From Princeton: “Researchers unlock coveted bond connection”

Princeton University

September 23 2016
Tien Nguyen

Researchers at Princeton University have introduced a long-awaited reaction capable of forming sp3-sp3 bonds whose presence increases a molecule’s complexity and its chances for clinical success as a drug candidate.

Published in Nature, the study detailed a mild and general method to couple sp3 carbon atoms – carbon centers defined by that fact that only single bonds connect them to their neighbors. Until now, this coveted reaction had resisted chemists’ efforts, even eluding transition metal catalysis, a powerful field that has enabled a staggering range of coupling reactions over the past 50 years.

General schematic of metallophotoredox catalyzed sp3-sp3 couplings

“The reaction is a very unique way of approaching how you would join molecules together, and broadly expands the types of carbons you can connect,” said David MacMillan, the James S. McDonnell Distinguished University, Professor of Chemistry and corresponding author on the work.

Their method revolves around the cooperation of two catalysts, a light-activated iridium catalyst and a nickel-based catalyst. Coined metallaphotoredox catalysis, this process circumvents roadblocks, such as undesired side reactions and an inability to form key intermediates, which had plagued other transition metal mediated attempts. Also, in contrast to previous, specialized versions of the reaction, the researchers’ strategy doesn’t require high temperatures, harsh basic compounds or additional zinc-based molecules.

The reaction succeeds by enlisting the two catalysts to bring together the molecules forming either side of the final sp3-sp3 bond. The light-activated iridium catalyst converts the commercially available starting compound known as a carboxylic acid into a ready partner. This intermediate is intercepted by the nickel catalyst, which can then incorporate the other chemical partner, called an alkyl halide. Finally, the nickel catalyst excises itself from the compound, releasing the desired product and resetting the cycle.

The team demonstrated the reaction’s generality as it proceeded smoothly with array of structurally diverse partners. Using this method, they also constructed the antiplatelet drug tirofiban in two steps from simple starting materials using their sp3-sp3 coupling reaction and another metallaphotoredox method recently developed in their lab. This example showcased the utility of their program for drug discovery though it holds potential for other industries as well.

“That’s what we really care about – inventing reactions that people will use,” MacMillan said. “We really want to do things that are enabling to people all around the world who care about making molecules.”

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

About Princeton: Overview

Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

From Yale: “Sterling Chemistry Lab reopens as a catalyst for cutting-edge science”

Yale University

August 31, 2016

Jim Shelton
james.shelton@yale.edu
203-361-8332

President Salovey addresses the crowd at the SCL ribbon-cutting event. (Photo by Michael Marsland)

From its gleaming, glass-enclosed teaching labs to the powerful mechanical hubs located in the basement and penthouse, the new Sterling Chemistry Lab (SCL) has all the right elements to be a citadel of science for the next century.

The 93-year-old building has been transformed from the inside out, and Yale officials celebrated with a grand reopening on Aug. 30. Hundreds of students, faculty, and staff gathered to tour SCL’s new teaching labs, hear more about the building’s history and envision scientific discoveries yet to come.

“The center of gravity of this campus is shifting north,” Yale President Peter Salovey said at the ribbon cutting, noting the construction of Yale’s newest residential colleges nearby and the resurgence of investment in Science Hill.

“We are at a moment here at Yale when we will take the excellent science, research, and education we do on campus, especially Science Hill, and move it to a truly outstanding level,” Salovey said. “We should want nothing less for students and for faculty.”

For the new SCL, that effort required two years of cranes, jackhammers, power saws, and occasional corridor closings. The exterior of the iconic building, designed by architect Williams Adams Delano in a Collegiate Gothic style, remains unchanged. CannonDesign is the architect for the renovation, with HBRA Architects designing the central public corridor areas, and Dimeo Construction guiding the work. SCL renovations encompass 159,000 square feet, of which 31,600 is additional space, and the building will be seeking LEED Gold certification.

The renovation includes new teaching labs for chemistry, such as this one, as well as labs for physics and biology. (Photo by Michael Marsland)

“Science is and must be a top priority for Yale,” said Provost Benjamin Polak. “If we think about what great universities will do in the 21st century, they’re going to advance knowledge by their discoveries, they’re going to change the world, and they’re going to move minds. That means science, and Yale has to be part of that — has to lead at that.”

A trio of teaching labs is central to that goal at the new SCL, both physically and symbolically. Biology teaching labs are located on the second floor, with flexibility allowing for adaptability to a variety of experiments and teaching needs; chemistry teaching labs are on the third floor, with individual venting hoods for each student conducting an experiment and dedicated spaces for teaching general, organic, advanced, and physical chemistry. Physics teaching labs are on the second floor, built with enhanced flexibility for experiments of different durations and sizes.

“This really is an occasion of coming together,” said Dean of the Faculty of Arts and Sciences (FAS) Tamar Gendler, noting that the renovation merges research and teaching, brings together students and faculty, and involves multiple disciplines. It also combines past and present, knits together different areas of the campus, and blends the abstract with the concrete, Gendler said.

Scott Miller, the Irénée du Pont Professor of Chemistry, divisional director of sciences for FAS, and former chair of the Department of Chemistry, took note of the many scientific discoveries that have taken place at SCL since 1923. He mentioned Lars Onsager’s work on thermodynamics for irreversible systems; the pioneering chemical biology research of Stuart Schreiber; and emeritus professor Jerome Berson’s research on reactive intermediates.

