In recent years, two-dimensional atomic-level thickness crystal materials have attracted widespread interest such as graphene, hexagonal boron nitride (h-BN), silicene, germanium, black phosphorus (BP), transition metal sulfides and so on.

Because of the linear dispersion relation and the unique structure of graphene’s Dirac electrons, which can be tuned the ultra‐wide band, this enables more applications in photonics, electronics and plasma optics. As a substrate, hexagonal boron nitride (h‐BN) has an atomic level flat surface without dangling bonds, a weak doping effect and a response in the far ultraviolet area. So the graphene/h‐BN heterostructure is very attractive due to its unique optical electronics characteristics. Graphene and h‐BN which are stacked in different ways could open the band gap of graphene, and form a moiré pattern for graphene on h‐BN and the superlattice in the Brillouin zone, which makes it possible to build photoelectric devices.

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.