Influence of porous anodic alumina matrix upon europium luminescence from sol–gel-derived films

Photoluminescence (PL) and PL excitation (PLE) spectra of Eu-doped TiO2, SnO2, and In2O3 xerogel films fabricated on porous anodic alumina (PAA) and flat substrates of monocrystalline silicon are analyzed. PAA matrix changes significantly the excitation conditions of Eu in TiO2 xerogel film, resulting in broad intense band at 280 nm in PLE spectra that is not presented for the same xerogel film fabricated on Si substrate. Moreover, PAA changes the PL behavior of xerogel subjected to thermal treatment resulting in non-monotonous dependence PL intensity on annealing temperature. It is revealed that increase of annealing temperature from 200 to 500 °C leads to decrease of intensity of predominant spectral band at 611 nm, whereas further temperature increase up to 900 °C increases the PL intensity over the value obtained at initial annealing temperature.