Green and red up-conversion emissions of Er3+-Yb3+Co-doped TiO2 nanocrystals prepared by sol-gel method

In this paper, green and red up-conversion emissions of Er3+-Yb3+ co-doped TiO2 nanocrystals were reported. The phase structure, particle size and optical properties of Er3+-Yb3+ co-doped TiO2 nanocrystals samples were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis-NIR absorption spectra and photoluminescence (PL) spectra. Green and red up-conversion emissions in the range of 520-570 nm (H-2(11/2), S-4(3/2) -> I-4(15/2)) and 640-690 nm (F-4(9/2) -> I-4(15/2)) were observed for the Er3+-Yb3+ co-doped TiO2 nanocrystals. The visible up-conversion mechanism and temperature dependence of up-conversion emission for Er3+ in TiO2 nanocrystals were discussed in detail. (c) 2008 Elsevier B.V. All rights reserved.