Engineering polypyrrole nanotubes by 100 MeV Si9 + ion beam irradiation: Enhancement of antioxidant activity

•Polypyrrole nanotubes have been irradiated by 100 MeV Si9 + ion beam.•X-ray diffraction reveals the increase in amorphicity with increase in ion fluence.•Thermal stability of nanotubes decreases with increase in ion fluence.•Enhancement in antioxidant activity is observed with increase in ion fluence.

In this work, the effect of 100 MeV Si9 + ion beam with four different fluences on antioxidant and structural properties of polypyrrole nanotubes has been investigated. Polypyrrole nanotubes have been synthesized by reactive self degrade template method. Fragmentation of the polypyrrole nanotubes at higher fluence is revealed from the high resolution transmission electron micrograph (HRTEM) and X-ray diffraction (XRD) results. The decrease in characteristics band of polypyrrole in Fourier transmission of infrared spectra (FTIR) spectra suggests the main chain scission of polypyrrole during irradiation. The free radical scavenging activity of pristine and irradiated samples are evaluated by using α, α-diphenyl-β-picrylhydrazyl (DPPH) assay. The decline of the UV–visible absorbance at 516 nm suggests the neutralization of DPPH free radicals through the reaction with polypyrrole. Significant increase in antioxidant activity of polypyrrole nanotubes is observed with increase in ion fluence.