Friday, November 25, 2011

Ionized plasmas as cheap sterilizers for developing world

University of California, Berkeley, scientists have shown that ionized plasmas like those in neon lights and plasma TVs not only can sterilize water, but make it antimicrobial -- able to kill bacteria -- for as long as a week after treatment.

Devices able to produce such plasmas are cheap, which means they could be life-savers in developing countries, disaster areas or on the battlefield where sterile water for medical use -- whether delivering babies or major surgery -- is in short supply and expensive to produce.

"We know plasmas will kill bacteria in water, but there are so many other possible applications, such as sterilizing medical instruments or enhancing wound healing," said chemical engineer David Graves, the Lam Research Distinguished Professor in Semiconductor Processing at UC Berkeley. "We could come up with a device to use in the home or in remote areas to replace bleach or surgical antibiotics."

Low-temperature plasmas as disinfectants are "an extraordinary innovation with tremendous potential to improve health treatments in developing and disaster-stricken regions," said Phillip Denny, chief administrative officer of UC Berkeley's Blum Center for Developing Economies, which helped fund Graves' research and has a mission of addressing the needs of the poor worldwide.

"One of the most difficult problems associated with medical facilities in low-resource countries is infection control," added Graves. "It is estimated that infections in these countries are a factor of three-to-five times more widespread than in the developed world."

Graves and his UC Berkeley colleagues published a paper in the November issue of the Journal of Physics D: Applied Physics, reporting that water treated with plasma killed essentially all the E. coli bacteria dumped in within a few hours of treatment and still killed 99.9 percent of bacteria added after it sat for seven days. Mutant strains of E. coli have caused outbreaks of intestinal upset and even death when they have contaminated meat, cheese and vegetables.

Based on other experiments, Graves and colleagues at the University of Maryland in College Park reported Oct. 31 at the annual meeting of the American Vacuum Society that plasma can also "kill" dangerous proteins and lipids -- including prions, the infectious agents that cause mad cow disease -- that standard sterilization processes leave behind.

In 2009, one of Graves' collaborators from the Max Planck Institute for Extraterrestrial Physics built a device capable of safely disinfecting human skin within seconds, killing even drug-resistant bacteria.

"The field of low-temperature plasmas is booming, and this is not just hype. It's real!" Graves said.

In the study published this month, Graves and his UC Berkeley colleagues showed that plasmas generated by brief sparks in air next to a container of water turned the water about as acidic as vinegar and created a cocktail of highly reactive, ionized molecules -- molecules that have lost one or more electrons and thus are eager to react with other molecules. They identified the reactive molecules as hydrogen peroxide and various nitrates and nitrites, all well-known antimicrobials. Nitrates and nitrites have been used for millennia to cure meat, for example.

Graves was puzzled to see, however, that the water was still antimicrobial a week later, even though the peroxide and nitrite concentrations had dropped to nil. This indicated that some other reactive chemical -- perhaps a nitrate -- remained in the water to kill microbes, he said.

Plasma discharges have been used since the late 1800s to generate ozone for water purification, and some hospitals use low-pressure plasmas to generate hydrogen peroxide to decontaminate surgical instruments. Plasma devices also are used as surgical instruments to remove tissue or coagulate blood. Only recently, however, have low-temperature plasmas been used as disinfectants and for direct medical therapy, said Graves, who recently focused on medical applications of plasmas after working for more than 20 years on low-temperature plasmas of the kind used to etch semiconductors.

"I'm a chemical engineer who applies physics and chemistry to understanding plasmas," Graves said. "It's exciting to now look for ways to apply plasmas in medicine."

Graves' UC Berkeley coauthors are former post-doctoral fellow Matthew J. Traylor; graduate students Matthew J. Pavlovich and Sharmin Karim; undergraduate Pritha Hait; research associate Yukinori Sakiyama; and chemical engineer Douglas S. Clark, The Warren and Katharine Schlinger Distinguished Professor in Chemical Engineering and the chair of the Department of Chemical and Biomolecular Engineering.

The work on deactivating dangerous and persistent biological molecules was conducted with a group led by Gottlieb Oehrlein, a professor of materials science and engineering at the University of Maryland in College Park.

The research is supported by the U.S. Department of Energy's Office of Fusion Science Plasma Science Center, the UC Berkeley Blum Center for Developing Economies, and the UC Berkeley Sustainable Products and Solution Program.

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The above story is reprinted from materials provided by University of California - Berkeley. The original article was written by Robert Sanders, Media Relations.

