Abstract
Photocatalysts produce free radicals upon receiving light energy; thus, they possess antibacterial properties. Silver (Ag) is an antibacterial material that disrupts bacterial physiology. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. However, the major limitation of this Ag-TiO2 composite material is its durability; the antibacterial property decreased markedly after repeated use. To overcome this limitation, we developed TiO2(N)/Ag/TiO2(N) sandwich films in which the silver is embedded between two TiO2(N) layers. Various characteristics, including silver and nitrogen amounts, were examined in the composite materials. Various analyses, including electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and ultraviolet–visible absorption spectrum and methylene blue degradation rate analyses, were performed. The antibacterial properties of the composite materials were investigated. Here we revealed that the antibacterial durability of these thin films is substantially improved in both the dark and visible light, by which bacteria, such as Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus, and Acinetobacter baumannii, could be efficiently eliminated. This study demonstrated a feasible approach to improve the visible-light responsiveness and durability of antibacterial materials that contain silver nanoparticles impregnated in TiO2(N) films.
Highlights
Photocatalysts produce free radicals upon receiving light energy; they possess antibacterial properties
Our previous study indicated that nitrogen-doped TiO2 [TiO2(N)] thin film coated with silver nanoparticles exhibited higher antibacterial activity under the illumination of visible light[6]
Because the silver nanoparticles are directly exposed to the environment and detached from the surfaces of the thin films, we observed that the antibacterial activity was substantially reduced after repeated usages
Summary
Photocatalysts produce free radicals upon receiving light energy; they possess antibacterial properties. Our previous study reported that the high antibacterial property of silver nanoparticles on the surfaces of visible light-responsive nitrogen-doped TiO2 photocatalysts [TiO2(N)] could be further enhanced by visible light illumination. Impurity doping or metal-particle-impregnated TiO2 may reduce the recombination rates of pairs of electrons and holes Impregnated material such as silver possesses antibacterial properties. Previous studies have described the development of visible-light-responsive antibacterial photocatalysts, which ensure high quantum efficiency under sunlight and can be used safely in indoor settings, preventing users from UV exposure, as a major advancement in photocatalytic material research[2,5,6,8,9,10,11,12,13]. In addition to E. coli, pathogenic bacteria, such as S. aureus, S. pyogenes (Gram-positive), and A. baumannii (Gram-negative), were first used to analyze the bactericidal effects of these Ag-TiO2 sandwich films
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