Robust phase transfer, 3D-assembly and SERS application of multi-shaped gold nanoparticles

A robust, fast and versatile phase transfer approach to the transfer of large hydrophilic multi-shaped gold nanoparticles from aqueous to organic phase was systematically investigated. The procedure uses the amphiphilic surfactant bis-(amidoethylcarbamoylethyl) octadecylamine (C18N3), which consists of a long alkane chain to provide hydrophobic properties and terminal amine groups for hydrophilic properties. Furthermore, the 3D-assembly behavior, plasmonic properties and surface-enhanced Raman scattering properties of the hydrophobic multi-shaped gold nanoparticles derived from the phase transfer method on the surface of mercapto-silica colloidal spheres were systematically investigate. The surfaces of mercapto-silica spheres immobilize gold nanoparticles through strong coordination interactions between gold cations and thiol groups and allow the direct assembly of large multi-shaped nanoparticles on supporting colloidal spheres. The size of the gold nanoparticles used in both 3D-assembly and phase transfer is much larger (as large as 55 nm) than any known reports to date. This assembly strategy will provide the research community with a highly versatile, configurable, and reproducible process for the preparation of various structures and great flexibility in incorporating multiple nanoparticle components. An effective procedure for phase transfer of multi-shaped, large size gold nanoparticles with the aid of a multi-amine surfactant C18N3 and their 3D-assembly on the support of mercapto-silica spheres is proposed.