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MASS-PRODUCING GRAPHENE


BY LES JOHNSON, JOSEPH E. MEANY

It may be easy to isolate little flakes of this one-atom-thick carbon material,
but it’s surprisingly difficult to produce large sheets for commercial use.

ENGINEERING TECHNOLOGY

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THIS ARTICLE FROM ISSUE

MAY-JUNE 2018

VOLUME 106, NUMBER 3

PAGE 176

DOI: 10.1511/2018.106.3.176

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What if you discovered an infinitesimally thin material capable of conducting
electricity, able to suspend millions of times its own weight, and yet porous
enough to filter the murkiest water? And what if this substance was created from
the same element as that filling the common pencil?

A growing cadre of scientists aims to make this extraordinary material,
graphene, a mainstay technological material by the second half of the 21st
century. Not satisfied with that timeline, some entrepreneurial types would like
to see widespread adoption of graphene within the next decade.

Graphene is elegant. It is created from a single element, carbon, formed by just
one type of bond. Despite graphene’s apparent simplicity, isolating the material
was elusive for chemists and physicists alike. Graphene excels at hiding in
plain sight, and the techniques and instrumentation perfected in the last two
decades have played a pivotal role in its discovery.

Graphene, shown here in crumpled form in a scanning electron micrograph, is as
remarkable for its versatility as for its strength. This material is made up of
carbon atoms bonded together to form a sheet just one atom thick. The honeycomb
arrangement of the atoms allows graphene to be very flexible as well as porous
and lightweight. An excellent conductor of electrons, graphene has attracted
great interest for its potential applications in miniature electronics and
various types of sensors; its transparency may also make it suitable for use in
solar panels and window coatings. But better production methods are needed to
recognize its potential.

André Geim & Kostya Novoselov/Science Source



Carbon, the sole constituent of graphene, is all around us. The element is the
fourth most common in the entire universe. Most people think of materials in
terms of atoms and molecules, where molecules are made from defined types and
numbers of atoms. With graphene, counting carbon atoms is inconsequential.
Merely the way in which the constituent carbons are bound to one another is
crucial, with this feature separating graphene from other wholly carbon
materials such as diamonds and graphite. At the atomic level, the exclusively
carbon graphene resembles a hexagonal “chicken wire” fence, with each carbon
atom making up the point of a hexagon. The hexagonal distribution makes
graphene’s properties possible, because the distribution allows the individual
carbon atoms of graphene to lie flat.

This property of graphene cannot be overlooked. Graphene is a perfect anomaly in
the world of chemistry—a flat, two-dimensional molecule, with a single sheet of
graphene measuring only one atom thick. You might immediately question the
structural integrity of graphene because of its delightfully simplistic
construction, but the weaving of the carbon hexagons throughout the structure
makes the atomically thin material unexpectedly strong.

You have experienced synthesizing graphene, maybe even earlier today, on a very
small scale. The pressure exerted by your hand and fingertips likely created a
few layers of graphene the last time you ran a pencil across a notepad, turning
humble graphite into graphene as you wrote this week’s grocery list.


SCALING UP

After two researchers in Great Britain, Konstantin Novoselov and Andre Geim,
were awarded the Nobel Prize in Physics in 2010, technology magazines everywhere
heralded a new era of “wonder materials” based around this atomically thin
tessellation of carbon atoms. With its incredibly high strength and almost
impossibly low electrical resistance, graphene pulled back a hidden curtain,
allowing scientists to catch a glimpse of the marvels that lay beyond.

Early investors were burned, however, by entrepreneurs who over-promised and
underdelivered on performance aspects for products (especially composites such
as plastics) that had graphene in them but that did not use graphene in a way
that made its incorporation worth the added expense. It was, in some cases, just
an added bit of snake oil. As the overall volume from new production methods and
the quality of the resulting graphene have both increased over time, we are
starting to finally see graphene’s true benefits.

Flakes of graphite (seen here in a scanning electron micrograph, left), may
measure only 10 nanometers in thickness and yet contain multiple layers of
graphene. For their discovery of this previously unknown material in 2004, Andre
Geim (right) and Konstantin Novoselov were awarded the Nobel Prize in Physics
six years later.

