Copper-Sensitized “Turn On” Peroxidase-Like Activity of MMoO4 (M = Co, Ni) Flowers for Selective Detection of Aquatic Copper Ions

Improving the catalytic performance of nanozymes is currently one of the hot topics in the field of analytical chemistry. Metal ions can be an ideal way for the regulation of enzyme activity because of its unique advantages. Although great advances have been achieved, the efficiency and selectivity of nanozymes still has big room to improve. Herein, we found that the copper ions (Cu2+) could selectively and sensitively regulate the peroxidase-like activity of flower-like transition-metal-based material MMoO4 (M = Co, Ni). The peroxidase-like activity of MMoO4 could obviously be activated by Cu2+, which accelerated the effective oxidation of common chromogenic substrates represented by 3,3′,5,5′-tetramethylbenzidine. The catalytic activity of MMoO4–Cu2+ strongly relies on the reaction temperature and the pH of solution. Moreover, the kinetic behavior follows the Michaelis–Menten kinetics. Then, a simple, sensitive, and selective colorimetric strategy using CoMoO4 as the probe for detecting Cu2+ was established. The obvious color change can be discerned by the naked eye or detected by the absorption spectroscopic method. In the range of Cu2+ concentration of 0.1–24 μM, the absorbance at 652 nm exhibited a linear relationship to the concentration of Cu2+. The low detection limit of our method could achieve 0.024 μM, and our strategy can also be well applied in the real sample with good recoveries. Our work implied the promising use of nanozymes in heavy metal ion detection.