Los Angeles (CA) - The path toward reliably and effectively creating sheets of graphene has just gotten one step closer. Researchers at UCLA used a bath of hydrazine (nitrogen + hydrogen) and graphite oxide paper to create the sheets which are just one atom thick. In addition, and perhaps most exciting, the electrical properties of graphene created in this way allow field-effect devices (semiconductors) with drive currents 1000x higher than has been previously reported. In short, the elusive dream of graphene-based technologies applied to semiconductors, optics, solar cells, batteries, and pretty much everything else, is closer now than ever before.
Breakthrough
Two current methods are used to create graphene, a single-atom thick layer of pure carbon which looks like a chain-link fence. The first is called the "drawing method" The drawing method is a hit-and-miss method to be sure. Using graphite crystals and essentially pealing back one layer at a time like an onion, the scientists hope to extract a good one which is just one atom thick. This is an arduous process wrought with disappointment yielding only tiny bits of graphene that are really unsuitable for all but the most hardy researcher.
The second method is called the "reduction method". It uses silicon carbide heated up to 1100 degrees Celsius. And just like making a good tomato sauce for pasta, the heat reduces it down to until only graphite and (hopefully) graphene is left.
Neither of these two methods are reliable or truly effective as the graphene they produce is not uniform or pure. These undesirable traits inhibit research and skew findings.
The UCLA team, led by Yang Yang, a professor of materials science, developed a new method called "hydrazine reduction." A hydrazine bath breaks down the graphite oxide chemically producing graphene sheets that are extremely pure. The sheets are also large, up to 800 square microns in size. They allow for synthesis or generation in reliable quantities that has never before been possible.
The researchers report production of sheets measuring up to 20 micrometers by 40 micrometers, though most are smaller. Still, these sizes are the largest ever produced and are nearly suitable for certain kinds of commercial electronic applications even as they are. And of course, they are wholly suitable for large scale graphene research in many industries.
Controlling the process
The team also discovered that graphene production can be controlled merely by varying the concentration and composition of the hydrazine solution. Said fellow researcher Matthew Allen, "These graphene sheets are by far the largest produced, and the method allows great control over deposition. Chemically converted graphene can now be studied in depth through a variety of electronic tests and microscopic techniques not previously possible."
As with most all great announcements, however, the process is nowhere near ready for mass production or true commercial applications. Said Yang, "This technology [hydrazine reduction] ... can dramatically simplify preparing electronic devices. It thus holds great promise for future large-area, flexible electronics."
Why graphene?
Richard Kaner, a UCLA professor of chemistry and biochemistry who worked on the project, said, "Graphene is a cutting-edge nanomaterial and one which has great potential to revolutionize electronics and many other fields." And he's right.
Researchers have looked at graphene because of its wide electrical properties. In fact, it has been researched as a source material for revolutionary forms of batteries, semiconductors, solar cells, nano-optics, and even room temperature superconductors.
If large graphene sheets can be distributed, studied, and reliably produced, and if follow-on enhancements to the synthesis process can yield even larger sheets (of 1mm square, for example), then the fundamental nature of a great many common devices we all use could be altered in the years to come. No longer will they based on materials which have served so well for decades.
The migration to graphene would allow previously impossible products. Computers with graphene core processors, batteries that last for days without recharging, and solar cells approaching the theoretical limits of the science, may all be possible. That is, at least, if all the hubbub about graphene is to be believed.
Funding
The research was carried out at the California NanoSystems Institute (CNSI) at UCLA. It was established in 2000 with $100 million from the state of California and $250 million in federal research grants and industry funding from undisclosed sources. CNSI researchers study the fundamental components of materials. Scientists in the areas of biology, chemistry, biochemistry, physics, mathematics, computational science and engineering are focused on measuring, modifying and manipulating atoms and molecules.
Read more at UCLA's CNSI.
Breakthrough
Two current methods are used to create graphene, a single-atom thick layer of pure carbon which looks like a chain-link fence. The first is called the "drawing method" The drawing method is a hit-and-miss method to be sure. Using graphite crystals and essentially pealing back one layer at a time like an onion, the scientists hope to extract a good one which is just one atom thick. This is an arduous process wrought with disappointment yielding only tiny bits of graphene that are really unsuitable for all but the most hardy researcher.
The second method is called the "reduction method". It uses silicon carbide heated up to 1100 degrees Celsius. And just like making a good tomato sauce for pasta, the heat reduces it down to until only graphite and (hopefully) graphene is left.
Neither of these two methods are reliable or truly effective as the graphene they produce is not uniform or pure. These undesirable traits inhibit research and skew findings.
The UCLA team, led by Yang Yang, a professor of materials science, developed a new method called "hydrazine reduction." A hydrazine bath breaks down the graphite oxide chemically producing graphene sheets that are extremely pure. The sheets are also large, up to 800 square microns in size. They allow for synthesis or generation in reliable quantities that has never before been possible.
The researchers report production of sheets measuring up to 20 micrometers by 40 micrometers, though most are smaller. Still, these sizes are the largest ever produced and are nearly suitable for certain kinds of commercial electronic applications even as they are. And of course, they are wholly suitable for large scale graphene research in many industries.
Controlling the process
The team also discovered that graphene production can be controlled merely by varying the concentration and composition of the hydrazine solution. Said fellow researcher Matthew Allen, "These graphene sheets are by far the largest produced, and the method allows great control over deposition. Chemically converted graphene can now be studied in depth through a variety of electronic tests and microscopic techniques not previously possible."
As with most all great announcements, however, the process is nowhere near ready for mass production or true commercial applications. Said Yang, "This technology [hydrazine reduction] ... can dramatically simplify preparing electronic devices. It thus holds great promise for future large-area, flexible electronics."
Why graphene?
Richard Kaner, a UCLA professor of chemistry and biochemistry who worked on the project, said, "Graphene is a cutting-edge nanomaterial and one which has great potential to revolutionize electronics and many other fields." And he's right.
Researchers have looked at graphene because of its wide electrical properties. In fact, it has been researched as a source material for revolutionary forms of batteries, semiconductors, solar cells, nano-optics, and even room temperature superconductors.
If large graphene sheets can be distributed, studied, and reliably produced, and if follow-on enhancements to the synthesis process can yield even larger sheets (of 1mm square, for example), then the fundamental nature of a great many common devices we all use could be altered in the years to come. No longer will they based on materials which have served so well for decades.
The migration to graphene would allow previously impossible products. Computers with graphene core processors, batteries that last for days without recharging, and solar cells approaching the theoretical limits of the science, may all be possible. That is, at least, if all the hubbub about graphene is to be believed.
Funding
The research was carried out at the California NanoSystems Institute (CNSI) at UCLA. It was established in 2000 with $100 million from the state of California and $250 million in federal research grants and industry funding from undisclosed sources. CNSI researchers study the fundamental components of materials. Scientists in the areas of biology, chemistry, biochemistry, physics, mathematics, computational science and engineering are focused on measuring, modifying and manipulating atoms and molecules.
Read more at UCLA's CNSI.
Shop Keywords: graphene carbon carbid hydrazine hydrogen nitrogen semiconductor solar cell battery optic optical UCLA University Los Angeles CNSI California NanoSystems nano system systems institute