Synthesis and Characterization of Halogen-free, Transparent, Aqueous Colloidal Titanate Solutions from Titanium Alkoxide

Transparent, aqueous colloidal titanate solutions were prepared by a reaction between titanium alkoxide and alkylamines or tetraalkylammonium hydroxides. The chemical species containing titanium atoms were found to be a colloidal particle (15 nm) with a layered structure. The formation reaction can be explained as an acid−base reaction between the amines and titanic acid derived from the alkoxide to yield ammonium titanates. Both the basicity of the amines and the sizes of the conjugate acid (ammonium cations) are crucial factors to determine whether the aqueous solutions can be prepared. Similarly, aqueous oxo metalate solutions of V, Nb, Ta, Al, Si, and Sn are easily prepared from corresponding alkoxides.