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Published online: 6 May 2009 | doi:10.1038/nchina.2009.92

Material chemistry: Cutting edge

Felix Cheung

Introduction

© (2009) Wiley Interscience

Graphene — a single layer of carbon atoms — has been the subject of intense research since its discovery. To tailor graphene to different needs, it can be cut into different shapes and sizes by physical means, such as heat and sonic treatment, or chemical means, such as oxidation. Zhenyu Li, Jinlong Yang and co-workers at the University of Science and Technology of China in Hefei¹ suggest that oxidation might produce graphene pieces with more smooth edges than heat or sonic treatment.

During oxidation, oxygen atoms attack the carbon–carbon bonds on the graphene sheet to form epoxy groups (top image; epoxy groups are marked in red) along a line. Calculations show that the 'line of defects' induces a distortion in the graphene structure, which makes epoxy groups prone to further oxidation into epoxy pairs (middle image).

It is difficult to break these epoxy pairs on a pristine graphene sheet, however. They require something else to activate their breakup.

The researchers modelled what would happen at the graphene edge during oxidation. Their calculations showed that some of the dangling bonds along the edge oxidize into carbonyl pairs. The carbonyl pairs make adjacent epoxy defects prone to further oxidation (bottom image). As a result, the graphene sheet tears apart from the edge.

The findings suggest that the presence of epoxy defects is critical to graphene breakup, and a well-controlled oxidation could break graphene down into smaller pieces with smooth edges.

The authors of this work are from:
Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, China; Department of Theoretical Chemistry, School of Biotechnology, Royal Institute of Technology, Stockholm, Sweden.

Reference

1. Li, Z., Zhang, W., Luo, Y., Yang, J. & Hou, J. G. How graphene is cut upon oxidation? J. Am. Chem. Soc. doi:10.1021/ja8094729 (2009). | Article |