Synthesizing and stabilizing copper nanoparticles by coating with a silica layer in aqueous solution

To improve the oxidation resistance of Cu nanoparticles chemically, silica-coated Cu nanoparticles were obtained by a multi-step process. First, Cu nanoparticles were produced by reducing copper inorganic salts in the presence of citrate acid in aqueous solution. Then these particles were undergone an in-situ surface modification treatment with 3-aminopropyl-trimethoxysilane (APS). And then they were coated subsequently with a silica layer by adding tetraethyl orthosilicate (TEOS) ethanol solution into the above solution. The molar ratio of citrate: Cu2+: hydrazine is 1:1:10, which can guarantee the basic environment of aqueous solution, in which the preparation of Cu particles and the latter coating of silica can be carried out simultaneously and controllably. The stability of Cu particles through coating was improved. Citrate acid and APS had essential effects on the antioxidation of Cu nanoparticles during their synthesis and coating with silica, respectively. (C) 2012 The Ceramic Society of Japan. All rights reserved.