Two types of preparation processes for highly ordered hole array structures of anodic porous alumina are described. In the naturally occurring ordering, long-range ordered hole configuration was obtained under appropriate anodization conditions. The pretexturing process using a mold yielded ideally ordered hole configuration with a single domain structure over the sample. Obtained highly ordered anodic porous alumina membranes were applied to preparation of several types of functional nanodevices. In addition, replication processes using highly ordered anodic porous alumina as a starting structure are described. Highly ordered metal and semiconductor hole arrays prepared by the replication processes were applied to the preparation of several types of functional electrodes.

Nano-sized particle manganese dioxides were synthesized by reduction process using NaMnO₄ precursor and fumaric acid as the reducing agent. Transmission electron microscopy examination showed size distribution of particles besides in the range of a few to 10 nm. The high specific capacity of 350 mAh g⁻¹ was observed during first charge. The electronic structure of synthesized samples before and after lithium ion intercalation and/or deintercalation was investigated by Mn L-edge and O K-edge X-ray absorption spectroscopy.

Large mesoporous SnO₂ powders have been prepared from SnCl₄·5H₂O by a templating method using a triblock copolymer as a surfactant. Ethanol-rinsing of resulting precipitates resulted in formation of large mesoporous SnO₂ powder having a broad pore size distribution with a maximum pore volume around 15 nm after calcination at 400 °C for 5 h. Treatment of as-precipitated products with phosphoric acid was not useful for improving the thermal stability of large mesoporous structure, whereas it prevented the growth of SnO₂ crystallites during the calcination. In contrast, large mesoporous SnO₂ powders having a sharp pore size distribution with a maximum pore volume around 3.5 nm and a specific surface area larger than 70 m² g⁻¹ could be prepared by deionized water-rinsing. It was revealed that aging treatment of as-precipitated products led to a more uniform pore size distribution after the calcination, although the specific surface area decreased accordingly.

Mixed proton-electron conducting nanocomposites have been formed based on a hydrous ruthenium oxide and a proton-conducting polymer for new supercapacitor energy storage nanomaterials with high capacitance and excellent rate capability. The nanocoating was carried out by polymerizing nano-ordered poly [3-(4-aminophenyl)propionic acid] (PAPPA) thin film on the surface of the hydrous ruthenium oxide nanoparticles under ultrasonic irradiation. From the transmission electron microscopy observation, PAPPA film was found to form compactly and thinly on aggregated hydrous ruthenium oxide particles with diameter of ca. 20 nm (primary size). At a low scan rate of 2 mV s⁻¹, the specific capacitance obtained for the nanocomposite electrode was 1210 F g⁻¹ which was higher than that for the ruthenium oxide nanoparticles itself (975 F g⁻¹). More importantly, the nanocomposite thin-film electrode maintained its high capacitance (ca. 1000 F g⁻¹) even at an ultrafast scan rate of 1000 mV s⁻¹.

Single crystals of Al₂O₃ nanoparticles were successfully synthesized by dc electrolysis of the Al³⁺ ion conducting Al₂(WO₄)_2.4(MoO₄)_0.6 solid solution electrolyte at 11 V, 900°C. The particle size can be intentionally controlled by adjusting the electrolysis period: the particles distributed in the range of 100-900 nm, and the average size was 440 nm for 3 days electrolysis, while the range and the size became 100-1400 nm and 520 nm after the electrolysis for a week, respectively. Electron diffraction patterns for each particle evidenced that the particles grown were δ-Al₂O₃ because the present electrochemical method was applicable at moderate temperatures around 900°C.

In order to evaluate the photocatalytic ability of TiO₂ film, quartz crystal microbalance (QCM), which is a gravitation method, was employed instead of the conventional absorption method. The advanced sol-gel method, which can control thickness to the several tenths of a nanometer level, was applied to the coating on the QCM element. India ink coated on the QCM element was used as the model material for the photo-decomposition. The amount of decomposition during UV light irradiation was detected by the frequency-shift. This method was also tested in application to an organic gas sensor.

