%0 Journal Article
%A Carmona Tejero, Noemí
%A Bouzas, V.
%A Jiménez, F.
%A Plaza, M.
%A Pérez García, Lucas
%A García, M. A.
%A Villegas, M. A.
%A LLopis, J.
%T Cobalt (II) environment characterization in sol-gel thermochromic sensors
%D 2010
%@ 0925-4005
%U https://hdl.handle.net/20.500.14352/42771
%X Optical absorption and magnetic properties of silica sol-gel monoliths doped with cobalt starting from different precursors and water/1-propanol molar ratios are investigated. Structural characterization of the sol-gel by X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy corroborate, that oxidising state of cobalt is Co^(2+). Furthermore, the Co^(2+) first neighbors are O atoms displaying a temperature transition from octahedral to tetrahedral coordination. The doped monoliths show thermochromic sensor activity ranging from 10 to 50⁰ C, which is related to the environment of Co^(2+) ions. The magnetic susceptibility also varies with Co^(2+) ions environment due to changes in the orbital contribution to the magnetic moment. Thus, we achieve a better understanding about environment of the Co^(2+) ions in the gel matrix and explain their       reversible temperature behaviour in spite of the rigid state of the host matrix.
%~