Highly Luminescent Composite Films from Core-Shell Oxide Nanocrystals
- PDF / 715,663 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 68 Downloads / 197 Views
DD7.8.1
HIGHLY LUMINESCENT COMPOSITE FILMS FROM CORE-SHELL OXIDE NANOCRYSTALS Valérie Buissette,1 Mélanie Moreau,1 Thierry Gacoin,1 Thierry Le Mercier,² Jean-Pierre Boilot1 1 Groupe de Chimie du Solide, Laboratoire de Physique de la Matière Condensée, CNRS UMR 7643, Ecole Polytechnique, 91128 Palaiseau cedex (France). ² Centre de Recherches d’Aubervilliers, Rhodia, 52, rue de la Haie Coq, 93308, Aubervilliers (France). ABSTRACT Luminescent nanocrystals can find interesting applications for the elaboration of light emitting transparent materials. The work described here is based on the use of lanthanide doped vanadate (YVO4:Eu) and phosphate (La,Ce,Tb)PO4-0,7H2O nanoparticles grown through aqueous colloidal synthesis, with average sizes below 10 nm. The well-dispersed colloids are transparent and respectively exhibit red and green luminescence under U.V. excitation with high luminescence yields (20 – 50 %). Improvement of luminescence properties of the nanocrystals is achieved through the elaboration of core/shell nanostructures, obtained after the growth at the surface of an amorphous silica shell or a crystalline lanthanum phosphate shell. Surface derivatization is further achieved through the controlled growth of an organically modified silica coating using a functionalized silane precursor. Concentrated sols are obtained, which are highly luminescent and well-dispersed. They can be spin-coated on various substrates, leading to perfectly transparent and highly luminescent thin films. Multi-layers films and heating treatments are performed, leading to optimized materials. INTRODUCTION Recently, the study of nanometric luminescent materials has become of great interest.1 Indeed, microstructural characteristics of the phosphors play an important role in the efficiency of luminescent devices, and new developments as electroluminescent devices, integrated optics or biological labels2 imply the design of new phosphors with controlled properties at the nanometric scale. The major part of the work has been focused on semiconductor nanocrystals.3 However, a significant amount of research has been devoted to lanthanide doped nanocrystals,4 but fewer work has focused on the synthesis of well-dispersed particles (yttrium vanadate,5,6 lanthanum fluoride,7 lanthanum phosphate8 and yttrium oxide9 nanoparticles doped with rare earth ions). The basic idea of the work presented here is to explore the potentialities of lanthanide (Ln) doped yttrium vanadate (YVO4) and lanthanum phosphate (LaPO4-xH2O) synthesized through colloidal chemistry. This choice is explained by the excellent luminescence properties of the bulk material: red phosphor for YVO4:Eu and green phosphor for (La,Ce,Tb)PO4. In a first part, the synthesis process, the structural and luminescence properties of the two nanocrystalline systems are described. Then, we report on the synthesis of nanocomposite materials in which the nanocrystals are dispersed in a transparent sol-gel matrix. EXPERIMENTAL SECTION • Synthesis of the aqueous colloidal suspensions The synthesis
Data Loading...
