Upconversion photoluminescence of core-shell structured SiO@YVO:Yb, Er, Eu nanospheres.

Core-shell structured SiO@YVO:Yb, Er, Eu nanospheres were prepared by a simple solgel method followed by a subsequent heat treatment. The as-prepared composites were characterized by a scanning electron microscope, high-resolution transmission electron microscope, x-ray diffraction, and photoluminescence spectra. The influences of different coating numbers were also studied. To sum up, the composites are spherical shaped with an average diameter of 200 nm, and the YVO:Yb, Er, Eu luminescent particles are successfully coated on the surface of SiO nanospheres. Under the near-infrared irradiation at 980 nm, the composites can emit strong green lights (at 525 nm, 550 nm) attributed to the H2→I4, S4→I4 transitions of Er ions, and slight red lights (at 590 nm, 620 nm) attributed to the D5→F7, D5→F7 transitions of Eu ions. Given the above, due to the regular core-shell structure, the uniform distribution of nanoparticles, and the colorful emissions, the SiO@YVO:Yb, Er, Eu nanospheres may have great potential for some biological applications, such as biological tracers, bio-labeling, and so on.