Synthesis of Nickel-Platinum Composite Nanoparticles and Silica-Coating of Them

Authors: Masato Yanase, Noriko Yamauchi, Shohei Tada, Yoshio Kobayashi

Abstract:

Some research groups have been working on synthesizing nickel (Ni) and Ni-containing nanoparticles due to their unique magnetic properties. In a preliminary experiment, aggregates of nanoparticles formed after they were synthesized. Since nanoparticle aggregation may deteriorate their unique properties, a method to suppress nanoparticle aggregation has been required. In the present work, compositing with nickel (Ni) and platinum (Pt) and silica-coating of them were examined for suppression. Ni-Pt nanoparticles were synthesized in water exposed to air, in which nickel (II) acetate tetrahydrate, hexachloroplatinate (IV) hexahydrate, and sodium borohydride were used as a Ni source, a Pt source, and a reducing reagent, respectively. Polyvinylpyrrolidone, poly (sodium 4-styrene sulfonate), and citric acid were used as the stabilizers. Silica-coating of Ni-Pt nanoparticles was performed by adding tetraethylorthosilicate(TEOS)/ethanol solution to the Ni-Pt nanoparticle colloidal solution (Ni-Pt/SiO2). The morphology of Ni-Pt nanoparticles was dependent on the reaction time and the species of stabilizer. The Ni-Pt/SiO2 nanoparticles were composed of Ni-Pt nanoparticles as core and SiO2 as shell, and their morphology depended on the TEOS concentrations. Furthermore, the Ni-Pt/SiO2 nanoparticles were more dispersed compared to uncoated Ni-Pt nanoparticles. This suggested that the silica-coating had an effect to control the aggregation.

Keywords: metal, composite, nickel, platinum, nanoparticle, silica-coating