Sunday, January 29, 2012

Flaky graphene makes reliable chemical sensors

Scientists from the University of Illinois at Urbana-Champaign and the company Dioxide Materials have demonstrated that randomly stacked graphene flakes can make an effective chemical sensor.

The researchers created the one-atom-thick carbon lattice flakes by placing bulk graphite in a solution and bombarding it with ultrasonic waves that broke off thin sheets. The researchers then filtered the solution to produce a graphene film, composed of a haphazard arrangement of stacked flakes, that they used as the top layer of a chemical sensor. When the graphene was exposed to test chemicals that altered the surface chemistry of the film, the subsequent movement of electrons through the film produced an electrical signal that flagged the presence of the chemical.

The researchers experimented by adjusting the volume of the filtered solution to make thicker or thinner films. They found that thin films of randomly stacked graphene could more reliably detect trace amounts of test chemicals than previously designed sensors made from carbon nanotubes or graphene crystals.

The results are accepted for publication in the AIP's journal Applied Physics Letters.

The researchers theorize that the improved sensitivity is due to the fact that defects in the carbon-lattice structure near the edge of the graphene flakes allow electrons to easily "hop" through the film.

Story Source:

The above story is reprinted from materials provided by American Institute of Physics.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Amin Salehi-Khojin, David Estrada, Kevin Y. Lin, Ke Ran, Richard T. Haasch, Jian-Min Zuo, Eric Pop, Richard I. Masel. Chemical sensors based on randomly stacked graphene flakes. Applied Physics Letters, 2012; 100 (3): 033111 DOI: 10.1063/1.3676276

Products of biotechnological origin using vegetable and fruit by-products generated by the industry

Through the TRANSBIO project, Tecnalia will be implementing biotechnological solutions, like fermention and enzymatic processes to obtain new, high-value products of biotechnological origin in the form of new materials offering the potential to replace current plastics, foodstuffs and enzymes for applications in detergents using the materials not taken advantage of in the fruit and vegetable processing industry. This way, the global sustainability of the and processing industry will be improved, and the competitiveness of the European will be enhanced through new applications.

As a result of these processes, new and more sustainable will be obtained to be used in application, enzymes for producing detergents, and other biotechnological products for application in foodstuff.

In parallel, and in order to achieve the total use of the by-products employed in the project, those that may not be suited for use in biotechnological processes and the coming from fermentation processes will be tested to assess their use as raw material for the production of biogas.

The consortium participating in the TRANSBIO project comprises various partners from the ambit of industry and the academic sector with experience in complementary fields. The combination of these synergies allows all the links in the value chain to be taken into consideration, from the reprocessing of by-products, fermentation, and right up to the processing of the final product.

Tecnalia is coordinating this international consortium that has 16 partners from nine countries and two continents (Latin America and Europe) to look into the potential of new biotechnological solutions for obtaining bioproducts that, in practice, will signify the cutting of the environmental impact of food-producing activities.

Provided by Elhuyar Fundazioa

Active compounds against Alzheimer's disease

Researchers recently identified a series of synthetic compounds (inhibitors) that interfere with the self-assembly of the amyloid in vitro; they influence both early stages and the transition to the characteristic amyloid fibrils. On a theoretical level, these compounds thus satisfy an initial condition for the development of an Alzheimer drug.

Peptide's disorder determines interaction

In order to understand the interactions between the amyloid beta peptide and active compounds at a structural level, Marino Convertino, Andreas Vitalis, and Amedeo Caflisch from the University of Zurich's Department of Biochemistry simulated these interactions on the computer. In doing so, they focused on a fragment of the peptide that is thought to control both interactions with inhibitors and progression of disease. Based on these simulations, the were able to identify a hierarchy of interaction patterns between the peptide and various active compounds. To their surprise, they discovered that the disordered structure of the peptide controls the interactions.

"The peptide's disorder and flexibility enable it to adapt to many basic structural frameworks," explains Andreas Vitalis. Often it is only subparts of the molecules that mediate interactions on the compound side. However, even minimal changes to a compound may induce measurable changes to the peptide-compound interactions. "Design of active compounds that influence the amyloid beta peptide structurally in a specific manner will only be possible with the aid of high-resolution methods that are limited to one or a few molecules," concludes Vitalis. In the next step, the researchers from the University of Zurich want to identify new classes of active substances with controllable properties that interact with the amyloid beta peptide.

More information: Journal of Biological Chemistry. October 3, 2011. doi: 10.1074/jbc.M111.285957

Provided by University of Zurich

Helping hydrogen move back home

"The hardest part is getting the back onto the storage material," said Dr. Tom Autrey, a chemist at PNNL who was involved with the study. "You can't just pump it back in. So, we needed to develop a chemical process where we can do it cost effectively."

It's all about cost and safety. Many processes developed in a laboratory can't be inexpensively and safely done when taken beyond the laboratory. Chemical hydrogen storage systems that could one day power cars and trucks can be recharged, but the devil is in the details. Current processes require molten sodium, which has safety concerns and cost issues at large scales. In early work, PNNL scientists demonstrated that rhodium complexes could be used, but rhodium is far too expensive. Their recent discovery shows that complexes of cobalt and nickel, abundant and inexpensive metals, could recharge an amine borane-based hydrogen storage system.

The researchers began by studying the underlying mechanics of the reactions. "We took a rational approach—mindful of the chemistry and how it impacts the refueling process," said PNNL chemist Dr. Michael Mock, who led the study.

"We can't just pressurize the spent fuel with hydrogen. You have to work with Mother Nature and use a chemical process to put the hydrogen back," said Autrey.

So, the team performed extensive electronic structure calculations using the NWChem software, previously developed in part at PNNL, to predict the reactivity of a large number of potential reaction schemes. "The calculations let us screen targets fast," said Dr. Don Camaioni, who led the theoretical portion of the research. "We quickly learned what influenced reactivity and what didn't."

With the properties determined, the researchers focused on the synthesis of a select number of cobalt and nickel complexes, benefiting from the use of resources in EMSL. They then analyzed the effectiveness of these complexes in activating hydrogen for transfer to targets molecules identified by computation. The experimental work confirmed that the cobalt and nickel complexes managed the job at reasonable temperatures and pressures.

"There is a lot of balancing required to match the energetics of all the different steps in the hydrogen refueling process," said Autrey. "This is a very good step forward."

This work is part broader of efforts at PNNL to answer the fundamental questions around molecular catalysis. For example, Mock is taking on a larger challenge in the Center for Molecular Electrocatalysis, a DOE Energy Frontier Research Center at PNNL. He will soon be solving fundamental questions around the complex multi-electron reduction that takes nitrogen gas to ammonia for fertilizer. Camaioni and Autrey are using the insight gained from these studies to investigate the potential of using non-metal complexes to catalytically activate hydrogen for energy storage applications.

More information: MT Mock, et al. 2011. "Synthesis and Hydride Transfer Reactions of Cobalt and Nickel Hydride Complexes to BX3 Compounds." Inorganic Chemistry 50(23): 11914-11928. DOI: 10.1021/ic200857x

Provided by Pacific Northwest National Laboratory (news : web)