In view of their numerous beneficial properties, there is a continuing need for new approaches to synthesize nanomaterials in concentrated forms which are stable and do not subsequently agglomerate or aggregate. A number of different surfactant and micelle systems have been employed in the synthesis as well as for the enrichment of nanoparticles. However, there are only a very few reports on the the utilization of zwitterionic surfactant micelles for such purposes. Zwitterionic surfactants exhibit unique phase behavior (that is opposite that of nonionic surfactants); i.e., their aqueous solutions are homogeneous at temperatures above their upper critical temperature but phase separate at lower temperatures with the formation of a small volume coacervate (surfactant-rich) phase. Thus, their use for the simple one-pot synthesis of metal nanoparticles would be advantageous in that at the elevated temperatures required for many such synthetic protocols, the necessary reactants would be dispersed in the homogeneous micellar medium. Then, after completion of the synthetic reaction step, upon cooling to room temperature, the solution would phase separate with the metal nanomaterials enriched and concentrated in the surfactant-rich coacervate phase. The successful utilization of such approach for the one-pot synthesis of monodispersed metal nanoparticles as well as metal nanochains will be descirbed. The different experimental factors which impact this general approach for the synthesis and preconcentration of such nanomaterials will be delineated. The nanomaterials prepared in such manner were found to be very stable in their concentrated form in the surfactant-rich phase of zwitterionic surfactants.  Some thoughts on the general applicability of this general approach will be presented.

Surfactant mediated one-pot synthesis with in situ preconcentration of metal nanomaterials using thermoresponsive zwitterionic type surfactants

254th National Meeting (2017)

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