Preparation of Z-scheme 3D ZnO/Au/g-C3N4 heterostructures for the photoelectrochemical sensing of glutathione

Three-dimensional (3D) ZnO nanostructures were used as the support for gold nanoparticles (AuNPs) and graphite carbon nitride (g-C3N4) to form a Z-scheme heterostructure photoelectrode (3D ZnO/Au/g-C3N4) in this work. The 3D structure of the ZnO nanorods provided a directional channel for fast carrier transport and abundant reaction sites. ZnO and g-C3N4 formed the Z-scheme heterojunction, and the AuNPs sandwiched between ZnO and g-C3N4 acted as the mediators and greatly reinforced vector electron transfer in the Z-scheme heterojunction. Then, the 3D ZnO/Au/g-C3N4 photoelectrode was applied to develop a sensitive photoelectrochemical (PEC) biosensor for reduced glutathione (GSH) detection. GSH can act as a hole scavenger and reduce the recombination of photogenerated electron–hole pairs, which results in an increase in the photocurrent of the system. The enhanced current showed good linearity with GSH concentration in the range of 7–2000 μM, and the system had a limit of detection of 2.3 μM. The proposed biosensor exhibited good selectivity and reproducibility, obtaining satisfactory results in the analysis of the target in human serum.