Ever since University of Manchester scientists Andre Geim and Konstantin Novoselov first isolated flakes of graphene in 2004 using that most high-tech pieces of equipment – adhesive tape – the one-atom sheet of carbon has continued to astound researchers with its remarkable properties. Now Professor Sir Andre Geim, (he’s now not only a Nobel Prize winner but also a Knight Bachelor), has led a team that has added superpermeability with respect to water to graphene’s ever lengthening list of extraordinary characteristics.

Graphene has already proven to be the thinnest known material in the universe, strongest material ever measured, the best-known conductor of heat and electricity, and the stiffest known material, while also the most ductile. But it seems the two-dimensional lattice of carbon atoms just can’t stop showing off.

Stacking membranes of a chemical derivative of graphene called graphene oxide, which is a graphene sheet randomly covered with other molecules such as hydroxyl groups OH-, scientists at the University of Manchester created laminates that were hundreds of times thinner than a human hair but remained strong, flexible and were easy to handle.

When the team sealed a metal container using this film, they say that even the most sensitive equipment was unable to detect air or any other gas, including helium, leaking through. The team then tried the same thing with water and, to their surprise, found that it evaporated and diffused through the graphene-oxide membranes as if they weren’t even there. The evaporation rate was the same whether the container was sealed or completely open.

“Graphene oxide sheets arrange in such a way that between them there is room for exactly one layer of water molecules. They arrange themselves in one molecule thick sheets of ice which slide along the graphene surface with practically no friction, explains Dr Rahul Nair, who was leading the experimental work. “If another atom or molecule tries the same trick, it finds that graphene capillaries either shrink in low humidity or get clogged with water molecules.”

Professor Geim added, “Helium gas is hard to stop. It slowly leaks even through a millimetre -thick window glass but our ultra-thin films completely block it. At the same time, water evaporates through them unimpeded. Materials cannot behave any stranger. You cannot help wondering what else graphene has in store for us.”

Although graphene’s superpermeability to water makes it suitable for situations where water needs to be removed from a mixture without removing the other ingredients, the researchers don’t offer ideas for any immediate applications that could take advantage of this property. However, they did seal a bottle of vodka with the membranes and found that the distilled solution did indeed become stronger over time. But they don’t foresee graphene being used in distilleries.

However, Professor Geim adds, “the properties are so unusual that it is hard to imagine that they cannot find some use in the design of filtration, separation or barrier membranes and for selective removal of water.”

Sourced & published by Henry Sapiecha

Silver is a known killer of harmful bacteria, and has already been incorporated into things such as antibacterial keyboards, washing machines, water filters, and plastic coatings for medical devices. Now, scientists have added another potential product to the list: silver nanoparticle-impregnated “killer paper” packaging, that could help keep food from spoiling.

Led by Aharon Gedanken from Israel’s Bar-Ilan University, the team discovered that paper could be covered with silver nanoparticles through the application of ultrasonic radiation – a process known as ultrasonication. It involves the formation and subsequent collapse of acoustic bubbles near a solid surface, which creates microjets that throw the desired nanoparticles onto that surface. To the team’s knowledge, this was only the second time that ultrasonication had ever been attempted on paper.

Unlike previous attempts at creating antibacterial paper, this one-step method was reportedly quite effective, and produced a smooth, homogenous, long-lasting coating. By varying the nanoparticle concentration and the application time, the thickness of the coating could be varied as needed. When exposed to E. coli and S. aureus bacteria, both of which cause food poisoning, the paper killed them all off within three hours.

The scientists stated that the ultrasonication process could also be used to apply other nanomaterials to paper, which could be used to tweak its hydrophobicity, conductivity, or texture.

While the addition of ionic silver to foods has been used in the past to ward off bacteria, the paper would reportedly serve as a longer-term solution, as it would act as a slow-release reservoir for the silver. Germany’s Fraunhofer Institute for Process Engineering and Packaging has previously looked into the use of sorbic acid-coated plastic as an antibacterial food wrap.

The killer paper research was recently published in the journal Langmuir.

Sourced & published by Henry Sapiecha

Materials that can repair themselves are generally a good thing, as they increase the lifespan of products created from them, and reduce the need for maintenance. Biorenewable polymers are also pretty likable, as they reduce or even eliminate the need for petroleum products in plastic production, replacing them with plant-derived substances. Michael Kessler, an Iowa State University associate professor of materials science and engineering, and an associate of the U.S. Department of Energy’s Ames Laboratory, is now attempting to combine the two.

