Optical spectroscopy and visible upconversion studies of YVO4:Er3+ nanocrystals synthesized by a hydrothermal process

Strong visible emissions of Er3+ resulting from two-photon absorption and energy transfer from the host YVO4 were observed in nanocrystalline Er3+-doped YVO4, which was prepared by a hydrothermal method using a citrate-yttrium-vanadate complex as the precursor. The nanocrystals were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV-visible absorption spectra, and photoluminescence (PL) spectra. The highly crystalline YVO4: Er3+ nanoparticles, with an average diameter of 35 nm, have a tetragonal zircon structure and can redisperse in water because of the presence of citrate ligands. We discussed in detail the visible upconversion mechanism and temperature dependence of the upconversion emission for the Er3+ ions in the YVO4 nanocrystals.