Antibacterial activities of silver-nanoparticles-titania composite thin films fabricated by the molecular precursor method (MPM)
Titanium Oxide (TiO2) as a photocatalyst produces free radicals upon receiving light energy; thus, it possesses antibacterial properties. The antibacterial property of silver-nanoparticles-doped TiO2 photocatalysts (Ag-NPs/TiO2) could be further enhanced by visible light illumination, which also widens its practical applications. However, the major limitation of this Ag-NPs/TiO2 composite material is its poor miscibility, which subsequently reduces the antibacterial activities of the material. To overcome this limitation, the Molecular Precursor Method (MPM) was adopted in this study as a synthetic method for the fabrication of Ag-NPs/TiO2 composite thin films with various and unprecedentedly high amounts of Ag-NPs. X-ray Diffraction (XRD) results revealed the presence of metallic Ag and a mixed phase in composite films. For composite films with less Ag content, Field Emission-Scanning Electron Microscopic (FE-SEM) analyses showed well dispensed Ag nanoparticles which appeared uniformly distributed across the films. Particles agglomeration and rough surface morphology were observed in films with high loads of Ag-NPs. Far-reaching absorption across the visible region was observed for composite films and the Surface Plasmon Resonance (SPR) of Ag-NPs is ascribed to the effect. The antibacterial behaviors of resultant films were investigated against a gram negative bacterium, Escherichia coli as a model, both in the dark and under visible light by using the Antibacterial Susceptibility Testing method. Composite films were found to have superior bactericidal activity than either neat TiO2 or Ag-only films, both in the dark and under visible light. Furthermore, films showed enhanced antibacterial activity under visible light than in the dark. In summary, all films exhibited bactericidal effect of different proportions depending on the Ag-NPs content in the titania matrix.
Silver-nanoparticles-titania, Molecular precursor method
Networked Digital Library of Theses and Dissertations