Use of Infrared Bands of the Surfactant Headgroup to Identify Mixed Surfactant Structures Adsorbed on Titania

Abstract

Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was used to identify the mixed surfactant structures formed on charged TiO 2 particles. Cetyltrimethylammonium bromide (CTAB) was first added to a bare TiO 2 surface at three different solution concentrations that result in adsorbed hemimicelle, admicelle, or micelle structures. Each CTAB structure was then probed as a function of contact time with a solution containing the deuterated form of the anionic surfactant, sodium dodecyl sulfate (SDS). While the amount of CTAB and SDS was determined from the intensity of the strong CH 2 and CD 2 stretching modes, it is the headgroup bands that provide the important structural information on the mixed surfactant architectures. By measuring the changes in the headgroup bands for both SDS and CTAB along with the change in the adsorbed amount of each surfactant as a function of time, a clearer picture emerges of the mixed surfactant structures formed on the surface.