Playing Favorites: Preferential Adsorption of Nonionic over Anionic Surfactants at the Liquid/Liquid Interface.

While many studies have investigated synergic interactions between surfactants in mixed systems, understanding possible competitive behaviors between interfacial components of binary surfactant systems is necessary for the optimized efficacy of applications dependent on surface properties. Such is the focus of these studies in which the surface behavior of a binary surfactant mixture containing nonionic (Span-80) and anionic (AOT) components adsorbing to the oil/water interface was investigated with vibrational sum-frequency (VSF) spectroscopy and surface tensiometry experimental methods. Time-dependent spectroscopic studies reveal that while both nonionic and anionic surfactants initially adsorb to the interface, anionic surfactants desorb over time as the nonionic surfactant continues to adsorb.

Assessing the Impact of Solvent Selection on Vibrational Sum-Frequency Scattering Spectroscopy Experiments.

The development of vibrational sum-frequency scattering (S-VSF) spectroscopy has opened the door to directly probing nanoparticle surfaces with an interfacial and chemical specificity that was previously reserved for planar interfacial systems. Despite its potential, challenges remain in the application of S-VSF spectroscopy beyond simplified chemical systems. One such challenge includes infrared absorption by an absorptive continuous phase, which will alter the spectral lineshapes within S-VSF spectra.