Heteroatom-regulated iron single-atom nanozymes for universal colorimetric discrimination of mycotoxins and metal ions

Single-atom nanozymes (SAzymes) have garnered considerable attentions in biosensing due to their superior catalytic properties. Although significant progress has been made in this field, designing SAzymes with satisfactory catalytic performance and constructing high-throughput sensor platforms remains a major challenge. Herein, we design and fabricate an iron single-atom catalyst with the optimal Fe-N3PS active moiety supported on N, P, S co-doped hollow carbon nanocage (Fe-N3PS/HC). As expected, the prepared Fe-N3PS/HC SAzyme shows outstanding peroxidase-like activity and kinetics. Moreover, the density-functional theory (DFT) calculations reveal that the doped P and S atoms endow Fe moiety with unique electronic structure due to the regulation of atomic configuration, and thus improve the peroxide-like activity of Fe-N3PS/HC SAzyme kinetically and thermodynamically. A three-channel nanozyme sensor array combing Fe-N3PS/HC SAzyme and three colorimetric reactions is established for colorimetric discrimination of mycotoxins and metal ions. Different analytes have varying interactions with Fe-N3PS/HC and diverse degrees of catalytic oxidation abilities, thus resulting in fingerprint-like colorimetric response for the analytes. The statistical analysis results show that the sensor array displays excellent discrimination ability for five mycotoxins and ten metal ions, and perform well in quantitative determination at the level of ng/mL and mu M. Additionally, the sensor array allows precise identification even in multicomponent mixtures and real samples (e.g., corn juice and actual water sample), demonstrating its potential in the applications of food safety and environment monitoring.