Carbon nanotubes in large panel displays

28 April 2011

US researchers have incorporated carbon nanotubes into organic light-emitting transistors (OLETs) to create devices that rival the performance of their silicon counterparts. This technology could lead to much larger flat screen televisions and displays, which are also cheaper to manufacture.

Organic light-emitting diodes (OLEDs) produce brighter light than liquid crystals and are cheaper to make than inorganic LEDs. This makes them a promising alternative for large flat screen displays.

Polycrystalline silicon transistors - semiconductor devices used to amplify and switch electronic signals - are used to make up the backplane of OLED electronic displays. However, it is difficult to make uniform polycrystalline silicon grains and this limits the size of display you can make.

Bigger, cheaper flat screen televisions could be on the cards thanks to an organic device that is both a light source and a transistor

Now a team of researchers, led by Andrew Rinzler at the University of Florida, Gainesville, has tackled this problem by adding a thin network of carbon nanotubes to a transistor. This transistor can perform the switching functions an electronic display needs at very low voltages. 'The goal is to allow people to build bigger screens. We have opened up the field to be able to exploit a whole new class of materials in these devices, to overcome the limitations of polycrystalline silicon,' says Rinzler.

The team took the design one step further and incorporated an OLED layer into the carbon nanotube-based transistor to produce an efficient OLET - a device that acts as both a transistor and light source for an electronic display. The device comprises a network of carbon nanotubes mounted on a thin dielectric layer. The device is sandwiched between two electrodes and the organic light emitting material sits on top.

Passing a small current through the device provides enough power to produce different coloured light. By adding different organic semiconductors the team were able to produce red, green or blue light without the need for a separate transistor and OLED.

'This concept has the potential to significantly improve OLED display resolution, increase panel size and reduce power consumption,' says Maxim Shkunov, an expert in organic electronic materials at the University of Surrey, UK. 'However, the realisation of this concept will need to be confirmed by display manufacturers.'

Rinzler believes that his OLET design could be commercialised in the near future. His team plan to build arrays of OLET-based pixels to check that the carbon nanotube technology can be scaled up for big screens. 'Our goal is really to demonstrate all the pieces for a display manufacturer to look at this technology seriously,' he says.

Mike Brown

RSC

New method for aromatic coupling

28 April 2011

Chemists in Switzerland have developed a way to couple aromatic rings through the Friedel-Crafts mechanism - something many people would have believed impossible. Furthermore, the method involves activating the highly stable bond between an aromatic carbon and a fluorine. So far the method only works for aromatic sites in the same molecule, but the team believes that the underlying concept could allow for couplings between discrete molecules.

The Friedel-Crafts reaction enables alkyl or acyl groups to be attached to an aromatic ring via the generation of a carbocation that attacks the ring's electron-rich pi clouds. Coupling two aromatic rings in this way has been problematic because of the instability of the phenyl cation. Instead, aromatic coupling - a hugely important reaction in the fine chemical and pharmaceutical industries - is usually carried out via palladium catalysts.

Aromatic rings can be coupled with the help of a silyl cation

Now, Jay Siegel's team at the University of Zurich has shown that an aryl halide can be coaxed to participate as an electophile in Friedel-Crafts reactions. The precursor molecule for the reaction is a polyaromatic containing a strong C-F bond. However, the bond between silicon and fluorine is even stronger. The researchers showed that when the C-F bond is exposed to a silyl cation - R3Si+ - the fluorine hops off the ring to join with the silicon. This would leave an aryl cation, were it not captured by its neighbouring ring, thus coupling the two rings. The proton that is released is then reacts with a silane to regenerate the silyl cation and repeat the cycle.

Siegel says that the technique could be used to make finely tuned fragments of graphene - sheets of carbon one atom thick. Large numbers of fluorinated polyaromatic precursor molecules could be bolted together by conventional methods, then the new method used to knit-up the 'loose ends'. 'If you bring many molecules together you end up with effectively a tattered sail, says Siegel. 'We can knit this together to make a single contiguous sheet of very specific geometry.' Fluorine is useful in this context, rather than the other halogens, because it is much smaller and so more suited to a sterically congested environment where fine control over molecular geometries is being sought.

The team is now looking into the possibility of coupling aromatic sites from separate molecules. To carry out this reaction the various intermediate species need to survive long enough for the relevant collisions to occur. 'We have some ideas of how we might tackle this,' says Siegel.

Scott Denmark at the University of Illinois in the US, is impressed and describes the approach as 'ingenious', adding that 'the accomplishment is particularly remarkable because it engages the least reactive of all the aryl halides, namely aryl fluorides. This new transformation allows ready access to important polyarene structures and opens vistas for exploration of novel chemical reactivity.'

Simon Hadlington

RSC

Polymer collapses in a flash

28 April 2011

Researchers in the Netherlands have created a polymer that folds up like a protein on exposure to light.1 Non-covalent interactions are responsible for the collapse of the polymer, but while hydrophobic interactions drive protein folding, hydrogen bonding folds the polymer.

'Natural polymers, like proteins, are functional due to their highly ordered well-defined three-dimensional structures,' says Tristan Mes of the Eindhoven University of Technology. Mes' synthetic polymer is packed with benzene-1,3,5-tricarboxamide (BTA) side chains that are connected by hydrogen bonds. Normally, these pull the polymer in on itself around a chiral centre of stacked BTA.

The polymer folds up in a flash when UV light frees it from its protecting groups
© Angew. Chem.

By photoprotecting the BTA with nitrobenzyl groups, the team added a trigger so that the folded polymer could only be obtained by external stimuli. Shining UV light on the polymer cleaves the protecting groups, causing it to fold up.

'By making use of photo-deprotection in combination with heating/cooling steps we can really control the folding,' says Mes. 'We have observed that the folding of these systems partly mimics protein folding.'

But Andrew Wilson of the University of Leeds, UK, says he is not so sure. 'I think what's really cool is that you get different degrees of H-bond mediated collapse depending on irradiation time and temperature - this hasn't really been demonstrated before and is of course a function of biological macromolecules.' But Wilson is unsure that folding is the right word for what the polymers do, explaining that pulling apart the polymer and allowing it to collapse will lead to a different superstructure each time, unlike proteins.

Mes and colleagues have also harnessed hydrophobic interactions in water to fold a BTA polymer intramolecularly.2 This folding bears a closer resemblance to that of the proteins which they are trying to mimic. In this case, these BTA polymers are wrapped around a catalytic ruthenium core to make a polymerisation 'enzyme'. Mes says the group now hopes to make artificial enzymes for asymmetric catalysis by using a chiral core of stacked BTA moieties.

Laura Howes
RSC

Hardy MOFs endure extreme conditions

28 April 2011

The most chemically and thermally stable metal-organic frameworks (MOFs) yet have been made by a team in the US. The MOFs could surpass zeolites as industrial catalysts.

Natural zeolites are porous alumina-silicate rocks used as catalysts in industrial processes. However, their pore sizes and surface functionalisations are difficult to alter, which limits their performance. MOFs - made by joining up metal oxide clusters with linking organic molecules - have similar structures to zeolites and are therefore of interest as alternatives. Until now, they have not been robust enough to withstand the conditions that zeolites undergo during industrial processes. Traditionally, MOFs have only been stable in temperatures up to 500 degrees Celsius, have low chemical stability and some even fall apart in water.

Jeffrey Long from the University of California, Berkeley, and colleagues have made MOFs that can withstand temperatures of 510 degrees Celsius and a pH range of 2 to 14. They made the MOFs by reacting a metal salt, such as nickel chloride or nickel nitrate, with trispyrazolylbenzene. The organic molecules were deprotonated and the functional groups were bound to the metal to create a three-dimensional network. 'We made four different compounds based on pyrazolate-type ligands,' says Long. 'They have very strong metal-ligand bonds, which make the porous solids extremely robust. Stability is important for real-world applications. You'd like to be confident that the compounds will survive for long periods of time under extreme conditions.'

