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.