Electrochemical synthesis and optical properties of helical polyaniline nanofibers

Helical polyaniline (PANI) nanofibers were facilely synthesized via a direct electrochemical method without using any template in the presence of (1S)-(+)-camphor-10-sulfonic acid (d-CSA) or (1R)-(−)-camphor-10-sulfonic acid (l-CSA) as the dopant. The helical morphologies of the PANI nanofibers prepared from potentiostatic deposition were confirmed with SEM and TEM. The helical PANI nanofibers induced by d-CSA and l-CSA exhibited mirror-imaged circular dichroism spectra in the UV–vis range, indicating the stereochemical selectivity of the electrochemical polymerization. The colors and optical activities of these nanofibers can be maintained on an indium-tin oxide (ITO) coated electrode with a dedoping/redoping treatment. The optical activities of the helical PANI nanofibers reversibly varied with different oxidized forms, which were easily controlled by the different potentials applied to the nanofibers.