160 MeV Ni12+ ion irradiation effects on the structural, optical and electrical properties of spherical polypyrrole nanoparticles

•Upon SHI irradiation the average diameters of PPy nanoparticles increases.•Crystallinity of PPy nanoparticles increases with increasing ion fluence.•IR active vibrational bands have different cross sections for SHI irradiation.•Upon SHI irradiation optical band gap energy of PPy nanoparticles decreases.•Upon SHI irradiation thermal stability of PPy nanoparticles increases.

In this study we report 160 MeV Ni12+ swift heavy ion irradiation induced enhancement in the structural, optical and electrical properties of spherical polypyrrole (PPy) nanoparticles. High resolution transmission electron microscope results show that the pristine PPy nanoparticles have an average diameter of 11 nm while upon irradiation the average diameter increases to 18 nm at the highest ion fluence of 1 × 1012 ions/cm2. X-ray diffraction studies show an enhancement of crystallinity and average crystallite size of PPy nanoparticles with increasing fluence. Studies of Fourier transform infrared spectra suggest the structural modifications of different functional groups upon irradiation. It also reveals that different functional groups have different sensitivity to irradiation. The infrared active N–H vibrational band at 3695 cm−1 is more sensitive to irradiation with a formation cross-section of 5.77 × 10−13 cm2 and effective radius of 4.28 nm. The UV–visible absorption spectra of PPy nanoparticles show that the absorption band undergoes a red shift with increasing fluence. Moreover upon irradiation the optical band gap energy decreases and Urbach’s energy increases with fluence. Thermo-gravimetric analysis studies suggest that upon irradiation the thermal stability of PPy nanoparticles increases which may be attributed to their enhanced crystallinity. Current–voltage characteristics of PPy nanoparticles exhibit non-Ohmic, symmetric behavior which increases with fluence.