André Geim/Science Source; James King-Holmes/Alamy

If graphene is made from carbon and scientists have known how to isolate the
material for more than a decade, why are there so few graphene products on the
market?

The roadmap from a fundamental research laboratory to store shelf is never a
direct path, although the time that passes between discovery and commercial
application is shrinking rapidly.

The graphene flakes on silicon wafers are really just the first droplets in the
bottom of a beaker when compared to the revolution that will occur once someone
solves the riddle of how to make large-area pristine graphene sheets.

For the last decade or so, Additive Manufacturing (AM) has been all the rage.
You might know AM by its more common name, 3D printing. Many early generation AM
devices used only plastic, to make interesting 3D renditions of various objects,
but the technology has grown significantly more capable.

Additively manufactured structural materials are an obvious place to begin
adding graphene flakes. Researchers at the Massachusetts Institute of
Technology, using a custom AM machine, printed various 3D objects from graphene
and tested them to measure their physical properties compared with more
conventionally produced parts. The results were astonishing. Some of the
3D-printed samples had 10 times the strength of steel at 1/20th the mass. They
can now print parts and assemblies that may, in some cases, replace
custom-manufactured steel parts for increased mechanical strength.



3D printing is another technology that can benefit from the thinness and
lightness of graphene. In comparative studies, 3D objects printed in graphene
were found to be 10 times as strong as their counterparts that had been printed
in steel, while having 5 percent of the steel objects’ mass. A type of graphene,
shown here, is tailored for building self-supporting 3D structures.

John Wiley and Sons; From García-Tuñon et al., Advanced Materials 27(10), 21
Jan. 2015

For graphene to make all the revolutionary changes that are predicted (and, in
some cases, actually tested), there must be an automated manufacturing process
to produce kilograms of graphene per day or tons of the material per year—not
just a few grams here and there. Graphite is basically graphene layered upon
itself, waiting for someone to separate it out. This is where it gets tricky,
however.

First of all, we should probably rule out mass production of graphene using the
method by which it was originally isolated. While it is amusing to imagine a
cavernous room filled with people using adhesive tape to separate graphene
sheets from piles of pencil lead, it is simply not practical. Perhaps someone
can figure out how to automate this particular process, but, even then, it
doesn’t appear likely to scale well to the mass production needed. In other
words, don’t invest your retirement savings in adhesive tape futures!

Researchers at Rutgers University are making sheets of graphene out of ordinary
graphite flakes and some sulfuric or nitric acid. The addition of the acid
oxidizes the graphene sheets that make up the graphite, and forcing oxygen atoms
between the sheets of graphene causes them to split apart, forming graphene
oxide sheets suspended in acid and water. Next, the liquid is filtered out,
leaving flakes of graphene oxide to clog up the filter. The sum of all the clogs
across the filter eventually makes up a paperlike sheet of graphene oxide. This
paperlike sheet can then be removed from the filter by dissolving the filter
away using a solvent that doesn’t react with graphene oxide. The last step is to
remove the oxygen, which is done by using hydrazine, leaving only a pure
graphene coating.

This resulting material is called reduced graphene oxide, or RGO for short. In
this instance, “reduced” refers to a chemical use of the word, where the
oxidation state of each graphene carbon has been decreased through the removal
of the oxygen by hydrazine. In this case, hydrazine is a reducing agent, which
is oxidized by its reaction with the graphene oxide.

For all its high-tech capacities, graphene is surprisingly easy to make at
home—in very small quantities. The only raw materials needed are graphite (for
instance, the broken-off point of a standard Number 2 pencil) and some fairly
robust adhesive tape. Sticking the tape onto the surface of the graphite and
pulling sharply will peel off a flake of carbon, and successive rounds of
flaking will reduce the thickness of the flake until it is down to a single-atom
layer.

Ozyilmaz Group/Physics Department/National University of Singapore

Methane, a carbon-rich gaseous compound with which we humans are very familiar,
can be reacted with copper at high temperatures to produce graphene. Simply heat
the copper to about 1,000 degrees Celsius and expose it to the methane gas.
Layers of graphene will form on the copper’s surface from the plentiful carbon
atoms in the methane gas, a process called chemical vapor deposition (CVD).
There are two big problems with this method: It takes a long time to make even a
little graphene, and the quality of the graphene produced is not very good.

