Electrosynthesis method of CoPt nanoparticles in percolated microemulsions

Abstract

An electrochemical synthesis of CoPt nanoparticles on Si/Ti/Au substrates has been performed in percolated water-in-oil (w/o) microemulsions to define the nanoparticle size and composition. The results allowed us to propose this method for direct growth of nanoparticles over substrates, avoiding overlapping of the particles during the deposition. We use proportions of an aqueous CoPt solution, surfactant and oil components to form w/o microemulsions in which droplets of the aqueous solution could be dispersed in the oil, but in a percolated state, to enhance the global conductivity of the system, allowing the electrodeposition process, although at a moderate rate. Under these conditions isolated nanoparticles have been obtained, whose composition is dependent on the composition of the solution of the aqueous droplets. Nanoparticles obtained at very low deposition rate aggregate by superficial diffusion leading to some well-defined hexagonal particles, reflecting their crystalline structure. When the proportions of the microemulsion components lead to a bicontinuous structure, growing particles overlap and branched structures have been obtained by electrodeposition.