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"Superheated" water new way to etch diamonds

07 May 2013

Ms Lim is the first author of the paper published in Nature Communications

Photo: Lianhe Zaobao © Singapore Press Holdings

Diamond is known to be the hardest natural substance, owing to its strong covalent bonds between atoms. It can only be cut with another diamond, special tools coated with diamond powder or laser.

Now, however, research led by Professor Loh Kian Ping, Head of the NUS Department of Chemistry, has found another way to etch diamonds - "superheated" water. The work was recently published on Nature Communications, an online multidisciplinary journal for high-quality research on the biological, physical and chemical sciences.

First author Ms Candy Lim Yi Xuan, a PhD candidate from the NUS Graduate School for Integrative Sciences and Engineering, made the exciting discovery when experimenting on the conductivity of graphene. While attempting to put a thin sheet of graphene on diamond using heated water, she observed unexpected corrosion on the diamond.

Upon further investigation, the NUS team - in collaboration with analytical instrumentation company Bruker Singapore and Hasselt University Wetenschapspark in Belgium - found that at high temperatures, there was a restructuring of the interface and chemical bonding between graphene and diamond. The water molecules trapped change into a distinct supercritical phase at a temperature above 400 degree Celsius. The "superheated" water exhibits different behaviours from normal water.

"We show for the first time that graphene can trap water on diamond, and the system behaves like a 'pressure cooker' when heated. Even more surprising, we found that such superheated water can corrode diamond. This has never been reported," pointed out Prof Loh.

The applications are "immense", he said. "In the industry, supercritical water can be used for the degradation of organic waste in an environmentally friendly manner. Our work is also applicable to the laser-assisted etching of semiconductor or dielectric films, where the graphene membrane can be used to trap liquids," said the graphene expert.

Next, the team plans to study the supercritical behaviours of other fluids at elevated temperatures. This could spell more industrial applications.