“Laboratories are sacred places,” Miller said. “Laboratories are the places where we try very hard to connect observation to explanation; where we try to make things on the basis of our theories and then when we can’t make them the way we’d like to we have to revise our theories. Laboratories are the places where we connect ‘mind to hand.’ These are truly profound things.”

In order to create teaching labs for today’s students, the SCL renovation involved a major overhaul of the building’s mechanical systems. Prior to renovation, many of the individual labs in SCL required separate services to handle venting, electricity, and other needs. Now there is a centralized system to handle the flow of power, water, and ventilation throughout the building. In addition, SCL has new replacement skylights and windows, switched from steam heat to hot-water baseboards, upgraded its sprinkler system, installed a bigger service elevator, completed masonry work, and conducted structural upgrades.

The renovation addresses aesthetic needs, as well. Expansive, well-lit corridors connect the labs with communal areas and a landscaped courtyard, for example. Also, the use of glass walls to frame the labs is intended to inspire a more connected, collaborative spirit among students and faculty.

“I can’t wait to come back in the coming weeks and see students at these benches and classes being taught,” Salovey said.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

From SLAC: Women in STEM – “SLAC, Stanford Team Finds a Tough New Catalyst for Use in Renewable Fuels Production” Linsey Seitz

SLAC Lab

September 1, 2016

Discovery Could Make Water-splitting Reaction Cheaper, More Efficient

Researchers at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory have developed a tough new catalyst that carries out a solar-powered reaction 100 times faster than ever before, works better as time goes on and stands up to acid.

And because it requires less of the rare and costly metal iridium, it could bring down the cost of a process that mimics photosynthesis by using sunlight to split water molecules – a key step in a renewable, sustainable pathway to produce hydrogen or carbon-based fuels that can power a broad range of energy technologies.

The team published their results today in the journal Science.

A simulation shows one possible way that a highly active iridium oxide layer could form on the surface of a strontium iridium oxide catalyst. Experiments by SLAC and Stanford researchers showed that strontium atoms (green spheres) left the top layer through a corrosion process during the catalyst’s first two hours of operation. The top layer then rearranged itself and became much better at accelerating chemical reactions. Follow-up X-ray studies at SLAC will examine these surface changes in more detail. (C.F. Dickens/Stanford University)

A Multi-pronged Search

The discovery of the catalyst – a very thin film of iridium oxide layered on top of strontium iridium oxide – was the result of an extensive search by three groups of experts for a more efficient way to accelerate the oxygen evolution reaction, or OER, which is half of a two-step process for splitting water with sunlight.

“The OER has been a real bottleneck, particularly in acidic conditions,” said Thomas Jaramillo, an associate professor at SLAC and Stanford and deputy director of the SUNCAT Center for Interface Science and Catalysis. “The only reasonably active catalysts we know that can survive those harsh conditions are based on iridium, which is one of the rarest metals on Earth. If we want to bring down the cost of such a pathway for making fuels from renewable sources and carry it out on a much larger scale, we need to develop catalyst materials that are more active and that use little or no iridium.”

The search started with SUNCAT theorists, who used computers to explore a database of materials and find the ones with the most potential to do exactly what was needed. Catalysts accelerate chemical reactions without being used up in the process, and databases like this one have become an important tool for designing catalysts to order, rather than testing thousands of materials in a time-consuming, trial-and-error approach.

Based on the results, a team led by SLAC Staff Scientist Yasuyuki Hikita and SLAC/Stanford Professor Harold Hwang, both investigators with the Stanford Institute for Materials and Energy Sciences (SIMES), synthesized one of the catalyst candidates, strontium iridium oxide. Linsey Seitz, a PhD student in Jaramillo’s group and first author of the report, investigated the material’s properties.

Stanford PhD student Linsey Seitz investigated the properties of a tough new catalyst material that carries out a key water-splitting reaction in acid. She is now a Helmholtz postdoctoral fellow at the Karlsruhe Institute of Technology in Germany. (Jesse D. Benck/Stanford University)

Sample of a new catalyst material created by SLAC and Stanford researchers. It’s 100 times better than previous catalysts at accelerating the oxygen-evolving reaction in acid, a key step in a pathway for making sustainable fuels. (Linsey Seitz/Stanford University)

Images made with an atomic force microscope show variations in the height of the catalyst’s surface before (left) and after its first 30 hours of operation. The observed changes in surface texture reflect strontium atoms leaving the top layers of the material during operation, forming a very catalytically active thin film of iridium oxide. (L. Seitz et. al., Science)

A Surprising Improvement

To the team’s surprise, this catalyst worked even better than expected, and kept improving over the first two hours of operation. Experiments probing the surface of the material indicated that a corrosion process released strontium atoms into the surrounding fluid during this initial period. This left a film of iridium oxide just a few atomic layers thick that was much more active than the original material, and 100 times more efficient at promoting the OER than any other acid-stable catalyst known to date.

“A lot of materials do this type of thing – surfaces can be very dynamic, changing during the course of a reaction – but in this case the catalyst changes in a way that gives you excellent performance in acid,” Jaramillo said. “This is unusual, because under these conditions most materials are either poor catalysts or they completely fall apart, or both.”

The researchers still don’t know exactly why this surface layer is so active, although the theorists, including SUNCAT graduate students Colin Dickens and Charlotte Kirk, have provided some ideas. Jaramillo’s group will be taking a closer look at the catalyst with X-ray beams at SLAC’s Stanford Synchrotron Radiation Lightsource, a DOE Office of Science User Facility, to determine exactly how the atoms on the surface rearrange themselves and why this boosts the catalyst’s performance.

