Post-γ -irradiation effects on structural, optical and morphological properties of chemical vapour deposited MWCNTs

Abstract In this work, the effect of γ-irradiation with 1.25 MeV average energy (Co-60) was studied on the structural, optical and morphological properties of chemical vapour deposited MWCNTs at 10–60 kGy dose. The XRD spectra with the peak at 2θ ~ 26.08° of (002) plane confirm the MWCNTs formation and conspicuous modifications were observed after γ- irradiation. The UV–Vis studies show that the UV lower wavelength shifts towards the higher region with increasing γ- dose, bandgap decreasing from 3.57 eV to 3.33 eV (372 nm–347 nm) because of the generation of charge trapping of the radiolytic holes or electrons, which change the valence and conduction bandgap in electronic states. The FTIR results provided confirmation of the attachment of hydroxyl and carboxyl functional groups to the MWCNTs sidewalls whereas after γ- irradiation caused significant changes in the structure of the sidewalls of MWCNTs. The Raman spectra confirmed the ID/IG ratio decreases after γ- irradiation which is due to the enhancement in defects through the interaction between MWCNTs and photons during γ-irradiation. The TEM and FESEM results confirmed the inter-mingling or agglomeration of the network of nanotubes having varying diameters of about 40–60 nm on account of the interaction of γ-ray. SAED pattern shows a dispense halo pattern due to the presence of amorphous carbon.