|Title:||Silver-loaded titania nanocomposite for antimicrobial application|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
|Department:||Department of Applied Physics|
|Pages:||xii, 89 leaves : ill. ; 30 cm.|
|Abstract:||Titanium dioxide, also known as Titania (TiO2), is an important photocatalytic material that is becoming more and more widely used in our daily life. The photo-generated electrons and holes in TiO2 induce redox reactions with the surface adsorbed water and oxygen to produce hydroxyl radicals and atomic oxygen, which are very oxidative to degrade organic materials (pollutants, or even microorganisms). The drawback of TiO2 is that ultraviolet (UV) light is required to generate the electron-hole pairs needed for the photocatalytic reaction. One strategy to achieve the visible light activity is to dope TiO2 with various elements. Silver (Ag) is another type of inorganic antimicrobial material widely used in food, polymer, and textile, etc. It does not require any UV light illumination. The drawback of Ag is that Ag nanoparticles can easily change color either by oxidation into AgO with a brown appearance or by agglomeration into larger Ag particles with a black color. Besides, Ag is also an expensive material. Low concentration of Ag is ineffective for real applications while higher concentration greatly increases the cost. In order to take the advantages of both materials and to minimize their respective shortcomings, we have synthesized Ag@TiO2 nanocomposties by forming Ag nanoparticles onto the surface of nano-sized TiO2 particles with various dopants. In this project, nanocomposites of Ag@TiO2 doped with nitrogen or europium were synthesized by hydrothermal and/or sol-hydrolysis method. A low temperature synthesis route was developed. The effects on the decomposition of organic dye (methyl orange), the anatase-rutile phase transformation temperature and the antimicrobial activity for materials synthesized from different routes were studied systematically and were compared with that of the commercial P25 powders. Our results show that, doping of nitrogen or europium enhances the photocatalytic activity of the material under either UV or visible light irradiation. Coating Ag nanoparticles on the surface of TiO2 also enhances the photocatalytic activity under illumination. As expected, the Ag@TiO2 composite shows antimicrobial activity under both illuminated and dark conditions. Based on our results, the Ag@TiO2 nanocomposites are regarded to have potential applications as self cleaning and antimicrobial agents. For application purpose, TiO2 nanocomposites were coated on cotton fibers to make a new type of functional textile. Due to the addition of some surfactants and the small size of the nanocomposite, the nanoparticles can bind to the cotton fiber tightly. As a consequence of the high surface to volume ratio of the nanocomposites, the cotton fiber showed self cleaning and antimicrobial properties even a small amount of the nanocomposites was used.|
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