The solid-state structures of organic charge transfer (CT) salts are critical in determining their mode of charge transport, and hence their unusual electrical properties, which range from semiconducting through metallic to superconducting. In contrast, using both theory and experiment, we show here that the conductance of metal | single molecule | metal junctions involving aromatic donor moieties (dialkylterthiophene, dialkylbenzene) increase by over an order of magnitude upon formation of charge transfer (CT) complexes with tetracyanoethylene (TCNE). This enhancement occurs because CT complex formation creates a new resonance in the transmission function, close to the metal contact Fermi energy, that is a signal of room-temperature quantum interference.
A significant problem in understanding the archaeology of standing buildings relates to the proscription to uncover features and structures within plastered and rendered walls due to the susceptibility and historic importance of such structures. Infrared thermography offers a method of visualization that is nondestructive and capable of revealing various types of archaeological anomaly that has been demonstrated on a small scale in the past. A passive infrared thermal camera is used to examine several historic buildings that are known or suspected to contain hidden archaeological information; the technique is also presented on complex, exposed historic building fabric. The results confirm that it is possible to detect various types of man-made anomaly and to differentiate building materials. In consequence, the use of passive thermal infrared imaging is shown to be a valuable tool in the examination and recording of historic buildings and structures.
In this contribution we demonstrate structural control over a transport resonance in HS(CH 2 ) n [1,4 − C 6 H 4 ](CH 2 ) n SH (n = 1, 3, 4, 6) metal-molecule-metal junctions, fabricated and tested using the scanning tunneling microscopy-based I (z) method. The Breit-Wigner resonance originates from one of the arene π -bonding orbitals, which sharpens and moves closer to the contact Fermi energy as n increases. Varying the number of methylene groups thus leads to a very shallow decay of the conductance with the length of the molecule. We demonstrate that the electrical behavior observed here can be straightforwardly rationalized by analyzing the effects caused by the electrostatic balance created at the metal-molecule interface. Such resonances offer future prospects in molecular electronics in terms of controlling charge transport over longer distances, and also in single-molecule conductance switching if the resonances can be externally gated.
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