Gold nanoparticles surface-terminated with bifunctional ligands

Gold nanoparticles have been prepared using bifunctional ligands of the type XRSH (X = COOH, OH, NH2) so that the surface is terminated with these functionalities. The ligands bind to the gold surface through their thiol (SH end). The coverage and binding strength of the surfactant on the gold surface have been investigated using thermogravimetric analysis and FTIR spectroscopy. The nanoparticles appear to have excess surfactants on their surface, but these do not necessarily form a bilayer structure. The surfactant conformation allows enough room for the particles to be bonded to other surfaces, such as those of another nanoparticle, even with some excess surfactant present on their surface.