A colorimetric smartphone-based platform for pesticides detection using Fe-N/C single-atom nanozyme as oxidase mimetics

In this study, a novel highly sensitive colorimetric platform has been designed for malathion assay based on FeN/C SAzyme. The as-synthesized SAzyme can directly oxidize 3,3,' 5,5 '-tetramethylbenzidine (TMB) to generate blue colored oxidized TMB. L-ascorbic acid-2-phosphate (AA2P), a substrate of acid phosphatase (ACP), could be hydrolyzed to AA, thereafter inhibit the oxidization reaction of TMB, leading to a conspicuous blue color fading. With the addition of malathion hindered the ACP activity and limited the AA production, resulting in the recovery of the catalytic activity of single-atom nanozyme. Under optimized operational conditions, a novel colorimetric assay has been designed for malathion detection with LOD of 0.42 nM. Besides, quantification of malathion in environmental and food samples was achieved based on the proposed strategy. In addition, the successfully integrated paper/smartphone sensor provided sensitive, and rapid, reliable detection of malathion with a LOD of 1 nM.

Automated summary

In this study, a novel highly sensitive colorimetric platform based on FeN/C SAzyme was designed for malathion assay. The synthesized SAzyme could directly oxidize 3,3,' 5,5 '-tetramethylbenzidine (TMB) to generate oxidized TMB, which exhibited a blue color. The addition of malathion hindered the ACP activity and restored the catalytic activity of single-atom nanozyme, enabling the quantitative detection of malathion.