Fast, cheap, and accurate: Detecting CO2 with a fluorescent twist

Detecting specific gases in the air is possible using a number of different existing technologies, but typically all of these suffer from one or more drawbacks including high energy cost, large size, slow detection speed, and sensitivity to humidity.

Overcoming these deficiencies with a unique approach, a team based at Kyoto University has designed an inexpensive new material capable of quick and accurate detection of a specific gas under a wide variety of circumstances. Moreover, in addition to being reusable, the compound gives off variable degrees of visible light in correspondence with different gas concentrations, providing for development of easy to use monitoring devices.

The findings, published in a recent issue of Nature Materials, describe the use of a flexible crystalline material (porous coordination polymer, or PCP) that transforms according to changes in the environment. When infused with a fluorescent reporter molecule (distyrylbenzene, or DSB), the composite becomes sensitive specifically to carbon dioxide gas, glowing with varying intensity based on changing concentrations of the gas. Lead author for the paper was Dr. Nobuhiro Yanai of the university's Graduate School of Engineering.

"The real test for us was to see whether the composite could differentiate between carbon dioxide and acetylene, which have similar physiochemical properties," explains Assoc. Prof. Takashi Uemura, also of the Graduate School of Engineering. "Our findings clearly show that this PCP-DSB combination reacts very differently to the two gases, making accurate CO2 detection possible in a wide variety of applications."

In its natural state, DSB is a long, flat molecule, which emits a blue light. When adsorbed by the PCP framework, DSB molecules twist, causing the entire PCP structure to also become skewed. In this condition, the glow of DSB diminishes significantly.

"On this occasion we observed that the presence of CO2 causes the DSB molecules to revert to their flat, brightly fluorescent form, while also returning the PCP grid to its usual state," adds Professor and deputy director Susumu Kitagawa of the university's Institute for Integrated Cell-Material Sciences (iCeMS). "And importantly, these steps can be reversed without causing any significant changes to the composite, making possible the development of a wide variety of specific, inexpensive, reusable gas detectors."

More information: "Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer" by Nobuhiro Yanai, Koji Kitayama, Yuh Hijikata, Hiroshi Sato, Ryotaro Matsuda, Yoshiki Kubota, Masaki Takata, Motohiro Mizuno, Takashi Uemura, and Susumu Kitagawa, Nature Materials, Published online on September 4, 2011.

Provided by Kyoto University

SNS, HFIR experiments help refine thin-film solar cells

 Solar cells that convert sunlight into electricity could be a widely used renewable energy source. Getting to that point, though, requires breakthroughs in their cost and their efficiency at turning sunbeams into electric current. Neutron scattering experiments conducted at Oak Ridge National Laboratory are helping solar cell makers obtain the hard data they need to refine their materials and manufacturing processes.

One of the most promising options for lowering costs is to make solar cells from thin films made up of combinations of plastics called polymers. These devices are easy to produce in large numbers because they use conventional industrial processing methods, which are relatively cheap and energy-efficient compared to the processes used to make the silicon solar cells that are most widely used now. Also, panels made from organic solar cells are lighter and less expensive to install than the bulky solar panels made from silicon cells.

The drawback to these easily fabricated thin-film devices is their power conversion efficiency, or how well they convert solar radiation to electricity. They're much less efficient than silicon cells (which are almost 30 percent efficient). To be inexpensive enough to compete with silicon cells, thin-film solar cells must be more than 10 percent efficient, but so far, the best ones are only about 8.3 percent efficient. To make solar cells efficient enough, scientists need to understand the molecular structure of the thin films they're made of, how the structure relates to the efficiency of the solar cell, and how to tailor the structure for the greatest efficiency.

Recent studies of polymer-based solar cells at ORNL's Spallation Neutron Source and High Flux Isotope Reactor revealed important details about their molecular structure and showed that annealing (heat treating) the devices improves their power conversion efficiency. The experiments showed that annealing solar cells appropriately as they are fabricated improves their efficiency by more than 20 percent compared to films that aren't annealed.

"We are trying to use mixtures of photoactive polymers to absorb light over a broad wavelength range to improve efficiency," said principal investigator Thomas Russell of University of Massachusetts-Amherst. Haiyun Lu of U-Mass and Bulent Akgun of the NIST Center for Neutron Research and the University of Maryland are co-investigators. Studies such as this one are key to improving the performance of polymer-based solar cells so that they can compete in the marketplace.

The device studied consisted of two semiconductor materials deposited in a thin film on an underlying plate. The films were examined in their original state after being deposited and then after annealing. The MAGICS magnetism reflectometer at the SNS investigated the vertical arrangement of the layers in the film, and the General Purpose Small-Angle Neutron Scattering instrument at HFIR showed how well the two semiconductors blended.

"Structural characterization of thin films has always represented a challenge for small-angle neutron scattering," said Yuri Melnichenko, lead scientist at GP SANS. A powerful neutron beam is needed to monitor the subtle structural changes that occur during the formation of the film, and HFIR provides one of the strongest neutron beams for SANS in the world. The experiments at HFIR were completed within approximately 24 hours, while similar measurements at less intense neutron sources would require five to seven days, Melnichenko said.

How well the semiconductor materials in the thin film blend is important to their performance. The measurements on MAGICS showed that the blending of the two semiconductors increased steadily as the sample was annealed for up to one minute, said Valeria Lauter, lead scientist for MAGICS. As heating continued beyond one minute, there was little further change in the blending.

The experiments determined that annealing the solar cell at 150 degrees Celsius for one minute at a particular point in the process improved its efficiency by slightly over 20 percent compared to the original film. Annealing for shorter times improved the efficiency by lesser amounts. Annealing for more than a minute caused it to decline, as did annealing it at a different point in the process.

