Luminescence from sol-gel-derived europium-doped films confined in mesoporous anodic alumina

Photoluminescence (PL) properties of the structure porous anodic alumina (PAA)/europium-doped xerogel film have been investigated with respect to the xerogel content (TiO2, Al2O3, In2O3), its transmittance and PL excitation wavelength. Three mechanisms of lanthanide optical excitation in the structure are proposed: (i) excitation through the PAA matrix; (ii) excitation through the xerogel matrix that depends on its transparency and, in turn, on xerogel content and thickness within the porous morphology; and (iii) direct excitation of a lanthanide ion due to the relative transparency of both the PAA and xerogel films. It is speculated that exploiting PAA allows significant change in the excitation conditions of lanthanides, probably due to multiple scattering of the exciting light, which is the main reason for the reported PL enhancement of lanthanides from the structure compared with similar PAA/lanthanide-doped xerogel films fabricated on flat substrates. (C) 2003 The Electrochemical Society.