Properties and stability of polyaniline nanofiber ammonia sensors fabricated by novel on-substrate method

Alumina substrates with interdigitated electrodes were coated with polyaniline (PANI) nanofibers using our newly developed on-substrate method. Uniform HCl-doped PANI nanofibers were reproducibly formed by optimizing the polymerization time. The responsiveness of the HCl-doped PANI nanofiber NH3 gas sensor was affected by the subsequent heat-treatment time in air, with longer heat treatment resulting in a greater response. Furthermore, redoping with DiOHP instead of HCl was successfully performed without damaging the nanofiber structures. The DiOHP-doped nanofiber sensor demonstrated excellent reproducibility and stability compared with the HCl-doped nanofiber sensor. The DiOHP-doped sensor showed sufficient detection sensitivity for NH3 at concentrations of 25 ppm or less.