Alkanethiolate Gold Cluster Molecules with Core Diameters from 1.5 to 5.2 nm:  Core and Monolayer Properties as a Function of Core Size

Abstract

The mean size of the gold (Au) core in the synthesis of dodecanethiolate-stabilized Au cluster compounds can be finely adjusted by choice of the Au:dodecanethiolate ratio and the temperature and rate at which the reduction is conducted. The Au clusters have been examined with a large number of independent analytical tools, producing a remarkably consistent picture of these materials. Average cluster and core dimensions, as ascertained by 1H NMR line broadening, high-resolution transmission electron microscopy, small-angle X-ray scattering, and thermogravimetric analysis, vary between diameters of 1.5 and 5.2 nm (∼110−4800 Au atoms/core). The electronic properties of the Au core were examined by UV/vis and X-ray photoelectron spectroscopy; the core appears to remain largely metallic in nature even at the smallest core sizes examined. The alkanethiolate monolayer stabilizing the Au core ranges with core size from ∼53 to nearly 520 ligands/core, and was probed by Fourier transform infrared spectroscopy, differential scanning calorimetry, contact-angle measurements, and thermal desorption mass spectrometry. The dodecanethiolate monolayer on small and large core clusters exhibits discernable differences; the line dividing “3-dimensional” monolayers and those resembling self-assembled monolayers on flat Au (2-dimensional monolayers) occurs at clusters with ∼4.4 nm core diameters.

3D Monolayers of 1,4-Benzenedimethanethiol on Au and Ag Clusters: Distinct Difference in Adsorption Geometry with the Corresponding 2D Monolayers

“…Absence of any observable shift indicates that the fraction of atoms involved in bonding is low in the clusters. Even for a cluster of 2.8-nm core diameter, only 10% of the total number of atoms are bound to thiolate groups (4), and the absence of Au I in XPS is not unexpected. Final state effects do not seem to shift the peak position greatly in this size range as seen earlier (4).…”

“…Molecules with a number of head and tail groups can be made to bind different surfaces (3), and it is possible to synthesize clusters with diverse properties. A range of cluster sizes can also be prepared by appropriate manipulation of the kinetic parameters (4). Apart from the properties of the metal core, the molecular chemistry of monolayers has also attracted attention (5).…”

Influence of Incorporated Lipophilic Particles on Ion Fluxes Through Polymeric Ion‐Selective Membranes

“…400 mesh ASTM) for column chromatography were from Fluka, the porous silica gel, Chromatographiegel Kovasil C 18 100A-20 (20 mm), of 100 ä nominal pore diameter, and Kovasil MS-C 18 (1.5 mm) from Chemie Uetikon AG (CH-8707 Uetikon, Switzerland). The syntheses of nanosized gold particles followed a standard procedure (type RT,2X,sd in [31]). …”

Helically Twisted Chiral Arrays of Gold Nanoparticles Coated with a Cholesterol Mesogen

“…Together with a surface area of the NPs estimated to be 11.5 to 13 nm 2 (ref. 25), this gives 73-82 ligands per particle. 27 Based on DSC and polarized optical microscopy (POM) the phase sequences obtained for 1 and AuCholC6 are listed in Table 1.…”