Tunable water-soluble carbon nitride by alkali-metal cations modification: Enhanced ROS-evolving and adsorption band for photodynamic therapy

Graphitic Carbon Nitride (g-C3N4) has extensive application prospect of photodynamic therapy (PDT), which can be attributed to the biocompatibility and photosensitivity. However, it suffers from the near-ultraviolet absorption edge and low reactive oxygen species (ROS) release rate. This work exhibits an atomic-thickness water-soluble g-C3N4 with alkali Zn2+ and K+ modification (MCN), whose absorption edge is tuned from 460 nm for GCN to the entire visible-light region (663 nm), and bandgap is reduced to 1.94 eV. Both K+- bridging intercalation and the in-plane Zn-N significantly enhance the photocatalytic performance, as well as inhibit the overexpression of glutathione (GSH) significantly. The synergistic effect make that the release rate of ROS is about 45.16 % (7.95 % for pristine g-C3N4), accomplishing a considerable inactivation efficiency of malignant melanoma A375. This work fundamentally releases the limitation of g-C3N4 as a PDT photosensitizer, revealing its multifunctional promise to cancer therapy.