Solution-based DNA-templating of sub-10 nm conductive copper nanowires

Abstract

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

Chemical and electrochemical routes to DNA-templated rhodium nanowires

“…80,81 Such increases in the material resistivity upon a reduction to the nanometre size regime are not uncommon, with the preparation of other metals in 1D nanoscale form showing increases in resistivity by several orders of magnitude. [82][83][84] In the case of the Rh structures reported here, this increase in resistivity is suggested to be most likely the result of the granular character of the Rh coatings on the DNA strands, as indicated by AFM and XRD, and leading to electron scattering at particle-particle interfaces and the nanowire surface (note: resistance caused by surface scattering is expected to become increasingly signicant as the diameter of the nanowire approaches and decreases below the bulk mean free path). There may also be a contribution from the formation of the oxyhydroxide layer on the nanowires surfaces, as indicated by the XPS data.…”

Preparation and electrical properties of a copper-conductive polymer hybrid nanostructure

“…14 Electrically conducting DNAtemplated Cu nanostructures have since been prepared via multiple seeding steps 15 or by carrying out the templating with the DNA dissolved in bulk solution at low concentrations of Cu(II). 16 One approach to improve the growth of metals at DNA-based structures is the introduction of a metal binding group into the monomer so that aer templating the polymer on DNA, electroless reduction of a metal ion leads to a core-shell structure: metal/polymer/DNA. Alkynyl-functionalised thienylpyrrole (TP) monomers were shown to enhance the smoothness of Ag/ polyalkynyl-TP/DNA nanowires compared to Ag/DNA.…”

Nanosheets and 2D-nanonetworks by mutually assisted self-assembly of fullerene clusters and DNA three-way junctions

“…21 This could decrease the cost of synthesis and tedious periodic assembly of long multiple DNA components. 22 On the other hand, DNA has been used as a scaffold or template in the bottom-up assembly of metal ions, [23][24][25] small molecules, 26 oligomers, 27,28 polymers, 29,30 and nanoparticles, 31,32 into various nanostructures. Moreover, the long range ordered assembly of short DNA strands into one dimensional (1D) nanobers/nanowires was reported using various design strategies such as DNA templated assembly, 33,34 complementary hydrogen bonding, 35 DNA condensation 36,37 and p-chromophore assisted self-assembly.…”