Networks of DNA-templated palladium nanowires: structural and electrical characterisation and their use as hydrogen gas sensors

Abstract

Electroless templating on DNA is established as a means to prepare high aspect ratio nanowires via aqueous reactions at room temperature. In this report we show how Pd nanowires with extremely small grain sizes (< 2 nm) can be prepared by reduction of PdCl4(2-) in the presence of lambda-DNA. In AFM images the wires are smooth and uniform in appearance, but the grain size estimated by the Scherrer treatment of line broadening in X-ray diffraction is less than the diameter of the wires from AFM (of order 10 nm). Electrical characterisation of single nanowires by conductive AFM shows ohmic behaviour, but with high contact resistances and a resistivity (-10(-2) omega cm) much higher than the bulk value for Pd metal (-10(-5) cm @ 20 degrees C). These observations can be accounted for by a model of the nanowire growth mechanism which naturally leads to the formation of a granular metal. Using a simple combing technique with control of the surface hydrophilicity, DNA-templated Pd nanowires have also been prepared as networks on an Si/SiO2 substrate. These networks are highly convenient for the preparation of two-terminal electronic sensors for the detection of hydrogen gas. The response of these hydrogen sensors is presented and a model of the sensor response in terms of the diffusion of hydrogen into the nanowires is described. The granular structure of the nanowires makes them relatively poor conductors, but they retain a useful sensitivity to hydrogen gas.

Metal-conductive polymer hybrid nanostructures: preparation and electrical properties of palladium–polyimidazole nanowires

“…Pd/DNA was prepared in the same way as Pd/PIm/DNA, but using λ-DNA instead of PIm/DNA on which to carry out the electroless deposition of Pd, as previously reported. 27 Deposition of Pd/PIm/DNA nanowires on substrates for microscopy. In order to facilitate the alignment of individual nanowires on Si/SiO2 substrates, the hydrophobicity of the SiO2 was increased by treating the Si/SiO2 substrates with chlorotrimethylsilane (Me3SiCl) vapor for about 10 min.…”

“…Metals, including Pd, can be readily assembled on DNA via the chemical or photoinduced reduction of DNAcomplexed metal ions. 10,[25][26][27] Electronic transport measurements have been made with DNA-templated metal wires and the results demonstrate that they may be used in electronic circuits and sensors. 6,7 However, the growth of metals on DNA does not always lead to smooth structures; objects with dendritic morphologies are common.…”

“…32,33 The choice of palladium is motivated by the fact that this metal is known to form relatively smooth DNA-templated nanowires with which the electrical properties of the hybrid can be compared. 27 The nanowires are first characterised chemically (FTIR, XPS) and structurally (AFM, SEM). We then show that it is possible to discriminate between different charge transport pathways in such a structure using a range of probe microscopy and two-terminal I-V characterisation techniques to investigate the electronic conductivity of these nanowires.…”

Metallic Conductive Nanowires Elaborated by PVD Metal Deposition on Suspended DNA Bundles

“…www.small-journal.com www.advancedsciencenews.com small 2017, 13,1700956 DNA bundles, which probably are not strictly at the top of the electrodes, but probably a little bit shifted down along the sidewalls. So, selective metal deposition should be done at the anchoring points, thus creating locally a decrease of the contact resistance between electrodes and NWs.…”

DNA-templated nanowires: morphology and electrical conductivity

“…Schematic showing the structure of the Pd NWs which comprise small crystallites of diameter x 1.6 nm by analysis of the Xray diffraction pattern linewidth, but a relatively smooth & uniform appearance in AFM images 55. This journal is © The Royal Society of Chemistry 2014Nanoscale, 2014, 6, 4027-4037 | 4033…”