SLAC SSRL

“To make a commercially viable catalyst we will need to reduce the amount of iridium in the material even more,” said Jens Nørskov, director of SUNCAT and a professor at SLAC and Stanford. “But there are many possibilities, and this gives us some very good leads.”

SUNCAT and SIMES are joint institutes of Stanford and SLAC. Major funding for the project came from the DOE Office of Science.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

From Cornell: “A miniaturized sensor that can measure chemistry on a chip”

Cornell University

August 17, 2016
Bill Steele

Light traveling through a nanoscale waveguide on a chip spreads beyond the waveguide and can interact with molecules above the surface of the chip. Credit: Cornell University

By combining expertise in photonics – manipulating light beams in nanoscale waveguides on a chip – and materials science, Cornell researchers have laid the groundwork for a chemical sensor on a chip that could be used in small portable devices to analyze samples in a lab, monitor air and water quality in the field and perhaps even detect explosives.

The researchers use a phenomenon called “Raman scattering:” when a laser strikes a molecule it kicks back the laser energy as photons of light at a variety of wavelengths that depend on the structure and composition of the molecule.

To allow this phenomenon to occur on a chip, researchers fire a laser into a waveguide – a strip of transparent material made of titanium dioxide, where the light bounces off the inside surfaces and becomes confined to the waveguide. Because a waveguide is only a few nanometers (billionths a meter) high, the light waves spread out beyond the waveguide, creating a so-called “evanescent field” above the surface of the chip. The pumping laser can induce Raman scattering in the space above the chip, or in a drop of liquid placed on its surface for analysis, while still confining the light wave to the chip. Light kicked back by the excited molecules also follows the waveguide; a prism at the end of the waveguide can spread that light into a spectrum that is a “fingerprint” identifying the molecule that produced it.

“If you need a chemical sensor in the lab, that is not a problem,” said Jin Suntivich, assistant professor of materials science and engineering. “But when you are outside, finding a chemical sensor that you can take with you is a challenge. We want to develop a technology that is small enough for a phone, such that your personal electronics can constantly monitor the world around you, and the moment you see something out of the ordinary, the sensor can tell you what it is.”

Sensors based on Raman scattering have been made before, using silicon nitride waveguides. The Cornell researchers have come up with a design that could make a sensor more sensitive and small enough to be used in the field by using a new material, titanium dioxide.

“We’re not the first but we’re the best,” said Christopher Evans, a Kavli Postdoctoral Fellow in the Laboratory of Atomic and Solid State Physics and the Kavli Institute at Cornell for Nanoscale Science. Evans is first author of paper describing the new approach published in the July 14 online edition of the American Chemical Society journal ACS Photonics. Co-authors are Suntivich and Chengyu Liu, a doctoral student in the School of Applied and Engineering Physics

A circular waveguide tangent to a straight guide causes light to circulate around and around, giving it more time to interact with material above the chip. The ring is about the diameter of a human hair.

Titanium dioxide has a much higher refractive index, making a greater contrast with the space above the chip, which creates a stronger evanescent field. The material is also transparent to light at visible wavelengths, a condition that allows researchers to use a laser at shorter, visible wavelengths, which induce better scattering. The researchers tested with a green laser pointer as a light source.

For a future device, a tiny laser unit can be built into a chip, as can a component that can spread out the wavelengths of the kicked off light onto a photosensitive device to read the spectrum. One possibility is to read the spectrum with the camera in a phone.

Interaction of the pumping laser with the material above the chip increases with the length of the waveguide. But the researchers also offer a way to increase the interaction without having to make the chip larger. The solution is a “ring resonator.” When a circular waveguide is set tangent to a straight guide, some of the light will enter the ring and continue to circle around it, letting the light interact continually with the material above the chip many times. The circumference of the ring can be adjusted to resonate with the wavelength of the light, intensifying the effect. “We have shown that we can increase the amount of peak signal from our sensors by an order of magnitude (or more), while simultaneously reducing the device footprint down to the cross-section of a human hair,” Evans said.

Potential applications include portable sensors to monitor air and water quality or conduct laboratory tests in the field. Chemists could and observe chemical reactions while they occur.

The work was supported in part by the Cornell Center for Materials Reseach and used the Cornell Nanoscale Facility, both funded by the National Science Foundation. Additional support was provided by the Samsung Advanced Institute of Technology and the Kavli Institute at Cornell for Nanoscale Science.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition
Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

From Princeton: “Professor explores new territory by bridging chemistry, biology”

Princeton University

August 11, 2016
Tien Nguyen, Department of Chemistry

In any given year, a synthetic chemist may set up several hundred chemical reactions. Many of these reactions will fail, so chemists temper their expectations.

But not Todd Hyster, a Princeton University assistant professor who joined the Department of Chemistry last summer.

Todd Hyster (right), a Princeton University assistant professor of chemistry, focuses his research on novel reactions in an area just emerging among American chemists — the merger of classic organic synthesis and biocatalysis. As one of the few synthetic chemists who understands biological systems, he is uniquely equipped to identify the reactions that would be most impactful for organic synthesis and make them happen. He encourages researchers in his lab, such as chemistry graduate student Braddock Sandoval (left), to harness chemistry and biology to bring about seemingly unlikely reactions. (Photos by C. Todd Reichart, Department of Chemistry)

“Todd gets really excited about these crazy ideas and he’s always confident that it’s going to work, even if we think it’s a long shot,” said Braddock Sandoval, a graduate researcher in Hyster’s lab.

