Sub-10 nm Hexagonal Lanthanide-Doped NaLuF₄ Upconversion Nanocrystals for Sensitive Bioimaging in Vivo

Abstract

By thermal decomposition in the presence only of oleylamine, sub-10 nm hexagonal NaLuF(4)-based nanocrystals codoped with Gd(3+), Yb(3+), and Er(3+) (or Tm(3+)) have been successfully synthesized. Sub-10 nm β-NaLuF(4): 24 mol % Gd(3+), 20 mol % Yb(3+), 1 mol % Tm(3+) nanocrystals display bright upconversion luminescence (UCL) with a quantum yield of 0.47 ± 0.06% under continuous-wave excitation at 980 nm. Furthermore, through the use of β-NaLuF(4):Gd(3+),Yb(3+),Tm(3+) nanocrystals as a luminescent label, the detection limit of <50 nanocrystal-labeled cells was achieved for whole-body photoluminescent imaging of a small animal (mouse), and high-contrast UCL imaging of a whole-body black mouse with a penetration depth of ~2 cm was achieved.

Upconversion fluorescence resonance energy transfer—a novel approach for sensitive detection of fluoroquinolones in water samples

“…The method was mainly based on the previously reported works [39,42]. Typically, a mixture of PAA (0.5 g) and DEG (10 mL) was heated at 110°C under vigorous stirring (500 rpm) for 10 min.…”

“…The entire content was centrifuged to obtain the final precipitate of Ab-UCNP. The precipitate was washed thrice with distilled water and dispersed in 1 mL HEPES buffer for further usage [39].…”

“…The OA-capped hydrophobic UCPs were functionalized using PAA-based ligand exchange strategy instead of the conventional SiO 2 encapsulation of hydrophobic nanocrystals [39,51]. The role of PAA was to replace monodentate OA shell on UCP surfaces by its multidentate binding sites.…”

“…In the present work, a highly monodisperse and uniform UCPs were synthesized, and the surface was modified into biocompatible by adopting the poly(acrylic acid) (PAA)-based ligand exchange strategies [36,39]. The UCPs were made as an energy donor after their surface functionalization with a group-specific Mab against FQs.…”

Recent advances in the optimization and functionalization of upconversion nanomaterials for in vivo bioapplications

“…24 To date, the upconversion quantum efficiency of small-size UCNPs has been reported to be o1%. 25,26 To solve these problems, new materials are being designed to reduce the possibility of nonradiative transition, enhance the absorption of the sensitizers or use a combination of these methods to improve the upconversion efficiency of UCNPs.…”