DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates.

DNA templated nanowires of a pentynyl-modified poly2-(2-thienyl)-pyrrole undergo functionalisation via"click chemistry" and retain their 1D-nanostructure and conductive properties.

Templating the electroless reduction of metal ions on DNA is now an established route to the preparation of nanowires and can be particularly useful for the formation of nanowires in the desirable <10 nm size range. However, different preparation conditions produce nanowires of widely different morphologies and conductivities. We describe a method for the synthesis of Cu nanowires in which electroless metal deposition is carried out on DNA 'template' molecules in bulk solution. Though analogous to previous surface-based routes, importantly this now produces conductive material. AFM was used to evaluate the size and morphology of the resulting nanowires; a mean nanowire diameter of 7.1 nm (standard deviation = 4.7 nm) was determined from a statistical analysis of 100 nanowires and the Cu coatings were continuous and smooth. These findings represent a notable improvement in nanowire morphology in comparison to the previous surface-based routes. UV-vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to confirm formation of Cu(0) metal takes place during nanowire synthesis, and additional scanning probe microscopy techniques were employed to probe the electrical properties of the nanowires. The nanowires are less conductive [resistivity ∼ 2 Ω cm] than bulk Cu, but much more conductive than nanowires prepared by the analogous method on surface-bound DNA. Using an extension of our thermodynamic model for DNA-templating, we show that the templating process in bulk solution favours the formation of continuous nanowires compared to templating on surface-bound DNAX-ray photoelectron spectra were obtained at the National EPSRC XPS User's Service (NEXUS) at Newcastle University, an EPSRC mid-range facility. This work was financially supported by Newcastle University, EU ITN NANOEMBRACE (Contract No. 316751) and Intel Ireland Ltd (with special thanks to Bernie D. Capraro, Research Programme Manager