Abstract
The optical properties of graphene quantum dots (GQDs) were investigated theoretically. We focused on the photoinduced charge transfer and electron-hole coherence of single-layer graphene in the electronic transitions in the visible regions. Surface functionalization with donor or acceptor groups produced a red shift in the absorption spectrum, and electrons and holes were highly delocalized. The recombination of excited, well-separated electron-hole (e–h) pairs can result in enhanced fluorescence. This fluorescence enhancement by surface functionalization occurs because of the decreased symmetry of the graphene resulting from the roughened structure of the surface-functionalized GQDs.
Highlights
Graphene is a single atomic layer that consists of a two-dimensional honeycomb lattice of carbon atoms
We investigated the effects of surface functionalization on the optical properties of graphene quantum dots (GQDs) with a lateral dimension of approximately 2 nm, mainly focusing on the charge-transfer and e–h coherence in the electronic transition of GQDs
The calculated absorption spectra of both GQDs in the visible region are presented in Fig. 2 and demonstrate that the optical absorption peaks of
Summary
Graphene is a single atomic layer that consists of a two-dimensional honeycomb lattice of carbon atoms. The PL mechanism of GQDs has been interpreted as the minimization of thermalization resulting from electron-phonon scattering[22], or the formation of an excited-state relaxation channel, which causes inelastic light scattering by electric doping[23]. Kim attributed this behavior to fast carrier–carrier scattering[24], which encourages the direct recombination of the excited electron–hole (e–h) pairs that produce this PL before the carriers are thermalized in the lattice. Our results can facilitate a deeper understanding of the origin of the optical properties of GQDs
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