Behavior of copper ions in silica xerogels

Various concentrations of copper were introduced into tetraethoxyorthosilicate (Si(OC2H5)(4)) based xerogels by CuSO4 solutions. After ambient drying and different thermal treatments, samples were characterized by gas adsorption, atomic adsorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The behavior of Cu cations during aging and subsequent heating was deduced. Based on the experimental data, no direct metal-oxygen-silicon bonds were found in Cu concentrations up to 2000 ppm. After heating at 600 degreesC for 3 h, copper was observed as dispersed Cu ions and Cu polycrystals. (C) 2004 Elsevier B.V. All rights reserved.