A Nanostructured Electrode for Photoelectrochemical Detection of Hydrogen Peroxide

Abstract

Hydrogen peroxide (H2O2) acts as a critical second messenger in fundamental biological processes, which makes it a highly important target for direct detection in biological systems. Among various read-out techniques, photoelectrochemical (PEC) sensing offers a low limit of detection and high sensitivity. Here, a promising, non-enzymatic, sunlight-driven, simple photoelectrochemical (PEC) sensor for H2O2 detection is presented. The electrode is based on a Si wafer, a thick ZnO spacer, a thin Au layer and a graphene layer on top. The fabrication was done through conventional e-beam evaporation deposition technique for the spacer and metal film. An additional layer of graphene was drop-casted on top. The latter provides highly conductive scaffolds to ease electron transport and to increase the electrode sensitivity. The morphological characteristics and optical properties were investigated via FESEM and UV-Vis spectroscopy, respectively. Additionally, the electrochemical characterization was conducted using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. Direct detection of H2O2 was studied via chronoamperometry method under simulated sunlight by using a three-electrode configuration in which stainless-steel served as both counter and reference electrodes and the fabricated electrode as the working electrode. The photo responses to gold and gold/graphene electrodes in a non-enzymatic and biocompatible PBS environment with a pH 7.2 were thoroughly investigated. The gold-graphene demonstrates boosted properties combining excellent photoelectroactivity and high sensitivity towards H2O2 with a superb limit of detection of 1pM in a linear range of 1pM-100mM. Keywords: Hydrogen peroxide, gold, graphene, photoelectrochemical sensor