Upconversion luminescence in BaYF5, BaGdF5 and BaLuF5 nanocrystals doped with Yb3+/Ho3+, Yb3+/Er3+ or Yb3+/Tm3+ ions

Nanomaterials based on BaREF5 fluorides (where RE = Y, Gd and Lu), doped with lanthanide ions Yb3+/Ln(3+) (Ln(3+) = Er, Ho or Tm) were synthesized by microwave assisted hydrothermal method. The method of synthesis, structural and morphological properties are reported and discussed. The products obtained showed visible upconversion luminescence excited by the laser light of wavelength of 975 nm as a consequence of energy transfer between Yb3+ and remaining Ln(3+) dopant ions. Their spectroscopic properties were characterized on the basis of excitation and emission spectra. Also luminescence decays and emission power dependences are presented and analysed. The materials compared revealed differences in their structural properties, reflected in their spectroscopic characteristics. The most intense luminescence was recorded for BaLuF5 based materials which exhibited upconversion also as water colloids. (C) 2015 Elsevier B.V. All rights reserved.