光子功能材料与器件研究室知识库

The upconversion efficiency could be affected by Li+ ions with changing the local crystal field of nanoparticles. Therefore, a series of NaGdF4:Yb3+/Tm3+ micro-particles with different Li+ doping concentrations were synthesized and investigated, respectively. The structure and morphology of the synthesized materials were tested by X-ray diffraction and scanning electron microscope. The photoluminescence properties were studied with different concentrations Li+ ions doping under the irradiation of 980 nm laser. The emission peaks of Tm3+ ions are 449, 477, 645, 723, 800 nm which are attributed to high excited states to ground state 3H6 transition through a multiple steps resonance energy transfer from excited Yb3+. The enormous increase in upconversion emission in upconversion micro-particles (UCMPs) by introducing Li+ ions was observed by the naked eye. The strongest photoluminescence intensity is the sample with 2.5% doped Li+ ions. Additionally, the practicality of the resultant UCMPs for photoluminescence visible imaging was systematically investigated. These results suggest that the Li+ doped NaGdF4: Yb3+/Tm3+ is very promising as a screen printing material for anti-counterfeiting recognition. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.