Tuesday, April 19, 2011

Novel ionic liquid batteries

 Scientists at the NRL Materials Science and Technology Division are providing solid evidence that there is a new route towards developing novel, lightweight energy storage devices. By moving away from centuries of caustic, hazardous aqueous-based battery cells and instead using non-volatile, thermally-stable ionic liquids, scientists predict multiple new types of batteries.

Rather than depend on highly acidic electrolytes, ionic liquids are used to create a solid polymer electrolyte composed of an ionic liquid and polyvinyl alcohol, developing novel types of solid state batteries with discharge voltages ranging up to 1.8 volts.

The unique properties of ionic liquids have fostered this explosive interest in battery applications. Ionic liquids are room temperature molten salts that possess many important characteristics, such as nearly no vapor pressure, non- flammability and lack of reactivity in various electrochemical or industrial applications. "It is the high thermal and electrochemical stability of the ionic liquids which has fostered the growing interest in ionic liquids for use in various electrochemical processes," said Dr. Thomas Sutto. "These new types of solid-state cells mimic standard alkaline cells, but without the need for caustic electrolytes."

Limits imposed by using corrosive electrolytes often result in severe restrictions to standard battery geometry and the need for special corrosive-resistant battery containers. The use of reactive ionic liquids in non-aqueous cells replaces the more hazardous highly alkaline electrolytes such as manganese oxide (MgO) and zinc (Zn) found in traditional batteries.

The root of this work began during standard corrosion studies of different metals in ionic liquids. While working with ionic liquids based on mineral acids, such as hydrogen sulphates, it was observed that Zn metal would react to form zinc sulphate. Since this is similar to that observed for the zinc anode in a standard alkaline cell, a series of experiments were then performed to determine how different metal oxides reacted in these types of ionic liquids.

Electrochemical experiments demonstrate that not only can these reactive ionic liquids act as the electrolyte/separator in both solid state and liquid batteries, but they can also act as a reactive species in the cell's electrochemical makeup. Using a non-aqueous approach to primary and secondary power sources, batteries are designed using standard cathode and anode materials such as magnesium dioxide (MgO2), lead dioxide (PbO2) and silver oxide (AgO). The ionic liquid that is the main focus of this work is 1-ethyl-3-methylimidazolium hydrogen sulphate (EMIHSO4), however, other ionic liquids such as those based on the nitrate and dihydrogen phosphate anions (negatively charged ions) have also been found to work well in this type of a battery design.

The use of these electrolytes suggests the potential for new types of rechargeable systems, such as replacement electrolytes in nickel-metal hydride (NiMH) batteries, or even the standard lead-acid battery. Experimental work is currently underway to develop such a rechargeable ionic liquid power source. The ability to create solid separators also allows for the formation of many new types of batteries via a number of fabrication techniques.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Naval Research Laboratory.

Scientists finely control methane combustion to get different products

 Scientists have discovered a method to control the gas-phase selective catalytic combustion of methane, so finely that if done at room temperature the reaction produces ethylene, while at lower temperatures it yields formaldehyde. The process involves using gold dimer cations as catalysts -- that is, positively charged diatomic gold clusters. Being able to catalyze these reactions, at or below room temperature, may lead to significant cost savings in the synthesis of plastics, synthetic fuels and other materials.

The research was conducted by scientists at the Georgia Institute of Technology and the University of Ulm. It appears in the April 14, 2011, edition of The Journal of Physical Chemistry C.

"­The beauty of this process is that it allows us to selectively control the products of this catalytic system, so that if one wishes to create formaldehyde, and potentially methyl alcohol, one burns methane by tuning its reaction with oxygen to run at lower temperatures, but if it's ethylene one is after, the reaction can be tuned to run at room temperature," said Uzi Landman, Regents' and Institute Professor of Physics and director of the Center for Computational Materials Science at Georgia Tech.

Reporting last year in the journal Angewandte Chemie International Edition, a team that included theorists Landman and Robert Barnett from Georgia Tech and experimentalists Thorsten Bernhardt and Sandra Lang from the University of Ulm, found that by using gold dimer cations as catalysts, they can convert methane into ethylene at room temperature.

This time around, the team has discovered that, by using the same gas-phase gold dimer cation catalyst, methane partially combusts to produce formaldehyde at temperatures below 250 Kelvin or -9 degrees Fahrenheit. What's more, in both the room temperature reaction-producing ethylene, and the formaldehyde generation colder reaction, the gold dimer catalyst is freed at the end of the reaction, thus enabling the catalytic cycle to repeat again and again.

