Study on the peroxidase-like activity of cobalt phosphate and its application in colorimetric detection of hydrogen peroxide.

The Co 3 (PO 4) 2.8 H 2 O nanozyme was in situ synthesized through direct reaction between cobalt (Ⅱ) and phosphate, and its peroxidase-like activity was studied in the presence of hydrogen peroxide (H 2 O 2) using a chromogenic substrate 3, 3′, 5, 5′ - tetramethylbenzidine (TMB). The effects of pH value, temperature, and incubation time on the conversion of TMB to oxidized TMB (oxTMB) catalyzed by Co 3 (PO 4) 2.8 H 2 O in the presence of H 2 O 2 were optimized. The peroxidase-like activity of Co 3 (PO 4) 2.8 H 2 O conforms to the Michaelis-Menten kinetics, and its Michaelis constant (K m) is 0.073 mM, showing a higher H 2 O 2 affinity than natural horseradish peroxidase (HRP) and some other peroxidase nanozymes. The mechanism exploration experiment confirmed that the hydroxyl radical (•OH) is the main active species in the catalytic reaction of Co 3 (PO 4) 2.8 H 2 O. Finally, based on the inherent peroxidase-like activity of Co 3 (PO 4) 2.8 H 2 O, a simple colorimetric detection method for H 2 O 2 was established, with a linear range of 15.0 − 100.0 μM and a detection limit of 4.385 μM. The method was applied to the determination of H 2 O 2 in milk samples with the spiked recovery of 90.2%− 106.2%. This study reports a novel nanozyme that can be easily produced in situ, which is exempt from the harsh, cumbersome, and time-consuming synthesis and purification procedures. In addition, the H 2 O 2 colorimetric detection method based on the nanozyme has the advantages of low cost, convenient, high sensitivity, and good selectivity. [Display omitted] • A novel nanozyme Co 3 (PO 4) 2.8 H 2 O of excellent catalytic activity is discovered. • This peroxidase-mimic nanozyme is in situ synthesized rapidly. • The hydroxyl radical is the major active specie in the catalytic reaction. • A sensitive colorimetric method for hydrogen peroxide determination is established. [ABSTRACT FROM AUTHOR]