Effects of low gamma irradiation dose on the photoluminescence properties of graphene quantum dots

We prepared graphene quantum dots (GQDs) using electrochemical approach. The luminescent properties of GQDs at various excitation wavelengths are examined. In order to study the possibility to improve these properties, we applied a low dose of gamma irradiation (15 kGy) on GQDs dissolved in two media: water and 4 % isopropyl alcohol solution. Upon gamma irradiation of water, various free radical species are formed and they usually cause oxidation. In the presence of isopropyl alcohol in water, during irradiation, oxygen contained radicals are quenched and only hydrogen radicals can survive and reduce the material exposed to irradiation. Morphology of GQDs is examined by atomic force and transmission electron microscopy. After gamma irradiation the increase of photoluminescence was noticed for both GQD samples. A higher intensity of photoluminescence is detected for GQDs irradiated in 4 % isopropyl alcohol solution. This result shows that further increase of gamma irradiation dose has a great potential for improvement of luminescence properties of GQDs.