Preparation technique of Pt monolayer islands has been developed by combining two techniques ; the preparation of nanopores in a self-assembled monolayer of alkanethiol and deposition of Pt monolayer using Cu adlayer as a reducing agent. This novel technique gives remarkably uniform monolayer islands for island sizes ranging from 3 to 11 nm.

Preparation of polypyrrole (PPy) containing Pt nanoparticles was attempted. The oxidation of pyrrole into polypyrrole proceeded by H₂PtCl₄, simultaneously reducing Pt(IV) to Pt(0). The Pt particles were obtained with average size of 2 nm and fairly narrow size distribution. Moreover, the maximum content of Pt reached over 20 wt% without any evidence of aggregation. The optimum [Pt]/[Py], for obtaining successful Pt/PPy composite including highly concentrated Pt and exhibiting high electrical conductivity, was determined at R = 0.6.

Suppression of substrate heating during film deposition is necessary to realize a high rate deposition of ITO films on plastic film substrate. In a sputter-deposition of the film using a conventional magnetron sputtering system, heating power incident into substrate was measured and mechanisms of the substrate heating were investigated precisely. Most of the incidence power into the substrate is originated in the bombardment of high-energy secondary electrons emitted from the target, and can be reduced to 1/9 by removing the electron bombardment. Compared with the total incidence power to the substrate, the heat of formation of the film was estimated to be below 1/50. This suggests that further reduction of the incidence power into substrate will be possible in the deposition using a conventional magnetron sputtering system.

Nano-scale crystal formation in copper magneto-electrodeposition under parallel magnetic fields was examined with X-ray diffraction. In 30 mol m⁻³ copper sulfate solution, below the overpotential −0.2 V, the average crystal size decreased with magnetic field, whereas beyond −0.2 V, the average crystal size increased in the higher range. The atomic force microscope images of the deposits also showed the same tendency.

Microscale Bi electrodeposition process was developed to fabricate the array of mushroom-shaped absorbers for the high sensitive X-ray imaging sensor, so called X-ray microcalorimeter array. The bath composition and operating conditions for Bi electrodeposition was optimized, and sufficient bath stability and surface smoothness of the deposits were achieved by applying the additives such as diethylenetriamine pentaacetic acid and sodium n-dodecyl sulfate with appropriate concentration. By applying the two-step exposure steps for the “stem” part and the “roof” part, the mold to deposit the mushroom-shaped microstructure was formed from single-layered photoresist coating. The absorber array was successfully fabricated by the sequential processes of Bi electrodeposition into the mold, precise polishing, and mold removal.

Ag ad-layer modified Au(100) and Au(111) electrodes showed excellent catalytic behavior for oxidation of aldose type (such as glucose, maltose, galactose and xylose) sugars. The best catalytic effect was observed at a (√2 × 5√2)R 45° Ag-Au(100) electrode, 2/5 monolayer of Ag on Au(100), where the oxidation of glucose began at −0.7 V (vs. Ag/AgCl) with a negative shift of ca. 0.2 V in oxidation potential compared to the oxidation at a bare Au(100) electrode. As was observed at a (√3 × √3)R 30° Ag-Au(111) electrode, 1/3 monolayer of Ag on Au(111), the catalytic oxidation of glucose was also seen at Au(111) film electrodes with large surface areas after deposition of Ag ad-layer.

Uniform size nanorods consisting of polypyrrole were synthesized via electropolymerization using a porous alumina template. The dispersion of polymer particles was obtained by dissolving the template in an alkaline solution followed by dialysis with distilled water. SEM-EDS and TEM techniques revealed that synthesized polypyrrole nanoparticles are rod-shaped having a diameter of 20 nm.

