Hydrothermal synthesis of BaYF5:Yb3+/Er3+ upconversion luminescence submicrospheres by a surfactant-free aqueous solution route Original Research Article

BaYF5:Yb3+/Er3+ upconversion (UC) luminescence submicrospheres have been synthesized by the hydrothermal synthesis method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), scanning probe microscope (SPM), transmission electron microscope (TEM), laser diffraction particle analyzer (LDPA) and UC emission spectra. The as-prepared highly crystalline BaYF5:Yb3+/Er3+ submicrospheres are of uniform size depending on different reaction temperatures and reaction times. It is found that the usage of fluoride source NaBF4 plays the crucial key in the formation of submicrosphere. Under the 980 nm excitation, the UC emission transitions for 4F9/2→4I15/2 (red), 2H11/2, 4S3/2→4I15/2 (green) in the BaYF5:Yb3+/Er3+ submicrospheres came from two-, two-, and two-photon UC processes, respectively. Further, the effects of Yb3+ ion concentration, size and surface of as-prepared submicrospheres, and pumping power on the UC luminescence properties of BaYF5:Yb3+/Er3+ have also been discussed.