title: Anomalous Light Emission and Wide Photoluminescence Spectra in Graphene Quantum Dot: Quantum Confinement from Edge Microstructure.
abstract: The physical origin of the observed anomalous photoluminescence (PL) behavior, that is, the large-size graphene quantum dots (GQDs) exhibiting higher PL energy than the small ones and the broadening PL spectra from deep ultraviolet to near-infrared, has been debated for many years. Obviously, it is in conflict with the well-accepted quantum confinement. Here we shed new light on these two notable debates by state-of-the-art first-principles calculations based on many-body perturbation theory. We find that quantum confinement is significant in GQDs with remarkable size-dependent exciton absorption/emission. The edge environment from alkaline to acidic conditions causes a blue shift of the PL peak. Furthermore, carbon vacancies are inclined to assemble at the GQD edge and form the tiny edge microstructures. The bound excitons, localized inside these edge microstructures, determine the anomalous PL behavior (blue and UV emission) of large-size GQDs. The bound excitons confined in the whole GQD lead to the low-energy transition.
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Pu
authors.initials: P
authors.lastname: Huang
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Shi
authors.affiliation: College of Physics and Electronic Information, Inner Mongolia Normal University , Hohhot 010022, People's Republic of China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Xin-He
authors.initials: XH
authors.lastname: Jiang
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Zhong
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Ding
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Cao
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Meng
authors.initials: M
authors.lastname: Wu
authors.affiliation: State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University , Beijing 100871, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lu