A smartphone-integrated colorimetric sensor for sensitive detection of organophosphorus pesticides based on large-scale synthesized Fe-N/C single-atom nanozymes

Single-atom nanozymes (SAzymes) have been wildly used to design high-performance biosensors for the quantification of organophosphorus pesticides (OPs) recently. However, the low yield and low metal loading of SAzymes often limit their practical use in biosensing field. Herein, a large-scale synthesis (6.60 g) of Fe-N /C SAzymes (Fe loading of 3.9 wt%) was achieved by using carbon black as a template. This prepared Fe-N/C SAzymes exhibit efficient oxidase-like activity that could catalyze the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) along with color variation. On this basis of Fe-N/C SAzymes, a colorimetric biosensor was designed for OPs detection. Then a smartphone combined with RGB analysis was used to digitize the color information. The B/ (R + G) value shows good linear detection range (1–100 nM) and low detection limit (0.4177 nM). More importantly, the large-scale synthetic approach and excellent catalytic performance of Fe-N/C SAzymes are significant for promoting the marketability of biosensors.