Low temperature resistivity of conducting nanotubular polyaniline doped with naphthalenesulfonic acid

The temperature dependence of the resistivity of polyaniline (PANI)-NSA(naphthalenesulfonic acid) samples composed of nanotubes and synthesized by a template-free method has been investigated in the temperature range of 80K less than or equal to T less than or equal to 300K. The ratios of aniline/NSA of the samples are 1:0.25, 1:0.5,1:1,1:2 and 1:3(in mole). On the basis of analyzing the structure characteristics of the samples, we suggest a hopping-tunneling model to explain the mechanism of the transport properties. Although both hopping and tunneling are playing a role at the same time, hopping is dominant when charge carriers conduct inside the nanotubes, while tunneling is dominant between the nanotubes. It is concluded from our experimental results that the resistivity is sensitive to the doping rate. The energy C-0, that is needed for charge carrier conduction, drops down dramatically with the increase of the doping rate. C-0 is nearly constant while the doping rate is near to saturation. By comparing two groups of samples, we study the influence of morphology of PANI-NSA on the C-0, and conclude that C-0 of PANI-NSA samples composed of nanotubes is smaller than those of samples composed of particles.