Graphene belongs to a group of new materials which are heavily researched in order to understand
their qualities and possible uses. Our website keeps an eye on news and breakthrough research and
we select only the most interesting news on graphene, at least in our opinion. This list is not
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30.5.2013. Graphene could be used as a means to define the ampere
The SI system of measures consists of many units, of which seven are considered base units.
These base units are meter, kilogram, second, kelvin, mole, candela and ampere. Most of these units
are well defined and constant, with the kilogram being an exception (kilogram is still defined as
the mass of the International Kilogram Prototype).
Ampere is well-defined as well, but its definition is a bit clumsy for practical use. The ampere
is defined as the constant current which, if maintained in two parallel conductors of infinite
length, 1 meter apart and straight, would produce a force between these two conductors
equal to 2x10-7
Graphene could come in handy in the re-definition of the ampere. Scientists have managed to
create an electron pump which can emit individual electrons at command using graphene. These graphene electron
pumps could be used to produce a current of exactly one ampere. Since the charge of a single
electron is well-known, the ampere could be prototyped on site as needed as a flow of
one couloumb of charge per second using one single electron pump, or many individual graphene
Aside from this metrology use of the graphene single-electron pump, there are many potential
uses in experimental quantum physics. These uses could lead to some interesting experiments
and proofs. We find it exciting that graphene could offer to change our world in such a fundamental
way as changing the definition of one of the base units of the SI system.
4.5.2013. Resonant tunnelling and negative differential conductance in graphene transistors
allows terahertz operating frequencies.
Graphene's chemical stability combined with properties of other free two-dimensional crystals
allows scientists to stack these crystalline materials and create novel devices using
advanced functional materials. Scientists have managed to induce a tunneling effect which produces
a negative differential conductance at room temperature using a layer of boron nitride a few atoms
thick, sandwiched between graphene electrodes.
The tunnel effect has been known for almost half a century, however conventional tunneling devices
were tens of nanometers thick, while these new graphene-boron nitride tunneling transistors are
merely a few atomic layers thick. Their miniscule thickness allows these transistors to achieve
ultra-fast transit times. In theory, these devices could be applied to high-frequency logic circuits.
This device can be controlled by applying a variable gate voltage. The current through the
transistor rises with the applied gate voltage increase until it reaches a maximum value, after
which it decreases steadily. This area of output current decrease as gate voltage increases can be
used similarly to the way tunneling diodes are used, only at much higher frequencies.
24.4.2013. Synthesis of graphene oxide/polyacrylic acid nanocomposite hydrogel
A review of studies focused on enhancing the thermal conductivity of phase change materials (PCM)
for thermal energy storage upon introduction of nanostructures is presented. These emerging materials
have only been studied since 2005 and represent a clear departure from previous/existing practices of
utilizing fixed, stationary high-conductivity inserts/structures into PCM. Carbon-based nanostructures
(nanofibers, nanoplatelets and graphene flakes), carbon nanotubes, both metallic (Ag, Al, C/Cu and Cu)
and metal oxide (Al2O3, CuO, MgO and TiO2) nanoparticles and silver nanowires have been explored as the
materials of the thermal conductivity promoters. Emphasis of the work so far has been placed on the
dependence of the enhanced thermal conductivity on mass fraction of the nanostructures and temperature
for both liquid and solid phases, however issues related to modifications of the degree of supercooling,
melting temperature, viscosity, heat of fusion, etc. are also reported.
In general, carbon-based nanostructures and carbon nanotubes exhibit far greater enhancement of thermal
conductivity in comparison to metallic/metal oxide nanoparticles due to the high aspect-ratio of these
nanofillers. Utilizing a figure of merit for the observed thermal conductivity enhancement, the majority
of 340+ measured data points in both liquid and solid phases are summarized.
23.4.2013. Growing better nanowires on graphene
Researchers at the University of Illinois produced III-VI compound semiconductors. This was previously
not feasible using silicon, and researchers used a graphene substrate instead of the old-fashioned
silicon. They used a process called MOCVD (MetalOrganic Chemical Vapour Deposition) to deposit
In-Ga-As (Indium-Gallium-Arsenic) semiconductors onto the surface of graphene. The semiconductor
atoms self-assembled into a nanostructure resembling a crystalline form. This is the first time
that these three semiconductors were merged in this fashion.
This discovery will allow scientists to grow coaxial core-shell structures in a single step instead
of a two-step process. A single step process ensures a better interface between the nanostructure
and the substrate, since the growth process is spontaneous. This is because the distance between
the atoms in a InAs crystal structure is the same as the distance between carbon atoms in graphene.
Therefore, the InAs fits into the space perfectly, like the final piece in a puzzle, allowing
gallium to form a shell around the InAs core.
Original research text: InxGa1-xAs Nanowire Growth on Graphene: van der Waals Epitaxy Induced Phase Segregation
This page was last modified: May 4th, 2013.