• Green synthesis of Bi₂O₃@PC using bismuth nitrate as a precursor and template. • Bi₂O₃@PC/GPE exhibits high Hg²⁺ sensitivity (0.101 µA cm⁻² µM⁻¹) and 84 nM detection limit. • Sensor retains 89.6% signal after 30 days; RSD of 1.19% confirms repeatability. • Excellent selectivity and ∼99% Hg²⁺ recovery in unprocessed canal water samples. • A low-cost, eco-friendly platform for heavy metal sensing in surface waters. Mercury (Hg²⁺) contamination remains a critical environmental and public health concern due to its toxicity, mobility, and bioaccumulation potential in aquatic systems. In this study, we present a green and cost-effective strategy to fabricate bismuth oxide-embedded porous carbon (Bi₂O₃@PC) composite electrodes for the selective electrochemical detection of Hg²⁺. The synthesis employs bismuth nitrate as a dual-function precursor and template, thermally decomposed within a glucose-derived carbon matrix, eliminating the use of corrosive acids or hazardous templating agents. Structural characterization confirms the formation of porous composites with tunable crystallinity, while electrochemical analysis reveals enhanced electron transfer kinetics and electroactive surface enrichment, particularly for the Z04 variant. The Bi₂O₃@PC/GPE sensor achieves a low detection limit (98 nM), high sensitivity (0.101 µA µM⁻¹), and excellent linearity (R² = 0.996), alongside strong selectivity against competing ions (Cd²⁺, Pb²⁺, Zn²⁺), robust repeatability (RSD = 1.19%), and durable stability (∼89.6% signal retention over 30 days). Real-sample analysis in canal water yields recovery rates of 99.12 ± 3.45%, highlighting the platform's practical applicability. Importantly, the use of low-cost reagents, recycled polystyrene, and graphite pencil electrodes for device fabrication enables the production of multiple sensors from a single batch, reducing material costs by over 90% relative to noble-metal or multistep systems. These results highlight the Bi₂O₃@PC sensor as a scalable, sustainable, and high-performance solution for decentralized monitoring of mercury in complex environmental settings.
Mushtaq et al. (2026) studied this question.