David Boyd at the California Institute of Technology, along with his research
collaborators, has found a way to improve on the CVD approach so that it will
work with lower temperatures and produce a higher quality graphene. They, too,
use copper and methane, but they add a bit of nitrogen to improve the layering
of the graphene on the copper. In this method, energy still needs to be added,
but not nearly as much. The reaction goes forward at a “mere” 420 degrees.
Global industry has considerable experience with CVD, so it should be possible
to eventually automate the process on a large scale; the goal is to produce
centimeters or even meters of high-quality graphene at a time.

> For the remarkable wonders of graphene to be realized, it must be produced in 
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Are dangerous chemicals, complex machines, and multistep chemical reactions and
processes too complex for your tastes? Then consider this approach, discovered
at Kansas State University, where they produced graphene by creating an
explosion. Have you ever built a spud gun? Basically, if you take a one- to
two-meter-long PVC pipe, create a combustion chamber at one end using a spark
plug and a quick-sealing endcap, stuff a potato in the other end, and fill the
now sealed combustion chamber with a flammable vapor (hair spray is good), then
you have a spud gun. Once the potato is in place, the chamber fueled with hair
spray and then sealed, you can point the far end of the PVC pipe toward your
target and discharge your battery to cause the spark plug to spark. The
resulting small explosion creates a pressure wave that dislodges the potato from
the end of the combustion chamber, moving it up the nozzle of the PVC pipe, and
into the air—often launching it tens of meters into the distance. The physics of
what happens in the combustion chamber is very similar to the method that
scientists at Kansas State University used to create graphene, in what may
become a scalable process that could be a step toward mass production.

Interestingly enough, graphene wasn’t what the scientists were trying to make.
Instead, they were trying to make something called a carbon soot aerosol gel for
use in insulation and water purification systems. These gels were suddenly
forgotten when they realized that their soot wasn’t what they were looking for,
but graphene. And not just a little bit of graphene. They claim that their
process is the least expensive so far for potentially mass-producing graphene,
and that it doesn’t require much input energy. Granted, nothing is ever that
simple, but this approach sounds like a good one to pursue in conjunction with
other methods.

Instead of PVC pipe, the scientists used a more robust chamber for their
combustion event. They replaced the hair spray with acetylene or ethylene gas
mixed with oxygen. They did use a spark plug to create the combustion, just as
we did with our spud gun. The fuel, the acetylene or ethylene gas, was turned
into graphene and some other carbon detritus.

A relatively inexpensive technique for producing graphene from soybean oil was
developed by researchers at Australia’s Commonwealth Scientific and Industrial
Research Organization. This method calls for heating the oil to break it down
into its constituent carbon atoms, and then quickly cooling the carbon in thin
layers on nickel foil. Besides being less costly, the soybean-oil technique is
safer than methods that use vacuum processing or explosive compressed gas.

Dr. Samuel Yick/CSIRO

Then there is the soybean oil method—as in, the same stuff you can use at home
when you cook. A research team in Australia found a way to use everyday soybeans
to produce single-layer graphene sheets on top of a nickel substrate—potentially
making sheets with large areas all at one time. The process is a variation of
the CVD process described previously, but with a significant difference: This
one is done in ambient air (no specialized vacuum chambers, etc.) and the
required energy is not as great as is for other CVD processes.

The secret is in the nickel foil catalyst used and in carefully controlling the
temperature of the process to prevent, as much as possible, the formation of
carbon dioxide. Voilà: In goes soybean oil—out comes graphene. It is worth
mentioning that the team investigated other metal foils, including copper, and
no others promoted the formation of graphene. Only nickel did.

When all else fails, why not just go home and use your blender to make the
wonder material of the 21st century? That’s essentially what Jonathan Coleman of
Trinity College, Dublin, did when he and his team put some graphite in a
blender, added an over-the-counter dishwashing liquid, and hit the start button.
With only a little more processing required to separate the newly formed
graphene sheets, Coleman and his colleagues found that they could produce
several hundred grams per hour using a fairly modest set of mixing equipment in
a 10,000-liter vat. It isn’t yet clear, however, whether this method can provide
high-quality graphene.

