Electrochemical Sensing of Arsenic Using Physically Vapor Deposited Au Nanofilm Electrodes: Flow Cell Configuration

Abstract

There is a current need for an inline arsenic sensing system that can continuously sample aquifer water quality for well drilling and ground water monitoring applications. Concentrations of arsenic oxyanions above 10 μg/L in drinking water are considered dangerous by the World Health Organization [1]. Levels above this in daily consumption can lead to renal toxicity and a condition known as Arsenicosis, which produces lesions on the skin. We are currently developing an Au thin film, As stripping voltammetry flow cell sensing to meet this challenging need. Our findings show that use of gold (Au) nanofilm electrodes physically vapor deposited (PVD) onto porous carbon papers can detect concentrations below 10 μg/L of arsenite, As (III), in water. The nanofilms were characterized by SEM, X-ray diffraction and with X-ray fluorescence with a measured loading of approximately 13 μg of Au per 1 cm2 of carbon paper in each electrode. The PVD method increases the manufacturability of aqueous arsenic sensors because it is facile, scalable, and uses much less Au than screen printing methods. Linear stripping voltammetry (LSV) was used in a three-electrode configuration to create a calibration curve for standard additions of 5, 10, 25, 50 and 75 μg/L As (III). The resulting plot of peak area versus concentration resulted in a linear correlation. The capacitance of PVD deposited Au nano films was significantly less than that of Au nanoparticles on XC72 carbon, produced via solution precipitation methods. The lower capacitance enables the detection of low concentrations of As without the need for the application of more complex pulse voltammetry methods.