Acknowledgements Authors would like to acknowledge the National Natural Science Foundation of China (NSFC, Grant No. 51361009), the International Joint Project of Hainan Province (Grant No. KJHZ2014-19), the Postgraduate Innovative Project of Hainan Province in 2015 (Grant No. Hys2015-24) and the Postgraduate Practice & Innovation Projects of Hainan University in 2015 for financial support. The Instrumental Analysis Center of Hainan University is also acknowledged here.
In a route boiling water served as reaction medium, a stoichiometric amount of rare-earth compound and fluoride are put into this system to form a-NaYF4:Yb, Er nuclei. Then prepared sample is heated at elevated tempe...