Double enzymatic cascade reactions within FeSe–Pt@SiO2 nanospheres: synthesis and application toward colorimetric biosensing of H2O2 and glucose

Abstract

A facile process was developed for the synthesis of FeSe–Pt@SiO₂ nanospheres based on the hydrothermal treatment of FeCl₃·6H₂O, selenium and NaBH₄ in ethanolamine solvent, followed by reducing HPtCl₄ with NaBH₄ in the presence of FeSe particles to obtain FeSe coated with Pt NPs (FeSe–Pt), ending with a surfactant assembled sol–gel process to obtain FeSe–Pt@SiO₂. The morphology and composition of FeSe–Pt@SiO₂ were characterized by transmission electron microscopy, high resolution TEM, X-ray diffraction and Fourier transform infrared spectroscopy. Structural analyses revealed that FeSe–Pt@SiO₂ nanospheres were of regular spherical shape with smooth surfaces due to the SiO₂ shells, compared with FeSe particles with 150 nm lateral diameter. The prepared FeSe–Pt@SiO₂ nanospheres possessed both intrinsic glucose oxidase (GOx-) and peroxidase-mimic activities, and we engineered an artificial enzymatic cascade system with high activity and stability based on this nanostructure. The good catalytic performance of the composites could be attributed to the synergy between the functions of FeSe particles and Pt NPs. Significantly, the FeSe–Pt@SiO₂ nanospheres as robust nanoreactors can catalyze a self-organized cascade reaction, which includes oxidation of glucose by oxygen to yield gluconic acid and H₂O₂, and then oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H₂O₂ to produce a colour change. Colorimetric detection of H₂O₂ and glucose using the FeSe–Pt@SiO₂ nanospheres was conducted with high detection sensitivities, 0.227 nM and 1.136 nM, respectively, demonstrating the feasibility of practical sensing applications. It is therefore believed that our findings in this study could open up the possibility of utilizing FeSe–Pt@SiO₂ nanospheres as enzymatic mimics in diagnostic and biotechnology fields.