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Highly Bright and Photostable Li(Gd,Y)F 4 :Yb,Er/LiGdF 4 Core/Shell Upconversion Nanophosphors for Bioimaging Applications
Author(s) -
Shin Jeehae,
Kim Youngsun,
Lee Jiyeon,
Kim Sehoon,
Jang Ho Seong
Publication year - 2017
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.201600183
Subject(s) - luminescence , photon upconversion , materials science , tetragonal crystal system , chemistry , optoelectronics , crystallography , crystal structure
Intense green‐emitting Li(Gd,Y)F 4 :Yb,Er/LiGdF 4 core/shell (C/S) upconversion nanophosphors (UCNPs) with a tetragonal bipyramidal morphology are synthesized. The morphology and UC luminescence of the Li(Gd,Y)F 4 :Yb,Er UCNPs are significantly affected by the Li precursors, and bright UC green‐emitting Li(Gd,Y)F 4 :Yb,Er UCNPs with a tetragonal bipyramidal shape, i.e., UC tetragonal bipyramids (UCTBs), are synthesized using LiOH·H 2 O as a Li precursor. A LiGdF 4 shell is grown on the Li(Gd,Y)F 4 :Yb,Er UCTBs, and the C/S UCNPs exhibit 4.7 times higher luminescence intensity than core UCTBs. The C/S UCNPs show a high absolute UC quantum yield of 4.6% under excitation with 980 nm near infrared (NIR) light, and the UC luminescence from the C/S UCNPs is stable under continuous irradiation with the 980 nm NIR laser for 1 h. The hydrophobic surfaces of the as‐synthesized C/S UCNPs are modified to hydrophilic surfaces by using poly(acrylic acid) (PAA) for bioimaging applications. They are applied to human cervical adenocarcinoma (HeLa) cell imaging and SK‐MEL‐2 melanoma cell imaging and in vivo imaging, including subcutaneous and intramuscular imaging, and UC luminescence images with high signal‐to‐noise ratio are obtained. Furthermore, sentinel‐lymph‐node imaging is successfully conducted with the PAA‐capped Li(Gd,Y)F 4 :Yb,Er/LiGdF 4 C/S UCNPs under illumination with NIR light.