibiting the growth of oral pathogens for up to 7 days of storage in water, and antibacterial activity was recovered by reapplication of the CSAA. Antibacterial GO/CSAA films were also formed on a tooth substrate. The results suggest that GO/CSAA coatings are effective in preventing oral infections.

File： s41598-022-21205-4.pdf

DOI： 10.1038/s41598-022-21205-4

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Other Link： https://www.nature.com/articles/s41598-022-21205-4

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d2cc02510h

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File： nanomaterials-12-02004.pdf

DOI： 10.3390/nano12122004

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

PDMS thimble was the key to combining incompatible reactions to achieve deracemization of 1-phenylethanols in high yield with high optical yield.

File： d2ra01326f.pdf

DOI： 10.1039/d2ra01326f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

We report here a novel, sensitive detection method for nitrogen dioxide (NO2) using thin films of CdSe/ZnS core-shell type quantum dots (QDs) with and without noble metal (NM) nanoparticles (Au, Pt, or Pt-Pd alloy) deposited on a glass substrate. The photoluminescence (PL) intensity of the QD-only film and NM-QD composite films with porous microstructure rapidly decreased on exposure to NO2 (1-100 ppm) in air, and it reversibly recovered after the atmosphere was changed back to air without NO2. Interestingly, the Au-QD, Pt-QD, and PtPd-QD films showed higher sensitivity when compared with the QD-only film. The reversible responses of QDonly film, Au-QD film, Pt-QD film, and Pt-Pd-QD film to NO2 in air suggested that the CdSe/ZnS QD film and NM-QD films could be promising PL-based optical NO2 sensors. Furthermore, the high NO2 sensitivity, but low ozone sensitivity, in the Pt-Pd-QD film suggests the possibility of recognizing these two oxidizing gases by using the gas-selective catalytic activity of Pd. (c) 2022 The Ceramic Society of Japan. All rights reserved.

File： 130_21088.pdf

DOI： 10.2109/jcersj2.21088

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DOI： 10.1021/acsami.2c00429

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

A mass spectrometric method for the simultaneous analysis of the enantiomeric excess of free amino acids, without chromatographic separation, was demonstrated using a quasi-racemic mixture of deuterium-labelled and unlabelled chiral Cu(<sc>ii</sc>) complexes.

File： d1ra06542d.pdf

DOI： 10.1039/d1ra06542d

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0055933

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DOI： 10.1021/acsami.1c04235

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Antibacterial photodynamic therapy (aPDT) utilizes reactive oxygen species such as singlet oxygen (1O2) and free radicals via photosensitizers, which are light and light-sensitive agents, to reduce bacterial infections. It has been utilized as a treatment for dental diseases in place of antibiotic therapies. However, aPDT does not always cause the desired therapeutic effect due to the instability of organic photosensitizers and the formation of bacterial biofilms. To promote the antibacterial and antibiofilm effects of aPDT, we have proposed a lysozyme (Lys)-gold nanoclusters (Au NCs)/rose bengal (Lys-Au NCs/RB) conjugate as a novel photosensitizer. This conjugate was found to effectively impede the growth of both gram-positive and gram-negative bacteria when exposed to white light-emitting diode (LED) irradiation. The photoexcited Lys-Au NCs/RB showed significantly higher antibacterial activity than photoexcited Lys-Au NCs or RB alone. The synergistic effect is a result of the combination of Lys (an antibacterial protein) and enhanced 1O2 generation related to resonance energy transfer (RET) in the Au NCs/RB conjugate. Photoexcited Lys-Au NCs/RB increased the effects of aPDT in a dose- and time-dependent manner. Furthermore, the photoexcited Lys-Au NCs/RB successfully decreased Streptococcus mutans biofilm formation. However, in contrast, it did not have a negative effect on the proliferation, adhesion, or spread of mammalian cells, indicating low cytotoxicity. Lys-Au NCs/RB is a novel photosensitizer with low cytotoxicity that is capable of bacterial inactivation and the suppression of biofilm formation, and could help to improve dental treatments in the future.

File： okamoto-et-al-2021-antibacterial-and-antibiofilm-photodynamic-activities-of-lysozyme-au-nanoclusters-rose-bengal.pdf

DOI： 10.1021/acsomega.1c00838

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DOI： 10.1016/j.colsurfa.2021.126360

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File： d0ra02835e.pdf

DOI： 10.1039/d0ra02835e

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jlumin.2020.117849

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.matlet.2020.128937

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Publishing type：Research paper (scientific journal)   Publisher：Nanocellulose: Synthesis, Structure, Properties And Applications  

DOI： 10.1142/9781786349477_0014

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Publishing type：Research paper (scientific journal)   Publisher：Frontiers Media SA  

A series of copper(II) complexes with chiral tetradentate ligands, <italic>N,N</italic>′-ethylene- bis(<italic>S</italic>-amino acid methyl amide or methyl ester) prepared from <italic>S-</italic>alanine, <italic>S-</italic>phenylalanine, <italic>S-</italic>valine or <italic>S-</italic>proline, was generated in methanol. The copper complexes provided three component complexes in the presence of a free chiral amino acid. The enantioselectivity for the amino acid was evaluated by electrospray ionization-mass spectrometry coupled with the deuterium-labeled enantiomer method and these copper complexes were found to exhibit high enantioselectivity for free amino acids having bulky side chains. This result suggests that steric interaction between the tetradentate ligand and free amino acid was a major factor in chiral recognition. The copper complex with a chiral tetradentate ligand prepared from <italic>S</italic>-proline showed opposite enantioselectivity to copper complexes consisting of tetradentate ligands prepared from other <italic>S</italic>-amino acids. The conformational difference of the tetradentate ligand in the copper complex was found to be significant for enantioselectivity.

File： fchem-08-598598.pdf

DOI： 10.3389/fchem.2020.598598

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

File： kawsaki_77.pdf

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

File： nanomaterials-10-01689-v2.pdf

DOI： 10.3390/nano10091689

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File： ishida-et-al-2020-synthesis-and-characterization-of-n-n-dimethylformamide-protected-palladium-nanoparticles-and-their.pdf

DOI： 10.1021/acsomega.0c01006

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Antibacterial photodynamic therapy (a-PDT) is a promising anti-infective technique for generation of singlet oxygen (1O2) to target dental disease. However, conventional organic photosensitizers have some problems for clinical use in terms of cytotoxicity, quenching of a-PDT activity by self-dimerization, and the lack of long-term antibacterial effect. We herein propose silver nanoclusters/rose bengal nanocomposite (AgNCs/RB) as a novel photosensitizer with two primary antibacterial effects: (1) 1O2 generation by irradiated RB and (2) Ag+ ion release from AgNCs. AgNCs/RB irradiated with white light-emitting diode (LED) for a short irradiation time of 1 min significantly decreased the bacterial turbidity of Streptococcus mutans, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans (P < 0.05). In SEM, TEM and LIVE/DEAD staining images, photoexcited AgNCs/RB reduced S. mutans colonization, destroyed the cell membrane, and increased the number of dead cells. The antibacterial efficiency of photoexcited AgNCs/RB was greater than that of AgNCs or RB alone (P < 0.05), suggesting a synergistic effect of 1O2 and Ag + ions from photoexcited AgNCs/RB. By contrast, photoexcited AgNCs/RB did not affect WST-8 and LDH activities and morphology of NIH3T3 mammalian cells, indicating low cytotoxicity. Interestingly, the antibacterial activity of AgNCs/RB on S. mutans was maintained even after the cessation of LED irradiation, indicating a long-term antibacterial effect due to released Ag+ ions. The present AgNCs/RB photosensitizers provide effective synergistic antibacterial effects for dental a-PDT via 1O2 and Ag+ ions coupled with low cytotoxicity.

DOI： 10.1016/j.pdpdt.2019.101647

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DOI： 10.1016/B978-0-12-822350-5.00009-6

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Language：English   Publishing type：Research paper (scientific journal)  

File： analsci.19P490.pdf

DOI： 10.2116/analsci.19P490

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：RSC  

File： c9na00583h.pdf

DOI： 10.1039/C9NA00583H

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Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Enantioselective coordination of a free amino acid as the second ligand of a Cu(<sc>ii</sc>) complex with a novel chiral tetradentate ligand was evaluated quantitatively in a short measurement time by ESI-MS/deuterium-labelled quasienantiomers.</p>

DOI： 10.1039/c9cc07231d

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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DOI： 10.1016/j.colcom.2019.100187

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Authorship：Last author   Language：English   Publisher：ナノ・バイオメディカル学会  

虫歯の病原菌であるStreptococcus mutansに対して審美的(象牙質変色予防)作用と抗菌的作用を持つ成分として、直径2nm未満の銀ナノクラスター(AgNC)を調製した。このAgNCはS.mutansの濁度と生存性を顕著に減少させるだけでなく、LIVE/DEAD染色法にて殺菌効果が認められた。このAgNCをヒト象牙質に適用すると、フッ化ジアミン銀を適用した場合と比べて象牙質の変色は認められず、AgNC-処理象牙質はS.mutansによるコロニー形成に対する阻害効果を示した。これらの結果から、AgNCは抗菌的・審美的基質として、歯科療法で有望と考えられた。

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10854-019-01571-y

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DOI： 10.1039/c9pp00035f

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DOI： 10.1021/acs.langmuir.8b01007

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcc.9b06849

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Ligand-protected silver nanoclusters (Ag NCs) have been gaining interest as antibacterial agents because of their ultrasmall sizes (<2 nm), their high antibacterial activity, and the variety of ligand species. The incorporation of Ag NCs into polymer resins is a desirable approach to achieve high durability and the long-term antibacterial activity of Ag NCs-based antibacterial coatings. However, the Ag NC-based antibacterial agents reported thus far are all water-soluble, and they have not been employed to generate antibacterial resins coatings because of the hydrophobic nature of the resins. Herein, we report for the first time Ag NC-based antibacterial photocurable acrylic resin coatings prepared by incorporating the conjugate of dihydrolipoic acid-capped Ag NCs with tetraoctylammonium (TOA) (TOA-Ag NCs). Given TOA's organosolubility, TOA-Ag NCs readily dissolved in the acrylic resin. The Ag NC-based antibacterial resin coatings displayed efficient antibacterial activity descending from the double antibacterial action of Ag NCs and TOA. This activity was maintained for a long time even after exposure of the coatings to aqueous environments. The cytotoxicity of the Ag NC-based antibacterial resin coatings was evaluated by measuring NIH3T3 cell proliferation and the expression of F-actin and vinculin, and data supported the low cytotoxicity of the coatings. These novel Ag NC-based antibacterial resin coatings have promising potential biomedical applications, for instance in healthcare/medical devices, for hospital infection prevention, and in implantable devices.

DOI： 10.1021/acsanm.8b01010

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DOI： 10.1098/rsos.172417

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

Great efforts have been devoted to the exploration of potential diagnostic and therapeutic applications of thiolate-protected gold nanoclusters (Au NCs). One of the therapeutic applications is the photosensitized generation of highly reactive singlet oxygen (1O2) using Au NCs for photodynamic therapy. However, there is scope for improving the 1O2-generation efficiency of Au NC photosensitizers. In this study, we exploit three strategies to improve the 1O2-generation efficiency of glutathione-protected Au NCs: (i) doping with silver (i.e., using bimetallic AuAg NCs, (ii) achieving aggregation-induced emission (AIE) using a Au(I)-thiolate complex, and (iii) achieving self-assembly-induced emission (SAIE) using a polymer nanogel. The combination of these three effects dramatically increased the 1O2-generation efficiency and enhanced the luminescence of the glutathione-protected Au NCs, owing to the inhibition of the nonradiative decay pathways. Finally, the photosensitizers based on AuAg NC@nanogel composites were successfully used for antimicrobial photodynamic therapy (a-PDT) against oral bacteria. This study provides general insights into the molecular design of water-soluble Au NC photosensitizers for therapeutic applications.

DOI： 10.1021/acs.jpcc.8b02373

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DOI： 10.1002/cctc.201800161

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Bovine serum albumin (BSA)-capped gold nanoclusters (BSA-Au NCs) are attractive photosensitizers for efficient singlet oxygen 1O2 generation owing to their high-water solubility, low toxicity, and the broad absorption from UV to visible wavelengths, and the long lifetime of the electronic excitations (of the order of microseconds). However, the 1O2 generation efficiency of BSA-Au NCs is relatively low. In the present study, a conjugate of BSA-Au NCs and methylene blue (MB) (BSA-Au NC-MB conjugate) has been developed to improve 1O2 generation for antimicrobial photodynamic therapy (aPDT). The BSA-Au NC-MB conjugate demonstrated enhanced 1O2 generation compared to the case of BSA-Au NCs and effective aPDT ability under white-light LED illumination for only 1min due to the resonance energy transfer from the Au NCs to the MB in the conjugate. To the best of my knowledge, this is first report of Au NCs on the resonance energy transfer application for efficient 1O2 generation. Therefore, the BSA-Au NC-MB conjugate is a novel photosensitizer for 1O2 generation that shows great potential for aPDT, and the present study also develops a very simple strategy to fabricate albumin-based nanoparticles for PDT.

DOI： 10.1016/j.jcis.2017.09.011

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

File： Ag7(MBISA)6 Nanoclusters Conjugated with Quinacrine for FRET-Enhanced Photodynamic Activity under Visible Light Irradiation.pdf

DOI： 10.3866/pku.whxb201710271

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Language：English   Publishing type：Research paper (scientific journal)  

Various apparently inconsistent experimental observations have been reported on the effects of electric charges on the volume phase transition of thermosensitive gels. A simple method of interpretating these results is presented.

DOI： 10.3390/gels4010024

PubMed

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Publishing type：Research paper (international conference proceedings)   Publisher：AMA Service GmbH, Von-Münchhausen-Str. 49, 31515 Wunstorf, Germany  

DOI： 10.5162/imcs2018/os1.3

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

File： 33_987.pdf

DOI： 10.2116/analsci.33.987

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Other Link： https://link.springer.com/article/10.2116/analsci.33.987/fulltext.html

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Paper-based electronics have been attracting significant attention because of their inexpensive, renewable, and eco-friendly substrates. In this study, Cu-based composite inks composed of a copper-based metal-organic decomposition (MOD) ink and Cu flakes were prepared as precursors to obtain conductive Cu films on untreated cellulose paper. Copper-based MOD inks have not been explored for the production of conductive Cu films on cellulose paper because the properties of the paper, such as high porosity, high permeability, and surface roughness, are not favorable to obtain continuous conductive Cu films. However, using our method, we have obtained Cu films on paper with resistivities that are similar to 10 times lower than those of films on polyimide or glass substrates. Importantly, the Cu films on paper exhibited better mechanical resistance than those on a polyimide substrate, without any pre-treatment of the paper surface. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2017.05.017

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

In electronic printing, ensuring high durability of sintered copper films on flexible substrates to obtain environmental stability and mechanical flexibility has become the most important task from a practical standpoint. In the study reported here, the authors develop solution synthesis of 2-amino-2-ethyl-1,3-propanediol (AEP)-protected copper nanoparticles (AEP-Cu NPs) with sizes of 3-8nm in ethylene glycol, where the Cu NPs are stabilized via the metallacyclic coordination stability of the AEP ligands. The sintered Cu film exhibits a resistivity of 50cm(-1) after heating at 150 degrees C under a nitrogen atmosphere. Most importantly, the resulting Cu films on the polyethylene terephthalate (PET) substrates show excellent durability in terms of bending and adhesion without requiring any additives like nanotubes and nanowires. Furthermore, the authors successfully demonstrated the high environmental stability of the resulting Cu film even after it is exposed to harsh environmental conditions (RH 80%, 60 degrees C) for 1 month. The environmental durability is further improved by utilizing a composite ink of AEP-Cu NPs with copper microflakes. It is experimentally proven that oxidation products from AEP ligands originating in the sintering process contributed to the high durability of sintered copper films on flexible substrates.

DOI： 10.1002/adem.201700259

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsami.7b04641

Scopus

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DOI： 10.1039/C6CC09279A

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We report methylations of alcohols and anilines catalyzed by DMFstabilized Ir nanoclusters using methanol as the C1 source. The DMFstabilized Ir nanoclusters were prepared in one step and have diameters of 1-1.5 nm. They react in a borrowing-hydrogen reaction and are efficient methylation catalysts (TON up to 310000).

DOI： 10.1039/c6cc09279a

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Authorship：Corresponding author  

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Language：English   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Cetyltrimethylammonium bromide (CTAB)-based surfactants are typically used as morphology-directing/stabilising agents for gold nanorods (AuNRs), forming bilayers on their surface. However, the biological applications of AuNRs require the removal of surface-bound CTAB due its high toxicity and the poor colloidal stability of CTAB-covered AuNRs in biological media. Herein, we report a simple and effective strategy for removing surface-bound cetyltrimethylammonium (CTA) cations from poly(ethylene glycol) thiolate-protected AuNRs (PEG-AuNRs) by treatment with dimethyl sulfoxide/citric acid (DMSO/Cit), achieving residual CTA ion levels that cannot be detected by highly sensitive mass spectrometry or X-ray photoelectron spectroscopy (XPS) techniques. The DMSO/Cit treatment is thought to destabilise the Ag-Br-CTA complex on AuNRs, since citric acid forms strongly bound chelate complexes with CTA cations.

File： c7ra02179h.pdf

DOI： 10.1039/c7ra02179h

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Language：English   Publishing type：Research paper (scientific journal)  

Antimicrobial photodynamic therapy (aPDT) has beneficial effects in dental treatment. We applied captopril-protected gold (Au25(Capt)18) clusters as a novel photosensitizer for aPDT. Photoexcited Au clusters under light irradiation generated singlet oxygen (1O2). Accordingly, the antimicrobial and cytotoxic effects of Au25(Capt)18 clusters under dental blue light-emitting diode (LED) irradiation were evaluated. 1O2 generation of Au25(Capt)18 clusters under blue LED irradiation (420-460 nm) was detected by a methotrexate (MTX) probe. The antimicrobial effects of photoexcited Au clusters (0, 5, 50, and 500 μg/mL) on oral bacterial cells, such as Streptococcus mutans, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis, were assessed by morphological observations and bacterial growth experiments. Cytotoxicity testing of Au clusters and blue LED irradiation was then performed against NIH3T3 and MC3T3-E1 cells. In addition, the biological performance of Au clusters (500 μg/mL) was compared to an organic dye photosensitizer, methylene blue (MB; 10 and 100 μg/mL). We confirmed the 1O2 generation ability of Au25(Capt)18 clusters through the fluorescence spectra of oxidized MTX. Successful application of photoexcited Au clusters to aPDT was demonstrated by dose-dependent decreases in the turbidity of oral bacterial cells. Morphological observation revealed that application of Au clusters stimulated destruction of bacterial cell walls and inhibited biofilm formation. Aggregation of Au clusters around bacterial cells was fluorescently observed. However, photoexcited Au clusters did not negatively affect the adhesion, spreading, and proliferation of mammalian cells, particularly at lower doses. In addition, application of Au clusters demonstrated significantly better cytocompatibility compared to MB. We found that a combination of Au25(Capt)18 clusters and blue LED irradiation exhibited good antimicrobial effects through 1O2 generation and biosafe characteristics, which is desirable for aPDT in dentistry.

DOI： 10.2147/IJN.S131602

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Open Access Text Pvt, Ltd.  

