Graphene Quantum Sheets with Multiband Emission: Unravelling the Molecular Origin of Grapherie Quantum Dots

The dependence of the fluorescence in graphene quantum dots on the excitation wavelength has been the focus of several studies recently. While some studies attributed their multichromophoric behavior to core and surface states, others related it to the differently sized nanodomains of sp(2)-hybridized carbon in an amorphous matrix. Herein, colloidal graphene quantum sheets and nanoflakes were directly synthesized via low temperature catalytic chemical vapor deposition (CVD). These graphene nanostructures were found to exhibit well-resolved multiemission bands in the visible region. Based on the X-ray photoelectron, FT-IR and Raman spectroscopies as well as density functional theory (DFT) calculations, the role of polycyclic aromatic hydrocarbons (PAHs) was identified as the building blocks of graphene quantum dots.