Fabrication of highly ordered nanoporous thin Au films and their application for electrochemical determination of epinephrine

The anodic oxidation of epinephrine (EP) on Au electrodes with a large surface area was studied in phosphate buffer solution (pH 7). The nanoporous thin Au films deposited over the surface of a highly ordered anodic aluminum oxide (AAO) served as sensitive electrodes for a simple and fast electrochemical determination of epinephrine. The electrochemical characterization of the obtained electrodes was carried out by cyclic voltammetry (CV) and chronoamperometry. The results revealed that oxidation processes of EP are controlled by diffusion. The transfer coefficient (alpha = 0.52), total number of electrons involved in the first step of EP oxidation (n = 1), and the diffusion coefficient of EP in the 0.1 M phosphate buffer solution (D = 3.4156 x 10(-5) cm(2) s(-1)) were calculated. The proposed ordered nanoporous Au electrodes exhibited a high electrocatalytic activity for oxidation of EP. The average catalytic rate constant was found to be 1.027 x 10(6) M-1 s(-1). The cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) studies showed that catalytic peak current was linearly dependent on the EP concentration. The linear response was observed over the EP concentration range of 25-500 mu M for LSV, 20-100 mu M for DPV and 25-600 mu M for chronoamperometry. However, the DPV method exhibited the highest sensitivity (1.13 mA cm(-2) mM(-1)) and the lowest detection limit (2.42 x 10(-6) M). (C) 2015 Elsevier B.V. All rights reserved.