Scattering Correlation Spectroscopy and Raman Spectroscopy of Thiophenol on Gold Nanoparticles: Comparative Study between Nanospheres and Nanourchins

The surface characterization of branched and spherical gold nanoparticles was done by two complementary techniques: scattering correlation spectroscopy (SCS) and surface-enhanced Raman spectroscopy (SERS). Thiophenol was used as a surface marker to probe the surface area and the gold–thiophenol interaction in gold nanourchins (GNUs) and gold nanospheres (GNSs). We observed that, for GNU, the thiophenol is first grafted on the core, with a saturation concentration of about 10 –3 M as observed for GNSs. Afterward, the saturation of the branches occurs at a higher thiophenol concentration (∼1 M). A numerical calculation of the surface areas of GNSs of different sizes allowed for the estimation of the GNU surface area. The hydrodynamic radius was measured at different steps of thiophenol–GNP functionalization. By comparing spherical and nonspherical nanoparticles, we demonstrate that the molecule–GNP interaction is highly dependent on the nanoparticle morphology (size and shape).