File： BEM-2-126.pdf

DOI： 10.15761/bem.1000126

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

In this study, we report a thiolate-protected Au nanocluster, Au-25(phenylethanethiol)(18) [Au-25(PET)(18)], which serves as an efficient catalyst by a three-component coupling reaction (A(3) reaction) of aldehydes, amines, and alkynes to give the corresponding propargylamines in good to excellent yields.

DOI： 10.1246/cl.160813

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Thiolate-protected Au-25 nanoclusters (NCs) have been shown to be efficient O-1(2) photosensitizers. The O-1(2)-generation efficiency of thiolate-protected Au NCs is expected to depend on the thiolate ligand species and size of the gold clusters. In the present study, Au25(glutathione)18 nanoclusters (Au-25(SG)(18) NCs) and bovine-serum-albumin (BSA)-protected Au-25 nanoclusters (BSA-Au-25 NCs) were synthesized to investigate the effect of different thiolate ligands on the O-1(2) generation. The efficiency of O-1(2) generation by the Au-25 NCs that were photo-excited at 532 nm was evaluated with methotrexate as a chemical probe. The effect of Au NC size on the O-1(2)-generation efficiency of thiolate-protected Au-18 and Au-25 NCs was also investigated. The O-1(2)-generation efficiency of BSA-Au25 NCs was higher than that of Au-25(SG)(18) NCs. The long lifetime of the electronic excitations and the high-photo-stability were key factors facilitating the formation of O-1(2) in BSA-Au-25 NCs. The effect of Au NC size on the O-1(2)-generation efficiency of thiolate-protected Au NCs, Au-n(SR)(m), decreased in the following order: Au-25(SR)(18) &gt; Au-18(SR)(14). (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2016.08.059

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

High molecular weight organic compounds (HMW-OCs), formed as secondary organic aerosols (SOA), have been reported in many laboratory studies. However, little evidence of HMW-OCs formation, in particular during winter season in the real atmosphere, has been reported. In January 2013, Beijing faced historically severe haze pollution, in which the hourly PM2.5 concentration reached as high as 974 mu g m(-3). Four typical haze events (HE1 to HE4) were identified, and HE2 (Jan. 9-16) was the most serious of these. Based on the hourly observed chemical composition of PM2.5 and the daily organic composition analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), we found that abundant ion peaks in m/z 200-850 appeared on heavy haze days, whereas these were negligible on a clear day, indicating the existence of HMW-OCs in the wintertime haze. A negative nonlinear correlation between HMW-OCs and 03 suggested that gas oxidation was not likely to be the dominant mechanism for HMW-OCs formation. During the heavy haze events, the relative humidity and mass ratio of H2O/PM2.5 reached as high as 80% and 0.2, respectively. The high water content and its good positive correlation with HMW-OCs indicated that an aqueous-phase process may be a significant pathway in wintertime. The evidence that acidity was much higher during HE2 (0.37 mu g m(-3)) than on other days, as well as its strong correlation with HMW-OCs, indicated that acid catalyzed reactions likely resulted in HMW-OCs formation during the heavy winter haze in Beijing. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.envpol.2016.07.004

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Lifescience Global  

Metal-organic decomposition (MOD) inks have been developed for printed electronics applications. Cu-based MOD inks prevent the oxidation of the metal during storage, as the Cu is already present in an oxidized form (i.e. a salt). However, usually hazardous formates such as Cu (II) formate have to be used as the copper salt in order to ensure thermal decomposition and self-reduction of the metal salt at moderate temperatures (less than 150°C). In this study, a formate-free hybrid ink containing copper particles and a Cu/1-amino-2-propanol (AmIP)/acetate complex was developed for the fabrication of conductive copper films on flexible polymer substrates at low sintering temperatures. A hybrid ink with a weight ratio of 3:1copper particles to MOD ink produced a conductive copper film with close-packed copper particles and a low resistance of 7.3—10-5Ω cm after sintering at a temperature of 180°C for 60 min under a N2 gas flow. Good oxidation resistance of the copper films was observed after exposure to air at 23 °C for two months.

File： document.pdf

DOI： 10.6000/2369-3355.2016.03.02.2

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

We report that both low electric resistivity and strong adhesion to polyimide film were attained for a conductive Cu film prepared by low-temperature sintering of 2-amino-1-butanol-protected Cu nanoparticles (AB-Cu NPs) with an average size of 4.4 nm. The sintering temperature of 60 A degrees C for the AB-Cu NPs is the lowest ever reported for Cu NPs. A nanoink comprising these AB-Cu NPs (similar to 35 wt% Cu) produced a conductive Cu film with resistivity of 52 mu Omega cm after heating at 150 A degrees C under a nitrogen flow. The adhesion to a polyimide film was compared for films prepared from nanoinks consisting of three different types of alkanol-amine-based Cu NPs: AB-Cu NPs, 1-amino-2-propanol-Cu NPs, and 3-amino-1-propanol-Cu NPs. Only the Cu film prepared from the AB-Cu nanoink established strong adhesion to the substrate without decreasing the electrical conductivity. The adhesiveness is attributed to residual oxidation products after thermal sintering of the Cu nanoinks.

DOI： 10.1007/s10854-016-4734-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Plant leaves administered with systemic insecticides as agricultural chemicals were analyzed using imaging mass spectrometry (IMS). Matrix-assisted laser desorption/ionization (MALDI) is inadequate for the detection of insecticides on leaves because of the charge-up effect that occurs on the non-conductive surface of the leaves. In this study, surface assisted laser desorption/ionization with a sputter-deposited platinum film (Pt-SALDI) was used for direct analysis of chemicals in plant leaves. Sputter-deposited platinum (Pt) films were prepared on leaves administered with the insecticides. A sputter-deposited Pt film with porous structure was used as the matrix for Pt-SALDI. Acephate and acetamiprid contained in the insecticides on the leaves could be detected using Pt-SALDI-MS, but these chemical components could not be adequately detected using MALDI-MS because of the charge-up effect. Enhancement of ion yields for the insecticides was achieved using Pt-SALDI, accompanied by prevention of the charge-up effect by the conductive Pt film. The movement of systemic insecticides in plants could be observed clearly using Pt-SALDI-IMS. The distribution and movement of components of systemic insecticides on leaves could be analyzed directly using Pt-SALDI-IMS. Additionally, changes in the properties of the chemicals with time, as an indicator of the permeability of the insecticides, could be evaluated.

File： analsci.32.587.pdf

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

The method for the quantitative analysis of fluoride anion employs a color change from purple-red to violet under the reaction of La(III)-alizarin-complexone(ALC) with the fluoride anion. We investigated the chemical species in a La(III)-alizarin-complexone(ALC) solution as well as its reaction solution with fluoride anion by using high-resolution mass spectrometry. As a result, the complexes present in a La(III)-(ALC) solution were estimated to be (La-ALC)(4-6), and their structure was an annulation consisting of (La-ALC) units. In these three complexes, only the (La-ALC)(4) complex reacted with fluorine ions to produce deprotonated complexes of [(La-ALC)(4)-H + LaF2] and [(La-ALC)(4)-2H + LaF]. This deprotonation of (La-ALC)(4) caused the solution to vary from purple-red to violet. (La-ALC)(5-6) complexes were not detected in a solution with excessive fluorine ions. This is because (La-ALC)(4) decreasing with complexation with the fluorine ions is thought to be supplied from the degradation of (La-ALC)(5-6). The same results were obtained in the system of Ce(III).

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Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

File： 5_S0054.pdf

DOI： 10.5702/massspectrometry.s0054

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Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

File： 5_A0045.pdf

DOI： 10.5702/massspectrometry.a0045

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Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.colsurfb.2015.12.037

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Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.bioconjchem.6b00455

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We presented the fabrication of a silver nanoparticle (Ag NP) functionalized glass fiber (Ag-GF) substrate for combined surface-enhanced Raman scattering spectroscopy (SERS)/surface-assisted laser desorption/ ionization (SALDI) mass spectrometry. Ag NPs were immobilized onto the surface of glass fibers through a simple sputter deposition process. The SERS and SALDI activities strongly depended on the nanostructures of the deposited Ag NPs on the GFs. The closely-packed Ag NPs with a size of 20-50 nm and an inter-particle nanoscale gap of less than 10 nm were effective for the simultaneously enhanced SERS/SALDI substrate via plasmonic/thermal "hot spots", while the interconnected continuous Ag film reduced both the SERS/SALDI activities. The SERS enhanced factor (EFSERS) and SALDI enhanced factor (EFSALDI) were newly proposed. Finally, the concentration-dependent signal intensities of SERS and SALD-MS of sulfur compounds using an identical Ag NP-GF substrate were examined, and the linear dependence relationship in the log-log plot was demonstrated for the combined quantitative SERS/SALDI-MS analysis.

DOI： 10.1039/c6an00511j

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

In this work, we first report the photo-mediated size-focusing synthesis of glutathione (SG)-protected atomically precise Ag nanoclusters (Ag NCs). This photo-mediated size-focusing synthesis comprises a two-step protocol: (i) the reduction of Ag ions by NaBH4 to form polydisperse Ag NC intermediates and (ii) the subsequent photo-mediated size-focusing of these intermediates under 365 nm UV irradiation, producing monodisperse Ag-32(SG)(19) NCs. The role of light in the size-focusing synthesis of Ag NCs was investigated. We have demonstrated that 365 nm UV light irradiation under air/O-2 is an important parameter for the synthesis of well-defined Ag NCs via the photo-mediated size-focusing process due to the UV light/oxygen-sensitive properties of Ag.

DOI： 10.1039/c6ra10892j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry (IMS) allows for the simultaneous detection and imaging of several molecules in brain tissue. However, the detection of glycerolipids such as diacylglycerol (DAG) and triacylglycerol (TAG) in brain tissues is hindered in MALDI-IMS because of the ion suppression effect from excessive ion yields of phosphatidylcholine (PC). In this study, we describe an approach that employs a homogeneously deposited metal nanoparticle layer (or film) for the detection of glycerolipids in rat brain tissue sections using IMS. Surface-assisted laser desorption/ionisation IMS with sputter-deposited Pt film (Pt-SALDI-IMS) for lipid analysis was performed as a solvent-free and organic matrix-free method. Pt-SALDI produced a homogenous layer of nanoparticles over the surface of the rat brain tissue section. Highly selective detection of lipids was possible by MALDI-IMS and Pt-SALDI-IMS; MALDI-IMS detected the dominant ion peak of PC in the tissue section, and there were no ion peaks representing glycerolipids such as DAG and TAG. In contrast, Pt-SALDI-IMS allowed the detection of these glycerolipids, but not PC. Therefore, using a hybrid method combining MALDI and Pt-SALDI (i.e., matrix-enhanced [ME]-Pt-SALDI-IMS), we achieved the simultaneous detection of PC, PE and DAG in rat brain tissue sections, and the sensitivity for the detection of these molecules was better than that of MALDI-IMS or Pt-SALDI alone. The present simple ME-Pt-SALDI approach for the simultaneous detection of PC and DAG using two matrices (sputter-deposited Pt film and DHB matrix) would be useful in imaging analyses of biological tissue sections. Copyright (c) 2015 John Wiley & Sons, Ltd.

DOI： 10.1002/jms.3700

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A simple, high-concentration (up to 0.6 M Cu salt) synthesis of sub-10-nm copper nanopartides (Cu NPs) was developed in ethylene glycol at room temperature under ambient air conditions using 1-amino-2-propanol (AmIP) as the stabilizer. Monodispersed AmIP-Cu NPs of 3.5 +/- 1.0 nm were synthesized in a high yield of similar to 90%. Thus, nearly 1 g of sub-10-nm Cu NP powder was obtained using a one-step synthesis for the first time. It is proposed that metallacyclic coordination stability of a five-membered ring type between the Cu and AmIP causes the high binding force of Am IP onto the Cu surface, resulting in the superior stability of the AmIP-Cu NPs in a solution. The purified powder of AmIP-Cu NPs can be redispersed in alcohol-based solvents up to high Cu contents of 45 wt % for the preparation of Cu nanoink. The resistivity of the conductive Cu film obtained from the Cu nanoink was 30 mu Omega. cm after thermal heating at 150 degrees C for 15 min under a nitrogen flow. The long-term resistance stability of the Cu film under an air atmosphere was also demonstrated.

DOI： 10.1021/acsami.5b05542

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We report the use of a DMF reduction method for straightforward synthesis of binary solid solution Cu-Pd nanoparticles (NPs) over the entire range of composition. The resulting NPs were uniform in size (less than 2.5 nm), tunable in composition, and exhibited photoluminescence properties that were nonlinear in composition. These binary solid solution NPs showed enhanced photoluminescence intensity and quantum yield compared to those of the single-metal NPs and their mixtures. The highest quantum yield of 3.10% for Cu-Pd alloy NPs synthesized using equimolar feeding ratio versus 2.75% for Cu and 0.71% for Pd NPs was obtained. These enhancements make the alloy NPs promising materials for optical applications.

DOI： 10.1039/c4tc02129k

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcc.5b03934

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Plasma medicine is an attractive new research area, but the principles of plasma modification of biomolecules in aqueous solution remain elusive. In this study, we investigated the chemical effects of atmospheric-pressure cold plasma on 20 naturally occurring amino acids in aqueous solution. High-resolution mass spectrometry revealed that chemical modifications of 14 amino acids were observed after plasma treatment: (i) hydroxylation and nitration of aromatic rings in tyrosine, phenylalanine and tryptophan; (ii) sulfonation and disulfide linkage formation of thiol groups in cysteine; (iii) sulfoxidation of methionine and (iv) amidation and ring-opening of five-membered rings in histidine and proline. A competitive reaction experiment using 20 amino acids demonstrated that sulfur-containing and aromatic amino acids were preferentially decreased by the plasma treatment. These data provide fundamental information for elucidating the mechanism of protein inactivation for biomedical plasma applications.

DOI： 10.1088/0022-3727/47/28/285403

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Structural identification of perfluoroalkyl and polyfluoroalkyl substances found in end-user products and their biodegradation products was performed using ultra-high resolution mass spectrometry. Little attention has so far been paid to the environmental burden of perfluorooctane sulfonate and perfluorooctanoic acid from compounds with a molar mass of similar to 2,000. Analysis of end-user waterproofing and stain repellent products revealed the presence of numerous ions with molar masses ranging from 1,000 to 2,000 and complex mass spectra. Ultra-high resolution mass spectrometry determined the accurate mass of the observed ions, allowing the cleavage position and fragment structure to be determined. The precursor structures were determined based on reconstitution of the retrieved fragments. Products of fluorochemical manufacturers before voluntary regulation comprised compounds with plural perfluorooctyl chains. In the current product lines, compounds comprising perfluorobutyl chains were detected. Biodegradation tests using activated sludge revealed that biodegradation products consistent with those reported previously were generated even from complex end-user products. For example, the biodegradation test revealed the formation of N-ethyl perfluorooctane sulfonamido acetic acid and various fluorotelomer acids in the samples. The results of the present study suggest that the environmental burden of these compounds should be reevaluated.

DOI： 10.1007/s00216-014-7862-0

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In this report, we demonstrate gold-decorated titania nanotube arrays (Au-TNA substrate) as a dual-functional platform for surface-enhanced Raman spectroscopy (SERS) and surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The Au nanopartides are grown on the substrate using vapor deposition of Au. The resulting substrates perform better than Au colloids in terms of the reproducibility of the SEAS measurements, long-term stability of the fabricated structures, and clean surface of the Au. The nanostructure of the Au-TNA substrate was designed to optimize the SALDI-MS and SERS performance. Excellent reproducibility of the SERS measurements using the Au-TNA substrate was obtained, with a standard error less than 6 %. SALDI activity was also demonstrated for the same Au-TNA substrates. Finally, the Au-TNA substrate was used for combined SERS and SALDI-MS analysis (i) to discriminate the structural isomers of pyridine compounds (para-, meta-, and ortho-pyridinecarboxylic acid) and (ii) to detect polycarbamate, a dithiocarbamate fungicide. These results are difficult to obtain using either approach alone.

DOI： 10.1021/am501291d

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

In this work, highly luminescent ovalbumin-protected Au nanoparticles (OVA-Au NPs) with a quantum yield of 9.3% for emission at 645 nm were demonstrated as a fluorescence probe for sensitive detection of glucose. The fluorescence of the Au NPs originated from the Au(I)-thiol (S) complex on their surfaces, and it was found to be quenched effectively by enzymatically generated hydrogen peroxide (H2O2). The OVA-Au NPs allowed the determination of glucose concentrations in the range varying from 1.0 x 10(-4) to 1 x 10(-2) M with a detection limit of 1 x 10(-5) M.

DOI： 10.1246/cl.140126

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Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c4cc01855a

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/cm500260z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

File： 3_A0026.pdf

DOI： 10.5702/massspectrometry.a0026

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Language：English   Publisher：The Mass Spectrometry Society of Japan  

We report the application of tapping-mode scanning probe electrospray ionization (t-SPESI) to mass spectrometry imaging of industrial materials. The t-SPESI parameters including tapping solvent composition, solvent flow rate, number of tapping at each spot, and step-size were optimized using a quadrupole mass spectrometer to improve mass spectrometry (MS) imaging of thin-layer chromatography (TLC) and additives in polymer films. Spatial resolution of approximately 100 μm was achieved by t-SPESI imaging mass spectrometry using a fused-silica capillary (50 μm i.d., 150 μm o.d.) with the flow rate set at 0.2 μL/min. This allowed us to obtain discriminable MS imaging profiles of three dyes separated by TLC and the additive stripe pattern of a PMMA model film depleted by UV irradiation.

DOI： 10.5702/massspectrometry.S0050

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Authorship：Corresponding author   Language：English  

DOI： 10.5702/massspectrometry.A0028

CiNii Books

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Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jz401447w

Scopus

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Language：Japanese   Publisher：The Adhesion Society of Japan  

DOI： 10.11618/adhesion.49.171

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

File： 29_429.pdf

DOI： 10.2116/analsci.29.429

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Other Link： https://link.springer.com/article/10.2116/analsci.29.429/fulltext.html

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

Abstract

The choice of stabilizer and the stabilizer-to-precursor ions molar ratio during metal nanoparticle synthesis are important for controlling the shape, size, and dispersion stability of the nanoparticles. However, the active sites on the nanoparticles surfaces may be blocked by the stabilizing agents used, resulting in a less-than-effective utilization of the surfaces. In this review, various surfactant-free solution-based methods of synthesizing metal nanoparticles are described, along with the applications of such nanoparticles in catalysis and sensing. “Surfactant-free” synthesis does not imply truly bare metal nanoparticles synthesis but implies one where the metal nanoparticles are prepared in the absence of additional stabilizing agents such as thiolate and phosphine compounds, surfactants, and polymers. These metal nanoparticles are stabilized by the solvents or the simple ions of the reducing agents or low-molecular-weight salts used. Surfactant-free synthesis of metal nanoparticles via photochemical-, ultrasonochemical-, and laser ablation-mediated synthesis methods is also described. Because of the effective utilization of their surfaces, metal nanoparticles prepared without surfactants, polymers, templates, or seeds are expected to exhibit high performance when used in catalysis (synthetic catalysis and electrocatalysis) and sensing (surface-enhanced Raman scattering (SERS)), surface-assisted laser desorption/ionization-mass spectrometry (SALDI-MS)).

