Hybrid magnetic–plasmonic nanocomposite: embedding cobalt clusters in gold nanorods

Abstract

We developed a method to fabricate hybrid magnetic–plasmonic nanorods (Au–Co NRs) via a modified seed mediated method. The only modification is to use cobalt ions instead of Au³⁺ in the preparation of the seed solution to obtain gold nanorods doped with Co clusters. By adjusting the amount of cobalt seed solution, Au–Co NRs of controlled aspect ratio can be obtained. The optical properties of the obtained Au–Co NRs were investigated and compared to those of the pure Au NRs. A slight shift and broadening were observed in the alloys compared to the pure ones, which was attributed to the presence of Co clusters leading to suppression of the dielectric properties. High resolution transmission electron microscopy (HRTEM) images indicate the existence of Co clusters in situ in the Au NR host and clearly show the metal–metal interface. The magnetic properties of the obtained Au–Co NRs increase as the concentration of dopant Co cluster seeds increases, as investigated by vibrating sample magnetometry (VSM). Our approach allows us to design nanomaterials of controlled shape, optical and magnetic properties which have many promising applications in tharanostics and photoelectronics.