Spinning Quantum Dots reported in Nature Nanotechnology

Dr. Stefan Ochsenbein, a postdoc working with Prof. Daniel Gamelin, Harry and Catherine Jaynne Boand Endowed Professor of Chemistry, is lead author on a new paper published in Nature Nanotechnology reporting the first successful coherent impurity spin manipulation within colloidal semiconductor nanocrystals (also known as quantum dots). Spin effects in semiconductor nanostructures have attracted broad interest for potential spin-based information processing technologies, whether in spin-electronics (“spintronics”) or spin-photonics. Colloidal doped semiconductor nanocrystals present interesting possibilities for constructing devices by solution processing or that involve integration with soft materials (e.g., organics), but their spin properties remain relatively untested. For example, the possibility to manipulate spins within colloidal semiconductor nanocrystals coherently, as would be necessary for many proposed applications, had not been demonstrated until these latest experiments.

In this paper, Ochsenbein and Gamelin describe the first observation of coherent spin manipulation in colloidal doped quantum dots. The observation was made by demonstrating microwave-driven Rabi oscillations within the high-spin ground states of Mn2+ impurity ions doped into colloidal ZnO semiconductor nanocrystals. Their electron spin-echo measurements revealed long spin coherence times approaching 1 µs, sufficient for potential qubit applications with optical excitation. The authors also identified previously unobserved hyperfine interactions between Mn2+ electron spins within the quantum dots and proton nuclear spins outside the quantum dots, revealing an important but previously unrecognized contribution to spin decoherence in such quantum dots.

Read the article: “Quantum oscillations in magnetically doped colloidal nanocrystals.” Ochsenbein, S. T.; Gamelin, D. R., Nature Nanotechnology, 2011, 6, 112–115.

To learn more about Prof. Gamelin’s research, visit his faculty webpage and research group website.

Dalton research featured in C&E News coverstory

The research of Prof. Larry Dalton, B. Seymour Rabinovitch Endowed Chair in Chemistry, was recently featured as part of C&E News’ cover story highlighting the key research advances in chemistry over the last decade.  The article describes the advances the Dalton research group has made in designing devices that convert electrical data into optical information at high rates of speed (more than 110 gigahertz) under low drive voltages (less than 1 V). These types of devices have a wide variety of uses in fiber-optic and satellite communication systems and for optical-switching technology.

Read the C&E News article.

Visit Prof. Dalton’s department website and group research page.

Pradipsinh Rathod awarded Gates Foundation grant

Pradipsinh K. Rathod, Professor of Chemistry, was awarded a $ 1,000,000 grant from the Bill & Melinda Gates Foundation as part of the next phase of Grand Challenges Explorations, an initiative to encourage bold and unconventional ideas for global health. The grant will provide continued support for Prof. Rathod’s  global health research project “Strategies to Disable Hypermutagenesis in Malaria Parasites.”

Prof. Rathod proposed that drug resistance in malaria parasite populations is driven by cellular components, a “mutasome”, that promotes acquisition of multiple mutations at target loci in the genome.  All malaria parasites may have had an ancestral, pre-existing mechanism to mutate surface proteins at extraordinary rates to avoid host immunity. However, parasite populations displaying the Accelerated Resistance to Multiple Drugs (ARMD) phenotype may have hijacked such a machinery to now make changes anywhere in the genome. Genomic studies are geared to identify genome components which help drive hypermutagenesis, and high throughput screens are being developed to directly block the process with small organic molecules. An ability to chemically disable such a mutasome during malaria therapy would improve success rates and staying power of new antimalarial drugs.   Laboratory Post-Doctoral colleagues John White and Jenny Guler, and graduate student Joseph Fowble conduct  experimental design and implementation on the GCE project in the Rathod laboratory.

Grand Challenges Explorations is a five-year, $100 million initiative of the Gates Foundation to promote innovation in global health. For more information, visit  http://www.grandchallenges.org/explorations.

To learn more about Prof. Rathod’s research, visit his faculty page.

Pictured: Prof. Rathod and Dr. Jennifer Guler in the lab (photo by Mary Levin).

Electro-Optic Research featured on cover of Journal of Physical Chemistry B

Stephanie Benight, a 5th year graduate student working with Larry Dalton and Bruce Robinson, is lead author on a paper recently featured as the cover story in the Journal of Physical Chemistry B  (Sept. 23rd issue). Benight’s graduate research has been focused on investigating intermolecular interactions in electro-optic chromophore systems using experimental and theoretical methods. Organic electro-optic (EO) materials have the potential to minimize the size, weight, and power requirements of next generation computing, telecommunications, and sensing applications.

