Thermodynamic and Charge Transport Studies for the Detection of Heavy Metal Ions in Electrochemical Sensors Using a Composite Film of Aniline, N-phenylglycine and Graphene Oxide

Abstract

The key performance parameters for an electrochemical aqueous ion sensor include the limit of detection (LOD) and the selectivity. Novel composite films were synthesized electrochemically from aniline, N-phenylglycine and graphene oxide(GO) to detect heavy metals by square wave voltammetry; and the LOD and interferences from several ions (As5+, Cr6+, Cu2+, Na+, Mg2+, Al3+, K+, Sr2+, Mn2+, Fe3+, Fe2+, Zn2+) for the detection of Cd2+ were characterized. The thermodynamic (chemisorption) analysis based on the adsorption isotherms and the charge transport analysis based on the barrier width technique were undertaken, and the −ΔGads and the barrier width values were utilized to help explain the improved performance parameters. Response surface analysis was undertaken to find the optimum condition (with respect to the film thickness and GO content) to obtain the optimum values of the LOD and interference, and the optimized film provided an LOD of 800 ppt for Cd2+ with improved tolerance to the interfering ions, especially for Cr6+. A comparative study was performed based on the electroactive surface area, LOD and interference effects with three other films (i) polyaniline (ii) poly (aniline-N-phenylglycine) (iii) and a composite from aniline and graphene oxide; and the novel film showed the best performance.