| Summary: | 碩士 === 國立東華大學 === 材料科學與工程學系 === 99 === Titanium dioxide（TiO2）has been developed and applied extensively in the form of coatings, in particular for its unique properties such as non-toxicity, high photocatalytic activity and strong self-cleaning ability, and has great potential for applications of photocatalytic and antibacterial purposes. In this study, a reactive magnetron sputtering system was used to deposit TiO2 and various silver containing Ag/TiO2 multilayered films. Subsequently the films were rapid thermal annealed at 500 oC for 5 hours. Due to the doping effect of silver in this TiO2 semiconductor material, the silver can capture electron to increase the carrier mobility when the illumination generated electron-hole pairs. The surface plasma generates plasmon resonance to enhance of films absorption, and can enhance the antibacterial activity of TiO2 films.
The structure and crystallinity of the as-grown Ag/TiO2 complex films were determined by X-ray diffraction (XRD). The morphology and thickness of the films were observed by using a filed emission scanning electron microscope (FESEM). An energy-dispersive spectrometer (EDS) was used to measure the concentration of silver in the films. An ultraviolet-visible (UV-vis.) spectrotometer was used to obtain the absorption spectra of the films. The photocatalytic efficiency properties of the films under visible-light illumination were evaluated by measuring the decomposition rate of methylene blue in aqueous solution. Escherichia coli (E-coli) was chosen for in-vitro anti-bacterial analyses.
In this study, Ag particles were uniformly distributed on the TiO2 surface after rapid thermal annealing. The Ag/TiO2 thin film with Ag content higher than 1.57 at.% possessed good photocatalytic efficiency and antibacterial activity. The Ag/TiO2 complex multilayer structure with silver oxides was prepared by periodic switch of Ag cathode power during the deposition of TiO2 films. After rapid thermal annealing at 500℃ for 5 hours in air, the deposited films transformed to anatase from amorphous phases. The silver oxides were reduced to form Ag and a new Ag2TiO3 phase was also found. It showed that the multilayered Ag- TiO2/TiO2 changed to a monolayer. Porous and rough structure was obtained because of phase transformation, density change, and inter-diffusion between Ag and TiO2 at high temperature. Ag particles segregated onto the surface of the Ag/TiO2 complex thin films. Due to the increase of specific area, the sample has better photocatalytic activity than TiO2, and the antibacterial rate is higher than 80%.
To obtain the photodegenerative and antibacterial performances of the Ag-TiO2, a series of annealed Ag-TiO2 with different Ag contents were synthesized. A weak rutile phase was found in the Ag/TiO2 complex film with a small content of Ag (1.91 at.%). When the silver content is higher than 10.36 at.%, the rutile phase disappeared, and a Ag2TiO3 phase were observed. By increasing the Ag content to 18.51%, the Ag/TiO2 complex film with uniform silver segregates on the surface had the best photodegeneration rate and antibacterial efficiency.
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