But in order to construct new materials and devices, researchers first need to understand how these tiny units interact with each other.
One such building block is graphite oxide, which is often used to make graphene — a hotly studied material that scientists believe could be used to produce low-cost carbon-based transparent and flexible electronics. Like graphene, graphite oxide is essentially a sheet that is only one atom thick, but can be as wide as tens of micrometers.
Jiaxing Huang, assistant professor of materials science and engineering at Northwestern University, and his research group at the McCormick School of Engineering and Applied Science set out to investigate how these graphite-oxide sheets assemble. Their results, published as the cover article in the Jan. 26 issue of the Journal of the American Chemical Society, surprised them.
“We were very curious how these extremely thin two-dimensional sheets interact with each other,” Huang says. “This knowledge can also help to prepare better graphene thin films.”
Huang and his group studied the sheets by putting them onto a water surface — a process called Langmuir-Blodgett assembly, which makes the sheets stay flat and allows scientists to move them around.
The effect reminded the researchers of water lilies on a pond, and Huang asked his sister to help to create a Chinese water painting similar to that of Claude Monet’s series of paintings “Water Lilies” to demonstrate the idea. The artwork was chosen as one of the first illustrated covers for the 130-year-old journal.
Researchers used a barrier to push the sheets together to see how they would interact and then “fished” the interacting sheets off the water surface using glass slides or silicon wafers. Huang and his colleagues expected to see that individual sheets had stacked one upon the other, like a shuffled deck of cards. Instead they found that the edges of the graphite oxide sheets rumpled as they were pushed together.
“This was quite a surprise for us,” Huang says. “Now we understand that electrostatic repulsion is the dominant interaction when these sheets are pushed together in this edge-to-edge geometry. This prevents graphite oxide layers from overlapping with each other.”
When squeezed even further, the sheets eventually formed an interlocking structure that becomes a continuous membrane.
This film — consisting of flat, non-overlapping single layers tiling over large areas — has been very difficult to achieve by conventional thin-film processing techniques such as drop casting or spraying.
This breakthrough could have two immediate technological impacts. “Because we can keep them close to each other and still keep them flat, it provides high coverage of the surface with the single layers — which in turn will translate into high successful yield in graphene device fabrication,” Huang says. “On the other hand, the continuous graphite oxide monolayer can be made into a transparent conductor after conversion to graphene.”
Now, after studying how they interact edge-to-edge, Huang hopes to study face-to-face contact of the graphene-based materials. Stacking graphene sheets directly on top of each other will form graphite and lose the advantages of the single-atom-thick graphene materials. But Huang hopes to find a way to stack graphene without making graphite, which could create functional materials for energy-related applications such as electrodes for batteries, ultracapacitors and fuel cells.
“If we are good at making these tiny building blocks and if we can control how they assemble, we will create a lot of wonderful new things,” Huang says.
In addition to Huang, co-authors of the paper include National Science Foundation graduate research fellow Laura Cote and postdoctoral fellow Franklin Kim, both of whom, according to Huang, “did a wonderful job” to create the high-quality graphite oxide sheets used in the experiment.
Kyle Delaney | EurekAlert!
Further reports about: > Fuel cells > Langmuir-Blodgett assembly > Large-Scale Graphene Films > Nanomaterial > Water > Water Lilies > building block > edge-to-edge geometry > electrodes for batteries > electrostatic repulsion > graphene > graphite oxide > silicon wafer > single-atom-thick graphene materials > ultracapacitors > water surface
Argon is not the 'dope' for metallic hydrogen
24.03.2017 | Carnegie Institution for Science
Researchers make flexible glass for tiny medical devices
24.03.2017 | Brigham Young University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy