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 (similar to 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).