Anisotropic Polyaniline/SWCNT Composite Films Prepared by in Situ Electropolymerization on Highly Oriented Polyethylene for High-Efficiency Ammonia Sensor

Anisotropic composite films of polyaniline (PANI) with single-walled carbon nanotube (SWCNT) were prepared by in situ electropolymerization on highly oriented high-density polyethylene (HDPE) films. Polarized UV–vis and Raman spectra confirm the anisotropic arrangement of PANI molecular chains in the composite films. The conductivities of 16.6 ± 0.2 and 2.07 ± 0.2 S cm–1 have been obtained for doped PANI/0.8 wt % SWCNT measured along and perpendicular to the direction of the HDPE molecular chain, respectively. The response of PANI/0.8 wt % SWCNT films used as ammonia sensors is much higher along the chain direction of HDPE than that perpendicular to the chain direction of HDPE with an anisotropic ratio of 1.8 at 100 ppm ammonia. This is attributed to the well-ordered array of PANI/0.8 wt % SWCNT induced by the oriented HDPE films. Moreover, the high ammonia response for PANI/0.8 wt % SWCNT may be attributed to the charge-transfer effect between PANI and SWCNT.