Hydrothermal synthesis and photoluminescence of host sensitized Yb2O3: Ho3+ nanorods

Ho3+ doped Yb2O3 upconverstion (UC) luminescent nanorods have been prepared using a simple hydrothermal method followed by an annealing treatment. The as-prepared samples were investigated by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectra for their structural, morphologic and UC luminescent properties. The XRD patterns indicate that all samples are crystallized in the cubic phase of Yb2O3. SEM images reveal that the samples have a rod-shape morphology with the length ranging from 0.5 to 1.0 μm and the diameter ~100 nm. Under 980 nm excitation, the as-obtained nanorods exhibit bight orange emission which is attributed to the characteristic transitions of 5F4, 5S2 → 5I8, 5F5 → 5I8 and 5F4, 5S2 → 5I7 of Ho3+ ion, respectively. The UC emission intensity initially increases as Ho3+ contents increase, reaching a maximum at 2.0 mol%, and then decreases due to the concentration quenching effect. The possible UC mechanisms and energy transfer process were also discussed.