Nanostructural and functional properties of Ag-TiO2 coatings prepared by co-sputtering deposition technique.

Ag-TiO2 nanocomposite coatings with varying Ag content were prepared by co-sputtering from two separate sputter sources. This technique allows to prepare coatings not only with a large variation of Ag content and different gradient but also allows much better control of nanocomposite thickness and nanostructure compared with mostly used techniques based on wet chemical approaches. Various thicknesses of nanocomposite layers with different deposition parameters were studied to obtain a better understanding on the growth of Ag nanostructures in the TiO2 films. The metal-volume-fraction was varied between 15% and 47%. Structural and microstructural investigations of the nanocomposite films were carried out by transmission electron microscopy. Special attention was paid to surface segregation of Ag and its suppression. The observed segregation on TiO2 contrasts sharply with the well known embedding tendency of Ag clusters on polymers. Functionality of the Ag-TiO2 nanocomposites was demonstrated via UV-Vis spectroscopy and antibacterial tests. It was shown that a thin layer of TiO2 can be used as an effective barrier to tailor the release behaviour of Ag ions.