Facile Synthesis and Characterization of Au-Urchin@Ag Core-Shell Nanoparticles

Core-shell structures of numerous metal nanoparticles have captured significant research attention; however, a proper control of their synthetic approach, morphologies and optical properties still remains challenging. Herein, an anisotropic coating of silver onto sea urchin-like gold nanoparticles so called Au-urchin@Ag core-shell nanoparticles were facilely prepared based on the seed mediated growth approach at room temperature. Ascorbic acid was used as green reductant for the coating of Ag shell onto pre-synthesized urchin gold seeds in the presence of polyvinyl pyrrolidone as capping agents. The Au-urchin@Ag core-shell nanohybrids exhibit a highly anisotropic morphology with tunable shell thickness and optical properties in the range 650–800 nm. Controlling the reaction rate by modulating the reaction pH plays a decisive role to form core-shell structure. Furthermore, the Au-urchin@Ag nanohybrids display a gradual blue-shift in the spectral response upon increasing the amount of AgNO3 precursor or reducing the dosage of Au-urchin seeds. The synergistic effect derived from the coupling of anisotropic silver shell and spiky shaped gold cores with multiple generated hot-spots suggests their great potential for plasmonic sensing, catalysis and biological applications.