The temperature-tuned catalyzed methane partial combustion process involves activating the methane carbon-to-hydrogen bond to react with molecular oxygen. In the first step of the reaction process, methane and oxygen molecules coadsorb on the gold dimer cation at low temperature. Subsequently, water is released and the remaining oxygen atom binds with the methane molecule to form formaldehyde. If done at higher temperatures, the oxygen molecule comes off the gold catalyst, and the adsorbed methane molecules combine to form ethylene through the elimination of hydrogen molecules.

In both the current work, as well as in the earlier one, Bernhardt's team at Ulm conducted experiments using a radio-frequency trap, which allows temperature-controlled measurement of the reaction products under conditions that simulate realistic catalytic reactor environment. Landman's team at Georgia Tech performed first-principles quantum mechanical simulations, which predicted the mechanisms of the catalyzed reactions and allowed a consistent interpretation of the experimental observations.

In future work, the two research groups plan to explore the use of multi-functional alloy cluster catalysts in low temperature-controlled catalytic generation of synthetic fuels and selective partial combustion reactions.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Georgia Institute of Technology.

Journal Reference:

Sandra M. Lang, Thorsten M. Bernhardt, Robert N. Barnett, Uzi Landman. Temperature-Tunable Selective Methane Catalysis on Au2 : From Cryogenic Partial Oxidation Yielding Formaldehyde to Cold Ethylene Production. The Journal of Physical Chemistry C, 2011; 115 (14): 6788 DOI: 10.1021/jp200160r

Recipe for radioactive compounds aids nuclear waste and fuel storage pools studies

Easy-to-follow recipes for radioactive compounds like those found in nuclear fuel storage pools, liquid waste containment areas and other contaminated aqueous environments have been developed by researchers at Sandia National Laboratories.

"The need to understand the chemistry of these compounds has never been more urgent, and these recipes facilitate their study," principal investigator May Nyman said of her group's success in encouraging significant amounts of relevant compounds to self-assemble.

The trick to the recipes is choosing the right templates. These are atoms or molecules that direct the growth of compounds in much the way islands act as templates for coral reefs.

The synthesized materials are stable, pure and can be studied in solution or as solids, making it easier to investigate their chemistry, transport properties and related phases.

The compounds are bright yellow, soluble peroxides of uranium called uranyl peroxide. These and related compounds may be present in any liquid medium used in the nuclear fuel cycle. They also appear in the environment from natural or human causes.

Made with relatively inexpensive and safe depleted uranium, the recipes may be adapted to include other, more radioactive metals such as neptunium, whose effects are even more important to study, Nyman said.

Cesium -- an element of particular concern in its radioactive form -- proved to be, chemically, an especially favored template for the compounds to self-assemble.

The work was done as part of the Actinide Materials Department of Energy (DOE) Energy Frontiers Research Center (EFRC) led by professor Peter Burns at Notre Dame University. Using the new method, researchers at the University of California-Davis are studying how materials behave in water and in different thermal environments, while researchers at DOE's Savannah River Site study the analogous behavior of neptunium.

The research will be featured as the cover article of the May 3 online European Journal of Inorganic Chemistry, to be published in print May 13. It currently is highlighted in preview in the online ChemViews Magazine.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by DOE/Sandia National Laboratories.

Journal Reference:

May Nyman, Mark A. Rodriguez, Todd M. Alam. The U28 Nanosphere: What's Inside? European Journal of Inorganic Chemistry, 2011; DOI: 10.1002/ejic.201001355

Poppy seed tea can kill you (repost)

Almost exactly two years ago, I posted the following story at the ScienceBlogs home of Terra Sigillata. I was drawn to revisit this moving, tragic story yesterday after reading a post by organometallic chemist Sharon Neufeldt at I Can Has Science? entitled, Morphine, Heroin, and Lemon Poppy Seed Cake.

In honor of Tom’s courage and the memory of his son, this repost is a fitting adjunct to Sharon’s essay.

The following post appeared originally on 31 March 2009 at the ScienceBlogs home of Terra Sigillata.

A little over a week ago, we posted on the very sad story of the accidental death of a University of Colorado sophomore from ingesting poppy seed tea. The poppy, Papaver somniferum, is the commercial source for prescription narcotic painkillers such as morphine and codeine. The seeds can be had online and in retail stores. The plants can often be grown if these seeds are not roasted or otherwise sterilized.

