title: APTES-modified RE2O3:Eu3+ luminescent beads: structure and properties.
abstract: Europium-doped lanthanide oxide RE(2)O(3):Eu(3+) (RE = Y or Gd) luminescent beads, with a spherical shape and a diameter of 150 ± 15 nm, have been modified by reaction with 3-aminopropyltriethoxysilane (APTES), in order to introduce reactive amine groups at their surfaces. The direct silanation has resulted in the formation of a nanometric layer at the surface of the beads, with an optimum grafting rate of 0.055 ± 0.005 mol APTES/mol RE(2)O(3). Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies confirmed the condensation of an organosilane layer, made of cross-linked -O-Si-O-Si- and of groups -O-Si-R (with R = (CH(2))(3)NH(2) or O-Et). Titration of the accessible amine groups has been performed by simultaneously measuring the luminescence of grafted fluorescein isothiocyanate and that of core particles: there are about 2.3 × 10(4) (2.8 × 10(4)) -NH(2) per Y(2)O(3):Eu(3+) (Gd(2)O(3):Eu(3+)) bead. The isoelectronic point was shifted by one pH unit after APTES modification. The surface modification by APTES at least preserved (for Gd(2)O(3):Eu(3+)) or improved (for Y(2)O(3):Eu(3+)) the red emission of the beads.
authors.affiliation: Centre d'Elaboration de Matériaux et d'Etudes Structurales, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Lechevallier
authors.forename: Peter
authors.initials: P
authors.lastname: Hammer
authors.forename: José M A
authors.initials: JM
authors.lastname: Caiut
authors.forename: Serge
authors.initials: S
authors.lastname: Mazeres
authors.forename: Robert
authors.initials: R
authors.lastname: Mauricot
authors.forename: Marc
authors.initials: M
authors.lastname: Verelst
authors.forename: Hervé
authors.initials: H
authors.lastname: Dexpert
authors.forename: Sidney J L
authors.initials: SJ
authors.lastname: Ribeiro
authors.forename: Jeannette
authors.initials: J
authors.lastname: Dexpert-Ghys
mesh_terms: D005063:Europium / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D049449:Luminescence; D011437:Propylamines; D012821:Silanes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D028581:Lanthanoid Series Elements; D011437:Propylamines; D012821:Silanes; D005063:Europium; C477625:amino-propyl-triethoxysilane