Graphene has a great deal of potential applications, including its use in energy storage, building materials and medical devices. According to the National University of Singapore, however, most commercially-produced graphene is of a poor quality – it's a problem that could be holding the technology back.
Not only is graphene the world's strongest manmade material, but it's also chemically inert and highly conductive, both thermally and electrically. It takes the form of one-atom-thick sheets of linked carbon atoms, and is typically sold as a powder. That powder consists of minuscule graphene flakes, which are exfoliated off of pieces of graphite.
Or at least, that's what it's supposed to consist of.
A team of NUS researchers analyzed a wide variety of those powders, obtained from 60 different suppliers in the Americas, Asia and Europe. To do so, they used a combination of electron microscopy, atomic force microscopy, Raman spectroscopy, elemental analysis, X-ray photoelectron spectrometry, plus both scanning and transmission electron microscopy.
The scientists determined that the majority of the powder samples contained less than 10 percent graphene flakes, with only one sample containing more than 40 percent. The rest of the material in those samples consisted mainly of relatively thick graphite microplatelets – these were likely the result of an improper exfoliation technique, and they do not have the same characteristics as actual graphene flakes.
This means that if the powders were utilized for research into possible uses for graphene, the results would be skewed not only by the low graphene content, but also by variations in the amount of graphene present in different powders used by different research institutes. Complicating things further, some samples additionally contained chemicals that were used in the production process.
While it's hard to say if the suppliers actually knew of the claimed shortcomings of their products, it is hoped that the team's findings will lead to a universal testing procedure which will ensure that all future commercially-produced graphene meets a standard, sufficient quality.
"This is the first ever study to analyze statistically the world production of graphene flakes," says lead scientist Prof. Antonio Castro Neto. "Considering the important challenges related to health, climate, and sustainability that graphene may be able to solve, it is crucial that research is not hindered in this way."
A paper on the research was recently published in the journal Advanced Materials.
Source: National University of Singapore