New form of carbon found: diamondiyne

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Scientists have created a new form of carbon called diamondiyne. It is a three-dimensional network of carbon atoms that resembles a diamond but with a more open structure.

Researchers first proposed the existence of this form more than three decades ago and it has finally been synthesised. The findings were reported in the journal Angewandte Chemie.

Carbon atoms can bond together to form crystals of different shapes, called allotropes. The three most famous ones are graphite, diamond, and graphene. While in diamond each carbon atom bonds to four neighbours, in the graphene the atoms form a flat sheet. Diamondiyne is more akin to diamond but it more closely resembles two open jungle gyms — the grid of cages you see in parks where children can climb and swing from — pushed through each other, with more spacious cages, with more room within the structure than diamonds.

Scientists took so long to create this allotrope because one of its chemical building blocks is unstable and because if the bonds do not connect properly in the process of making it, they can be difficult to undo.

The researchers who succeeded, from the University of Gothenburg, Stock University, and the Chalmers University of Technology, all in Sweden, did so by making the material at a boundary between water and chloroform, with the chemical reaction slowly releasing the building blocks and allowing them to link up at a rate the team could control. (The ‘y’ in the material’s name comes from the presence of carbon-carbon triple bonds.)

The process — which could take around a week — produced thin films of carbon covering around five square centimetres each. The researchers could control their thickness by slowing down or speeding up the reaction, from a few nanometres to up to 60 nanometres.

The team used spectroscopy and electron microscopy to confirm the films contained small diamondiyne crystals. However, it was present only to the tune of 1% of the reaction yield.

So much trouble, and for what?

Scientists often pursue research like this in order to discover what forms matter can take and how the ways in which their atoms are arranged control their properties as a material.

Carbon in particular poses an interesting case because while diamond is extremely hard and an electrical insulator, graphite is soft and conducts electricity, yet both are allotropes of the same element. By extension, synthesising the new allotrope has reinforced the notion that scientists can potentially create materials with radically different properties but without changing their chemical composition.

And some discoveries could eventually lead to a material that might be useful in electronics, storing energy or some other technology that the world is looking for.

The cage-like structure of diamondiyne also offers the additional prospect of containing other atoms within. Synthesising diamondiyne confirms to scientists that the prediction more than 30 years ago was correct, which in turn validates the process scientists used to make that prediction.

Finally, the technique by which the team synthesised the material could help researchers make other previously inaccessible materials with useful properties.

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