Nobuyoshi Baba

Small quantum‐sized CdS particles assembled to form a regularly nanostructured porous film

Submicroporous CdS films were fabricated by a two‐step replication process, in which porous anodic alumina was used as a template. The films were grown on a porous gold support of the same structure, resulting in a free‐standing CdS/Au membrane. The diameter of the holes of the regular porous structure is in the order of 100 nm. Moreover, the replicated CdS film consists of small‐sized quantized crystalline particles, the size of which are in the range of 5 nm. Thus, the film is ordered in the 5 and 100 nm domain forming a superstructure.

Fabrication of Porous TiO2 Films Using Two-Step Replication of Microstructure of Anodic Alumina

Microporous TiO2 films were fabricated using a two-step replicating process, in which porous anodic alumina was used as a template. The TiO2 films prepared from a TiO2 sol solution had straight micropores of high aspect ratio, and the distribution of the pore diameter was very sharp. Change due to postheating treatment of as-prepared TiO2 films was examined by electron diffraction analysis and scanning electron microscopic observation.

Nature of the carboxylate species incorporated in anodic alumina films formed in oxalic acid solution

Abstract Electron spin resonance (ESR) and IR spectroscopy, combined with a chemical sectioning technique supported by transmission electron microscopy, were employed to study the nature of oxalate species incorporated into porous anodic films formed on aluminium in an aqueous solution of oxalic acid. ESR spectroscopy combined with chemical sectioning of the oxides indicated that spin centres, which are supposed to be due to the cleavage of the chemical bonds of oxalate species, are present predominantly in the outer region of the cell walls of the oxide. No spin centres, however, were detected in the inner region nearest to the cell boundary, although a small amount of carboxylate species was still detected in that region. In addition, IR spectroscopy of the oxide, chemically sectioned for various periods, showed that the incorporated species are present in the oxide as carboxylate ions but their structures showed marked variation as a function of depth from the surface of the cell wall of the oxide. These results suggest strongly that oxylate anions incorporated into a barrier layer of the oxide are unstable and undergo decomposition in the high electric field present within the layer during anodization.

Electrochromic Properties of V2O5 Thin Films Colloid-Chemically Deposited onto ITO Glasses

The dynamic properties of a V2O5 ECD cell prepared by the sol-get method are mentioned. The V2O5 thin film was electrochemically deposited onto ITO glass from a poly-vanadic acid sol. The response time of the ECD cell was 2–20 seconds, depending upon the cell voltage. The repeating time was more than 8×104 times. It is possible to fabricate large-area ECD cells by this method.

Fabrication of a one-dimensional microhole array by anodic oxidation of aluminum

A one‐dimensional microhole array with high‐aspect ratio was successfully obtained using anodic oxidation of an aluminum oxide/aluminum/glass structure. This process allows the fabrication of an array of microholes less than 1000 A diameter without any exposure mask or resist, and the size of the array can be controlled on the basis of the relationship between the thickness of the aluminum layer and anodizing voltage.

CHARACTERIZATION AND PROPERTIES OF ELECTROCHROMIC COBALT OXIDE THIN FILM PREPARED BY ELECTRODEPOSITION

Abstract Electrochromic, anodically and cathodically deposited films were prepared by electrodeposition from Co(NO3)2 solution onto ITO glass substrate. Anodically deposited films consisted of cobalt oxide and cathodically deposited films consisted of α-Co(OH)2, β-Co(OH)2 and CoO which had been originated from the redox reaction of OH− ions existing in the electrolyte. Furthermore, H2O penetrates into the anodically deposited film during the redox reaction. In the case of the cathodically deposited film, Co(OH)2 is present at the reduction state, whereas at the oxidation state, the film composition changes to a mixture of Co(OH)2 and CoO.

Formation of Nickel Oxyhydroxide Thin Films by Electrodepositon and Their Electrochromic Characteristics

Electrochromic nickel oxyhydroxide films were formed by an electrodeposition method from 0.005 M NiSO4+0.015 M (NH4)SO4 solution, and their memory characteristics, response time and operation lifetime were investigated. The films prepared were porous with a network structure. They were colorless and transparent in a lower oxidation state [Ni(OH)2], but were dark brown in a higher oxidation state [NiOOH]. By heat-treating the films at 250degC for 15 minutes, electrochromic characteristics such as the operation lifetime could be remarkable improved.

Fabrication of Pt microporous electrodes from anodic porous alumina and immobilization of GOD into their micropores

It has been reported that porous alumina films obtained by anodic oxidation of aluminum can be employed for functional electrodes of which the surface geometry is regulated at dimensions ranging from submicron to nanometer scale [l-7]. Anodic porous alumina films have several unique properties characterized by their microporous structure, that is, excellent uniformity in diameter and interval of micropores, and their ideally cylindrical shape. However, when the anodic alumina films are adopted for electrode materials, several disadvantageous points of the films, such as chemical instability in aqueous solutions, insufficiency of mechanical strength, and nonconductivity, lead to serious problems [S]. We have reported in previous articles that microporous membranes which have an identical geometrical structure with the anodic porous alumina can be fabricated with Au, Ni or TiO, [g-12], by means of a two-step replication method. In this method, fabrication of a negative-type structure of the anodic porous alumina and subsequent formation of a positive-type structure resulted in a membrane having an identical structure with anodic porous alumina. In the present report, we applied the two-step replication method to the preparation of a microporous Pt membrane, which has been widely used as an electrode material. The surface area of the Pt microporous electrode was evaluated by proton adsorption reaction in an acidic electrolyte. In addition to this, a preliminary result concering the immobilization of the enzyme, which plays an important role in biosensor technology, was shown. Immobilization of glucose oxidase (GOD) into the micropores of anodic porous alumina has been investigated by Majda et al. [2]. However, for the practical applications of the enzyme-immobilized electrode to high performance sensor systems, conductive porous electrodes with large surface area are required. For this purpose, platinized platinum has been used as

Photoluminescence of Anodic Oxide Films on Aluminium

A wide variety of anodic oxide films were investigated from the photoluminescent point of view. It was found that the phenomenon of photoluminescence appears only on the films anodically formed in organic acids instead of inorganic acids. In particular, thick oxalic acid films formed in low electrolyte concentration, with high current densities on high purity aluminium, gave intense photoluminescence. The luminescent centres were presumed to be the carboxylate ions which had been incorporated in the films during anodisation.

Electrochromic IrOx thin films formed in sulfatoiridate (III,IV) complex solution by periodic reverse current electrolysis (PRIROF)

Electrochromic thin films of iridium oxide have been obtained by alternative anodic and cathodic polarization of the electroconducting glass (NESA) in a sulfatoiridate complex solution. On both electrodes a transparent, dark-blue deposition was observed. According to the current waveform, it is suggested that the repeated anodic and cathodic polarization acts as coloring and bleaching processes of the electrochemically growing deposit, the electrochromic oxide film gradually thickening on the NESA. The deposits are very adhesive to the substrate NESA. This method offers a simple and economical process for manufacturing iridium oxide films on NESA glasses compared with the already reported method.