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Journal Reference:

Matthew J Traylor, Matthew J Pavlovich, Sharmin Karim, Pritha Hait, Yukinori Sakiyama, Douglas S Clark, David B Graves. Long-term antibacterial efficacy of air plasma-activated water. Journal of Physics D: Applied Physics, 2011; 44 (47): 472001 DOI: 10.1088/0022-3727/44/47/472001

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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Engineers solve energy puzzle: How energy levels align in a critical group of advanced materials

 University of Toronto materials science and engineering (MSE) researchers have demonstrated for the first time the key mechanism behind how energy levels align in a critical group of advanced materials. This discovery is a significant breakthrough in the development of sustainable technologies such as dye-sensitized solar cells and organic light-emitting diodes (OLEDs).

Transition metal oxides, which are best-known for their application as super-conductors, have made possible many sustainable technologies developed over the last two decades, including organic photovoltaics and organic light-emitting diodes. While it is known that these materials make excellent electrical contacts in organic-based devices, it wasn't known why -- until now.

In research published in Nature Materials, MSE PhD Candidate Mark T. Greiner and Professor Zheng-Hong Lu, Canada Research Chair (Tier I) in Organic Optoelectronics, lay out the blueprint that conclusively establishes the principle of energy alignment at the interface between transition metal oxides and organic molecules.

"The energy-level of molecules on materials surfaces is like a massive jigsaw puzzle that has challenged the scientific community for a very long time," says Professor Lu. "There have been a number of suggested theories with many critical links missing. We have been fortunate to successfully build these links to finally solve this decades-old puzzle."

With this piece of the puzzle solved, this discovery could enable scientists and engineers to design simpler and more efficient organic solar cells and OLEDs to further enhance sustainable technologies and help secure our energy future.

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The above story is reprinted from materials provided by University of Toronto Faculty of Applied Science & Engineering.

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Journal Reference:

Mark T. Greiner, Michael G. Helander, Wing-Man Tang, Zhi-Bin Wang, Jacky Qiu, Zheng-Hong Lu. Universal energy-level alignment of molecules on metal oxides. Nature Materials, 2011; DOI: 10.1038/nmat3159

Robot speeds up glass development

Model by model, the electronics in a car are being moved closer to the engine block. This is why the materials used for the electronics must resist increasing heat -- so the glass solder being used as glue must be continually optimized. For the first time ever, a robot takes on the task of developing new types of glass and examining their characteristics. Researchers will introduce this robot at the "productronica" trade fair to be held in Munich, Germany, from November 15 -- 18, 2011.

For laymen glas looks like glass -- it might be a window, a drinking vessel, a lense for an automotive headlight. But there is much more in and to the transparent material: glass can consist of 50 to 60 different elements. Experts are constantly being asked to create glass with certain characteristics out of these elements, since new applications require new materials quite often. Let's take the car as an example: the electronic components in a car's engine compartment are being brought ever closer to the engine and so must increasingly be resistant to heat and corrosive gasses. This also applies to the glue, a glass solder. In the development of fuel cells, the demand for new types of glass is also great: the use of new metals requires that the glass solder also be adapted. In addition, over a period of approximately 100,000 hours, the glass must withstand thermal heat of 900 degrees Celsius without being damaged.

In order to develop glass with new characteristics, experts select about ten compounds from potential elements, mix them and then heat the powder. They heat it in a furnace until it is soft, then they pour it into a mould and let it cool slowly and in a controlled fashion, down to room temperature. During that process small samples from the viscous glass are taken to test it: how viscous is it? How well does it wet metals? How does it crystallize out? To produce the glass samples by hand and to test them requires a lot of time: one employee needs approximately two weeks to process 16 samples.

Researchers of the Fraunhofer Institute for Silicate Research ISC in Würzburg have developed a unit that carries out all these steps automatically. "It needs only 24 hours to process 16 samples," says Dr. Martin Kilo, manager of the expert group for glass and high-temperature materials at the ISC. "For this reason we are able to develop glass elements more cost-effectively than previously, by up to 50 percent." The core piece of the unit is a robot: it puts a mixing cup on a scale and moves it under 14 storage vessels, from which a certain amount of powder is filled into the cup. Then the robot mixes the individual ingredients by closing the cup and shaking it, just like a bartender does with a cocktail shaker. The robot arm then grabs a crucible, puts it onto the scale, fills it with a certain amount of the mixed powder and puts the crucible into one of the five furnaces available in total. The robot repeats this steps several times, since gases build up when the powder is heated and foam could form otherwise. In addition, the powder shrinks during the melting process. Finally the furnace heats the fully filled crucible to a higher temperature, causing the gas bubbles in the glass to rise to the surface. Once the glass is viscous, the robot arm removes the crucible, pours the glass into a new mould and places it in a stress-relieving furnace. Here, the glass cools slowly and in a controlled manner, from 600 to 800 degrees Celsius down to room temperature.

