Highly selective and sensitive colorimetric detection of nicosulfuron based on Cu-MOF nanozyme

A copper metal-organic framework composite nanozyme (Cu-MOF) with peroxidase-like activity was prepared using an improved room temperature method. Cu-MOF can catalyze H₂O₂ to release (•OH), thereby oxidizing the colorless chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxidized product (oxTMB), which has a maximum UV absorption peak at 652 nm. Nicosulfuron can regulate the electronic balance of the redox pair (Cu²⁺/Cu⁺) on the Cu-MOF surface, thereby enhancing its peroxidase activity and promoting the deepening of the TMB blue color. Based on this principle, a colorimetric detection method for nicosulfuron was established. The linear range of this method is 0.2-10 μg/mL^-1, and the detection limit is 0.02 mg/kg. This method has been applied for the detection of nicosulfuronin corn samples, with recovery rate ranging from 90.88% to 117.33%, and all relative standard deviation being less than 4%.