The conformation of adsorbed citrate on gold nanoparticles (AuNPs) has been investigated. We employed attenuated total internal reflection-IR (ATR-IR) and x-ray photoelectron spectroscopy (XPS) to characterize coordination of the functional groups of the adsorbed citrates to the AuNP surface. Spectroscopy data indicates the central and one of the terminal carboxylate groups are associated with the surface binding, while the hydroxyl group is not involved in surface coordination. Also, the free carboxylate group exhibits intraparticle-type interactions with incoming metal ions. There is evidence of a second citrate layer interacting with the absorbed surface citrate through hydrogen bond formation between terminal free carboxylic acids, which form a citrate bilayer on the AuNP surface. The intermolecular spacing of the adsorbed citrate is estimated. We expect that more detailed characterization of the citrate adsorption on AuNPs will impact a broad area of AuNP-based studies including ligand exchange reactions, nanoparticle catalytic activity, and linker conjugation.

Conformation of adsorbed citrate on gold nanoparticles: Intermolecular spacing and citrate bilayer

241st National Meeting (2011)

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