Figure 3

Comparison between the luminescence properties of the graphene nanospheres and nanosheets.

(a) Emission spectra from the samples of graphene nanospheres and nanosheets, respectively, with the excitation fluence of 1.47 mJ/cm². The solid lines are the curves fitted to the theoretical model (Eq.1). Inset is a schematic diagram of the scattering-induced hot luminescence emission. The dashed line indicates possible modification of band structure. (b) The emission intensities at 500 nm and 700 nm are plotted as a function of the excitation fluence. The solid lines are the curves fitted to different power functions. (c) The ratios between emission intensities at 700 nm and 500 nm, recorded from nanospheres and nanosheets, are plotted as a function of the excitation fluence, respectively. With increasing the excitation pulse, a blueshift for the emission from nanosheets is observed in contrast to a redshift for the emission in nanospheres. (d) Fitted values of the effective screening vector vs excitation fluence for measurements on the nanospheres and nanosheets, respectively.