Carbon nanotubes (CNTs) were deposited from a chlorosulfonic superacid solution onto PET substrates by a filtration/transfer method. The sheet resistance and transmission (at 550 nm) of the films were 60 Ω/sq and 90.9% respectively, which corresponds to a DC conductivity of 12,825 S cm(-1) and a DC/optical conductivity ratio of 64.1. This is the highest DC conductivity reported for CNT thin films to date, and attributed to both the high quality of the CNT material and the exfoliation/doping by the superacid. This work demonstrates that CNT transparent films have not reached the conductivity limit; continued improvements will enable these films to be used as the transparent electrode for applications in solid state lighting, LCD displays, touch panels, and photovoltaics.

The earliest studies of electron-transfer proteins raised the question of whether or not π-electron residues might facilitate electron transport. Three recent long-range electron-transfer experiments utilizing DNA bridges revisit this provocative, yet unresolved, question. ,, The distance dependence of electron transfer in DNA is not a matter of purely academic concern; it controls the mechanism of DNA damage and repair in cells and is being exploited in new molecular probes of DNA sequence. We present a theoretical analysis based upon very large scale self-consistent-field quantum calculation of all valence electrons (as many as ∼3300) in these three systems. This computation is the first performed on such large macromolecules and also the first to extract long-range electronic interactions at this level of theory. DNA electron transfer is found to be mediated by through-space interactions between the π-electron-containing base pairs, but the magnitude of the coupling facilitated by this channel drops rapidly with distance, as a consequence of the ∼3.4 Å noncovalent gap between base pairs. These predictions are in agreement with most of the experimental data. The rapid decay of electron-transfer rates with distance computed here suggests that biologically controlled DNA electron-transfer events, of importance in DNA repair, must function over relatively short range. Moreover, the predicted distance dependence of electron transfer in DNA is strikingly close to that found in proteins.

DNA-based electron transfer reactions are seen in processes such as biosynthesis and radiation damage/repair, but are poorly understood. What kinds of experiments might tell us how far and how fast electrons can travel in DNA? What does modern theory predict?