I had originally suspected that the CU-Boulder student had not used poppy seed tea but rather some other decoction of the plant itself. I had always contended that the seeds did not contain appreciable amounts of morphine, codeine, or other opiate-related molecules. However, it appears that I am wrong.

Commenter Tom
just shared with me the absolutely heartbreaking story of the death of his 17-year-old son from poppy seed tea:


Just a note regarding your statement: “A previous report has been that the student and friends were boiling up poppy seeds, but I was suspicious as those lack significant amounts of opiates.”.

Our son died 6 years ago from exactly the same causes as the man in this case. Except that my did in fact use only poppy seeds, in large amounts. Even though there is no Morphine in the seeds, they contain traces from the rest of the plant from the processing/harvesting. We have put up a Web site that includes the coroner’s report stating that cause of death was indeed Morphine overdose from poppy seed tea. You can find our Web site at: http://www.poppyseedtea.com/

I spent some time on Tom’s site, Poppy Seed Tea Can Kill You, and I just have to say that I am in awe of the effort and courage this gentleman has undertaken to keep other kids and other parents from experiencing the same tragedy.

Related specifically to Tom’s comment, he has courageously posted a redacted version of the medical examiner’s report from 13 Sept 2003. Therein, the toxicology analysis of tissues, blood, and the tea his son ingested are detailed. On the third page, the content of the tea was quantified as having a “high level of morphine,” 259 micrograms/mL.

Calculating a lethal dose for morphine is difficult because previous use of morphine can causes significant tolerance, or resistance, to both the therapeutic and lethal effects of the drug. For example, a dose of 100-150 mg may be lethal to a person who has never taken morphine orally, but it is not unusual for cancer patients with chronic pain to take as much as 4,000 mg/day.

Therefore, Tom’s son could’ve received a lethal dose by drinking as little as a pint of the poppy tea he had prepared.

The medical examiner himself concluded the opinion section of the report by saying:

Poppy seeds are the natural source of opioid analgesics. Although they contain extremely low levels of the drug, concentration of these compounds by brewing can result in potentially lethal levels. [emphasis mine]

Frankly, I don’t know if I would have what it takes to set up such a website in my son’s memory. But as Tom writes there:

Why do we have this site?
When, as parents, we realized that our son was taking poppy seed tea, we saw it as a “natural herbal tea”, prepared with an ingredient sold openly in supermarkets without any restrictions, and thought that it was acceptable for him to do this. When we looked on the Internet for additional information on it, we did find several sites that talked about it, but none stated clearly that this tea contained morphine and that these levels could potentially be lethal. Even after our son’s overdose accident, we were surprised to find out that even within the medical community, the fact that the morphine content in poppy seed tea can be very high is not widely known.

The purpose of this Web site is to hopefully have it show up in Internet search results for people researching the subject. Mostly for curious users experimenting with it, like our son was, but also for concerned parents looking to understand the risks that their children may be undertaking. We can only wish that we had seen the information provided on this Web site when we did our Internet search trying to understand what the risks were. Please share with others…

Yes, we will share with others.

I am deeply appreciative of Tom stopping by and raising my awareness of the dangers of poppy seed tea. Again, I am in awe of his selflessness in providing this information and establishing his website.

My hope is that our post here popularizing his message increases the dissemination of the message on the danger of using poppy seed tea.


Yale student killed in machine shop accident

A Yale University senior, Michele Dufault, was killed last night in an accident in the chemistry department machine shop. Although the university says only that it was “a terrible accident involving a piece of equipment,” the New Haven Register reports that Dufault’s hair was caught in a spinning lathe and was dead when emergency responders arrived.

Dufault was an astronomy and physics major who helped organize the Northeast Conference for Undergraduate Women in Physics in January.

An AP story says that “The university told the U.S. Occupational Safety and Health Administration that Dufault was operating the machinery for a senior project when she was killed.” A commenter to a Yale Daily News story says that “Michele was very competently trained. She took two semesters of shop training and knew her way around the machines.”

C&EN has its annual staff meeting over the rest of the week, so I’ll try to keep tabs on this but will largely be otherwise occupied. As more information comes out, feel free to post it in the comments.

And remember this basic safety rule that applies to the lab as much as machine shops: Tie back long hair.

Other blogosphere discussion so far: CENtral Science’s own Transition States, Chemistry Blog, The Great Beyond

Update from Yale University President Richard C. Levin, via an e-mail from the university’s public affairs office:

Last night, Michele’s hair got caught in a lathe as she worked on a project in the student machine shop in the Sterling Chemistry Laboratory. Her body was found by other students who had been working in the building. They called the police, who responded immediately.

