Previously documented results on molecule manipulation using metal nanogates are comprehensively reviewed to conclude novel characteristics, which could be widely used for the developments of the systems at electrified interfaces. Novel systems to segregate molecules from self-spreading lipid bilayers in electrolyte solutions have been developed by using metal nanogate structures on solid surfaces. The spatial distribution of target molecules in the lipid bilayer changes depending on the molecule characteristics, such as charge, size, and flexibility. Energy dissipation during the spreading of the molecules on the surface contributes to the compression of the lipid bilayer at the nanogate, leading to the formation of a gradient of the electrochemical potential of the bilayer system including the target molecule in the vicinity of the nanogate (<100 nm from the gate). The gradient results in a segregation force being applied to target molecules in the order of 10⁻¹⁵ N per molecule. The segregation property can be tuned by changing the electrolytes, lipid molecules, temperature, and the width and surface hydrophobicity of the metal nanogate. Introduction of asymmetry to the nanogate leads to further effective diffusion control in a direction perpendicular to the spreading. It has been demonstrated that target molecules with a different number of glycolipid per protein in the lipid bilayer are effectively separated based on the Brownian ratchet mechanism.

View full abstract

This paper summarized the author’s recent studies about effective design of the systems for environmental and dental application of TiO₂ photocatalysts and boron-doped diamond (BDD) electrodes. The titanium mesh impregnated photocatalyst, TMiP™ has been fabricated as a novel photocatalytic filter. The high mechanical flexibility of TMiP allows us to design any geometry of modules by combination of UV-sources and the other technologies. In this paper, a practical air-cleaner using the TMiP-plasma synergistic reactor was fabricated and installed in a real-scale smoking room in the office. The amounts of the compounds in tobacco smoke were almost totally removed by the air-cleaner. On the other hands, the author also reported the possibilities of wastewater treatments by electrolysis with BDD electrodes. Based on these studies, a novel pinpoint ozone-water production unit for dental treatment using of BDD microelectrodes was developed. The unit showed almost the same sterilization ability as conventional 20 ppm of aqueous sodium hypochlorite treatment in in vitro assessment in the root-canal of bovine teeth. These results present several key solutions for practical applications of TiO₂ photocatalysis and BDD electrolysis.

View full abstract

We have developed three types of photoelectrochemical nanomaterials and devices based on metal and/or semiconducting metal oxide nanoparticles for effective use of light energy. Photocatalysts with oxidative energy storage abilities were developed by coupling a photocatalyst with a rechargeable metal oxide or metal hydroxide nanomaterial to address an issue that TiO₂ photocatalyst does not function after dark. Plasmonic metal nanoparticle ensembles were thermally and/or chemically stabilized by using a metal oxide nanomask or ultrathin metal oxide coating and applied to localized surface plasmon resonance sensors and photovoltaic cells based on the plasmon-induced charge separation. Organic and organic-inorganic hybrid photoelectrodes were also developed to give photocurrents enhanced by optimally arranged plasmonic metal nanoantennas.

View full abstract

Anion-exchange membrane fuel cell (AEMFC) is a relatively new member of the family of polymer electrolyte fuel cells (PEFCs) as an electrochemical system for electric power sources. Alkaline environment in the anion-exchange membranes provides some advantageous characteristics for AEMFCs. In this comprehensive paper, some attractive features of AEMFCs are briefly explained as compared with proton-exchange membrane fuel cells (PEMFCs), and our recent results on electrocatalysts and triple-phase boundary in AEMFCs are discussed.

View full abstract

Fullerene, C₆₀, is readily reduced to its anion radical, C₆₀^•−, in nitrobenzene (NB) that contains a tetraphenylborate ion (TPB⁻) under irradiation with visible light. Fullerene excited by visible light withdraws one electron from TPB⁻ to form C₆₀^•− and generated TPB radical decomposes. C₆₀^•− can be stored for several days without any changes in deaerated NB. However, as soon as the NB solution containing C₆₀^•− is bubbled with air, C₆₀^•− immediately oxidizes to C₆₀. Using this photochemical reaction of C₆₀, we have developed a new-type of photovoltaic cell that can generate and store electricity. We call this cell a photoelectrochemical condenser (PEC). The anodic reaction of the PEC is the oxidation of C₆₀^•− to C₆₀; although many reduction reactions are possible, the cathodic reaction is chosen to be the reduction of Fe³⁺ to Fe²⁺ in an aqueous phase. When the PEC was irradiated with visible light ranging from 400 nm to 700 nm (23.4 mW cm⁻²), the electromotive force was measured to be approximately 1100 mV, and an electric current of approximately 2 mA was observed. In this paper, we present the PEC and discuss its performance for generating and storing electricity.

View full abstract

High purity tantalum ethoxide (99.997%) was successfully synthesized using electrosynthesis method and characterized by IR and ¹H-NMR spectra, the influence of various factors on the electrosynthesis process and the distillation purification of tantalum ethoxide was also studied. Cell voltage was closely related to process parameters such as electrolyte species, electrolyte concentration, electrode distance, solution temperature, current density and electrolysis time et al. All the current efficiencies were higher than 100%, which might be related to the low valence sate of tantalum. The ideal conditions for the electrosynthesis of tantalum ethoxide were also obtained. The purity of tantalum ethoxide increased when increasing reflux ratio. Infrared spectra conformed to chemical bonds excellently, and the peak area ratio of nuclear magnetic resonance coincided with number ratio of hydrogen atoms.

View full abstract

NiO, Co(OH)₂, Ir oxide, and Ru oxide were combined as rechargeable materials with TiO₂ or Pt-TiO₂ photocatalyst to obtain novel photocatalysts with oxidative energy storage abilities. NiO, which is more stable than the conventional storage material, Ni(OH)₂, showed similar characteristics to those of Ni(OH)₂. The redox potential of Co(OH)₂ was more negative, and those of Ir oxide and Ru oxide were more positive than that of Ni(OH)₂. The photoelectrochemically charged Ir oxide was reduced by acetone, acetic acid, Br⁻, and water. The diversity of energy storage materials was accordingly improved in terms of the reaction potential and stability.

View full abstract

High infrared-absorption films having low cost and light weight are indispensable for infrared sensors. We developed IR-adsorption coatings with low-reflectance and low-transmittance at wavelengths of 3–13 µm, based on a copper electroplating film pretreated with chemical etching and subsequent blackening. The chemical etching and blackening respectively produced columnar and feather-shaped structures on a copper surface. The reflectance and the transmittance of the films were below 15% and below 1% at wavelengths of 3–13 µm, respectively. The current coating technique might be useful to develop high absorption, low cost, and lightweight infrared absorbers.

View full abstract