text: Polyaniline nanofibers have been shown to be incredibly successful as chemical sensors, as they perform better than conventional polyaniline films in numerous tests. This performance difference has been attributed to their high surface area, porosity, and small diameters which enhance diffusion of materials through the nanofibers. Polyaniline nanofiber sensors function through a change in resistance. The polyaniline nanofiber film is placed on an electrode, where a current flows through. The resistance of the electrode changes when the target interacts with the film, which allows the target to be detected.
  One study proposes the creation of hydrogen gas sensors using polyaniline nanofibers. It shows that both doped and dedoped polyaniline nanofibers can be used for detection of hydrogen gas through resistance changes, but the dedoped nanofibers were more stable and had better reproducibility.
  Another study shows the potential of polyaniline nanofibers as NO gas sensors. NO gas acts as a strong oxidizing agent to the emeraldine form of polyaniline nanofibers, which causes resistance changes greater than three orders of magnitude at 100 ppm.
  Sensing targets can be expanded through adding materials to the polyaniline nanofibers. One study proposes polyaniline nanofiber composites with metal salts for the detection of hydrogen sulfide. Hydrogen sulfide is a weak acid that is dangerous at low ppm, but polyaniline nanofibers can only give a robust response to strong acids. Metal salts can react with hydrogen sulfate to form a metal sulfide precipitate and a strong acid. By combining metal salts and polyaniline nanofibers, detection of hydrogen sulfide can be performed.
  Another study decorated polyaniline nanofibers with gold nanoparticles to detect volatile sulfur compounds in expired human breath. These sensors can potentially be used in various breath analyses and also in disease diagnosis for diseases with malodor biomarker gases.
  Humidity sensors have also been prepared using polyaniline nanofibers. These sensors were prepared through electrospinning of a N,N-dimethylformamide solution of polyaniline nanofibers, poly(vinyl butyral) (PVB), and poly(ethylene oxide) (PEO). These sensors were shown to have high sensitivity, with resistance changes of three orders of magnitude. Furthermore, the sensors showed good sensing linearity, fast response, small hysterics, and good repeatability.