An enhanced photoelectrochemical platform: graphite-like carbon nitride nanosheet-functionalized ZnO nanotubes

The development of new promising visible-light-driven metal-free photosensitive materials is attracting ever increasing interest within the field of photoelectrochemical (PEC) assays. Large-scale two-dimensional (2D) graphite-like carbon nitride (g-C₃N₄) nanosheets with obvious upconversion properties were obtained through a liquid exfoliation route using bulk g-C₃N₄ as the precursor. ZnO nanotube arrays obtained by corrosion of ZnO nanorods were functionalized by 2D g-C₃N₄ nanosheets, and provided a PEC platform showing enhanced PEC activity compared to those of the individual materials, which could be ascribed to the appropriate band alignment between the g-C₃N₄ nanosheets and the ZnO nanotubes. On the basis of the enhanced PEC activity, a novel PEC biosensing platform was demonstrated to detect carcinoembryonic antigen as a model target analyte using the in situ produced ascorbic acid as an electron donator under visible light source irradiation. As expected, excellent assay results were achieved owing to the synergistic effect. Furthermore, benefiting from the inherent attractive properties, the water-soluble ultrathin g-C₃N₄ nanosheets might open a new promising platform for bioimaging.