Orientation of spheroid-shaped silver nanoparticles in mesostructured silica films studied by polarized absorption and low-frequency Raman spectroscopy

Orientation of spheroid-shaped silver (Ag) nanoparticles (NPs) embedded in mesostructured silica sol gel films is studied by polarized absorption measurements and low-frequency Raman scattering, two complementary techniques well-adapted to characterize nanostructures in amorphous matrix. Comparison is made with analysis of mesostructured silica sol gel films containing nanospheres. Polarization-dependent absorption spectra clearly evidence spheroid-shaped NP orientation and their mean aspect ratio is estimated from corresponding polar plots. Mean diameter of spherical NPs is deduced from low-frequency Raman scattering spectra as well as size of elongated spheroid NPs.