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Yoshimoto S.,Kumamoto University | Yoshimoto S.,Kumamoto Institute for Photo Electro Organics | Itaya K.,Tohoku University
Annual Review of Analytical Chemistry | Year: 2013

We describe the history of electrochemical scanning tunneling microscopy (STM) and advances made in this field during the past 20 years. In situ STM allows one to monitor various electrode processes, such as the underpotential deposition of copper and silver ions; the specific adsorption of iodine and sulfate/bisulfate ions; electrochemical dissolution processes of silicon and gold single-crystal surfaces in electrolyte solutions; and the molecular assembly of metalloporphyrins, metallophthalocyanines, and fullerenes, at atomic and/or molecular resolution. Furthermore, a laser confocal microscope, combined with a differential interference contrast microscope, enables investigation of the dynamics of electrochemical processes at atomic resolution. Copyright © 2013 by Annual Reviews. Source


Tominaga M.,Kumamoto University | Tominaga M.,Kumamoto Institute for Photo Electro Organics | Sasaki A.,Kumamoto University | Togami M.,Kumamoto University
Analytical Chemistry | Year: 2015

Achieving oxygen reduction at high positive potentials with fast heterogeneous electron transfer is desirable for the biocathode of fuel cells based on enzymes. Here, we present an effective interface for obtaining direct electron transfer from a laccase (Lac)-based cathode for O2 reduction, starting from a potential very close to the redox equilibrium potential of the oxygen/water couple. The interface between Lac and single-walled carbon nanotubes was improved by modification with the steroid biosurfactant sodium cholate. The heterogeneous electron-transfer rate between the type-1 Cu site of Lac and the modified electrode was determined to be 3000 s-1. The electron-transfer rate was sensitive to the side chain of the steroid biosurfactant, and the rate decreased more than 10-fold when sodium deoxycholate was used as the side chain. © 2015 American Chemical Society. Source


Saita K.,Kumamoto University | Saita K.,Kumamoto Industrial Research Institute | Nagaoka S.,Kumamoto Industrial Research Institute | Nagaoka S.,Kumamoto Institute for Photo Electro Organics | And 7 more authors.
Carbohydrate Research | Year: 2012

We synthesized new dispersive chitosan particles at circumneutral pH. Particles composed of a chitosan-borate complex were synthesized by a method consisting of two simple steps: mixture and dialysis. As this method does not employ reagents such as organic solvents or surface-active agents and does not require heat treatment, it has a minimal negative impact on the environment. Crosslinking of the reaction of glucose and boric acid at ordinary temperature and pressure led to the formation of composite particles. Stereoscopic microscopy and investigation of the particle size distribution by dynamic light scattering (DLS) revealed that particles ranging in size from submicrons to several microns with high dispersibility in water were obtained. Even after heat treatment at 80°C for 12 h, the particles maintained their composite formation, indicating that they have high thermal stability. Chitosan powders demonstrated inadequate antimicrobial properties at circumneutral pH, but the particles of the chitosan-borate complex had antimicrobial properties against the gram-negative bacterium, Escherichia coli, and the gram-positive bacterium, Staphylococcus aureus, as well as the fungi Aspergillus niger and Fusarium solani. These results indicated that the particles of the chitosan-borate complex had a broad antimicrobial spectrum at circumneutral pH. © 2011 Elsevier Ltd. All rights reserved. Source


Kuwahara Y.,Kumamoto University | Kuwahara Y.,Kumamoto Institute for Photo Electro Organics | Kaji M.,Kumamoto University | Okada J.,Kumamoto University | And 5 more authors.
Materials Letters | Year: 2013

We demonstrated fabrication of photo-mechanical materials alternatively-including azobenzene-side-chained acrylate polymer, PMAz6Ac, and polyvinyl alcohol, PVA, without cross-linking. The multi-bilayered (PMAz6Ac/PVA)n films were obtained by alternative spin-coating methods of PVA and PMAz6Ac solutions on glass substrates. After thermal treatment, the azobenzene groups as mesogen were self-organized and were induced out-of-plane orientation. After UV irradiation (λ=375 nm), the self-standing films obtained by peeling off was bent to an opposite side of the light source, and the bended film reverted toward the initial position by following visible light irradiation (λ>420 nm). Their optical properties of the PMAz6Ac layers indicated that change of molecular orientation, out-of-plane orientation and disordered random, of azobenzene groups in the PMAz6Ac layers closely related with the photo-mechanical behaviors. © 2013 Elsevier B.V. Source


Kuwahara Y.,Kumamoto University | Kuwahara Y.,Kumamoto Institute for Photo Electro Organics | Oda T.,Kumamoto University | Izumi R.,Kumamoto University | And 5 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

A few research group reports formation of ordered structures of colloidal particles due to topological defects in a nematic liquid crystal. In this paper, we describe the photochemical phase transition of a nematic liquid crystal by the photoisomerization of azobenzene dyes, focusing especially on the dynamical effect of the trans-cis-trans photoisomerization cycle of a push-pull azobenzene dye. Then, we discuss the effects of light irradiation on the motion of small objects dispersed in the nematic and smectic liquid crystals contatining a push-pull azobenzene dye, and successfully manipulate those objects by pushing, trapping and dragging them. © 2014 SPIE. Source

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