Anomalous Light Emission and Wide Photoluminescence Spectra in Graphene Quantum Dot: Quantum Confinement from Edge Microstructure

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• 作者：Pu Huang ; Jun-jie Shi ; Min Zhang ; Xin-he Jiang ; Hong-xia Zhong ; Yi-min Ding ; Xiong Cao ; Meng Wu ; Jing Lu
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：August 4, 2016
• 年：2016
• 卷：7
• 期：15
• 页码：2888-2892
• 全文大小：408K
• 年卷期：0
• ISSN：1948-7185

文摘

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.