A search of the scientific literature reveals a myriad of techniques that can
produce graphene of varying quality. What they have in common is complexity,
energy, and the fact that they can only achieve the production of small
quantities of graphene, which then needs to be separated out from the other
reaction products. To date, there is no simple production technique that results
in large quantities of high-quality graphene. For the truly remarkable wonders
of graphene to be realized, it must be produced in massive amounts—cheaply.


QUALITY CONTROL

Would you like to buy a 10 millimeter x 10 millimeter monolayer of graphene
flakes on a silicon substrate? $146. How about a 60 millimeter x 40 millimeter
piece of monolayer graphene on copper? $172. There are companies specializing in
graphene that will sell individual users samples at very reasonable prices. In
fact, for $124 and up they will sell you a small bit of graphene on your own
custom substrate.

Making graphene, though, is not trivial. The best mass-market graphene comes
from chemically exfoliated, natural, mined graphite, and companies that own
interests in graphite mines are already establishing themselves as players in
this graphene revolution, leveraging their preferential access to raw materials
in order to increase share prices.

But without agreement in the market or regulation, how would buyers determine
which so-called graphene product would be best for their needs?

The Center for Advanced 2D Materials (CA2DM) at the National University of
Singapore has established seven different tests by which it measures graphitic
materials to establish quality and identity. Unfortunately, only a few of these
tests are within the reach of a typical company laboratory; the others require
expensive equipment that needs to be run and maintained by specially trained
technicians.

The three cheapest tests to perform determine the size of a particular flake,
the degree of defects within a given sample, and the elemental makeup of a
sample. The size of a flake is determined by an optical microscope, whereas a
graphene/graphite sample on a backing surface is measured by a typical light
microscope. A camera and computer are able to measure the rough dimensions of a
graphene/graphite particle and report roughly how big the resulting flakes are.



Clusters of silicon atoms embedded in a graphene sheet appear as yellow shapes
in the center of this colored scanning transmission electron micrograph. The
hexagonal, latticelike arrangement of graphene atoms holds the silicon atoms in
place so they can be imaged.

ORNL/Science Source

Because graphene’s electronic properties are very sensitive to defects in the
flakes, the degree of these defects is an important parameter to measure. This
measurement is made with what is called Raman spectroscopy, which measures
vibrational patterns in the sample. Oxidation of the carbon-carbon bonds in
graphene by oxygen opens up graphene to environmental degradation, and the
introduction of other atoms onto the graphene surface causes various properties
to change dramatically. For example, adding even a single hydrogen atom to the
graphene structure causes the graphene to become magnetic.

The defect measurements would be supported by elemental analysis, particularly
the Carbon-Nitrogen-Hydrogen-Sulfur (CNHS) analysis. Mined graphite would
contain residues of the formerly living matter from which it was created, and
these elements would ultimately detract from the quality of the graphene through
one mechanism or another. Unfortunately, CNHS analysis is a destructive
technique. Part of the sample must be burned for the components to be analyzed.
Although this would be useful for batch-to-batch control of relatively cheap
industrially exfoliated graphite, it will not be acceptable for samples of
graphene produced by other methods.

There are many ways to determine the number of layers in a given graphite flake.
One such test, called atomic force microscopy (AFM), uses a hair-thin needle
mounted on a small springboardlike lever to measure the atomic forces between
the needle and a sample. A laser reflects off the top of the lever, which is
able to measure the amount of deflection, up or down, that the needle
experiences in its interaction with the surface. The readout gives the thickness
measured, and because graphite flakes stack at a constant distance from one
another, you can do the math to determine the number of layers. AFM is able to
create an image from many scans, because it adds successive one-dimensional
lines together to display a sample’s topography. In effect, it creates a height
map of a surface.

> It all might be made possible by the most abundant, most versatile, and most
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Scanning electron microscopy and transmission electron microscopy are methods of
looking at what a flake of graphene looks like, but on a much finer level than
optical microscopy is capable of. These two analyses have a much higher
magnification resolution and are therefore able to find rips, tears, and other
punctures in a flake; such punctures may be naturally existing or may have
formed during the graphene's isolation or handling. These two analyses combined
with AFM would give the most complete 3D picture of a graphene/graphite sample
overall.

