Balancing "on" and "off" response of hydroxyl groups to a nanozyme-catalyzing system for the construction of an ultra-sensitive and selective "signal-on" detection platform for dopamine.

Targeting the functional groups present in analytes by nanozyme-catalyzed systems is a promising strategy to construct sensitive and selective platforms for the sensing of specific analytes. Herein, various groups (-COOH, -CHO, -OH, and -NH) on benzene were introduced in an Fe-based nanozyme system with MoS-MIL-101(Fe) as the model peroxidase nanozyme, HO as the oxidizing agent, and TMB as the chromogenic substrate, and the effects of these groups at both a low concentration and high concentration were further investigated. It was found that the hydroxyl group-based substance catechol showed an "on" effect at a low concentration to increase the catalytic rate and enhance the absorbance signal, whereas an "off" effect at a high concentration with a decreased absorbance signal.