Synergism between anionic double tail and zwitterionic single tail surfactants in the formation of mixed micelles and vesicles, and use of the micelle templates for the synthesis of nano-structured gold particles

Interaction between the anionic double tail AOT (sodium bis (ethylhexyl) sulfosuccinate) and the zwitterionic single tail TPS (N-tetradecyl-N,N-dimethyl-3-ammoino-1-propane sulfonate) in water and at the air/water interface has been studied. The surfactants synergistically interact with the solution as well as at the air/water interface forming mixed assemblies. The physicochemical properties of the free amphiphile monomers up to the point of their critical micelle concentration (CMC) have been evaluated and discussed. The interactions between the two amphiphiles in the mixed micelles in the bulk, and the adsorbed mixed assemblies at the air/solution interface have been analyzed using Rubingh and Rosen formalisms. The mixed systems have been found to undergo composition dependent salt induced micelle -> vesicle -> micelle forming transitions (MVMT). This has been supported by the fluorescence anisotropy measurements of the DPH probe, and the hydrodynamic diameter determined by the DLS method. Stable vesicle formation has been confirmed from the calcein dye encapsulation experiments, and the high resolution transmission electron microscopy (HRTEM) measurements. Nano-structured gold particles (GNPs) have been synthesized in the pure and mixed micelles of the AOT and TPS by the reduction of the HAuCl4 by NaBH4. The morphology of the nano-structured materials was characterized from the UV and HRTEM measurements. (C) 2015 Elsevier B.V. All rights reserved.