File： 10.1515_ntrev-2012-0079.pdf

DOI： 10.1515/ntrev-2012-0079

Scopus

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Other Link： https://www.degruyter.com/downloadpdf/journals/ntrev/2/1/article-p5.xml

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using GaP nanoparticles (NPs) prepared by a gas evaporation method was investigated on poly(ethylene glycol)s (PEGs). The mass spectra of PEG and survival yield measurements suggested that larger GaP NPs have a quite high soft ionization ability.

DOI： 10.1039/c2an36738f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IM PUBLICATIONS  

The electrical conductivity of the matrix crystal might be a new factor to enhance matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sensitivity. In MALDI-MS, several compounds are used as a standard matrix. Utilization of such compounds is based on an a posteriori approach, but there is no theoretical guidance for selecting a matrix. In an attempt to further understand performance in MALDI-MS, we utilized peptide detection for random screening of a chemical library (12,383 compounds) for compounds with matrix functions in MALDI-MS. A lot of thiophene compounds were found to be a matrix, in which 2-[5-(2,4-dichlorobenzoyl)-2-thienyl] acetic acid (DCBTA) provided an important clue to measure the electrical conductivity of the matrix crystal, because the structure of DCBTA is analogous to conductive polymers and organic solar cells. Most of the crystals of standard matrices, such as alpha-cyano-4-hydroxycinnamic acid (CHCA), 3,5-dimethoxy-4-hydroxycinnamic acid [sinapinic acid, (SA)], and DCBTA showed electrical conductivity, whereas the conductivity of crystal was not observed in 2,5-dihydroxybenzoic acid (2,5-DHB). On the other hand, super-DHB using 2-hydroxy-5-methoxybenzoic acid [5-methoxysalicylic acid, (MSA)] as an additive to 2,5-DHB, improved the electrical conductivity of the crystal, that followed the enhancement of peak intensity in MS spectrum. These observations might indicate that the electrical conductivity of matrix crystals is a key consideration in obtaining efficient MALDI performance.

DOI： 10.1255/ejms.1215

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A complementary analytical methodology combining localised surface plasmon resonance (LSPR) sensing and matrix assisted laser desorption/ionisation-mass spectrometry (MALDI-MS) has been developed by using triangular silver nanoplates (Ag NPLs). Ag NPLs with near-IR LSPR absorbance were prepared via a two-step photo-mediated growth process from Ag nanoparticles. These could be utilised as a common platform for LSPR/MALDI-MS, as they were suitable for LSPR sensing via the analysis of surface plasmon absorption bands and as the assisting material for LDI-MS. For practical use, the detection of analytes by LSPR sensing can be achieved by using specific biomolecular recognition techniques that involve the surface modification of metal NPs with large molecules such as proteins. We investigated the effect on LSPR sensitivity (i.e. refractive index unit, RIU) of modifying the Ag surface with molecules of different sizes, and found that the RIU values were proportional to the amplitude of the cube root of the molecular weight, M-w(1/3). We demonstrated the utility of this complementary LSPR and MALDI-MS analysis methodology by evaluating the binding of a soybean trypsin inhibitor to the Ag NPL substrate covalently modified with trypsin. This specific biomolecule recognition phenomenon was first detected using the LSPR technique, and then successfully identified by MALDI-MS.

DOI： 10.1039/c3ay40708j

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jp308380z

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s11051-012-1379-2

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Graphene-coated cobalt nanoparticles surface-functionalized with benzylamine groups (CoC-NH2 nanomagnets) were shown to effectively enrich analytes for surface-assisted laser desorption/ionization mass spectrometry (affinity SALDI-MS) analysis. These CoC-NH2 nanomagnets are highly suited for use with affinity SALDI-MS because their mean diameter of 30 nm, high specific surface area of 15 m2 g-1, and high-strength saturation magnetization of 158 emu g-1 led to efficient extraction of analytes by magnetic separation, which in turn enabled excellent SALDI-MS performance. Surface modification of CoC nanomagnets with benzylamine groups increased the yield of peptide ions and decreased fragmentation of benzylpyridinium ions, so-called "thermometer ions" formed through soft ionization. The CoC-NH2 nanomagnets were used to extract perfluorooctanesulfonate from large volumes of aqueous solutions by magnetic separation, which was identified directly by SALDI-MS analysis with high sensitivity even at the sub-part-per-trillion level (∼0.1 ng/L). The applicability of CoC-NH2 nanomagnets in conjunction with SALDI-MS for the enrichment and detection of pentachlorophenol, bisphenol A, and polyfluorinated compounds (PFCs) with varying chain length, which are environmentally significant compounds, as well as small drugs, was also evaluated. © 2012 American Chemical Society.

DOI： 10.1021/ac302004g

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c2ay26013a

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Here, we report on the use of human serum albumin (HSA)-modified Fe3O4 nanoparticles (NPs) (HSA-Fe3O4 NPs) for affinity-SALDI-MS of small drugs in human biological liquids. We demonstrated that HSA-Fe3O4 NPs effectively captured small drugs from human urine and serum via the interactions between HSA and these drugs. The drugs adsorbed on HSA could then be identified by directly introducing the HSA-Fe3O4 NPs into a mass spectrometer for SALDI-MS analysis. The ability of HSA to interact with multiple small drugs facilitated the simultaneous detection of a 4-drug-mixture in serum, viz., phenytoin, ibuprofen, camptothecin, and warfarin sodium, by affinity-SALDI-MS using HSA-Fe3O4 NPs. In contrast, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with an organic matrix could detect only warfarin sodium. We also demonstrated the capacity of affinity-SALDI-MS to quantify warfarin sodium in urine samples across a range of 50 - 1000 mu M (R-2 = 0.998) when using HSA-Fe3O4 NPs. The detection sensitivity was further improved to a range of 5 - 100 mu M (R-2 = 0.999) by using denatured HSA. The open structure of denatured HSA may enhance the effective extraction of small drugs from biological liquids, and increase the detection-sensitivity of affinity-SALDI-MS. Affinity-SALDI-MS using protein-modified Fe3O4 NPs can open up new approaches to the analytical detection of small drugs in biological liquids by SALDI-MS.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

RATIONALE Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) allows for the simultaneous detection and imaging of several molecules in a sample. However, when using an organic matrix in the MALDI-IMS of small molecules, inhomogeneous matrix crystallization may yield poorly reproducible peaks in the mass spectra. We describe a solvent-free approach that employs a homogeneously deposited metal nanoparticle layer (or film) for small-molecule detection. METHODS Platinum vapor deposition surface-assisted laser desorption/ionization imaging mass spectrometry (Pt vapor deposition SALDI-IMS) of small molecules was performed as a solvent-free and organic-matrix-free method. A commercially available magnetron sputtering device was used for Pt deposition. Vapor deposition of Pt produced a homogenous layer of nanoparticles over the surface of the target imaging sample. RESULTS The effectiveness of Pt vapor deposition SALDI-IMS was demonstrated for the direct detection of small analytes of inkjet ink on printed paper as well as for various other analytes (saccharides, pigments, and drugs) separated by thin-layer chromatography (TLC), without the need for extraction or concentration processes. The advantage of choosing Pt instead of Au in SALDI-IMS was also shown. CONCLUSIONS A solvent-free approach involving the direct deposition of Pt on samples (SALDI-IMS) is effective for the analysis of inkjet-printed papers and various analytes separated by TLC. This method would be useful in imaging analyses of various insulating materials such as polymers and biological materials. Copyright (C) 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.6301

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

An atmospheric pressure photoionisation (APPI) source for liquid chromatography/mass spectrometry (LC/MS) was applied to determine neonicotinoid pesticides in the aquatic environment. Dopant-assisted APPI was very effective in the ionisation of neonicotinoids. Neonicotinoids generated protonated molecules in APPI with high sensitivity, while adduct ions, such as sodiated molecules, were predominantly generated in conventional electrospray ionisation. The ionisation of neonicotinoids was confirmed by ultra-high-resolution MS. An analytical method coupled with solid phase extraction was developed for acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, and thiamethoxam. Method detection limits were 0.47 to 2.1 ng L-1 for six neonicotinoids. Dinotefuran was the most frequent and highest among the neonicotinoids examined in the aquatic environment in Osaka, Japan. The maximum concentration of dinotefuran was 220 ng L-1. Given the toxicity of neonicotinoids for aquatic creatures, the concentrations observed here were substantially low. The change in concentrations was temporally coincident with the period of the neonicotinoid application. Although rapid photodegradation and some degradation products have been elucidated, the degradation products in the aquatic environment were not identified in the present study.

DOI： 10.1039/c2em30296a

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Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Books

J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

In order to elucidate the role of desorption/ionization efficiency of peptides in MALDI-MS, we focused on peptides with disulfide bonds, which form a rigid tertiary structure. We synthesized seven sets of peptides with one disulfide bond (oxytocin, somatostatin, [Arg(8)]-vasopressin, [Arg(8)]-vasotocin, cortistatin, melanin-concentrating hormone, urotensin II-related peptide) and five sets of peptides with two disulfide bonds (tertiapin, alpha-conotoxin GI, alpha-conotoxin 1ml, a-conotoxin MI and alpha-conotoxin SI). Each peptide set consisted of three peptides: the oxidized form (S-S type), the reduced form (SH type), and an internal standard peptide in which all cysteine residues were substituted with alanine residues. In the case of urotensin II-related peptide, tertiapin, alpha-conotoxin ImI and alpha-conotoxin MI, the reduced form showed higher desorption/ionization efficiency than the oxidized form. In contrast, the other peptides revealed higher desorption/ionization efficiency in the oxidized form relative to the reduced form. These results imply that a rigid structure of peptides formed by disulfide bonds does not correlate with desorption/ionization efficiency in MALDI-MS.

DOI： 10.2116/analsci.28.295

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Mass Spectrometry Society of Japan  

File： 1_A0012.pdf

DOI： 10.5702/massspectrometry.a0012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Surfactant-free, single-nano-sized copper nanoparticles (Cu NPs) (size: about 2 nm) were prepared by the DMF reduction method. The Cu NPs showed high catalytic activity (with a turnover number (TON) of up to 2.2 X 10(4)) in Ullmann-type cross-coupling of aryl halides with phenols under ligand-free conditions.

DOI： 10.1039/c2cc30975k

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In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH4, a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (similar to 10(-7) g). The pseudo-first-order rate constant (k(app)) and activation energy were estimated to be 3 x 10(-3) s(-1) and 31 kJ mol(-1), respectively, with 1.0 mu M of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t(0)) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au-25(SG)(18)NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (k(app) = 8 x 10(-3) s(-1)) even with a low catalyst concentration (1.0 mu M), and there was no induction time (t(0)) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au-25(SG)(18)NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.

DOI： 10.1039/c2nr30222e

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This report demonstrates the first pH-dependent synthesis of pepsin-mediated gold nanoclusters (AuNCs) with blue-, green-, and red-fluorescent emission from Au-5 (Au-8), Au-13, and Au-25, respectively. Pepsin is a gastric aspartic proteinase (molecular weight, 34 550 g/mol) that plays an integral role in the digestive process of vertebrates. It was found that the pH of the reaction solution was critical in determining the size of Au NCs (i.e., the number of gold atoms of AuNCs). Interestingly, enzyme function of pepsin contributes to the formation of these AuNCs. The photo-stability of the Au-25 (or Au-13) NCs is much higher than that of Au-5 NCs (i.e., Au-25 similar to Au-13 &gt; &gt; Au-5). The pepsin-mediated Au-25 NCs were also found to be useful as fluorescent sensors for the detection of Pb2+ ions by enhanced fluorescence and the detection of Hg2+ ions by fluorescence quenching. Although the detailed formation mechanisms of these AuNCs require further analysis, the synthetic route using proteinase demonstrated here is promising for preparing new types of fluorescent metal nanoclusters for application in catalysis, optics, biological labeling, and sensing.

DOI： 10.1002/adfm.201100886

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

File： 27_591.pdf

DOI： 10.2116/analsci.27.591

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Other Link： https://link.springer.com/article/10.2116/analsci.27.591/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The polymerization of vinyl chloride (VC) with n- or tert-butyllithium (n- or tert-BuLi) in the presence of allyl bromide (ABr) was evaluated for synthesizing the vinyl-terminated poly(vinyl chloride) macromonomer (PVCM). The structure of the product was based on the (1)H NMR and H-H COSY spectra. The functionality of the vinyl group was over 90%. To determine the detailed structure of PVCM, a MALDI-TOF-MS analysis of the PVCM derivative (PVC-DEA center dot HCl) obtained by the thiol-ene reaction of the macromonomer with 2-(diethylamino)ethanethiol hydrochloride was conducted. The MALDI mass spectrum of PVC-DEA center dot HCI in the absence of any ionizers exhibited only one series of ions repeating at an interval of 62 Da (which was the repeating VC unit), and the mass distribution agreed well with the calculated value of PVC-DEA center dot H(+) without any defect structures. The syndiotactic rich PVC was found to be synthesized by the polymerization of VC with BuLi in the presence of ABr. Especially, the obtained PVCM using tert-BuLi (ABr/BuLi = 10) was the most syndiotactic polymer (rr &gt; 80%).

DOI： 10.1021/ma200042e

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Ultrasonic degradations of polyethylene oxide (PEO), polymethyl methacrylate (PMMA) and polyethylene oxide-block-propylene oxide (PPO) copolymers in aqueous media were studied using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and liquid-chromatography atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). The ultrasonic degradation of the polymers with a horn-type 28 kHz oscillator was monitored as a function of the ultrasonication duration to examine the structural details of ultrasonic degradation polymers. The ultrasonication of a PEO solution produced five types of oligomers (Mn = ca. 1000 Da) with different end groups, irrespective of the initial average molecular masses (Mn) 2, 6, 20, and 2000 kDa. Several degradation pathways with free radical reactions were suggested to explain these degradation products. On the other hand, ultrasonication of PMMA (Mn 1630 Da) and uniform PMMA (n = 29) generated only one type of degradation oligomer. In addition to chemical reactions with OH center dot and H center dot radicals, the results indicated that primary degradation takes place near at the center of the polymer chains by mechanical forces generated around collapsing cavitation bubbles. Ultrasonic degradation of PEO-block-PPO copolymers consisting of a hydrophilic and a hydrophobic portion was studied to determine the location of bonds involved in the initial scission of the copolymers. A detailed structural analysis of the degradation products indicated that the initial bond scissions occurred principally at the boundary regions between the backbones of PEO and PPO chains. Further structural analysis revealed the presence of oxygen adducts in the degradation products. By a comparison with a thermal degradation carried out in a helium atmosphere, one can conclude that the oxygen adducts are formed by radical reactions with water or dissolving oxygen molecules. The study demonstrated that chemical reactions as well as physical bond stress scissions are involved in the ultrasonic degradation of the copolymers.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Femto-second laser photodegradations of polyethylene oxide (PEG), poly (ethylene oxide-b-propylene oxide) copolymer and polydimethylsiloxane (PDMS) were studied to investigate the degradation mechanism. MALDI-TOFMS and LGAPCI-MS were used for detail structural analysis of the degradation products. The results indicated that laser photodegradation proceeds within a few minutes in both aqueous and organic solutions. The degradation products of laser irradiation were identical to those of ultrasonic irradiation, but were not to those of thermal degradation in an aqueous solution using high-resolution mass spectrometry. Therefore, it is suggested that the mechanism of laser photodegradation of the polymers is due to the physical bond scissions through cavitation, just like ultrasonic degradation and the chemical reactions of the polymer chains with radicals formed from solvent or dissolved oxygen in laser-ablation.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

A simple and rapid method to provide a 2-dimensional liquid chromatogram (LCxLC) was developed for the characterization of synthetic polymers using liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS). Two sets of LC-MS chromatogram data using two different LC columns were prepared in property. The elution time of each chromatogram was plotted based on ions with the same m/z values, to give a scattering diagram of pseudo 2D-chromatogram. The application of this method was discussed to separate and identify a mixture of ten different polyethers.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Nowadays, chitin and chitosan are applied in many medical and pharmaceutical products. However little is known about the metabolism of chitin and chitosan in vivo. In the human body, lysozyme will degrade chitin and chitosan into chito-oligosaccharides. C-13 labeled chitosan is an essential prerequisite for the further study of the fate of chito-oligosaccharides in vivo. To fulfill this requirement, chitosans were extracted from mycelia of fungi. Absidia coerulea ATCC 14076 and Gongronella butleri USDB 0201 and ATCC 42618 grown in solid substrate fermentation (SSF) and submerged fermentation (SMF) to select the best fungus and fermentation method for the production of C-13 labeled chitosan. Based on the production yield of chitosan, the SSF method is the best method for the production of fungal chitosan when compared with SMF methods (i.e., fed-batch fermentation and batch fermentation). However synthesis of C-13 labeled chitosan in cell wall of G. butleri grown in SSF medium coated with 1-C-13-glucose was not observed. Alternatively, fungus A. coerulea was grown in SMF medium containing 2-C-13-glucose. The successful synthesis of C-13 labeled glucosamine from 2-C-13-glucose was observed in mycelia of A. coerulea grown in SMF medium containing 2-C-13-glucose in a yield of about 13 g/100 g mycelia. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbpol.2010.06.023

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DOI： 10.1016/j.apsusc.2010.08.128

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A self-assembled film of gold nanoparticles (AuNPs) with a raspberry-like morphology was prepared on a glass plate by the layer-by-layer thermal annealing of multilayer films of AuNPs. It was possible to control the morphology of the obtained films of AuNPs by changing the annealing temperature, duration of annealing, and number of layers. On investigating the plasmonic properties of these films, we found that AuNP films with a raspberry-like morphology yielded the highest refractive index unit, which is a critical parameter in localized surface plasmon resonance (LSPR) sensing, as compared to other types of AuNP films. Self-assembled AuNP films with a raspberry-like morphology were subsequently functionalized with 11-mercaptoundecanoic acid (MUA) to enable the binding of lysozyme to the MUA-modified Au surface. The superior limit of detection for the LSPR sensing of lysozyme in a buffer solution was found to be in the picomolar range (similar to 10(-12) M). The high sensitivity observed in the region was attributed to the raspberry-like morphology, where the AuNPs were packed closely together, and the electromagnetic field confinement was most intense (i.e., at hot spots). The MUA-modified, self-assembled AuNP films with a raspberry-like morphology were finally used in the combination analysis of LSPR sensing and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the selective detection and identification of lysozyme in human serum.

DOI： 10.1039/c0an00826e

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1143/APEX.4.095001

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We report the synthesis of 2 nm copper nanocrystals (Cu NCs) via a microwave-assisted polyol method without using additional protective and reducing agents. The Cu NCs are oxidation resistant and exhibit photoluminescence and highly stable properties in a colloidal dispersion.

DOI： 10.1039/c1cc12346g

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Surfactant-free Pd nanoclusters (Pd NCs) (size: 1-1.5 nm) showed high catalytic activity in the Suzuki-Miyaura cross-coupling and Mizoroki-Heck reactions. The Pd NCs had a high turnover number, up to 6.0 x 10(8), which can be recycled at least five times without loss of catalytic activity.

