Adhesion of Sodium Dodecyl Sulfate Surfactant Mono layers with TiO2 (Rutile and Anatase) Surfaces

Surfactants are widely used as templates to control the nucleation and growth of nanostructured metal oxides such as titania. To gain insight into the origin of the surfactant-titania interactions responsible for polymorph and orientation selection, we simulate the self-assembly of an anionic surfactant monolayer on various low-index titania surfaces, for a range of densities. We characterize the binding in each case and compute the adhesion energies, finding anatase (100) and rutile (110) to be the strongest-binding surfaces. The sodium counterions in the monolayer are found to dominate the adhesion. It is also observed that the assembly is directed predominantly by surface-monolayer electrostatic complementarity. Incorporating water displacement into the calculations does not alter the general findings but does cause the adhesion energies to fall within a smaller range.