Microstructure and environment dependence of 2H11/2→4I15/2 upconversion emission in YVO4: Er3+, Yb3+ nanocrystals

Upconversion emission of different nanocrystalline YVO4:Er3+, Yb3+ synthesized by a hydrothermal process at low temperature was studied under 980 nm excitation where green [(H-2(11/2), S-4(3/2))-> I-4(15/2)] and red (F-4(9/2)-> I-4(15/2)) emissions demonstrate sensitivity to the local environments of Er3+. Small particle size, high Yb3+ concentration, or high temperature favors the emission of the H-2(11/2)-> I-4(15/2) transition. Both XRD patterns and Raman spectra have confirmed that crystal lattice distortion of YVO4:Er3+, Yb3+ nanocrystals is more serious when the nanoparticle size is decreasing or Yb3+ concentration is increasing. This distortion is thought to play a key role in the observed spectral properties, which might lead to a new route to improve the monochromatic upconversion emission efficiency in these nanocrystals.