Effect of humidity on electrical properties of micro/nano-polyaniline thin films with different D-CSA doping degree

In this paper, the influence on humidity sensitive characteristics of micro/nano-polyaniline (PANI) thin films with different doping degree of (1S)-(+)-10-camphorsulfonic acid (D-CSA) is investigated. The PANI is synthesized by an in situ chemical oxidative polymerization of aniline in the presence of ammonium peroxydisulfate (APS) acidic at ice-water bath for 10 h, and characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. Then, the composite films are formed between interdigital electrodes on a silicon (Si) substrate via self-assembly method. The humidity sensitive characteristics of the PANI films are measured. The experimental results show that the conductivity of PANI increases with increasing the molar ratios of [D-CSA]/[Ani]. Besides, the humidity sensitivity of the PANI films enhances with increasing the molar ratios of [D-CSA]/[Ani] and decreasing the layer number of PANI films, respectively. The PANI films with [D-CSA]/[Ani] molar ratio of 1.0 ([D-CSA]/[Ani] = 1:1) has higher sensitivity. The results indicate that the doping degree of D-CSA actually influences on the humidity sensitive characteristics of PANI thin films, and may be referencing significance for the fabrication of better humidity sensor. (C) 2012 Elsevier Ltd. All rights reserved.