Polyaniline/poly(acrylic acid) composite film: A promising material for enzyme-aided electrochemical sensors

Abstract

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of various concentrations of PAA. The conductivity of the composite films (PANI/PAA films) was determined by in-situ measurement in a phosphate buffer solution of pH 7.0 and corroborated by electrochemical impedance spectroscopy. In the range of PAA content up to 18.2 %, the conductivity of the PANI/PAA film was found to increase significantly with increasing PAA content, owing to enhanced protonation of nitrogen atoms of PANI. Glucose oxidase (GOx) was immobilized on the PANI/PAA films by the condensation reaction with the carboxyl groups of PAA on their surfaces. Amperometric sensing was carried out for glucose by use of the GOx-immobilized PANI/PAA film as an enzyme electrode. The GOx-immobilized film gave the current response to glucose depending on its concentration. Although the current response leveled off to reach a constant value in a high glucose concentration range, the value was found to increase with increasing PAA content in the PANI/PAA film used, corresponding to the increased conductivity of the film.