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

Abstract

A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of PdCl4(-2) with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV-vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5-45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1-1.4 S cm(-1)), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm(-1)). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (E(a )= 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd.

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

“…These results indicate some of the current ows through the Cu metallization in contrast to the case of palladium metallization on polyimidazole/DNA nanowires, i.e., Pd/ polyimidazole/DNA. 10…”

“…This stands in contrast to the case of Pd on polyimidazole/DNA structures where metallization had no signicant effect on the conductivity of the polymer/DNA nanowire. 10 The conduction pathway in Cu/polyNPPBH/DNA must therefore involve the Cu metallization. Second, the conductivity of Cu/polyNPPBH/DNA is less than of polypyrrole/DNA nanowires; 21,39 this might be expected on the basis of the known bulk polyNPPBH conductivity, but it is worth noting that the conduction via the Cu metallization would not be detectable on a polypyrrole/DNA nanowire and in this respect the deleterious effect of the pyridine group on the polymer conductivity is advantageous in the present case.…”

“…Single component systems of such DNA-templated nanowires are now quite common, but there are relatively few examples of metalconducting polymer hybrid nanowires made from both inorganic and organic materials. 9,10 Metals and conductive polymers have interesting electrical and optical properties that are appropriate for numerous applications. 4 Amongst metal nanowires, Cu nanowires are of particular interest because of the essential role of the metal in interconnects in electronics.…”

“…More recently, we were able to compare the conductivities of the polymer/DNA and metal/polymer/DNA nanowires in the Pd/ poly(imidazole)/DNA system, but the conduction pathway was found to be dominated by the polymer rather than the metal. 10 Polypyrrole (PPy) and its derivatives have been extensively studied because their ease of synthesis allows experimenters to combine chemical functionality with electronic conductivity. 18,19 In this report, we prepare an N-propylpyridine derivative of pyrrole (NPPBH) and show that upon metallization with Cu, Cu/polyNPPBH/DNA nanowires are indeed more conductive than polyNPPBH/DNA nanowires.…”

Inkjet printing and electrical characterisation of DNA-templated cadmium sulphide nanowires

“…DNA-templated nanowires are prepared by nucleating the growth of conductive materials (semiconductors [1][2][3][4][5][6][7][8][9], metals [10][11][12][13][14][15][16][17][18][19], and conductive polymers [20][21][22][23][24][25]) on DNA molecules.…”