title: Anomalous behaviors of visible luminescence from graphene quantum dots: interplay between size and shape.
abstract: For the application of graphene quantum dots (GQDs) to optoelectronic nanodevices, it is of critical importance to understand the mechanisms which result in novel phenomena of their light absorption/emission. Here, we present size-dependent shape/edge-state variations of GQDs and visible photoluminescence (PL) showing anomalous size dependences. With varying the average size (d(a)) of GQDs from 5 to 35 nm, the peak energy of the absorption spectra monotonically decreases, while that of the visible PL spectra unusually shows nonmonotonic behaviors having a minimum at d(a) = ~17 nm. The PL behaviors can be attributed to the novel feature of GQDs, that is, the circular-to-polygonal-shape and corresponding edge-state variations of GQDs at d(a) = ~17 nm as the GQD size increases, as demonstrated by high-resolution transmission electron microscopy.
authors.affiliation: Department of Applied Physics, Kyung Hee University, Yongin 446-701, Korea.
authors.forename: Sung
authors.initials: S
authors.lastname: Kim
authors.forename: Sung Won
authors.initials: SW
authors.lastname: Hwang
authors.forename: Min-Kook
authors.initials: MK
authors.lastname: Kim
authors.forename: Dong Yeol
authors.initials: DY
authors.lastname: Shin
authors.forename: Dong Hee
authors.initials: DH
authors.lastname: Shin
authors.forename: Chang Oh
authors.initials: CO
authors.lastname: Kim
authors.forename: Seung Bum
authors.initials: SB
authors.lastname: Yang
authors.forename: Jae Hee
authors.initials: JH
authors.lastname: Park
authors.forename: Euyheon
authors.initials: E
authors.lastname: Hwang
authors.forename: Suk-Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Geunwoo
authors.initials: G
authors.lastname: Ko
authors.forename: Sunghyun
authors.initials: S
authors.lastname: Sim
authors.forename: Cheolsoo
authors.initials: C
authors.lastname: Sone
authors.forename: Hyoung Joon
authors.initials: HJ
authors.lastname: Choi
authors.forename: Sukang
authors.initials: S
authors.lastname: Bae
authors.forename: Byung Hee
authors.initials: BH
authors.lastname: Hong
mesh_terms: D016477:Artifacts; D006108:Graphite / Q000737:chemistry*; D008027:Light; D008163:Luminescent Measurements / Q000379:methods*; D010316:Particle Size; D045663:Quantum Dots; D012542:Scattering, Radiation
chemical_list: D006108:Graphite