Electrochemical Sensors for Monitoring Water Quality: Recent Advances in Graphene Quantum Dot-based Materials for the Detection of Toxic Heavy Metal Ions Cd(II), Pb(II) and Hg(II) with their Mechanistic Aspects

In this review, we discuss the current state of the art of electrochemical (EC) sensors based on graphene quantum dot (GQD)-based materials for the detection of heavy metal ions (HMIs), Cd(II), Pb(II), and Hg(II). The majority of the water sources are polluted with HMIs according to WHO, and UNEP. Because of its widespread nature and high toxicity even at very low concentrations and bio accumulative properties, it is imperative to monitor and measure the concentrations of the HMIs in water sources for a safe and healthy environment. Among other HMIs, Cd(II), Pb(II), and Hg(II) bagged much attention in the research field due to its high toxicity, environmental persistence, and significant health hazards, even at trace levels and hence they are listed in the top ten highly toxic species by WHO. Thus, the EC Sensing of Cd(II), Pb(II), and Hg(II) become more prevalent in water quality monitoring. Herein, we discuss the recent advances in GQD-based EC sensors for HMIs with focus on the sensors for Cd(II), Pb(II), and Hg(II). We have further conceptualized the mechanism involved in the EC sensing. In brief, this review, we started off by emphasizing the necessity of water quality monitoring, followed by the significance of employing EC sensing in water quality assessment and the available GQD sensors in the detection of Cd(II), Pb(II), and Hg(II). The review is concluded with a detailed and critical analysis of the mechanism involved in the EC sensing process and its future perspectives.