Rational design of PtBi nanoalloy-embedded nitrogen-doped porous carbon nanosphere for ultrasensitive electrochemical detection of Cd2+ and Hg2+ in food samples

Rapid and accurate identification of heavy metals in food products is essential for ensuring food safety and public health. In this study, an electrochemical sensor based on nitrogen-doped hierarchical porous carbon nanospheres encapsulating ultrasmall PtBi nanoparticles (PtBi-HPCNs) was developed to enhance preconcentration and electrochemical deposition. The HPCNs provide abundant adsorption sites and effective mass transfer channels for metal ion enrichment, while the PtBi nanoalloys act as highly active electrocatalytic centers for metal ion reduction. Investigation of adsorption behavior and reduction kinetics reveals an “adsorption-assisted in-situ electrocatalytic reduction” mechanism. Leveraging these structural and electronic properties, the sensor enables sensitive and selective detection of Cd 2+ and Hg 2+ with low detection limits of 0.253 nM and 0.381 nM, respectively, well below Chinese regulatory limits. When applied to actual food sample detection, satisfactory recoveries of 96.80–104.53% were obtained, demonstrating its potential for practical monitoring of trace heavy metal ions in food.