Morphology and electrical properties of template-synthesized polypyrrole nanocylinders

Polypyrrole nanocylinders were fabricated by chemically synthesizing polypyrrole within the pores of nanoporous polycarbonate particle track-etched membranes. The morphology of the nanostructures was characterized by transmission electron microscopy and scanning electron microscopy. The nanocylinders were observed to be cigarshaped, with the diameter at the center being up to 2.5 times the diameter at the ends. The electrical conductivity of the nanocylinders was measured by leaving the nanocylinders embedded in the insulating template membrane and measuring the trans-membrane resistance. The cigar-like shape of the nanocylinders was taken into account in calculating the conductivity. Contrary to previous reports, the smallest diameter nanocylinders exhibited a slightly lower conductivity relative to the larger diameter nanocylinders. The temperature dependence of the resistance and magnetoresistance was in accordance with Mott variable range hopping at temperatures above 5 +/- 1 K and Efros-Shklovskii variable range hopping at temperatures below 5 +/- 1 K. Based on the measurements in the Mott regime, the localization length, the density of states at the Fermi energy, and the temperature dependence of the average hopping distance were calculated. (C) 2002 Elsevier Science B.V. All rights reserved.