Graphyne goes from theory to practice


The crystal structure of a layer of graphyne. Image: Yiming Hu.

For over a decade, scientists have attempted to synthesize a new form of carbon called graphyne, with limited success. That endeavor is now at an end, though, thanks to new research from the University of Colorado Boulder (CU Boulder).

Graphyne has long been of interest to scientists because of its similarities to the ‘wonder material’ graphene – another form of carbon that is highly valued by industry and whose discovery was even awarded the Nobel Prize in Physics in 2010. However, despite decades of work and theorizing, only a few fragments of graphyne have ever been created before now.

This latest research, reported in a paper in Nature Synthesis, fills a longstanding gap in carbon material science, potentially opening brand-new possibilities for electronics, optics and semiconducting material research.

“The whole audience, the whole field, is really excited that this long-standing problem, or this imaginary material, is finally getting realized,” said Yiming Hu, lead author of the paper and a doctoral graduate in chemistry at CU Boulder.

Scientists have long been interested in the construction of novel carbon allotropes, or forms of carbon, because of carbon’s usefulness to industry, as well as its versatility.

There are various different ways carbon allotropes can be constructed, depending on how sp2, sp3 and sp-hybridized carbon (reflecting the different ways carbon atoms can bind to other elements), and their corresponding bonds, are utilized. The most well-known carbon allotropes are graphite (used in pencils and batteries) and diamonds, which are created out of sp2 carbon and sp3 carbon, respectively.

Using traditional chemistry methods, scientists have successfully created various other allotropes over the years, including fullerene (the discovery of which won the Nobel Prize in Chemistry in 1996) and graphene.

However, these traditional methods don’t allow for different types of carbon to be synthesized together in any sort of large capacity, as is required for graphyne. This has left the theorized material – speculated to have unique electron conducting, mechanical and optical properties – to remain just that: a theory.

But it was exactly that need for non-traditional approaches that led those in the field to reach out to Wei Zhang’s group. Zhang, a professor of chemistry at CU Boulder, studies reversible chemistry, which is chemistry that allows bonds to self-correct, allowing for the creation of novel ordered structures, or lattices, such as synthetic DNA-like polymers.

After being approached, Zhang and his lab group decided to give it a try. Creating graphyne is a “really old, long-standing question, but since the synthetic tools were limited, the interest went down,” said Hu, who was a PhD student in Zhang’s group. “We brought out the problem again and used a new tool to solve an old problem that is really important.”

Using a process called alkyne metathesis – which is an organic reaction that entails the redistribution, or cutting and reforming, of alkyne chemical bonds (a type of hydrocarbon with at least one carbon-carbon triple covalent bond)—as well as thermodynamics and kinetic control, the group was able to successfully create what had never been created before. A material that could rival the conductivity of graphene but with control.

“There’s a pretty big difference (between graphene and graphyne) but in a good way,” said Zhang. “This could be the next-generation wonder material. That’s why people are very excited.”

While the material has now been successfully created, the team still wants to look into the particular details of it, including how to create the material on a large scale and how it can be manipulated. “We are really trying to explore this novel material from multiple dimensions, both experimentally and theoretically, from atomic-level to real devices,” Zhang said.

These efforts, in turn, should aid in figuring out how the material’s electron-conducting and optical properties can be used for industry applications like lithium-ion batteries. “We hope in the future we can lower the costs and simplify the reaction procedure, and then, hopefully, people can really benefit from our research,” said Hu.

For Zhang, this could never have been accomplished without the support of an interdisciplinary team: “Without the support from the physics department, without some support from colleagues, this work probably couldn’t be done.”

This story is adapted from material from the University of Colorado Boulder, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.



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