The last major analysis performed by CA2DM is X-ray photoelectron spectroscopy
(XPS). XPS determines the chemical makeup of a sample nondestructively, and so
would give you all of the information that CNHS provides while still allowing
you to recover your sample. In this technique, X-rays are fired at the graphene
surface, and some of the X-rays are absorbed by electrons in the sample. The
electrons are ejected from the sample with an energy characteristic of the
element in the sample, which tells you what elements are present and in what
amounts.


MEANS OF GROWTH

Other than the Scotch tape method and chemical exfoliation, what could our
options be for making graphene in large amounts? Is there any way that we might
print or grow something into graphene? Mechanical exfoliation may be used to
peel hunks of graphite from the surface of a larger graphite hunk, with
successive peelings carried out to isolate a few monolayer sheets. This process
has been dramatically improved over the years, and indeed, special tapes are now
used, which can dissolve in water or other solvents more easily than can office
tape. That makes depositing graphene flakes even easier than before.

The second method, chemical exfoliation, has a history going back to the late
1800s. As with the mechanical exfoliation process, researchers have added to the
field by developing new exfoliation parameters. Generally they are less harsh on
the graphite and so minimize damage to the graphene surfaces. Perhaps the method
uses recyclable materials, which would be tremendously important for any company
that wants to produce literally tons of graphene per year. Some of the
improvements improve the yield of pristine monolayer flakes, which is the most
important optimization of all.

Graphene can also be grown from silicon carbide to produce what is called
epitaxial graphene.

Graphene layer growth from the decomposition of silicon carbide is now an
extremely complicated process, in which the silicon is sublimed at high
temperature but the atmosphere above the surface layer is variable. Tailoring
the environment above the surface allows researchers to produce graphene at
better efficiencies than with an open-air atmosphere. A 2009 Nature Materials
editorial by Peter Sutter described an advance in epitaxial growth that involved
removing air from above the silicon carbide surface and replacing it with an
inert noble gas atmosphere. Since then, research has turned back toward reactive
atmospheres.

Controlled confinement sublimation (CCS) is a way to produce graphene on a
silicon carbide substrate. If the silicon is not confined, the graphene grows in
a rapid and uncontrolled manner (A). Under confinement in a graphite enclosure,
sublimated silicon allows graphene to grow at near-thermodynamic equilibrium
(B); heat is supplied by an induction furnace (C). This method produces one to
ten layers of graphene on the silicon-terminated face and up to 100 layers on
the carbon-terminated face (D–F).

Jeff Fitlow/Rice University;Images from PNAS
(http://www.pnas.org/content/108/41/16900.)

In a twist, three groups from across Germany devised a method in which they
glued a plastic made from many aromatic benzene hexagons onto a silicon carbide
surface and found that this plastic actually drastically improved the size and
quality of graphene monolayers produced from the silicon sublimation. This work
was inspired by an earlier paper, which fused CVD with epitaxial growth to
improve the graphene yield. It seems that somehow the combination of these two
processes creates a product that is leagues better than either isolated method.
If time shows that this combination turns out to be repeatable and economical,
it could set the stage for graphene’s everyday importance to skyrocket. What’s
more, it could even force out natural, mined graphite from high-tech graphene
uses. That could spell disaster for graphite mining companies that are betting
their futures on selling to graphene consumers. This will be a development to
keep close tabs on.


RENEWABLE SOURCES

Expensive, rare, or otherwise valuable starting materials will generate
significant demand for those starting materials, which would limit graphene’s
use in everyday materials. Therefore, it is absolutely imperative to find a way
that graphene can be made reliably from a cheap (or free) resource. If graphene
could be made from things that would otherwise go to waste, this would
significantly decrease the long-term price of graphene so that anyone could have
access to it.

If such a process were available, those who invented it would be regarded as
highly as Fritz Haber, who won the Nobel Prize in Chemistry in 1918 “for the
synthesis of ammonia from its elements.” Haber took nitrogen from the air and
hydrogen from methane gas, combined them under high pressure and temperature
over a metal catalyst to speed up the reaction, and boom! Ammonia came out of
the reaction, ready to be put into fertilizer. Haber’s invention quite literally
feeds the world.

