Cobalt (II) environment characterization in sol-gel thermochromic sensors



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Carmona Tejero, Noemí and Bouzas, V. and Jiménez, F. and Plaza, M. and Pérez García, Lucas and García, M. A. and Villegas, M. A. and LLopis, J. (2010) Cobalt (II) environment characterization in sol-gel thermochromic sensors. Sensors and actuators B - chemical, 145 (1). pp. 139-145. ISSN 0925-4005

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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.

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©2009 Elsevier B.V. All rights reserved.
Authors wish to thank XAFS Beamline BM25 (Spanish-SPLine CRG) at the European Synchrotron Radiation Facilities, ESRF (Grenoble, France). The funding of the EU project “BONSAI” LSHB-CT-2006-037639. NC acknowledges the financial support of the FSE-MEC, Ramón y Cajal program ref. RYC-2007-01715.

Uncontrolled Keywords:Magnetic-properties; Films; Nanoparticles; Temperature; Absorption; Glasses
Subjects:Sciences > Physics > Materials
Sciences > Physics > Solid state physics
ID Code:45433
Deposited On:15 Nov 2017 19:51
Last Modified:13 Jun 2018 12:05

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