Fabrication of CeVO4 as nanozyme for facile colorimetric discrimination of hydroquinone from resorcinol and catechol

Abstract

A simple method was proposed for the preparation of CeVO₄. The as-synthesized CeVO₄ was, for the first time, demonstrated to exhibit both peroxidase-like and oxidase-like activity, which catalyzes the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to form a typical blue solution in the presence or absence of H₂O₂. Moreover, the mechanism of its dual-enzyme activity was investigated in detail. The Michaelis constant (K_m) value for CeVO₄ (0.136 mM) was lower than that of horseradish peroxidase (0.424 mM) with TMB as the substrate. Interestingly, hydroquinone (H₂Q), dihydroxybenzene isomer, undergoes reduction accompanying the oxidation of TMB by the CeVO₄ oxidase mimic along with a visible color change, while the other two dihydroxybenzene isomers, i.e., resorcinol (RC) and catechol (CC), do not. Based on these findings, a colorimetric platform was developed to discriminate H₂Q from RC and CC. Under optimal conditions, a linear relationship between the H₂Q concentration and absorbance was observed from 0.05 to 8 μM, and a limit of detection of 0.04 μM was achieved. Moreover, this colorimetric platform can selectively reveal H₂Q concentrations in the presence of other dihydroxybenzene isomers.