In:
Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 68, No. 17 ( 2019), p. 174204-
Abstract:
A series of the hexagonal-phase NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉/12.0% Ce〈sup〉3+〈/sup〉@NaLuF〈sub〉4〈/sub〉:〈i〉x〈/i〉%Yb〈sup〉3+〈/sup〉 core-shell (CS) nanocrystals with codoping different Yb〈sup〉3+〈/sup〉 ions in the shell is successfully built by a sequential growth process. The crystal structures and morphologies of samples are characterized by X-ray diffractometer and transmission electron microscope. With the Yb〈sup〉3+〈/sup〉 ion concentration increasing from 0% to 15% in NaLuF〈sub〉4〈/sub〉 shell, none of the crystal structures, sizes, and morphologies of the samples changes obviously because of the similarity in ionic radius between Yb〈sup〉3+〈/sup〉 and the ions in shell and the low doping concentration. Under 980 nm near-infrared (NIR) excitation, the NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉 core nanocrystal produce green and red UC emission. And the red UC emission intensity is higher than green emission intensity. This is because two effective cross-relaxation processes happen between Ho〈sup〉3+〈/sup〉 and Ce〈sup〉3+〈/sup〉 ions, which results in the enhancement of the red emission. However, the overall emission intensity of NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉 nanocrystal decrease compared with that of the NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉 nanocrystal. Thus, to further enhance the red UC emission intensity in NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉 nanocrystal, the NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0% Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉@NaLuF〈sub〉4〈/sub〉:〈i〉x〈/i〉%Yb〈sup〉3+〈/sup〉 CS nanocrystal are prepared for blocking the excitation and emission energy, transmitting surface quenching center and getting more excitation energy through doping Yb〈sup〉3+〈/sup〉 ions in NaLuF〈sub〉4〈/sub〉 shell. It can be clearly seen that the red UC emission intensity of CS nanocrystal first increases and then decreases with Yb〈sup〉3+〈/sup〉 ion concentration increasing. Meanwhile, the corresponding red-to-green ratio increases from 4.9 to 5.6. The highest red UC emission intensity is observed in each of the NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉 /2.0%Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉@NaLuF〈sub〉4〈/sub〉:10%Yb〈sup〉3+〈/sup〉 CS nanocrystal because the Ho〈sup〉3+〈/sup〉 ions get more energy through the following three ways: 1) Yb〈sup〉3+〈/sup〉 (core)-Ho〈sup〉3+〈/sup〉 (core); 2) Yb〈sup〉3+〈/sup〉 (shell)-Ho〈sup〉3+〈/sup〉 (core); 3) Yb〈sup〉3+〈/sup〉 (shell)-Yb〈sup〉3+〈/sup〉 (core)-Ho〈sup〉3+〈/sup〉 (core). Thus, building CS nanocrystals is one of the most effective approaches in order to improve the UC efficiency by suppressing the non-radiative decay of activators in the core and getting more excitation energy through different energy transfer ways. These NaLuF〈sub〉4〈/sub〉:20.0%Yb〈sup〉3+〈/sup〉/2.0%Ho〈sup〉3+〈/sup〉/12.0%Ce〈sup〉3+〈/sup〉@NaLuF〈sub〉4〈/sub〉:Yb〈sup〉3+〈/sup〉 CS nanocrystals with red UC emission have great potential applications in biological field and multi-primary color.
Type of Medium:
Online Resource
ISSN:
1000-3290
,
1000-3290
DOI:
10.7498/aps.68.20190441
Language:
Unknown
Publisher:
Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
Publication Date:
2019
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