Etching single-wall carbon nanotubes into green and yellow single-layer graphene quantum dots

Single-walled carbon nanotubes (SWCNTs) have been used to prepare single-layered graphene quantum dots (GQDs) through a simple and green hydrothermal etching method. After the characterization of products and intermediates with scanning electronic microscopy, Raman and FTIR, a possible mechanism has been proposed for the formation of GQDs. The treatment of SWCNTs has resulted in two kinds of GQDs (i.e. GQD1 and GQD2), both of which are monodisperse and single-layered nanosheets with an average lateral dimension of 8 nm and an average height of 0.5 nm. Excited with 365 nm UV light, aqueous solutions of GQDs1 and GQDs2 give green and yellow luminescence, respectively. The differences in optical property between GQDs1 and GQDs2 mainly results from their differences in degree of oxidation.