In situ quantitative study of the phase transition in surfactant adsorption layers at the silica–water interface using total internal reflection Raman spectroscopy

Abstract

Dimethyldodecylamine N-oxide (DDAO) shows high surface activity with two distinct energy states at the hydrophilic silica/aqueous solution interface studied by total internal reflection (TIR) Raman spectroscopy combined with ratiometric and kinetic analysis.

Cooperative Adsorption of Nonionic Triton X-100 and Dodecyldimethylamine Oxide Surfactant Mixtures at the Hydrophilic Silica–Water Interface Studied by Total Internal Reflection Raman Spectroscopy and Multivariate Curve Resolution

“…The light scattering measurement was calibrated against pure water and the aqueous micellar CTAB solution at 1.0 mM in the Supporting Information of previous work. 12 The aqueous CTAB solution has the cmc value of ∼0.9 mM at ambient conditions. 16 Tyrode et al 17 executed the adsorption experiment of CTAB at the silica−water interface using TIR-Raman spectroscopy.…”

“…As a result, both the TIR-Raman integrations and the light scattering photon counts increased when pure water was replaced by the 1.0 mM CTAB aqueous solution. 12 An increase in surfactant concentration led to a linearly proportional increase in the scattering intensity because the surface coverage was saturated, and the contribution from the bulk became significant.…”

“…The procedure for cleaning fused silica prism, glassware, Teflon components, Raman cell, and turbidity cell was detailed in the previous paper. 12 All solutions were prepared in a nitrogen-filled glovebox because DDAO is highly hygroscopic. A background spectrum with the laser blocked and another background spectrum for pure water were acquired before introducing the solution sample into the flow system.…”

“…9,10 On the other hand, a small amount of dimethyldodecylamine (DDAO) significantly enhances the adsorption of dodecyl maltoside (C12E6) on the silica surface. 11 Interesting adsorption behaviors of the DDAO surfactant on silica surface under the flow condition have been explored in the previous study, 12,13 showing high surface activity at the silica− water interface by forming a dense and more ordered liquidcrystalline adsorbed layer. 12 Mixing the DDAO solution with a nonionic surfactant, e.g., Triton X-100 (TX), typically shows a negligible synergetic effect in the bulk solution.…”

“…11 Interesting adsorption behaviors of the DDAO surfactant on silica surface under the flow condition have been explored in the previous study, 12,13 showing high surface activity at the silica− water interface by forming a dense and more ordered liquidcrystalline adsorbed layer. 12 Mixing the DDAO solution with a nonionic surfactant, e.g., Triton X-100 (TX), typically shows a negligible synergetic effect in the bulk solution. 10,14 However, as in the mixture with the DDAO surfactant, the nonionic species is expected to have its adsorption on the silica surface drastically enhanced (Figure 1).…”