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Individual Biomolecules via Break Junctions

Break junctionWorking principle of mechanical break junction

Metallic break junctions with tunable nanogaps provide a new approach to investigate the electron transfer mechanism of biomolecule-nanoelectrode hybrid systems. By breaking a metallic wire, two opposing nanoelctrodes can be generated that are later used as source and drain electrode. Break junctions have the advantage that one can tune the distance between the nanoelectrodes to the size of a single molecule with sub Ångstrom accuracy. We are attaching model proteins or functional units to the nanoelectrode through linker molecules and study the electron transfer in the bio-inorganic junctions. Our goal is to identify charge transport pathways in biomolecules and to determine the dominating charge transport mechanism.

Mechanically Controllable break junction

Mechanically Controllable break junction

Mechanically controllable break junction (MCBJs) setups with tunable distance between the nanocontacts give control over the number of molecules electrically connected in the junction. MCBJs make use of an attenuation factor to control the electrode with unique accuracy. Particularly, for individual molecules charge transfer investigations became feasible by realization of different nanoelectrodes configurations where the electrodes are separated by a gap of molecular dimensions. Functional molecules are applied to the fabricated nanoelectrodes which are bridging the gap after a self assembly process. The so generated organic-inorganic heterojunctions are investigated regarding their electrical and noise characteristics. By this means we were able to show on the level of individual molecules that the electrical properties of metal-organic compounds strongly depend on type of used metal ion. The conductance was found to be reciprocal dependent on the respective complex stability.

In-situ break junctions

In-situ break junctions

For biological systems, the presence of an aqueous environment is of crucial importance for the conservation of structural integrity and functionality. Therefore, we have fabricated in-situ mechanically controllable break junctions (in-situ MCBJ) that facilitate electrical addressing of individual molecules. In-situ break junctions allow tuning of the electrode morphology by controlling the electrode potential in contrast to junctions in a vacuum environment. We found that needle-like nanogaps can be realized at appropriate overpotentials which showed smaller contact area and better stability than nanogaps fabricated by conventional lithography techniques. Later, we bridged the nanogaps by electrostatically linked ferrocene molecules under control of pH and electrode potential and investigated electrical characteristics. The findings are of relevance for understanding biological electron transport as well for designing novel biosensors.

Additional Information

Contact:

Dr. Dirk Mayer

Tel.:  +49-2461-61-4023
e-mail: dirk.mayer@fz-juelich.de

References:

G. Meszaros, S. Kronholz, S. Karthäuser, D. Mayer, Th. Wandlowski, Electrochemical fabrication and characterization of nanocontacts and nm-sized gaps, Appl. Phys. A 87, (2007) 569, DOI: 10.1007/s00339-007-3903-2

 

Y. Liu, A. Offenhäusser, D. Mayer, Rectified tunneling current response of bio-functionalized metal–bridge–metal junctions, Biosens. Bioelectron. 25 (2010) 1173, doi:10.1016/j.bios.2009.10.001

 

Z. Yi, M. Banzet, A. Offenhäusser, D. Mayer, Fabrication of nanogaps with modified morphology by potential-controlled gold deposition, Physica Status Solidi (RRL), 4 (2010) 73, DOI: 10.1002/pssr.200903417

 

Z. Yi, S. Trellenkamp, A. Offenhäusser, D. Mayer, Molecular junctions based on intermolecular electrostatic coupling, Chem. Commun., 46 (2010) 8014, DOI: 10.1039/c0cc02201b

 

D. Xiang, F. Pyatkov, Y. Zhang, A. Offenhäusser, D. Mayer, Gap size dependent transition from direct tunneling to field emission in single molecule junctions, Chem. Commun., 47 (2011), 4760 DOI:10.1039/C1CC10144G

 

D. Xiang, F. Pyatkov, F. Schröper, Y. Zhang, A. Offenhäusser, D. Mayer, Molecular Junctions Bridged by Metal Ion Complexes, Chemistry - A European Journal, 17, (2011)  13166  doi: 10.1002/chem.201102915

 

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