Electrografting and Surface Properties of Some Substituted Nitrophenols on Glassy Carbon Electrode and Simultaneous Pb2+ - Cd2+ Analysis via Assist of Graphene Oxide Terminated Surface

Abstract

A new electrode was prepared by the electrooxidation of orto-, meta-, and para-substituted nitro phenols on glassy carbon electrode. Electrochemical modification of the electrodes was carried out in 0.01 M HCl using cyclic voltammetry (CV). Then nitro groups in the covalently grafted nitro phenol derivatives on GC electrode were reduced to amine groups in 0.01 M HCl. The electrochemical behavior of the modified electrodes was studied in the presence of electroactive redox probes such as ferrocene and ferricyanide by CV and electrochemical impedance spectroscopy (EIS). X-ray photoelectron spectroscopy (XPS) was employed to characterize the surface structure and composition of the modified substrates. Thickness of the films was measured by using an ellipsometer. Surface topography of the nanofilms and bare GC was characterized via AFM. Graphene oxide (GO) was covalently attached on 4-aminophenyl involved surface through EDC. Simple immersing of the GO covered nanoplatform into a sample solution led to the chemical deposition by means of the interaction with Cd2+ and Pb2+ ions, simultaneously. Various analysis parameters that affect the simultaneous analysis of the ions such as deposition time, pH factor and deposition temperature, were optimized. Calibration curve for the GO grafted electrode surface with Square-wave anodic stripping voltammetry (SWASV) were obtained in the concentration range between 1 × 10−8 M and 1 × 10−12 M for Pb2+ and Cd2+. The detection limits of the modified electrode for Pb2+ and Cd2+ ions were determined to be about 3.2 (± 0.1) × 10−13 M and 2.4 (± 0.2) × 10−13 M, respectively.