Local atomic structure of lanthanide complexes in cubic ordered mesoporous silica

Abstract

The aim of this work was to analyze the local atomic environment around lanthanide atoms anchored inside silica matrices by means of X-ray absorption spectroscopy (XAS). Europium and cerium complexes were incorporated in cubic FDU-1 and SBA-16 ordered mesoporous silica (OMS) by a post-synthesis method. Small angle X-ray scattering (SAXS) showed the presence of an ordered arrangement of pores for all investigated samples. A much higher Eu incorporation for the dibenzoylmethane complex is attained compared to picrate complex with a weight percent similar to the nominal concentration of Eu, as determined by Rutherford back-scattering spectrometry (RBS). the XAS results showed that the local atomic arrangement around Eu is composed by a first neighbor sphere similar to the complex and different second neighbors compared to pristine material, indicating an interaction of the complexes with the silica walls, in such an extent that it does not interfere on the complexes luminescent properties. the first and second spheres around the incorporated Ce are analogous to the pure cerium picrate complex, showing that the complex is anchored on the porous surface. the solvent does not interfere on the local atomic structure, but on the incorporation capacity. (C) 2013 Elsevier B.V. All rights reserved.