Durian-like multi-functional Fe3O4–Au nanoparticles: synthesis, characterization and selective detection of benzidine

A novel durian-like multi-functional water soluble Fe3O4–Au nanocomposite is fabricated via a facile layer-by-layer technology in which a mercapto-silica shell is utilized as a functional coating on the central Fe3O4 nanoparticle cluster. Then gold nanoparticles are loaded onto the surface of Fe3O4, stabilized by Au–S chemical bonding. The fabricated nanocomposites inherit excellent physical and chemical properties from their building blocks, simultaneously exhibiting superparamagnetic, surface plasmon resonance and surface enhanced Raman scattering (SERS) active properties. Based on the magnetic separability of the inner Fe3O4 nanoparticle clusters and the SERS active properties of the suface gold, a selective detection method for benzidine has been developed for rapid detection and ease of operation with a low detection limit of 0.18 ppm.