Abstract
It is important to investigate the influence of surfactants on structures and physical/chemical properties of oil/water interfaces. This work reports a second harmonic generation study of the adsorption of malachite green (MG) on the surfaces of oil droplets in a hexadecane/water emulsion in the presence of surfactants including sodium dodecyl sulfate, polyoxyethylene-sorbitan monooleate (Tween80), and cetyltrimethyl ammonium bromide. It is revealed that surfactants with micromolar concentrations notably influence the adsorption of MG at the oil/water interface. Both competition adsorption and charge-charge interactions played very important roles in affecting the adsorption free energy and the surface density of MG at the oil/water interface. The sensitive detection of the changing oil/water interface with the adsorption of surfactants at such low concentrations provides more information for understanding the behavior of these surfactants at the oil/water interface.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (Nos. 21273277 and 21473249), the “1000 Talent Program” (The Recruitment Program of Global Experts), the “One Hundred Talents Project Foundation Program” and the “Western Action Plan (KGZD-EW-502)” from the Chinese Academy of Sciences, and the “Young Creative Sci-Tech Talents Cultivation Project of Xinjiang Uyghur Autonomous Region (Nos. 2013711016 and 2013711012).”