The work is detailed in the paper "Morphological characterization of low-bandgap crystalline polymer: PCBM bulk heterojunction solar cells," in Advanced Energy Materials, available online at http://neutrons.or … _russell.pdf

Provided by Oak Ridge National Laboratory (news : web)

Coffee could offer key ingredient for new treatments for Parkinson's disease

Scientists from Heptares Therapeutics have used Diamond Light Source, the UK’s national synchrotron facility, to understand the structure of a protein involved in Parkinson’s disease and other neurological disorders. Their findings, published this week in the journal Structure, could pave the way for a new generation of targeted drug treatments.

The team used Diamond’s Microfocus Macromolecular Crystallography (MX) beamline (I24) to reveal the complex structure of the vital adenosine A2A receptor and show how xanthine-based drugs such as caffeine bind to their target. Adenosine A2A receptors regulate the effects of neurotransmitters in the brain, cardiovascular and immune systems, and are of particular interest as a drug target for Parkinson’s disease. Although it was known that caffeine inhibits the action of the adenosine, the exact molecular mechanism involved was not fully understood.

“These co-structures of xanthines in complex with the adenosine A2A receptor advance our understanding of what is happening at the molecular level when the drug binds to its target and blocks the receptor’s response. Along with novel chemotypes discovered by our team, the structural data we collected at Diamond is enabling us to develop highly optimised next-generation drug candidates for Parkinson’s disease and other neurological disorders,” said Dr. Fiona Marshall, Chief Scientific Officer at Heptares.

The adenosine A2A receptor is a G-protein-coupled receptor (GPCR). GPCRs are responsible for transmitting chemical signals into a variety of different cell types. There are over 700 GPCRs encoded in the human genome and as many as 75 of these have clinical validation, presenting a wide range of opportunities as therapeutic targets in areas including cancer, diabetes, central nervous system disorders, obesity and pain.

Dr. Andrew Doré, Senior Scientist at Heptares, says: “GPCRs represent the single most important family of drug targets in the human body because they are central to so many biological processes. The design of drugs for GPCRs is hampered by the lack of structural information so access to a facility like the Diamond synchrotron is vital to our research. It has enabled us to solve the 3D structure of the adenosine A2A receptor in complex with caffeine and other xanthines as well as our own novel drug candidates.”

Caffeine is a methylxanthine, a stimulant derivative of xanthine, as is theophylline (in tea), and theobromine (in chocolate).  Methylxanthines are among the most widely consumed substances in the world. Caffeine is present in many foods and drinks and reportedly consumed at an average rate of 200mg per day by Americans (Ref. 1). In 2000, the Journal of the American Medical Association (JAMA) published research showing a correlation between higher intake of caffeine and lower incidence of Parkinson’s disease, a devastating and incurable neurological disorder (Ref. 2).

While caffeine exerts a broad range of adverse effects, and is therefore poorly suited for use as a drug, pharmaceutical researchers have generated more potent and selective adenosine receptor modulators. A2A receptor antagonists, in particular, have shown clinical efficacy in the treatment of Parkinson’s disease. First generation A2A antagonists using older furan and xanthine type chemical structures have been associated with various safety, tolerability, and pharmacokinetic limitations. Heptares have used structural information to generate the next-generation of A2A antagonists.

More information: Structure of the adenosine A2A receptor in complex with ZM241385 and the xanthines XAC and caffeine. Doré, AS et al. Structure (2011) 19, 1–11. doi:10.1016/j.str.2011.06.014

References:
Daly, GW. Caffeine analogs: biomedical impact. Cell. Mol. Life Sci. (2007) 64(16), 2153-2169
Ross, GW et al. Association of Coffee and Caffeine Intake with the Risk of Parkinson’s Disease. JAMA (2000) 283(20), 2674-2679

Provided by Diamond Light Source

Cutting edge research results with a click of the mouse

With its new search facility and directories of scientific publications from numerous journals in chemistry, pharma, life science and related disciplines, CHEMIE.DE Information Service GmbH now offers unparalleled access to scientific data, providing convenient filtering options for a truly unique search experience.

More than 200,000 scientific papers from several hundred journals, along with their bibliographic data and abstracts, are now searchable on the portals chemeurope.com and bionity.com. Results can be refined by specifying one or more subjects or industry sectors, because the articles have been categorised. By successively adding subject filters, highly complex searches can be conducted. For instance, if a search for a substance or pathogen yields a long list of results, it takes just a few mouse clicks to narrow these down to display only those results that relate to certain analytical or chemical methods, or to a specific subject.

Users can regularly access the bibliographical data and abstracts of the papers they find. Open access journals and publications to which the user has subscribed allow articles to be retrieved from the publisher's website in full text.

While conventional literature searches provide only scientific papers, users of the CHEMIE.DE portals can also find other content, such as news items, whitepapers, market studies and event notifications. The new search facility thus yields not only insular scientific results but also various other items relating to the search terms, providing a more comprehensive picture. A search for EHEC (enterohemorrhagic E. coli), for instance, may spawn anything from an encyclopaedic definition to current news items and relevant products, to scientific papers, all displayed at a glance on a single portal.

"With our new search facility for scientific publications we have further enhanced the information we offer to the scientific community," Dr Björn Lippold, Chief Content Officer at CHEMIE.DE, explains. "The most significant advantage of our new search facility over those that focus purely on scientific literature is that it yields a host of valuable, additional information. Results include current news items, scientifically relevant organisations and more, ranging from basic to specialist information and from scientific theory to business data, thereby conveying a comprehensive picture."