High temperature acidic oxidation of multiwalled Carbon nanotubes and synthesis of Graphene quantum dots

The acid oxidation of carbon nanotube generally results in opening the close ends of the nanotube and to make surface modifications. Herewith, Multiwall carbon nanotubes (MWCNTs) were oxidized in acids at high temperature experimental conditions which led to the formation of graphene quantum dots (GQDs). High resolution transmission electron microscope (HRTEM), energy dispersive X-ray spectroscopy (EDS), IR Infrared study showed the formation of 5-10 nm diameter GQDs and their crystalline structure having the inter-planner distance of 2.40 Å and 2.14 Å were confirmed by the electron diffraction. The UV visible spectroscopy showed the lowest exciton peak at 4eV. Photoluminescence (PL) studies showed the Photoluminescence peak in visible range which is independent of excitation wavelengths. A mechanism for the formation of highly crystalline graphene quantum dots during the high temperature acid oxidation of MWCNTs is proposed in the paper.