Combined small-angle x-ray scattering/extended x-ray absorption fine structure study of coated Co nanoclusters in bis(2-ethylhexyl)sulfosuccinate

Abstract

Chemically stable cobalt nanostructures have been prepared with Co(II) reduction in the confined space of cobalt bis(2-ethylhexyl)sulfosuccinate, Co(AOT)2, reverse micelles dispersed in n-heptane. The reaction was carried out by adding a solution of sodium borohydride in ethanol (1% weight) to a 0.2M micellar solution of Co(AOT)2 in n-heptane at a reductant to Co(II) molar ratio of 4. This procedure involves the rapid formation of surfactant-coated Co nanoparticles followed by their slow separation as nanostructures embedded in a sodium bis(2-ethylhexyl)sulfosuccinate matrix. The resulting composites, characterized by extended x-ray absorption fine structure and small-angle x-ray scattering, showed the presence of subnanometer sized cobalt nanoparticles aggregated together to form elongated structures coated by the surfactant molecules.