Modification of surface functionality and interlayer spacing of multi-walled carbon nanotubes using γ-rays

The surface functionality and interlayer spacing changes induced by gamma-ray irradiation were investigated in multi-walled carbon nanotubes (MWCNTs). The modification effect of MWCNTs irradiated in air and epoxy chloropropane (ECP) was characterized by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. The results indicated that c-ray irradiation in two different media improved the amount of oxygen-containing functional groups on nanotube surface, and the irradiation in ECP was more efficient. Compared with the pristine MWCNTs, the MWCNTs irradiated in air exhibited a decrease in width of G band and intensity ratio of D to G band in the Raman spectra and an increase in intensity and diffraction angle of (002) characteristic x-ray peak. However, the MWCNTs tended to show the opposite behaviors in Raman spectra and x-ray diffraction patterns after they were irradiated in ECP. This preliminary study suggests that gamma-ray irradiation in air can meaningfully decrease the interlayer distance of MWCNTs and improve the graphitization of MWCNTs, while irradiation in ECP disorders and breaks the structure of MWCNTs. It is worth expecting that MWCNTs can be functionalized by gamma-rays in reactive liquid and also be employed for preventing gamma-ray radiation from reaching sensitive materials at least for short term experiments in air. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552598]