The MOFs were made by reacting metal salts with trispyrazolylbenzene

To test the MOFs' ability to retain their structures under extreme conditions, the team heated them to over 500 degrees Celsius and boiled them in either a strong acid or a strong base for two weeks. 'The nickel compound was particularly robust. It was stable for pH 2-14, which hadn't been demonstrated before,' says Long.

'There are a couple of MOFs out there that are stable when you heat them, but the thing that's exciting about Long's compounds is that they have exposed metal sites,' says Russell Morris, who studies MOFs at the University of St Andrews, UK. Exposed metal sites make the reactive site more accessible, explains Morris.

'For catalysis, surface area is important because it dictates the number of catalytic sites you can have on your material,' says Long, who adds that his MOFs have higher surface areas than zeolites. He goes on to say that the MOFs could be used to improve catalytic processes, molecular separations and for storing compressed gas in high density.

Morris believes that the MOFs will be used to catalyse different reactions to zeolites. By putting a metal catalyst into a framework, it might change the way catalysis is done, he says. 'You've also got pores, which could have an effect on shape and size selectivity, which is interesting,' he adds.

Elinor Richards
RSC

Drug cocktails greater than the sum of their parts

27 April 2011

Canadian scientists have shown that combining an antibiotic that is past its prime with other drugs can give it a new lease of life. Pharmaceutical companies could use the systematic surveying technique employed to produce combinations of off-patent drugs that could tackle antibiotic-resistant bacteria. These drug combinations can also be patented - provided the mixture of drugs is non-obvious.

As bacteria become resistant to commonly used antibiotics, doctors often prescribe a combination of two antibiotics to ensure an infection is completely eradicated. Some bioactive, non-antibiotic drugs are known to work well with particular antibiotics, but most have been discovered serendipitously, not systematically.

A team led by Gerry Wright and Eric Brown at McMaster University, Canada, has performed the first systematic survey of off-patent bioactive drugs combined with antibiotics to treat bacterial infections. The team screened a sub-therapeutic dose of the antibiotic minocycline with over 1000 bioactive compounds, with startling results.

Just like the internet, bacteria are hard to kill by cutting just a single pathway

They found that a small dose of minocycline alongside loperamide, a well-known anti-diarrhoeal drug, killed eight species of bacteria. They also found other potent combinations, which killed related bacteria or just a single species.

Wright says that this work is commercially interesting as novel or non-obvious drug combinations can be patented. Little drug development should be needed, he adds, so these combinations could be used in the near future to treat stubborn infections.

The emerging area of systems biology will offer new ways to counteract antibiotic resistance, Wright says. 'Cellular pathways are not an unlinked set of railway tracks,' he says. 'They are more like the internet with lots of interconnections, so you can't shut them down just by hitting one point in the pathway; that would be like trying to shut down the internet from your home computer.' He adds that combinations of drug treatments will attack the microorganism at several points simultaneously, reducing the risk of resistance. Bioactive non-antibiotic drugs may affect any point in bacterial cell processes and may aid antibiotic transfer into the cell.

Esa-Matti Lilius, an antimicrobial immune response researcher at the University of Turku, Finland, has eagerly anticipated such a systematic study. However, he points out: 'You have to be sure that the drugs go to the right place in the body to be active together; drugs may function well together in the laboratory, but in a patient this is a different matter.' Animal tests by the authors are promising, he adds, and clinical trials should be the next step.

Carol Stanier

RSC

Multiple emulsion droplet design

27 April 2011

Scientists in China have developed a device that can control the production of multiple emulsion systems. This system could be used to encapsulate incompatible drug ingredients and to design multi-compartment materials, they say.

Multiple emulsions are liquid systems in which emulsion droplets are placed inside each other, each droplet smaller than the last, creating 'levels'. Microfluidic devices have been designed to produce such systems, but controlling the number, size and ratio of droplets at each level is difficult, especially when developing a system that has different types of emulsion droplets at the same level. Control over such multi-compartment levels would allow more precise encapsulation and the development of more advanced materials.

Liang-Yin Chu at Sichuan University and colleagues have designed a microfluidic device capable of producing multi-compartment multiple emulsions. Chu says: 'We hope the novel type of emulsions in our work will open a new gate for the applications of emulsions in the fields of template synthesis, synergistic delivery, micro reactions, bioassay and so on.'

Optical micrographs of monodisperse sextuple-component triple emulsions, containing one water-in-oil single emulsion and two oil-in-water-in-oil double emulsions

The team tested their system using different coloured oil droplets in water. The device - a droplet maker, connector and liquid extractor - can be arranged in different combinations to generate different emulsions. As the oil droplets move through the system, they merge in the main channel to form the multi-component emulsions.

Ho Cheung Shum, an expert in emulsions at the University of Hong Kong, in China, says: 'Such fine droplet engineering finesse creates new opportunities to explore topics such as reaction-on-demand, encapsulation of incompatible actives and templated assembly of artificial cell aggregates.'

Alberto Fernandez-Nieves, an expert in microfluidics at the Georgia Institute of Technology, US, is also impressed with the work. 'This beautiful work provides a very clever way to extend the applicability and uses of glass-based microfluidics,' he says.

The team now intend to explore the full potential of their device and promote its application in different areas.

Harriet Brewerton

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Pnicogens link up as new bond is discovered

26 April 2011

German researchers have discovered a chemical oddity - a new type of intramolecular interaction between group 15 atoms, which is as strong as a hydrogen bond. These interactions could be used to build supramolecular structures.

Pnicogens, group 15 elements, such as nitrogen and phosphorus, are well known for acting as Lewis bases, or electron donators. However, researchers at the University of Leipzig, Germany, have found that instead of repelling each other, two pnicogen atoms can attract each other, forming non-covalent bonds.

'Typically when you look at group 15 compounds, such as PR3, you would always regard them as a Lewis base,' says author Eva Hey-Hawkins. 'You would not expect two Lewis bases to interact because both have lone pairs of electrons.'

Group 15 compounds can form interactions as strong as hydrogen bonds

The team looked at how a number of known PR3 compounds interacted with each other. 'We calculated interaction energies and were astonished that they could be as large as hydrogen bonds - around 20 kJ mol?1,' says Barbara Kirchner, who led the theoretical study.

The team suggest the pnicogen atoms interact with each other by donating a lone pair into an antibonding P-R orbital of the other atom. While the lone pair itself is an area of negative charge, electrostatic potential calculations show that this is surrounded by a band of positive charge. 'This is the way you can imagine two molecules interacting - because there is both positive space and negative space,' says Kirchner. Preliminary calculations suggest nitrogen, arsenic and antimony behave in a similar way.

The researchers found that adding an electron withdrawing group perpendicular to the P-P axis decreases the interaction, while adding a good leaving group along the P-P axis increases the strength of the bond. However, Kirchner stresses that they have not yet studied enough compounds to be sure of these trends. 'At the moment I would be careful because if you put a hydrogen perpendicular to the P-P axis the trend can be inverted,' she says.

'I think it's quite interesting - it's an unexpected bonding,' says Bernd Engels, a theoretical chemist at the University of Würzburg, Germany. 'I think it's too early to say if there are consequences, but it's of interest for basic research.'

The researchers hope to use these new interactions, in place of hydrogen bonds, to build supramolecular structures, such as molecular machines. 'With phosphorus as one of the building blocks this could result in networks that have similar strengths as those based on hydrogen bonds,' says Hey-Hawkins. 'By using phosphorus you would have a broader way of varying the properties of donors and acceptors just by varying the substituents.'

Manisha Lalloo
RSC

Lignin cut down to size by nickel catalyst

21 April 2011

A nickel-based homogeneous catalyst that breaks down lignin - the tough polymer that forms plant cell walls - into useful building blocks suitable for chemicals, including green fuels, has been developed by US scientists. The team says that the nickel catalyst is more efficient than current heterogeneous catalysts, although industrial applications are still some way off.

The search for efficient biomass conversion methods to produce useful, green and sustainable products has gained much ground in recent years. However, a major obstacle has been that the main components of biomass - namely cellulose and lignin - are tough polymers that do not break down easily. Lignin comprises a network of ring-like monomeric nine carbon hydrocarbon units that are principally connected by C-O bonds. Cleaving these bonds without breaking open the individual ring structures is crucial to produce useful chemical building blocks, rather than a mixture of short chain hydrocarbons.

