Synthesis and surface enhanced optical properties of multibranched spindle particles and core–shell structures

A facile approach has been developed for the synthesis of monodisperse spindle-shaped α-Fe2O3 and multibranched spindle FeO(OH) as well as their core–shell structures. The formation of unique multibranched spindle FeO(OH) particles depended on the smooth liberation of hydroxide ions by urea which inhibited the nucleation and growth rate of crystals. The amount of different metal ions and oleic acid exhibited significant effect on the shape of the particles, in which the formation of multibranched ends was induced. Their core–shell structures were fabricated by attaching the small Au nanoseeds onto the core surfaces followed with the catalyzed reduction to form continuous Au shell. The FeO(OH) and FeO(OH)@Au core–shell crystals were characterized using transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The surface-enhanced Raman scattering (SERS) activities from different core–shell substrates were investigated. The results revealed that the intensity of SERS signal was dependent on the shell thickness. The multibranched core–shell particles exhibited optimum SERS activity and could serve as candidate substrate for both theoretical and practical applications in SERS.