Date

2015

Author

Akköprü Akgün, Betül

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Sol-gel processing routes for development of silver biocide-doped antibacterial silicate based coatings and powders were established and structural properties defining the antibacterial activity and long term durability were determined. During the first phase of this study, silver-doped silica based powders have been synthesized by hydrolysis and condensation of tetraethyl orthosilicate (TEOS, Si(OC2H5)4) in the presence of a silver nitrate (AgNO3) solution. The effects of modifications in sol-gel chemistry -acid catalysis and acid/base catalysis- and subsequent heat treatments on silica microstructure and on silver particles size were investigated. The acid-catalyzed sol-gels formed a microporous silica network whereas the two-step catalyzed silica exhibited a mesoporous structure. It was found that mesoporous structure leads to formation of bigger silver particles and promotes crystallization of silica network upon calcination and improving the antibacterial performance. In the following phase, silver nanoparticle containing silica coatings on soda-lime glass were prepared by the sol–gel process. The effect of thermal densification treatment at different temperatures in the range of 100–700ºC on microstructure and antibacterial properties of the coatings were examined. The mechanisms for formation and distribution of silver nanoparticles in the silica matrix with respect to the calcination temperature were discussed, and the correlation between the microstructural properties and antibacterial activity was described. The investigations revealed that silver nanoparticles were mainly in the metallic state during thermal treatments and silver accumulated on the surface diffuse into glass substrate at higher calcination temperatures. A high level of antibacterial activity was observed for the coatings calcined at 300ºC or lower temperatures allowing accommodation of silver on the surface of the coating. Silver diffusion into bulk via ion-exchange with sodium and calcium ions from glass substrate during calcination at higher temperatures (500 or 700ºC) resulted in apparent degradation in the antibacterial activity.

Subject Keywords

Silver., Silica., Coatings., Nanoparticles., Sol-gel processs.

URI

http://etd.lib.metu.edu.tr/upload/12619431/index.pdf
https://hdl.handle.net/11511/25133

Collections

Graduate School of Natural and Applied Sciences, Thesis