Vanadia/silica xerogels and nanocomposites

Vanadia–silica xerogels: optical and structural properties

“…Stiegman et al, reported the presence of vanadyl ion in vanadia-silica samples, when the starting material was oxovanadium alkoxide [9]. They also reported the color change exhibited by vanadia doped silica systems upon adsorption of water and other molecules [9]. Earlier, we have also established the stabilization of vanadium as vanadyl ion in vanadia-silica xerogels starting from NH 4 VO 3 , a pentavalent inorganic source of vanadium [15].…”

“…Considerable attention has been focused on the synthesis of vanadia-silica mixed gels, glasses and oxides from various organic precursors such as vanadium (V) oxide-triisopropoxide, vanadium tert-butoxy orthosilicate, vanadyl acetyl acetonate etc. [9][10][11][12][13][14]. The spectroscopic evidences from these studies mainly established the presence of essentially the pentavalent vanadium.…”

“…The spectroscopic evidences from these studies mainly established the presence of essentially the pentavalent vanadium. Stiegman et al, reported the presence of vanadyl ion in vanadia-silica samples, when the starting material was oxovanadium alkoxide [9]. They also reported the color change exhibited by vanadia doped silica systems upon adsorption of water and other molecules [9].…”

Effect of surface hydroxylation on the catalytic activity of a Cr(II)/SiO2 model system of Phillips catalyst

“…Although the method does not fully guarantee that residual nearby Cr(II) sites can still be present, it ensures that their contribution is minimal. Transparent silica xerogels of high surface area, produced through a sol-gel process, were already employed as hosts for transition metal ions [7]. Recently, we demonstrated that mesoporous Cr/SiO 2 monoliths are good models for the industrial Phillips catalysts, with the additional advantage to increase of some order of magnitude the sensitivity of characterization techniques, such as UV-Vis and FT-IR spectroscopies of adsorbed species [8].…”

Behavior of copper ions in silica xerogels

“…Introducing transition metal into hydrolyzable precursors through sol-gel methods permits the formation of numerous novel materials that exhibit important optical and/or catalytic functions [1][2][3][4][5][6][7]. Cu or Cu oxides in oxide matrices have attracted sustained interest due to their unusual properties.…”