Molecular Conformation Changes in Alkylthiol Ligands as a Function of Size in Gold Nanoparticles

J. M. RAMALLO-LOPEZ; GIOVANETTI, L.J.; F. G. REQUEJO; S. R. ISAACS; Y. S. SHON; M. SALMERON

LNLS Scientific Highlights Activity Report 2006

Brazilian Association for Syncrotron Light Technology

Lugar: Campinas; Año: 2007; p. 52 - 54

The binding of thiol molecules to gold, and in particular to gold nanoparticles (NP), is important in sensors, self-assembled monolayers and many other nanotechnology applications. For example, organic-thiolates are extensively used as capping agents to prevent metal particle sintering and as ligands that can be functionalized to provide desirable chemical properties. An interesting feature of alkyl hydrocarbon chains is their flexibility that allows them to change conformation to maximize space filling. This is driven by the inter-chain van der Waals energy, which is considerable higher for longer chains and can be comparable to the stronger covalent bond of the S head with the Au.  By other side, chain flexibility is facilitated by the easy formation of gauche distortions which require activation energies of only 0.16 eV.