Leaky graphene oxide with high quantum yield and dual-wavelength photoluminescence

Leaky graphene oxide (LGO) was gram-scale prepared by oxidation of graphite oxide using mixed acid. The LGO showed a dual-wavelength photoluminescence (PL) with the absolute quantum yield of 11.6%. Three routes including hydrothermal method, hydrazine-assisted hydrothermal method, and hydrazine reflux were used to reduce the LGO. The contents of oxygen- and nitrogen-bearing functional groups varied depending on the reduction methods. The reduced LGOs showed a blue-shifted dual-wavelength PL and strong decrease of the quantum yields. To understand the contribution of different kind of functional groups to the PL, we used density functional theory calculation of the ground states of graphene fragments modified by various functional groups according to our experimental results. The energy gaps broadened with the removal of functional groups, indicating the blue-shift of the PL after reduction. We proposed that the blue-green PL of the LGO arose from small aromatic domains by quantum size effect. Functional groups surrounded the aromatic domains induced the red shift of the PL. The high quantum yield may ascribe to the defective and holey structure of the LGO. Our work provided a simple method to prepare high performance graphene based PL materials, and could help for understanding the nature of dual-wavelength PL.