Wednesday, February 1, 2012

Chemistry professor developing sustainable bioplastics

Chemistry Professor Eugene Chen and his co-workers have invented a platform of processes to convert small derived from nonedible to . The molecules can be transformed into different materials depending on the that is added to them. That catalyst can either be an organic compound or a metal-based compound.

Officials with CSU Ventures, the university’s technology transfer arm, are optimistic about the commercial potential of this work and have filed several provisional patent applications on Chen’s processes. Two related studies were published last year and this month, both in Angewandte Chemie International Edition.

“Each year, the U.S. alone manufactures almost 90 billion pounds of synthetic plastics derived predominantly from fossil fuels, which are not renewable,” Chen said. “There’s a great deal of concern to develop sustainable polymers or materials that can displace those petrochemical polymers. There’s huge interest in academia and industry, so the largest companies such as Dow Chemical, Dupont and BASF are pursuing sustainable chemical feedstocks to make materials.”

The organic process Chen created could be used to produce commodity plastics for everyday uses such as artificial glass, dental resins, automobile parts and furniture. His metal-based process would be used to produce high-performance engineering plastic materials that have superb mechanical and physical properties.

Chen has found in his laboratory that commercially available organic catalysts applied to small molecules derived from plant biomass are very active and efficient – the reaction achieves completion within a minute – and non-toxic. He also has developed a metal-based catalyst system that produces “stereoregular” polymers that exhibit superior physical and mechanical properties, meaning they’re very robust and more resistant to such factors as temperature, liquids, chemicals and scratches.

Plastic optical fibers, for example, must sustain exposure to the elements and still perform at a high level so they don’t interrupt telecommunications service.

“These materials require high resistance to extreme conditions including high temperature and unexpected environmental invasion,” Chen said.

Chen has done previous research showing that dissolving plant biomass in “green” solvent ionic liquids - salts that melt at low temperatures - converts more sugars needed for biofuel more quickly than traditional methods. The discovery was an important step in the move toward the use of nonedible plant biomass as an alternative source for fuel. Most recently, Chen’s lab has filed a provisional patent for a new catalytic process in ionic liquids to convert plant biomass to platform chemicals.

Chen joined Colorado State in 2000 from Dow Chemical where he researched production of petroleum-based polyolefin plastics. His current research has been supported by grants from the National Science Foundation and the U.S. Department of Energy.

Yuetao Zhang, a research scientist; Yangjian Hu, a postdoctoral fellow; and Garret Miyake, a graduate student, all work with Chen and contribute to the research.

Provided by Colorado State University

Scientists devise new imaging technique for analysis of biological samples

"The beauty of the technique is that it doesn't require any sample preparation," said Dr. Julia Laskin, who led the research project for PNNL's Imaging Initiative. "Here, you just take your sample, slice it, and put it in front of the instrument for analysis."

The technique, known as Nanospray Desorption Electrospray Iionization or nano-DESI, allows scientists to efficiently determine which molecules reside in a precise spot on a sample. With this information, researchers can learn more about how diverse , such as tissues and microbes,  respond to environmental factors. For example, biochemists can gain see how the marine microbe Shewanella oneidensis alter metals to remediate hazardous materials in the soil. For example, S. oneidensis can change very soluble hexavalent uranium to less soluble form, limiting its movement in groundwater. Another opportunity lies with medical researchers learning how nicotine and other toxins affect brain .

"Great discoveries often require great tools," said Dr. Louis Terminello, who leads the Chemical Imaging Initiative at PNNL. "The discoveries needed to solve today's problems aren't something that you're going to get by eyeballing a sample."

A pop quiz for cells

This sample shows an overlay of the optical and nano-DESI image of a human kidney tissue sample.

From the beginning, the team was convinced that the liquid bridge used in nano-DESI could be scaled down to analyze small areas on biological samples. By making adjustments, the team was able to scale the probe down to analyze an area about 10 micrometers in diameter, about the same size as a single red blood cell or mid-sized bacteria.

"With this probe, we are getting down to individual cells," said Laskin.

The team first analyzed rat brain tissues, which provide an outstanding test case for the technique, because they are very dense and yield high signals. The nano-DESI was able to draw up and analyze the molecules from different regions on the sample. Then, the team moved onto "airy" kidney tissues, and again were able to analyze micrometer-sized areas.

With each sample, the nanoDESI generated reams of mass spectra. Existing software packages could not process the data. The job fell to Brandi Heath, a team member who recently completed her bachelor's degree and is working on her master's degree at Washington State University. She read the charts and determined the fatty acids, amino acids, lipids, and other molecules that resided at different locations on the tissue.

"It was very tedious, but in the end, very rewarding," said Heath.

"Compared to other online liquid extraction techniques, nano-DESI has about an order of magnitude better spatial resolution," Laskin added. "It is comparable, spatially, to what laser-based techniques can give."

The team is working on two efforts related to their work with nanoDESI. First, they are working with Drs. Dongsheng Li and James Carson through the Initiative to understand and visualize the mass spectrometry data on the fly. Also, the team is working with Drs. Matthew Marshall, Margaret Romine, Grigoriy Pinchuk, and Jim Fredrickson to analyze different microbial communities of interest to the Department of Energy.

