Bright Blue, Green, and Red Luminescence from Dye-Sensitized Core@Shell Upconversion Nanophosphors under 800 nm Near-Infrared Light

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.

Toward Upconversion Luminescence Enhancement with Dye Sensitization

“…(c) Schematic diagram of energy-cascade UC energy-transfer sequence for IR-808 sensitization. Reprinted with permission from ref . Copyright 2020 Multidisciplinary Digital Publishing Institute.…”

“…The UCL integrated emission intensity from 500 to 700 nm was more than 7 times higher than the nonsensitized counterparts. Subsequently, the dye-sensitized lithium-based energy-cascade UCNPs [Li(Gd/Y)F 4 ] resulted in 87-fold (blue), 10.8-fold (green), and 110-fold (red) luminance enhancement, respectively (Figure c) …”

“…This occurs because the excited-state energy of one dye molecule can be transferred to another dye molecule instead of being transferred to the UCNP, leading to a decrease in the luminescence intensity. Therefore, it is important to optimize the number of dyes linked to the UCNP to prevent concentration quenching and maximize the luminescence intensity. , In this case, a unique material AIE material with concentration quenching resistance was proposed, in which the molecules emitted enhanced emission under the aggregation situation . The AIE dye, CyTSO, was synthesized by introducing tetraphene into cyanine dyes .…”

“…Subsequently, the dye-sensitized lithium-based energy-cascade UCNPs [Li(Gd/ Y)F 4 ] resulted in 87-fold (blue), 10.8-fold (green), and 110fold (red) luminance enhancement, respectively (Figure 5c). 36 Additionally, with NIR stimulation, the UCL of IR-808-dyesensitized UCNPs is extremely brilliant, which has significant applications in biological therapy and probing. The IR-808sensitized NaGdF 4 :Yb,Er@NaGdF 4 :Nd,Yb can harvest 808 nm photons and efficiently emit green and red light, with ∼12-fold UCL enhancement.…”

Application and Design of Switches Used in CAR

“…It is worth noting that if the development of biochemical molecules dependent on light of a higher wavelength of molecules would be difficult, it is possible to use UCNPs (upconverting nanoparticles). They have the ability to locally convert infrared light to blue light, a property that eliminates the limitation due to the shallow penetration of UV alone [ 60 ]. Moreover, UCNPs can act specifically in the tumor microenvironment.…”