Electrochemically template-grown multi-segmented metal-conjugated polymer nanowires

(eng) Anisotropic nano-sized materials are currently of great interest both for improving our fundamental understanding of electrical transport at the nanoscale and for the technological development of many novel electronic devices. Though many various methods are commonly used for fabricating one-component nanowires and nanotubes, only the hard-template technique offers the ability to generate multi-component nanowires, made from or organic and inorganic materials, with a very good control over the composition, spatial distribution and length of the different nanowire blocks. Among the organic materials studied for their electronic properties in 1D environment, conducting polymers (CP) have received a special attention. Based upon the template-based strategy, we have developed an all electrochemical process, consisting in the sequential deposition of metallic and conjugated polymer segments within the pores of polycarbonate membranes. In the present work, we describe the synthesis of various types of bi-, tri- and multi-segmented Metal (Pt, Au) / Conjugated Polymer (polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT) and polyaniline (PANI)) nanowires of different diameters ranging from 30 to 160 nm and, presenting various polymer junction lengths (from a few microns to only a few nanometers). We also report on the fabrication of magnetic nanowires including a conjugated polymer junction and, on the fabrication and characterization of metallic nanowires with an hetero-polymer (PPy-PEDOT) in-wire junction. As the mechanical properties of these hybrid nanowires are key for their use as individually addressable electronic components, a special attention is paid to the morphology and strength of the metal/CP interfaces. For all the systems, the synthesis conditions of the multi-segmented nanowires are optimized in order to improve their mechanical robustness. A study of the electrical transport properties is carried out on various single multi-component nanowires and reveals original electrical properties for some of these hybrid nanostructures nanowires. For instance, an interesting feature of tetra-segmented Au-PEDOT-PPy-Au nanowires, compared to tri-segmented Au-PPy-Au and Au-PEDOT-Au nanowires, is the switching of their electrical characteristics in function of the redox state of the two CP blocks. These observations are correlated with the electronic structure and doping ratio of the CP segments at different redox states. Of course, the highly reproducible synthetic procedure described in this work can be exploited for producing other novel CP-based multisegmented nanowires with desirable electrical properties.