Effect of ion exchange in NaAOT surfactant on droplet size and location of dye within Rhodamine B (RhB)-containing microemulsion at low dye concentration

Dioctyl sulfosuccinate sodium salt or Sodium AOT (NaAOT), an ionic surfactants give Na+ counterions in solution, which can interact with a negatively charged surface formed during the formation of nanodroplets in NaAOT/water/oil microemulsion system. In this work, effect of cation exchange in NaAOT surfactant from Na to H on the water droplet size and location of dye of Rhodamine B (RhB) at low concentration within water/decane microemulsions at W = [Water]/[Surfactant] = 40 was studied by the dynamic light scattering (DLS) and spectroscopy techniques. The dynamical characterization of nanometer sized micelles by DLS technique indicated that by exchanging cation within NaAOT microemulsion containing dye, the water droplet size increased and the interactions between nanodroplets were less repulsive with the mass fraction of nanodroplets (MFD). It was observed that hydrophilic dye of RhB at low concentration can be localized near tail (Gouy Chapman Layer) of HOT microemulsion in addition to the locating into the water/oil interface (Stem Layer), slightly than NaAOT microemulsion. Furthermore, molecules of RhB at high dye concentration were localized near tail (Gouy Chapman Layer) of NaAOT microemulsion in addition to locating into the water/oil interface (Stern Layer) compared to molecules of dye at low concentration within NaAOT microemulsion. (C) 2018 Elsevier B.V. All rights reserved.