High Performance Mercury Sensing Enabled by the Synergistic Effect of rGO–MnO₂ Nanocomposites

Abstract

Access to safe and clean water remains a major global concern, largely due to contamination by toxic heavy metals. Among these contaminants, mercury exhibits extreme toxicity even at ultra-trace level concentrations, posing serious and long-lasting threats to both human health and the environment. To mitigate this issue, a highly selective and sensitive electrochemical sensor has been fabricated for Hg²⁺ ions detection at the trace level. The sensor is designed on a glassy carbon electrode (GCE), which has been modified with a nanocomposite composed of manganese dioxide (MnO₂) nanoparticles and reduced graphene oxide (rGO). Incorporation of the rGO and MnO₂ nanoparticles improves electrical conductivity, enlarges the electroactive surface area, and provides abundant adsorption sites for Hg²⁺ ions. MnO₂ serves as a redox-active component with strong affinity for mercury ions Hg²⁺, whereas rGO ensures efficient electron transfer. The combined effects of these materials result in a synergistic interface exhibiting excellent electrocatalytic activity, enabling ultrahigh sensitivity, broad detection capability, and a remarkably low detection limit of 0.097 nM—well below the World Health Organization’s permissible concentration for Hg²⁺ in drinking water. Furthermore, the developed sensor exhibits long-term operational stability, reproducibility, and repeatability, along with strong selectivity against common interfering ions such as Na⁺, K⁺, Fe³⁺, Zn²⁺, and Cu²⁺. Overall, the rGO–MnO₂ nanocomposite modified sensor offers a reliable, cost-effective, and efficient approach for real-time detection and monitoring of Hg²⁺ contamination in aqueous systems.