Anchoring single-atom iron sites onto carbon spheres for boosting electrochemical sensing of bisphenol A

Bisphenol A (BPA), a common endocrine-disrupting chemical, poses serious threats to both ecological systems and human health even at trace concentrations. However, the accurate detection of BPA in complex matrices remains challenging due to the low sensitivity and poor selectivity of conventional electrochemical sensing platforms. The saturated N₄-coordinated single-atom sites derived from metal phthalocyanines exhibit high catalytic specificity and atomic utilization efficiency, enabling selective recognition of BPA. These characteristics enhance adsorption and electron transfer processes, potentially overcoming the limitations of traditional sensing materials and offering a feasible route for the ultra-sensitive detection of trace BPA in complex environments. In this study, we have developed a highly efficient electrochemical sensor for BPA by anchoring saturated N₄-coordinated single-atom sites of metal phthalocyanine onto carbon spheres (MPc/CSs, where M = Fe, Co, and Ni). The carbon spheres (CSs) serve as substrates to support the metal phthalocyanine molecules, improving the stability of the active sites and preventing aggregation. Among the materials tested, FePc/CSs exhibited the highest sensitivity (0.53 μA μM^-1) and the lowest limit of detection (0.031 μM), exhibiting better performance than other modified electrodes, including CoPc/CSs, NiPc/CSs, and metal-free phthalocyanine-loaded CSs (H₂Pc/CSs). Structural analysis revealed that the Fe-N₄ single-atom sites possess higher charge density than the Co-N₄ and Ni-N₄ single-atom sites, resulting in their superior catalytic activity. Practical validation of the FePc/CSs modified glassy carbon electrode (GCE) in real samples, such as supermarket receipts and plastic products, yielded satisfactory recovery rates (97.5-103.4 %), confirming the sensor's reliability in complex matrices. These results demonstrate that electrodes based on CSs-supported single-atom iron sites can serve as highly sensitive, selective, and cost-effective electrochemical sensors for BPA. Overall, this work provides an efficient strategy for designing high-performance environmental sensors based on engineered electronic microenvironments and offers valuable insights for the sensitive analysis of environmental pollutants.