Nickel-doped cuprous oxide nanocauliflowers with specific peroxidase-like activity for sensitive detection of hydrogen peroxide and uric acid.

Copper-based nanomaterials have the properties of mimetic enzymes and can be used as excellent candidates for colorimetric sensing due to their environmental friendliness, low cost, and high abundance. In this paper, Ni-doped Cu₂O nano cauliflower (Ni-Cu₂O) was synthesized for the first time and applied to the detection of H₂O₂ and uric acid (UA) in human serum and urine. It was found that the proportion of Ni incorporation controls the morphology and the catalytic effect of Ni-Cu₂O. The catalytic mechanism was studied by X-ray photoelectron spectroscopy, free radical capture experiments, photoluminescence spectroscopy, and steady-state kinetic analysis, which verified the redox reactions involving electron transfer and active substances. The results showed that Ni-Cu₂O could catalyze the formation of reactive oxygen species (•OH, O₂^•-, ₁O², h⁺) from H₂O₂, which could oxidize 3,3', 5,5'-tetramethylbenzidine (TMB) to oxTMB, and the color changed from colorless to blue. The Michaelis-Menten constant (K_m) and the maximum initial velocity (V_max) of Ni-Cu₂O were 1.8 mM and 15.2×10^-8 M/s, respectively. Based on the excellent peroxidase-like (POD) activity of Ni-Cu₂O, a colorimetric sensing platform combined with TMB was proposed to sensitively detect H₂O₂ and UA in a wide range, and the detection limits were as low as 0.17 μM and 0.22 μM, respectively. This study creates a platform for using the Cu-based cauliflowers as a biosensor to detect UA in the medical and biomedicine fields.