What starting material could we use for carbon as a feedstock that would not
unduly tax typical sources of carbon, such as fossil fuels or natural gas?
Certainly, one option is to harvest carbon dioxide from the air and reduce it
back to C. That is an extremely energy-intensive process, however, and no
technological advances within the known laws of physics will reduce that energy
demand.

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That leads us back to thinking about something that is abundant, all around us,
makes efficient use of capturing carbon, and can capture this carbon without
direct energy input from humans: plants. Plants take in passive solar light and
carbon dioxide from the atmosphere and grow in most places of their own accord.
Huge trees are carbon sinks made possible by photosynthesis. Lots of plant waste
is generated per year, which might go toward creating graphene if it would
otherwise take up space within a landfill. Invasive species of plants, such as
kudzu and bamboo in the southeastern United States, can serve as a feedstock.

James Tour took this to a logical extreme in 2011 on a bet. Tour had been
thinking about the ways to use the carbon already free around us in the
environment. He had been successful in converting Plexiglas
(polymethylmethacrylate) to graphene, and table sugar was his next target. After
having turned table sugar into pyrolysis-CVD graphene flakes on a piece of
copper foil, one of his colleagues perked up, and dared Tour to make graphene
out of six different carbon-based materials: cookies, chocolate, grass,
polystyrene (Styrofoam), roaches, and dog feces. This result is interesting, as
the Australian laboratory mentioned above failed when using a copper foil
substrate for their soybean oil conversion process. What these conflicting
stories mean, however, is that there is vast room for improvement in our
understanding of the way graphene forms from gaseous molecules.

Using the same method employed with the table sugar, all of the proposed unusual
carbon sources produced small flakes of high-quality graphene. Tour and his
coworkers stressed that no preparation or purification of these weird materials
was necessary. In other words, a roach leg could be dropped on the foil, heated
up, and come out as graphene. You can’t even make a cake with that much ease.
Tour’s 2011 finding, combined with the CVD-epitaxy findings from the German team
in 2016, could provide a clear route to making large, cheap, defect-free
graphene samples.


OUTER SPACE

At the moment, NASA is researching ways to process waste carbon dioxide from
astronauts’ breath on the International Space Station into graphene. This
improvement to the life-support system would have a twofold bonus. For one, a
waste material such as carbon dioxide otherwise requires sequestration with
special chemicals that need to be shipped up with special deliveries from Earth.
Processing the carbon dioxide into graphene would mean that fewer resupply
missions would be necessary.

Turning carbon dioxide into graphene provides another benefit as well: The
resulting graphene could be incorporated into new solar cells, or could be put
to use in the water purification systems, or a thousand other possibilities,
rather than trying to eject it out the airlock. This possibility helps to
lengthen the umbilical cord between the station and Earth. Eventually we need to
cut that umbilical entirely, if we are to ever send humans on extended missions
to other planets and beyond.

Strictly speaking, graphene is two-dimensional, being a single layer of atoms.
Researchers at MIT have found, however, that when subjected to heat or pressure,
graphene takes on a complex shape called a gyroid, which is three-dimensional
but riddled with holes or pores (a model is shown here). The combination of
strength and porosity may make graphene suitable for the manufacture of new,
lightweight construction materials—for example, for use in bridges.

Melanie Gonick/MIT

Luckily, there is a side benefit for us Earthlings as well. A process like this
would also be able to take carbon dioxide from the atmosphere and turn our own
breath into organic electronics or a million other things in which uses for
graphene could be found. Although turning carbon dioxide into graphene would not
be cost-effective or energy efficient on Earth (right now), abundant power from
solar cells aboard the International Space Station could provide the kick
necessary to strip oxygen from the carbon dioxide. Companies could “mine” the
atmosphere to take carbon dioxide from processes that can’t help but produce it,
and turn the waste gas into a raw material for further products. The “waste not,
want not” principle that every hiker and explorer knows well means that a system
designed for reuse will ultimately increase the chances of a mission’s success
(whether it be on Earth or in space), while also minimizing environmental
impact. Redundancy on Earth can only be a good thing. In outer space, it is an
absolute requirement.


