Charge Reversal Behavior at the CaF₂/H₂O/SDS Interface as Studied by Vibrational Sum Frequency Spectroscopy

Abstract

We report in situ spectroscopic measurements of charge reversal behavior and surfactant bilayer formation at the salt/aqueous solution interface as the aqueous surfactant concentration is varied. The studies, which employ vibrational sum frequency spectroscopy to measure the vibrational response of sodium dodecyl sulfate and water at the CaF 2 /H 2 O interface, demonstrate the complex nature of the adsorption process which includes monomer adsorption, surfactant bilayer formation, surfactant restructuring, surface charge reversal, and water reorientation. These effects have been monitored directly for the first time by taking advantage of the spectroscopy and the nonlinear phase relationships between the CH and OH vibrational modes. The results provide important insight into the adsorption mechanism that is central to processes such as mineral ore flotation and separation, waste processing, and petroleum recovery.

Measuring properties of interfacial and bulk water regions in a reverse micelle with IR spectroscopy: A volumetric analysis of the inhomogeneously broadened OH band

“…However, SFG spectra of interfacial water have been measured for other water/surfactant interfaces [32][33][34][35]. In these systems, the SFG water spectrum is typically described by two broad Gaussian components centered at 3200 cm À1 and 3450 cm À1 .…”

Phenomenology and control of buckling dynamics in multicomponent colloidal droplets

“…The initial colloidal aqueous dispersion of silica (LUDOX V R TM 40, pH $ 9, average diameter $22 nm, 40% in weight, Sigma Aldrich, India) was diluted to 2% in weight in distilled water and the dynamics of the levitated droplet under natural drying condition was recorded as the base case. SDS [22][23][24][25][26][27][28][29] (BioReagent, !98.5% (GC), Sigma Aldrich, India) dispersion was prepared in distilled water and added to 2% weight aqueous TM dispersion. The mixed colloidal dispersion was sonicated for 30 min using ultrasonicator.…”

“…Such an arrangement of headgroups of the surfactants leads to minimum energy of the system. 25 The silica particles continue to interact among each other and forms aggregates in the spaces available [not occupied by SDS headgroups] (Figs. 3(ii)(b) and 3(ii)(c)).…”

Sum-Frequency Vibrational Spectroscopy on Water Interfaces: Polar Orientation of Water Molecules at Interfaces

“…Controlled adsorption of sodium dodecyl sulfate (SDS) surfactant anions on the surface could be used to adjust the net surface charge density. 104,105 As the surface charge density changed from positive to negative, the intensity of the SF vibrational spectrum first decreased, went through a minimum at the zero-charge point, and then increased. Presumably 5 S…”