NiWO₄/reduced graphene oxide modified electrode for ultra-sensitive nanomolar detection of Cu(II) and Hg(II) in environmental samples

Abstract

Heavy metals like Cu(II) and Hg(II) are poisonous, persistent, and may accumulate in living things, making their detection essential. They provide significant dangers to human health and the environment, even at low concentrations. Pollution control, public safety, and environmental monitoring all depend on sensitive and trustworthy detection techniques. A NiWO₄/RGO nanocomposite has been produced utilizing a simple reflux method by integrating nickel tungsten oxide (NiWO₄) nanoparticles with reduced graphene oxide (RGO). This composite was applied for modifying a glassy carbon electrode (GCE), resulting in a NiWO₄/RGO@GCE sensor capable of simultaneously detecting Cu(II) and Hg(II) ions in environmental samples. Characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X - ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD) and Raman spectroscopy confirmed the successful formation of the nanocomposite. Electrochemical studies using cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) demonstrated high sensitivity, selectivity, and reproducibility. The sensor showed an enormous linear range(1–20 ppb) and extremely low detection limits: 0.142 ppb for Cu(II) and 0.120 ppb for Hg(II). Real sample analysis showed excellent recovery rates ranging from 97.8 % to 102.0 %, indicating strong practical applicability. This work presents a cost-effective and reliable electrochemical platform for trace heavy metal detection, with promising potential for environmental monitoring applications.