In this study, the effect of a dissolved gas on Pd deposition at the silicon substrate in the solutions saturated with various gases in a glove box is investigated. The number of Pd nanoparticles deposited in the solution saturated with the mixed gas (10% H₂ and 90% N₂) is less than with the air and pure oxygen gas. Also, the average size of Pd particles deposited in the hydrogen atmosphere is larger than in the air and oxygen atmospheres. In the solution containing the dissolved H₂ gas, the Pd nucleus significantly grows, and there are small numbers of Pd particles, because H₂ oxidation occurs only at the Pd nucleus.

Direct electron transfer-type bioelectrocatalysis of four-electron reduction of dioxygen was successfully realized with bilirubin oxidase (BOD, EC 1.3.3.5, from Myrothecium verrucaria) at carbon electrode surfaces with high crystal graphite edge density. It was found that adsorbed BOD functions as a biocatalyst. The current-potential curves were interpreted by considering the enzyme catalytic constant, surface electron transfer kinetics, surface concentration of BOD, and the formal potential of BOD. The analysis suggested that the standard surface electron transfer rate constant and surface coverage of “active” enzyme depend strongly on functional groups and/or nano-structure of carbon electrode surface.

DNA-Ru(bpy)₃²⁺ complex was prepared to study EL characteristics. Ru(bpy)₃²⁺ was associated with duplex of DNA by the interaction such as intercalation in the pH 3 aqueous solution. It was revealed that the EL device composed of DNA-Ru(bpy)₃²⁺ complex exhibited extremely faster response than the other Ru(bpy)₃²⁺ based EL devices. The emission mechanism was discussed. DNA-Ru(bpy)₃²⁺ complex is expected to be applicable to an optoelectro-functional molecular wire.

The photoelectrochemical behavior of the Pt/TiO₂ nanocomposite electrodes in aqueous 0.1 M Na₂SO₄ electrolyte was investigated. Pt/TiO₂ nanocomposite films (platinum nanoparticles dispersed in TiO₂ films) and TiO₂ films deposited on ITO glass substrates by the sputtering were used as electrodes. Anodic photocurrent of Pt/TiO₂ nanocomposite electrode at potential higher than 0.5 V vs. Ag/AgCl under the irradiation of Xenon lamp was one order smaller in the magnitude than that of TiO₂ electrode, resulting from the recombination between hole and electron at Pt particles. Anodic photocurrent of Pt/TiO₂ nanocomposite electrode at 1.0 V vs. Ag/AgCl was observed at the wavelength region of visible light. Pt/TiO₂ nanocomposite electrodes have remarkably different photoelectrochemical behaviors compared with that of pure TiO₂ electrodes.

Co-deposition characteristics of refined nanodiamond particles (5 nmϕ) into electrolessly plated nickel films were studied. Effects of concentration, temperature and pH of the baths were investigated. It is suggested that nanodiamond particles are co-deposited into the film after adsorption on a surface of the plated film. The authors found that the content of diamond particles in the film increased with decreasing deposition rate and decreasing hydrogen evolution rate accompanied by plating reaction. The content did not exceed 2% when we use an ordinary plating solution; ammoniacal-citrate nickel plating bath.

The redox properties of a series of “center-to-edge” phosphorus(V) porphyrin arrays composed of similar porphyrin units were investigated by cyclic voltammetry. From the assignments of the reduction peaks, it was revealed that small difference of electron-donating ability of the axial ligands and the electrostatic intramolecular interaction affect their redox potentials. Moreover, the comparison of the reduction potentials enables to determine the polarization direction of the charge transfer excited-state of the porphyrin arrays.

