Characterization and Modeling of Stable Colloids of Organically Surface Tailored Gold Nanoparticle Liquids

Stable aggregate-free colloidal suspensions of gold nanoparticle liquids (NPLs) in toluene and dichlorobenzene were prepared. NPLs were made by reduction of tetrachloroauric acid in the presence of mercaptoethane sulfonate and further treatments with surfactants. Gold nanoparticles were coated with a novel ionic bilayer corona which consists of an ionic thiol linker and alkyl ammonium chloride surfactants. NPLs were capable of solvent removal and redispersing in toluene and dichlorobenzene. The average particle size, corona shell thickness, and extent of aggregation were examined using small-angle neutron scattering (SANS) and high resolution transmission electron microscopy (HR-TEM). The volume fraction normalized scattering spectra for the three series of samples exhibited one normalized curve showing a Guinier plateau in the low-q (q < 0.02 angstrom(-1)) regime. This indicates the presence of aggregate-free stable colloidal suspensions within the examined range. The experimental scattering spectra were simulated using a polydisperse core-shell model with Schulz polydispersity approximation. This approximation resulted in average core diameters and average shell thicknesses of NPLs in d-toluene. HR-TEM studies of NPLs exhibited the presence of core-shell structures containing gold cores and corona layers.