Competitive Adsorption of Thiolated Poly(ethylene glycol) and Alkane-Thiols on Gold Nanoparticles and Its Effect on Cluster Formation

摘要

The surface concentration and conformation ofnthiol-terminated poly(ethylene glycol) (PEG) on gold nanoparticlesnare studied before and after coadsorption of alkane-thiols.nThermogravimetric analysis (TGA) indicates alkane-thiol ligandsnwill competitively adsorb on gold surfaces of nanoparticles and thatnthe extent of PEG-thiol replacement depends on the specific lengthnof the alkane-thiol molecule. The conformation of the polymer isnalso affected by the length and packing density of the alkane-thiol.nDynamic light scattering (DLS) shows that the hydrodynamic sizenof coated particles has an intermediate maximum for thenadsorption of octane-thiol, which also forms the most denselynpacked alkane-thiol monolayers. These two factors greatly impact the formation of clusters by nanoparticle surfactants. Smallnangle X-ray scattering (SAXS) shows that the largest clusters are formed when particles have a low PEG-thiol surfacenconcentration and an extended PEG conformation.