Preparation, characterization and scanned conductance microscopy studies of DNA-templated one-dimensional copper...

The synthesis of one-dimensional metal nanostructures can be achieved through the use of DNA molecules as templates to control and direct metal deposition. Copper nanostructures have been fabricated using this strategy, through association of Cu(2+) ions to DNA templates and reduced with ascorbic acid. Due to the possibility that the reduction of the Cu(2+) can result in the preferential formation of Cu(2)O over metallic Cu(0), X-ray photoelectron spectroscopy and X-ray diffraction have been carried out to establish the chemical identity of the nanostructures. Conclusive evidence is found that reduction of the Cu(2+) ions does result in the formation of the desired metallic Cu(0) structures. The morphology of the nanostructured Cu(0) material has also been observed by atomic force microscopy, showing the structures to have a "beads-on-a-string" appearance and being 3.0-5.5 nm in height. The electrical properties of the structures have been investigated by scanned conductance microscopy, showing the Cu(0) structures exhibit much larger electrical resistance than expected for a metallic nanowire. This is thought to be a consequence of their "beads-on-a-string" morphology and small lateral dimensions (sub-10 nm); both these factors would be expected to increase the electron scattering rate, and, further, there are likely to be significant tunneling barriers at the Cu(0) particle-particle junctions.