Enhanced Electrochemical and Physical Properties of Ag/AgCl Planar Reference Electrodesin Potentiometric Sensors by Graphite Oxide Layer

The most common reference electrode (RE) which is used in electrochemical measurements is the Ag/AgCl electrode. In this study, we present a novel solid-state Ag/AgCl planar electrode that was coated with a thin layer of Graphite Oxide (GO) as a protective layer. The Ag/AgCl planar electrode was fabricated by using the photolithography and lift-off method combined with the Ag[NH3]2Cl complex. The GO was produced by Hummer’s method and was deposited on top of the Ag/AgCl layer by drop-casting method. The layers of the fabricated reference electrode were characterized by micro Raman spectroscopy, Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The responding time of the planar electrode was short and the signal was more stable in comparison to the plainAg/AgCl electrode. The Open Circuit Potential (OCP) measurement with the fabricated electrode as the RE and the platinum electrode as the working electrode in electrolyte solutions which had various pH values was performed with a linear response in pH ranges from pH 5 to pH 8 and the linear correlation coefficient (R^2 = 0.9899). Moreover, the coating of the GO layers also enhanced the durability of the modified electrode. The results showed that the modified Ag/AgCl electrode with a thin layer GO as the protective layer could be used as plana REs for the potentiometric sensors.