Thursday, January 19, 2012

Clariant is named Pigment Supplier of the Year by Sitivesp

Sitivesp, the Union of Paints & Coatings producers of the State of Sao Paulo, has named Clariant “Supplier of the Year” in the Pigment category of its annual award scheme. This is the 17th time, in the 20 year history of the award, that Clariant has been chosen as the best Pigment supplier.

Promoted by the Union's Raw Materials Department, the Sitivesp Supplier of the Year Award highlights the work done by companies that promote continuous improvements in the products and services offered to the paint and coatings market. “Clariant continuously invests in research and innovation, in the improvement of its processes and the development of environmentally friendly products, with the objective of providing clients with the optimum solutions for their needs. This recognition proves that we are on the right path, from the stand point of quality and customer service,” states Pieter Hermens, Clariant’s Head of Business Unit Pigments to Latin America.

The selection process included votes from all Sitivesp associated companies. In all there are 75 companies, which together make up 70% of the Brazilian paint and coatings market. In the secret and voluntary vote, the members took into consideration factors such as relationship between company and supplier, pre- and post-sale service quality, timely delivery, commercial policy, process, product quality and technological innovation.

For Clariant, the award is even more significant because it is based on Top of Mind Awareness (TOMA), in which Sitivesp members freely name the best companies in different categories. “The Clariant team includes experienced professionals who have been serving the paint market for many years, which contributes to our deep understanding of client needs, and strengthens our relationships and partnerships," states Luis Carlos Peres, Pigment Sales Coordinator at Clariant.

Charges going astray: New transfer paths for electrons discovered

 In the development of materials for energy production and distribution, knowledge of molecular processes in electrical charge transfer is fundamental. Research groups of Prof. Dr. Stefan Weber and Prof. Dr. Thorsten Koslowski at the Institute for Physical Chemistry of the Albert-Ludwigs-University Freiburg once more discovered that nature provides interesting templates for long-range electron transfer.

They recently published their results in the  journal Angewandte Chemie International Edition. In collaboration with Dr. Kenichi Hitomi and Prof. Dr. Elizabeth D. Getzoff of Scripps Research Institute in La Jolla/USA the physico chemists studied proteins from the photolyase/cryptochrome family. These proteins perform a range of different tasks although their topologies are very similar.

All members of the protein family share a cascade of three amino acids that forms a pathway from the protein surface to its core, along which electrons can "hop." When studying cyanobacterial cryptochrome using time-resolved electron paramagnetic resonance, the charge carriers, however, did not follow the usual electron channel despite the presence of the amino acid cascade known from the other members of the family. Instead, the cascade was used only partially, eventually branching to a neighboring amino acid, even though the electrons had to then cover a much longer distance.

With the help of theoretical analyses the scientists were able to describe and thereby understand the protein's unexpected behavior: The orientation of the amino acids has a stronger influence on electron-transfer efficiency than previously expected, and a more favorable stacking of the amino acid "stepping stones" can compensate for the longer distance. Hence, evident structural similarity does not necessarily lead to identical behavior. To "understand" the protein, one clearly needs to look closer.

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The above story is reprinted from materials provided by Albert-Ludwigs-Universit├Ąt Freiburg, via AlphaGalileo.

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Journal Reference:

Till Biskup, Kenichi Hitomi, Elizabeth D. Getzoff, Sebastian Krapf, Thorsten Koslowski, Erik Schleicher, Stefan Weber. Unexpected Electron Transfer in Cryptochrome Identified by Time-Resolved EPR Spectroscopy. Angewandte Chemie International Edition, 2011; 50 (52): 12647 DOI: 10.1002/anie.201104321

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Graphene quantum dots: The next big small thing

 A Rice University laboratory has found a way to turn common carbon fiber into graphene quantum dots, tiny specks of matter with properties expected to prove useful in electronic, optical and biomedical applications.

The Rice lab of materials scientist Pulickel Ajayan, in collaboration with colleagues in China, India, Japan and the Texas Medical Center, discovered a one-step chemical process that is markedly simpler than established techniques for making graphene quantum dots. The results were published online this month in the American Chemical Society's journal Nano Letters.

"There have been several attempts to make graphene-based quantum dots with specific electronic and luminescent properties using chemical breakdown or e-beam lithography of graphene layers," said Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor of Mechanical Engineering and Materials Science and of chemistry. "We thought that as these nanodomains of graphitized carbons already exist in carbon fibers, which are cheap and plenty, why not use them as the precursor?"

Quantum dots, discovered in the 1980s, are semiconductors that contain a size- and shape-dependent band gap. These have been promising structures for applications that range from computers, LEDs, solar cells and lasers to medical imaging devices. The sub-5 nanometer carbon-based quantum dots produced in bulk through the wet chemical process discovered at Rice are highly soluble, and their size can be controlled via the temperature at which they're created.

