Synthesis and Application in Anticounterfeiting of RGB Upconversion Nanoparticles

Figure 4

(a) The upconversion spectrum of (a) KMnF₃:18%Yb³⁺,1%Er³⁺ NPs, (b) NaYF₄:18%Yb³⁺,0.5%Tm³⁺ NPs, and (c) NaYF₄:18%Yb³⁺,2%Er³⁺ NPs in 980 nm excitation. Embedded in every figure is the picture of the corresponding NP cyclohexane solution without or with 980 nm excitation. (d) The CIE color coordinates of the NPs.

(a)

(b)

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(d)