Orange Peel-Assisted GO/rGO Blended to Functionalize Ag Nanoparticles: A Sensing Probe for Organo-Hg²⁺ Ions in...

Heavy metals such as Hg²⁺, Pb²⁺, and Cd²⁺ are among the most hazardous environmental pollutants due to their high toxicity and tendency to bioaccumulate in living organisms. Mercury, particularly in the form of alkylated mercury, poses a serious public health concern owing to its accumulation in fish and other aquatic life, which subsequently enters the human food chain. There are different fish species across Asia, such as Catla, Rui, Aar, Bhetki, and Tilapia, that have been reported to bioaccumulate these toxic metals in their tissues. In this study, we present a green-synthesized nanohybrid, C-Ag NPs@rGO, as an efficient sensing platform for the detection of Hg²⁺ ions and the detection of mercury in fish serum samples. The nanocomposite's high surface area and abundant active sites facilitate enhanced interactions with target analytes, making it highly effective for sensing applications. Although numerous Hg²⁺ sensors have been reported, many still face challenges related to insufficient sensitivity and relatively high detection limits. In contrast, our C-Ag NPs@rGO sensor demonstrates excellent selectivity, pH-dependent fluorescence sensing capabilities, and excellent electrochemical sensing ability. Notably, under near-physiological pH conditions, the sensor achieved a remarkably low limit of detection (LOD) of 6.64 × 10^-3 nM, 34.2 × 10^-3 nM for Hg²⁺ through fluorescence measurement, and an LOD value of 0.032 nM through cyclic voltammetry measurement, substantially lower than most of the reported values. This eco-friendly sensing platform offers a promising approach for the detection of trace levels of mercury in both biological and environmental samples.