The Rice researchers were attempting another experiment when they came across the technique. "We tried to selectively oxidize carbon fiber, and we found that was really hard," said Wei Gao, a Rice graduate student who worked on the project with lead author Juan Peng, a visiting student from Nanjing University who studied in Ajayan's lab last year. "We ended up with a solution and decided to look at a few drops with a transmission electron microscope."

The specks they saw were bits of graphene or, more precisely, oxidized nanodomains of graphene extracted via chemical treatment of carbon fiber. "That was a complete surprise," Gao said. "We call them quantum dots, but they're two-dimensional, so what we really have here are graphene quantum discs." Gao said other techniques are expensive and take weeks to make small batches of graphene quantum dots. "Our starting material is cheap, commercially available carbon fiber. In a one-step treatment, we get a large amount of quantum dots. I think that's the biggest advantage of our work," she said.

Further experimentation revealed interesting bits of information: The size of the dots, and thus their photoluminescent properties, could be controlled through processing at relatively low temperatures, from 80 to 120 degrees Celsius. "At 120, 100 and 80 degrees, we got blue, green and yellow luminescing dots," she said.

They also found the dots' edges tended to prefer the form known as zigzag. The edge of a sheet of graphene -- the single-atom-thick form of carbon -- determines its electrical characteristics, and zigzags are semiconducting.

Their luminescent properties give graphene quantum dots potential for imaging, protein analysis, cell tracking and other biomedical applications, Gao said. Tests at Houston's MD Anderson Cancer Center and Baylor College of Medicine on two human breast cancer lines showed the dots easily found their way into the cytoplasm and did not interfere with the cells' proliferation.

"The green quantum dots yielded a very good image," said co-author Rebeca Romero Aburto, a graduate student in the Ajayan lab who also studies at MD Anderson. "The advantage of graphene dots over fluorophores is that their fluorescence is more stable and they don't photobleach. They don't lose their fluorescence as easily. They have a depth limit, so they may be good for in vitro and in vivo (small animal) studies, but perhaps not optimal for deep tissues in humans.

"But everything has to start in the lab, and these could be an interesting approach to further explore for bioimaging," Romero Alburto said. "In the future, these graphene quantum dots could have high impact because they can be conjugated with other entities for sensing applications, too."

Co-authors include Angel Marti, aprofessor of chemistry and bioengineering, postdoctoral research associates Zheng Liu and Liehui Ge, senior research scientist Lawrence Alemany and graduate student Xiaobo Zhan, all of Rice; Rice alumnus Li Song of Shinshu University, Japan; Bipin Kumar Gupta of the National Physical Laboratory, New Delhi, who worked at the Ajayan lab on an Indo-US Science and Technology Forum fellowship; Guanhui Gao of the Ocean University of China; research technician Sajna Antony Vithayathil of Baylor College of Medicine; Benny Abraham Kaipparettu, a postdoctoral researcher at Baylor College of Medicine; Takuya Hayashi, an associate professor of engineering at Shinshu University, Japan; and Jun-Jie Zhu, a professor of chemistry at Nanjing University.

The research was supported by Nanoholdings, the Office of Naval Research MURI program on graphene, the Natural Science Foundation of China, the National Basic Research Program of China, the Indo-US Science and Technology Forum and the Welch Foundation.

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The above story is reprinted from materials provided by Rice University.

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Journal Reference:

Juan Peng, Wei Gao, Bipin Kumar Gupta, Zheng Liu, Rebeca Romero-Aburto, Liehui Ge, Li Song, Lawrence B. Alemany, Xiaobo Zhan, Guanhui Gao, Sajna Antony Vithayathil, Benny Abraham Kaipparettu, Angel A. Marti, Takuya Hayashi, Jun-Jie Zhu, Pulickel M. Ajayan. Graphene Quantum Dots Derived from Carbon Fibers. Nano Letters, 2012; : 120106121847009 DOI: 10.1021/nl2038979

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Novel chemical route to form organic molecules

An international team of scientists led by University of Hawai'i at Manoa Professor Ralf I. Kaiser, Alexander M. Mebel of Florida International University, and Alexander Tielens of Leiden Observatory in the Netherlands, discovered a novel chemical route to form polycyclic aromatic hydrocarbons (PAHs) -- complex organic molecules such as naphthalene carrying fused benzene rings -- in ultra-cold regions of interstellar space.

The team announced their findings in the January 3 issue of Proceedings of the National Academy of Sciences. Funding for the study was provided by the U.S. Department of Energy, Basic Energy Sciences.

These findings have crucial implications not only to reduce the emission of PAHs as toxic byproducts from internal combustion engines, but also rationalize the synthetic routes to a key class of organic molecules in the interstellar medium associated with the origins of life.

