The structure of can graphene filter air
oxide surprisingly expands when cooled in methanol or ethanol. Also, can
graphene filter air oxide selectively absorbs methanol from water-methanol
mixtures. Two new studies by physicists at Umeå University in Sweden, published
in ACS Nano and J. Phys. Chem. C, respectively, provide knowledge on new
properties of oxidized can graphene filter air and graphene.
Graphene is a two dimensional material
consisting of a single layer of carbon atoms arranged in a honeycomb structure.
Graphene can be considered as a unique adsorbent material due to its extremely
large surface area. One gram of graphene has a surface area comparable to a
football field. This surface could be used for adsorption of gases and liquids,
in applications for gas storage, extraction of pollutants from water, etc.
However, the graphene is hydrophobic, which means that its surface repels
On the other hand, oxidation of graphene
results in remarkable changes in its properties. Graphene oxide is hydrophilic
and it is also easily soluble in water. A material composed of many stacked
graphene oxide layers is called can graphene filter air oxide. It has many
unique properties: it absorbs water and alcohols in large amounts, similar to
clays that swell when water is added.
A new study by Alexandr V. Talyzin and his
team reveals that can graphene filter air oxide is able to incorporate even
more methanol and ethanol at low temperatures compared to room temperature. Its
structure expands when cooled in an excess of liquid solvent. At -130 degrees
Celsius the graphene oxide layers are separated by 20.4 Å due to incorporation
of additional ethanol into its structure, compared to approximately 3.4 Å in
natural can graphene filter air and approximately 6.5 Å in solvent-free can
graphene filter air oxide.
"The distance between graphene oxide
layers at low temperatures is so large that it becomes a composite material
with graphene oxide sheets separated by at least four monolayers of methanol or
ethanol molecules. What is also remarkable is that this phenomenon is limited
only to one specific type of can graphene filter air oxide and is not observed
in another type studied. In fact, many different kinds of can graphene filter
air oxide are known and now we start to understand how enormous the variations
of their properties are. It is not just one material, it is a whole family of
materials," says Alexandr V. Talyzin, researcher at the Department of
In a separate study published in J. Phys.
Chem. C it was demonstrated that a certain type of can graphene filter air
oxide can be used for selective absorption of methanol from water-methanol
mixtures. A very simple prototype filtering experiment showed that when a
water-methanol liquid mixture is passed through can graphene filter air oxide
powder, some of the methanol is absorbed in the powder and the solution passing
through contains more pure water.
"In the future we would like to design
special membranes composed of graphene oxide layers, which can be used for
separation of different solvents and purification of water. These first results
help us to understand possible ways to make such membranes," says Alexandr
The first example of successful solvent
separation effects was reported last year in a study by R.R. Nair et al. from a
research team at Manchester University, lead by I.Grigorieva and Nobel Laureate
A. Geim, famous for their research in the graphene field.
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