Phase transformation and morphology tuning of β-NaYF4:Yb3+,Er3+ nanocrystals through K+ ions codoping*
Liang Zhi-Qina),b), Zhao Su-Linga),b)†, Cui Yuea),b), Tian Li-Jiaoa),b), Zhang Jun-Jiea),b), Xu Zhenga),b)
       
(a) UC emission spectra of the samples with different concentrations of K+ ions. All of them are measured under the same conditions. (b) Red-to green (R/G) emission ratios as a function of the content of K+ ions.