Electropolymerization of ortho-Phenylenediamine and its Use for Detection on Hydrogen Peroxide and Ascorbic Acid by Electrochemical Impedance Spectroscopy

摘要

Poly(ortho-Phenylenediamine) was deposited as a thin film by electrochemical impedancespectroscopy (EIS) and compared to cyclic voltammetry (CV) on Teflon insulated Platinum揑ridium(Pt) disk microelectrode (125 m diameter) in 300 mM phosphate buffer solution (pH 7.2). This studyfocuses on the electropolymerization process and electrical properties of PoPD-modifiedmicroelectrodes, using EIS technique. The estimated thickness of the PoPD film was 31 nm with conductivity of 1.1 x 10 Scm . The initial impedance plot shows a semicircle which characterizedthe charge-transfer resistance at the microelectrode/polymer interface at higher frequency and adiffusion process at lower frequency. Impedance data were fitted to the Randles and a modified2 2 Randles circuit models with = 0.12 and = 0.06 respectively. The capacitive behavior (phase angle= 83) of the bare Pt microelectrode was transformed to a resistive behavior (phase angle = 13) afterthe formation of PoPD layer at lower frequency. The modified electrode was applied as an analyticalprobe to detect of hydrogen peroxide (H2O2) and ascorbic acid (AA). The EIS technique also revealedthat the PoPD layer blocked the AA species, reflected in the higher impedance observed compared toH2O2.