Synthesis, phase structure and up-conversion luminescence of NaYF4:Yb3+, Er3+/Tm3+ nanorods

Upconversion luminescent NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were successfully synthesized via a facile and one-pot solvothermal method using oleic acid/oleylamine (OA/OM) as surfactants. The effects of synthetic parameters including rare earth ion doping concentrations and temperatures on the crystal phase structure, size and shape of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were systematically investigated. By modulating the synthetic parameters, the shape of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals were controlled in forms of nanorods and nanowires. The reaction temperature has large effects on the phase structure of NaYF4:Yb3+, Er+/Tm3+ nanorods, exhibiting a phase transformation from cubic phase (alpha-) in low temperatures to hexagonal phase (beta-) in high temperatures. Moreover, the upconversion luminescence of NaYF4:Yb3+, Er3+/Tm3+ nanocrystals was found to be dependent on the rare earth ion doping concentrations and temperatures.