A photoelectrochemical sensor combining CS−GSH−CuNCs and xanthine oxidase for the detection of xanthine

Abstract A photoelectrochemical (PEC) sensor combining chitosan‐coated and glutathione‐protected copper nanocluster (CS−GSH−CuNCs) with peroxidase‐like activity and xanthine oxidase (XAO) was developed for rapid detection of xanthine. Firstly, CS−GSH−CuNCs was prepared by glutathione (GSH) reduction using chitosan (CS) as protective agent, and then was modified on titanium dioxide nanoparticles (TiO 2 NPs)/ITO electrode which was prepared by sintering titanium dioxide (TiO 2 ) on the ITO electrode surface by high temperature calcination. After excited by light at 350 nm, the photoinduced electrons from the lowest unoccupied molecular orbital (LUMO) of CS−GSH−CuNCs were transferred to the conduction band of TiO 2 , which resulted in spatial separation of electron‐hole and enhancement of photocurrent signal. XAO oxidizes xanthine to produce hydrogen peroxide (H 2 O 2 ). Part of the photoinduced electrons from CS−GSH−CuNCs transferred and catalyzed the reduction of H 2 O 2 , resulting in the reduction of the photocurrent. Under optimal conditions, the PEC sensor exhibits good sensitivity and reproducibility with the limit of detection (LOD) of 6.6 nmol ⋅ L −1 and a relative standard deviation of 3.5 % for 10 replicate detections of 1.00 μmol ⋅ L −1 xanthine and the linear range of 0.04–90.0 μmol ⋅ L −1 for xanthine. Furthermore, the PEC sensor presents nice selectivity owing to its enzyme‐like activity and was successfully applied to human urine, indicating its great potential for real sample analysis.