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Molecular Simulations of Stretching Gold Nanowires in Solvents

Qing Pu and Yongsheng Leng, (Department of Chemical Engineering, Vanderbilt University)
Xiongce Zhao and Peter T. Cummings (CNMS, ORNL)

Achievement

Molecular dynamics and grand canonical Monte Carlo simulations were performed to study, for the first time, the effect of solvent on the elongation dynamics and structure of gold nanowires. For a simple Lennard-Jones solvent (propane), molecular dynamics simulation results demonstrated that below the melting point of gold nanowires, the solvent effect on the elongation properties of Au nanowires is minimal. Monte Carlo simulations were performed to study the self-assemble structure of benzenedithiol (BDT) molecules on a gold nanowire when it is immersed a bulk BDT liquid, using the force field for the BDT-Au chemical bonding developed by several of the authors. The simulation results show that the packing density of the bonded BDT on the surface of Au nanowire is greater than that on an extended Au (111) surface.

Significance

Studying the current-voltage (I-V) characteristics of single molecules is a key step towards the development of practical molecular electronics devices. Many of the experimental I-V measurements in metal-molecule-metal junctions have been performed in a solvent where the junctions were created through mechanical stretching of nanowires. The electronic properties of these junctions are dependent on both the stretching process and the environment in which the fabrication is performed. However, the effect of solvent on the elongation properties of nanowires has not been previously investigated. Molecular modeling is a natural tool to investigate such questions. This study is the first theoretical approach to investigate the solvent effects on the elongation the Au Nanowires. The results from this paper are helpful in understanding the underlying mechanism of the formation of Au-BDT-Au junctions implemented in molecular conductance measurements.

Publications

Qing Pu, Yongsheng Leng, Xiongce Zhao, and Peter T. Cummings, "Molecular Simulations of Stretching Gold Nanowires in Solvents," Nanotechnology 18, 424007 (2007).

 

(a) (b)

Break-junction configurations of 256-Au (001) nanowire in (a) vacuum and (b) propane at 300 K.

(a) (b)

The equilibrium adsorption configurations of BDT molecules on an Au (001) nanowire.
(a) Side view (b) top view