Three-dimensional hierarchical porous PtCu dendrites: A highly efficient peroxidase nanozyme for colorimetric detection of H_2O_2

摘要

Three-dimensional (3D) hierarchical porous PtCu dendrites (HPPtCuDs) as a novel peroxidase nanozyme were fabricated by the formation of 3D hierarchical PtCu dendrites via galvanic replacement, followed by chemical dealloying to selectively dissolve a less noble metal Cu from PtCu alloys. The morphology, structure and composition of HPPtCuDs were characterized in detail. Due to the special 3D porous dendritic structure (geometric effect) and electronic effect, the resulting HPPtCuDs exhibited intrinsic peroxidase-like activity, catalyzing the classical peroxidase substrate 3,3'.5,5'-tetramethyl-benzidine (TMB) by hydrogen peroxide (H_2O_2). The optimized conditions including pH, temperature, concentrations of both H_2O_2 and HPPtCuDs were obtained. Kinetic study indicated that the HPPtCuDs showed a stronger affinity for both TMB and H_2O_2 with lower Michaelis-Menten constant (K_m) values, compared with hierarchical PtCu dendrites and monometallic Pt microspheres. Based on the high catalytic activity, the HPPtCuDs was used to construct a colorimetric H_2O_2 sensor with a wide linear range of 0.3-325 μM and a low limit of detection (LOD) of 0.1 μM. The LOD was much lower than the H_2O_2 allowance level of US FDA (0.05 wt%, ca. 15 μM). With good anti-interference toward various anions and cations and good stability and reusability, this colorimetric H_2O_2 sensor was successfully applied to the determination of H_2O_2 in dairy milk products with satisfactory results.