Assembly Of Gold Nanowires Research Articles

Assembly of Gold Nanowires on Gold Nanostripe Arrays: Simulation and Experiment

Nanowires (NWs) have a large aspect ratio and large available surface area, which have made them a potential platform for applications in biosensors as well as electronic/optic and power storage de...

Building a hybrid nanocomposite assembly of gold nanowires and thienyl-derivative fullerenes to enhance electron transfer in photovoltaics

We report the preparation and characterization of a novel nanocomposite assembly comprising metallic gold nanowires (Au NWs) and thienyl-C61-butyric acid methyl ester (ThCBM) fabricated by adsorbing ThCBM groups, via coordinate bonds involving sulfur functionalities, onto the Au(111) surfaces of Au NWs. The ThCBM-adsorbed Au NW nanocomposites displayed clear shifts in the plasmonic absorption band and in the binding energy of the gold relative to the pure gold NWs. A bulk heterojunction solar cell using the ThCBM-adsorbed Au NW nanocomposites displayed a good power conversion efficiency (PCE) of 3.12%, and a short circuit current density and fill factor that were significantly better than those of a reference cell prepared using ThCBM without Au NWs (with a PCE of 2.67%). The electron mobility in an electron-only device prepared using the ThCBM-adsorbed Au NW nanocomposites was significantly higher (by 35% or more) than the electron mobility in a device prepared with pure ThCBM. In conclusion, the hybrid composites proposed here, i.e., ThCBM-adsorbed Au NW nanocomposites, provide a promising approach to improving the performance of bulk heterojunction photovoltaic cells via improved electron transfer through the metallic nanowires as well as by enhanced ordering among the fullerenes assembled along the longitudinal axes of the gold nanowires.

Assembly of gold nanowires by sedimentation from suspension: Experiments and simulation.

We investigated the ordering of gold nanowires that settled from aqueous suspension onto a glass substrate due to gravity. The nanowires, ca. 300 nm in cross-sectional diameter and ca. 2, 4, or 7 microns in length, were coated with 2-mercaptoethanesulfonic acid to provide electrostatic repulsion and prevent aggregation. The layer of nanowires in direct contact with the substrate was examined from below using optical microscopy and found to exhibit smectic-like ordering. The extent of smectic ordering depended on nanowire length with the shortest (2 μm) nanowires exhibiting the best ordering. To understand the assembly in this system, we used canonical Monte Carlo simulations to model the two-dimensional ordering of the nanowires on a substrate. We accounted for van der Waals and electrostatic interactions between the nanowires. The simulations reproduced the experimental trends and showed that roughness at the ends of the nanowires, which locally increased electrostatic repulsion, is critical to correctly predicting the experimentally observed smectic ordering.

Selective Assembly of Gold Nanowires on Patterned Gold Surfaces via Electrostatic Interactions

Gold nanowires, 50 nm in diameter and 1-2 μm in length, were prepared by template synthesis and modified by bifunctional thiols then suspended in different solvents. The dispersibility of nanowires is found to be strongly affected by the selection of solvents. The functionalized gold nanowires can be selectively assembled onto patterned surface via electrostatic interactions. It is possible that this simple process can be carried out in fabrication of more complicated structures, which are potentially useful in many applications such as nanoelectronic, photonic and SERS.

Surfactant mediated assembly of gold nanowires on surfaces

The potential of surfactant interactions to direct both the placement and orientation of gold nanowires onto surfaces from solution has been investigated. Gold nanowires were synthesized by template electrodeposition in porous aluminum oxide membranes. Their assembly onto surfaces was controlled by functionalizing the nanowires and surfaces with self-assembled monolayers of thiol based surfactants. Nanowires were assembled from solution onto patterned functional surfaces, and after excess solvent had evaporated the arrangement of nanowires on the surface was observed. A variety of assembly techniques, based upon wettability, electrostatic, or chemical interactions have been studied. Nanowire assembly onto surfaces with patterned wettability resulted in the placement of nanowires on hydrophilic regions with a specific orientation. Hydrogen bonding and carboxylate salt attachment of mercaptoundecanoic acid functionalized nanowires to reactive regions of patterned surfaces has been demonstrated, with unbound wires removed by washing. Similarly, electrostatic interactions between charged nanowires and surfaces have been demonstrated to preferentially assemble nanowires onto oppositely charged surface regions. Although selective attachment of nanowires to reactive surface regions was achieved by both chemical and electrostatic assembly techniques, these methods did not control the orientation of assembled nanowires.

DNA-Templated Assembly of Conducting Gold Nanowires

AbstractThe use of DNA to template the assembly of gold nanowires from gold nanoparticles is reported. Double-stranded calf thymus DNA, was deposited on a polystyrene-coated silicon wafer substrate. The substrate was then exposed to an aqueous dispersion of positively charged gold nanoparticles (~ 4 nm diameter), which adsorbed at the negatively charged DNA template. The adsorbed nanoparticles were then enlarged and enjoined by electroless deposition leading to formation of continuous nanowires of 85 nm average diameter. Gold electrodes were then overlaid on individual nanowires using conventional lithographic techniques. Two-terminal current-voltage measurements were employed to characterize the electrical characteristics of single nanowires. The nanowires exhibit resistivity values < 6 × 10-7 Ωm. These and related findings have implications for the design and assembly of next generation electronic devices.

DNA-templated Assembly of Nanowires and Protein-functionalized Nanocontacts

We describe the use of DNA to template the assembly of gold nanowires between conventionally patterned gold contacts on a silicon wafer substrate. We also describe the use of DNA to template the assembly of protein-functionalized gold nanocontacts on a silicon wafer substrate. Of particular significance is the finding that suitably modified gold nanoparticles recognize and bind selectively the protein-functionalized nanogap between the above contacts and are localized there.