Electron molecular wires

The probability matrix plays an important role in many processes in chemical physics. For chemical reactions, the probability of reaction is often limited by tunnelling tlnough a barrier, or by the fonnation of metastable states (resonances) in an intennediate well. Equivalently, the conductivity of a molecular wire is related to the probability of transmission of conduction electrons tlttough the junction region between the wire and the electrodes to which the wire is attached. 

Many other opportunities exist due to the enormous flexibility of the preparative method, and the ability to incorporate many different species. Very recently, a great deal of work has been published concerning methods of producing these materials with specific physical forms, such as spheres, discs and fibres. Such possibilities will pave the way to new application areas such as molecular wires, where the silica fibre acts as an insulator, and the inside of the pore is filled with a metal or indeed a conducting polymer, such that nanoscale wires and electronic devices can be fabricated. Initial work on the production of highly porous electrodes has already been successfully carried out, and the extension to uni-directional bundles of wires will no doubt soon follow. 

In addition, SWNTs have been expected to act as acceptors or molecular wires in molecular photoelectric conversion since they have attractive electron-accepting... 

Grozema FC, Siebbeles LDA, Gelinck GH, Warman JM (2005) The Opto-Electronic Properties of Isolated Phenylenevinylene Molecular Wires. 257 135-164 Guiseppi-Elie A, Lingerfelt L (2005) Impedimetric Detection of DNA Hybridization Towards Near-Patient DNA Diagnostics. 260 161-186 Guo Y, see Coleman AW (2007) 277 31-88... 

Linear multinuclear metal complexes are attracting attention in the context of molecular electronics due to their projected use as molecular wires. 01igo(pyridyl)amido ligands are efficient scaffolds for lining up several Ni11 ions like a string. The first structurally characterized trinickel complex of this type, [Ni3(dpa)4Cl2] (dpa = bis(2-pyridyl)amide), showed a nearly linear Ni3 unit with Ni—Ni distances of around 244 pm.209 Penta-, hepta-, and nonanuclear systems have... 

Troisi A, Ratner MA (2005) Modeling the inelastic electron tunneling spectra of molecular wire junctions. Phys Rev B 72(3) 033408... 

Emberly EG, Kirczenow G (2002) Molecular spintronics spin-dependent electron transport in molecular wires. Chem Phys 281 (2—3) 311—324... 

Yaliraki SN, Ratner MA (1998) Molecule-interface coupling effects on electronic transport in molecular wires. J Chem Phys 109(12) 5036-5043... 

Widawsky JR, Kamenetska M, Klare J, Nuckolls C, Steigerwald ML, Hybertsen MS, Venkataraman L (2009) Measurement of voltage-dependent electronic transport across amine-linked single-molecular-wire junctions. Nanotechnology 20 434009... 

Chi Q, Zhang J, Jensen PS, Christensen HEM, Ulstrup J (2006) Long-range interfacial electron transfer of metalloproteins based on molecular wiring assemblies. Faraday Discuss 131 181-195... 

Mujica V, Kemp M, Ratner MA (1994) Electron conduction in molecular wires. I. A scattering formalism. J Chem Phys 101 6849... 

Apart from electron promoters a large number of electron mediators have long been investigated to make redox enzymes electrochemically active on the electrode surface. In the line of this research electron mediators such as ferrocene and its derivatives have successfully been incorporated into an enzyme sensor for glucose [3]. The mediator was easily accessible to both glucose oxidase and an electron tunnelling pathway could be formed within the enzyme molecule [4]. The present authors [5,6] and Lowe and Foulds [7] used a conducting polymer as a molecular wire to connect a redox enzyme molecule to the electrode surface. 

Electron transfer of the glucose oxidase/polypyrrole on the electrode surface was confirmed by differential pulse voltammetiy and cyclic voltammetry. The glucose oxidase clearly exhibited both reductive and oxidative current peaks in the absence of dissolved oxygen in these voltammograms. These results indicate that electron transfer takes place from the electrode to the oxidized form of glucose oxidase and the reduced form is oxidized by electron transfer to the electrode through polypyrrole. It may be concluded that polypyrrole works as a molecular wire between the adsorbed glucose oxidase and the platinum electrode. 

In contrast to the molecular wire of molecular interface, electron mediators are covalently bound to a redox enzyme in such a manner as an electron tunneling pathway is formed within the enzyme molecule. Therefore, enzyme-bound mediators work as molecular interface between an enzyme and an electrode. Degani et al. proposed the intramolecular electron pathway of ferrocene molecules which were covalently bound to glucose oxidase [ 4 ]. However, few fabrication methods have been developed to form a monolayer of mediator-modified enzymes on the electrode surface. We have succeeded in development of a novel preparation of the electron transfer system of mediator-modified enzyme by self-assembly in a porous gold-black electrode as schematically shown in Fig.12 [14]. 

The use of molecular wires and devices for electronics applications is destined to occur. The ability to control molecular structures at the subnanometer scale is obvious throughout chemical synthesis. These are the same techniques that have been optimized over the last 50 years for the synthesis and modification of compounds for pharmaceutical, dye, petroleum, and fine chemical indus-... 

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