Sol-gel technique for the generation of europium-doped mesoporous and dense thin films: A luminescent study

In this paper, a series of europium-activated titania mesoporous and dense thin films were prepared by sol-gel process. Structural characterizations show that high europium ion loadings can be incorporated into titanium dioxide walls with out destroy in the mesoporous arrangement. However, high europium content locks the titanium dioxide crystallization process. Upon 10% europiumions loading, mesoporous thin films are mainlyamorphous, whereas dense ones are still partially crystallized. Eu3+ ion luminescence has been investigated by exciting through the semiconductor host lattice. Emission features reveal that europiumions adopt similar environments (nano crystalline and glassy-likeones) in both dense and mesoporous thin films. Fluctuations of europium emission under continuous UV excitation have been observed. One observes that the effect strongly depends on the thin films'crystalline character which is strongly related with the texturation and existence at the mesoscopic length scale