Precipitation reactions of silver nanoparticles were carried out at 50°C in bicontinuous microemulsions composed of a mixture of surfactants sodium bis (2-ethylhexyl) sulfosuccinate/sodium dodecyl sulfate  an aqueous solution of 0.3M silver nitrate and toluene as organic phase. The concentration of the precipitating agent (sodium borohydride) solution and its dosing rate on the microemulsion were varied. A mixture of spheroidal and worm-like silver nanostructures was obtained as demonstrated by X-ray diffraction and high-resolution transmission microscopy. A direct dependence of: (i) the nanostructures size, and (ii) the proportion of the worm-like nanostructures in the final product on the concentration of the precipitating agent was found. A sort of cyclical behavior of the nanostructures average size and the proportion of the nanostructures type in the product throughout the reaction was determined, which was ascribed to a possible repetitive process of accumulation-aggregation of spheroidal nanostructures.

worm-like silver nanoparticles, precipitation reactions, bicontinuous microemulsions.