More information: Laskin J, et al. 2012. "Tissue Imaging Using Nanospray Desorption Electrospray Ionization Mass Spectrometry." Analytical Chemistry 84(1):141-148. DOI: 10.1021/ac2021322

Provided by Pacific Northwest National Laboratory (news : web)

Neutron scattering provides window into surface interactions

To better understand the fundamental behavior of molecules at surfaces, researchers at the U.S. Department of Energy's Oak Ridge National Laboratory are combining the powers of neutron scattering with chemical analysis.

Scientists have a fundamental interest in how molecules behave at solid surfaces because surface interactions influence chemistry, such as in materials for catalysis, drug delivery and carbon sequestration. Understanding these interactions allows researchers to tailor materials for a specific desirable outcome.

Michelle Kidder and A.C. Buchanan, physical organic chemists, and Ken Herwig, neutron scattering scientist, used neutron scattering to study the physical motion of a chemically attached organic molecule inside a silica nanopore, MCM41.

"There is a connection between a molecule's dynamic behavior or motion to its surroundings." Herwig said. "In particular, restricting the ability of a molecule to freely move by confining it to a small volume dramatically affects both the range and character of its movement. We are trying to gain insight into the connection between the changes in molecular motion and the changes in chemistry that occur when molecules are attached to a solid surface."

Herwig used neutron scattering to gain a unique perspective into molecular motion because neutrons are sensitive to the hydrogen atoms, which are present in many molecules that researchers are interested in. Additionally, neutron scattering simultaneously tells researchers how rapid the motion is and what type of motion they are observing on the atomic and nanoscale.

If scientists understand how pore size affects surface interactions, they can modify pore size to change a chemical product outcome.

To study surface interactions, Kidder synthesized both the organic molecules and MCM41 of different pore sizes, then chemically attached the molecules to the silica pore surface, which forms an organic-inorganic hybrid material. This hybrid material is used in studies to understand chemical decomposition pathways, where surface interactions were presumed to play a role.

"We are interested in understanding the thermo decomposition of molecules similar to those found in biomass resources," Kidder said. "What we have seen is that there are many local environmental factors that influence chemical reactivity and products, and one of those large influences occurs when a molecule is confined to a pore wall, where even the pore size has a large impact on reactivity."

This research was funded by DOE's Office of Science.

Story Source:

The above story is reprinted from materials provided by DOE/Oak Ridge National Laboratory.

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

Journal Reference:

Edward J. Kintzel, Michelle K. Kidder, A. C. Buchanan, Phillip F. Britt, Eugene Mamontov, Michaela Zamponi, Kenneth W. Herwig. Dynamics of 1,3-Diphenylpropane Tethered to the Interior Pore Surfaces of MCM-41. The Journal of Physical Chemistry C, 2012; 116 (1): 923 DOI: 10.1021/jp209458a

Transparency limits on transparent conducting oxides identified

 Researchers in the Computational Materials Group at the University of California, Santa Barbara (UCSB) have uncovered the fundamental limits on optical transparency in the class of materials known as transparent conducting oxides. Their discovery will support development of energy efficiency improvements for devices that depend on optoelectronic technology, such as light- emitting diodes and solar cells.

Transparent conducting oxides are used as transparent contacts in a wide range of optoelectronic devices, such as photovoltaic cells, light-emitting diodes (LEDs), and LCD touch screens. These materials are unique in that they can conduct electricity while being transparent to visible light. For optoelectronic devices to be able to emit or absorb light, it is important that the electrical contacts at the top of the device are optically transparent. Opaque metals and most transparent materials lack the balance between these two characteristics to be functional for use in such technology.

In a paper published in Applied Physics Letters, the UCSB researchers used cutting-edge calculation methods to investigate tin dioxide (SnO2), a widely-used conducting oxide.

Conducting oxides strike an ideal balance between transparency and conductivity because their wide band gaps prevent absorption of visible light by excitation of electrons across the gap, according to the researchers. At the same time, dopant atoms provide additional electrons in the conduction band that enable electrical conductivity. However, these free electrons can also absorb light by being excited to higher conduction-band states.

"Direct absorption of visible light cannot occur in these materials because the next available electron level is too high in energy. But we found that more complex absorption mechanisms, which also involve lattice vibrations, can be remarkably strong," says Hartwin Peelaers, a postdoctoral researcher and the lead author of the paper. The other authors are Emmanouil Kioupakis, now at the University of Michigan, and Chris Van de Walle, a professor in the UCSB Materials Department and head of the research group.

They found that tin dioxide only weakly absorbs visible light, thus letting most light pass through, so that it is still a useful transparent contact. In their study, the transparency of SnO2 declined when moving to other wavelength regions. Absorption was 5 times stronger for ultraviolet light and 20 times stronger for the infrared light used in telecommunications.

"Every bit of light that gets absorbed reduces the efficiency of a solar cell or LED," remarked Chris Van de Walle. "Understanding what causes the absorption is essential for engineering improved materials to be used in more efficient devices."

Story Source:

The above story is reprinted from materials provided by University of California - Santa Barbara.

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

Journal Reference:

H. Peelaers, E. Kioupakis, C. G. Van de Walle. Fundamental limits on optical transparency of transparent conducting oxides: Free-carrier absorption in SnO2. Applied Physics Letters, 2012; 100 (1): 011914 DOI: 10.1063/1.3671162