Lignin is found in abundance in biomass, but its complex structure makes it difficult to convert into useful chemicals

Previous systems for cleavage of aromatic C-O bonds in aryl ethers were based on heterogeneous catalysts that require high pressures and temperatures. Furthermore, these systems work by competing C-O bond cleavage and hydrogenation of the aryl ring, leading to complex mixtures, which wastes hydrogen.

Now, Alexey Sergeev and John Hartwig at the University of Illinois at Urbana-Champaign, US, have developed a homogeneous nickel-carbene catalyst which selectively cleaves aromatic C-O bonds in various aromatic ethers without reduction of aromatic rings or cleavage of aliphatic C-O bonds. In addition, compared with other catalytic systems, theirs functions at lower temperatures and pressures.

'We were surprised that such a simple catalyst is able to do such a challenging transformation of a number of unactivated aryl and benzyl ethers with such high selectivity,' says Hartwig. 'Because the catalyst is able to cleave aromatic C-O bonds in aryl ethers selectively, it could allow the production of nine carbon arenes from lignocellulosic biomass. These arenes can be used for the production of chemicals or, ultimately, green transportation fuels,' he adds.

'The challenge with lignin conversion is the selective depolymerisation of the carbon-oxygen linkages,' says George Huber who investigates biomass conversion at the University of Massachusetts, Amherst, US. 'This work offers an exciting new approach to cleave the carbon-oxygen bonds in lignin and could potentially open up a whole new area in biomass conversion.'

However, before the catalyst is ready for industry the system needs to be made more practical by decreasing catalyst loadings by several orders of magnitude. The catalyst's stability in the presence of moisture also needs to be improved as biomass tends to have a high water content.

James Urquhart
RSC

RNA analysis raises hopes of early cancer diagnosis

21 April 2011

An improved method for diagnosing colorectal cancer without using invasive techniques has been developed by scientists in China.

Colorectal cancer is one of the most common forms of cancer in the Western world

Colorectal cancer has become one of the most common forms of cancer in the Western world. Early diagnosis plays a key role in recovery from the disease, but this is hindered by the invasive techniques often needed. To address this, there has been increasing focus on finding ways to detect cancer cells excreted in faeces. A team led by Guohua Zhou at Nanjing University has now developed an improved method for detecting cancer-cell RNA in stool samples.

The team used a bead-based assay in conjunction with the polymerase chain reaction to detect the RNA produced by cancer cells. By using beads functionalised with multiple primers (to detect multiple RNA products), they were able to increase the detection rate by reducing the number of false negatives. They tested their method on stool samples from patients with colorectal cancer, and found a detection rate of 77 per cent, which Zhou describes as 'promising'.

A key advantage of analysing multiple genes simultaneously, says Zhou, is that 'it avoids the trouble of preparing different calibration curves for different genes'. He concludes that, although the sample size is not large, their work 'does give us hope of non-invasive diagnosis of colorectal cancer'.

Jennifer Hardingham, a specialist in molecular oncology at the Queen Elizabeth Hospital, Woodville, Australia, agrees with Zhou that the sample size needs to be increased, saying that use of a larger cohort 'will establish whether the sensitivity is sufficient for reliable detection of tumour cells in stool samples'. Nevertheless, she describes the method as 'highly innovative', and adds 'I look forward to the development of this technology in kit format for colorectal cancer diagnosis'.

David Barden
RSC

CO2 aids oxidation reactions

21 April 2011

Carbon dioxide enhances the catalytic oxidation of cyclic alkenes, leading to higher conversions at low pressures, say researchers from South Korea. The system could be a step towards new technology for using CO2 at low pressures.

Sang-Eon Park and coworkers from Inha University, Incheon, prepared carbon nitrides that contain surface groups to activate the CO2, which was then used to promote the oxidation reactions of several cyclic alkenes.

CO2 is being recognised as an alternative and economic resource for use in organic reactions and it has been used in catalytic reactions, either as a solvent or a reagent. However, in most cases, it is used in a dense phase or under supercritical conditions, which require high operating pressures and have low reaction rates.

Carbon dioxide is used to promote the oxidation reactions of several cyclic alkenes

The team tested their system by oxidising different cyclic alkenes with various amounts of oxygen, with and without CO2, and compared the results. They found that the presence of the CO2 increased the conversion percentage in all cases. The CO2 acts as an oxygen source, which is inferred from the formation of carbon monoxide and surface carbamate. The team was also able to reuse the catalyst up to three times.

Chang-jun Liu from Tianjin University, China, an expert in catalysis and the use of greenhouse gases, says that using 'high nitrogen containing carbon nitrides to enhance the oxidation of cyclic olefins with CO2 as a soft oxidant' is significant. Liu adds that the work could lead to an easy approach for CO2 conversion with the production of highly-valued chemicals.

Park's team now hopes to fully understand the reaction mechanism, explaining that this will help them to design a more appropriate catalyst. 'Further spectroscopic and computational studies are in progress and hopefully, very soon, a complete insight over promotional aspects will be revealed,' concludes Park.

Mary Badcock
RSC

Insecticide studies provide clues to bees' disappearance

21 April 2011

A rapid analytical technique could facilitate more extensive studies of the reasons for the worldwide decline in bee populations. Studies using the method suggest insecticides used to coat crop seeds may be partly to blame.

Neonicotinoid insecticides are used to coat crops such as corn and oilseed rape, and are one of several groups of chemicals identified as suspects in the disappearance of honey bees - a phenomenon referred to as colony collapse disorder. One theory is that the insecticides are passed to the bees in pollen.

Using ultra-high performance liquid chromatography, Andrea Tapparo at the University of Padua in Italy and colleagues now show that it is possible for bees to pick up a lethal dose of insecticide by grazing on sap produced by crop plants and present on leaf tops.1 Building on earlier work in 2009,2 the researchers show that concentrations of neonicotinoids present in drops collected from the leaves of corn plants are high enough to kill bees within a few minutes.


Bees could be picking up a lethal dose of insecticide by grazing on sap produced by crop plants and present on leaf tops

Although Tapparo doesn't think the mechanism they identify is the primary cause - noting that bee decline is probably due to many different factors - he says it can't be ignored. 'It must not be neglected that bees can be exposed to high doses of insecticides,' he says. 'The exposure scenario should be studied with particular attention.'

Galen Dively, an entomologist at the University of Maryland, US, doubts it is a major exposure route. 'Several Swiss studies and tests by Bayer CropScience indicate honey bees are not likely to forage for water to any significant degree in seedling corn, which overlaps with the spring nectar flow and at a time when rains are usually sufficient to provide other water sources,' he explains. 'Certainly the possibility of direct exposure exists but additional studies are needed.'

Crucial, though, is the method itself, which could facilitate much more widespread research into bee decline. Tapparo's team shunned more sophisticated chromatographic techniques involving mass spectrometry (HPLC-MS) in favour of an approach that would be faster and available to a broader range of researchers.

'I think for example, biologists, or students or teachers in the agronomic field, for them it's not possible to have direct access to mass spectrometer instrumentation,' says Tapparo. 'But HPLC is easier. And if we want to extensively study the mechanism involved with the neonicotinoids, we probably need a very simple analytical procedure.'

Hayley Birch
RSC

Putting the cement industry in the calcium loop

20 April 2011

Scientists in the UK have shown that two major industrial processes that generate large amounts of carbon dioxide could usefully be linked together to deliver significant savings in energy and CO2 emissions.

For several years researchers have investigated ways of capturing and concentrating CO2 from fossil fuel power stations so that it can be trapped, possibly in underground rock formations. One promising method involves reacting the flue gases with calcium oxide. The CO2 in the exhaust gas combines with CaO to form calcium carbonate, CaCO3. This can then be heated to drive off the CO2 at a much higher concentration. The process regenerates CaO, which can be used for further cycles. Typically flue gases contain around 15 per cent CO2, which can be concentrated to around 95 per cent through this 'calcium looping' process.

After repeated cycles the CaO undergoes morphological changes which reduce its efficiency for producing CaCO3. It has been suggested that this spent CaO could be used as a feedstock for the production of cement. The cement industry requires a large amount of CaO, which is produced by heating calcium carbonate in the form of limestone, which in turn produces significant CO2 emissions.

Carbon dioxide emissions from cement manufacture can be greatly reduced using calcium looping technology

However, it has not been clear if the CaO derived from the calcium looping cycle would be suitable for cement manufacture. Now, Charles Dean, Denis Dugwell and Paul Fennell, from Imperial College London, have carried out laboratory scale tests that suggest that spent CaO sorbent from CO2 capture retains the appropriate chemistry for its inclusion in cement, with no detrimental properties to the final product.

'If you take off a purge stream of calcium oxide from the calcium looping cycle, it should be possible to feed this directly into the cement works,' says Fennell. 'This would save about 50 per cent of the CO2 produced in production.' The requirement for less energy to generate the CaO from limestone would also create significant cost savings. 'We have shown for the first time that cement can be successfully produced from CaO previously used in the calcium looping cycle, thereby confirming a positive synergy between the two processes,' says Fennell.

Hannah Chalmers of the University of Edinburgh in the UK is a member of the Scottish Carbon Capture and Storage research group. She says successful application of CO2 capture to cement manufacture could be an important part of global efforts to reduce greenhouse gas emissions. 'This work includes important information for developing an understanding of the economic and environmental performance of CO2 capture from cement manufacture, which could be vital for successful development and deployment of this technology.'

Simon Hadlington

RSC

New clotting drug antidote could cut surgery risk

20 April 2011

Chemists in the UK have developed a possible alternative to protamine, a molecule used by doctors to counteract the effects of anti-clotting drugs. Unlike protamine, the new molecule should easily break down into less toxic metabolites, although it hasn't yet been tested in human blood or plasma.

Physicians often use anti-clotting agents to treat blood disorders, or to prevent blood clotting during surgery. One of the most popular anti-clotting agents is heparin, which has been used since the 1930s. But in order to combat dangerous overdoses of heparin, or to inactivate it after surgery is complete, physicians need a heparin binder. The only clinically approved heparin binder is protamine, but this agent sometimes causes severe allergic reactions, so scientists are keen to develop alternatives.

New molecule can bind heparin, counteracting its effects

Heparin is negatively charged, so the protamine alternatives developed so far have mostly been positively charged, like protamine itself. But positively charged polymers are often toxic, and these alternatives have proved unsuitable for clinical use. Now, however, David Smith and colleagues at the University of York have developed heparin binders that only temporarily become positively charged, so the risk of an allergic reaction is reduced.

The molecules developed by Smith's group contain hydrophobic units that self-assemble in water into spherical nanostructures of a similar size to protamine. These nanostructures have branches of positive charge to aid binding to heparin. Indeed, during in vitro tests in salt solutions, the protamine alternative was 'directly comparable to, if not a little bit better than, protamine,' says Smith.

'The interesting aspect of this work is that the designed heparin antidote is much smaller at a molecular level [than protamine].and is expected to bio-degrade to innocuous products, thereby functioning under in vivo conditions in a more predictable and less noxious manner,' says Umesh Desai, a medicinal chemist at Virginia Commonwealth University in the US.

Desai and other chemists say the molecule should have been tested in blood or plasma, where its effectiveness - and toxicity - may be different. Smith is already working on this to see whether biological fluids interfere with binding. 'Overall, I would say this is an interesting approach but with a long way to go to prove itself as a protamine alternative,' says Bob Linhardt, a heparin expert at the Rensselaer Polytechnic Institute in New York, US.

Jon Cartwright

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Clenbuterol scandal highlights the need for better testing

19 April 2011

By Hepeng Jia/Beijing, China

The illegal use of clenbuterol in porcine feed in China has led to an overhaul in Chinese food industry regulations and calls for scientists to develop more stringent testing techniques for the chemical.

Clenbuterol is a beta-2 agonist and sympathomimetic amine that is used to treat breathing disorders. When fed to livestock it accelerates growth and increases the proportion of lean meat. China began to use clenbuterol in pig feed in the late 1980s, but hundreds of people suffered from nausea, dizziness, hypertension and hyperglycemia after eating pork containing the chemical, and it was banned in 2002. According to Wang Zongli, from the Chinese Ministry of Agriculture, illegal use of clenbuterol is reducing year by year, but it has not been eliminated yet.

Clenbuterol is still used illegally in China to accelerate the growth of livestock

On 15 March, China central television (CCTV) reported that pork sold by Shuanghui, the country's largest meat producer, contained clenbuterol, sparking a nationwide campaign against the chemical's illegal use. By 8 April, a total of 95 people in central Henan Province, where Shuanghui is based, were taken into police custody for allegedly producing, selling or using clenbuterol. All meat product sales of Shuanghui have been suspended and the company has claimed total losses of up to Yuan20 billion (£1.9 billion).

The scandal was caused by farmers pursuing profits and slack regulations, says Chen Wen, deputy dean of the School of Public Health of Guangzhou-based Sun Yat-sen University.

According to Wang Zhixiang, a professor of veterinary science at Henan Agricultural University, random testing for clenbuterol by meat producers is carried out in the industry using a paper test and then positive results are confirmed with techniques such as gas chromatography mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). But the cost to test one pig is about Yuan30 while a meat producer's profit per pig is commonly only Yuan50, said Shuanghui's chairman Wang Long, when speaking to the Xinhua News Agency. As a result, the self random testing rate of meat producers is only 0.4 per cent while it is required to be 4 to 5 per cent of all pigs.

'If we want to eliminate the scandals, besides regulatory improvement, it is an urgent need to develop easier, cheaper, more convenient and wider-spectrum testing methods for regular food products,' Chen told Chemistry World.

RSC

Cell factories package drugs for delivery

19 April 2011

Scientists in Australia and Germany have used living cells as 'factories' to encapsulate particles such as drugs in biological membranes. The system could be used in the future as a biocompatible drug-delivery vehicle that could evade the body's immune and excretory systems, the scientists suggest.

Dayang Wang of the University of South Australia and Adelaide, and colleagues showed that certain hydrophobic molecules, including drugs and dyes, can diffuse across the membranes of cultured human or mouse cells. These molecules are then acted upon by enzymes in the cell to create the active hydrophilic product, which because of its water loving properties can remain in the cell's cytoplasm.

The capsules are released through protein channels in the cell membrane
© Nano Letters

The next stage is to parcel up these particles within much smaller membrane capsules. The researchers did this by exposing the cells a substance called cytochalasin B, which disrupts the internal scaffolding of the cell, its cytoskeleton. When the cells are then shaken, the membrane breaks up into many smaller hollow spheres, typically 1-2 micrometres in diameter, containing the introduced molecule.

The team showed that the membrane proteins, including receptors and ion channels, remain in the membranes of the smaller vesicles, and that these can, in certain circumstances, be stimulated by an appropriate biochemical cue to release the contents of the vesicle. The team showed that the vesicles can largely evade the attention of macrophages, cells which circulate in the blood and mop up foreign particles.

'We wish that in the future one could use cells directly from patients to encapsulate drugs, magnetic nanoparticles and other biological labels and inject these loaded capsules back into the patients,' says Wang. 'Since the capsules are derived from patients, there should be no clearance by macrophages or the renal system.'

Martin Garnett, a drug delivery expert from the University of Nottingham in the UK, says that the work is 'interesting in terms of how drugs can be loaded into containers produced from cell membranes and cytoplasm'. The fact that the capsules are not readily taken up by macrophages is also significant, he says. However, Garnett adds: 'As with other drug delivery systems the question of payload will have to be resolved. In the current paper the loading of drugs is dependent on having a hydrophobic drug which can be metabolised into a hydrophilic drug to retain it, and this may be applicable to only a small number of drugs.'

