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

Graphical Detection mechanism of PEC sensor for detecting xanthine based on photocurrent signal changes caused by hydrogen peroxide reduction catalyzed by copper nanoclusters 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.