The peroxidase-like catalytic activity of in situ prepared cobalt carbonate and its applications in colorimetric detection of hydrogen peroxide, glucose and ascorbic acid

In this study, the cobalt carbonate (CoCO3) was in situ prepared using cobalt (Ⅱ) and carbonate at room temperature, and the intrinsic peroxidase-like activity of CoCO3 was demonstrated for the first time through the oxidation of chromogenic substrate 3, 3', 5, 5' - tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). The effects of pH, reaction temperature, and incubation time on the catalytic activity of CoCO3 were studied. Under the optimal reaction conditions, the Michaelis constant (Km) of CoCO3 to H2O2 is 0.443 mM, which is lower than that of natural horseradish peroxidase and the previously reported peroxidase mimics. Furthermore, the mechanism exploration experiments confirm that the catalytic activity of CoCO3 is mainly attributed to the hydroxyl radical (•OH). Finally, based on the outstanding peroxidase-like activity of CoCO3, a colorimetric sensor for the detection of H2O2, glucose, and ascorbic acid (AA) was developed, which shows satisfactory selectivity and recovery. In addition, the total antioxidant capacity of three types of tea, dried lemon, three kinds of fresh fruit juice, and vitamin C tablet were determined. In short, this study reports a novel in situ generated CoCO3, which can be prepared rapidly at room temperature, eliminating the harsh, cumbersome, and time-consuming synthesis and purification process. The developed sensor based on the newly found excellent peroxidase-like activity of in situ prepared CoCO3 for the determination of H2O2, glucose, and AA is fast, simple, low cost, and high sensitivity.