Green and red up-conversion emissions of Er 3+–Yb 3+ Co-doped TiO 2 nanocrystals prepared by sol–gel method

Abstract

In this paper, green and red up-conversion emissions of Er 3+–Yb 3+ co-doped TiO 2 nanocrystals were reported. The phase structure, particle size and optical properties of Er 3+–Yb 3+ co-doped TiO 2 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 ( 2H 11/2, 4S 3/2→ 4I 15/2) and 640–690 nm ( 4F 9/2→ 4I 15/2) were observed for the Er 3+–Yb 3+ co-doped TiO 2 nanocrystals. The visible up-conversion mechanism and temperature dependence of up-conversion emission for Er 3+ in TiO 2 nanocrystals were discussed in detail.