DOI： 10.1039/c1cc11487e

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Language：English   Publisher：The Biophysical Society of Japan  

Electrospray ionization mass spectrometry (ESI-MS), circular dichroism (CD), nuclear magnetic resonance (NMR) spectroscopy, flow dialysis, and bioactivity measurements were employed to investigate the roles of the C-terminal residues of calmodulin (CaM). In the present study, we prepared a series of truncated mutants of chicken CaM that lack four (CCMΔ4) to eight (CCMΔ8) residues at the C-terminal end. It was found that CCMΔ4, lacking the last four residues (M145 to K148), binds four Ca²⁺ ions. Further deletion gradually decreased the ability to bind the fourth Ca²⁺ ion, and CCMΔ8 completely lost the ability. Interestingly, both lobes of Ca²⁺-sturated CCMΔ5 showed instability in the conformation, although limited part in the C-lobe of Ca²⁺-saturated CCMΔ4 was instable. Moreover, unlike CCMΔ4, structure of the C-lobe in CCMΔ5 bound to the target displayed dissimilarity to that of CaM, suggesting that deletion of M144 changes the binding manner. Deletion of the last five residues (M144 to K148) and further truncation of the C-terminal region decreased apparent capacity for target activation. Little contribution of the last four residues including M145 was observed for structural stability, Ca²⁺-binding, and target activation. Although both M144 and M145 have been recognized as key residues for the function, the present data suggest that M144 is a more important residue to attain Ca²⁺ induced conformational change and to form a proper Ca²⁺-saturated conformation.<br>

DOI： 10.2142/biophysics.7.35

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DOI： 10.1117/12.893716

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DOI： 10.2116/bunsekikagaku.60.245

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Language：English   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using nanoparticles (NPs) and nanostructured surfaces as the LDI-assisting nanomaterials is a soft ionization technique that features minimal fragmentation of analytes. As compared to traditional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) using organic matrices, SALDI-MS affords several advantages, such as the ability to detect small molecules (&lt;500 Da), easy sample preparation, low-noise background, high salt tolerance, and fast data collection without the use of an organic matrix. The performance of SALDI has been further improved recently in terms of the detection sensitivity, detection mass range from the low- to the high-mass region, a soft LDI process, the detection of both polar and nonpolar compounds, the selective detection of analytes from a complex mixture using functionalized NPs, and various applications, including imaging mass spectrometry. This review summarizes recent developments pertaining to various NPs and nanostructured surfaces for SALDI-MS.

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

In the present study, we carried out the photochemical synthesis of glycine-stabilized gold nanoparticles (Au NPs) at room temperature by using a photochemical initiator (Irgacure-2959). By adjusting the pH of the aqueous solution to 9 at the synthesis, we obtained a stable dispersion of anionic-glycine-stabilized Au NPs with sizes of about 5 nm; on the other hand, we obtained large and unstable neutral-glycine-capped Au NPs and cationic-glycine-capped Au NPs at pH 6 and 3, respectively. Anionic glycine has the highest affinity to Au NPs since the unprotonated amine and carboxylic groups of glycine interact with the gold surface. Heavy-metal-induced aggregation behavior of the glycine-stabilized Au NPs was also examined through the colorimetric detection of heavy metals (Ca2+, Cd2+, Co2+, Hg2+, Mg2+, Ni2+, Pb2+, and Zn2+). These sensitivities were nearly consistent with the complex formation constants (beta(1)) of glycine with these metal ions, but there was no difference between the detection limits of Hg2+ and Pb2+, irrespective of much higher beta(1) value of Hg2+ than that of Pb2+. It was suggested that this difference could be attributed to the difference in the binding behaviors of Hg2+ and Pb2+ with the glycine-capped Au NPs. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2010.07.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SCIENTIFIC PUBLISHERS  

Platinum/carbon (Pt/C) composite materials were prepared by the hydrazine reduction of H(2)PtCl(6) confined to a mixed surfactant lytropic liquid crystal (LC)/C mixture with varying amounts of water. The reaction at relatively low water contents successfully yielded cross-linked Pt nanowires with wire-widths of 2-5 nm. The novel Pt nanostructure is believed to be from poorly hydrated hexagonal domains formed together with layered domains by the phase separation of the precursory LC mixture in the presence of carbon. Electrochemical measurements using cyclic volutammetry and membrane electrode assemblies revealed that the cross-linked nanowired Pt/C composite exhibits fairly high electrocatalytic activity for oxygen reduction reaction, as well as a high performance as the cathode material for polymer electrolyte fuel cells.

DOI： 10.1166/jnn.2010.2439

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

We have designed a semi-online liquid chromatography/matrix-assisted laser desorption/ionization mass spectrometry (LC/MALDI-MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI-MS analysis. Our novel semi-online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,-hexa-fluoroisopropyl alcohol (HFIP), to be used to achieve cost-effective analysis. Using the semi-online LC/MALDI-MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size-exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed-phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI-MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size-exclusion separation; the reversed-phase separation by interaction with the ODS functions may have less influence on column separation. The semi-online monolithic capillary LC/MALDI-MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4584

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Ultrasonic degradation of poly(ethylene oxide-block-propylene oxide) copolymers consisting of a hydrophilic and a hydrophobic portion was studied with the aim to determine the location of bonds involved in the initial scission of the copolymers. LC-APCI-IT-MS and LC-APCI-orbitrap-MS were used for the detailed structural analysis of degradation products. The results indicated that initial bond scissions occurred principally at the boundary regions between backbones of polyethylene oxide (PEO) and polypropylene oxide (PPO) chains. Further structural analysis revealed the presence of oxygen adducts in the degradation products. Comparison with a thermal degradation carried out in helium atmosphere, one can conclude that the oxygen adducts are formed by radical reaction with water or dissolving oxygen molecules. The study demonstrated that chemical reactions as well as physical bond stress scissions are involved in the ultrasonic degradation of the copolymers. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/jms.1771

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

The effects of an on-line ion suppressor device on alkali metal ion adduct formations of the model compound tacrolimus were investigated. The base peak ion in the positive ion ESI-MS spectrum of tacrolimus was a sodium ion adduct, [M+Na](+). On the other hand, an ammonium ion adduct, [M+NH(4)](+), was the base peak ion in the full-scan mass spectrum of tacrolimus with a cation-exchange suppressor resin, and both [M+Na](+) and [M+K](+) were eliminated. These results indicate that the combination of an on-line ion suppressor with ESI-MS is a simple and effective technique that eliminates undesirable alkali metal ion adduct formations in the positive-ion mode.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The heterochirality of a 1:2 metal/Ph-pybox complex ion was encyclopedically evaluated by ESIMS using pseudo-racemic (R,R)- and (S,S)-Ph-pybox pair, which were unlabeled/labeled by deuterium atoms, respectively. The heterochiral complex was predominantly formed in all investigated 1:2 metal/Ph-pybox complex ions.

DOI： 10.1246/cl.2010.564

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

One of the problems associated with surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using metal nanoparticles is that peptide analytes are characterized by alkali metal ion adducts even though in the presence of an excess proton source of trifluoroacetic acid in the mass spectra, and their alkali metal ion adducts are often observed in the low peak intensity. In this study, to improve the detection of the proton adduct form of the peptides, the effectiveness of platinum (Pt) particle deposition on a silicon plate for SALDI-MS was examined using the following different Pt-deposited silicon substrates: (1) Pt galvanic deposition (PGDS), (2) Pt particles deposited by suspension deposition on silicon, (3) evaporated Pt on oxidized silicon, and (4) evaporated Pt on bare silicon. Among these substrates, the PGDS plate exhibited the dominant proton adduct form of peptides in the SALDI mass spectra. In addition to platinum deposition, we attempted to employ palladium galvanic deposition as a SALDI-MS substrate, but it was found to lead mainly to the Na(+) and K(+) forms of the molecular ion. We propose that UV laser radiation-mediated surface-localized positive charges generated by effective charge separation (electron and hole) in the PGDS are important for the production of the proton adduct forms of peptides. Gly-Gly-Tyr-Arg, caffeine, raffinose, and beta-cyclodextrin were used as examples to demonstrate the feasibility of PGDS as a matrix-free method for LDI-MS. It was possible to detect these small molecules with SALDI-MS using PGDS; however, the detection sensitivity of these small molecules remains an unresolved issue. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ijms.2010.02.001

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The degradation effects of benzoylferrocene (BF) on poly(ethylene glycol) (PEG) and poly(methyl methacrylate) (PMMA) were investigated using MALDI-MS. It is supposed that the release of free radicals in solution by BF plays a key role in the decomposition of PEG and PMMA. MALDI-MS combined with examination of the degradation by BF could be applied to the analysis of synthetic polymer structures containing the PEG and PMMA chain.

DOI： 10.1246/cl.2010.66

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DOI： 10.1246/cl.2010.370

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DOI： 10.1021/la9038842

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

We report a new and facile method for synthesizing 3D platinum nanoflowers (Pt Nfs) on a scratched silicon substrate by electroless galvanic displacement and discuss the applications of the Pt Nfs in surface-assisted laser desorption/ionization-mass spectrometry (SALDI-MS). Surface scratching of n-type silicon is essential to induce Pt Nf growth on a silicon substrate (to obtain a Pt Nf silicon hybrid plate) by the galvanic displacement reaction. The Pt Nf silicon hybrid plate showed excellent SALDI activity in terms of the efficient generation of protonated molecular ions in the absence of a citrate buffer. We propose that the acidity of the Si-OH moieties on silicon increases because of the electron-withdrawing nature of the Pt Nfs; hence, proton transfer from the Si OH groups to the analyte molecules is enhanced, and finally, thermal desorption of the analyte ions from the surface occurs. Signal enhancement was observed for protonated molecular ions produced from a titania nanotube array (TNA) substrate on which Pt nanoparticles had been photochemically deposited. Moreover, surface modification of the Pt Nf silicon hybrid plate by perfluorodecyltrichlorosilane (FDTS) (to obtain an FDTS-Pt Nf silicon hybrid plate) was found to facilitate soft SALDI of labile compounds. More interestingly, the FDTS-Pt Nf silicon hybrid plate acts 1) as a high-affinity substrate for phosphopeptides and 2) as a SALDI substrate. The feasibility of using the FDTS-Pt Nf silicon hybrid plate for SALDI-MS has been demonstrated by using a beta-casein digest and various analytes, including small molecules, peptides, phosphopeptides, phospholipids, carbohydrates, and synthetic polymers. The hybridization of Pt Nfs with a scratched silicon substrate has been found to be important for achieving excellent SALDI activity.

DOI： 10.1002/chem.201001038

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DOI： 10.1039/b925117k

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DOI： 10.11203/jar.25.344

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DOI： 10.1002/rcm.4305

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

The simultaneous LC/MS analyses of hexachlorobenzene (HCB) and pentachlorophenol (PCP), two dioxin precursors were studied by both atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization mass spectrometry (APPI/MS). The optimum LC/MS conditions of the simultaneous analysis were determined for these two compounds with different polarity. Ionization by APPI was found to be more effective than by APCI, and is thus a better ionization method for analysis of the two compounds. Using LC/APPI/MS we can achieve the simultaneous analysis of HCB and PCP at ppb levels.

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

Bare FePtCu nanoparticles (NPs) are first prepared for laser desorption/ionization mass spectroscopy (LDI-MS) analysis as affinity probes to selectively trap oppositely charged analytes from a sample solution. Our present results demonstrate bare FePtCu NPs to be a potentially useful matrix for surface-assisted laser desorption/ionization mass spectroscopy (SALDI-MS), for the analysis of small proteins and peptides. The upper detectable mass range of peptides was approximately 5 kDa, and the detection limit for peptides approximately 5 fmol. Sulfonate group-modified FePtCu nanoparticles (FePtCu-SO(3)(-) NPs), with ionization being independent of the solution pH, can interact with a positively charged analyte, and the analyte-bound NPs can be separated from the reaction supernatant by centrifugation or an external magnetic field. An oligopeptide, Gly-Gly-Tyr-Arg (GGYR) from an oligopeptide mixture containing Asp-Asp-Asp-Asp (DDDD), Gly-Gly-Gly-Gly (GGGG) and GGYR, was detected using SALDI-MS with FePtCu-SO(3)(-) NPs employing electrostatic interaction. Furthermore, FePtCuSO(3)(-) NPs can detect lysozyme (Lyz) in human serum through the electrostatic attraction between positively charged Lyz and FePtCu-SO(3)(-) NPs at pH 8, while detection of negatively charged albumin in human serum is not possible.

DOI： 10.1007/s00216-009-3122-0

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

The pyrolytic highly oriented graphite polymer film (PGS) was first employed to analyze low-mass analytes in environmental analysis by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). PGS is a synthetic uniform and highly oriented graphite polymer film with high thermal anisotropic conductivity. We have found that negative ion mode SALDI-MS using oxidized PGS (PGS-SALDI-MS) can be used to detect [M-H](-) ions from perfluorooctanoic acid (PFOA) and other perfluoroalkylcarboxylic acids when the PGS surface is modified with the cationic polymer polyethyleneimine (PEI). The signal intensity of PFOA when employing the PEI modification showed a ten-fold increase over that obtained from desorption/ionization on porous silicon (DIOS). PFOA was quantified using PGS-SALDI-MS and the calibration curve showed a wide linear dynamic range of response (20-1000 ppb). The combination of atmospheric pressure ionization and PGS (AP-PGS-SALDI) showed greater signal intensity than vacuum PGS-SALDI for deprotonated PFOA. Several other environmentally important chemicals, including perfluoroalkylsulfonic acid, pentachlorophenol, bisphenol A, 4-hydroxy-2-chlorobiphenyl, and benzo[a]pyrene, were also successfully used to evaluate PGS-SALDI-MS. In addition, we found that nonafluoro-l-butanesulfonic acid was able to produce protonated peptides in positive ion PGS-SALDI-MS, but that perfluoropentanoic acid and trifluoroacetic acid were not. It is suggested that perfluoroalkylsulfonic acids are better protonating agents than perfluoroalkylcarboxylic acids in SALDI-MS. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4254

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

We have investigated the effect of urea surface modification and the photocatalytic cleaning on surface-assisted laser desorption ionization mass spectrometry (SALDI-MS) with amorphous TiO2 nanoparticles for the reduction of the background noise and the improvement of the sensitivity. In the use of nanoparticles of high surface area, chemical background signals arising from ambient environments and organic contaminants can frequently be serious problems below 500 Da, possibly reducing the advantages of the matrix-free approach. In this study, removal of contaminants and enhanced SALDI efficiency were easily achieved with UV irradiation via the photocatalyst effect of TiO2 before SALDI-MS measurements. The surface cleaning achieved by the UV photocatalytic procedure reduced the background noise and increased the peak intensities of peptides. in addition, we found that urea surface modification of TiO2 nanoparticles increased the performance of the TiO2-SALDI-MS. (1) The urea-surface modification of TiO2 made it possible to produce proton-adduct forms without citrate buffer, resulting in low background noises below 500 Da, in contrast to the essential use of a citrate buffer in the bare TiO2-SALDI-MS. (2) The detection sensitivity of angiotensin I increased to 0.3 fmol with the urea-surface modification, as compared to the use of bare TiO2 nanoparticles (6 fmol). The urea-TiO2 could ionize proteins of more than 20 000 Da such as trypsinogen (600 fmol). (3) The urea modification of TiO2 had the advantage of selective detection of phosphopeptides without sample clean up, or prefractionation in tryptic digest products of bovine hemoglobin. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/jms.1628

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Desorption/ionization on porous silicon mass spectrometry (DIOS-MS) was introduced as a matrix-free LDI-TOF-MS, which succeeded at almost eliminating the background ion interference and offered a new technology for high-speed analysis of low mass compounds. In this study, we first demonstrated that the DIOS-MS is very useful for environmental analysis of perfluorooctane sulfonate (PFOS). In particular, DIOS can detect PFOS with the high sensitivity and the detection limit was 1 ppt without the extraction operation. At the very low concentration of 1 ppt, the PFOS was not detectable with the use of the traditional MS methods such as MALDI-MS and ESI-MS. The quantitative analysis of PFOS in the tap water was also performed from the calibration curve in the low concentration range from 2.5 to 10 ppb. In contrast, it was found that DIOS-MS has a low sensitivity for PFOA. This suggests that the DIOS plate has a high sensitivity for perfluorochemicals of sulfonic acid than that of carboxylic acid as the ionized group. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2009.04.035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Zinc pyrithione (ZnPT) is widely used as an antidandruff or antifouling reagent. However, this compound is considered toxic, such as the teratogenic effect, to aquatic lives, and it is important to clarify the mechanism of its toxicity. In this study, the interactions between ZnPT and amino acids were observed using electrospray ionization mass spectrometry (ESI-MS) in order to obtain information on the activity of ZnPT within the living body. The ZnPT complex ([ZnPT-ligand+Amino acid](+)), in which the ligand of ZnPT was exchanged by the amino acid, was detected in ZnPT solutions mixed with one of 20 amino acids by ESI-MS. Histidine and cysteine, in particular, showed a high reactivity with ZnPT, while serine and glycine showed a low reactivity. The complexes of ZnPT and a peptide were also observed by the ESI-MS measurement of the solution containing ZnPT with the peptide. These results would be useful to understand the mechanism of ZnPT toxicities to living creatures. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4128

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Language：English   Publisher：JOHN WILEY & SONS LTD  

One of the major problems in proteome analysis is that &lt;50-80% of the peptide fragments generated by the digestion of proteins can be detected by mass spectrometry (MS).([1]) In consequence, inaccuracy of protein identification and lower sensitivity to the detection of post-translational modification occurs in proteome analysis. In addition to suppression effects in peptide mixtures, ([2]) several intrinsic properties of peptides, such as size,([3]) hydrophobicity,([3]) the presence of charged side chain, ([1,4]) aromatic amino acids([1,5]) and secondary structure,([6]) have been reported to influence the ionization efficiency of peptides in laser desorption/ionization MS.

DOI： 10.1002/jms.1574

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

A highly sensitive and simple method for the analysis of chlorothalonil was presented using a liquid chromatograph/mass spectrometer equipped with an atmospheric pressure photoionization (APPI) Source. Chlorothalonil is one of the most extensively used fungicides. The major degraded product of chlorothalonil, 4-hydroxy-2,5,6-trichloroisonaphthonitrile (4OH-TPN), was also quantified with sensitivity similar to that of chlorothalonil. The method was applied to the determination of chlorothalonil in aqueous environment and food samples. The method detection limits (MDLs) of chlorothalonil for aqueous samples and cucumber were determined to be 0.18 and 3.2 ng g(-1). respectively. At several estuarial locations, chlorothalonil was detected with a maximum of 1.1 ng L(-1). Oil the other hand, 4OH-TPN was detected not from estuaries but from rivers with a maximum of 14 ng L(-1).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

In this paper, we describe systematic detailed considerations of the feasibility of using various metal nanoparticles for organic-matrix-free surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). In order to avoid the influence of organic molecules on the nanoparticles, stabilizer-free bare nanoparticles of Ag, Au, Cu and Pt were prepared by laser ablation. Although all metal nanoparticles absorbed N-2 laser light (337 nm) energy, the performance of desorption/ionization of a representative peptide, angiotensin 1, strongly depended on the metal element. Citrate buffer was used as a proton source; it reduced the amount of alkali cation adducts present. Then, protonated molecules of analytes predominated in the mass spectra when Au and Pt nanoparticles were used. Pt nanoparticles showed the highest performance in SALDI-MS, owing to their smaller heat conductivity and higher melting temperature. The selective desorption of a cationic surfactant with longer alkyl chains and a peptide with methionine was also observed.