Hyster focuses his research on novel reactions at the merger of two areas in which he has extensive experience: classic organic synthesis, which uses small molecules that perform an expansive range of reactions, and biocatalysis, which uses large biological systems such as enzymes to execute only specific reactions, but does so very efficiently. Researchers at the intersection of these fields propose to modify powerful enzymes so that they can be used in more organic reactions.

The majority of the work in this area has come from biology labs that are well acquainted with wrangling complex biological systems, but the field hasn’t seen the same level of engagement from chemists, especially in the United States. Essentially, chemists can have difficulty dealing with biological systems because they must learn how to grow cells and work with complicated enzymes. Yet, biologists may not know which of the thousands of possible reactions organic chemists would find most valuable and useful.

Hyster, however, can do both. As one of the few synthetic chemists who also understands biological systems, he is uniquely equipped to identify the reactions that would be most impactful for organic synthesis and make them happen.

“Todd has the ability to connect these enzymes to reaction mechanisms people aren’t even thinking about,” said David MacMillan, the James S. McDonnell Distinguished University Professor of Chemistry at Princeton. “He’s at the vanguard of something new in biocatalysis and I think it’s going to be incredibly exciting.”

Building up to biocatalysis

As a graduate student under the direction of Tomislav Rovis at Colorado State University, Hyster began research in transition-metal catalysis and, at the time, wanted nothing to do with biology. “I remember saying that I was ‘repulsed’ by biology,” Hyster said with a laugh, “probably one of the most naïve things I’ve ever said.”

It wasn’t until his third year of graduate school that his attitude began to shift. He became intrigued by a conference presentation on using mutated proteins to catalyze a specific reaction and even chose the general topic — directed evolution — for his departmental seminar. Then Rovis went on sabbatical in France and presented Hyster with the opportunity to collaborate with a research group working at the interface of biology and organometallic chemistry at the University of Basel in Switzerland, opening a new area of research for the Rovis lab in biocatalysis.

Rovis recalled emailing Hyster late at night from Europe to pitch him the collaboration idea. The usual strategy to improve the reaction is to change the small molecule known as the ligand. Instead, Rovis suggested keeping the ligand constant and changing the reaction environment using a biological system developed by the group in Basel. Hyster replied the next morning that he loved the idea and was game to try it.

“He’s someone who had the vision to see the real impact and potential of the idea, and who certainly doesn’t pay attention at all to how hard it might be. That’s the kind of researcher he is,” Rovis said.

In order to make the collaboration work, Hyster spent four months in Basel in Professor of Chemistry Thomas Ward’s laboratory learning how to work with proteins, ultimately bringing those skills back to the lab in Colorado.

“His fearlessness is his best quality,” Rovis said. “It’s what allowed him to embrace this new field that he had no prior experience with and successfully tackle the problem.”

The resulting work — published in the journal Science in 2012 — was the first example of a biological environment that could be engineered to promote the formation of new bonds. The reaction took advantage of the extremely strong binding affinity between the large protein streptavidin and the compound biotin, which is referred to as “molecular Velcro.” By attaching the ligand-metal complex to biotin, the researchers could lock the metal catalyst into the highly controlled binding pocket of streptavidin.

For his postdoctoral study, Hyster began to shift his focus onto biocatalysis. He joined the laboratory of one of the pioneers of biocatalysis, Frances Arnold, professor of chemical engineering, bioengineering and biochemistry at the California Institute of Technology.

In a 2014 paper published in the Journal of the American Chemical Society during his time in the Arnold lab, Hyster developed variants of the enzyme P450 — one of the most well-known enzymes that break down organic molecules in the liver — to catalyze a particularly unfavorable bond connection. In this type of reaction, known as an amination reaction, the catalyst typically breaks the weakest existing carbon-hydrogen bond to form the new bond. The specially designed P450 mutant, however, adopts a specific shape that favors the bond disconnection at the neighboring carbon, giving the researchers access to a reaction that would be difficult to accomplish by organic catalysis.

Focusing on the puzzles

At Princeton, Hyster is applying what he learned from his time in Rovis’ and Arnold’s labs in terms of both the science and mentorship. Their relaxed styles and flexibility in letting students follow their own interests were really effective, he said, and he hopes to emulate them.

Hyster is hands-off, but always available to answer questions, Sandoval said. The whole group works long hours in the lab and is eager to establish themselves in the research community. Hyster is very driven, Sandoval said, and his confidence and excitement for the work has inspired them to set up reactions that they may not have tried otherwise.

“If you pursue what you’re most passionate about, I think that’s when you can do your greatest possible amount of good,” Hyster said. Pursuing his own passion is already starting to pay off. Since starting up less than a year ago, the Hyster lab is already preparing to publish research about an enzyme-mediated light-based reaction that hasn’t been seen before.

Though pleased about these initial successes, for Hyster, the real satisfaction comes from the research process.

“I just like thinking about these problems. When I wake up, at home, all the time, it’s what I enjoy thinking about and that’s rewarding enough for me,” Hyster said. “It’s just an added bonus that these reactions might be valuable.”

