Preparation of spindle-shape silver core-shell particles

Silver core-shell nanoparticles with spindle shape were successfully synthesized by the seed-mediated growth technique. Small amount of silver nanoparticles (4 ± 1.5 nm) were immobilized on polyethylene amine (PEI) coated spindle-shape β-FeOOH particles and served as ‘seeds’ for further growth of silver shell. The seed catalyzed growing process was repeated for 1 to 4 times, the surface coverage of the silver core-shell particles was increased until a complete silver layer was formed finally. UV–visible extinction spectra showed that two absorption peaks red-shifted with the increasing surface coverage and shell completeness. Our research showed that these spindle-shape silver core-shell particles were promisingly to be used as surface enhanced Raman scattering (SERS) nanosensors.