Michele was an exceptional science student who was pursuing a B.S. in astronomy and physics. She also had keen interest in oceanography and was intending to undertake work in that field after graduation. She was an enthusiastic saxophonist in the Yale Band, and a widely admired member of the Saybrook College community.

The safety of our students is a paramount concern. The University has programs to train students before they use power equipment. Nonetheless, I have initiated a thorough review of the safety policies and practices of laboratories, machine shops, and other facilities with power equipment that is accessed and operated by undergraduates. This includes arts as well as science facilities. Steven Girvin, Deputy Provost for Science and Technology, will lead the review. Until the review is completed, Yale College will limit undergraduate access to facilities with power equipment to hours that will be specified by the end of the week; monitors will be present at these times in all such locations.


Ensemble Hits Macrocycle Milestone

Today, Ensemble Therapeutics announced it has developed experimental drugs with molecular structures containing a large ring, which the company calls Ensemblins, against one of 8 key drug targets laid out in a 2009 agreement with Bristol-Myers Squibb Company (BMS). As a result, the drug development program will be handed off to BMS and Ensemble will receive a milestone payment. Neither the drug target nor the milestone payment amount have been disclosed.

I first became acquainted with Ensemble in 2008, when I wrote about a symposium extolling the potential benefits of compounds containing rings of 12 or more atoms, also known as macrocycles, in drug discovery. These molecules are larger in size than traditional small molecule drugs, but they can increase the strength of a binding interaction at a desired target, or even make it possible to target proteins in the body that traditional small molecule drugs can’t. Some macrocylic drugs are already on the market, such as the antibiotic erythromycin and the immunosuppressant rapamycin.

In 2009, I focused on one of Ensemble’s proprietary drug discovery programs, but since then the company has partnered with both Pfizer and BMS, developing macrocyclic Ensemblins for tough-to-hit targets. In reporting the 2009 story, I learned that Ensemble’s discovery platform, which is based on chemistry carried out in company founder David R. Liu’s lab at Harvard University, uses DNA to guide production of thousands of different macrocycles at a time, and then tests the macrocycles’ ability to disrupt biologically relevant interactions between proteins. Drugmakers tend to develop biologic drugs to tackle these so-called protein-protein interactions, because these interactions don’t usually have the kind of well-defined pockets a small molecule can wedge its way into- they come together more like two marshmallows as opposed to two LEGO bricks.

Given that knowledge I asked medicinal chemist Michael D. Taylor, Ensemble’s president and CEO, about the nature of the 8 key targets in the BMS collaboration. “Macrocycles are useful for a variety of different targets,” Taylor says. “We’ve always thought that protein-protein interactions are an area or particular importance and our partners have emphasized protein-protein interactions within the collaborations that we have, so it’s fair to say that the vast majority of the targets fall in that area.”

Ensemble’s press release about the milestone also mentions that the company has made improvements to its platform to boost output as well as druglike qualities in its libraries of macrocycles. I asked Ensemble’s chief scientific officer Nick K. Terrett, also a medicinal chemist, to elaborate. He says the changes come in two areas- first, to the company’s DNA-guided discovery platform, and second, to the organic chemistry used to make discrete macrocycles (macrocycles sans DNA) for further testing. In the first area, the company has made very specific improvements in how they do chemistry on DNA, which has increased speed and has lowered cost per compound synthesized from just under a dollar in 2009 to nine cents today. They’ve also designed a new scheme for programming a chunk of DNA to encode specific bits of a macrocycle.

In the second area, making discrete compounds without DNA, the operation usually involves solid phase chemistry. Here, the team has changed reagents to cut costs and improve yields.

Terrett and Taylor emphasize that Ensemble’s role isn’t just hit-finding. The new improvements to both parts of the platform help Ensemble start with the most diverse set of macrocycles possible, they say. They also help chemists take hits that emerge from screening those diverse macrocycles and develop them into leads with druglike properties, such as oral bioavailability-the ability to be absorbed in the body when taken orally. “We drove all the chemistry up to this point,” Taylor says. “Now BMS can pick up and run with it.”

More reading: “The exploration of macrocycles for drug discovery — an underexploited structural class”,
Driggers, Terrett, et al, Nature Rev. Drug Disc., DOI: 10.1038/nrd2590.

View the original article here