Colloidal solutions and redispersible powders of nanocrystalline, lanthanide-doped YVO4 have been prepared via a hydrothermal method at 200 °C. High-resolution transmission electron micrographs of size-selected samples show highly crystalline particles ranging in size from about 10 to 30 nm. The particles exhibit the tetragonal zircon structure known for bulk material. Upon UV excitation of the vanadate host, the energy is transferred to the lanthanide ion and strong luminescence (f−f transitions) is observed. By analyzing line splitting and intensity pattern in the luminescence spectrum of the europium-doped sample, we are able to verify that the dopant ions enter the same lattice site as in bulk material despite the nanocrystalline nature of the sample and the low-temperature synthesis. For YVO4:Eu nanoparticles a luminescence quantum yield of 15% at room-temperature was observed.

Wet-chemical synthesis of doped colloidal nanoparticles : yvo4:ln (ln = eu, sm, dy)

This review summarizes recent work in nanostructured insulating materials that contain optically active lanthanide ions. These materials find applications in lasers, optical amplifiers, and optical-display phosphors. This review concentrates on the synthesis and luminescence spectroscopy of lanthanide-containing nanostructured particles, films, and composites. Spectroscopic studies range from basic luminescence spectroscopy and quantum efficiency measurements to high-resolution spectroscopic studies that investigate the phonon dynamics and electron−phonon interaction as a function of particle size. This review identifies several areas for further study, including the location, distribution, or segregation of dopants in nanoparticles; the efficiency of energy transfer across interfaces; and the effects of quantum confinement or changes in phonon dynamics and electron−phonon interactions on the radiative and nonradiative relaxation rates in localized luminescent dopants.

Synthesis and luminescence of lanthanide ions in nanoscale insulating hosts

Eu2O3 nanocrystals are synthesized by a colloidal precipitation route in the size range 2-40 nm. The nanocrystals are passivated with a surface layer of trioctyl phosphine oxide (TOPO) in order to eliminate surface recombination effects. When pumped at 254 nm (4f --> 5d transition) the nanocrystals exhibit red luminescence characteristic of 5D0 --> 7Fn Eu3+ transitions within the cubic form of Eu2O3. The efficiency of the luminescence is increased by a factor of five as the particle size drops below 10 nm; it is suggested that confinement of the long lifetime Eu3+ excitation within the nanocrystal is responsible for this effect. Copyright 1999 Academic Press.

J.-C. Krupa

Papers

Luminescence of nanometric scale Y2SiO5:Eu3+