Tin(II) Antimonates with Adjustable Compositions: Effects of Band-Gaps and Nanostructures on Visible-Light-Driven Photocatalytic H2Evolution

Urea-derived graphitic carbon nitride (u-g-C3N4) films with highly enhanced antimicrobial and sporicidal activity

In this manuscript, we describe the fabrication of photoactive biocidal or sporicidal films from urea-derived graphitic carbon nitride (u-g-C₃N₄). Co-deposited films of u-g-C₃N₄ and Escherichia coli O157:H7 (IC₅₀=14.1±0.2mJ) or Staphylococcus aureus (methicillin resistant IC₅₀=33.5±0.2mJ, methicillin sensitive IC₅₀=42.7±0.5mJ) demonstrated significantly enhanced bactericidal behavior upon administration of visible radiation (400nm≤λ≤426nm). In all cases, complete eradication of the microbial sample was realized upon administration of 100mJ of visible radiation, while no antimicrobial activity was observed for non-irradiated samples. In contrast, Bacillus anthracis endospores were more resistant to u-g-C₃N₄ mediated killing with only a ca. 25% reduction in spore viability when treated with a 200mJ dose of visible radiation. Characterization of u-g-C₃N₄ reveals that the improved activity results from enhancements of both the surface area and reduction potential of the material's conduction band edge, coupled with fast injection of charge carriers into localized states and a decline in radiative recombination events. The results of this study demonstrate that g-C₃N₄-based materials offer a viable scaffold for the development of new, visible light driven technologies for controlling potentially pathogenic microorganisms.

Preparation and characterization of photoactive antimicrobial graphitic carbon nitride (g-C3N4) films

Photoactive films derived from nanostructured samples of metal-free, intermediate band gap semiconductor graphitic carbon nitride (ns-g-C₃N₄) have been synthesized and characterized for their particle properties and antimicrobial activity. Physical characterization reveals that these materials are composed of discrete nanoparticles whose dimensions range from 200 nm to 700 nm. Investigation of the photochemical reactivity of ns-g-C₃N₄ using coumarin-3-carboxylic acid (3-CCA) indicates that this material produces reactive oxygen species (ROS) under visible radiation. When irradiated with 0.31J visible light, ns-g-C₃N₄-based materials reduced the viability of both gram-negative Escherichia coli O157:H7 and gram-positive Staphylococcus aureus by approximately 50%. Nearly complete inactivation of both strains of microorganisms was achieved upon administration of a 0.62J dose of visible radiation. Importantly, no biocidal activity was observed for non-irradiated samples, indicating that the g-C₃N₄-derived films are not inherently toxic in the absence of visible light. The results of this study suggest that materials and, by extention, films and coatings derived from g-C₃N₄ may present a novel route for controlling pathogenic microorganisms on surfaces in the environment, and could be useful in reducing incidents of hospital-acquired infections.

State-of-the-art Sn2+-based ternary oxides as photocatalysts for water splitting: electronic structures and optoelectronic properties

Synthesis and electronic structures for Sn²⁺-based oxide materials are reviewed in an attempt to develop visible-light-responsive photocatalysts.