For the development of the preparation method of size-controlled nanoparticles, we applied the liquid phase deposition (LPD) method to the reverse micelle (RM) reaction contained TritonX-100 and 1-hexanol. We prepared two kinds of metal oxide nanoparticle; TiO₂ and SnO₂. The average sizes of nanoparticles were 5.9 nm and 3.0 nm for TiO₂ and SnO₂, respectively. The size distribution was narrow, and crystallization of the particles was promoted by the nano-scale reaction field. The bandgap was calculated from UV-Vis spectra. The bandgap energy of SnO₂ nanoparticles showed a larger value at 4.6 eV, whereas that of TiO₂ nanoparticles showed a constant value at 3.2 eV. The quantum effect causes the variation of the bandgap, however, the effect depends on the kinds of the metal oxide.

TiO₂ thin film, which has high photocatalytic property, was fabricated from its precursor solution by spin-coating method. The solution was prepared by the recently developed advanced sol-gel method. This liquid process is based on the hydrolysis and polymerization of Ti alkoxide in mixed solvent of butanol and toluene. The obtained solution was transparent without precipitate and stable, and thus the metal oxide precursor solution was prepared. TG-DTA analysis of the powder dried in vacuum and XRD patterns of the annealed films showed that the crystalline anatase phase appeared at 300°C. This temperature is lower than that obtained from the conventional sol-gel method. From AFM imaging, the surface of TiO₂ thin film coated on quartz or glass substrates appeared flat. The photocatalytic activity of TiO₂ thin film prepared by advanced sol-gel method was higher than that prepared by conventional sol-gel method.

Adlayer structures of S on Cu(100) and Cu(110) were investigated by using in situ scanning tunneling microscopy (STM) in alkaline solution. On Cu(100), the adsorbed S formed a structure, whereas a c(2 × 8) structure was found on Cu(110). Both structures were stable in the double-layer potential region. At anodic potentials, Cu₂S was formed on both surfaces. On Cu(100), patches of islands with Cu₂S(100) surfaces were observed. On Cu(110), the surface was highly roughened as a result of the formation of Cu₂S.

The oxidation mechanism of TiCl₃ as a reductant for an electroless deposition process was studied by ab initio molecular orbital method. The reaction process of TiCl₃ proceeds with the substitution of Cl⁻ to OH⁻. Net charge and spin density of the reactant, product, and intermediates were evaluated. It was suggested that the electron emission of TiCl₃, which is originated by the oxidation of Ti(III) to Ti(IV), took place when Cl is replaced by OH⁻ to form Ti(OH)₄. The catalytic activity of the metal surface, which is one of the most important factors for the electroless deposition process, was studied using a Pd₄ cluster as a model surface. It was suggested that the Pd₄ cluster enhanced the reaction of TiCl₃ to emit the electron. The effect of solvation is also taken into account in terms of the dielectric field constant. It was indicated that the heat of oxidation reaction shifted to an exothermic reaction with decreasing dielectric constant, indicating that the reaction preferentially proceeds in the vicinity of solid/liquid interface. However, it was indicated that the reaction could proceed in the bulk solution, suggesting that appropriate stabilization such as formation of complex is required for the application of the TiCl₃ to the electroless deposition process.

The chemical etching behaviors of undoped GaAs (100) in tartaric acid (C₄H₆O₆) and hydrogen peroxide (H₂O₂) aqueous solutions is investigated for the fabrication of nano-structures applied for opt-electronic and photonic devices. The role of the constituents of the etching solution (H₂O₂ and C₄H₆O₆) is reported clearly. The etching rate of GaAs increases with increased concentration of H₂O₂, and the cross-sectional etching profile changes from a non-isotropic to an isotropic shape as the H₂O₂ concentration decreases. X-ray photoelectron spectroscopy studies clarify that the H₂O₂ oxidizes the GaAs surface, and C₄H₆O₆ removes the oxide layers. Photoelectron peaks attributed to arsenic oxides are obtained from the surface of a GaAs specimen chemically etched in a C₄H₆O₆ + H₂O₂ aqueous solution. It seems that successive oxidation and dissolution of GaAs are performed during chemical etching in C₄H₆O₆ + H₂O₂, and gallium oxide may preferably dissolve into the solution.