Electrochemical Gate-Controlled Conductance of Single Oligo(phenylene ethynylene)s

Abstract

We have studied electron transport properties of unsubstituted oligo(phenylene ethynylene) (OPE) (1) and nitro-substituted OPE (2) covalently bound to two gold electrodes. The conductance values of single 1 and 2 are approximately 13 and approximately 6 nS, respectively. In addition to a decrease in the conductance, the presence of the nitro moiety leads to asymmetric I-V characteristics and a negative differential resistance-like (NDR-like) behavior. We have altered the nitro-substituted OPE by electrochemically reducing the nitro group and by varying the pH of the electrolyte. The conductance decreases linearly with the electron-withdrawing capability (i.e., Hammett substituent values) of the corresponding reduced species. In contrast, the conductance of 1 is independent of the pH and the electrode potential.

Electrostatic modification of novel materials

“…Extending these approaches to three-terminal devices has been extremely challenging because of geometrical and electrostatic constraints. Electrochemical gating of atomic-scale junctions and individual small molecules has also been demonstrated ͑Shu et al, 2000;Chen, Zwolak, and Di Ventra, 2005;Xiao et al, 2004Xiao et al, , 2005Albrecht et al, 2005;Xu et al, 2005a We note that significant progress has been made in fabricating transistors based on carbon nanotubes. These macromolecules may be considered as onedimensional semiconductor or metallic crystals, and exhibit a number of remarkable properties, including ballistic conduction.…”

Single-molecule transistors: Electron transfer in the solid state

“…Some have argued that charging energies may be renormalized by strong coupling to the metallic source and drain [9]. Further, Coulomb charging effects can be strongly reduced in, for example, electrochemical STM experiments [33], due to the large relative dielectric constant of the surrounding solution.…”

Nanogap Electrodes

“…There are mainly two approaches for wiring molecules between electrodes. One method is to make top-contact junctions, which includes scanning probe microscopy (scanning tunneling microscopy (STM) and conducting atomic force microscopy (AFM)), [11][12][13][14][15][16][17][18][19][20][21][22] cross wire junctions, [23][24][25] mercury drop electrodes [26,27] and thermally deposited metal films. [6] All devices manufactured by this kind of method can be categorized as 'prototype devices', which are very useful for fundamental investigations and have already provided many important results.…”

“…[6] All devices manufactured by this kind of method can be categorized as 'prototype devices', which are very useful for fundamental investigations and have already provided many important results. [4][5][6][7][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] However, these devices are far from practical applications, as we can not imagine a nanometer device carrying a huge scanning probe microscopy (SPM) system or other systems. The other way utilizes nanogap electrodes [28][29][30][31][32] to form metal/molecule/metal devices.…”