Joseph T. Khoury

Critical sizes in the growth of Au clusters

Abstract A systematic exploration of the growth of Au clusters has revealed a critical size for the formation of stable assemblies. Mass-spectrometric measurements of clusters, as grown in the presence of an excess of weakly binding long-chain n-alkylthiol(ate) groups, show high yields of new compounds with core masses near the 15k minimum (≈ 75 Au atoms; k = 10 3 amu), and also at 23k, and 29k. Structural analyse establish their cores as compact metal nanocrystals of the corresponding effective diameters (1.4 to 1.7 nm), probably of decahedral close-packing and morphology. The precise identities of this sequence of special structures can now be sought.

Liquid-phase synthesis of thiol-derivatized silver nanocrystals

A liquid-phase method is reported for the preparation of dodecanethiol-derivatized silver nanocrystals. Toluene sols of this material maintain as sols in air at room temperature at least on the timescale of months. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to obtain size and structural information about the nanocrystal core while solubility properties and energy dispersive X-ray spectroscopy (EDS) are used to identify the passivating layer. Laser desorption time-of-flight mass spectra (LDTOFMS) of this material show broad peaks in the mass range from 40 to 300 kamu. These results are consistent with the synthesized material being a dodecanethiol-derivatized silver nanocrystal material with a mean crystalline silver core of 3.1 + 0.6 nm.