Thiolated Gold Nanoparticles Research Articles

Assembling thiolated gold nanoparticles in compact patterns: a transmission electron microscopy and scanning probe microscopy investigation

We present results from a study of the deposition of synthesized dodecanethiol capped gold clusters onto solid substrates investigated using Transmission Electron Microscopy (TEM) and Scanning Probe Microscopy (SPM). TEM imaging of films prepared onto carbon coated grids using the drop cast method from cluster solutions that have undergone an increasing number of selective size separation steps show the efficacy of the vapor transfer technique in narrowing down the particle size distribution. In order to assemble the gold clusters in compact patterns and investigate their organization using SPM, we have prepared 1,4-benzenedimethanethiol self-assembled films onto heteroepitaxial gold on mica to be used as a substrate. A comparison of results obtained on this substrate using gold cluster films prepared with the drop cast method and the Langmuir-Blodgett (LB) technique is made. In the case of LB films made from size-selected nanoparticles, we present room temperature scanning tunneling images of clusters arranged in compact patterns.

Digestive Ripening of Thiolated Gold Nanoparticles: The Effect of Alkyl Chain Length

Digestive ripening, heating a colloidal suspension at or near the solvent boiling point in the presence of a surface-active ligand, was applied to polydisperse colloidal gold in toluene using a series of alkylthiols, viz., octyl-, decyl-, dodecyl-, and hexadecylthiols. In all the instances, digestive ripening significantly reduced the average particle size and polydispersity. All the colloids remain suspended in solution above 80 °C, but at room temperature the tendency to form 3D superlattices and precipitate increased with declining alkyl chain length. For example, using octanethiol as the ligand makes the colloids aggregate into big 3D superlattices and precipitate; decane- and dodecanethiol also produce precipitated 3D superlattices along with separate particles, while hexadecanethiol-coated particles remain well separated from each other. The optical spectra at room temperature reveal, apart from the gold plasmon band at 530 nm, a large tail above 700 nm for Au−octanethiol and Au−decanethiol cases an...