Rapid colorimetric sensing of ascorbic acid based on the excellent peroxidase-like activity of Pt deposited on ZnCo2O4 spheres

Abstract

Pt deposited ZnCo₂O₄ nanocomposites (Pt/ZnCo₂O₄) were prepared by a two-step method and found to possess excellent intrinsic peroxidase-like activity. With the aid of a colorless peroxidase substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), the peroxidase-like activity of Pt/ZnCo₂O₄ was evaluated in the presence of H₂O₂, which conforms to the Michaelis–Menten kinetic equation. The colorless TMB rapidly turned into a blue product (oxTMB) in just 3 min. Pt/ZnCo₂O₄ has a higher affinity for H₂O₂ and TMB compared to natural horseradish peroxidase (HRP) and can be used as a peroxidase mimic for establishing a colorimetric sensing platform. Importantly, fluorescent probe and electrochemical data verify that the catalytic activity of Pt/ZnCo₂O₄ is due to the accelerated electron transfer between H₂O₂ and TMB. Furthermore, the peroxidase-like activity of Pt/ZnCo₂O₄ was significantly inhibited by ascorbic acid (AA), resulting in the fading of blue oxTMB. Based on this, a simple and efficient colorimetric sensor for H₂O₂ and AA has been constructed. Under optimal conditions, the linear response ranges of H₂O₂ and AA are 100–2000 μM and 1–15 μM, respectively. The detection limits of H₂O₂ and AA are 26.44 μM and 0.456 μM, respectively.