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. 2018 May 24;2(3):243–257. doi: 10.7150/ntno.25901

Figure 2.

Figure 2

(A) Up-conversion emission spectra of the core NaYF4:Yb,Er NPs (green), the core-shell NaYF4:Yb,Er@NaYF4:Yb NPs (blue), and the core-shell-shell NaYF4:Yb,Er@NaYF4:Yb@NaYF4: Yb,Nd UCNPs (red); λex = 980 nm, 1 mg/mL in n-hexane. (B) Up-conversion emission spectrum of NaYF4:Yb, Er@NaYF4:Yb@NaYF4:Yb,Nd core-shell-shell UCNPs (λex = 793 nm, 1 mg/mL in n-hexane; inset: photograph of the sample solution). (C) Down-conversion emission spectrum (λex = 793 nm, 1 mg/mL in n-hexane) and excitation spectrum (λem= 980 nm, inset) of NaYF4:Yb,Er@ NaYF4:Yb@ NaYF4:Yb,Nd UCNPs.