Transforming C60 molecules into Graphene Quantum Dots

Transforming C60 molecules into Graphene Quantum Dots
Kian Ping Loh and Jiong Lu
Department of Chemistry, National University of Singapore
Graphene is a one-layer thick sheet of carbon atoms arranged in a honeycomb structure.
Unlike the stacked carbon sheets in graphite, the isolated sheet is decoupled from other
carbon sheets. This stand-alone nature of graphene coupled with the special symmetry of
its honeycomb structure creates very fascinating and unique electronic properties in this
material. Due to the fact that graphene is a single atomic sheet with no bulk, when it is
used as active material in devices, it represents the ultimate limit in terms of the vertical
downsizing.
A major hindrance for graphene to be fully utilized for next-generation nanoelectronics is its
lack of an energy gap. The presence of an energy gap is essential for a transistor to
achieve a good on-off ratio in switching. One way to engineer a band gap in graphene is to
geometrically confine the size of graphene. For example, using lithographical techniques,
graphene can be patterned into very narrow ribbons or very small dots. In these cases,
owing to quantum confinement and edge effects, a band gap can be opened up in the
material. However, structures with lateral dimension smaller than 10 nm are usually needed
to achieve quantum confinement, and to fabricate such small structures is highly
challenging using conventional top-down lithographical approaches.
The team of KP LOH and Jiong Lu [1] considered a bottom-up assembly approach using
C 60 molecules as the precursor for the generation of graphene. The idea is simple: every
fullerene molecule has the same size and shape, so the fragmentation of fullerene, if
carried out under well-controlled conditions, should produce uniformly-sized graphene
quantum dots. They show that when C 60 molecules are adsorbed on Ruthenium (Ru) crystal

at low coverage, the Ru-catalyzed cage-opening of fullerene provides a controllable route to
the templated synthesis of graphene quantum dots. Using Scanning Tunneling Microscopy,
the team found that the fragmentation of the C 60 molecules at elevated temperatures
produces highly symmetrical carbon cluster that undergo diffusion and aggregation to form
geometrically well defined quantum dots. These results provide valuable insights into the
diffusion and thermal dynamics of carbon clusters on metal surfaces.
Reference
[1] Transforming C-60 molecules into graphene quantum dots
Lu J (Lu, Jiong) 1 , Yeo PSE (Yeo, Pei Shan Emmeline) 1,2 , Gan CK (Gan, Chee Kwan) 2 , Wu P
(Wu, Ping) 2 , Loh KP *(Loh, Kian Ping) 1
Source: Nature Nanotechnology, 6, 247–252, (2011), doi:10.1038/nnano.2011.30
The work has been highlighted in http://nanotechweb.org/cws/article/tech/45526.
[2] Graphene oxide as a chemically tunable platform for optical applications
Loh KP*, Bao QL, Eda G, et al.
NATURE CHEMISTRY Volume: 2 Issue: 12 Pages: 1015-1024 Published: DEC 2010
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