Molecular conformation changes in alkylthiols ligands as a function of size in gold nanoparticles: X-ray absorption studies

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

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physics Society

Año: 2006 vol. 74 p. 734101 - 734104

0163-1829

The bonding of hexanethiols to gold nanoparticles of 1.5, 2.0, and 3 nm was studied using x-ray absorption near-edge spectroscopy (XANES) extended x-ray absorption fine structure (EXAFS). The XANES spectra revealed that a substantial fraction of weakly bound hexanethiol molecules are present in addition to those forming covalent bonds with Au atoms. The weakly bound molecules can be removed by washing in dichloromethane. After removal of the weakly bound molecules the S K-edge XANES reveals peaks due to S-Au and S-C bonds with intensities that change as a function of particle size. Au L3-edge EXAFS results indicate that these changes follow the changes in coordination number of Au to the S atoms at the surface of the particles.