Synthesis, Manipulation and Conductivity of Supramolecular Polymer Nanowires

The synthesis of supramolecular conducting nanowires can be achieved by using DNA and pyrrole. Oxidation of pyrrole in DNA‐containing solutions yields a material that contains both the cationic polypyrrole (PPy) and the anionic DNA polymers. Intimate interaction of the two polymer chains in the self‐assembled nanowires is indicated by FTIR spectroscopy. AFM imaging shows individual nanowires to be continuous, ≈5 nm high and conformationally flexible. This feature allows them to be aligned by molecular combing in a similar manner to bare DNA and provides a convenient method for fabricating a simple electrical device by stretching DNA/PPy strands across an electrode gap. Current–voltage measurements confirm that the nanowires are conducting, with values typical for a polypyrrole‐based material. In contrast to polymerisation of pyrrole on a DNA template in bulk solution, attempts to form similar wires by polymerisation at surface‐immobilised DNA do not give a continuous coverage; instead, a beads‐on‐a‐string appearance is observed suggesting that immobilisation inhibits the assembly process. Templating polymer nanowire growth with DNA: Supramolecular conducting polymer nanowires were synthesised by oxidising pyrrole in the presence of DNA, which acts as a template. The AFM image shows immobilised DNA on mica after in situ polymerisation of pyrrole. Non‐specific absorption of polymer particulates is evident as bright spots (scale bar=200 nm).