[nanoPost] Tailored functional properties of Ag-nanoparticles in thin TiO2-films

Research Centre Germany

Silver nanoparticles embedded in TiO2-films have received increasing attention in recent years due to their high potential
for applications in the fields of solar energy conversion, photocatalysis, chemical and biological sensing, antibacterial
coatings and unique optical components. The special optical properties are mainly based on surface-enhanced Raman
scattering, localized surface plasmon resonance, and metal-enhanced fluorescence. Especially the structure, size, shape
and arrangement of the embedded nanoparticles play an essential role in tailoring the functional properties of such
nanocomposite coatings.

In the present study Ag-TiO2 nanocomposite films were prepared by means of RF-magnetron sputtering and subsequent
annealing. The structural, chemical and optical properties of the deposited films have been characterized by means of SEM,
UV-Vis Spectroscopy, XRD, Raman Spectroscopy, XPS and X-Ray Absorption Spectroscopy for different film structures like
Ag nanoparticles on top of TiO2 layers or Ag nanoparticles embedded in TiO2 as intermediate layers. The influence of the
deposition parameters on the structure of the nanocomposite film and on its optical properties was investigated.
A controlled modulation of Ag content and particle size, shape and distribution in a TiO2 dielectric film matrix could be
obtained as a function of the applied RF-power, total pressure, annealing temperature and deposition time.
In order to achieve a detailed microscopic understanding of kinetic mechanisms in such heterogeneous
photoelectrocatalytic nanocomposite films, in-situ electrochemical Surface-enhanced Raman Spectroscopy was used to
study the adsorption behavior of carboxylate species (COO-) on adsorption sites of the nanocomposite film and the
interaction between semiconductor and metal under external electric field. The results will be linked to the further
applications like dye photosensitization in solar cells.