(a)
(b)
(c)
Figure 6: (a) Room temperature upconversion emission spectra of LiGdF4:Yb3+/Er3+ nanocrystals, which are synthesized at and , 2 h, 3 h, 4 h, and 5 h. (b) Room temperature upconversion emission spectra of LiGdF4:Yb3+/Er3+ nanocrystals, which are synthesized at , , and . (c) Log-log plot of power dependence of the upconversion emissions intensity for LiGdF4:Yb3+/Er3+ nanocrystals at , , and .