Fabrication of NIR-Excitable SERS-Active Composite Particles Composed of Densely Packed Au Nanoparticles on Polymer Microparticles

A simple fabrication method is demonstrated for surface-enhanced Raman scattering (SERS)-active plasmonic nanoballs, which consisted of Au nanoparticles (NPs) and core–shell polystyrene and amino-terminated poly(butadiene) particles, by heterocoagulation and Au NP diffusion. The amount of Au NPs introduced into the core–shell particles increases with the concentration of Au NPs added to the aqueous dispersion of the core–shell particles. When the amount of Au NPs increases, closely packed, three-dimensionally arranged and close-packed Au NPs arrays are formed in the shells. Strong SERS signals from para-mercaptophenol adsorbed onto composite particles with multilayered Au NPs arrays are obtained by near-infrared (NIR) light illumination.