Influence of anions stabilizing the sols in synthesis of powders of highly dispersed titanium dioxide and three-dimensional nanocomposites based on SiO$_2$/TiO$_2$

This paper reports on the results of investigations into the influence of anions (Cl$^-$, SO$_4^{2-}$, NO$_4^-$), which stabilize the sol-gel synthesis of highly dispersed titanium dioxide, on the crystallization and phase transition of TiO$_2$ upon dehydration. The effect of the size factor on the phase composition of TiO$_2$ in SiO$_2$/TiO$_2$ nanocomposites has been investigated using a three-dimensional opal matrix as a set of nanoreactors for the sol-gel synthesis of TiO$_2$ $\cdot$ $n$H$_2$O. It has been shown that there is a possibility of extending the region of the existence of a thermodynamically metastable modification of TiO$_2$ (anatase) to the temperature of 1100$^\circ$C due to the changes in the conditions of the sol-gel synthesis of TiO$_2$ $\cdot$ $n$H$_2$O.