Efficient green and red up-conversion emissions in Er/Yb co-doped TiO 2 nanopowders prepared by hydrothermal-assisted sol–gel process

• DOI: 10.1016/j.jlumin.2016.03.011
• Publication Date: 2016-03-22T18:01:34Z
• Authors: Rached Salhi; Jean-Luc Deschanvres
• Keywords: Photon Upconversion; Ytterbium; Quantum yield; Erbium

Abstract In this work, erbium and ytterbium co-doped titanium dioxide (Er–Yb:TiO2) nanopowders have been successfully prepared by hydrothermal-assisted sol–gel method using supercritical drying of ethyl alcohol and annealing at 500 °C for 1 h. Nanopowders were prepared with fixed 5 mol% Erbium concentration and various Ytterbium concentrations of 5 and 10 mol%. The powders were characterized by studying their structural, morphology and photo-luminescent properties. The annealing treatment at 500 °C was found to enhance the crystallinity of the TiO2 anatase structure and the upconversion (UC) emission of the nanopowders. UC emissions were investigated under 980 nm excitation, and the Er–Yb:TiO2 nanopowders exhibited the intense green (520–570 nm) and red (640–690 nm) upconverted emissions of Er ions originating from an efficient Yb–Er energy transfer process. The absolute upconversion quantum yield (UC-QY) of each nanopowders was measured for the UC emissions centered at 525, 550 and 655 nm at varying excitation power densities. UC-QY analysis has revealed that 5 mol% Er–5 mol% Yb:TiO2 nanopowders possess the highest total quantum yield of 2.8±0.1% with a power density of 16.7 W/cm2. These results make these nanopowders promising materials for efficient upconversion in photonic applications.