First Synthesis by Liquid−Liquid Phase Transfer of Magnetic Co<i>_x</i>Pt_100-<i>_x</i>Nanoalloys

Abstract

Controlled synthesis of magnetic nanoparticles with a well-known size and composition is always a challenge. A soft chemical synthesis was developed to obtain magnetic alloy nanocrystals with a high ability to control composition, size, and polydispersity. Cobalt-platinum alloy nanocrystals were synthesized using a colloidal approach by the liquid-liquid phase transfer method. Structural characterization using HRTEM and XRD was carried out on nanocrystals in the range of 25-75% cobalt composition, which indicated the formation of nanoalloy bimetallic CoxPt100-x. Adjusting the alkylamine capping agent and the kinetics of the reduction process allowed tuning of the size in the range of 1.8-4 nm while keeping an equiatomic composition. The narrow size distribution led to the possibility of inducing nanoparticle self-organization over a long range. The magnetic properties of the Co50Pt50 nanoalloy in the disordered face-centered cubic phase A1 were studied for different nanoparticle sizes.