fig6
Figure 6. TEM images of α- (A-B) and β- (C-D) NaErF4 core (A, C) and NaErF4@NaYF4 core-shell (B, D) nanoparticles. The size distribution histograms are shown in the insets. The size for elongated α-NaErF4@NaYF4 nanoparticles is represented by the shorter axes.
