Water-Soluble Ln(3+)-doped LaF(3) nanoparticles: retention of strong luminescence and potential as bio-labels

The use of optically robust, luminescent lanthanide-based particles is becoming an area of interest for bio-label-related chemistry, due to their long lifetimes and range of non-overlapping absorption and emission lines from the visible to the near-infrared. We report the synthesis and optical properties of water-soluble, luminescent Ln(3+)-doped nanoparticles (NPs) coordinated with a hydrophilic (RO)PO(3) (2-) ligand that facilitates the stabilization of the NPs in aqueous conditions, and that regulates particle growth to the nanometer range. The use of lanthanide ions as dopants, in particular Eu(3+) and Er(3+) ions, yields optically robust particles with narrow emission lines in the visible (591 nm) and in the near-infrared (1530 nm), respectively. Luminescent lifetimes range from the microsecond to the millisecond for Er(3+) and Eu(3+) ions, respectively, and the NPs are not expected to be susceptible to photo-bleaching due to the fact that the emissions arise from intra-4f transitions of the lanthanide ions.

Bright White Light through Up-Conversion of a Single NIR Source from Sol−Gel-Derived Thin Film Made with Ln3+-Doped LaF3 Nanoparticles

White light was generated from a single silica thin film made with Yb0.75La0.2Eu0.05F3, La0.45Yb0.5Er0.05F3, and La0.75Yb0.2Tm0.05F3 nanoparticles by exciting with a single source near-infrared light (980 nm CW diode laser). Eu3+ and Tm3+ ions are responsible for red and blue emission, respectively. Er3+ ion is responsible for green as well as red emission. The Commission Internationale de l'Eclairage (CIE) coordinates of the resulting light were easily adjusted by controlling the concentration of Ln3+ (Eu3+, Er3+, Tm3+) ions in the nanoparticles as well as the concentration of Ln3+-doped nanoparticles in the sol-gel thin layer.

Colloidal nanoparticles of Ln3+-doped LaVO4: energy transfer to visible- and near-infrared-emitting lanthanide ions

Colloidal, organic solvent-soluble Ln3+-doped LaVO4 nanoparticles have been synthesized by a precipitation reaction in the presence of (C18H37O)2PS2- as ligand, that coordinates to the surface of the nanoparticles. The materials are well soluble in chlorinated solvent such as chloroform. Energy transfer of excited vanadate groups has been observed for Ln3+ ions that emit in the visible and the near-infrared (Eu3+, Tm3+, Nd3+, Er3+, Ho3+, Dy3+, Sm3+, Pr3+), thus making it a very generic sensitization mechanism. The LaVO4 nanoparticles have a different crystal structure than bulk LaVO4 ones (xenotime instead of monazite), similar to YVO4 nanoparticles. This xenotime crystal structure results in a more asymmetric crystal field around the Ln3+ ions that is advantageous to their luminescence, for it increases the radiative rate constant, thus reducing quenching processes.