Comparison of carbonized and activated polypyrrole globules, nanofibers, and nanotubes as conducting nanomaterials and adsorbents of organic dye

Abstract

Polypyrrole globules, nanofibers and nanotubes were activated by their carbonization at 650 °C in the 3:1 mass excess of molten potassium hydroxide in argon. They have been compared with parent polypyrroles and analogous samples obtained by the carbonization in the absence of hydroxide. The yields after activation, 12–18 wt%, were lower compared to the carbonization, which exceeded 50 wt%. The changes in molecular structure are discussed on the basis of FTIR and Raman spectra. One-dimensional morphologies, especially nanotubes, were superior to globules in most respects. They have higher conductivity close to 10 S cm−1, which was reduced by two orders of magnitude after carbonization but partly recovered after activation. The specific surface areas of nanotubes of the order of tens m2g−1 was several times higher compared with globules. They have not changed after carbonization but increased several times upon activation. The activated polypyrroles were tested as adsorbents of anionic azo dye, Reactive Black 5. Activated nanotubes performed the best in adsorption followed by parent nanotubes and nanofibers. The mechanism of dye adsorption is proposed by considering the presence of dye tautomers identified on the basis of FTIR spectra.