| Abstract
| - The mean size of the gold (Au) core in the synthesis ofdodecanethiolate-stabilized Au cluster compoundscan be finely adjusted by choice of the Au:dodecanethiolate ratio andthe temperature and rate at whichthe reduction is conducted. The Au clusters have been examinedwith a large number of independentanalytical tools, producing a remarkably consistent picture of thesematerials. Average cluster and coredimensions, as ascertained by 1H NMR line broadening,high-resolution transmission electron microscopy,small-angle X-ray scattering, and thermogravimetric analysis, varybetween diameters of 1.5 and 5.2 nm(∼110−4800 Au atoms/core). The electronic properties of the Aucore were examined by UV/vis and X-rayphotoelectron spectroscopy; the core appears to remain largely metallicin nature even at the smallest coresizes examined. The alkanethiolate monolayer stabilizing the Aucore ranges with core size from ∼53 tonearly 520 ligands/core, and was probed by Fourier transform infraredspectroscopy, differential scanningcalorimetry, contact-angle measurements, and thermal desorption massspectrometry. The dodecanethiolatemonolayer on small and large core clusters exhibits discernabledifferences; the line dividing “3-dimensional”monolayers and those resembling self-assembled monolayers on flat Au(2-dimensional monolayers) occursat clusters with ∼4.4 nm core diameters.
|
