Controlled synthesis and optical properties of Au and Au@PS nanoparticles

In this study, uniform gold (Au) nanoparticles (NPs) were prepared using seed-mediated growth method. The particle size was controlled by tuning the dosage of seed solution. Au@PS core–shell NPs were then synthesized by introducing a polystyrene (PS) shell (2–3 nm thick) around the core of Au NPs (115 nm). Evaluation of the surface plasmon (SP) optical properties indicated that wavelength of SP resonance of Au NPs increased gradually with increase in the particle size. This red shift was about 0.92 nm per 1 nm increase in particle size. The results also indicated that the zeta potential and optical properties of Au NPs could be adjusted by coating PS on the outside. Therefore, surface modifications and surface coating were effective ways to control the optical properties of Au NPs.