萘磺酸掺杂对纳米管结构聚苯胺低温电阻率的影响

Low temperature resistivity of conducting nanotubular polyaniline doped with naphthalenesulfonic acid

通过研究用自组装法制备的萘磺酸掺杂的纳米管结构聚苯胺 (苯胺与萘磺酸的摩尔比分别为 1∶0 2 5 ,1∶0 5 ,1∶1,1∶2 ,1∶3)的电阻率 温度依赖关系 (测量温区为 80— 30 0K) ,仔细分析聚苯胺的结构形貌特征 ,提出了变程跳跃 隧道穿透混合模型 :认为在萘磺酸掺杂的纳米管结构聚苯胺样品中 ,跳跃和隧穿两种机制同时起作用 ,载流子沿纳米管传导是变程跳跃过程起主要作用 ,而载流子在纳米管之间的传导是隧穿过程起主要作用 .实验结果表明 ,不同浓度的萘磺酸掺杂对样品的低温电阻率的影响很大 ,随着掺杂浓度增加 ,载流子传导所需克服的能垒C0 迅速减小 ,当掺杂接近饱和时 ,C0 不再减小 .实验中还研究了不同形貌对电阻率的影响 。

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.