Control of the Shape and the Size of Copper Metallic Particles

Colloidal copper particles were prepared in aqueous solution via the reduction of copper dodecyl sulfate, Cu(DS) 2, by sodium borohydrate. Below the critical micellar concentration (cmc), it has been obtained isolated particles forming an interconnected network of either oxide or pure metallic copper aggregates. Syntheses performed above the cmc show the formation of elongated or spherical copper metallic particles. The size and shape of crystallites are controlled by surfactant concentration. The change in the shape of metallic copper particles from spheres to rods is followed by TEM and UV−visible spectroscopy. As it has been predicted by calculation, a red shift in the plasmon peak is observed when the elongation of the particles increases. It is demonstrated that the shape and the size of the particles are controlled by the formation and the number of micellar aggregates.