Abstract

Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF₄:Yb³⁺/Eu³⁺, a series of NaYF₄:Yb³⁺/Eu³⁺ micro-particles with different Li⁺ doping concentrations were synthesized by the hydrothermal synthesis method, respectively. Firstly, the structure and morphology of NaYF₄:Yb³⁺/Eu³⁺ upconversion micro-particles (UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope (SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li⁺ concentrations of NaYF₄:Yb³⁺/Eu³⁺. X-ray diffraction shows that the crystal field around Eu³⁺ changes with the increase of Li⁺ concentration. Then, the fluorescence spectrum of NaYF₄:Yb³⁺/Eu³⁺ was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF₄:Yb³⁺/Eu³⁺ with 2% Li⁺ is the strongest, which is twice the intensity of NaYF₄:Yb³⁺/Eu³⁺ without Li⁺. Finally, the fluorescence imaging analysis of NaYF₄:Yb³⁺/Eu³⁺ with 2% Li⁺ concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF₄:Yb³⁺/Eu³⁺ (with 2% Li⁺) has great application prospects in anti-counterfeiting recognition.

© 2020 Chinese Laser Press

Tunable concentration-dependent upconversion and downconversion luminescence in NaYF₄: Yb³⁺, Er³⁺@ NaYF₄: Yb³⁺, Nd³⁺ core-shell nanocrystals for a dual-mode anti-counterfeiting imaging application

Shaobo Cui, Li Tao, Wen Kiat Chan, Donglei Zhou, Zhongzheng Yu, and Wen Xu
Opt. Lett. 47(11) 2814-2817 (2022)

Effect of EDTA on the formation and upconversion of NaYF₄:Yb³⁺/ Er³⁺

Ruisen Zhou and Xia Li
Opt. Mater. Express 6(4) 1313-1320 (2016)

Upconversion emissions from high-energy states of Eu³⁺ sensitized by Yb³⁺ and Ho³⁺ in β-NaYF₄ microcrystals under 980 nm excitation

Lili Wang, Zhenyu Liu, Zhe Chen, Dan Zhao, Guanshi Qin, and Weiping Qin
Opt. Express 19(25) 25471-25478 (2011)

3D printing of resin composites doped with upconversion nanoparticles for anti-counterfeiting and temperature detection

Rongping Ni, Bin Qian, Chang Liu, Xiaofeng Liu, and Jianrong Qiu
Opt. Express 26(19) 25481-25491 (2018)

Enhanced upconversion of NaYF₄:Er³⁺/Yb³⁺ phosphors prepared via the rapid microwave-assisted hydrothermal route at low temperature: phase and morphology control

Sudipta Som, Subrata Das, Che-Yuan Yang, and Chung-Hsin Lu
Opt. Lett. 41(3) 464-467 (2016)