ELECTRIC PROPERTY OF INSULATED MOLECULAR WIRE FORMED BY CONJUGATED CONDUCTING POLYMERS

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We have recently found a novel kind of molecular wire formed by conducting polymer and cyclodextrin (CD) with cyclic form. CD molecules were threaded onto a typical soluble conducting polymer, polyaniline (PANI), in solution and formed a necklace-like inclusion complex. This inclusion complex can be regarded as insulated molecular wire, because a conducting polymer is covered by CD molecules as insulator.In this study, we formed the insulated molecular wire of the molecular nanotube synthesized from CDs and a conducting polymer, PANI, and observed the structure of the insulated molecular wire by atomic force microscopy (AFM). As a result, we observed rod-like forms of the insulated molecular wires clearly by AFM in non-contact mode. The inclusion interaction between CD and PANI was too weak to form the inclusion complex at room temperature. In contrast, the molecular nanotube can form the insulated molecular wire at room temperature. These results suggest that the molecular nanotube has much stronger inclusion interaction with PANI than CD.Further, we found that the insulated molecular wire was moved or cut with the AFM tip in the contact mode. These results indicate that the insulated molecular wire can be manipulated by AFM.This technique is applicable for the connection between any two points with the insulated molecular wire.Finally, we doped the insulated molecular wire. It is well known that undoped conducting polymer shows low conductivity and the conductivity increases drastically with doping as well as semiconductors. The results of the absorption spectrum and the AFM observation indicated that the insulated molecular wire could be doped by addition of HCl. It is expected that the doped insulated molecular wire has high conductivity.The results in this study indicate that the insulated molecular wire of conducting polymers and molecular nanotubes is a promising candidate novel material for molecular wire, which has attracted interests of many researchers.