By using a simple, inexpensive and quick process, researchers from the University of Madras have been able to produce a monolayer or a few layers thick graphene nanosheets from graphite material without using any strong oxidising or reducing agents. The results were published in the journal Materials Letters .
Among several techniques adopted to synthesise graphene from graphite, the liquid phase exfoliation methods have been found to be facile and cost-effective.
Yet, the use of strong solvents and relatively low yield have turned out to be major drawbacks, limiting its utilisation in the large-scale production of graphene.
“Commercialisation of high-quality graphene sheets calls for the exploration of a simple, effective, and inexpensive method for its engineering and environmental applications,” says Dr. S. Balakumar, Director of the National Centre for Nanosciences and Nanotechnology, University of Madras.
Dr. S. Balakumar and one of his students, M. Balasubramaniam, used ultrasound along with water, glacial acetic acid (CH3COOH), which is a mild solvent, and ethanol (C2H6O) to exfoliate graphite into graphene sheets.
Additional energyWhile electrostatic bonds between the cleavage planes do not allow the acid to get in, supplying additional mechanical energy in the form ultrasonic waves enables the organic acid to penetrate deeper into the graphitic flakes and exfoliate the individual layers of graphene.
“Probe sonication is an effective method for the exfoliation of molybdenum sulphide, another material similar to graphite. It is likely that in presence of molecules like acetic acid, exfoliation of graphite is effective,” acoording to Prof. T. Pradeep from the Department of Chemistry, IIT Madras, who wasn't involved in the research.
