Synthesis of Y2O3:Bi3+,Yb3+ nanosheets from layered yttrium hydroxide precursor and their photoluminescence properties
Y2O3:Bi3+,Yb3+ fluorescent nanosheets were prepared through calcining solvothermally synthesized layered yttrium hydroxide precursors at 600–1200 °C. X-ray diffraction (XRD) and transmission electron microscope (TEM) images confirmed that the nanosheets were polycrystalline with uniform crystallographic orientation. TEM images also confirmed that the nanosheet structure was maintained after calcination at temperatures up to 1000 °C. Atomic force microscope (AFM) images revealed that the Y2O3:Bi3+,Yb3+ nanosheets had thicknesses of 10–30 nm. The photoluminescence excitation (PLE) spectrum featured a broad band at 332 nm corresponding to the 1S0 → 3P1 transition of Bi3+. The emission spectrum featured a peak at 976 nm corresponding to the 2F5/2 → 2F7/2 transition of Yb3+. The photoluminescence (PL) intensity and PL lifetime increased with increasing calcination temperature, because of the improved crystallinity of Y2O3:Bi3+,Yb3+. The photostability of the nanosheets was evaluated by measuring the change in PL intensity under continuous irradiation by near-ultraviolet light for 2 h. The PL intensity of the nanosheets increased therein, possibly because of photooxidation by ambient oxygen of bismuth or ytterbium ions that were reduced during the solvothermal reaction.