INDUSTRY STANDARDS

Graphene is composed of pure carbon as a single sheet in a flat hexagon pattern.
Any changes to this structure mean that the resulting chemical is no longer
technically graphene; instead it is a graphene derivative. Graphene behaves very
differently from graphene oxide, and both behave differently from lithium-doped
graphene.

Take, for instance, the difference between two samples of exfoliated graphite
from two different companies. One sample could have been exfoliated by a process
that is rather harsh, so that the exfoliation added defects of oxygen atoms or
alcohol groups to the graphene flakes. The second sample could have been
exfoliated more gently, in a way that preserves the carbon-only structure
without adding holes or tears in the flakes. Which is better than the other? How
can you tell them apart? Both manufacturers slapped “Graphene” on the bottle and
sold it to you at an exorbitant price; they must be indistinguishable in a
product formulation and therefore you can just go with the cheaper option,
right? Not so. The source of the graphene and how it was prepared have
tremendous implications for its performance. A device might not work at all, or
it may just work worse than expected.

Standards do not exist yet for graphene production, and not all companies are on
board with establishing standards at all. These standards could take many
possible forms and do not necessarily mean legal regulation. That would be quite
obviously an extreme measure and would be unenforceable in other countries.
Considering the international playing field for graphene, this would be a
significant hindrance. Nobody wants that. However, at this point in the game,
most products labeled “graphene” on the market are not actually graphene.
Rather, they are thin flakes of graphite that can be up to a few hundred layers
thick. Some manufacturers are able to produce flakes with a high yield of
monolayer graphene, and these companies will gladly tell you that they produce a
guaranteed percentage of monolayer graphene, with most of the rest of the sample
consisting of flake aggregates between two and ten layers thick. A word to those
of you who are interested in using true graphene for an application—ask about
these flake thicknesses from your supplier. It is absolutely critical to take
what they say to an independent lab for verification to establish a definitive
level of trust.



Rice University chemist James Tour and others are exploring the potential for
imprinting patterns and structures in graphene onto food. In the future, this
application may be a means to produce edible devices on fruits or packaged
meals, for example, which would make it possible to trace their path from the
farm or factory all the way to the consumer.

Jeff Fitlow/Rice University

Ideally, standards set forth should grade graphene, taking into account
parameters such as the yield of monolayer flakes, the size of those flakes, and
the elemental analysis of the sample (at a minimum). That way, a vendor can
stand behind the production cost of their so-called graphene sample, rather than
jacking up the cost for some graphite that has been pulverized in a kitchen
blender. Caveat emptor. On the other hand, if a vendor is selling
high-surface-area epitaxially grown graphene with a repeatable or verifiable
certificate of analysis, then you may have a justification to pay more for that
sample.


CARBON EVERYWHERE

Graphene’s potential to change the course of innumerable industries is only
limited by the imagination and cunning of business leaders who share a vision
with a knowledgeable chemist, engineer, or physicist. Bolder, more enterprising
technologies will develop by adding different molecules to graphene, treating it
as a scaffold onto which biomolecules can be grafted, perhaps as passive sensors
for chemical and biological weapons.

Graphene as a coating material could even change industries in the short term.
Because graphene is mostly nonreactive and very hydrophobic, any surface coated
in a layer of graphene would move through water with decreased friction from
water-metal surface tension. A graphene layer on tanker ships would make
worldwide shipping more effective. Adding a graphene layer onto a windshield
would create a surface that was not only transparent (because graphene itself is
transparent) but would naturally repel water and increase driver safety in
rainstorms. Want to reduce air drag on a high-performance car? Ensure that its
shell is perfectly atomically flat by encasing it in graphene. Maybe an
especially talented engineer in the future will design a vehicle with perfectly
smooth and regular flow over the car’s body, eking out a few more horsepower
from the engine and a few more miles per gallon from the tank.

And all these things might be made possible by one of the most abundant, most
versatile, and most essential of all elements, carbon—the same carbon that forms
the basis of all known forms of life on Earth and enables graphene to be formed:
graphene—the superstrong, superthin, and superversatile material that will
revolutionize the world.

--------------------------------------------------------------------------------

This article is excerpted and adapted from Graphene: The Superstrong, Superthin,
and Superversatile Material that will Revolutionize the World (Prometheus Books,
2018). Reprinted with permission from the publisher.



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