Antibacterial Z-scheme ZnIn2S4/Ag2MoO4 composite photocatalytic nanofibers with enhanced photocatalytic performance under visible light

Regulation of Charge Transfer Pathway in Ag-ZnIn2S4 Nanowires for Visible Photodynamic Therapy on Candida Albicans Infections

Photodynamic therapy (PDT) is receiving extensive attention as an antimicrobial strategy that does not cause drug resistance by reactive oxygen species (ROS). Herein, hierarchical Ag-ZnIn2S4 (Ag-ZIS) core-shell nanowires are synthesized by in situ Metal-Organic Framework derived method for efficient PDT of Candida albicans (C. albicans). The core-shell structure enables spatial synergy strategy to regulate the charge transfer pathway under visible light excitation, in which the Ag nanowires are like the highway for the photogenerated electrons. The enhanced charge carrier separation efficiency greatly increased the chances for the generation of ROS. As expected, the optimized Ag-ZIS nanowires exhibit excellent performance for inactivation of C. albicans under visible light irradiation (λ ≥ 420 nm, 15 min), and the effective sterilization concentration is as high as 107CFU mL-1. Moreover, in vivo infection experiments suggested that the PDT effect of Ag-ZIS nanowires on the mouse wound healing is better than that of the clinical Ketoconazole drug. The PDT antifungal mechanism of Ag-ZIS nanowires is also investigated, and superoxide anion is found to be the predominant active species to causes C. albicans damage. This work provides a new perspective for designing novel interface structures to regulate charge transfer to achieve efficient PDT antifungal therapy.

Principle of CoS2/ZnIn2S4 heterostructure effect and its mechanism of action in a visible light-catalyzed antibacterial process

The development of visible-light-driven catalytic antimicrobial technology is a significant challenge. In this study, heterojunctions were constructed for the appropriate modification of semiconductor-based photocatalysts. A simple hydrothermal method was used for material reconstruction, and smaller CoS2 nanoparticles were deposited and in situ grown on two-dimensional nanoflower-like ZnIn2S4 carriers to form CoS2/ZnIn2S4 (CS/ZIS) Schottky heterojunctions. Systematic study via characterization techniques and density functional theory calculations indicated that the excellent photocatalytic activity of CS/ZIS stemmed from the solid interfacial coupling between the two solid-phase materials. These materials acted as co-catalysts to increase the number of active reaction sites, enhance charge transfer, drive unidirectional electron movement, and improve charge separation efficiency, which effectively facilitated the production of reactive oxygen species (ROS). The optimized CS/ZIS heterojunction exhibited excellent performance for the efficient photocatalytic degradation of organic matter and inactivation of Escherichia coli (E. coli) compared with the ZnIn2S4 photocatalyst. Moreover, the antibacterial mechanism of the heterojunction photocatalyst and the extent of damage to the cell membrane and internal cytoplasm were explored by performing various assays. It was demonstrated that superoxide radicals are the predominant active species and multiple ROS act together to cause oxidative stress damage and cell inactivation.

Jointly augmented photocatalytic NO removal by S-scheme Bi12SiO20/Ag2MoO4 heterojunctions with surface oxygen vacancies

The deep oxidation of NO molecules to NO₃^- species with the avoidance of toxic NO₂ generation is a big and challengeable concern, which can be solved by the rational design and construction of catalytic systems with satisfactory structural and optical features. For such, in this investigation binary composites Bi₁₂SiO₂₀/Ag₂MoO₄ (BSO-XAM) were fabricated through a facile mechanical ball-milling route. From microstructural and morphological analyses, heterojunction structures with surface oxygen vacancies (OVs) were simultaneously created, contributing to the enhanced visible-light absorption, reinforced migration and separation of charge carries, and further boosted generation of reactive species such as superoxide radicals and singlet oxygen. Based on the density-functional theory (DFT) calculations, surface OVs induced the strengthened adsorption and activation of O₂, H₂O, and NO molecules and oxidation of NO to NO₂, while heterojunction structures were beneficial for the continuous oxidation of NO₂ to NO₃^- species. Thus, the heterojunction structures with surface OVs synergistically guaranteed the augmented photocatalytic NO removal and constrained NO₂ generation of BSO-XAM through a typical S-scheme model. This study may provide scientific guidances for the photocatalytic control and removal of NO at ppb level by Bi₁₂SiO₂₀-based composites through the mechanical ball-milling protocol.