Abstract
Thanks to their excellent thermal and optical properties, graphene oxide quantum dots (GOQD) have been extensively explored for several applications, such as composite material, optoelectronic devices, solar cells, and fluorescence materials, among others. Consequently, GOQDs are commercially available suspended in a solution. However, the density, size, and crystallinity of commercially available GOQDs can differ a lot from one manufacturer to another, which rarely provide exhaustive information about them. Furthermore, a recent report has questioned the quality of graphene-based materials produced by liquid phase exfoliation. Here a statistical analysis of the quality of commercially available GOQDs, using transmission electron microscope (TEM), is presented. This technique enables to observe the internal structure, thickness, lattice structure, orientation, and local defects of the samples at atomic scale. High resolution TEM images reveal that the thickness of the GOQDs is not homogenous from center to edges within one single domain. The edges show hexagonal lattice (monolayer) while the central location shows to be rhomboidal structure (multilayer). This work provides clear statistical information about the quality of the commercially available GOQDs.