Peroxidase-like Cu–Fe bimetal oxide mesoporous nanospheres identified for the efficient recognition of toxic o-aminophenol and bioactive glutathione

Abstract

To strengthen the enzyme-mimetic catalytic activity of the classical transition metal oxide of copper and iron, bimetal Cu–Fe oxide mesoporous nanoparticles (Cu–Fe MNPs) were prepared in one pot under microwave-assisted conditions. The proposed Cu–Fe MNPs possessed a well-distributed mesoporous structure with an average aperture of 3.91 nm and a high BET specific surface area of 197.93 m² g⁻¹. Their peroxidase-like kinetic parameters (K_m/V_max) toward catalyzing the redox reactions of TMB and H₂O₂ were 0.013 mM/3.01 × 10⁻⁸ M s⁻¹ and 56.58 mM/4.12 × 10⁻⁸, respectively. In particular, both toxic o-aminophenol (o-AP) and bioactive glutathione (GSH) could deteriorate their peroxidase-like property with an obvious color change from blue to colorless in the proposed Cu–Fe MNPs-TMB-H₂O₂ system. Under optimized conditions, Cu–Fe MNPs-TMB-H₂O₂ showed selective response to o-AP and GSH with quite low detection limits of 1.57 × 10⁻⁸ mol L⁻¹ (S/N = 3) and 3.35 × 10⁻⁸ mol L⁻¹ (S/N = 3), respectively. When they were applied for the visual monitoring of o-AP and GSH in real aqueous, fruit juice and medicinal samples, the detection recovery (%) was between 96.8–101.4% for o-AP and 97.1–105.8% for GSH. The mechanisms of the synergetic enhancement of the peroxidase-like activity of Cu–Fe MNPs and the selective recognition of o-AP and GSH were investigated in detail.