Cu nanoparticles of low polydispersity synthesized by a double-template method and their stability

Cu nanoparticles of well-defined size and stability were synthesized with the aid of a double-template method. The templates consisted of sodium dodecyl sulfate (SDS) aggregates combined with and wrapped by poly(vinylpyrrolidone) (PVP) chains. Copper sulfate was reduced within the templates resulting in multicrystalline Cu nanoparticles. The size of the particles was uniform. They were capped by PVP–SDS complexes and the shape turned out to be non-spherical. PVP used in the experiments has an average molecular weight of 40,000. In this case, the particle dimensions were essentially determined by the chosen concentration of SDS in the reaction solution. No oxidation of the as-grown copper particles was detected even in the absence of inert gas protection during the synthesis process. When exposed to air at room temperature, Cu nanoparticles capped by PVP–SDS complexes showed much better resistance to oxidation than those without the capping agents. Furthermore, the steric and screening effect of the capping agents permitted the preparation of uniform colloidal dispersions stable over months. The material obtained by this double-template method was found to be very sensitive to the synthesis temperature. At synthesis temperatures above 40 °C, CuO instead of Cu was obtained.