Enzyme sensors prepared by electrodeposition on platinized platinum electrodes

Abstract

Platinized Pt (platinum black) electrodes were employed as a base electrode for the immobilization of glucose oxidase (GOD). The GOD sensors were prepared by first electrodeposition of GOD/ BSA(bovine serum albumin) mixture on platinized Pt and subsequent cross-linking with glutaraldehyde. The roughness factor and morphology of the platinized Pt surfaces significantly depended on the platinization potential between 0.0 and −0.25 V (vs. sat. Ag/AgCl). At more positive potentials, small Pt crystallites were uniformly deposited to give a flatter layer, while dendritic crystallites were prominent at the other extreme resulting in higher roughness factors. A preferred exposition of Pt(110) planes was also observed on the dendritic crystallite surfaces, onto which the protein molecules deposited with a faster rate than onto the Pt(100) planes. The current intensities to glucose of the resulting GOD sensors gradually increased as the plating potentials for the base electrodes were more negative, which was accounted for from the fact that larger amounts of the protein molecules deposited on those highly roughened and preferentially Pt(110)-exposed Pt black surfaces. In addition, the highly roughened Pt black electrodes gave rise to a better signal to noise ratio in the current signals of the resulting sensors. It is likely that the plantinization process imparts a higher hydrophilic character on the Pt black surfaces such that adhesion of oxygen bubbles is greatly suppressed.