Adsorption Calorimetric Study of the Organization of Sodium n-Decyl Sulfate at the Graphite/Solution Interface

Abstract

The material and enthalpy balances of the adsorption of sodium n-decyl sulfate from aqueous solutions onto graphitized carbon black were determined between 288 and 318 K by using an automated flow sorption/ microcalorimeter system. At low concentrations, the surfactant molecules form a flat monomolecular film on the graphite plane, in consequence of surface-directed ordering. A mechanism is proposed in which two adsorbed phases coexist during the formation of this surfactant monolayer. The enthalpy of adsorption in the monolayer region is ca. -42 kJ mol -1 , which does not depend appreciably on the temperature or on the surface coverage. At higher concentrations, the ordered monolayer induces surface aggregation to produce half-cylindrical hemimicelles as the critical micelle concentration is approached. The enthalpies of surface aggregation at 288, 298, and 318 K are -10, -16, and -26 kJ mol -1 , respectively. As the temperature is increased from 288 to 318 K, the average number of surfactant molecules in the cross section of a half-cylinder drops from ca. 5.4 to 3.4. Calorimetric evidence is provided that cationic and anionic surfactant adsorption on graphite follow the same mechanism in the low-density and high-density adsorbate regions.

Controlling Carbon-Nanotube—Phospholipid Solubility by Curvature-Dependent Self-Assembly

“…13,14 where an initial, ordered monolayer is reported. Simulationally the emergence of alignment following graphite symmetry directions due to collective surfactant-surfactant interactions has been reported earlier for ionic surfactants.…”

“…13,14,76 This would correspond to a monolayer formed of columns of lipids opposing each other. The lipids adopting a side-by-side structure in our simulations is likely a concentration dependent phenomenon (opposing lipid morphology induced only upon further adsorption) and also possibly influenced by the finite size of the simulations box.…”

A Thermometric Titration Study on the Micelle Formation of Sodium Decyl Sulfate in Water

“…The accuracy of the cmc and mic H data is of crucial importance in a number of cases. We recently investigated the aggregative adsorption of n-dodecyltrimethylammonium bromide and SDeS from aqueous solutions onto graphite in the temperature range 288-318 K by using flow sorption microcalorimetry (7,8). An adequate interpretation of the adsorption and calorimetric data of surfactant aggregation at solid/solution interfaces requires a precise knowledge of the cmc and mic H of the same surfactant in bulk solution (7)(8)(9)(10).…”

“…We recently investigated the aggregative adsorption of n-dodecyltrimethylammonium bromide and SDeS from aqueous solutions onto graphite in the temperature range 288-318 K by using flow sorption microcalorimetry (7,8). An adequate interpretation of the adsorption and calorimetric data of surfactant aggregation at solid/solution interfaces requires a precise knowledge of the cmc and mic H of the same surfactant in bulk solution (7)(8)(9)(10). Since the available cmc and mic H data for SDeS, obtained from calorimetry and conductometry, are somewhat contradictory, we decided to perform a high-sensitivity titration calorimetric study of the micelle formation of SDeS in aqueous solutions over a range of temperatures.…”

Effect of an anionic surfactant (SDS) on the photoluminescence of graphene oxide (GO) in acidic and alkaline medium

“…26 In this context, it is important to mention that several researchers extensively investigated the adsorption behavior of surfactants onto graphitic carbons. [36][37][38] Compared to graphite, adsorption behavior of SDS on FGS is different. Graphite contains sp 2 hybridized carbon atoms with a high degree of hexagonal order.…”