MOF-based Ag NPs/Co3O4 nanozyme for colorimetric detection of thiophanate-methyl based on analyte-enhanced sensing mechanism

Silver nanoparticles supported on metal–organic framework (ZIF-67)-derived Co 3 O 4 nanostructures (Ag NPs/Co 3 O 4 ) were synthesized via a facile in situ reduction strategy. The resulting materials exhibited pH-switchable peroxidase/catalase-like catalytic activity. Ag NP doping greatly enhanced the catalytic activity of Ag NPs/Co 3 O 4 towards 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation and H 2 O 2 decomposition which were 59 times (A 652 of oxTMB) and 3 times (A 240 of H 2 O 2 ) higher than that of ZIF-67, respectively. Excitingly, thiophanate-methyl (TM) further enhanced the peroxidase-like activity of Ag NPs/Co 3 O 4 nanozyme due to the formation of Ag(I) species in TM-Ag NPs/Co 3 O 4 and generation of more radicals resulting from strong interaction between Ag NPs and TM. The TM-Ag NPs/Co 3 O 4 nanozyme exhibited lower K m and higher V max values towards H 2 O 2 when compared with Ag NPs/Co 3 O 4 nanozyme. A simple, bioelement-free colorimetric TM detection method based on Ag NPs/Co 3 O 4 nanozyme via analyte-enhanced sensing strategy was successfully established with high sensitivity and selectivity. Our study demonstrated that hybrid noble metal NPs/MOF-based nanozyme can be a class of promising artificial nanozyme in environmental and food safety applications. Graphical Abstract