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

About Princeton: Overview

Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

From U Illinois Chicago: “Breakthrough solar cell captures CO2 and sunlight, produces burnable fuel”

University of Illinois

July 28, 2016
Bill Burton

Simulated sunlight powers a solar cell that converts atmospheric carbon dioxide directly into syngas.

Researchers at the University of Illinois at Chicago have engineered a potentially game-changing solar cell that cheaply and efficiently converts atmospheric carbon dioxide directly into usable hydrocarbon fuel, using only sunlight for energy.

The finding is reported in the July 29 issue of Science and was funded by the National Science Foundation and the U.S. Department of Energy. A provisional patent application has been filed.

Unlike conventional solar cells, which convert sunlight into electricity that must be stored in heavy batteries, the new device essentially does the work of plants, converting atmospheric carbon dioxide into fuel, solving two crucial problems at once. A solar farm of such “artificial leaves” could remove significant amounts of carbon from the atmosphere and produce energy-dense fuel efficiently.

“The new solar cell is not photovoltaic — it’s photosynthetic,” says Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at UIC and senior author on the study.

“Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight,” he said.

While plants produce fuel in the form of sugar, the artificial leaf delivers syngas, or synthesis gas, a mixture of hydrogen gas and carbon monoxide. Syngas can be burned directly, or converted into diesel or other hydrocarbon fuels.

The ability to turn CO2 into fuel at a cost comparable to a gallon of gasoline would render fossil fuels obsolete.

Chemical reactions that convert CO2 into burnable forms of carbon are called reduction reactions, the opposite of oxidation or combustion. Engineers have been exploring different catalysts to drive CO2 reduction, but so far such reactions have been inefficient and rely on expensive precious metals such as silver, Salehi-Khojin said.

“What we needed was a new family of chemicals with extraordinary properties,” he said.

Amin Salehi-Khojin (left), UIC assistant professor of mechanical and industrial engineering, and postdoctoral researcher Mohammad Asadi with their breakthrough solar cell that converts atmospheric carbon dioxide directly into syngas.

Salehi-Khojin and his coworkers focused on a family of nano-structured compounds called transition metal dichalcogenides — or TMDCs — as catalysts, pairing them with an unconventional ionic liquid as the electrolyte inside a two-compartment, three-electrode electrochemical cell.

The best of several catalysts they studied turned out to be nanoflake tungsten diselenide.

“The new catalyst is more active; more able to break carbon dioxide’s chemical bonds,” said UIC postdoctoral researcher Mohammad Asadi, first author on the Science paper.

In fact, he said, the new catalyst is 1,000 times faster than noble-metal catalysts — and about 20 times cheaper.

Other researchers have used TMDC catalysts to produce hydrogen by other means, but not by reduction of CO2. The catalyst couldn’t survive the reaction.

“The active sites of the catalyst get poisoned and oxidized,” Salehi-Khojin said. The breakthrough, he said, was to use an ionic fluid called ethyl-methyl-imidazolium tetrafluoroborate, mixed 50-50 with water.

“The combination of water and the ionic liquid makes a co-catalyst that preserves the catalyst’s active sites under the harsh reduction reaction conditions,” Salehi-Khojin said.

The UIC artificial leaf consists of two silicon triple-junction photovoltaic cells of 18 square centimeters to harvest light; the tungsten diselenide and ionic liquid co-catalyst system on the cathode side; and cobalt oxide in potassium phosphate electrolyte on the anode side.

When light of 100 watts per square meter – about the average intensity reaching the Earth’s surface – energizes the cell, hydrogen and carbon monoxide gas bubble up from the cathode, while free oxygen and hydrogen ions are produced at the anode.

“The hydrogen ions diffuse through a membrane to the cathode side, to participate in the carbon dioxide reduction reaction,” said Asadi.

The technology should be adaptable not only to large-scale use, like solar farms, but also to small-scale applications, Salehi-Khojin said. In the future, he said, it may prove useful on Mars, whose atmosphere is mostly carbon dioxide, if the planet is also found to have water.

“This work has benefitted from the significant history of NSF support for basic research that feeds directly into valuable technologies and engineering achievements,” said NSF program director Robert McCabe.

“The results nicely meld experimental and computational studies to obtain new insight into the unique electronic properties of transition metal dichalcogenides,” McCabe said. “The research team has combined this mechanistic insight with some clever electrochemical engineering to make significant progress in one of the grand-challenge areas of catalysis as related to energy conversion and the environment.”

Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid is online at http://www.eurekalert.org/jrnls/sci/ or by contacting scipak@aaas.org.

Co-authors with Asadi and Salehi-Khojin are Kibum Kim, Aditya Venkata Addepalli, Pedram Abbasi, Poya Yasaei, Amirhossein Behranginia, Bijandra Kumar and Jeremiah Abiade of UIC’s mechanical and industrial engineering department, who performed the electrochemical experiments and prepared the catalyst under NSF contract CBET-1512647; Robert F. Klie and Patrick Phillips of UIC’s physics department, who performed electron microscopy and spectroscopy experiments; Larry A. Curtiss, Cong Liu and Peter Zapol of Argonne National Laboratory, who did Density Functional Theory calculations under DOE contract DE-ACO206CH11357; Richard Haasch of the University of Illinois at Urbana-Champaign, who did ultraviolet photoelectron spectroscopy; and José M. Cerrato of the University of New Mexico, who did elemental analysis.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

The University of Illinois at Urbana-Champaign community of students, scholars, and alumni is changing the world.

