Eu3+-doped CdS nanocrystals in SiO2 matrices: one-pot sol-gel synthesis and optical characterization

摘要

An enhancement of the europium luminescence has been reported in Eu-doped SiO2 materials by interaction with adsorbed CdS nanoparticles. In this paper, the preparation of homogeneous Eu3+-doped CdS nanocrystals embedded in SiO2 sol - gel matrices by a simple "one-pot'' method is reported. The synthesis conditions have been varied in order to modify the distribution of the lanthanide ions and the CdS nanoparticles within the nanocomposite. The structural modifications involve different strengths in the Eu3+ - CdS interaction. The effect of these interactions on the Eu3+ luminescence is discussed. The absorption, excitation and emission spectra of the Eu3+ species, as well as the time-resolved luminescence, revealed the existence of an efficient CdS --> Eu3+ energy transfer, responsible for the increase in the fluorescence intensity. However, when these species are spatially close, a diminution of the total emission and lifetime values is observed as a result of a back transfer from the Eu3+ ions to CdS nanoparticles.