Structural and optical properties of self-assembled polypyrrole nanotubes

Polypyrrole (PPy) nanotubes doped with camphorsulfonic acid (CSA) have been synthesized using self-assembly polymerization method. The average diameter of the resulting PPy nanotubes has been controlled by varying the dopant/monomer molar ratio. Formation mechanism of PPy nanotubes has been discussed at length. The formation of PPy nanotubes has been confirmed from the high resolution transmission electron microscopy (HRTEM) studies. FTIR studies depict that the “effective conjugation length” of PPy nanotubes increases with increasing CSA/Py molar ratio. UV-vis studies reveal the formation of polaron and bipolaron bands within the band gap of neural PPy, confirming the doping of PPy nanotubes with CSA. The optical band gap energy decreases with increasing CSA/Py ratio and also the thermal stability of PPy nanotubes gets enhanced with increasing dopant/monomer molar ratio.