With our land-grant heritage as a foundation, we pioneer innovative research that tackles global problems and expands the human experience. Our transformative learning experiences, in and out of the classroom, are designed to produce alumni who desire to make a significant, societal impact.

From Notre Dame: “Notre Dame chemistry and biochemistry hosts faculty from Pontifical Catholic University of Chile”

Notre Dame University

May 16, 2016
Brian Wallheimer

No image caption. No image credit.
_________________________________________________________

Seven members of the Pontifical Catholic University of Chile (PUC) visited Notre Dame last week to strengthen developing research partnerships and plan upcoming workshops in biochemistry and chemistry, the latest in a partnership between the universities started in 2013.

Notre Dame and PUC signed a memorandum of understanding in 2013 that formalized research partnerships, as well as faculty and student exchange programs. Much of the work and collaborations have been possible through the Luksic Grants Program through Notre Dame International.

“The department has fully embraced the opportunity to work with PUC Chile,” says Ken Henderson, chair of the Department of Chemistry and Biochemistry at Notre Dame. “The latest visit by PUC Chile faculty to Notre Dame demonstrates the enthusiasm for building this relationship.”

Since the universities formally partnered, they have held joint graduate summer schools in Santiago, Chile, along with the University of Heidelberg, which Notre Dame entered into a similar agreement with in 2014. Last year, the three schools organized the Santander International Summer School on molecular catalysts in Chile, focused on fundamentals and developments in molecular catalysts. Students from Germany, France, Chile, Brazil, Spain, Switzerland and the United States attended.

Notre Dame has hosted PUC graduate student research visits, and nine Notre Dame faculty have visited Chile over the past two years.

The universities are working to develop a dual doctoral program over the next few months, and there will be a graduate workshop on X-ray crystallography and a joint symposium on drug discovery in Chile in the next academic year.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

The University of Notre Dame du Lac (or simply Notre Dame /ˌnoʊtərˈdeɪm/ NOH-tər-DAYM) is a Catholic research university located near South Bend, Indiana, in the United States. In French, Notre Dame du Lac means “Our Lady of the Lake” and refers to the university’s patron saint, the Virgin Mary.

The school was founded by Father Edward Sorin, CSC, who was also its first president. Today, many Holy Cross priests continue to work for the university, including as its president. It was established as an all-male institution on November 26, 1842, on land donated by the Bishop of Vincennes. The university first enrolled women undergraduates in 1972. As of 2013 about 48 percent of the student body was female.[6] Notre Dame’s Catholic character is reflected in its explicit commitment to the Catholic faith, numerous ministries funded by the school, and the architecture around campus. The university is consistently ranked one of the top universities in the United States and as a major global university.

The university today is organized into five colleges and one professional school, and its graduate program has 15 master’s and 26 doctoral degree programs.[7][8] Over 80% of the university’s 8,000 undergraduates live on campus in one of 29 single-sex residence halls, each of which fields teams for more than a dozen intramural sports, and the university counts approximately 120,000 alumni.[9]

The university is globally recognized for its Notre Dame School of Architecture, a faculty that teaches (pre-modernist) traditional and classical architecture and urban planning (e.g. following the principles of New Urbanism and New Classical Architecture).[10] It also awards the renowned annual Driehaus Architecture Prize.

From Princeton: “Theorists smooth the way to solving one of quantum mechanics oldest problems: Modeling quantum friction (J. Phys. Chem. Letters)”

Princeton University

May 16, 2016
Tien Nguyen, Department of Chemistry

From left to right: Herschel Rabitz, Renan Cabrera, Andre Campos and Denys Bondar. Photo credit: C. Todd Reichart

Theoretical chemists at Princeton University have pioneered a strategy for modeling quantum friction, or how a particle’s environment drags on it, a vexing problem in quantum mechanics since the birth of the field. The study was published* in the Journal of Physical Chemistry Letters.

“It was truly a most challenging research project in terms of technical details and the need to draw upon new ideas,” said Denys Bondar, a research scholar in the Rabitz lab and corresponding author on the work.

Quantum friction may operate at the smallest scale, but its consequences can be observed in everyday life. For example, when fluorescent molecules are excited by light, it’s because of quantum friction that the atoms are returned to rest, releasing photons that we see as fluorescence. Realistically modeling this phenomenon has stumped scientists for almost a century and recently has gained even more attention due to its relevance to quantum computing.

“The reason why this problem couldn’t be solved is that everyone was looking at it through a certain lens,” Bondar said. Previous models attempted to describe quantum friction by considering the quantum system as interacting with a surrounding, larger system. This larger system presents an impossible amount of calculations, so in order to simplify the equations to the pertinent interactions, scientists introduced numerous approximations.

These approximations led to numerous different models that could each only satisfy one or the other of two critical requirements. In particular, they could either produce useful observations about the system, or they could obey the Heisenberg Uncertainty Principle, which states that there is a fundamental limit to the precision with which a particle’s position and momentum can be simultaneous measured. Even famed physicist Werner Heisenberg’s attempt to derive an equation for quantum friction was incompatible with his own uncertainty principle.

The researchers’ approach, called operational dynamic modeling (ODM) and introduced in 2012 by the Rabitz group, led to the first model for quantum friction to satisfy both demands. “To succeed with the problem, we had to literally rethink the physics involved, not merely mathematically but conceptually,” Bondar said.

Bondar and his colleagues focused on the two ultimate requirements for their model – that it should obey the Heisenberg principle and produce real observations – and worked backwards to create the proper model.