Simon Hadlington
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Shaping crystals with bio-tools

18 April 2011

Researchers in the US have developed a new approach for controlling crystal growth, borrowing tools from biology.

Some crystalline materials can behave very differently as catalysts depending on the crystal surface used, says Yu Huang of the University of California Los Angeles. 'If we were able to use biomolecules to produce just one particular shape, it would increase the efficiency of these catalysts.'

In the 'capping' method, crystals are shaped by binding molecules to preferred facets, inhibiting their growth and directing atoms to pack onto the uncapped facets.

The capping molecules must sense the subtle variations in the surfaces of different crystal facets. For instance, the atoms on the face of a platinum cube are in a face-centred cubic arrangement, but those on a tetrahedron are hexagonal. The discovery of such discriminating molecules has been haphazard, which has led Yu Huang of the University of California Los Angeles and her colleagues to propose a new approach.

© Nature Chemistry

Huang's team turned to biology's millions of years of experience in developing molecules with very specific binding tastes. They used a technique known as 'phage display', in which peptide sequences, from a library of a billion different combinations, are encoded into the DNA of viruses.

Those peptide sequences appeared as proteins in the virus membranes, and by exposing the viruses to a particular crystal facet, the researchers could discern how well they attached. The team selected two peptide sequences this way, one which bound to platinum cubes and the other to octahedra.

To make the crystals, Huang and her colleagues mixed chloroplatinic acid with peptides. A shot of sodium borohydride reduced the platinum ions suddenly, kicking off crystal growth. By the end of thirty minutes, 70 per cent of the crystals bound to the octahedron's peptide sequence had become tetrahedra, a shape with identical facets. The peptide for cubes had a similar success rate, forming crystals with 7.5nm dimensions.

Although the binding mechanism is unknown, the researchers conjecture that the aromatic group on the tetrahedron peptide may prefer the hexagonal formation of the platinum ions. They also suggest that oxygen of the hydroxyl groups at the end of the other peptide sequence may be bridging two adjacent platinum atoms on the cube surface.

Sara Skrabalak of the University of Indiana says the work could lead to highly reactive surfaces that are presently impossible to achieve in nanocrystals: 'It will be exciting to see how this approach develops.'

Kate McAlpine
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Delayed US budgets finally agreed

15 April 2011

Major chemistry funders in the US, including the National Science Foundation (NSF) and the Department of Energy (DOE) Office of Science, will see their funding shrink under the budget agreement covering the remainder of fiscal year (FY) 2011, which ends on 30 September. Brokered more than half a year late, the deal reached by Congress and the Obama administration on 8 April came just in time to avoid a government shutdown.

"Science agencies did pretty well in comparison with the others"
- Pat Clemins, American Association for the Advancement of Science

The Obama administration says it no longer plans to keep the budgets of the key physical science agencies on a trajectory to double between 2006 and 2016, but it is still vowing to provide them with 'strong investments'.

Under the long-awaited arrangement, the NSF will have a $6.9 billion (£4.2 billion) budget, representing a $53 million drop compared with the previous year. The figure is $550 million under the President's request but $307 million over the original House proposal. Specifically, the NSF research accounts will be shaved by $43 million, or 0.8 per cent, and the education and human resources budget cut by $10 million, or nearly 12 per cent.

Meanwhile, the DOE Office of Science was spared the billion dollar reduction proposed by the House. Instead, the office - which funds the US national laboratories - will see its budget fall to $4.9 billion, representing a drop of $20 million.

The US National Institutes of Health (NIH), which under the House proposal would have lost $1.6 billion, will receive a $31 billion budget, representing a decrease of $260 million, or 0.8 per cent. Specifically, $50 million is being taken from the agency's buildings and facilities account. Congress has approve these final appropriations for FY2011.

'It could have been much worse, but overall science agencies did pretty well in comparison with the others,' says Pat Clemins, who heads the budget and policy programme at the American Association for the Advancement of Science. For example, the Environmental Protection Agency saw its funding slashed by $ 1.5 billion, or 16 per cent. 'Now it is up to the scientific community to show that this was a good idea and to spend the money wisely,' Clemins adds.

The American Chemical Society (ACS) has already turned its attention to the FY 2012 budget and beyond. The House Budget Committee blueprint for FY 2012 contains what appears to be predictable and sustained funding for many of the US science agencies. But those plans now appear to be in doubt. Spokesperson Glenn Ruskin says the ACS is 'taking a wait and see approach'.

Rebecca Trager, US correspondent for Research Europe

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DNA origami yields tiny flask

14 April 2011

A US group of researchers has made a round bottomed flask from folded up DNA with an internal capacity of just 24000nm3, which would be enough to hold 800,000 molecules of water. The flask is 70nm high and 40nm wide and was made by stacking different sized rings of DNA on top of each other - the way in which so-called coil pots are made out of clay.

'We are inspired by both Nature and engineered architectural objects' says Hao Yan, one of the group members at Arizona State University, US. Yan says Nature is full of objects with delicate curvatures.

Scientists have used DNA 'origami', in which DNA is used as a structural material, to make rings before. But varying the size is difficult because DNA prefers circles with 10.5 base pairs per turn, and stacking those would just give a tube. Yan and colleagues found a way to control the folding of DNA to make bigger and smaller rings, as well as half rings, and used those to build up their 'nanoflask'.

© Dongran Han / Science

Yan Lui, another of the researchers involved in the study, explains that although DNA helices are thought of as straight lines, they are quite soft and flexible and can easily be bent and twisted: 'With designed crossover points at desired positions, DNA helices can be linked together so that different sized curvatures in and out of the plane can be achieved.'

Paul Rothemund at California Institute of Technology, US, who did much of the early work on DNA origami, says he is impressed by the flask. Research on DNA structures is moving very fast, he adds.

Of course, flasks made from DNA are unlikely to replace traditional glassware in the lab, but Yan and Lui say that the technique could be used to make templates for nanocrystals, artificial enzymes or capsules for drug delivery.

The team is now also working to make more elaborate structures from longer lengths of DNA, but they say that, for that, the pen and paper they've been using up until now might have to be traded in for computer-aided design software.

Laura Howes

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Fish in chips: growing embryos in microfluidic systems

14 April 2011

Scientists in the Netherlands and the UK have shown for the first time that an animal embryo can develop in a microfluidic environment. Their discovery could find application in high-throughput, low-cost assays for drug screening and life sciences research.

Zebrafish embryos are becoming important animal models, bridging the gap between cell culture assays and whole animal testing, and have found use in disease modelling and drug safety prediction assays. These assays are currently performed in microtitre plates and require periodic replacement of the buffer solution, which can cause stress or damage to the embryos. Now, Michael Richardson, from Leiden University, and coworkers have developed a microfluidic lab-on-a-chip device in which the buffer solution can flow continuously through the system, and have successfully raised zebrafish embryos under these conditions.

The team made the device from three layers of borosilicate glass with an array of temperature-controlled wells connected by channels; each well houses a single zebrafish embryo. The growth and development of embryos in the microchip was investigated following a five-day culture. Some minor phenotypic variations, such as reduced body length, were found in the microchip-raised embryos; however, there was no significant increase in other abnormalities compared with control experiments.

More than 100 embryos could be cultured in an area smaller than a credit card

They demonstrated the device's potential for application in drug screening assays by releasing ethanol into the wells to induce embryonic abnormalities. The small volume of the microchip wells (10ul) means that short exposure experiments will consume far less reagent than traditional drug screening assays. 'This makes the biochip promising for drug discovery in which only small quantities of compound are available, or in which the compound is very expensive,' says Richardson.

'We have a limited repertoire for automating many of the processes of drug discovery,' remarks Randall Peterson, an expert in zebrafish chemical genetics at the Cardiovascular Research Centre, Massachusetts General Hospital, US. 'This work helps to further the goal of making tools accessible for high-throughput studies and as we gain more tools like this, we can accelerate the pace of discovering new drugs.'

Richardson and his colleagues are now working on validating the new technology, performing screening assays with existing drugs. The next challenge will be to enable compatibility between the microchip and the machinery currently used by pharmaceutical companies in automated screening assays. Richardson also hopes that the system could be used in other applications, such as 3D cell culture and mammalian tissue growth and regeneration.

