Spinel Zn3V3O8 nanosheets via a one-step hydrothermal synthesis with peroxidase-like activity for high sensitivity glucose colorimetric detection in synthetic perspiration

Abstract

Due to their specific spinel structure, ternary oxides with multi-catalytic sites on a highly active exposed surface are recommended as alternative bio-catalysts. Spinel zinc vanadate with two-dimensional nanosheets (Zn₃V₃O₈ NSs) was synthesised using a one-step hydrothermal route with CTAB and glycine as a bi-surfactant, where each NS has a thin thickness (25 nm) and wide cross section (2 μm). As a key parameter for peroxidase-like activity, the Michaelis–Menten constant (K_m) for Zn₃V₃O₈ NSs was calculated to be 0.271 mM with TMB and 1.317 mM with H₂O₂ at optimum conditions, indicating a higher affinity for the exposed (011) facet towards horseradish peroxidases. This affinity is related to the geometric matching between V⁴⁺ active sites and the terminal amino groups of TMB. The V⁴⁺ ions on the (011) facet act as dangling bonds and readily react with H₂O₂ in a Fenton-like reaction. The peroxidase-like activity for Zn₃V₃O₈ NSs is verified by the formation of [V(IV)–OO˙] by the ˙O₂⁻ and V⁵⁺ near V⁴⁺ sites, but oxidase activity for Zn₃V₃O₈ NSs. Based on the peroxidase-like activity, Zn₃V₃O₈ NSs were used as a colorimetric glucose sensor with a wide linear range from 0.01 to 0.5 mM and a detection limit (LOD = 3σ/S) of 2.81 × 10⁻⁷ M. The colorimetric sensor also exhibited high accuracy and selectivity in synthetic perspiration samples.