Preparation and optical properties of silica gels doped with a new Eu(III) complex

The preparation and incorporation in silica gels of a novel europium complex, [Eu(ntac)(3)][pphendcn] containing 4,4,4-trifluoro-1-(naphthalene-2-yl) butan-1,3-dione (Hntac) and pyrazino[2,3-f][1,10-phenathroline-2,3-dicarbonitrile (pphendcn) is demonstrated. An effective energy transfer from the organic ligands to the Eu(III) ions leads to a strong f-f luminescence even at low activator concentrations, n(Eu)/n(si) approximate to 1 x 10(-5). The new amorphous materials are characterized by UV/Vis reflectance and transmission spectroscopy, luminescence/excitation spectroscopy, X-ray diffraction, elemental analysis, IR spectroscopy, DTA/TG and NMR. The optical properties of gels with a different Eu(III) doping are discussed. The stability of the europium complex in the silica matrix during time (up to 4 months) and after heating is discussed. The Eu(III) spectra-structure correlation is used to characterize the site symmetry of the activator. (C) 2011 Elsevier B.V. All rights reserved.