Figure 2 | Scientific Reports

Figure 2

From: Upconversion Modulation through Pulsed Laser Excitation for Anti-counterfeiting

Figure 2

Photoluminescence features of the upconversion nanoparticles. (a–b) The emission spectra of nanoparticles under CW 980 nm diode laser excitation: (a) NaYF4:Er/Tm, NaYF4:Er/Tm@NaYF4 and (b) NaYF4:Er/Tm@NaYF4:Yb; (c) Excitation power density dependence at 541 nm and 654 nm of NaYF4:Er/Tm@NaYF4 nanocrystals under CW 980 nm laser excitation; (d) Proposed energy transfer upconversion mechanism of NaYF4:Er/Tm@NaYF4 nanoparticles.

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