Sensitive and selective colorimetric detection of thiophanate-methyl based on a novel Ru-FeO nanozyme with enhanced peroxidase-like activity.

A novel Ru-FeO nanozyme with enhanced peroxidase-like (POD-like) activity was synthesized through a hydrothermal method. Ru-FeO nanozyme was effectively utilized for the detection of thiophanate-methyl (TM) using a colorimetric technique. The POD-like activity of Ru-FeO was found to be superior compared to FeO, Rh-FeO, and Pd-FeO. Ru-FeO provided excellent POD-like activity with Michaelis constants of 0.00645 mM and 0.66714 mM for substrates of 3,3',5,5'-tetramethylbenzidine and HO, respectively. The density functional theory calculation showed that Ru-FeO had better HO decomposition reactivity compared to FeO. Compared with FeO, the adsorbed HO molecules underwent decomposition more readily on the Ru-FeO catalytic surface facilitating the occurrence of the HO catalytic reaction, further suggesting the excellent POD-like activity of Ru-FeO. The coordination and electrostatic interactions of Ru-FeO and TM promoted their binding, contributing to TM covering Ru-FeO catalytic site and inhibiting the POD-like activity of Ru-FeO. As a result, the sensitive and selective detection of TM using Ru-FeO by a colorimetric method was achieved. The Ru-FeO nanozyme displayed a good linear correlation, with a linear detection range and a detection limit of 0.1-100 and 0.03 μg/mL, respectively. The Ru-FeO nanozyme was used for the determination of TM in soil and water samples with success.