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Carbon “Miracle Material”
Graphene
Applications
Potential graphene applications include lightweight,
thin, flexible, yet durable display screens, electric circuits, and solar
cells, as well as various medical, chemical and industrial processes enhanced
or enabled by the use of new graphene materials.
In
2013, the European Union made a €1 billion grant to be used for research into
potential graphene applications.
In
2013 the Graphene Flagship consortium formed, including Chalmers University of
Technology and seven other European universities and research centers, along
with Nokia.
The funding will be used to set up a communication
system to allow the scientific and business interests to meet and develop new
uses for graphene and ways to integrate it into future products. It will be
headquartered in the Swedish Chalmers University of Technology
Graphene consists of carbon atoms laid down in an
atom-thick layer of material, and it holds great promise not only for faster
and more efficient electronics but also for a host of other applications
ranging from desalinization to the construction of a space elevator.
Drug delivery
Researchers in Monash University discovered that the
sheet of graphene oxide can be transformed into liquid crystal droplets
spontaneously – like a polymer - simply by placing the material in a solution
and manipulating the pH.
The
graphene droplets change their structure at the presence of an external
magnetic field. This finding opens the door for potential use of carrying drug
in the graphene droplets and drug release upon reaching the targeted tissue
when the droplets change shape under the magnetic field.
Another
possible application is in disease detection if graphene is found to change
shape at the presence of certain disease markers such as toxins.
A
graphene 'flying carpet' was demonstrated to deliver two anti-cancer drugs
sequentially to the lung tumor cells (A549 cell) in a mouse model.
Doxorubicin
(DOX) is embedded onto the graphene sheet, while the molecules of tumor
necrosis factor-related apoptosis-inducing ligand (TRAIL) are linked to the
nanostructure via short peptide chains.
Injected
intravenously, the graphene strips with the drug playload preferentially
concentrate to the cancer cells due to common blood vessel leakage around the
tumor.
Receptors
on the cancer cell membrane bind TRAIL and cell surface enzymes clip the
peptide thus release the drug onto the cell surface.
Without
the bulky TRAIL, the graphene strips with the embedded DOX are swallowed into
the cells. The intracellular acidic environment promotes DOX's release from
graphene.
TRAIL
on the cell surface triggers the apoptosis while DOX attacks the nucleus. These
two drugs work synergistically and were found to be more effective than either
drug alone.
Electronics
For integrated circuits, graphene has a high carrier
mobility, as well as low noise, allowing it to be used as the channel in a
field-effect transistor. Single sheets of graphene are hard to produce and even
harder to make on an appropriate substrate.
In 2008, the smallest transistor so far, one atom
thick, 10 atoms wide was made of graphene. IBM announced in December 2008 that
they had fabricated and characterized graphene transistors operating at GHz
frequencies.
In
May 2009, an n-type transistor was announced meaning that both n and p-type
graphene transistors had been created.
A
functional graphene integrated circuit was demonstrated – a complementary
inverter consisting of one p- and one n-type graphene transistor. However, this
inverter suffered from a very low voltage gain.
According to a January 2010 report, graphene was
epitaxially grown on SiC in a quantity and with quality suitable for mass
production of integrated circuits.
At
high temperatures, the quantum Hall effect could be measured in these samples.
IBM built 'processors' using 100 GHz transistors on 2-inch (51 mm) graphene
sheets.
In June 2011, IBM researchers announced that they had
succeeded in creating the first graphene-based integrated circuit, a broadband
radio mixer.
The
circuit handled frequencies up to 10 GHz. Its performance was unaffected by
temperatures up to 127 °C.
Transistors
In 2013 researchers reported the creation of
transistors printed on flexible plastic that operate at 25 gigahertz,
sufficient for communications circuits and that can be fabricated at scale.
The
researchers first fabricate the non-graphene-containing structures — the
electrodes and gates — on plastic sheets.
Separately,
they grow large graphene sheets on metal, then peel it off and transfer it to
the plastic.
Finally,
they top the sheet with a waterproof layer. The devices work after being soaked
in water, and are flexible enough to be folded.
Transparent conducting
electrodes
Graphene's high electrical conductivity and high
optical transparency make it a candidate for transparent conducting electrodes,
required for such applications as touchscreens, liquid crystal displays,
organic photovoltaic cells, and organic light-emitting diodes.
In
particular, graphene's mechanical strength and flexibility are advantageous
compared to indium tin oxide, which is brittle. Graphene films may be deposited
from solution over large areas.
Piezoelectric effect
Density functional theory simulations predict that
depositing certain adatoms on graphene can render it piezoelectrically
responsive to an electric field applied in the out-of-plane direction.
This
type of locally engineered piezoelectricity is similar in magnitude to that of
bulk piezoelectric materials and makes graphene a candidate for control and
sensing in nanoscale devices.
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