Abstract
In this study, Li-based blue- and green-emitting core@shell (C@S) upconversion nanophosphors (UCNPs) and NaGdF4-based red-emitting C@S UCNPs were synthesized, and IR-808 dyes were conjugated with the C@S UCNPs to enhance upconversion (UC) luminescence. The surface of the as-synthesized C@S UCNPs, which was originally capped with oleic acid, was modified with BF4− to conjugate the IR-808 dye having a carboxyl functional group to the surface of the UCNPs. After the conjugation with IR-808 dyes, absorbance of the UCNPs was significantly increased. As a result, dye-sensitized blue (B)-, green (G)-, and red (R)-emitting UCNPs exhibited 87-fold, 10.8-fold, and 110-fold enhanced UC luminescence compared with B-, G-, and R-emitting Nd3+-doped C@S UCNPs under 800 nm near-infrared (NIR) light excitation, respectively. Consequently, dye-sensitized UCNPs exhibiting strong UC luminescence under 800 nm NIR light excitation have high applicability in a variety of biological applications.
Highlights
Lanthanide-doped upconversion nanophosphors (UCNPs) have been widely used in biological applications owing to their unique features such as large anti-Stokes shift luminescence under invisible near-infrared (NIR) light and non-cytotoxicity [1,2,3,4,5,6,7,8,9]
We synthesized LiREF4 − based blue- and green-emitting C@S UCNPs, and NaGdF4 − based red-emitting C@S UCNPs, where Nd3+ ions were doped in the shell
C@S UCNPs with BF4 −, the C@S UCNPs were successfully conjugated with IR-808 dyes and they were confirmed by FT-IR analysis
Summary
Lanthanide-doped upconversion nanophosphors (UCNPs) have been widely used in biological applications owing to their unique features such as large anti-Stokes shift luminescence under invisible near-infrared (NIR) light and non-cytotoxicity [1,2,3,4,5,6,7,8,9]. Tang’s group reported the results of in vivo upconversion (UC) luminescence/magnetic resonance imaging using. In vitro cell imaging and in vivo imaging were performed with 980 nm NIR light. Under irradiation with 980 nm NIR light for a long time, an overheating problem, that is, the increase of the temperature of the biomolecules, can cause cell death [11]. To solve this problem, many researchers have studied 800 nm-excitable
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