Figure 5

(a,b) SEM images of the as-prepared α-NaYF₄ and α-NaYF₄:5%Er³⁺ nanocrystals. (c) SAED pattern, (d) HRTEM image and (e) EDS spectrum of as-prepared α-NaYF₄:5%Er³⁺ nanocrystals, respectively. The insert in (b) is TEM image of a single α-NaYF₄:5%Er³⁺ nanocrystal.