10 September 2014 Luminescence studies on solid and nanostructured SiO2:Eu3+ spheres obtained by sol-gel route
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Rare earths in confined systems are studied because their possible imaging applications. In this work we studied the optical properties of Eu3+ inside nanoporous spheres. Their properties were compared with these from europium in solid SiO2 spheres prepared by sol-gel method. Nanoporus channels were produced by using a surfactant. The last one was removed by chemical procedure. Then, europium was incorporated into the channels. XRD reveals the hexagonal structure of the pores. That was confirmed by HRTEM that shows the channels, clearly. N2 adsorption- desorption isotherm Type IV, characteristic of mesoporous materials, was obtained by BET. The I(5D07F2)/I(5D07F1) asymmetry ratio from Eu3+ transitions was obtained by photoluminescence. It had a value of 2.65 in the solid spheres and 1.65 in the nanoporous ones. That means Eu3+ is in an asymmetric site in both systems, and asymmetry is bigger in the solid spheres. Because the differences, we can use this parameter to distinguish between both systems, easily. Photoluminescence lifetimes were obtained for the 5D0 → 7F2 emission. It was shorter in the solid spheres than in the nanoporous ones, confirming there is a more asymmetric site for the rare earth in the first case. IR spectra shows Eu3+ is not incorporated as part of the SiO2 network.
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J. A. García-Macedo, J. A. García-Macedo, E. Terán H., E. Terán H., A. Franco, A. Franco, "Luminescence studies on solid and nanostructured SiO2:Eu3+ spheres obtained by sol-gel route", Proc. SPIE 9161, Nanophotonic Materials XI, 916112 (10 September 2014); doi: 10.1117/12.2061390; https://doi.org/10.1117/12.2061390

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