“Rather than starting with approximations, Denys and the team built in the proper physics in the beginning,” said Herschel Rabitz, the Charles Phelps Smyth ’16 *17 Professor of Chemistry and co-author on the paper. “The model is built on physical and mathematical truisms that must hold. This distinct approach creates a new rigorous and practical formulation for quantum friction,” he said.

The research team included research scholar Renan Cabrera and Ph.D. student Andre Campos as well as Shaul Mukamel, professor of chemistry at the University of California, Irvine.

Their model opens a way forward to understand not only quantum friction but other dissipative phenomena as well. The researchers are interested in exploring the means to manipulate these forces to their advantage. Other theorists are rapidly taking up the new paradigm of operational dynamic modeling, Rabitz said.

Reflecting on how they arrived at such a novel approach, Bondar recalled the unique circumstances under which he first started working on this problem. After he received the offer to work at Princeton, Bondar spent four months awaiting a US work visa (he is a citizen of the Ukraine) and pondering fundamental physics questions. It was during this time that he first thought of this strategy. “The idea was born out of bureaucracy, but it seems to be holding up,” Bondar said.

Read the full article here:

Bondar, D. I.; Cabrera, R.; Campos, A.; Mukamel, S.; Rabitz, H. A. Wigner-Lindblad Equations for Quantum Friction.” J. Phys. Chem. Lett. 2016, 7, 1632.

This work was supported by the US National Science Foundation CHE 1058644, the US Department of Energy DE-FG02-02ER-15344, and ARO-MURI W911NF-11-1-0268.

*Science paper:
Wigner–Lindblad Equations for Quantum Friction

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

About Princeton: Overview

Princeton University is a vibrant community of scholarship and learning that stands in the nation’s service and in the service of all nations. Chartered in 1746, Princeton is the fourth-oldest college in the United States. Princeton is an independent, coeducational, nondenominational institution that provides undergraduate and graduate instruction in the humanities, social sciences, natural sciences and engineering.

As a world-renowned research university, Princeton seeks to achieve the highest levels of distinction in the discovery and transmission of knowledge and understanding. At the same time, Princeton is distinctive among research universities in its commitment to undergraduate teaching.

Today, more than 1,100 faculty members instruct approximately 5,200 undergraduate students and 2,600 graduate students. The University’s generous financial aid program ensures that talented students from all economic backgrounds can afford a Princeton education.

From Ethan Siegel: “Which Elements Will Never Be Made By Our Sun?”

Starts with a Bang

May 11, 2016
Ethan Siegel

A high-resolution spectrum showing the elements in the Sun, by their visible-light absorption properties. Image credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF.

Our Sun is the greatest source of heat and light in the entire Solar System, fusing hydrogen into helium in a nuclear chain reaction in its core. Because an atomic nucleus of helium is 0.7% lighter than the four hydrogen nuclei that it’s created from, that act of nuclear fusion releases a tremendously efficient amount of energy. Over the course of its 4.5 billion year lifetime (so far), the Sun had lost about the mass of Saturn due to the amount of hydrogen that’s fused into helium, through Einstein’s E = mc^2, which is the root source of all the sunlight we receive here on Earth. The Sun has a lot more going on inside of it than just fusing hydrogen (the lightest element) into helium (the second lightest), though, and is capable of making so many more elements than that. But the periodic table has a whole slew of elements the Sun can never make.

Periodic Table 2016

We’re pretty fortunate that our Sun wasn’t among the very first stars in the Universe. Shortly after the Big Bang, the Universe was made exclusively of hydrogen and helium: 99.999999% of the Universe was composed of these two elements alone. Yet the first massive stars didn’t just fuse hydrogen into helium, but eventually fused helium into carbon, carbon into oxygen, oxygen into silicon and sulfur, and then silicon and sulfur into iron, nickel and cobalt. When the inner core reached a large enough concentration of those heavy elements, a catastrophic supernova occurred, creating a rapid burst of neutrons that were scattered into the other nuclei. Very quickly, the types of elements present in the Universe climbed up and up the periodic table, creating everything we’ve ever found in nature and many elements even heavier than that. Even the very first core-collapse supernovae created elements that are beyond the limit of what we find on Earth: elements heavier than even uranium and plutonium.

The various layers of a supernova-bound star. During the supernova itself, many trans-uranic elements are created, through rapid neutron capture. Image credit: Nicolle Rager Fuller of the NSF.

But our Sun won’t go supernova, and won’t ever make those elements. That rapid burst of neutrons that happens in supernova allows the creation of elements through the r-process, where elements rapidly absorb neutrons and climb the periodic table in great leaps and jumps. Instead, our Sun will burn through the hydrogen in its core, and then will contract and heat up until it can begin fusing helium in its core. This phase of life — where our Sun will become a red giant star — is something that happens to all stars that are at least 40% as massive as our own.

Red Giant, SSL UC Berkeley

Reaching the right temperatures and densities, simultaneously, for helium fusion, is what separates red dwarfs (which can’t get there) from all other stars (which can). Three helium atoms fuse together into carbon, and then through another hydrogen-fusion pathway — the CNO cycle — we can create nitrogen and oxygen, while we can continue to add helium to various nuclei to climb up the periodic table. Carbon and helium make oxygen; carbon and oxygen make neon; carbon and neon make magnesium. But two very particular reactions take place that will create the vast majority of elements we know:

carbon-13 will fuse with helium-4, creating oxygen-16 and a free neutron, and
neon-22 will fuse with helium-4, creating magnesium-25 and a free neutron.

