Reclined trend of alkyl chain of sodium dodecylbenzenesulfonate molecules induced by friction

Abstract

Surfactants tend to adsorb on the surface/interface mostly in a directional manner. The alkyl chain orientation and conformation order for molecular monolayers of sodium dodecylbenzenesulfonate (SDBS) at low concentrations are studied by using the sum frequency generation vibrational spectroscopy (SFG-VS). The molecular arrangement of the surfactants adsorbed at the solid/liquid interface is further investigated. It is found that the arrangement of the SDBS at the interface becomes relatively ordered with increasing bulk concentration. Meanwhile, the orientation angle reduces gradually, and the molecules tend to be upright state. In addition, the effect of friction on the conformation order and orientation angle are also analyzed. The intensity of the SDBS vibrational contraction peak becomes lower after friction, which indicates that the anion has a reorientation process at the interface. The arrangement of molecules becomes more disordered due to friction. The orientation angle increases slightly, which indicates the monolayer has an inclined trend relative to the lateral direction on the interface. A modified adsorption model considering friction effect is proposed. This work may provide a reference for the further study of adsorption mechanism and application of surfactants.

Shielding Effects Provide a Dominant Mechanism in J-Aggregation-Induced Photoluminescence Enhancement of Carbon Nanotubes

“…Although the surface coating of SWCNTs by surfactants is primarily for improving its dispersion stability in an aqueous environment and the separation of SWCNTs with different chirality, , the surface coating by surfactants has been reported to contribute to the enhancement of the photoluminescence of SWCNTs . Previous studies suggested that 4SDBS adsorbs on SWCNTs in two steps. − The first step occurring at a low concentration is random adsorption of 4SDBS, with their hydrophobic tails parallel to the long axis of SWCNTs . At a high concentration, 4SDBS is reorganized into a more ordered adsorption with their aliphatic tails arranged perpendicular to the long axis of SWCNTs .…”

Hydration lubrication modulated by water structure at TiO2-aqueous interfaces

“…The detailed laser assembly of SFG measurements was described in Refs. [48][49][50]. The SFG setup was based on an amplified laser system (Spitfire, Spectra-Physics; 1 kHz, 100 fs) to generate pulses at 800 nm (5 mJ of energy) through a sapphire oscillator (Mai Tai, Spectra-Physics) and a high-power pump laser (Empower, Spectra-Physics).…”