Self-healing materials generally incorporate microcapsules containing a liquid healing agent, and catalyst elements, which are embedded within the material’s matrix. As cracks form within the matrix, the microcapsules rupture, releasing the healing agent. As soon as that agent encounters the catalyst, it hardens into three-dimensional polymer chains, thus filling and securing the cracks. Such technology has been used not only to create self-healing plastics, but also self-healing concrete.

Since 2005, Kessler has been working with Iowa State’s Prof. Richard Larock on the development of biorenewable polymers made from vegetable oils. Larock is the inventor of a process wherein bioplastics can be created that consist of 40 to 80 percent inexpensive natural oils – these plastics reportedly have very good thermal and mechanical properties, are good at dampening noises and vibrations, and are also very good at returning to their original shape when heated.

Kessler is now trying to create self-healing versions of these same plastics.

One thing he has deduced so far is that a healing agent for a tung oil-based polymer works too fast. Kessler and his colleagues are now working on slowing down the reactive process of that agent, while also developing biopolymer-friendly encapsulating techniques, and bio-based healing agents.

The big challenge, he says, is to match the 90 percent healing efficiency of standard synthetic composites.

Sourced & published by Henry Sapiecha

Dec 7 – It is only one atom thick, but according to the Nobel prize winning scientists who discovered it, flourographene could soon be making a big impact. Stuart McDill reports.

View video here

Nanoscale Gold Coatings Developed

Researchers at Rensselaer have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. As seen in the research image, drops of gold-infused toluene applied to a surface evaporate within a few minutes and leave behind a uniform layer of nanoscale gold. The process requires no sophisticated equipment, works on nearly any surface, takes only 10 minutes, and could have important implications for nanoelectronics and semiconductor manufacturing. (Credit: Image courtesy of Rensselaer Polytechnic Institute)

Gold plated porche.Munich show.

Science (June 21, 2010) — Researchers at Rensselaer Polytechnic Institute have developed a new, ultra-simple method for making layers of gold that measure only billionths of a meter thick. The process, which requires no sophisticated equipment and works on nearly any surface including silicon wafers, could have important implications for nanoelectronics and semiconductor manufacturing.

Sang-Kee Eah, assistant professor in the Department of Physics, Applied Physics, and Astronomy at Rensselaer, and graduate student Matthew N. Martin infused liquid toluene — a common industrial solvent — with gold nanoparticles. The nanoparticles form a flat, closely packed layer of gold on the surface of the liquid where it meets air. By putting a droplet of this gold-infused liquid on a surface, and waiting for the toluene to evaporate, the researchers were able to successfully coat many different surfaces — including a 3-inch silicon wafer — with a monolayer of gold nanoparticles.

“There has been tremendous progress in recent years in the chemical syntheses of colloidal nanoparticles. However, fabricating a monolayer film of nanoparticles that is spatially uniform at all length scales — from nanometers to millimeters — still proves to be quite a challenge,” Eah said. “We hope our new ultra-simple method for creating monolayers will inspire the imagination of other scientists and engineers for ever-widening applications of gold nanoparticles.”

Results of the study, titled “Charged gold nanoparticles in non-polar solvents: 10-min synthesis and 2-D self-assembly,” were published recently in the journal Langmuir.

Whereas other synthesis methods take several hours, this new method chemically synthesizes gold nanoparticles in only 10 minutes without the need for any post-synthesis cleaning, Eah said. In addition, gold nanoparticles created this way have the special property of being charged on non-polar solvents for 2-D self-assembly.

Previously, the 2-D self-assembly of gold nanoparticles in a toluene droplet was reported with excess ligands, which slows down and complicates the self-assembly process. This required the non-volatile excess ligands to be removed in a vacuum. In contrast, Eah’s new method ensures that gold nanoparticles float to the surface of the toluene drop in less than one second, without the need for a vacuum. It then takes only a few minutes for the toluene droplet to evaporate and leave behind the gold monoloayer.

“The extension of this droplet 2-D self-assembly method to other kinds of nanoparticles, such as magnetic and semiconducting particles, is challenging but holds much potential,” Eah said. “Monolayer films of magnetic nanoparticles, for instance, are important for magnetic data storage applications. Our new method may be able to help inform new and exciting applications.”

Co-authors on the paper are former Rensselaer undergraduate researchers James I. Basham ’07, who is now a graduate student at Pennsylvania State University, and Paul Chando ’09, who will begin graduate study in the fall at the City College of New York.

The research project was supported by Rensselaer, the Rensselaer Summer Undergraduate Research Program, the National Science Foundation (NSF) Research Experiences for Undergraduates, and the NSF’s East Asia and Pacific Summer Institutes and Japan Society for the Promotion of Science.

Watch a video demonstration of this new fabrication process at: http://www.youtube.com/watch?v=nqkwM9o1s-w

Sourced & published by Henry Sapiecha

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