In this article, Benight and coworkers demonstrate both experimentally and theoretically that lattice dimensionality can be defined using the relationship between centrosymmetric order and acentric order. Experimentally: Acentric order of a chromophore system is determined by attenuated total reflection measurement of electro-optic activity coupled with hyper-Rayleigh scattering measurement of molecular first hyperpolarizability, and centrosymmetric order is determined by the variable angle polarization referenced absorption spectroscopy method. Theoretically: Order is determined from statistical mechanical models that predict the properties of soft condensed matter.

Full citation: [Stephanie J. Benight, Lewis E. Johnson, Robin Barnes, Benjamin C. Olbricht, Denise H. Bale, Philip J. Reid, Bruce E. Eichinger, Larry R. Dalton, Philip A. Sullivan, and Bruce H. Robinson, J. Phys. Chem. B, 2010114 (37), pp 11949–11956.]

Pictured: Stephanie Benight and a few of the co-authors of the paper. (Left to right) Lewis Johnson, Prof. Bruce Robinson, and Stephanie Benight.

UW team builds artificial enzyme

UW Chemistry professors Michael Gelb and Forrest Michael, in collaboration with Prof. David Baker (UW Biochemistry), have engineered an artificial enzyme capable of catalyzing a bimolecular Diels-Alder reaction with high stereoselectivity and substrate specificity. Their findings were reported July 16 in Science. The team of collaborators used computer modeling to screen over 10 billion possible protein backbone geometries for the ones that could support the right combination of active sites and catalytic residues. From this list, and further optimization, 84 de novo designs were selected for experimental work. Ultimately, two of the designed enzymes showed the ability to catalyze the Diels-Alder reaction.

The Diels-Alder reaction is one of the cornerstones of synthetic chemistry and no naturally occurring enzymes have been shown to catalyze it. Broader application of de novo enzyme design should be significantly useful in synthetic chemistry.

The authors of the paper also include Justin Siegel (graduate student in biochemistry, UW), Alexandre Zanghellini (graduate student in biochemistry, UW), Helena Lovick (graduate student in chemistry, UW), Gert Kiss (graduate student in chemistry, UCLA), Abigail Lambert (former graduate student with Prof. Stoddard), Jennifer St. Clair (Dept. of Biochemistry, UW), Jasmine Gallaher (lab technician, Baker lab),  Barry Stoddard (Professor at Fred Hutchinson Cancer Research Center in Seattle), Don Hilvert (Professor of Chemistry, ETH Zurich), Michael Gelb (Professor of Chemistry, UW), Ken Houk (Professor of Chemistry, UCLA), Forrest Michael (Associate Professor of Chemistry, UW), David Baker (Professor of Biochemistry, UW).

Picture: UW graduate student Justin Siegel, professor Forrest Michael, professor Michael Gelb and post-doctoral fellow Alexandre Zanghellini (Steve Ringman / The Seattle Times).

J. B. Siegel, A. Zanghellini, H. M. Lovick, G. Kiss, A. R. Lambert, J. L. St. Clair, J. L. Gallaher, D. Hilvert, M. H. Gelb, B. L. Stoddard, K. N. Houk, F. E. Michael, D. Baker “Computational Design of an Enzyme Catalyst for a Stereoselective Bimolecular Diels-Alder Reaction”, Science, 2010, 239, 309-313

Read the Science paper

Read the article in The Seattle Times

Read the Chemistry World article

Also visit faculty webpages for Michael Gelb, Forrest Michael and David Baker.

CMDITR research highlighted on two journal covers

Two recent journals have highlighted the research of the UW-based Science and Technology Center on Materials and Devices for Information Technology Research (CMDITR). The October 28, 2009 issues of the Journal of Materials Chemistry was a themed issue centered on Nonlinear Optics and featured articles by several CMDITR researchers as well as a cover photo highlighting that research. Even more recently, the January 19, 2010 issue of Accounts of Chemical Research also featured cover art depicting CMDITR research - primarily related to the article “Theory-Inspired Development of Organic Electro-optic Materials” by UW researchers Philip A. Sullivan and Larry R. Dalton.

