Electronic transport in single polyaniline and polypyrrole microtubes

Completely doped submicrotubes (90-560 nm in diameter) of conducting polyaniline and polypyrrole have been synthesized by a template-free method. The measurements of resistivity, I-V curve and magnetoresistance of single polyaniline tube by a standard four-probe technique are presented. Due to the elimination of large intertubular contact resistance, the single polyaniline tube shows a considerably high conductivity and a small positive magnetoresistance. In particular, a crossover from Mott to Efros-Shklovskii variable-range hopping conduction at about 66 K is observed in the single polyaniline tube owing to a strong electron-electron interaction with a Coulomb gap of 11.2 meV. This strong Coulomb interaction is also proved by the I-V curves, which show an obvious zero-bias anomaly at low temperatures. In addition, the temperature dependences of electrical conductivity of single polypyrrole submicrotubes with different diameter have also been studied. The room-temperature conductivity of single polypyrrole tube increases from 0.13 to 73 S/cm when the outer diameter decreases.