Iron-ferrocenedicarboxylic nanozyme based colorimetric and photothermal dual-modal signal catalytic inhibition for detection of glyphosate.

A novel dual-mode colorimetric and photothermal sensing platform for glyphosate (GLP) based on iron-ferrocenedicarboxylic metal-organic framework (Fe-FcMOF) nanozyme-mediated catalysis is presented. Specifically, the synthesized Fe-FcMOF nanozyme exhibits superior peroxidase (POD)-like activity, which can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (ox TMB) in the presence of H2O2. Due to the photothermal effect of oxTMB, the catalytic system composed of Fe-FcMOF, H2O2 and TMB exhibits remarkable temperature changes (ΔT) before and after being irradiated by near-infrared light at 808 nm. Subsequently, Fe-FcMOF reacts with GLP through electrostatic attraction, hydrogen bonding and specific chemical coordination between the -FeO of Fe-FcMOF and -PO3H2 of GLP, resulting in the formation of stable Fe-O-P coordination bonds. This specific interaction leads to the decrease of the POD-like activity of Fe-FcMOF and the ultraviolet absorbance and ΔT of the system. Building upon these findings, we develop a colorimetric and photothermal dual-modal sensor, with detection limits of 0.0676 µg mL-1 and 0.0856 µg mL-1 respectively. Notably, the proposed dual-mode sensing platform enhances the reliability of the assay, which offers a potential approach for the on-site visual detection of pesticide residues to guarantee food safety.