Excitonic Photoluminescence from Nanodisc States in Graphene Oxides.
The origin of near-infrared (NIR) luminescence from graphene oxide (GO) is investigated by photoluminescence (PL) excitation spectroscopy, time-resolved PL spectroscopy, and density functional theory based many body perturbation theories. The energy of experimentally observed NIR PL peak depends on the excitation energy, and the peak broadens with increasing excitation energy. It is found that the PL decay curves in time-resolved spectroscopy show build-up behavior at lower emission energies due to energy transfer between smaller to larger graphene nanodisc (GND) states embedded in GO. We demonstrate that the NIR PL originates from ensemble emission of GND states with a few nanometers in size. The theoretical calculations reveal the electronic and excitonic properties of individual GND states with various sizes, which accounts for the inhomogeneously broadened NIR PL. We further demonstrate that the electronic properties are highly sensitive to the protonation and deprotonation processes of GND states using both the experimental and theoretical approaches.
†Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.
Daichi
D
Kozawa
‡School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.
Xi
X
Zhu
†Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.|§Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
Yuhei
Y
Miyauchi
†Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.
Shinichiro
S
Mouri
∥Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashi-Nada-ku, Kobe 658-8501, Japan.
Masao
M
Ichida
‡School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|⊥Institute of Advanced Studies, Nanyang Technological University, 60 Nanyang View, 639673 Singapore.
Haibin
H
Su
†Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan.
Kazunari
K
Matsuda
functional groups; graphene oxides; graphene quantum dots; many-body perturbation theory; near-infrared; photoluminescence; ultrafast dynamics