Deposition mechanism of anatase TiO2 on self-assembled monolayers from an aqueous solution

The nucleation and growth process of anatase TiO2 on several kinds of self-assembled monolayers (SAMs) in an aqueous solution has been evaluated in detail. Homogeneously nucleated TiO2 particles and amino groups of SAM showed negative or positive zeta potential in the solution, respectively. The adhesion of TiO2 particles to the amino group surface by attractive electrostatic interaction caused rapid growth of TiO2 thin films in the supersaturated solution at pH 2.8. On the other hand, TiO2 was deposited on SAMs without the adhesion of TiO2 particles regardless of the type of SAM in the solution at pH 1.5 whose degree of supersaturation is low as a result of a high concentration of H+. Additionally, the orientation of films deposited on all SAMs was shown to be improved by enlarging the reaction time regardless of the kind of SAM or pH. It is conjectured that the adsorption of anions to specific crystal planes caused c-axis orientation of anatase TiO2.