Image credit: screenshot from the wikipedia article on the s-process.

Free neutrons aren’t created in great abundance, just in relatively scarce numbers, since such a small percentage of these atoms actually are carbon-13 or neon-22 at any given time. But these free neutrons can only stick around for about 15 minutes, on average, until they decay away.

The two types (radiative and non-radiative) of neutron beta decay. Image credit: Zina Deretsky, National Science Foundation.

Fortunately, the interior of the Sun is dense enough that 15 minutes is more than enough time for this free neutron to run into another atomic nucleus, and when it does, it inevitably gets absorbed, creating a nucleus that’s one atomic mass unit heavier than before the neutron was absorbed. There are a few nuclei this won’t work for: you can’t create a mass-5 nucleus (out of helium-4, for instance) or a mass-8 nucleus (out of lithium-7, for examples), since they’re all inherently too unstable. But everything else will either be stable on timescales of at least tens of thousands of years, or it will decay by emitting an electron (through β-decay), which causes it to move one element up the periodic table.

Image credit: E. Siegel, based on the original from the University of Oregon’s physics department, via http://zebu.uoregon.edu/2004/a321/lec10.html.

During any star’s red giant, helium-burning phase, this enabled you to build all the elements between carbon and iron through this process of slow neutron capture, and heavy elements from iron all the way up through lead through that very same process. This process, known as the s-process (because neutrons are produced-and-captured slowly), runs into a problem when it tries to build elements heavier than lead. The most common isotope of lead is Pb-208, with 82 protons and 126 neutrons. If you add a neutron to it, it beta decays to become bismuth-209, which can then capture a neutron and β-decay again to become polonium-210. But unlike the other isotopes, which live for years, Po-210 only lives for days before emitting an alpha particle — or a helium-4 nucleus — and returning back to lead in the form of Pb-206.

The chain reaction that’s at the end of the line for the s-process. Image credit: E. Siegel and the English Language Wikipedia.

This leads to a cycle: lead captures 3 neutrons, becomes bismuth, which captures one more and becomes polonium, which then decays back to lead. In our Sun and in all stars that won’t go supernova, that’s the end of the line. Combine that with the fact that there’s no good pathway to get the elements between helium and carbon (lithium, beryllium and boron are produced from cosmic rays, not inside of stars), and you’ll find that the Sun can make a total of 80 different elements: helium and then everything from carbon through polonium, but nothing heavier. For that, you need a supernova or a neutron star collision.

Two neutron stars colliding, which is the primary source of many of the heaviest periodic table elements in the Universe. Image credit: Dana Berry, SkyWorks Digital, Inc.

But think about that: of all the naturally occurring elements here on Earth, the Sun makes about 90% of them, all from a tiny, non-descript star of no particular cosmic significance. The ingredients for life are literally that easy to come by.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

From SA: “Earth Has Mystery Gas Delivered from Space”

Scientific American

April 28, 2016
Anthony King, ChemistryWorld

Credit: Wikimedia Commons/NASA/JPL-Caltech

Xenon from deep within the Earth’s mantle has shone a light on the planet’s formation and early evolution. The isotopic signature of this earthly xenon has been shown to resemble that of primitive meteorites and differs markedly from the profile of the gas found in the atmosphere, which is mysteriously missing most of its xenon.

The origin of Earth’s volatile elements such as water, carbon and nitrogen remains a puzzle. It is difficult to determine if these elements originated from solar gas after the solar system formed or were delivered by asteroids or comets.

A new study, which sampled xenon from carbon dioxide-rich mineral spring gas from the volcanic Eifel province in Germany, points to an asteroidal origin for part of the volatile elements trapped in Earth’s mantle—planetary bodies whose remnants now lie between Mars and Jupiter. The mysterious xenon in the atmosphere came from elsewhere, possibly comets.

‘We conclude that this [mantle] component was contributed by asteroids when the proto-Earth was still building up,’ notes senior author Bernard Marty at the University of Lorraine, France. ‘The ancestor atmosphere xenon was contributed later on at the Earth’s surface, by late bombardments, and never mixed up with mantle xenon.’ This late bombardment occurred around 800 million years after Earth’s formation and might have involved cometary bodies. The isotopic signature of xenon on comets is unknown, however.

The extraterrestrial chondritic xenon found in the mantle has been isolated for 4.45 billion years. It also proves that volcanism in Eifel relates to upwelling from the deep mantle, likely to be over 700 km deep.

‘It’s a small step forward to show that mantle xenon came from meteorites, but the big step forward is showing that this component is not related to the atmosphere,’ says Christopher Ballentine, a geochemist at the University of Oxford, UK, who was not involved with this work.

Atmospheric xenon’s origin was not just from outgassing of the mantle and is more complex, Ballentine explains. ‘Nobody has measured xenon composition in comets yet, so maybe that is the source,’ he adds. Around 90% of the xenon expected to be in Earth’s atmosphere is missing, with various theories posited. The enigma of the ‘missing xenon’ and where it went is one of the big unsolved puzzles in geochemistry.

‘Understanding xenon really is a lynchpin for understanding the early formation of volatiles. And resolving how volatiles arrived at the planet tells us something fundamental about the way in which the planets formed,’ Ballentine says.

See the full article here .

Please help promote STEM in your local schools.

Stem Education Coalition

Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.