Is it Possible Graphene Could Be Used For Desalination?
There have been a couple of articles over the last year on the use of “graphene-based materials.” Graphene is interesting because– rolled up its a carbon nanotubes. However, laid out flat — its graphene — and it is cheap and plentiful.
Work appeared out of Northwestern last year:
“This research provides a basis for developing a new class of composite materials for many applications, through tuning of their electrical and thermal conductivity, their mechanical stiffness, toughness and strength, and their permeability to flow various gases through them,” said Ruoff, professor of mechanical engineering in the McCormick School of Engineering and Applied Science. “We believe that manipulating the chemical and physical properties of individual graphene-based sheets and effectively mixing them into other materials will lead to discoveries of new materials in the future.”
Another team led by Andre Geim from the University of Manchester in England:
But Geim and colleagues say that the appeal of this kind of carbon lies not with nanotubes in themselves, but with the underlying fabric: the flat sheets of graphene. They have developed methods for splitting graphite apart into its separate layers and lying them down flat on a surface, where their electrical properties can be studied. A graphene sheet is electrically conducting, behaving essentially like a two-dimensional metal. But it is a strange kind of metal, with properties dictated by quantum mechanics. For example, even if there are no mobile electrons to carry an electrical current, the electrical conductivity can never fall below a certain minimum value: it is like an electron gate that can never be fully closed.
And the Manchester researchers have shown that graphene can be fashioned into a device called a spin valve, which discriminates between mobile electrons according to their spin.
Maybe too this could be worked into a filter of some sort to take out charged Na or Cl ions.
This week another article came out on the subject:
Physicists pioneer new super-thin technology (Update)
Atomic gauze hanging on a scaffold of golden wires: It is the thinnest material you will ever see. Credit: University of Manchester
Researchers have used the world’s thinnest material to create a new type of technology, which could be used to make super-fast electronic components and speed up the development of drugs.
Physicists at The University of Manchester and The Max-Planck Institute in Germany have created a new kind of a membrane that is only one atom thick.
An artist’s impression of the chicken wire of carbon atoms. Credit: University of Manchester
It’s believed this super-small structure can be used to sieve gases, make ultra-fast electronic switches and image individual molecules with unprecedented accuracy.
The findings of the research team is published today in the journal Nature.
Two years ago, scientists discovered a new class of materials that can be viewed as individual atomic planes pulled out of bulk crystals.
These one-atom-thick materials and in particular graphene – a gauze of carbon atoms resembling chicken wire – have rapidly become one of the hottest topics in physics.
However, it has remained doubtful whether such materials can exist in the free state, without being placed on top of other materials.
Now an international research team, led by Dr Jannik Meyer of The Max-Planck Institute in Germany and Professor Andre Geim of The University of Manchester has managed to make free-hanging graphene.
The team used a combination of microfabrication techniques used, for example, in the manufacturing of microprocessors.
A metallic scaffold was placed on top of a sheet of graphene, which was placed on a silicon chip. The chip was then dissolved in acids, leaving the graphene hanging freely in air or a vacuum from the scaffold.
The resulting membranes are the thinnest material possible and maintain a remarkably high quality.
Professor Geim – who works in the School of Physics and Astronomy at The University of Manchester – and his fellow researchers have also found the reason for the stability of such atomically-thin materials, which were previously presumed to be impossible.
They report that graphene is not perfectly flat but instead gently crumpled out of plane, which helps stabilise otherwise intrinsically unstable ultra-thin matter.
Professor Geim and his colleagues believe that the membranes they have created can be used like sieves, to filter light gases through the atomic mesh of the chicken wire structure, or to make miniature electro-mechanical switches.
It’s also thought it may be possible to use them as a non-obscuring support for electron microscopy to study individual molecules.
This has significant implications for the development of medical drugs, as it will potentially allow the rapid analysis of the atomic structures of bio-active complex molecules.
“This is a completely new type of technology – even nanotechnology is not the right word to describe these new membranes,” said Professor Geim.
“We have made proof-of-concept devices and believe the technology transfer to other areas should be straightforward. However, the real challenge is to make such membranes cheap and readily available for large-scale applications.”
A second article this week on the subject by the same team suggests the work could be used for transistors.
Another group this week at Cornell
found that a single sheet of graphene, a form of carbon atoms in a plane just one atom thick, can be isolated and used as an electromechanical resonator.