DOI： 10.2116/analsci.25.339

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Various contaminants alight be frequently detected in high-performance liquid chromatography/mass spectrometry (LC/MS) experiments. This makes highly accurate qualitative and quantitative analyses of LC/MS difficult. It is necessary to know the identification and origin of the contaminants to prevent them from being mixed. In the present work, we paid attention to any contaminants eluted from vials, septa and syringe filters used for an automatic sampling device and filtration preparation in LC/MS experiments. Some contaminants were identified by LC/MS and MS/MS analysis. In addition, we could specify the contaminant source.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Nanohole-structured single-crystalline Pt nanosheets have been synthesized by the borohydride reduction of Na(2)PtCl(6) confined to the lyotropic liquid crystals (LLCs) of polyoxyethylene (20) sorbitan monooleate (Tween 80) with or without nonaethylene-glycol (C(12)EO(9)). The Pt nanosheets of around 410 nm in central thickness and up to 500 nm or above in diameter have a number of hexagonal-shaped nanoholes similar to 1.8 nm wide. High-resolution electron microscope images of the nanosheets showed atomic fringes with a spacing of 0.22 nm indicating that the nanosheets are crystallographically continuous through the nanoholed and non-holed areas. The inner-angle distributions for the hexagonal nanoholes indicate that the six sides of the nanoholes are walled with each two Pt (111), Pt (1(1) over bar 1) and Pt (010) planes. The formation mechanism of nanoholed Pt nanosheets is discussed on the basis of structural and compositional data for the resulting solids and their precursory LLCs, with the aid of similar nanohole growth observed for a Tween 80 free but oleic acid-incorporated system. It is also demonstrated that the nanoholed Pt nanostructures loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction and a high performance as a cathode material for polymer-electrolyte fuel cells, along with their extremely high thermostability revealed through the effect of electron-irradiation.

DOI： 10.1002/adfm.200800966

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SCIENTIFIC PUBLISHERS  

We developed surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using nanocomposite films of cationic diblock copolymer micelles [poly(styrene-b-N-methyl-4-vinyl pyridinium iodide)] and ammonium citrated Au nanoparticles (AuNPs) on silicon. The nanocomposite film on silicon was suitable for use as a material for matrix-free LDI-MS of peptides due to its low matrix background from Au clusters and high ionization efficiency; this plate successfully ionized angiotensin I, and also insulin in the proton adduct forms, in contrast to methods using only AuNPs and those using nanocomposite films of cationic polymer in conjunction with Au NPs. The high ionization efficiency is discussed from the viewpoint of nanoparticle distribution controlled by polymers on the plate (aggregates vs. nonaggregates).

DOI： 10.1166/jnn.2009.J046

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC POLYMER SCIENCE JAPAN  

Allyl monomers polymerize only with difficulty and yield polymers of medium-molecular-weight or oligomers. This is attributable to "degradative monomer chain transfer." However, the well-known allyl polymerization mechanism is based on only the kinetic data but any structural identification is not given. Allyl acetate (AAc), a most typical allyl monomer, was polymerized radically and the resultant oligomeric poly(AAc)s were characterized using MALDI-TOF-MS spectrometry in order to reassess the AAc polymerization mechanism proposed by Litt and Eirich. The induced decomposition of benzoyl peroxide by both growing polymer radical and monomeric allyl radical was presumed but it was never of importance. Then, the fate of resonance-stabilized monomeric allyl radical generated via monomer chain transfer of growing polymer radical was pursued in terms of the competition between the initiation of a new polymer chain and the chain stopping reaction of a growing polymer radical providing monomeric allyl groups as the initial and terminal end-groups, respectively. The monomer chain transfer constant was estimated to be 3.73 x 10(-2) from the P(n) value of poly(AAc) obtained at a low initiator concentration where the coupling termination of growing polymer radical with monomeric allyl radical was negligible.

DOI： 10.1295/polymj.PJ2008174

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DOI： 10.1039/b821402f

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DOI： 10.2116/analsci.25.1197

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Halohydrination of epoxy resins using sodium halides as cationizing agents in matrix-assisted laser desorption/ionization (MALDI) and desorption ionization on porous silicon mass spectrometry (DIOS-MS) were investigated. Different mass spectra were observed when NaClO(4) and NaI were used as the cationizing agents at the highest concentration of 10.0 mM, which is much higher than that normally used in MALDI-MS. MALDI mass spectra of epoxy resins using NaI revealed iodohydrination to occur as epoxy functions of the polymers. The halohydrination also occurred using NaBr, but not NaCl, due to the differences in their nucleophilicities. On the basis of the results of experiments using deuterated CD(3)OD as the solvent, the hydrogen atom source was probably ambient water or residual solvent, rather than being derived from matrices. Halohydrination also occurred with DIOS-MS in which no organic matrix was used; in addition, reduction of epoxy functions was observed with DIOS. NaI is a useful cationizing agent for changing the chemical form of epoxy resins due to iodohydrination and, thus, for identifying the presence of epoxy functions. Copyright (C) 2008 John Wiley & Sons, Ltd.

DOI： 10.1002/jms.1454

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Layer-by-layer (LBL) self-assembled multilayer films of gold nanoparticles (AuNPs) on a silicon wafer were demonstrated to be promising substrates for surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) of peptides and environmental pollutants for the first time. LBL multilayer films, (AuNPs/PAHC)(n), consisting of alternating layers of ammonium citrate capped AuNPs and poly(allylamine hydrochloride) (PAHC) were prepared on a silicon surface. Silicon plates with aggregated AuNPs were more suitable than those with dispersed AuNPs for the SALDI-MS of peptides. The number of particle layers had a significant effect on the laser desorption/ionization of angiotensin I; the peak intensity of the peptide (molecular ion amount) increased with an increase in the number of layers of AuNPs. As a result, the (AuNPs/PAHC)(5) multilayer films increased the sensitivity of the angiotensin I to subfemtomoles and raised the useful analyte mass range, thus making it possible to detect small proteins (a 12 kDa cytochrome c). The signal enhancement when using (AuNPs/PAHC)(5) may be due to (i) the high absorption of the UV laser fight at 337 nm by the AuNP layers, (ii) the low thermal conductivity due to the AuNPs being covered with a thin monolayer of PAHC, and (iii) the increase in the surface roughness (similar to 100 nm) with the number of AuNP layers. Thus, laser-induced rapid high heating of AuNPs for effective desorption/ionization of peptides is possible. In addition, it was found that (AuNPs/PAHC)(5) could be used to extract environmental pollutants (pyrene and dimethyldistearylammonium chloride) from very dilute aqueous solutions with concentrations less than 10(-10) mg/mL, and the analytes trapped in the LBL film could be identified by introducing the film directly into the SALDI mass spectrometer without needing to elute the analytes out of the film.

DOI： 10.1021/ac800789t

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Butyl vinyl ether (BVE) was polymerized radically, and the resultant oligomeric poly(BVE)s were characterized mainly using MALDI-TOF-MS spectrometry. For a further structural identification, the poly(BVE) obtained in bulk was subsequently subjected to H-1 NMR measurement. Notably, an intensive peak assignable to -CH2C(=O)CH2- protons was observed unexpectedly although a peak assignable to -CHO proton as the terminal end-group generated via beta-scission of growing polymer radical as a presumed chain-end forming reaction appeared only weakly. Thus, a plausible chain-end forming reaction would be the intramolecular (backbiting) hydrogen abstraction to form mid-chain radical which subsequently undergoes beta-scission resulting in oligomeric poly(BVE) radical was checked by using toluene as a solvent having labile hydrogen. The dependence of the degree of polymerization on initiator concentration was examined because the occurence of primary radical termination was remarkable, probably leading to reduce chain length. Finally, the reinitiation reaction by butyl group generated via beta-scission of mid-chain radical was pursued.

DOI： 10.1021/ma800949q

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

We have developed surface-assisted laser desorption/ionization mass spectrometry using zinc oxide (ZnO) nanoparticles with anisotropic shapes (ZnO-SALDI-MS). The mass spectra showed low background noises in the low m/z, i.e. less than 500 u region. Thus, we succeeded in SALDI ionization on low molecular weight organic compounds, such as verapamil hydrochloride, testosterone, and polypropylene glycol (PPG) (average molecular weight 400) without using a liquid matrix or buffers such as citric acids. In addition, we found that ZnO-SALDI has advantages in post-source decay (PSD) analysis and produced a simple mass spectrum for phospholipids. The ZnO-SALDI spectra for synthetic polymers of polyethylene glycol (PEG), polystyrene (PS) and polymethylmethacrylate (PMMA) showed the sensitivity and molecular weight distribution to be comparable to matrix-assisted laser desorption/ionization (MALDI) spectra with a 2,5-dihydroxybenzoic acid (DHB) matrix. ZnO-SALDI shows good performance for synthetic polymers as well as low molecular weight organic compounds. Copyright (C) 2008 John Wiley & Sons, Ltd.

DOI： 10.1062/jms.1385

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Polylactic acid (PLA) is a biodegradable polymer, currently used in pharmaceutical and surgical devices. There is a concern that cyclic polylactic acid (CPLA), which is a by-product of PLA synthesis, may be introduced into the human body as an undesirable contaminant. We Carried out a quantitation investigation of the CPLA heptamer (CPLA-7) by liquid chromatography mass spectrometry (LC-MS). We found that CPLA-7 binds strongly with serum proteins and that only 62% of CPLA-7 was recovered after routine deproteination; therefore, we directly injected serum into the LC-MS/MS system after passage through a bovine serum albumin (BSA)-coated chromatographic column and found the recovery of CPLA-7 was improved to 84%, and that the detection (S/N = 3) and quantitation limit (S/N = 10 and below 15% relative standard deviation) were 1.5 and 2.5 ng/mL, respectively. We conclude that direct injection LC-MS/MS, using a BSA column, is a simple and effective quantitative analysis method for CPLA in serum. (C) 2008 Elsevier B.V. All rights reserved

DOI： 10.1016/j.jchromb.2008.06.035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Using transmission electron microscopy (TEM) electron irradiation effects were studied for nanogroove-network structured single-crystalline and dendritic polycrystalline Pt nanosheets 50-60 nm in size. These two nanosheets with nearly the same average groove-width or dendritic spacing of 1.3-1.4 nm were prepared from the mixed and single surfactant liquid crystalline templates, respectively. On exposure to electron beam for 20 min at the acceleration voltage of 200 kV, the nanogrooved nanosheets were morphologically little affected, but the dendritic ones were transformed into less branched polycrystalline structures with spacings distributed around similar to 1.7 nm. The shape transformation of the latter occurred by the combined mechanism of segmental migration and atomic diffusion. These observations indicate that the nanogrooved Pt nanosheets are highly stabilized by the grooved but crystallographically continuous Pt framework, leading to their extremely high thermo-resistance, in marked contrast to the polycrystalline dendritic structures constructed of crystallographically discontinuous linkages of nanoblocks. (C) 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2007.05.019

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

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DOI： 10.1295/polymj.PJ2008019

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

No-template synthesis of surface clean platinum nanomaterials with thin projections (petals) on the Pt nanoparticle surface, termed Pt nanoflowers, has been developed, and Pt nanoflowers have achieved superior performance on surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) of biomolecules. With this new material, one can obtain high-resolution mass spectra with lower laser energy and smaller sample amounts, and no organic matrix is needed for laser desorption/ionization. The mass spectra also have fewer obstacle peaks at the lower m/z region. Furthermore, this novel substrate is quite stable against aging and showed no sweet-spot problems, that is, equal sensitivity on the whole substrate surface. Various biomolecules, including peptides and phospholipids, were examined, and Pt nanoflowers showed good performance for matrix-free laser desorption/ionization MS of these materials.

DOI： 10.1021/jp075159d

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the fabrication of self-organized surfactant nanofibers containing platinum ions on a highly oriented pyrolytic graphite (HOPG) surface from mixed solutions of hexadecyltrimethylammonium hydroxide (C16TAOH) and hydrogen hexachloroplatinate (IV) (H2PtCl6). The fibrous surfactant self-assembly was stable in air, even after being soaked in water, in contrast to surfactant hemicylindrical micelles, which are stable only at graphite/solution interfaces. The results show that the graphite surface served as an essential template for the specific formation of fibrous surfactant self-assemblies. In addition, when surfactant nanofibers containing metal ions were treated with hydrazine, platinum nanoparticles concentrated in the nanofibers formed on the HOPG surface. We also prepared surfactant nanofibers containing gold ions on HOPG surfaces and formed gold nanoparticles in the nanofibers.

DOI： 10.1021/la701020s

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

We first report the fabrication of submillimeter-sized Au plates (up to about I mm in size) through the simple thermal decomposition of HAUCl(4) in two-component ionic liquids of 1-butyl-3-methylimidazolium hexafluorophosphate (C4ImPF6) and 1-octyl-3-methylimidazolium hexafluorophosphate (C8ImPF6), which were about ten times larger sizes than those from the single-component ionic liquid of the either.

DOI： 10.1246/cl.2007.1038

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have investigated ultrasonic degradations of poly( ethylene oxide) ( PEG) and poly( methyl methacrylate) ( PMMA) in aqueous media by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The ultrasonic degradation of polymers was monitored as a function of ultrasonication duration to examine the structural details of ultrasonic degradation polymers. PEG solution ultrasonication produced five types of oligomers ((M) over bar similar to 1000 Da) with different end groups, irrespective of the initial average molecular masses (M = 2, 6, 20, and 2000 kDa). Several degradation pathways with free radical reactions have been suggested to explain these degradation products: the ultrasonic degradation of PEG is initiated by breaking of the C-O bond in the PEG chain, generating polymeric radicals with two terminal groups, i.e., X center dot( similar to CH2CH2 center dot) and Y center dot(similar to CH2CH2O center dot), followed by termination with extraction or release of a hydrogen atom. However, PMMA ((M) over bar = 1630 Da) ultrasonication generated only one type of degradation oligomer, which has a hydrogen group at both ends, the same as that of the original oligomer. It has been suggested that the presence of the radical terminal groups X center dot(similar to CH2 center dot) and Y center dot(similar to(CH3) CCOO(CH3) C center dot) is due to selective C-C bond breaking in the chain during the ultrasonic degradation of PMMA. The MALDI-TOFMS combined with the ultrasonic degradation technique (UD/MALDI-TOFMS) developed in this study could be extended to the analysis of synthetic polymer structures with high molecular weights.

DOI： 10.1021/ac062304v

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the effects of counterion species on the adsorption of cetyltrimetyl ammonium salts (C16TAX) onto gold surfaces and the subsequent formation of gold nanoparticles in the C16TAX surfactant solution. The surfactant adsorption onto gold surfaces was examined by using quartz crystal microbalance (QCM) and atomic force microscopy (AFM). The counterion species (X) examined in this study were as follows: X = Br-, Cl-, NO3, F-, OH-, and SO42-. The adsorption onto the gold surface depended on the counterion species of C16TAX-the frequency shift of QCM decreased in the following order: X = Br- &gt; NO3- approximate to SO42- &gt; Cl- &gt; F- &gt; OH-. The chemical reduction of gold(III) in the surfactant solutions of C16TAX with use of 2,2'-iminodiethanol as a mild reducing agent produced anisotropic gold nanoparticles, depending on the surfactant counterion. The high-affinity adsorption of Br, NO3, and Cl on gold surfaces produced anisotropic gold nanoparticles, while only spherical gold nanoparticles were obtained for weakly bound counterions such as SO42-, F-, and OH-. In contrast, the chemical reduction with hydrazine proceeded rapidly such that the shape of the gold nanoparticles was uncontrollable; this resulted in the formation of spherical gold nanoparticles, irrespective of the surfactant counterion.

DOI： 10.1021/jp066963n

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Single-crystalline Pt nanosheets with a nanogroove-network structure (see figure) are reported. A method of loading the nanogrooved Pt nanosheets on a carbon support is also described and the resulting nanogroove-networked Pt on a carbon support (Pt/C) is demonstrated to exhibit fairly high electrocatalytic activity for oxygen reduction, which is of interest for fuel cells.

DOI： 10.1002/adma.200601127

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS LTD  

Thin-layer chromatography (TLC) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) were combined to achieve characterization of polyether mixtures. Three polyethers, polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetramethylene glycol (PTMG), or mixtures of these compounds, were studied. One shortcoming of mixture analysis of synthetic polymers using MALDI-MS is that individual polymers in the mixture may display different detection sensitivities. For example, the MALDI mass spectrum of an equimolar mixture of PEG, PPG and PTMG displayed a high intensity of PPG ions, while no PTMG ions were detectable; however, PTMG ions were detected after the mixture had been separated by TLC. This combined TLC and MALDI-MS analysis of a PPG polymer bearing reactive epoxy groups showed that the polymer contained byproducts with different end-groups. These byproducts were identified as chloro-substituted polymers formed during polymer synthesis. Our study shows TLC to be a rapid and low-cost separation technique, and that it can be combined with MALDI-MS to achieve effective analysis of synthetic polymers. Copyright (c) 2007 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.2896

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Two-component Langmuir monolayers formed on 0.02 M Tris buffer solution (pH 7.4) with 0.13 M NaCl at 298.2 K were investigated for two different fluorinated-hydrogenated hybrid amphiphiles (F6PH5PPhNa and F8PH5PPhNa or F6 and F8, respectively) with DPPC. Surface pressure (pi), surface potential (Delta V) and dipole moment (mu(perpendicular to) as a function of molecular surface area (A) were measured by employing the Whithelmy method and an ionizing electrode method. From the A- and Delta V-X-F6 (or X-F8) curves, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined as a function of surface mole fraction (X-Fn) at discrete surface pressures. Then, the behavior of occupied surface areas and surface potentials of the respective components could be made clearer. Compressibility (C-s), elasticity (C-s(-1)), and excess Gibbs energy (Delta G((ex))) as a function of X-F6 (or X-F8) were estimated at definite pressures. These physico-chemical parameters were found to reflect the mechanical strength of monolayer films formed. The regular solution theory being applied to Delta G((ex)), the activity coefficients (f) as well as the interaction parameter (I-p) between DPPC and two hybrid amphiphiles in the binary monolayers were evaluated. I-p values thus obtained indicated that F8 molecules interact more strongly with DPPC molecules than F6. Moreover, in order to better understand the morphological monolayer state, Langmuir-Blodgett (LB) films made from DPPC and fluorinated-hydrogenated hybrid amphiphiles were examined by atomic force microscopy (AFM). The miscibility of the two components in the monolayer state is evidenced by these thermodynamic quantities and AFM observations. Furthermore, AFM images demonstrated that F8 could more effectively disperse the ordered domains of DPPC than F6. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfb.2006.07.019