On Earth, PAHs are as­so­­ci­ated with in­­­com­­­­­­plete com­bus­tion processes and can be formed readily at elevated temperatures in combustion engines of cars and in cigarette smoke. Once liberated into the am­bient environ­ment, PAHs can be transferred into the lungs by inhalation and are strong­­­­ly implicated in the de­gra­da­tion of hu­man health, particularly due to their high carcino­ge­nic risk po­­ten­­tial. PAHs are also se­rious water pollutants of marine ecosystems and bioaccumulate in the fat­ty tis­­­­sue of living or­ga­nisms. Together with leafy ve­ge­tables, where PAHs de­po­­sit easily, they have been further link­ed to soil contamination, food poisoning, liver lesions, and tu­mor gro­wth.

Whereas on Earth, PAHs are classified as highly toxic, PAHs have been dubbed as the 'cradle of life' in the interstellar medium and are considered as key players in the astrobiological evolution. On the molecular level, functionalized PAHs carrying carbonyl and hydroxyl groups were found in organic extracts from the Murchison meteorite and form membrane-like boundary structures, the first in­dica­tions of a cell type structure, which are requisite to the origin of life. The compounds that are water soluble form non-soluble vesicles, constituting molecules that possess both polar and non-polar components. The hollow droplets formed by this lipid multilayer are essential for the origin of life process since they provide an environment in which the functionalized PAHs can evolve by isolating and protecting them from the surrounding medium.

Scientists have been researching the formation of PAHs in combustion flames and in the interstellar medium for decades, but the formation mechanism of even the simplest PAH pro­to­type -- the naphthalene molecule (C10H8) as present in earthly mothballs -- has remained an open question. Textbook knowledge postulates that classical reaction mechanisms involve complex reactions following hydrogen abstraction and acetylene addition (HACA) sequences with substantial 'activation energies.' These processes can only operate at high temperatures of a few 1,000 K as present, for instance, in combustion processes and in the outflows of carbon-rich stars and planetary nebulae. However, in recent years it has become quite clear that interstellar PAHs are rapidly destroyed in the interstellar medium upon photolysis, interstellar shock waves driven by supernova explosions, and energetic cosmic rays. The destruction time scales are much shor­ter than the timescale for injection of new material into the interstellar medium by carbon-rich Asymptotic Giant Branch (AGB) stars and carbon-rich planetary nebulae as the descendants of AGB stars. Therefore, the ubiquitous presence of PAHs in the interstellar medium implies a cru­cial, previously unexplained route to a fast chemical growth of PAHs in the cold environment of the in­­terstellar medium at temperatures down to 10 K, where the classical HACA reaction mechanism cannot function, since entrance barriers (classical 'activation energies') cannot be overcome.

To unravel the formation of naphthalene as the simplest representative of PAHs, University of Hawai‘i at Manoa chemists Dorian S.N. Parker, Fangtong Zhang, Seol Kim, and Ralf I. Kaiser conducted gas phase crossed molecular beam experiments in their laboratory and presented that naphthalene can be formed as a consequence of a single collision event via a barrier-less and exoergic reaction between the phenyl radical and vinylacetylene invol­ving a van-der-Waals complex and submerged barrier in the entrance channel. Angular resolved mass spectrometer measurements of the reaction products together with isotopic labeling confirmed that naphthalene plus a single hydrogen atom, were produced. To support the derived mechanism involved in the formation of naphthalene, theoretical chemists at Florida International University (Alex Landera, Vadim V. Kislov, Alexander Mebel), merged the experimental results with theoretical computations. Theoretical computations also provide the three-dimensional distribution of electrons in atoms and thus the overall energy level of a molecule. Mebel's computations showed that naphthalene is formed from the reaction of a single phenyl radical colliding with vinylacetylene. Most importantly, since the temperatures of cold molecular clouds are very low (10 K), the computations indicate that the reaction has no entrance barrier ('activation energy').

"These findings chal­len­ge conventional wisdom that PAH-formation only occurs at high tem­pe­ra­tures such as in combustion systems and implies that low tem­pe­ra­tu­re chemistry can initiate the synthesis of the very first PAH in the interstellar medium," said co-author Tielens.

In the future, the team plans to expand these studies to unravel the formation routes to more complex PAHs like phenan­thre­ne and anthracene, and also to nitrogen-substituted PAHs such as indole and quinoline. This concept can be also expanded to functionalized PAHs with organic side chains thus bringing researchers closer to solving the decade old puzzle of how complex PAHs and their derivatives can be synthesized in combustion flames and in cold interstellar space.

Story Source:

The above story is reprinted from materials provided by University of Hawaii at Manoa.

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

Journal Reference:

D. S. N. Parker, F. Zhang, Y. S. Kim, R. I. Kaiser, A. Landera, V. V. Kislov, A. M. Mebel, A. G. G. M. Tielens. Low temperature formation of naphthalene and its role in the synthesis of PAHs (Polycyclic Aromatic Hydrocarbons) in the interstellar medium. Proceedings of the National Academy of Sciences, 2011; 109 (1): 53 DOI: 10.1073/pnas.1113827108

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Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.