Cobalt tuned copper sulfide on montmorillonite: Peroxidase-like activity, catalytic mechanism and colorimetric sensing of hydrogen peroxide

Series of Co-doped CuS-Montmorillonite (Co/CuS-MMT) nanocomposites with different mole ratio of Co2+ to Cu2+ have been prepared via a simple hydrothermal route. Co/CuS-MMT has been firstly demonstrated to possess an intrinsic peroxidase-like activity with the aid of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). The colorless TMB is rapidly oxidized into blue oxTMB by H2O2 only in 3 min, which is obviously distinguished by the naked eye. Among series of Co/CuS-MMT, 50Co/CuS-MMT (Co2+ doping is set to 50 atomic percentage (at%)) exhibited the highest peroxidase-like activity, in accordance with the typical Michaelis-Menten kinetics. The catalytic activity of Co/CuS-MMT is dependent on temperature, pH and the amount of Co2+, respectively. The excellent peroxidase-like performance is attributed to the (OH)-O-center dot generated in the process of catalytic reaction. Based on the peroxidase-like activity of 50Co/CuS-MMT, a fast colorimetric H2O2 sensing platform was constructed in a linear response range (10-100 mu M) with a relative low detection limit (2.2 mu M). This fast sensitive colorimetric sensor is conveniently applied to detect H2O2 residue in contact lens solution.