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The shape transformation of platinum (Pt) nanosheets with a uniform thickness of as thin as 3.5 +/- 1 nm supported on graphite was investigated by in situ atomic force microscopy (AFM). The AFM observations revealed the shape transformation and the coalescence in preferred directions for the Pt nanosheets at room temperature (25 degrees C), which is much lower than the melting point of bulk metallic platinum (1769 degrees C). The behavior may be attributed to the high surface energy for the edge parts of Pt nanosheets with the small curvature of the nanometer scale. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2006.02.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The surface pressure (pi)-area (A), the surface potential (Delta V)-A, and the dipole moment (mu(perpendicular to))-A isotherms were obtained for monolayers made from a ganglioside originated from echinoderms [Diadema setosum ganglioside (DSG-1)], dipalmitoylphosphatidylcholine (DPPC), dimyristoylphosphatidylethanolamine (DMPE), cholesterol (Ch), and their combinations. Monolayers spread on several different substrates were investigated at the air/water interface by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM) and atomic force microscopy (AFM). Surface potentials (Delta V) of pure components were analyzed using the three-layer model proposed by Demchak and Fort [R.J. Demchak, T. Fort, J. Colloid Interface Sci. 46 (1974) 191-202]. The new finding was that DSG-1 was stable and showed a liquid-expanded film and that its monolayer behavior of Delta V was sensitive for the change of the NaCl concentration in the subphase. Moreover, the miscibility of DSG-1 and three major lipids in the two-component monolayers was examined by plotting the variation of the molecular area and the surface potential as a function of the DSG-1 molar fraction (XDSG-1), using the additivity rule. From the A--XDSG-1 and Delta V-m-XDSG-1 plots, partial molecular surface area (PMA) and apparent partial molecular surface potential (APSP) were determined at the discrete surface pressure. The PMA and APSP with the mole fraction were extensively discussed for the miscible system. The miscibility was also investigated from the two-dimensional phase diagrams. Furthermore, a regular surface mixture, for which the Joos equation was used for the analysis of the collapse pressure of two-component monolayers, allowed calculation of the interaction parameter (xi) and the interaction energy (-Delta epsilon) between them. The observations using fluorescence microscopy and AFM image also provide us the miscibility in the monolayer state. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfb.2006.07.006

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

One-dimensional (1-D) self-assemblies of Pt nanoparticles on a graphite surface have been synthesized via a template-directed sintering process of individual nanoparticles, using nonionic/cationic mixed hemicylindrical micelle templates of dodecyldimethylamine oxide surfactant at graphite/solution interfaces. The dimension and morphology of Pt nanoparticles can be widely controlled by the concentration of Pt ions equivalent to the mixing ratio of nonionic and cationic species in the surfactant micelle. This approach could be extended to fabricate a wide range of self-assembling metallic nanostructures on surfaces using various nonionic/cationic mixed micelle-like self-assemblies carrying metal ions at interfaces, while providing a fundamental insight into a 1-D self-assembly from individual nanoparticles. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2006.03.040

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A preliminary study on the reversible micelle-vesicle conversion of oleyldimethylamine oxide [Kawasaki, H. et al. J. Phys. Chem. B. 2002, 106, 1524] is extended in the present study. In the presence of 0.01 M NaCl at a surfactant concentration of 0.05 M, a micelle-to-vesicle conversion with increasing degree of ionization alpha takes place in the following sequence: growth of fibrous micelle (alpha &lt; 0.2), a fused network (alpha similar to 0.3), fibrous micelles + (perforated) vesicles (alpha = 0.4), and vesicles + lamellae (alpha = 0.5). Viscoelasticity correspondingly varies from the Maxwell-type behavior of the entangled network of fibrous micelles to the gel-like behavior of vesicle suspensions, via a fluid solution-like behavior of the fused network. This phase sequence is in contrast with the case of no added salt where no branching of micelles is observed, and long micelles and bilayers (vesicles + lamellae) coexist at alpha = 0.5. In water, a state of the lowest viscoelasticity occurs around alpha = 0.2 for both surfactant concentrations 0.05 and 0.15 M. Synergism between protonated and nonprotonated amine oxide headgroups is observed despite low ionic strengths. From the time course of the reversible micelle-vesicle conversion, vesicles seem to be formed from threadlike micelles within 25 h according to the shear moduli, while a longer conversion time is suggested by a flow property (viscosity). Shear thickening behavior is observed at alpha = 0.2 and 0.4 in 0.01 M NaCl but not in water.

DOI： 10.1021/jp056967c

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A double- tail amine oxide surfactant, di- n- decylmethylamine oxide ( 2C10MAO), was prepared, and the effects of protonation on aggregate structure were examined by small- angle neutron scattering ( SANS), cryotransmission electron microscopy ( cryo- TEM), turbidity, electric conductivity, and solubilization of an oil-soluble dye at various degrees of neutralization, X, defined as the mole ratio of HCl/ 2C10MAO. The surfactant makes an L-2 phase in the nonprotonated state ( X = 0) in water. The L-2 phase is in equilibrium with an aqueous L-1 phase. On protonation, unilamellar vesicles ( ULVs) are formed over a wide range of compositions ( 0.05 &lt; X&lt; 0.4- 0.5 at C = 10 mM) as observed by cryo- TEM. At X = 0.2, the ULV is stable over a wide concentration range ( 3 mM &lt;= C &lt; 0.1 M), but an L-alpha phase replaces the vesicle phase at C &gt; 0.1 M. SANS results show that the mean radius of the ULV is about 25 nm and the bilayer thickness is about 2 nm, consistent with the extended configuration of the alkyl chains of the surfactant. An important contribution to the enhanced stability of the bilayer structures over the L-2 phase is suggested to be the translational entropy of the counterions. The enhanced stability of the bilayers diminishes as the counterion concentration increases either by an increase of X or by the addition of a salt. When the counterion concentration exceeds a critical value, the ULV solutions transform into the L-2 phase ( or L-2/ L-1 two- phase system at low surfactant concentrations). The critical composition X* is about 0.4- 0.5 in water, but it is below 0.4 in D2O. The critical NaCl concentration is below 5 mM at X = 0.2. The stability of ULVs against multilamellar vesicles is ascribed partly to undulation forces and partly to the adjustable nature of the spontaneous curvature of amine oxide monolayers. The characteristics of the ULV of the surfactant remain the same within a temperature range 25 - 50 degrees C at X = 0.2. An iridescent lamellar phase and possibly an L-3 phase were observed in a very narrow X range ( 0 &lt; X &lt; 0.02) prior to the vesicle phase.

DOI： 10.1021/jp061335r

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In the present study, we investigated the effects of L-arginine on aggregates of fatty acid/fatty soap in the aqueous media as a function of pH, by means of hydrogen ion titration, viscoelastic measurement, cryotransmission electron microscopy and phase contrast microscopy. We found out that L-arginine effectively inhibits the oil droplet growth of oleic acid or octanoic acid. The effect is explained in terms of the adsorption of arginine at the microscopic drop surface, or at the oil/water microinterface through the hydrophobic effect assisted by the hydrogen bonds between carboxyl group of fatty acid and carboxylate of arginine. As to the crystallization of lauric acid at temperatures below the melting point of the hydrocarbon chain, arginine is not effective. In addition, we also found out that the strong binding of arginine cation to anionic oleate micells induces the dominant micellar growth. L-arginine has been used in many refolding systems to suppress protein aggregation. These effects of L-arginine on the aggregates of fatty acid/fatty soap in the aqueous media observed in the present study is expected to form a basis to the specific function displayed in the protein refolding.

DOI： 10.1007/s00396-005-1423-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Surface pressure (pi)-, surface potential (AV)-, and dipole moment (mu(perpendicular to))-area (A) isotherms and morphological behavior were examined for monolayers of a newly designed 18-mer amphiphilic alpha-helical peptide (Hel 13-5), DPPC, and DPPC/egg-PC (1:1) and their combinations by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM), and atomic force microscopy (AFM). The newly designed Hel 13-5 showed rapid adsorption into the air-liquid interface to form interfacial films such as a SP-B function. Regardless of the composition and constituents in their multicomponent system of DPPC/egg-PC, the collapse pressure (pi(c); -42 mN m(-1)) was constant, implying that Hel 13-5 with the fluid composition of egg-PC is squeezed out of Hel 13-5/DPPC/egg-PC monolayers accompanying a two- to three-dimensional phase transformation. FM showed that adding a small amount of Hel 13-5 to DPPC induced a dispersed pattern of ordered domains with a "moth-eaten" appearnce, whereas shrinkage of ordered domains in size occurred for the DPPC/egg-PC mixture with Hel 13-5. Furthermore, AFM indicated that (i) the intermediate phase was formed in pure Hel 13-5 systems between monolayer states and excluded nanoparticles, (ii) protrusions necessarily located on DPPC monolayers, and (iii) beyond the collapse pressure of Hel 13-5, Hel 13-5 was squeezed out of the system into the aqueous subphase. Furthermore, hysteresis curves of these systems nicely resemble those of the DPPC/SP-B and DPPC/SP-C mixtures reported before.

DOI： 10.1021/la0524925

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Hexadecyltrimethylammonium bromide (CTAB), which is necessary for the preparation of gold nanorods (NRs), was extracted from a NR solution into a chloroform phase containing phosphatidylcholine (PC). After three extractions, the zeta potential of the NRs remained positive, but its magnitude decreased from +67 +/- 1 to +15 +/- 1 mV. Transmission electron microscopy and energy-dispersive X-ray analysis indicated that the NRs were passivated with PC. The PC layer on the NR surface contributed to the prevention of NR aggregation. The PC-passivated NRs showed low cytotoxicity in comparison with twice-centrifuged NRs. It was shown that a negligible amount of CTAB was dispersed in the NR solution after the extraction. The extraction using a chloroform phase containing PC was found to be a convenient way of replacing the CTAB with alternative capping agents such as PC. This is a key technique for preparing functional NRs that can have practical applications.

DOI： 10.1021/la0520029

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Single-crystalline platinum nanosheets have been prepared via a new methodology based on the chemical reduction of a platinum salt (H2PtCl6) with hydrazine at a graphite/solution interface, using polyoxyethylene (20) sorbitan monostearate (Tween 60) based self-assembly (hemicylindrical micelle) templates. The platinum nanosheets with a uniform thickness of as thin as 3.5 +/- 1 nm are surface-smooth and continuous over relatively large length scales of micrometer sizes. In striking contrast to the Tween 60 based system, no Pt nanosheets are obtained with nonaethylene glycol monododecyl ether (C12EO9) and polyoxyethylene (23) dodecyl ether (C12EO23). No Pt nanosheets are also obtainable with a laterally homogeneous layer of Tween 60 formed at the silica/solution interface. These results indicate that surfactant Tween 60 molecules with a triple polyoxyethylene structure, as well as their hemicylindrical micelle templates, play an essential role for the formation of the Pt nanosheets. It is also suggested that the interfacially directed growth of Pt metals within the aqueous shells of the Tween 60 hemicylindrical micelles induces the thin Pt crystals as thick as the aqueous shells. The present approach could be extended to prepare a wide range of novel nanostructures of noble metals, using various micelle-like self-assemblies at interfaces.

DOI： 10.1021/la051247i

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Effects of micelle-to-vesicle transitions on the degree of counterion binding (beta) were investigated on three systems. For the concentration-dependent micelle-to-vesicle transition in the didodecyldimethylammonium bromide (DDAB)/water system, in the region of coexistent micelles and vesicles, less than 3 mM, the beta values increased significantly with DDAB concentration: beta(0.07 mM) = 0.35 and beta (3 mM) = 0.93. In the coexistent region, activities of the bromide ion, a(Br), were almost independent of the DDAB concentration, suggesting the pseudo-phase nature of both micelles and vesicles. In the concentration-dependent vesicle-to-lamellar transition region above 5 mM, where multilamellar vesicles were prevailing, on the other hand, the values were only little affected by this transition. This suggests that the increase in the layer number of DDAB multilamellar vesicles scarcely affects the values. This Was also Supported by the fact that the destruction of multilamellar vesicles by ultrasonication did not change the P values. These results strongly suggest that the inner and Outer monolayers of DDAB multilamellar vesicles are characterized by similar 6 values. The second system, cetyltrimethylammonium bromide (CTAB)/DDAB mixtures. showed composition-dependent transitions depending on the mole fraction of DDAB X-DDAB: spherical micelles (0 &lt; X-DDAB &lt; 0.2) -&gt; rodlike micelles (0.2 &lt; X-DDAB &lt; 0.4) -&gt; vesicles (0.6 &lt; X-DDAB &lt; 1). Values of beta increased with both the sphere-to-rodlike micelle transition and the micelle-to-vesicle transition. The increase in the value was larger for the latter than for the former transition. Little effects Of Ultrasoflication on was also observed for the multilamellar vesicles of CTAB/DDAB mixtures. In the third system of the mixtures of two single chain surfactants, protonated and non-protonated of oleyldimethylamine oxide, the dependence of beta on the degree of ionization (alpha) can be well described with a theoretical curve, derived on the basis of the linear relation between the surface charge density and the alpha value, despite the occurrence of the micelle-to-vesicle transition. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2005.02.021

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Lyotropic phase behavior of the nonionic and the half-ionized oleyldimethylamine oxide (O1DMAO)/water systems was investigated using polarized light microscopy, small-angle X-ray diffraction, and differential scanning calorimetry. Nonionic O1DMAO formed isotropic micellar solution, nematic, hexagonal, cubic, and lamellar liquid crystalline phases as the surfactant concentration increased. In contrast, half-ionized O1DMAO (i.e., 1:1 mixture of the nonionic and the protonated species) had a greater tendency to form bilayer structures, and the phase diagram became quite similar to those of double-chained ionic surfactants rather than single-chained ones, despite the introduction of positive charges to the nonionic one. The preference of the bilayer structures in the half-ionized O1DMAO was interpreted in terms of the dimers stabilized by the hydrogen bond between the nonionic and protonated species. For alkyldimethylamine oxides with a saturated hydrocarbon chain (CnDMAO, chain length: n = 14, 16, and 18), the phase sequence of lyotropic liquid crystals was hardly affected by the protonation, but an elongation of the cylinders of the hexagonal phase was observed for the half-ionized C14DMAO. Consequently, it can be considered that the dominant bilayer formation of the half-ionized O1DMAO is attributed to the combined effect of the hydrogen-bonded dimer formation and the cis-double-bond configuration of the alkyl chain.

DOI： 10.1021/la0503496

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The effects of ammonium salts and anionic amphiphiles on the formation and morphology of gold nanorods (NRs) in hexadecyltrimethylammonium bromide (CTAB) solutions were investigated. The addition of a small amount of tetrahexylammonium bromide (THAB) increased the aspect ratio of NRs. while an excess of THAB or tetradodecylammonium bromide (TDAB) decreased the aspect ratio, and concomitantly increased the formation of spherical gold nanoparticles. In contrast, the addition of anionic amphiphiles forming hydrophobic ion-complexes with CTAB did not decrease the aspect ratio, but suppressed the formation of NRs. These results could be attributed to the change in the adsorbed layer of CTAB on the gold NRs. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2004.10.015

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

We present a temperature-induced sedimentation/dispersion transition of ionic vesicles in the system of alkyldimethylamine oxide hemihydrochloride (CnDMAO.1/2HCl) with a hydrocarbon chain length of 12-16 (n = 12,14, and 16) and sodium 2-naphthalenesulfonate (NaNphS). The temperature-sensitive sedimentation/dispersion of ionic vesicles took place around a temperature of 50 degrees C, which was weakly dependent on the alkyl chain length. The combined effect of the thermally induced dissociation of the counterions from the vesicle and a hydrogen bonding between the nonionic and the cationic head groups is likely to be responsible for this unique behavior. (c) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2004.09.078

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The complex formation between nonionic alkyldimethylamine oxide (CnDMAO, n = 14, 16, and 18) and sodium palmitate (NaPa) in the solid phase of CnDMAO/NaPa mixtures and the dependence of the interaction parameter of the regular solution theory (RST) on the mixed micelle composition of C16DMAO/NaPa mixtures were investigated. The dissolution temperature showed a maximum at a NaPa mole fraction X*(Pa) of 0.3-0.4 for C16DMAO/NaPa and 0.2 for C18DMAO/NaPa. The compositions of the complexes suggested by X*(Pa) are C 16DMAO: NaPa = 3:2 or 2:1 and C18DMAO:NaPa = 4: 1. The composition X*(Pa) depended on the chain length of the amine oxides.The maximum was not observed in the case of the C14DMAO/NaPa/water system. In the range 0.7 less than or equal to X*(Pa) less than or equal to 1.0, dissolution temperature depression was observed with decreasing X-Pa. The dissolution temperature depression was analyzed by taking into account the nonideal behavior in the mixed micelles and the counterion binding on the mixed micelle surface. The negative values were obtained for all three mixed systems. It was shown that the counterion activity remained practically constant in the range of 0.7 less than or equal to X-Pa less than or equal to 1.0. The cmc values of C16DMAO/NaPa mixtures were determined by pyrene fluorescence measurement. For C16DMAO/NaPa mixtures, the dependence of the RST interaction parameter beta on the mixed micelle composition X-Pa was determined for a wide range (0.2 less than or equal to X-Pa less than or equal to 0.9). In the range 0.2 less than or equal to X-Pa less than or equal to 0.5, the beta values were obtained from an analysis of cmc based on the RST. In the range 0.7 less than or equal to X-Pa less than or equal to 0.9, the beta values were obtained from an analysis of the dissolution temperature depression. From the analysis of the micelle composition dependence of the P values, a short-range attractive interaction between the headgroup of C16DMAO and palmitate anion is suggested. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcis.2004.08.154

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

pH-induced transformation between a hemicylindrical aggregate and a laterally homogeneous layer at the graphite-solution interface was demonstrated in micellar aggregates of dodecyldimethylamine oxide (C12DMAO) using atomic force microscopy (AFM). Nonionic C12DMAO (pHsimilar to8) and fully-ionized cationic C12DMAO (pHsimilar to1.5) both formed hemicylindrical aggregates on graphite, similar to aggregates formed by many other ionic (or nonionic) surfactants on graphite. However, a laterally homogeneous layer was observed in the case of nearly half-ionized C12DMAO around pHsimilar to4 (a 1:1 mixture of the nonionic and the cationic species). These results indicated that the surface curvature of the C12DMAO aggregates on graphite was the smallest around the degree of ionization alpha=0.5, despite charging up the nonionic hemicylindrical aggregates. Using AFM images and the corresponding force curves, the transformation between the hemicylindrical aggregate and the laterally homogeneous layer was found to be reversible via a change in pH. The formation of the laterally homogeneous layer of nearly half-ionized C12DMAO is explained by hydrogen bond formation between the nonionic and the cationic headgroups.

