Voltammetric Detection of Cd2+, Pb2+, and Hg2+, Using Bio-Matter Mediated Nanocomposite Modified Screen-Printed Carbon Electrode

Abstract

The use of bio matter in the synthesis of NPs is increasingly becoming popular in nanotechnology. In this work, orange (Citrus X sinensis) peels’ extract was used in a simple synthesis of Cu2O/ZnO metallic bioxide NPs. The as-prepared bi-oxide NPs were characterized with UV-Vis, SEM, TEM, XRD and Zeta potentials and physically blended with intrinsically conductive PANI polymer. The mixture was used to treat the surface of a screen-printed carbon electrode (SPCE) through drop dry strategy. The modified electrode was characterized using cyclic voltammetry (CV) in 10 mM (Fe(CN)6)3−probe containing 0.1 M KCl, and 0.1 M HCl electrolyte mediums, and electrochemical impedance spectroscopy (EIS) in the same electrolyte. The modified electrode showed enhanced redox current response in the electrolyte and reduced the charge transfer resistance (Rct) in HCl medium from 175 kΩ at the bare SPCE to 65 kΩ (equivalent of 62.8%). Using square wave voltammetry (SWV), 0.1 M HCl electrolyte, 180 s deposition time, -1.2 V deposition potential, potential step of 4 mV, frequency of 8 Hz, and pulse amplitude of 28 mV, the limits of detection (LoD) of Cd2+, Pb2+, and Hg2+ at the fabricated electrode were evaluated. Peak stripping currents varied linearly with analyte concentration from 31.16 -274.98 µg/L, 0-1334.74 µg/L, and 32.58-328.82 µg/L for Cd2+, Pb2+, and Hg2+. The LoD computed for Cd2+, Pb2+, and Hg2+ were 1.08 ppb, 2.79 ppb and 2.72 ppb respectively. The sensitivities of the electrode for the electrolytes were 26.19 µA/µM, 3.46 µA/µM, and 108.12 µA/µM respectively. The relative standard deviation (RSD) derived from a single disposable SPC electrode at a small amount of the Cd2+, Pb2+ and Hg2+ analytes was 6.50 %, 0.98 % and 4.44 % respectively. The fabricated sensor was eventually deployed for real sample analysis of Pb2+. The result was satisfactory, with a total recovery rate of 96.70%. The electrode also demonstrated capacity to detect simultaneously the three analytes (Figure 1). Figure 1