Polyaniline nanofibers

[2] Properties that make polyaniline useful can be seen in the nanofiber form as well, such as facile synthesis, environmental stability, and simple acid/base doping/dedoping chemistry.

These and other properties have led to the formation of various applications for polyaniline nanofibers as actuators, memory devices, and sensors.

[3][4][5][6] Other less common methods include nanofiber seeding, electrosynthesis, electrospinning, and preforming polymerization in dilute aniline solutions.

However, if the reaction is left uncontrolled, heterogeneous nucleation will begin to dominate as the polyaniline will preferentially grow on existing particles, leading to irreversible agglomeration.

[4][6] A typical reaction involves an aqueous solution of acid and oxidant and an organic layer of aniline together.

As polymerization proceeds, the polyaniline nanofibers will diffuse into the water layer, leaving the reactive interface.

These asymmetric films demonstrate rapid reversible actuation in the presence of acids and bases, in the form of bending and curling.

The advantages polyaniline nanofiber asymmetric films have over other actuators include the ease of synthesis, large degree of bending, patternability, and no delamination.

[9] Research has shown that polyaniline nanofibers can also be used to create nonvolatile plastic digital memory devices when decorated with various metal, such as gold, nanoparticles.

[11] This performance difference has been attributed to their high surface area, porosity, and small diameters which enhance diffusion of materials through the nanofibers.

[13] NO2 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.

One study proposes polyaniline nanofiber composites with metal salts for the detection of hydrogen sulfide.

Another study decorated polyaniline nanofibers with gold nanoparticles to detect volatile sulfur compounds in expired human breath.

Scanning electron microscope (SEM) image of polyaniline nanofiber film. [ 1 ]
Polymerization pathways of polyaniline and polyaniline nanofibers, as well as the doped/dedoped oxidation/reduction chemistry that can occur.
Route I shows the heterogeneous nucleation route, where the nanofibers are formed, followed by secondary growth on the wires which cause agglomeration. Route II shows the homogeneous nucleation route, where only nanofibers are formed.