DOI： 10.1007/s00396-004-1146-8

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DOI： 10.1016/j.colsurfb.2004.06.013

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Effects of the surfactant concentration C-d and the NaCl concentration C-s on the electrophoretic mobilities U of the well-characterized polymer-like micelles have been investigated by the electrophoretic light scattering, using tetradecyldimethylamine oxide hemihydrochloride (C14DMAO . 1/2HCl). At the high ionic strength of 0.1 mol kg(-1) NaCl, the electrophoretic mobilities were independent of C-d (5 mM &lt; C-d &lt; 100 mM), despite the concentration-dependent micelle growth of the polymer-like micelles. This suggests that the electrophoretic mobility of the polymer-like micelle at high ionic strengths is independent of the contour length (i.e., the molecular weight), as found on linear polyelectrolytes. Somewhat surprisingly, the entanglements of the polymer-like micelles gave small effect on the electrophoretic mobilities in the examined range of the surfactant concentration above an overlap concentration. The mobilities of the polymer-like micelle decreased with rootC(s) in a single exponential manner in the range of C-s front 0.02 to 0.3 mol kg(-1). It is suggested that the cylinder model can be applied to the electrophoretic mobilities of the polymer-like micelles at high ionic strengths (i.e. a free-draining behavior), since the persistence length of the polymer-like micelle (similar to20 nm) is much larger than the Debye length at high ionic strength. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfa.2004.04.097

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We studied the effects of the degree of ionization(alpha) and the surfactant concentration (C-d) on the micelle-vesicle transition in salt-free oleyldimethylamine oxide (OlDMAO) aqueous solutions by the dynamic light scattering (DLS), the hydrogen ion titration, the small angle neutron scattering (SANS), the electrophoretic light scattering (ELS) and viscoelastic measurements. From the study of ionization effects, the micelle-vesicle transition was recognized as a change of aggregate size by the DLS measurement; however, the micelle-vesicle transition was not detected both in the ELS measurement and the hydrogen ion titration, suggesting that the electric properties of the worm-like micelles and the vesicles are very similar despite a large difference of shapes between them. From the results of the SANS, the DLS and the viscosity measurements, it was suggested that a concentration-dependent micelle-vesicle transition took place around C-p = 10 mmol kg(-1) for the solutions at alpha = 0.5. In the concentration-range 10 mmol kg(-1) &lt; C-d &lt; 150 mmol kg(-1), the micelles and the vesicles coexisted. In the concentration region (C-d = 10-50 mmol kg(-1)), the vesicle size increased with the surfactant concentration. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.colsurfb.2004.04.011

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The correlation between the dispersion stability of graphite particles suspended in aqueous solutions of dodecyldimethylhydroxylammonium chloride (C12DMAOH.Cl) and the structure of the adsorption layer on the graphite surface was investigated by a combination of data from AFM images, measurements of interaction forces, an adsorption isotherm, and turbidity measurements of graphite suspensions. A model for the two-step adsorption mechanism was successfully applied to describe the adsorption isotherm. (The first step was the formation of the horizontal adsorbed monolayer, and the second step was the formation of the hemicylindrical aggregate.) It was suggested that there is a transition regime where the horizontal adsorbed monolayer coexists with the hemicylindrical aggregate. A dispersion of graphite particles is unstable in the presence of the horizontal adsorbed monolayer. Surface force measurements suggest that the surface charges of the horizontal adsorbed monolayer are mostly neutralized by the bound counterions. The critical hemimicelle concentration (hmc) was about 0.8 mM, which was about (1)/(10) of the bulk critical micelle concentration (cmc approximate to 6 mM). The hmc value was close to the critical concentration at which the suspension stability started to increase dramatically with the surfactant concentration. We found that a stable dispersion of graphite particles can only be achieved once the hemicylindrical aggregates have formed on the surface at full surface coverage, leading to the development of the electric double layer forces from the positively charged aggregate.

DOI： 10.1021/jp0488970

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JOHN WILEY & SONS INC  

The volume change of crosslinked nonionic poly (N-isopropylacrylamide) (NIPA) polymer gel immersed in tetradecyldimethylaminoxide (C14DMAO) surfactant solutions at 0.1M NaCl, were investigated to distinguish between binding and nonbinding polymer gel/C14DMAO surfactants. Also, the aggregation behavior of C14DMAO surfactants the inside and the outside the polymer hydrogels has been studied through solubilization of Sudan III dye. For the C14DMAO surfactants at the degrees of ionization (alpha) of 0.5 and 1, they bind to the NIPA gel at low surfactant concentration (C-D) that enhance the gel swelling due mainly to the osmotic pressure contribution from the counter ions (regime I, C-D&lt;10mM). However, the deswelling behavior was observed as the surfactant concentration increases above 10 mM (regime II). The solubilization experiments indicated that the surfactant concentration inside the gel is lower than that outside the gel in the regime 0 11, which may be due to the large micelle size that cannot accommodate the mesh size of the gel. It was suggested that the uneven distribution of the ionic micelles leads to the reduction of the net swelling osmotic pressure of the gel (i.e., the decrease of the gel volume). In the case of the nonionic C14DMAO at alpha = 0, on the other hand, the deswelling behavior was not clearly observed and the surfactant concentration inside the gel and outside the gel was almost identical even at 30 mM. For the nonionic surfactant, it was also found that the gel volume increases with the surfactant concentration at low surfactant concentration less than 1mM. This may be attribute to the dipole-dipole repulsion of N-O headgroups. (C) 2004 Wiley Periodicals, Inc.

DOI： 10.1002/app.20634

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Vesicle formation in a mixture of oleyldimethylamine oxide (OleylDMAO) and sodium oleate (NaOl) was investigated by viscoelastic measurements and cryoscopic transmission electron micrograph (cryo-TEM) observations. The viscoelastic properties changed with increasing mole fraction of NaOl (X-NaOl) from the Maxwell behavior of OleylDMAO solutions (X-NaOl=0) suggesting a transient network of long flexible chains. For X-NaOl=0.2 and 0.4 mixtures, both the shear storage modulus G' and the shear loss modulus G' showed weak dependences on angular frequency omega with a relation G'&gt;G'. From cryo-TEM observations, vesicles coexisted with threadlike micelles in mixtures of X-NaOl=0.2 and 0.3. As X-NaOl increased further (X-NaOl=0.5 and 0.6), threadlike micelles disappeared and the coexistence of vesicles and globular micelles was observed. At X-NaOl=0.5, the viscosity decreased remarkably, which was consistent with the disappearance of threadlike micelles. The results indicated that vesicles were formed by the addition of NaOl to OleylDMAO solutions, contrary to the expectation of a decrease of the packing parameter with the introduction of electric charges.

DOI： 10.1007/s00396-004-1049-8

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The influence of adding alkyldimethylamine oxide (CnDMAO) with varying alkyl chain lengths (n(c)) on the acid soap formation of oleic acid was investigated. The solutions of equimolar mixtures of CnDMAO and sodium oleate (Na(+)Ol(-)), each 25 mmol kg(-1), became turbid at a certain critical pH (pH(c)) on decreasing pH. Values of the pH(c) depended on n(c) and showed the minimum at C10DMAO/NaOl mixture. The presence of the minimum was interpreted in terms of two different kinds of the complex formed in the micelles depending on n(c): the catanionic complex (CnDMAOH(+)/Ol(-)) in the mixed micelles of n(c)=16, 14, 12 and 10, and the acid soap of oleic acid for C6DMAO/NaOl and C8DMAO/NaOl mixtures. At pH(c) where the amounts of these complexes of double-chain nature reached certain critical values in the mixed micelles, a phase separation (most probably lamella formation) took place. It was expected that the critical amount of the catanionic complex was smaller for the mixtures of higher n(c) values and hence pH(c) increased with n(c) for the mixtures n(c)greater than or equal to10. For the mixtures of n(c)&lt;10, it was expected that the amount of the acid soap in the mixed micelles increased with decreasing n(c) at a given pH and the pH(c) increased with decreasing n(c). Micelle compositions at cmc were evaluated on the basis of the regular solution theory coupled with the pseudo phase approximation. The micelle compositions at 100 mmol kg(-1) were examined with C-13-NMR. The results showed the mixed micelle formation for n(c)=16-10, while the micelles mostly consisting of oleic acid for the mixtures of n(c)=8 and 6. The assumption of two different complexes for the two groups of the mixture was thus supported. The cmc range of mixed micelles was evaluated and it was well correlated with the observed concentration range of pyrene fluorescence change.

DOI： 10.1007/s00396-003-0970-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A new proton-conducting intercalation system of a layered polysilicate compound, octosilicate (RUB-18), was synthesized by exchanging Na+ ion with half- and full-ionized dodecyldimethylamine oxides. RUB-18 intercalated by half-ionized dodecyldimethylamine oxide was shown to contain alkyl chains of the trans zigzag conformation by powder X-ray diffraction and C-13 CP-MAS NMR measurements. The DC electrical conductivity and the distribution factor beta of the relaxation time were determined to be 6.4 x 10(-6) S m(-1) and 0.67, respectively, from Cole-Cole plots of the complex impedance measured at room temperature under the relative humidity of 100%. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2003.09.014

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

The protonation effect of tetradecyldimethylamine oxide (Cl4DMAO) on the aggregate structures (a surfactant concentration, Ct = 2 x 10(-2) mol kg(-1)) in water at 25degreesC was examined by adding aromatic sulfonic acids of 2-naphtalenesulfonic acid (NphH). It turned out that partially protonated C14DMAO formed vesicles in the range of the degree of the protonation a from alpha = 0.25 to alpha = 0.5. The critical vesicle formation concentration (cvc) of the vesicle at alpha = 0.4 was suggested to be around Ctsimilar to3 x 10(-4) mol kg(-1), which was very close to the critical aggregation concentration (cacsimilar to8 x 10(-5) mol kg(-1)). The kinetics of the micelle-to-vesicle transition by changing pH was examined and it could be analyzed as a first-order process. The rate constant on the vesicle formation was found to increase linearly on both the temperature and the ionic strength of the solution. Contrary to the vesicle formation process, the vesicle breakdown process was too fast (&lt; 10 s) to follow in the measurable time scale. The leakage experiment of glucose from the vesicle was carried out with the vesicles. To examine effects of the hydrophobicity of the aromatic sulfonic acids on the aggregate structures, the aggregate structures were also examined for such as benzenesulfonic acid (BzH) and p-phenolsulfonic acid (PheH). In the case of the BzH, the interaction was much weaker than that of the NphH and the phase separation occurred by protonation. PheH was found to be almost ineffective to induce a significant structural change of the micelle, in spite of the hydrophobic nature of the aromatic counterion.

DOI： 10.1007/b100303

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Combination of chemical reduction of tetrachloroaurate by ascorbic acid and subsequent ultraviolet photoirradiation resulted in the quick generation of gold nanorods quantitatively, with appreciable shape changes as the reaction proceeds.

DOI： 10.1039/b307836a

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Spontaneous vesicle formation was found to occur on simple mixing of two solutions: a micellar solution of tetradecyldimethylamine oxide hemihydrochloride (C14DMAO.1/2HCl) and a sodium 2-naphthalenesulfonate (NaNphS) salt solution. The stability of the vesicle dispersion and the sign of the vesicle charge depended on the mixing mole ratio beta (=[NaNphS]/[C14DMAO.1/2HCl]) at 25 degreesC: elongated micelles (beta &lt; 0.25) --&gt; positively charged unilamellar vesicle dispersion (0.3 &lt; beta &lt; 0.5) --&gt; sediments consisting of aggregated multilamellar vesicles (0.55 &lt; beta &lt; 0.75) --&gt; negatively charged unilamellar vesicle dispersion (0.75 &lt; beta &lt; 5). The beta-dependent aggregation behavior of the vesicles correlated well with the change in the potential of the vesicles, and it was described by the normal DLVO theory. This indicates that the repulsive double-layer force is a major factor in stabilizing the vesicle dispersion, while the main driving force of the aggregation is an attractive van der Waals force between the vesicle bilayers. CryoTEM pictures demonstrated that the vesicles showed a drastic change in microstructure upon aggregation. In the aggregated multilamellar vesicles, the electrostatic repulsion between the bilayers is suppressed by the complete binding of counterions NphS(-), leading to the change from unilamellar vesicles to aggregated multilamellar vesicles. It is suggested that vesicle formation in the C14DMAO.1/2HCl-NaNphS system can be attributed to the combined effect of the hydrogen bonding between the cationic and the nonionic headgroups (-N+-OH...O-N-) and the strong counterion NphS- binding.

DOI： 10.1021/jp0300804

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Hydrogen ion titration profiles of the aqueous potassium oleate/oleic acid systems were examined as a function of the degree of neutralization, beta, in corresponding metal chloride solutions. At temperatures higher than 5 degreesC, the titration curves were almost identical to those of sodium oleate systems at temperatures higher than 20 degreesC characterized by a single constant-pH region due to the multiple-phase equilibrium including metal oleate micelles. At a low temperature, 0 degreesC, on the other hand, different titration curves characterized by two constant-pH regions were observed. The ranges of beta of the high constant-pH region were 0.6 &lt; beta &lt; 0.95 in contrast to the sodium oleate system (0.5 &lt; beta &lt; 0.95). These results suggested that the acid soap compositions, oleate acid/metal oleate ratios, were 2:3 for the potassium oleate and 1: 1 for the sodium oleate systems. Differential scanning calorimetry analysis for the potassium oleate/oleic acid and the sodium oleate/oleic acid two-component systems detected the formation of an acid soap with equivalent compositions in aqueous media. To inspect further the changes in the temperature profiles of the titration curves, the temperature dependence of the solution properties of potassium and sodium oleates was examined.

DOI： 10.1007/s00396-002-0753-5

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We investigated the phase behavior of cationic tetradecyldimethylhydroxylammonium chloride (C14DMAOH(.)Cl) (a fixed surfactant concentration, 20 mM) in the presence of sodium 2-naphthalenesulfonate (SNphS) as a function of the molar ratios beta (= SNphS/C14DMAOH(.)Cl) by turbidity, viscosity, dye solubilization, and polarizing microscopy. The C14DMAOH(.)Cl/SNphS system formed aggregates with a lower curvature than cetyltrimethylammonium bromide (C16TAB)/aromatic counterion systems, despite the shorter alkyl chain. Addition of SNphS into the C14DMAOH(.)Cl solution at 25 C produced precipitates of solid crystals above beta similar to 0.5, in contrast with long fibrous micelles of many other cationic micellearomatic counterion pairs. The crystalline solids (tetradecyldimethylhydroxylammonium naphthalenesulfonate, C14DMAOH(.)NphS) at 20 mM concentration were transformed into the lamellar liquid crystalline phase dispersion (lamellar droplets) above 54 C. The lamellar phase was not spontaneously converted into vesicles upon dilution to 1 mM in contrast to spontaneous vesicle formation of cetyltrimethylanimonium hydroxynaphthalenecarboxylate (C16TAHNC). The stability of the lamellar droplets was rather limited in the low surfactant concentration of 1 mM. The phase separation into the lamellar liquid crystalline phase and the clear isotropic solution was observed within several hours. By gentle shaking by hand, on the other hand the lamellar phase could be dispersed to lamellar droplets at 60 degreesC again. The fact that the C14DMAOH(.)NphS prefers the planar bilayer structure (a precipitate or a lamellar liquid crystalline phase) to the curved bilayer structure (vesicles) may manifest the rigid surface of the bilayers. Compared with C16TAHNC, the rigid nature of the C14DMAOH(.)NphS bilayer is likely due to the proposed hydrogen bond formation between the two neighboring cationic headgroups, where their charge repulsion was now suppressed by the counterion binding. To examine effects of the hydrophobicity of the counterion on the phase behavior, similar experiments were carried out for sodium benzenesulfotiate (SBzS) and Na2SO4. In the case of the SBzS, the interaction was much weaker than that of SNphS and no lamellar droplets were observed at elevated temperatures. Na2SO4 was found to be ineffective to induce a structural change of the micelle, despite consisting of divalent counterions.

DOI： 10.1021/la0205021

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The effects of the heterogeneity of the gel on the swelling behavior and on the binding of surfactant counterions, dodecylpyridinium chloride (C12Py), were examined using copolymer gels of N-isopropylacrylamide and p-styrene sulfonate (pSS). The feed mole fractions of pSS, X, were 0.05, 0.1, 0.15, 0.20 and 0.25. The gels prepared at 40 +/- 2 degreesC were turbid, indicating heterogeneous monomer densities on a microscopic scale, while the gels prepared at 41 degreesC were transparent. Significantly different swelling behavior was observed on changing the temperature between the two kinds of gel: the change in gel volume in a given temperature interval was always smaller for the heterogeneous gels than for the homogeneous gels. The binding isotherms of C12Py were, in contrast, very similar between the two kinds of gel. The cooperative parameter of the binding, u, was rather small (2-4) for both types of gel. This small cooperativity was ascribed to relatively low charge densities. A small but significant decrease in u was found when X increased.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

The effects of protonation (ionization) of hexadecyldimethylamine oxides on the dissolution temperature in aqueous media were investigated by differential scanning calorimetry. Only one endothermic peak was reproducibly observed at all the degrees of ionization a examined that were assigned to the transition from the solid (the gel phase) to the solution containing micelles. The dissolution temperature versus alpha curves showed a maximum at alpha = 0.5, strongly suggesting the formation of a stable complex of 1-to-1 composition of the nonionic and cationic species through the proposed hydrogen bond. From the shape of the dissolution curve as well as the composition analysis of the solid phase, the solid solution was found to be formed over all alpha values. Effects of alkylchain length on the dissolution temperature for a homologous series of octadecyl- (C18DAO), hexadecyl- (C16DAO), and tetradecyldimethylamine oxide (C14DAO) were also examined for alpha = 0.5 and alpha = 1. Both the transition temperature and the associated thermodynamic quantities DeltaH and DeltaS increased systematically with the chain length, but for alpha = 0.5 smaller increases in DeltaH and DeltaS values with the chain length were observed [DeltaH/CH2 (kJ mol(-1)) = 7.2 +/- 0.2 and 2.2 +/- 0.5 for alpha = 1 and alpha = 0.5, respectively, and DeltaS/CH2 (J mol(-1) K-1) = 21.9 +/- 1.8 for alpha = 1 and 4.6 +/- 1.9 for alpha = 0.5]. By annealing procedures, the metastable nature of the gel phase was demonstrated for the C16DAO (alpha = 1) solid. (C) 2002 Elsevier Science (USA).

DOI： 10.1006/jcis.2002.8458

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Protonation of oleyldimethylamine oxide (OleylDAO) decreased the average curvature and induced a change from threadlike micelles in the nonionic state to particles (vesicles) at the half-protonated state (degree of ionization alpha = 0.5), concluded from viscoelastic measurements and cryoTEM observations in water at 25 degreesC. The viscoelastic changes were confirmed to be reversible with respect to a pH change. The times required for the solutions to recover the behavior at alpha = 0.5 after the addition of HCl to the solutions of alpha = 0 were about 25 h at 0.05 mol (kg water)(-1) and 14 days at 0.15 mol (kg water)(-1). The correspondence between the viscoelastic properties and the cryoTEM observations was good. It was suggested from the viscoelastic properties that the threadlike micelles grew with alpha at alpha = 0.2, but the change from threadlike micelles to vesicles was suggested as alpha increased further. On increasing the concentration at alpha = 0.5, the vesicles became perforated, probably due to the increased counterion concentration. The present results indicate unambiguously the important and effective action of protonation in controlling the packing parameter, or the mean curvature, of amine oxide amphiphiles.

DOI： 10.1021/jp013366m

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The binding of a cationic surfactant, dodecylpyridinium (C12Py) chloride, with a low-charge-density poly (methacrylic acid) (PMA) was investigated in buffer solutions under the condition of constant pH. The binding isotherms with PMA consisted of two and three steps at a pH lower and higher than 3.2, respectively. Bindings in the first step were independent of pH and this step was considered to correspond to the solubilization of the hydrocarbon chains of C12Py into the nonpolar region of the compact form of PMA. This is the indication of the compact form from the binding isotherm. At pH higher than 3.2, the second step was discriminated and it depended on the pH. In the third step, a sharp rise in the degree of binding (beta) was observed accompanying the solubilization of the precipitates of the PMA-C12Py complex. The binding with poly(acrylic acid) (PAA) and PMA in conventional unbuffered NaCl solutions was also examined and the pH profile of the solution during the binding process was determined. In the case of unbuffered NaCl solutions, the binding with PAA took place cooperatively at the critical association concentration (cac). The binding isotherm consisted of two steps and the pH decreased with the increase in beta. The binding isotherm of PMA, on the other hand, consisted of three steps: the pH decreased slightly in the first step and considerably in the second step with the increase in beta but it increased with beta in the third step, exhibiting a pH minimum around 3.2. The binding in the first step coincided with that obtained in the buffered solutions. Linear relationships between beta and the pH were found for both polymers. In the case of PMA, no cac was observed in both buffered and unbuffered NaCl solutions.

