Enhanced photoelectrochemical sensing performance of graphitic carbon nitride by nitrogen vacancies engineering

Ciprofloxacin (CIP) as a typical antibiotic is widely used to produce antimicrobial drugs. Determination of CIP has raised extensive concern due to its possible toxic effects on human health. Here, a simple photoelectrochemical (PEC) sensor for detecting CIP has been developed by using the nitrogen-deficient graphitic carbon nitride (ND-g-CN) as a PEC active material. The ND-g-CN material exhibits two-dimension (2D) thin sheet structure with abundant nitrogen vacancies. The 2D thin sheet structure can enable the effective charge separation and transfer, thus dramatically improving the PEC performance. Simultaneously, nitrogen vacancies can serve as charge trap to efficiently inhibit the charge recombination. Furthermore, the synergistic effect of the two can widen the absorption edge and decrease the band gap of ND-g-CN material, resulting in increasing light harvesting and enhancing PEC performance. CIP can be oxidized by the holes of ND-g-CN, thus realizing effective charge separation, which can result in the amplification of the photocurrent. The designed PEC sensor demonstrated a wide detection range from 60 to 19090 ng L^-1 and a low detection limit of 20 ng L^-1 for CIP assay. This strategy broadens the application of graphitic carbon nitride (g-CN) material in PEC field and presents a promising potential for the practical application in the environmental monitoring.