Nickolov Z.S., Britt D.W., Miller J.D.
Drexel University, Drexel Nanotechnology Institute, US
Keywords: interfacial water structure, Langmuir films, sum-frequency spectroscopy
Sum frequency spectroscopy (SFS) in the OH stretching region was employed to obtain structural information about the interfacial water structure underneath Langmuir monolayers on H2O subphase. The films were composed by the model lipid dioctadecyldimethylammonium bromide (DOMA or DODAB), the surfactants methyl stearate (SME) and stearic acid (STA), and their mixtures. The results demonstrated that the uncompensated head group charge of DODAB at the interface is the reason for structuring of interfacial water close to the mixed DODAB-methyl stearate monomolecular films. To get insight into this charge-induced effect SFS studies of the structure of the stearic acid monolayer _ water interface as a function of pH were performed. At low pH values the stearic acid monolayer is neutral and the water structure close to it is mostly disordered, while at high pH values it is negatively charged and interfacial water structure is strongly promoted by the surface electric field.
Journal: TechConnect Briefs
Volume: 4, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 4
Published: May 20, 2007
Pages: 32 - 35
Industry sector: Advanced Materials & Manufacturing
Topic: Materials Characterization & Imaging
ISBN: 1-4200-6376-6