Sarah Farley

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Microrockets aim at cancer diagnostics

13 April 2011

Researchers at the University of California, San Diego, have made self-propelled microtube rockets that can find and capture cancer cells from blood samples.

The researchers say that these 'microrockets' could make an effective diagnostic tool. And blood samples would not need significant pre-treating, unlike samples for other micro-diagnostic methods. 'We showed for the first time that this microtube rocket can propel in biological fluid,' says nano-engineer Joseph Wang, whose team joined forces with that of cancer researcher Liangfang Zhang.

The microrockets run on hydrogen peroxide fuel added to a biological sample. Platinum on the inside of the tube catalyses the splitting of hydrogen peroxide into water and oxygen, and the tapered tube is driven forward as the oxygen gas leaves through the wider back end. Iron layered between the inner platinum and outer gold coatings allows researchers to steer the microrockets with magnetic fields.

The functionalised microrocket picks up cancer cells as it travels along
© Angew. Chem., Int. Ed.

The team made the rocket specific for cancer by adding antibodies for a protein commonly found on colorectal, gastric and pancreatic cancer cells to the gold surface of the tube, making the receptor highly selective - it won't bind to other cells.

Samuel Sanchez and his colleagues at the Leibniz Institute for Solid State and Materials Research in Dresden, Germany, developed this 'microbot' design, and he says he is pleased to see another group making use them.

The Californian team tested the microtubes in saline solution and human blood serum. In human serum, the rockets captured their pancreatic cancer cell targets 70 per cent of the time and could still move about while carrying their cellular cargo, with only a small drop in speed.

Sanchez says this work could 'help our community to believe that these tiny machines have real biomedical applications'.

Wang suggests that future nano-machine enabled cancer diagnostics could be as simple as adding hydrogen peroxide to a blood sample, using the magnetic field to guide the tiny rockets on several passes through the fluid and then examining the rockets for captured cancer cells with an optical microscope.

'This technology has the potential to not only isolate circulating tumour cells (CTCs) from suspension but to manipulate the subsequently captured CTCs in a precise manner,' says Shashi Murthy of Northeastern University in Boston, US. This would allow the cells to be collected and concentrated for further analysis, he adds.

Kate McAlpine

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Full steam ahead for China's nuclear development

13 April 2011

By Hepeng Jia/Beijing, China

As the nuclear crisis at the Fukushima Daiichi nuclear power plant in Japan escalates and continues to be the cause of worldwide concern, China is unlikely to stop its ambitious plan to expand its nuclear industry.

'The [Fukushima] accident will impact nuclear development worldwide, but in my opinion, it will not influence China's overall nuclear strategies,' said Zhang Guobao, newly retired director of China's National Energy Bureau at a seminar on low-carbon energy in Beijing, on 24 March.

In response to the crisis, the Chinese premier Wen Jiabao asked for nuclear facility safety across China to be completely scrutinized and for the approval of new nuclear plants to be suspended. He also ordered that a national plan on nuclear safety should be drafted.

China has 13 operating nuclear power reactors, with another 20 currently under construction. With this massive development, the installed nuclear power capacity will reach 80 million kilowatts by 2020, meaning nuclear power will contribute seven per cent to China's total power supply within 10 years.

China's plan to reduce carbon emissions cannot be met without massive development in nuclear power

Compared with the nuclear facility in Fukushima, China's reactors are thought to be much safer. Natural disasters like earthquakes and tsunamis will not destroy their cooling systems, said Pan Ziqiang, China's top nuclear safety expert from the China National Nuclear Corporation (CNNC), at a media workshop on 25 March. 'To take a more cautious attitude after the Japan accident will be good for the healthy development of the nuclear industry,' he added.

China, the world's largest carbon emitter, has promised that by 2020, its carbon emissions per unit of gross domestic product (GDP) will be reduced by 40 to 45 per cent compared with 2005 values, and it is widely believed that this goal cannot be achieved without massive development of nuclear power.

However, the safety audit of nuclear facilities planned by Wen Jiabao and the suspension on approving new reactor construction could highlight other unknown problems. According to leading business newspaper 21st Business Herald, the three nuclear energy groups, CNNC, China Guangdong Nuclear Power Holding Corporation (CGNPC), and China Power Investment Corporation (CPI), have obtained a total of Yuan800 billion (£75 billion) in bank credits. If any of the reactors under construction are halted due to safety concerns, or have poor operation records after completion, the banks will risks losing their earlier loans.

'In a sense, while reviewing safety issues, the current caution of policymakers can help people rethink the possible regulatory, technological and commercial shortcoming of China's nuclear power projects,' says an industrial insider who refused to be named.

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Nanofiltration for better energy storage

13 April 2011

Scientists in China have found that nanofiltration membranes could enhance the efficiency of vanadium redox flow batteries (VRBs) making them a more viable tool for large-scale energy storage.

Xianfeng Li from the Chinese Academy of Sciences in Dalian and his team made the membranes, which separate two components in the batteries, from polyacrylonitrile. Pores in the membrane can be adjusted, allowing scientists to have more control over the ions passing from one side of the battery to the other during charge-discharge cycles, improving the battery's performance.

The nanofiltration membrane lets protons through but not vanadium ions

The random and intermittent nature of renewable wind and solar energy sources can limit the power output quality, says Li, who adds that 'energy storage is the key to solving this problem.' VRBs can store a significant amount of energy. In these batteries, two electrolyte tanks, containing species of vanadium in different valance states, are separated by an ion exchange membrane. When the battery is charged, the vanadium ions are oxidised or reduced, converting chemical energy into electrical energy.

Ion exchange membranes should prevent the crossover of vanadium ions, while allowing protons to pass through. But the ones most commonly used - perfluorinated polymers such as Nafion - let vanadium ions through and are expensive to buy, despite showing high proton conductivity and chemical stability. Other low-cost membranes need additional ion-exchange groups, which lower their stability. The difficulty in finding a suitable membrane has limited the commercialisation of VRBs, Li explains.

The team adjusted the polyacrylonitrile membrane's pore size distribution by varying the polymer concentration. They measured their membrane's selectivity between vanadium ions and protons by placing the membrane in a cell with vanadyl sulfate in sulfuric acid on one side and deionised water on the other. They collected samples from the right side over time and analysed them with a UV-visible spectrometer and a pH meter. They found that the membrane showed increased selectivity for protons over vanadium with a smaller pore size distribution. They observed that the performance was comparable to Nafion, but at a lower cost.

John Varcoe, who develops systems for clean and sustainable energy generation at the University of Surrey, UK, says that using nanofiltration membranes in redox flow batteries is 'an exciting new development in the field'. 'The simplicity of the system does not lead to a sacrifice in performance and efficiency,' he adds, but he points out that further stability tests are needed.

Fay Nolan-Neylan

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China sets modest energy saving plan

12 April 2011

Hepeng Jia/Beijing, China

After forced power cuts last year in a bid to save energy, China has released more realistic figures on energy saving and carbon emission reduction.

The 12th five-year (2011-15) energy development plan, announced on 15 March, promises to cut energy consumption by 16 per cent per unit of gross domestic product (GDP), compared with 2010, as well as cutting carbon dioxide emissions by 17 per cent per unit of GDP, all by the end of 2015.

From 2006 to 2010, China reduced its energy consumption by 19.1 per cent from 2005 levels, close to the 20 per cent target that was set. 'As compared with the previous five-year plan, the 16 per cent [energy intensity reduction] is modest and more realistic,' says Wang Yi, an energy expert and deputy director of the Institute of Policy and Management, at the Chinese Academy of Sciences.

At the Copenhagen climate change conference in 2008, China promised to cut carbon emissions by 40 to 45 per cent for every unit of GDP by 2020 compared with 2005 levels. 'If the 16 per cent goal is finished by 2015, then the 40 per cent emission cut per unit of GDP by 2020 is easier to realise,' Wang told Chemistry World.

