Preparation of silver nanostructures from bicontinuous microemulsions

Abstract

Precipitation of silver nanoparticles at 70C was carried out by dosing a 1.3M sodium borohydride aqueous solution over bicontinuous microemulsions formed with a mixture of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium dodecylsulfate (SDS) as surfactants, a 0.5M silver nitrate aqueous solution, and toluene. Weight ratios of 2.5/1 and 3/1 AOT/SDS were used in the precipitation reactions. Silver nanoparticles were characterized by transmission electronic microscopy, X-ray diffraction, and atomic absorption spectroscopy. A mixture of isolated spheroidal nanoparticles (15wt.%) with an average diameter around 10nm and wormlike structures (85wt.%) with an average length close to 480nm and an average diameter ca. 40nm was obtained, regardless of the AOT/SDS ratio. Higher yields were obtained compared with those reported when reverse microemulsions were employed. Formation of wormlike structures was ascribed to one-dimensional aggregation of crystal and particles within the channels of bicontinuous microemulsions, which performed as templates. Copyright © 2012 M. A. Pedroza-Toscano et al.