KYUNG HEE UNIVERSITY

Breakthrough research of graphene quantum dots clarifies size dependences of luminescence and structural formation.

Professor Suk-Ho Choi of the Department of Applied Physics at Kyung Hee University’s Global Campus published his research findings in the August 12th internet edition of the journal, ACS Nano, which is published by the American Society of Chemistry. Choi’s paper, “Anomlous behaviors of visible luminescence from graphene quantum dots: interplay between size and shape,” is the first ever to discover size-dependent changes in the shape and the edge state of graphene quantum dots and the dependence of the luminescence on these changes.
 

Turning point in the utilization of graphene quantum dots for LEDs, solar cells, memories, and photodetectors
Since its discovery in 2004, graphene, a 0.34-nm-thick, two-dimensional honeycomb (hexagon-shaped) network of carbon atoms, has received wide attention as a new future nanomaterial. Since graphene is transparent, chemically stable, and highly conductive, it can be used in a wide range of products such as flexible displays and solar cells.

In his research, Choi fabricated various-size graphene quantum dots by chemical exfoliation and cutting of graphene oxide sheets, and proved that the shape and the edge state of graphene quantum dots strongly depend on their size. It is widely believed that when quantum dots increase in size, light energy decreases (quantum confinement effect). However, Choi proved through photoluminescence analyses that light energy decreases as the size increases when quantum dots retain their circular shape, but when their shape varies into polygons, light energy increases with size.

“Because the research on graphene quantum dots has been conducted for just one to two years, very little has been revealed,” says Choi. “As such, I take pride in this research which clarified the size dependences of their structural and light-emitting properties..

Choi has published 140 papers in SCI journals including the world’s first discovery of the light amplification of graphene in the September 15, 2010 internet edition of the American Institute of Physics’ Physical Review Letters, the world’s leading journal in physics. Last year, he received the Korean Physical Society Award for Outstanding Accomplishments in Physics Research at its 87th meeting in 2011. In recognition of these contributions, Choi was named a Kyung Hee Fellow for a second term this year following his selection in 2009.

Professor Choi has been studying electronic and optical devices by using semiconductor and metal nanostructures and is currently interested in hybrid structures of semiconductors and graphene. Choi revealed future plans to conduct research on graphene and graphene-related materials applicable to nano-optoelectronic devices such as memories, LEDs, solar cells, and photodetectors.