Read the articles:
Accounts of Chemical Research: DOI: 10.1021/ar800264w
Journal of Materials Chemistry, 28 October, 2009

Visit the CMDITR website at www.stc-mditr.org

Goldberg et al. characterize methane-metal complex

Professor Karen Goldberg and researchers at the University of North Carolina and the University of Washington have described the first observation of a metal complex that binds methane in solution. The finding is reported in the October 23, 2009 issue of Science. The Science report describes a σ-methane complex that is shown to be quite stable in solution. This report is the first observation and full characterization of a relatively long-lived σ-methane complex in solution. Nuclear magnetic resonance (NMR) spectra of the complex were obtained by protonation of a rhodium-methyl precursor at -110 °C. The complex is observed to rapidly tumble in the coordination sphere of rhodium, exchanging free and bound hydrogens. Density functional theory calculations indicate that the complex is best described as η2-C,H methane coordination to the metal.

Professor Goldberg is the Director of the UW-based NSF Center for Enabling New Technologies through Catalysis, a Center for Chemical Innovation that seeks to find efficient, inexpensive and environmentally friendly ways to produce chemicals and fuels.

Citation: “Characterization of a Rhodium(I) σ-Methane Complex in Solution” Wesley Bernskoetter, Cynthia Schauer, Karen Goldberg, Maurice Brookhart, Science, 326 (5952), 553 (23 October 2009)

[DOI: 10.1126/science.1177485]

Read the Science paper

UW press release

Prof. Goldberg’s faculty page and research group website

Gamelin et al. report light-induced spontaneous magnetization in Science

A paper by Professor Daniel Gamelin, members of his research group, and collaborators at the University of Duisberg-Essen appeared in the August 21, 2009 issue of Science, published by the American Association for the Advancement of Science (AAAS). The paper details the spontaneous photoinduced polarization of Mn2+ spins in colloidal doped CdSE nanocrystals. Very large effective internal magnetic fields were observed up to ~50 K and photomagnetic effects are observed all the way up to room temperature.

Citation: “Light-Induced Spontaneous Magnetization in Doped Colloidal Quantum Dots” Rémi Beaulac, Lars Schneider, Paul I. Archer, Gerd Bacher, Daniel R. Gamelin, Science 325 (5943), 973 (21 August 2009) [DOI: 10.1126/science.1174419]

To view the abstract and full text, please visit Science magazine.

UW News press release

Kahr, Kaminsky, et al. determine structural origin of light polarizing properties of herapathite

A paper by Professor Bart Kahr and members of his research group appeared in this week’s issue of Science, published by the American Associate for the Advancement of Science (AAAS). The paper details the crystal structure of herapathite (iodoquinine sulfate), a crystal structure that had remained unknown since the crystalline compound was first discovered in 1852. Herapathite, which functions as a linear dichroic light polarizer, was used to produce the first large-aperture light polarizers, patented as Polaroid in 1929.

Citation: “Herapathite.” Bart Kahr, John Freudenthal, Shane Phillips, and Werner Kaminsky. Science 324 (5933), 1407 (12 June 2009). [DOI: 10.1126/science.1173605]

To view the abstract and full text, please visit: Science Magazine.

Pradip Rathod receives Gates Foundation grant

Professor Pradipsinh Rathod was one of 104 recipients of a grant through the Bill & Melinda Gates Foundation‘s new initiative, Grand Challenges Explorations in Global Health. Rathod’s grant will support a project titled “Strategies to Disable Hypermutagenesis in Malaria Parasites,” which targets components of the malaria genome and develops partner drugs to disable parasite hypermutagenesis, allowing older methods of treatment to be effective against the disease.

The Gates Foundation believes that “creative, unorthodox thinking is essential to overcoming the most persistent challenges in global health,” and the Grand Challenges Explorations initiative is designed to “foster innovation in global health research and expand the pipeline of ideas that merit further exploration.” The initiative features an accelerated grant-making process with short two-page applications requiring no preliminary data. Initial grants of approximately $100,000 are awarded, with the possibility of additional funding ($1 million or more) for projects that show promise. The projects selected fit into the fourteen “grand challenges” set forth by the Gates Foundation, which address seven long-term goals to improve health in the developing world, such as creating new vaccines, improving nutrition, and establishing quantitative assessments of overall population health.

To view the full article in UWeek, please visit: GCGH article.

The awarding of the GCGH grants was covered by the local press, with articles in the Seattle Post-Intelligencer and the Seattle Times.

For more information about Pradip Rathod and his research, please visit his faculty page.