Nanometric oxides from molecular precursors in the presence of starch: Coatings of glass with these oxides in silica sols

Sn, Sn-Sb, Ti, Ce, Zr, Zn, In, In-Sn, and Fe oxides of nanometric size were obtained through the hydrolytic route, starting from molecular precursors in the presence of starch. Gels were treated with alpha-amylase to produce oxide suspensions and starch degradation. Solid oxide products resulted from reaction with H2O2, washing with H2O, and centrifugation of the suspensions. The nanometric size and morphology of crystallites were assessed by x-ray diffractometry, transmission electron microscopy, and, for SnO2, solid-state nuclear magnetic resonance. Product consolidation at,600 degrees C did not produce any noticeable increase in dimensions. Thermal analysis coupled with mass spectrometry of evolved gaseous species showed that glucoside residues remain chemically bonded to the nanoparticles, thus explaining the effective stabilization of crystallite dimensions. Aqueous suspensions of nanopowders were mixed with a silicon tetra-ethoxide ethanol solution and subjected to an ordinary sol-gel process. The resulting suspensions were used to obtain stable and homogeneous coatings on glass sheets.