An additional central element of the unit is the analysis unit. It works according to the thermo-optical measurement principle. Looking through two measurement windows, the shade the sample projects in a backlight test system is recorded by a CCD camera. The changes in the contour make it possible to determine characteristics such as sample volume, hemisphere point and wetting angle. This test unit measures how viscous the melt is, and if and how it crystallizes and wets metals. The test unit can also be used independently of the glass screening unit. The unit also determines and records the ability of the glass to conduct heat.

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The above story is reprinted from materials provided by Fraunhofer-Gesellschaft.

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Flexible rack systems sort molecules

Researchers of Karlsruhe Institute of Technology (KIT) and Ruhr-Universität Bochum (RUB) have developed a flexible and efficient new process for the separation of enantiomers. Enantiomer separation is indispensable for the production of many pharmaceuticals. In their process, the scientists use porous molecular frameworks (MOFs) that are assembled in layers on solid substrates using a specifically developed method.

The results have now been published in the journal Angewandte Chemie.

Enantiomers are pairs of molecules built in a mirror-inverted manner. They differ from each other like a left and a right glove. This property of the molecules that is referred to as chirality is of particular relevance to biosciences and pharmaceutics. "While many, especially smaller, molecules like carbon dioxide or methane are not chiral, many biologically relevant molecules, such as tartaric acid have this property," explains Professor Christof Wöll, Head of the KIT Institute of Functional Interfaces (IFG). For many pharmaceutical agents, only one of both enantiomers is desired for the effective molecules being able to dock to certain structures in the body.

In contrast to conventional methods, the process developed by the team of researchers directed by Professor Wöll, Professor Roland Fischer from the Chair for Inorganic Chemistry II of RUB, and Humboldt scholar Bo Liu (KIT and RUB) allows for a more rapid and, hence, cheaper separation of enantiomers. It is based on novel molecular frameworks (MOFs) that can be grown on solid substrates. These porous coatings that are also referred to as SURMOFs are produced by an epitaxy process specifically developed by the researchers. Instead of heating the solution mixtures produced from the initial substances, modified substrates are immersed alternately in the solutions of the initial substances. "In this way, the molecular layers are assembled one after the other comparable to a rack system," explains Roland Fischer. These molecular rack systems anchored to the surfaces can be functionalized for various applications.

The enantiomers are separated by chiral organic molecules that are the linkers or struts of the rack systems. Thanks to their enantiopure structure, these coatings retain one of both enantiomers. In their contribution that was also selected for the title photo of the journal "Angewandte Chemie," the scientists describe the separation of the enantiomer molecules (2R, 5R)-2,5-hexanediol (R-HDO) and (2S, 5S)-2,5-hexanediol (S-HDO). Future work will be aimed at increasing the mesh width of the porous structures in order to test the method for larger molecules used as pharmaceuticals. "Pharmaceutical substances are two or more nanometers in size and, hence, larger than hexanediol. The development of surface-attached networks with such large structures is a big challenge," explains Professor Wöll.

It is a particular advantage of SURMOFs that the efficiency of enantiomer separation can be measured rapidly and precisely. With the help of quartz crystal microbalances, it was demonstrated that surface-anchored molecular framework structures reach excellent separation efficiencies already. "The SURMOFs as a new material have an enormous potential for use in pharmaceutical industry," explains Professor Jürgen Hubbuch, holder of the Chair for Molecular Separation Engineering (MAB) and Spokesman of the KIT Competence Field of Biotechnology.

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The above story is reprinted from materials provided by Helmholtz Association of German Research Centres.

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Journal Reference:

Bo Liu, Osama Shekhah, Hasan K. Arslan, Jinxuan Liu, Christof Wöll, Roland A. Fischer. Homochirale Dünnschichten auf der Basis Metall-organischer Gerüste: orientiertes Wachstum von SURMOFs und enantioselektive Adsorption. Angewandte Chemie, 2011; DOI: 10.1002/ange.201104240

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