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

Abstract

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