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 (TiO2 NPs)/ITO electrode which was prepared by sintering titanium dioxide (TiO2) 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 TiO2, which resulted in spatial separation of electron‐hole and enhancement of photocurrent signal. XAO oxidizes xanthine to produce hydrogen peroxide (H2O2). Part of the photoinduced electrons from CS−GSH−CuNCs transferred and catalyzed the reduction of H2O2, 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.

A Photoelectrochemical Sensor Based on DNA Bio-Dots-Induced Aggregation of AuNPs for Methionine Detection

“…The electrical impedance of the electrode increases to maximum. This is because AuNPs accumulate on the electrode surface, resulting in an increased e --h + recombination probability in CS-GSH-CuNCs and a reduced transfer of photogenerated electrons to the electrode [34]. However, when Met is present, AuNPs gathered on the electrode surface fall off and bind with Met because the interaction between Au and S is stronger than the interaction between Au and N [37,38,42], and the electrode conductivity is enhanced and the impedance is reduced (curve f).…”

“…The detection performance of PEC sensors is closely related to the modified photosensitive materials. It is demonstrated that chitosan-coated and glutathione-protected copper nanocluster/titanium dioxide nanoparticles (CS-GSH-CuNCs/TiO 2 NPs) are a good photosensitive composite [34]. Photoexcitation at a wavelength of 365 nm causes the electrons in a copper nanocluster to move from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) [35].…”