Christian Punckt - Adsorption of Sodium Dodecyl Sulfate on Functionalized Graphene Measured by Conductometric Titration

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  Hsieh, Andrew G., Punckt, Christian, Korkut, Sibel, Aksay, Ilhan   A. 117 7950-7958-

  Abstract: We report on the adsorption of sodium   dodecyl sulfate (SDS) onto functionalized graphene sheets (FGSs)   in an aqueous system, measured at broad SDS and FGS concentration   ranges by conductometric surfactant titration. At dilute SDS   concentrations (<12 mu M in bulk solution), there is evidence   of a counterion exchange between hydronium ions (from the   dissociation of acidic chemical functionalities on FGS) and   sodium ions coadsorbing with dodecyl sulfate monomers onto FGSs.   We find that, for FGS with a carbon-to-oxygen ratio of similar to   18, monolayer adsorption of SDS on FGS reaches full surface   coverage by similar to 12 mu M SDS. Additionally, the critical   surface aggregation concentration (csac) for surface micelle   formation on FGS is measured to be similar to 1.5 mM SDS The   transition from monolayer adsorption to surface micelle formation   appears to occur at a similar SDS concentration on FGSs as on   graphite, suggesting there is little difference in the surfactant   adsorption behavior on both materials. We estimate that the FGS   surface area available for SDS adsorption is similar to 600   m(2)/g which is significantly less than expected for FGSs in   suspension and indicates the presence of regions on FGS on which   SDS adsorption does not occur.

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