China will still emit more than 10 billion tonnes of carbon dioxide in 2015, the same as the US and EU combined

The national energy plan is divided into different regional goals. For more advanced regions like Shanghai and Jiangsu, the goal is to cut 18 per cent, and for Beijing, it is 17 per cent. But for the least developed Chinese regions the target is 10 per cent.

The 12th five-year plan also stipulates that non-fossil fuels should account for 11.4 per cent of the total energy consumption, but it does not mention China's total energy consumption goal for 2015, which is widely believed to be 4 billion tonnes of standard coal. This means, despite the energy saving efforts, China will still emit more than 10 billion tonnes of carbon dioxide (one unit of standard coal is equal to 2.6 units of carbon dioxide) in 2015, the same as the US and EU combined.

Hu Jinglian, a senior expert at the Energy Research Institute of the National Development and Reform Commission in China, thinks that even reducing by 16 per cent per unit of GDP, is still a difficult target to reach. 'It will depend on the growth rate of GDP. If it is kept as high as 10 per cent annually, it will be a great challenge to cut energy intensity,' Hu says. She adds that China should have a national government agency to make a comprehensive energy saving plan, rather than simply setting a target.

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How antidepressants spur brain growth

12 April 2011

Researchers have identified the mechanism by which some antidepressants stimulate the formation of new brain cells, an insight that could lead to improved drugs.

Antidepressants combat depression by increasing levels of serotonin in the brain. But they can also help by stimulating the formation of new brain cells, a process called neurogenesis, which plays an important role in memory.

Depressed patients are thought to release greater amounts of glucocorticoid stress hormones, such as cortisol, which reduce neurogenesis, causing symptoms such as impaired memory and low mood. Previous research has shown that antidepressants block the effect of the glucocorticoid hormones and restore neurogenesis, but the mechanism by which this happens was unknown.

Now, scientists at King's College London in the UK have found that antidepressants affect neurogenesis by interacting with the glucocorticoid receptor, leading to expression of key genes needed for stem cells to differentiate and proliferate. The group exposed cultures of human stem cells from an area of the brain called the hippocampus to a range of antidepressants, including sertralene, which is marketed as Zoloft by Pfizer.

'We've seen that the glucorticoid hormones and the antidepressants activate the same protein, called the glucorticoid receptor,' explained Christoph Anacker, who led the study group. 'But they activate this receptor in very different ways'. Glucocorticoids decrease neurogenesis, whereas antidepressants increase it.

The researchers say that their work provides a model for depression in the laboratory and a platform for drug discovery to develop antidepressants that are more effective and lead to fewer side effects. 'It demonstrates that antidepressants have effects which go beyond simply increasing the transmission of serotonin in the brain,' says Daniel Smith, an expert in clinical psychology at Cardiff University, UK. 'Current antidepressants have quite a broad range of effects and interact with a large number of different receptors in the brain.' The work could lead to new drugs that target the glucocorticoid receptor more specifically, he adds.

By 2020, depression is expected to be the second most damaging disease globally as measured across a range of indicators. One in five women and one in 10 men are likely to experience the disease at some point.

Meera Senthilingam
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Solvay and Rhodia to form European giant

11 April 2011

Speciality chemical companies Solvay and Rhodia, have agreed to a deal that will see Solvay purchase Rhodia for 3.4 billion (£3 billion) in cash.

The move will create a European chemical giant with annual sales of 12 billion. Key products for Solvay include speciality polymers, sodium carbonate and hydrogen peroxide. Solvay employs 17,000 people, and in 2010 it made sales of 7 billion. Rhodia makes: materials from silica and rare earth elements; products for consumer markets, such as surfactants, natural polymers and acetate; engineering plastics based on polyamide; and other products. Rhodia employs 14,000 people, and it generated sales of 5.23 billion in 2010.

Solvay sold its pharma business to Abbott for $5.2 billion in 2009, and in September 2010 it said it would cut 800 jobs worldwide.

The two companies say that combining their activities will lead to annual savings of 250 million within three years. But two thirds of the money saved will come from outside the new company, and therefore they are not planning any 'major' downsizing as a direct result of the move.

The deal follows DuPont's $5.8 billion (£3.5 billion) deal for Danisco and Clariant's 2 billion deal for Süd-Chemie.

According to Constantine Biller, director and senior analyst for chemicals at UK corporate finance advisory firm Clearwater, this marks the end of the period of 'bolt on' acquisitions. 'Groups are now looking at diversifying their product areas and geographic reach,' he says. 'Rhodia takes Solvay into more growth markets.' When viewed together, the two companies currently generate 40 per cent of sales in emerging markets.

Biller says there are lots of companies with 'reinforced' balance sheets looking for similar acquisitions. Companies in Europe and North America are motivated by growing demand in the so-called N11, the 'next 11' growth economies, as well as the bric countries (Brazil, Russia, India and China), he adds.

Andrew Turley

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One catalyst, two reactions

11 April 2011

Researchers in the US have designed a novel material that can catalyse two separate, sequential reactions to produce industrially relevant intermediates in one pot.

Solid catalysts are important in the chemical industry for accelerating the production of compounds that make commodity goods. The catalysts are typically nanometre-sized metal or metal oxide particles supported on a high surface area solid. They can be modified chemically to tune their performance, but it is difficult to catalyse multiple reactions with only one material.

Now a team led by Peidong Yang at the University of California, Berkeley, has developed a nanocrystal catalyst that incorporates multiple metal-metal oxide interfaces and can catalyse two different reactions in sequence.

The assembly of the new tandem catalyst
© Nature Chemistry

Platinum nanocubes were assembled into a one nanocube thick monolayer with oleylamine capping agents in between the cubes and transferred onto a flat silica (SiO­2) surface. A second monolayer made of ceria (CeO2) nanocubes spaced with oleic acid was then placed on top to form a bilayer. UV irradiation removed the capping agents to leave vertical gaps between the stacked nanocrystals. This provides a high surface area, and clean metal-metal oxide catalytic interfaces.

'With our novel concept of interface design through nanocrystal design we have a versatile principle where multiple interfaces can be assembled, be responsible for separate reaction steps and ultimately lead to great reaction selectivities, says Yang.

To test the bilayer structure, the team used the two distinct metal-metal oxide interfaces - CeO2-Pt and Pt-SiO2 - to catalyse two sequential reactions. CeO2-Pt catalysed the decomposition of methanol to CO and H2, which then made propanal byPt-SiO2 catalysed ethylene hydroformylation.

'This work will be high impact in the catalysis community and in industry, getting people to think about smart catalyst design, which is the core for energy and chemical provisions,' says Edman Tsang, an expert on solid catalyst design at the University of Oxford in the UK. He goes on to say however, that unwanted side reactions could occur with reactants or products being converted by the wrong catalyst interface. 'There is still a long way to go for this concept to flourish. But the design is indeed interesting,' he adds.

Yang believes that the tandem catalyst could be easily used in large scale industrial processes. 'One could simply devise a scale-up process for producing tandem oxide-metal junctions using a colloidal route,' he says. He explains that the next step is to explore new oxide supports such as TiO2 in the catalyst designs. 'We are starting to explore the same concept with multi-step photoelectrochemical reactions such as solar water splitting,' he adds.

Mike Brown
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Pocket sized fuel cell, a step closer

11 April 2011

A new catalyst for hydrogen evolution could see you carry around a fuel cell in your pocket to power electronic devices.

Commenting on a story for Chemistry World last year that employed a homogeneous catalyst to convert formic acid into hydrogen got Edman Tsang of the University of Oxford, in the UK, thinking. So he went into the lab and made a heterogeneous catalyst that does the same job at ambient temperatures, without the need for solvents or additives.

'We went back and thought: why don't we develop a room temperature heterogeneous catalyst using a cleaner system?' says Tsang, who is part of an EPSRC funded consortium investigating hydrogen production from organic molecules.

Formic acid - a byproduct of biomass processing - is thought to be a great source of hydrogen for fuel cells, because it has a high energy density and is readily available. But so far, catalysts to produce hydrogen from formic acid have all had drawbacks. Heterogeneous catalysts incorporating noble metals have needed high temperatures, while homogeneous catalysts have managed to work at room temperature, but need organic solvents and additives like amines or bases.

