A novel strategy to construct a direct Z-Scheme Bi@Bi2O2CO3/g-C3N4 heterojunction catalyst via PDA electronic bridge

Triggering "signal-on" photoelectrochemical responses by heterojunction transition for selective detection of copper(II) based on Pd/MoS2@g-C3N4 nanocomposites

Controlling the concentration of copper(II) in aquatic systems is of importance for human health. Numerous traditional technologies to detect Cu2+ may encounter with limitations, such as high signal background and complicated operation. Herein, a highly selective photoelectrochemical (PEC) sensor is proposed for the "signal-on" detection of Cu2+ employing g-C3N4 nanosheets with MoS2 and Pd quantum dots deposited (Pd/MoS2@g-C3N4). Pd/MoS2@g-C3N4 could present the enhanced photocurrents of specific responses to Cu2+ under light irradiation. MoS2 quantum dots on the sensor are agglomerated into MoS2 bulk during sensing Cu2+, forming an efficient Z-scheme heterojunction. The heterojunction transition induced photoelectrons transferring from the bulk MoS2 to g-C3N4, resulting in "signal-on" PEC responses. Such Z-scheme heterojunction has conquered the traditional heterojunction towards "signal-on" mechanism, that was further verified by band structure measurements and DMPO spin trapping ESR analysis. Photocurrent intensities increased gradually with the addition of incremental Cu2+ concentrations, achieving a detection limit of 0.21 μM and a broad linear interval range from 1 μM to 1 mM with high selectivity and stability. This work may open a new door towards the in situ construction of g-C3N4-based Z-scheme heterojunctions for the signal-on PEC sensing platform, providing wide applications in environmental monitoring and food safety.

Chitosan-based carbon nitride-polydopamine‑silver composite dressing with antibacterial properties for wound healing

Infection represents a major clinical barrier that delays wound healing, while the overuse of antibiotics can lead to bacterial resistance. Hence, it is of particular important to develop a new type of dressing to combat bacterial resistance. Herein, a carbon nitride-polydopamine‑silver complex (C₃N₄-PDA-Ag) was prepared using the photocatalyst C₃N₄ and silver nanoparticles (Ag NPs) to achieve a synergistic antimicrobial effect. The solution casting method was then employed to further modify the C₃N₄-PDA-Ag complex by compounding it with chitosan (CS), thereby forming a C₃N₄-PDA-Ag@CS film. The results revealed that the C₃N₄-PDA-Ag@CS film exhibits superior antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa compared to the CS group. The hemolysis, cytotoxicity, and in vivo implantation experiments indicated that the composite film possesses excellent in vitro and in vivo biocompatibility. In addition, the composite dressing promoted wound healing in infected mice by facilitating collagen deposition and accelerating epidermal regeneration. Collectively, the findings of this study clearly demonstrate that the C₃N₄-PDA-Ag@CS composite dressing has excellent antibacterial properties, biocompatibility, and enhances wound healing, thus providing a strategy for the application of photocatalytic materials for the treatment of infected wounds.