Upconversion luminescence properties of Y2O3:Yb, Er and Y2O2S:Yb, Er nanoparticles prepared by complex precipitation

Abstract

The Yb3+, Er3+ doped Y2O3 and Y2O2S upconversion nanophosphors were prepared by the direct complex precipitation method with the mixed solution of NH4HCO3 and NH3·H2O as the complex precipitant. The precipitate of Re OH x CO 3 y calcined at 900°C in air presents the pure Y2O3 with cubic structure, and the calculated crystalline size is about 26 nm, while the Y2O2S:Yb, Er nanocrystals were obtained by annealing the same precipitate at 900°C but in the atmosphere of N2 gas containing sulfur vapor. The obtained sample presents the pure hexagonal structure of Y2O2S with calculated crystalline size of 29 nm. According to the transmission electronic microscopy (TEM), the nanophosphors exhibit uniform quasispherical shape and size about 30 nm. By using the 980 nm excitation laser, the properties of upconversion luminescence and energy transfer processes were studied in detail for the different concentration of Yb3+ in Er3+ doped Y2O3 as well as the Yb3+, Er3+ codoped Y2O2S nanocrystals. The high-efficient red and yellow upconversion emissions were both observed by naked eyes in day time corresponding to the Y2O3:Yb, Er and Y2O2S:Yb, Er phosphors, respectively. Thus the upconversion nanoparticles combining its high efficient emission would pave the way for ideal fluorescence probes in biological applications.