Controllable Synthesis of a Porous PEI-Functionalized Co3O4/rGO Nanocomposite as an Electrochemical Sensor for Simultaneous as Well as Individual Detection of Heavy Metal Ions

The present study focuses on the strategy of employing an electrochemical sensor with a porous polyethylenimine (PEI)-functionalized Co3O4/reduced graphene oxide (rGO) nanocomposite (NCP) to detect heavy metal ions (HMIs: Cd2+, Pb2+, Cu2+, and Hg2+). The porous PEI-functionalized Co3O4/rGO NCP (rGO·Co3O4·PEI) was prepared via a hydrothermal method. The synthesized NCP was based on a conducting polymer PEI, rGO, nanoribbons of Co3O4, and highly dispersed Co3O4 nanoparticles (NPs), which have shown excellent performance in the detection of HMIs. The as-prepared PEI-functionalized rGO·Co3O4·PEI NCP-modified electrode was used for the sensing/detection of HMIs by means of both square wave anodic stripping voltammetry (SWV) and differential normal pulse voltammetry (DNPV) methods for the first time. Both methods were employed for the simultaneous detection of HMIs, whereas SWV was employed for the individual analysis as well. The limits of detection (LOD; 3σ method) for Cd2+, Pb2+, Cu2+, and Hg2+ determined using the rGO·Co3O4·PEI NCP–modified electrode were 0.285, 1.132, 1.194, and 1.293 nM for SWV, respectively. Similarly, LODs of Cd2+, Pb2+, Cu2+, and Hg2+ were 1.069, 0.285, 2.398, and 1.115 nM, respectively, by DNPV during simultaneous analysis, whereas they were 0.484, 0.878, 0.462, and 0.477 nM, respectively, by SWV in individual analysis.