Assessment of environmental high-doses using Raman spectroscopy of gamma irradiated MWCNT-OH Nanopowder utilized in radiation accidents

Introduction: The functionalized Multi-Walled Carbon Nanotube with hydroxyl group (MWCNT-OH) due to high aspect ratios (length to diameter), and also excellent mechanical, electrical and thermal characteristics, has great potential applications in flexible electronics, solar cells, antistatic devices, electromagnetic interference shielding, radiation shielding, electrode materials for batteries, lightweight energy storage devices, supercapacitors, piezoelectric sensors, radiation sensors, and dosimeters. Several experiments showed that gamma irradiation can be used to modify the mechanical, and electronic properties of nanostructured carbon materials via the creation of atomic defects in the materials. Raman spectroscopy is a powerful tool for the characterization of carbon nanostructures. According to Raman spectroscopy of nanostructured carbon materials, there are two main peaks of D- band and G-band at 1344 cm-1, 1574 cm-1 respectively. Also there is another peak entitled G' that is indicator of second mode of vibrations in the carbon atoms near 2680 cm-1. The ratio of ID/IG is a characterizing agent for determination of structural defects created in carbon nanostructures. It is expected to increase the amount of ID/IG after gamma irradiation of MWCNT-OH sample at high dose irradiations. Regarding this fact, if the plot of ID/IG versus absorbed dose would be linear, so it can be deduced that this material can be used as a dosimeter. Materials and Methods: In this experimental work, MWCNT-OH Nanopowder with density of 2.1 g/cm3, the outer diameter of 5-15 nm, the inner diameter of 3-5 nm, 50 μm length, the electrical conductivity between 105-107 S/m, containing 1.7 wt% –OH groups was prepared from US Nano Inc and irradiated by gamma rays of 60Co gamma-cell installed in Atomic Energy Organization of Iran-Tehran with dose rate of 1.62 Gy/s within the different doses of 0-30 kGy at room temperature. Raman spectroscopy model Takram P50C0R10 with 532 nm Nd:YAG laser in the range of 100–4600 was applied. Results: According to Raman spectroscopy of the samples, the ratio of ID/IG versus absorbed dose exhibited a linear response in the range of 0-20 kGy and after that saturation effect was dominant. The maximum increase in the ID/IG value in comparison with pristine sample was ±18.7 % at 20 kGy. Conclusion: In this experimental work, MWCNT-OH Nanopowder was prepared and irradiated by gamma rays in different doses of 0-30 kGy at room temperature. The samples were subjected to Raman spectroscopy to determine the defects created in the carbon atoms of the nanostructure materials. Results showed that the amount of ID/IG versus absorbed dose exhibited a linear behavior in the range of 0-20 kGy that can be used for high dose level dosimetry purposes especially assessment of dose in the radiation accidents at nuclear facilities.