160Â MeV Ni12+ ion irradiation effects on the dielectric properties of polyaniline nanotubes

We report on the dielectric properties and a.c. conductivity studies of CSA doped polyaniline nanotubes. Nanotubes of 47-100 nm diameter, were synthesized by the self-assembly method and irradiated using Ni12+ ions of 160 MeV energy with fluences of 1 × 1010, 5 × 1010, 1 × 1011 and 3 × 1011 ions/cm2. X-ray diffraction studies reveal an increase in the degree of crystallinity and consequently, the extent of order of the nanotubes with increasing fluence, but show a lower degree of crystallinity at higher fluence. The decrease in d-spacing for the (100) reflections with fluence is ascribed to the decrease in the tilt angle of the aligned polymer chains. A significant change was seen after irradiation in dielectric and electrical properties which may be correlated with the increased carrier concentration and structural modifications in the polymer films. The surface conductivity of films increases with increasing fluence, which also decreases at higher fluence. The a.c. conduction mechanism for the nanotubes could be explained in terms of correlated barrier hopping model. The existence of polarons as the major charge carriers in the present nanotube system was confirmed by the low values of polaron binding energy, found to decrease with fluence. The hopping distance increases with fluence indicating that the hopping probability increases with fluence.