Optical
microscope image of stacked graphene layers. Credit: Dr Matt Large
Graphene
and nanomaterials have been touted as wonder materials, and they are proving
invaluable in all sorts of applications, such as in the automotive and
aerospace industries, where heavy metals are replaced with lighter but equally
strong composite materials. Nanomaterial quality therefore matters a great
deal, but standardization and quality checking have eluded the industry.
The Sussex
team have developed a technique that gives detailed information about the size
and thickness of graphene particles. It uses a non-destructive, laser-based
method for looking at the particles as a whole, and lets them quickly build a
detailed picture of the distribution of particles in a given material. Their
paper, "Raman Metrics for Molybdenum Disulfide and Graphene Enable
Statistical Mapping of Nanosheet Populations," is published in the journal
Chemistry of Materials.
Dr. Matt
Large, who led the discovery in the School of Mathematical and Physical
Sciences at the University of Sussex, said:
"Standards
for measurement are a really critical underpinning of modern economies. It
really comes down to one simple question; how do you know you got what you paid
for? At the moment the graphene industry is a bit of a wild frontier; it's very
difficult to compare different products because there is no agreed way of
measuring them. That's where studies like ours come in. It's really an
important issue for any business looking to reap the benefits of graphene (or
any other nanomaterial, for that matter) in their products. Often using the
wrong material can either have no benefit at all, or even make product
performance worse. A particular example would be composite materials like
graphene-reinforced plastics; if a poor-quality graphene material is used it
can cause parts to fail instead of providing the improved strength expected.
This can be a big issue for industries such as automotive and aerospace, where
there is enormous effort behind replacing heavier metal parts with lighter
composite materials (like carbon fiber) that are just as strong. If graphene
and other nanomaterials are to play a role in reducing weight and cost then
agreed standards are really important."
Aline
Amorim Graf is a co-author of the paper in the team at the School of
Mathematical and Physical Sciences at the University of Sussex. She said:
"Some
manufacturers say they produce graphene but actually—no doubt
inadvertently—produce a form of graphite. Some will charge up to £500 per gram.
The trouble is there's no standardization. What we've done is to create a new
way to measure the quality of nanomaterials like graphene. We use a Raman
spectrometer to do this, and have created an algorithm to automate the process.
In this way, we can determine the quality, size and thickness of the sample.
Clearly the quality of graphene really matters. If you're using graphene to
strengthen structures, to use in health monitors, to use in supermarket tags,
you want to know you're getting the real stuff. But actually purchasers of
graphene have no clue as to the quality of what they're buying online. If
you're using graphene to strengthen cement, and it turns out it's actually not
graphene or is low quality graphene, then that's going to matter."
Professor
Alan Dalton, co-Director of the Sussex Program for Quantum Research and
co-author of the paper, said:
"This
is truly an important area of research for our team. We believe that our new
metric will be of great help to industry, researchers and standards bodies
alike who are key-stakeholders in the development of 2-D materials towards
commercialisation."
The
Graphene Council has long called for better standardization. Terrance Barkan of
the Graphene Council has written:
"The lack of an agreed global standard for graphene and closely related materials creates a vacuum and lack of trust in the marketplace for industrial scale adoption of graphene materials."