Controlled synthesis of lanthanide-doped NaYF4 upconversion nanocrystals via ligand induced crystal phase transition and silica coating
نویسندگان
چکیده
Upconversion nanocrystals NCs of NaYF4:Yb,Ln Ln=Er and Tm in cubic and hexagonal phases were synthesized in oleic acid OA and/or trioctylphosphine TOP with octadecene ODE via a thermolysis method. Only cubic-phase NCs were obtained in OA/ODE and TOP/ODE solvents; on the other hand, the hexagonal-phase NCs resulted in OA/TOP/ODE. The phase transition from cubic to hexagonal was induced by a ligand formed between oleate and TOP at high temperature. Moreover, the addition of OA/TOP in high and low ratios produced hexagonal nanoparticles and nanorods, respectively. The formed NCs were coated by SiO2 using microemulsion reactions for further biofunctionalization in biological applications. © 2007 American Institute of Physics. DOI: 10.1063/1.2783476
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