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We have investigated the effects of ionization on the aggregate structures of tetradecyldimethylamine oxide (C14DAO) at the mica-solution and graphite-solution interfaces by atomic force microscopy. It was found that the C14DAO forms aggregate structures with lower curvature at the mica-solution interface as the degree of ionization of C14DAO increased. Nonionic C14DAO formed short cylindrical aggregates on mica. On the other hand, a flat bilayer on mica was observed for the half-ionized C14DAO1/2HCl and the fully ionized C14DAOHCl. The flat bilayers for C14DAO1/2 HCl and C14DAOHCl suggest the higher packing parameter (or lower mean curvature) character of these surfactants, compared to the cationic quaternary ammonium surfactant with a single tetradecyl tail as well as the nonionic C14DAO which all form the cylindrical aggregates on mica. The reason for this lower curvature of half-ionized C14DAO was suggested to be the hydrogen bonds between the headgroups (i.e., the cationic-nonionic pair for C14DAO1/2 HCl), in addition to the contribution of the electrostatic attractive interaction between the cationic headgroup and the negatively charged mica. Contrary to the aggregates on mica, the dominant structures of C14DAO an graphite were hemicylinders, irrespective of the ionization. It seas found that the ionization increased the distances between the hemicylindrical aggregates due to the electrostatic repulsion between the aggregates rather than induced the change in the aggregate structure. The weak dependence of the ionization on the aggregate structures at the graphite-solution interface is suggested to be due to the dominant attractive interaction between the graphite surface and the surfactant tail.

DOI： 10.1021/la010934g

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Solid phase behaviors of alkyldimethylamine oxide hydrochlorides (CnDAO . HCl) and hemihydrochlorides (CnDAO .1/2HCl) were investigated by differential scanning calorimetry (DSC) and infrared spectroscopy on five members n=10, 12, 14, 16 and 18. Two main transitions were commonly detected by DSC on the protonated (cationic) species (CnDAO . HCl): the order-disorder transition of the hydrocarbon chain (or chain melting) and the melting to a liquid crystalline(LC) phase. Both the chain-melting transition temperature T-chain and the associated thermodynamic quantities DeltaH(chain) and DeltaS(chain) increased systematically with the chain length. Only one phase transition assigned to the partial chain melting was detected by DSC on the hemihydrochlorides (CnDAO .1/2HCl) except for n = 12. The associated enthalpy changes DeltaH(tr) were smaller than DeltaH(chain) of the corresponding hydrochlorides by about 10-15 kJ mol(-1). For the hydrochlorides, the high temperature solid phase (S2) was stable only for a limited temperature range. On the contrary, the S2 phase of hemihydrochlorides was stable over a considerable temperature range. This stable nature of the hemihydrochlorides suggested the attractive head group interaction inferred from the previous solution studies. (C) 2001 Elsevier Science B.V. All rights reserved.

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Marked effects of protonation (ionization) of tetradecyldimethylamine oxide on the viscoelastic properties of the micelle solutions were found. The effect strongly suggests the short-range attractive interaction between the headgroups of the nonionic (deprotonated) and the cationic (protonated) species. The zero shear viscosity reached a maximum at the half-ionized state (the degree of ionization alpha = 0.5) and the value was larger than that of the nonionic species (alpha = 0) or the cationic species (alpha = 1) by more than 2 orders of magnitude. At a surfactant concentration C of 0.1 mol/kg, approximately single Maxwell behavior was observed as a approached 0.5 from either side. For the half-ionized micelles (alpha = 0.5) in 0.1 mol/kg NaCl solutions, the steady-state compliance J(e)(0) decreased with C with an exponent of 2.1 +/- 0.2, suggesting the presence of an entangled network of flexible threadlike micelles. The relaxation time, on the other hand, exhibited a nonlinear dependence on C. It was about 0.1 s and remained nearly constant in the range C &gt; 0.1 mol/kg (regime I), whereas it increased with C in the range of C &lt; 0.09 mol/kg (regime II) with an exponent slightly larger than 1. The single Maxwell behavior was observed in regime I. The regime shift was not controlled by the ratio C/m(s), m(s) representing the NaCl concentration. Effects of NaCl concentration and the temperature on the viscoelastic properties were also examined at alpha = 0.5. Cryo-transmission electron micrographs clearly showed a highly entangled network in the solution for alpha = 0.5, while much smaller micelles for alpha = 0. Contrary to the expectation from the theological results, a highly entangled network was also observed in the solution for alpha = 1.

DOI： 10.1021/jp0101155

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The salt effect on the phase transition of N-isopropylacrylamide (NIPA) gel was studied. The swelling behavior of the NIPA gel strongly depends on the salt concentration and is well described as a function of the chemical potential difference of water molecules in solution from that at the transition. From the analysis of the OH stretching, Raman spectra in water and in various aqueous solutions in terms of collective proton motions reveals that the presence of salts tends to disrupt or distort the water molecules in hydrophobic hydration shell around the NIPA gel. This leads to inducing the growth of the cluster shell around the salts, which leads to gel collapse. The volume phase transitions due to the different types of perturbation (temperature, salt) are induced by the same mechanism, hydrophobic hydration and dehydration, and therefore can be described in a unified manner in terms of the chemical potential and the collective proton motions of water molecules. (C) 2000 American Institute of Physics. [S0021-9606(00)52037-6].

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Solid phase behaviors of dodecyldimethylamine oxide (C12DAO) studied by differential scanning calorimetry and X-ray scattering have shown clearly the effects of protonation. Besides the protonated (cationic) (C12DAO HCl) and the nonionic (C12DAO) species, 1:1 composition or hemihydrochloride (C12DAO 1/2 HCl) was shown to be a stable complex. The phase behavior of C12DAOHCl was similar to that of dodecylammonium chloride rather than dodecyltrimethylammonium chloride (C12TACl), although similar crystal structure was suggested for C12DAOCl and C12TABr. Solid phase behaviors changed dramatically by changing the counterion from Cl- to NO3- or SO42- for both the cationic and 1:1 species. (C) 2000 Elsevier Science B.V. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACS  

Aqueous solutions of half-ionized tetradecyldimethylamine oxide (TDAO) with 0.1 M NaCl and varying surfactant concentration were studied by small-angle neutron scattering. The scattering data demonstrate the presence of wormlike micelles, and an analysis based on polymer theory and the results from Monte Carlo simulations was performed. The surfactant concentrations correspond to dilute and semidilute solutions for the wormlike micelles. The analysis of the forward scattering demonstrates a concentration dependence of the growth of the micelles in agreement with mean-field theory. The scattering data in the full range of measured scattering vectors were analyzed using a modified random phase approximation expression, and excellent agreement was found for concentrations up to 65 times the overlap concentration. The model fitting showed that the micelles have an elliptical cross section with semiaxes of about 16 and 28 angstroms. Based on the self-consistent analysis, an independent comparison between the correlation length determined from the scattering data and from Monte Carlo simulations was performed as a function of the reduced concentration.

DOI： 10.1021/la000085h

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We investigated the aggregate morphologies of tetradecyl-dimethylamine oxide hemihydrochloride (C14DAO . 1/2HCl) on mica surface in the surfactant solutions by Atomic Force Microscopy (AFM). C14DAO . 1/2HCl forms a flat bilayer on mice. This morphology is different from spheres or cylinders which have been reported for other cationic surfactants with a single tetradecyl tail. The reason for this lower curvature of the C14DAO . 1/2HCl aggregate on mica is discussed in terms of the hydrogen bond between the headgroups.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Effects of the introduced charge on the thermal behavior of N-isopropylacrylamide (NIPA) gel were investigated by differential scanning calorimetry (DSC) for copolymer gels of NIPA and sodium styrenesulfonate (NIPA-SSNa) with various charge densities of the chains and ionic strengthes. As the SSNa contents of the NIPA-SSNa gel increased, the sharp endothermic peak of the NIPA gel in water changed into a broad one and the excess enthalpy change per mole of NIPA monomer (Delta H) decreased. The Delta H value is most likely related to the amount of the dehydration of NIPA chains. In NaCl solutions, however, the sharp endothermic peak was observed again for the NIPA-SSNa gel and the Delta H value was similar to that of the NIPA gel. We found that the DSC curve was very similar to the derivative profile of the swelling curve with respect to temperature both in water and in NaCl solutions. The good correspondence between the derivative curve and the DSC curve suggests that the volume shrinkage of the gel and the specific heat change of the gel are closely related. This similarity most probably originates from the fact that the temperature-induced volume shrinkage of the gel is caused by the dehydration of NIPA chains. On the basis of this correlation, the effect of the introduced charge on the DSC curve (i.e., the shape of the endothermic peak and the Delta H value) is explained in terms of the Donnan osmotic pressure of counterions.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Effects of the gel size on the thermal behavior and the shrinking profile of chemically cross-linked poly( N-isopropylacrylamide)( NIPA)gel in water were mainly investigated by differential scanning calorimetry( DSC) and the volume measurement at the same heating rate as the DSC. The DSC thermogram of NIPA gel depended on the shrinking process at the transition. The DSC thermogram of NIPA gel of the smallest size ( 0.3 mm diameter at the preparation) gave double endothermic peaks and the gel underwent a discontinuous volume shrinkage ( i.e. a volume transition) at about 34.5 degrees C within the time scale of DSC run of heating rate of 0.1 degrees C/min. This suggests that the two-step cooperative dehydration of NIPA chains takes places in the volume shrinkage. It was proposed that the peak at the low temperature( peak 1) originated from the dehydration of NIPA chains without the volume transition while the peak at the high temperature ( peak 2) was associated with the discontinuous volume shrinkage. A single broad endothermic peak was observed for NIPA gel of the largest size (3 mm diameter at the preparation) that shrank only slightly during DSC run. For the largest gel, the volume transition cann0 ot occur within the time scale of DSC run due to the slow volume shrinkage while dehydration of the polymer chains takes place locally. The peak of the largest gel and the peak 1 were suggested to be due to the dehydration of NIPA chains coupled with the spinodal decomposition without the volume transition.

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

Effects of the introduced electric charges on the swelling behavior of a thermosensitive gel, N-isopropylacrylamide (NIPA), were examined with the copolymer gels with sodium acrylate(NaA) or sodium styrene sulfonate (NaSS). The introduced charge altered the volume change behavior of NIPA gels from the discontinuous type (the volume phase transition) to the continuous one by a very small amount, less than 0.01 mole fraction. This charge effect was suppressed by the addition of a salt, NaCl, and at the NaCl concentration of about 0.3 M or higher, the transition behavior was resumed. These effects of the charge and the salt were both understood in a unified manner in terms of the Donnan osmotic pressure of the shrunken state of the gels. In parallel with the change of the swelling behavior, the endothermic peak observed at the transition temperature of NIPA gels in the DSC measurements became smaller and broader as the mole fraction of the charged monomer increased. The solution nature of the shrunken state of NIPA gels was suggested from the effects of sugars and/or salts on the volume phase transition. This solution nature was suggested to be kept in the shrunken state of ionized NIPA gels. This is the prerequisite to the above interpretation of the charge effect in terms of the Donnan osmotic pressure of the shrunken state. Temperature-induced volume changes of the copolymer gels of NIPA with sodium acrylate were examined at various pH. The volume change of the gel was discontinuous against temperature at pH below 6.3, although it was continuous at pH above 7.5. Potentiometric titrations of the linear copolymer of NIPA and acrylic acid ( PNIPA-AA ) revealed that the dissociation constant of carboxyl groups in solutions decreased with raising temperature above 34 degrees C. The similar decrease in the carboxyl ionization with raising temperature was also observed for NIPA-AA gel. The resumed discontinuous volume change at neutral or acidic pH was correlated with the two effects arising from the protonation of the carboxylate groups of NIPA-AA gel :the reduced Donnan osmotic pressure and the presence of a significant fraction of unionized carboxyl groups in the gel at the collapsed state. The nature of the shrunken state under these pH values was suggested to differ considerably from that of NIPA or ionized NIPA gels. It is not solution-like but a space of low dielectric constant similar to the interior of globular proteins.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The theory for describing the effect of Donnan osmotic pressure on the volume phase transition of NIPA gel is developed. The theory can well explain the experimental result that a continuous volume change behavior of charged NIPA gel in a salt-free solution turns to a discontinuous one in 0.1 M salt solution.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC CHEMICAL ENG JAPAN  

The paraldehyde chemical heat pump is combined with a chemical reaction and a vapor-compression heat pump. The paraldehyde chemical heat pump generates cold thermal energy with depolymerization of paraldehyde (2,4,6-trimethyl-trioxane). The cooling rate of the paraldehyde chemical heat pump depends on the catalyst activity of the paraldehyde depolymerization. This study investigates the effect of the acid strength of the solid catalyst on the paraldehyde depolymerization rate, the cooling rate, and the coefficient of performance of the heat pump. The acid strength distribution of Amberlyst 15 E was measured for estimation of the catalyst activity of the paraldehyde depolymerization. The depolymerization rate was measured with Amberlyst 15 E of modified acid strength distribution. The high activity range of the acid strength is -7.1 &lt; pKa &lt; -4.3 for the paraldehyde depolymerization with Amberlyst 15 E. The coefficient of performance, the cooling rate and the catalyst weight were estimated with the acid strength. The weight of the catalyst can be reduced to 0.05 g with 1.6 g.s(-1) of the flow rate in the system when the cooling rate and COP are 0.9 kW and 6, respectively.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Effects of the gel size on the thermal behavior and the shrinking profile of a chemically cross-linked poly(N-isopropylacrylamide) (NIPA) gel in water were investigated by differential scanning calorimetry (DSC) and the volume measurement at the same heating rate as used for the DSC. The DSC thermogram of NIPA gel depended on the shrinking process at the transition. The DSC thermogram of the NIPA gel of the smallest size (0.3-mm diameter at the preparation) gave double endothermic peaks, and the gel underwent a discontinuous volume shrinkage (i.e. a volume transition) at about 34.5 degrees C in the DSC run with a heating rate of 0.1 degrees C/min. This suggests that the two-step cooperative dehydration of NIPA chains takes places in the volume shrinkage. It was proposed that the peak at the low temperature (peak 1) originated from the dehydration of NIPA chains without the volume transition while the peak at the high temperature (peak 2) was associated with the discontinuous volume shrinkage. A single broad endothermic peak was observed for the NIPA gel of the largest size (3-mm diameter at the preparation) that shrank only slightly during the DSC run. For the largest gel, the volume transition cannot occur within the time scale of the DSC run due to the slow volume shrinkage while dehydration of the polymer chains takes place locally. The peak of the largest gel and peak 1 were suggested to be due to the dehydration of NIPA chains coupled with the spinodal decomposition without the volume transition.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A temperature-induced volume change of ionic gels was investigated for cross-linked copolymer gels of N-isopropylacrylamide and sodium acrylate (NIPA-AA) at various pH values, The volume change of the gel against temperature was discontinuous below pH 6.3, but it was continuous above pH 7.5. The continuous volume change observed for the completely ionized NIPA-AA gel suggests that an increase in the counterion osmotic pressure alters the discontinuous volume change of NIPA gel to the continuous one. Potentiometric titrations revealed that the dissociation constant of carboxyl groups of the linear copolymer of N-isopropylacrylamide and acrylic acid in solution decreased with increased temperature above 34 degrees C. The similar decrease in the carboxyl ionization with increasing temperature was also observed for NIPA-AA gel. The discontinuous volume change was correlated with the two effects arising from the decrease in the carboxyl ionization of NIPA-AA gel: the reduced Donnan osmotic pressure and the presence of a significant fraction of un-ionized carboxyl groups in the gel at the collapsed state.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the temperature-induced volume phase transition behavior of a copolymer gel of N-isopropylacrylamide and sodium acrylate (NIPA-AA) at pH 9.5 in the range of low mole fraction of the acrylate x (x &lt; 0.01), either in salt-free aqueous solution or NaCl aqueous solutions. Introduction of electric charges into the network switched the temperature-induced volume change of the gel from a discontinuous to a continuous type in salt-free aqueous solutions. The switching of the regime took place within a very narrow range of x around a very small value of 0.002. The continuous volume change in salt-free aqueous solution was transformed into the discontinuous one in NaCl aqueous solutions of 0.1 and 0.3 M. Effects of the two factors, the charged monomer fraction and the ionic strength, were explained in a unified manner in terms of the Donnan osmotic pressure. We found that the continuous or the discontinuous regime of NIPA-AA gel was well characterized, respectively, by the high or low osmotic pressure. Similar results were obtained with NIPA-sodium poly(styrene sulfonate) copolymer gels.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Effects of the gel size on the thermal behavior and the shrinking profile of poly(N-isopropylacrylamide)(NIPA)gel in water were investigated by differential scanning calorimetry(DSC) and the volume measurement at the same heating rate. The DSC thermogram of NIPA gel of the smallest size gave double endothermic peaks and the gel underwent a discontinuous volume phase transition during DSC run. On the other hand, a single endothermic peak was observed for NIPA gel of the largest size and the gel shrank only slightly during DSC run due to the slow volume change.

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Authorship：Lead author   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jp963772j

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Saccharide-induced volume phase transition of poly(N-isopropylacrylamide) (NIPA) gels was found fur glucose, galactose, and sucrose, and the transition concentrations were about 1.5, 1.3, and 1.2 M, respectively. Temperature-induced volume phase transition of NIPA gels was affected by these saccharide, and the transition temperature decreased with increasing concentration of the saccharides. The reduced extent of the transition temperature increased linearly with the decrement of the chemical potential of water molecules due to the saccharides. This indicates that the change of the chemical potential of water induced by the addition of the saccharide plays an essential role in the saccharide-induced volume phase transition of NIPA gels.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

The surface tension of poly(N-isopropylacrylamide) gel is measured as a function of temperature. It is found that the surface tension of the gel suddenly decreases as the gel undergoes the discontinuous volume phase transition. The surface tensions of the polymer network of the gel are evaluated on the basis of a simple theory. The results yield that the surface tension of the poly(N-isopropylacrylamide) gel is mainly determined by the area occupied by the polymer chain on the surface of the gel in most of the temperature regions. In addition, it is also found that the surface tension of the polymer network of the gel shows a singular behavior in the immediate vicinity of the volume phase transition temperature of the gel.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The volume phase transition is studied in the ternary system of the nonionic poly (N-normalpropylacrylamide) gel, water, and various alcohol. The gel shows a reentrant volume phase transition in all mixed solvent systems studied here. It is found that the phase transition is multiple in the mixed solvent systems of water-1-propanol and water-2-propanol. These results are discussed by the mean field theory in which the effects of the chain stiffening due to the adsorption of the solvent molecules are taken into account. These results strongly suggest that the adsorption and/or the desorption of the solvent molecules promote the multiple phase transition of the nonionic poly (N-normalpropylacrylamide) gel. (C) 1995 American Institute of Physics.

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Total pages：2, 8, 351, 9p, 図版10p   Language：Japanese  

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DOI： 10.1016/B978-0-12-822350-5.00009-6

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