Pocket sized fuel cells that use formic acid as a hydrogen source could power your mp3 player sooner than you think
© Nature Nanotechnology

Tsang's new catalyst combines the best of both worlds, it is a cleaner system and works at room temperature. The catalyst uses the unique properties of a core-shell system to do things that normal noble metals can't. The palladium outer shell adsorbs the formic acid and splits it into hydrogen and carbon dioxide. To increase the catalytic activity, an electron rich core of silver modifies the properties of the palladium to maximise efficiency.

'For mobile applications, low temperature hydrogen on demand is a big advantage' says Henrik Junge, who investigates formic acid as a hydrogen source at the Leibniz Institute for Catalysis at the University of Rostock, Germany. Junge describes the work as a 'big step' towards using fuel cells to power electronic devices.

The new catalyst works at a turnover frequency comparable to other catalysts developed already. 'You'll have to make sure that the amounts of hydrogen produced could be scaled-up to the levels needed for applications' says Junge, but Tsang's back of the envelope calculations suggest in theory the catalyst should be good enough for a fuel cell to power small devices. Capsules of formic acid could be plugged into the fuel cell, in your pocket, to power your mp3 player. Bigger devices like laptops will require further improvement to the design.

'There are lots of hurdles before you can get a real device' Tsang says. He is now working to improve the turnover frequency of his device and then says he'll need to work with engineers to work out how to make the concept of liquid fuel and fuel cell into reality.

Laura Howes
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Surface plasmons create vivid holograms

07 April 2011

Holograms displayed using interactions between light and the collective oscillations of electrons on the surface of a metal, known as surface plasmons, are set to transform three-dimensional imaging technology. Satoshi Kawata and his team from Japanese research insitute RIKEN's Saitama campus have constructed images that, unlike credit-card holograms, appear in the same natural colours from any angle.

Plasmons are "quasiparticles" that are observed when electrons in a metal collectively oscillate at light wave frequency. If light falls on a metal with a lower frequency than the surface plasmons it is reflected, while higher-frequency light is transmitted. The frequencies of gold and silver's surface plasmons are in the visible range, causing their distinctive colours. Katawa's team exploits this phenomenon. 'Our proposal is plasmons can be used to select colours in a hologram,' he says. 'This hologram is reconstructed by white light - you don't need a laser.'

Reconstruction of a red apple with a green leaf in three dimensions using surface plasmon holograms
© Science/AAAS

Lasers are still needed to make the hologram. Team members Miyu Ozaki and Jun-Ichi Kato illuminate objects with red, green and blue lasers and the light beams diffract onto a glass sheet covered in a 150 nm thick layer of photoresist material, recording the image.

To make the plasmon hologram, the scientists coated 55 nm silver and 25 nm glass layers onto the photoresist. Shining light into the hologram through a prism from three different angles, one for each colour, reconstructs the three-dimensional image.

Katawa predicts that he and other scientists will eventually use this method to create moving pictures. But even before that such holograms promise 'revolutionary' tools for personalised medicine, according to Heike Arnolds, who researches plasmon-enhanced photochemistry at the University of Liverpool. 'Chemists are ideally placed to exploit this by producing functionalised hologram surfaces for surface plasmon resonance sensors,' she says. A glucose sensor might display its readout through characteristic colour changes, Arnolds explains. 'If your apple doesn't look green, go see a doctor.'

Andy Extance

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Long chains give new life to RNA world hypothesis

07 April 2011

The so-called RNA world hypothesis has gained fresh momentum with the synthesis of the longest lab grown RNA strands made using an enzyme that is itself made of RNA, an 'RNAzyme'.

Philipp Holliger and his team at the Medical Research Council laboratory in Cambridge, UK, developed an RNAzyme that makes RNA strands comprising up to 93 bases.

The RNA world: RNA would have done the jobs that proteins and DNA do today
© Medical Research Council

In 1968, Francis Crick suggested that the first enzyme might have been made from RNA, and from this idea came the 'RNA world' hypothesis, in which life began with an RNA molecule that gained the ability to self replicate. The hypothesis has since generated huge interest in the scientific community, and the wider public, but it remains unproven.

Scientists identified the first RNAzyme in the early 1990s. In later work, they picked mutants of that structure to grow longer, but the chains were still relatively short chains, typically comprising about 20 bases, and the bases were put in the same sequence despite changing the mutant.

Holliger normally works on the more familiar enzymes made of proteins. By introducing evolutionary pressure, the group was able to selectively improve the enzyme and then combine the best bits of their experiments to make a new RNAzyme that replicates faster and more reliably than previous attempts.

'The pressure was just the right kind of pressure' says Gerald Joyce, who studies the evolution of RNAzymes at Scripps in California, US. Holliger was able to add 'some really nice technical twists to select for polymerisation', he explains. 'Molecular evolution is a powerful process and allows us to rapidly identify RNA molecules with a desired activity' adds Holliger, explaining how the group found their 'needle in the haystack'.

As well as making longer strands of RNA, the RNAzyme can also make enzymatically active RNA molecule, something Joyce says is extremely significant.

Holliger says he hopes that his work, along with that of other groups, will provide sufficient clues to 'replay the tape' and plot a likely course for how life began.

'The mindset in the field is let's just make an RNA world so we can see one in motion,' says Joyce. 'There's only one example of life that we know of wouldn't it be cool if we had another example, even if it was synthetic biology,' he adds.

'There are still some formidable challenges ahead,' Holliger says. But the development of self-replicating RNA would be an enormous step forward. 'It's pretty clear where you'd go from there,' he adds.

Laura Howes

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Molecular can reach millikelvin

07 April 2011

Scientists have laid the foundations for a high-performance 'molecular fridge' capable of reaching temperatures within a few thousandths of a degree of absolute zero (0K) with a high degree of efficiency. Such ultracoolers could have applications in areas such as ultra-low temperature physics, where alternative technologies such as those that rely on expensive and rare helium-3 could be unsuitable or too costly.

The system relies on a phenomenon called the magneto-caloric effect, where the removal of a magnetic field from a ferromagnetic material causes a drop in temperature. The key to achieving a high magneto-caloric effect is to have a material with many unpaired electrons, all of whose spin states are aligned.

Euan Brechin from the University of Edinburgh in the UK, Keith Murray from Monash University in Australia and Marco Evangelisti from the University of Zaragoza in Spain and their colleagues designed a molecule based on gadolinium and copper, which can be cooled to a few millikelvin.

Molecular structure of the gadolinium and copper complex

To produce the required high magneto-carolic effect, the team used an ion consisting of five copper atoms and four gadoliniums - a system with multiple unpaired electrons in the appropriate spin state.

But once you start joining these individual ions together into a large molecule, there is a problem,' says Brechin. 'Ninety-five per cent of all metal-metal interactions are antiferromagnetic - their magnetic moments cancel each other out.'

So the challenge was to retain the electronic and magnetic integrity of the individual ions while incorporating them into a molecule capable of being processed. 'The key is to use organic connector ligands,' says Brechin. 'We use a polyalkoxide - when it is deprotonated the oxygens can bridge the metals. We are almost making a metal oxide but are stopping growth by encapsulating the metal centres in an organic shell.' This produces a crystalline material consisting of discrete molecules, each retaining its important characteristics. When a magnetic field is removed, significant temperature reductions can be achieved at the molecular level and hence in the whole material.

'When we change the magnetic field by 1 tesla the temperature falls by 2 kelvin,' says Brechin. 'This is a very big drop. So if you take the sample material down to 4 K by conventional means, you can then take it to very close to absolute zero extremely efficiently.'

Commenting on the research Eric McInnes, an expert in low-temperature magnetic refrigerants at the University of Manchester in the UK, says, 'This new material adds to the growing family of magnetic cluster compounds that show considerable promise for low-temperature cooling applications, but it raises the bar for the potential level of performance.'

Simon Hadlington

RSC