Solvothermal synthesis and luminescence properties of NaYF4:Ln3+ (Eu3+, Tb3+, Yb3+/Er3+) nano- and microstructures

NaYF4 and NaYF4 (Eu3+, Tb3+, Yb3+/Er3+) nano- and microstructures were successfully synthesized through a facile and effective polyol-mediated route with ethylene glycol (EG) as solvent. The factors including the molar ratio of F−/Y3+, reaction temperature and reaction time were well studied in the influences on size, morphology and phase transition of samples. The experimental results indicate that the F−/Y3+ ratio and reaction temperature play key roles in crystal phase and morphology of the product. Higher molar ratio of F−/Y3+ and higher temperature as well as longer reaction time facilitate α cubic structure-to-β hexagonal structure phase transition, which behaves as a dissolution–recrystallization transformation process. Photoluminescence measurements demonstrated that the as-prepared β-NaYF4 is one good up- and down-conversion luminescent host material.

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► We have demonstrated a polyol-mediated method for NaYF4 nano/microstructure.
► The higher F−/Y3+ ratio favors growth of the bigger hexagonal NaYF4 microcrystals.
► PL of β-NaYF4 is good up- and down-conversion luminescent host materials.