Self-healing coatings for steel

31 August 2010

A conducting polymer film acts as a self healing coating to protecting metals from corrosion, say researchers in Japan.

Steel is used to construct many different structures but is susceptible to corrosion, which can limit its practical uses and lifetime. Structures such as bridges or boats are often exposed to salt solutions that rapidly corrode them. This is a large problem and costs related to corrosion in developed countries amounts to approximately four per cent of their gross national product.

Damian Kowalski and coworkers at Hokkaido University have developed a new type of coating using an intrinsically conducting polymer (ICP), polypyrrole, which could be used as an alternative to expensive and toxic chromates currently used.

Ions are released when the coating is damaged and react with the metal to repair itself

ICPs are, in effect 'synthetic metals', capable of conducting electrical currents or ions. Kowalski doped polypyrrole with heteropolyanions (PMo12O403- and HPO42-). When the polymer coating is damaged, healing ions are released to the affected site, react with the steel forming an insoluble iron molybdate salt in the defect zone. This is different to other systems where usually a monomer is released to recreate the coating in the damaged region.

The key to the system is the control of the healing, explains Kowalski, 'in our work we have demonstrated how to control the release of these healing ions using an ion-permselectivity approach'. This stops the healing ions reacting with the metal before the coating is damaged, significantly increasing the lifetime of the coating.

Paul Braun, an expert in self-healing coatings at the University of Illinois, US, is impressed by the novel approach. Braun sees one possible advantage of Kowalski's system is its size, as it is 'much thinner than other coatings, which will be a distinct advantage for some applications'.

Kowalski is now developing the system to improve the healing response of the coating, attempting to reduce the size even further.

Jon Watson

Oyster glue's secret ingredient

31 August 2010

The natural cement produced by oysters to build extensive reef systems contains significantly more inorganic material than the glues of other marine species, and could spur development of new synthetic adhesives for biomedical devices or antifouling coatings for ships, say researchers in the US.

Jonathan Wilker and his team at Purdue University and colleagues at the University of South Carolina have been investigating how oysters bind to reefs and each other, in a bid to develop synthetic composite materials with properties that imitate the oyster glue.

The team analysed the chemical composition of oysters' adhesive using infrared spectroscopy, electron paramagnetic resonance spectroscopy and thermogravimetric analysis. They found higher protein content in the adhesive material than in oyster shell (10 per cent as opposed to 2 per cent), and evidence of protein cross-linking, iron species and radical species.

Oysters cement themselves together (left) and can form large reefs (right)
© J. Am. Chem. Soc.

However, the rest of glue, around 90 per cent, was formed mainly of inorganic species such as calcium carbonate. This feature separates oysters from other marine species such as mussels and barnacles, whose glues are predominantly protein based with only a small portion of inorganic material. 'It looks like oysters have more of a hard, inorganic cement compared to mussels and barnacles that produce more of a soft organic glue,' says Wilker.

'This study reveals new details of a previously poorly-characterised marine adhesive, and a rare example where a significant inorganic mineral component is present,' says Phillip Messersmith, an expert in biomedical engineering at Northwestern University in Illinois, US. 'It will be interesting to see if follow-up studies provide insight into the mechanism of formation, crystallography and mechanical role of the inorganic component,' he adds.

Wilker hopes that the different properties of the oyster adhesive compared to mussel or barnacle glue could lead to a new class of synthetic materials. 'One of the more appealing ideas would be if you could adapt this kind of technology into a surgical adhesive, a bone cement or dental cement,' he tells Chemistry World.

By understanding how the oysters stick to surfaces the team could also develop surfaces that prevent them sticking in the first place, which could be useful in antifouling coatings on ship hulls, Wilker says. At present, copper based paints are used, but they can be toxic to marine organisms as the copper is released into the water.

Mike Brown


Bio battery based on cellular power plant

27 August 2010

Leigh Krietsch Boerner/Boston, US

Mitochondria, often called the powerhouse of the cell, have been harnessed in a new battery-like device that could one day power small portable devices like mobile phones or laptops.

Mitochondria convert fatty acids and pyruvate, formed from the digestion of sugars and fats, to adenosine triphosphate (ATP), the cell's energy supply. Along the way a tiny electrical current is generated, and Shelley Minteer and coworkers from Saint Louis University in Missouri, US, have now harnessed those flowing electrons to put them to work in a new biological battery device.

Speaking at the American Chemical Society national meeting in Boston, US, Minteer described how her team has built a biological battery that incorporates whole mitochondria capable of producing a current anywhere from microamps to milliamps per square centimetre, depending on the surface area of the mitochondria and the load density.

Mitochondria generate energy within cells, and could now be tapped in new bio battery devices
© Dr David Furness, Keele University/Science Photo Library

Minteer notes that commercially available batteries contain metals, and need to be recycled. However, battery recycling facilities aren't widespread in many areas. 'My research is about transitioning from these metal-based batteries to a biological battery,' she said. 'The living cell does energy conversion very efficiently.'

Similar to a traditional battery, the bio version contains two electrodes. The cathode houses the conversion of oxygen to water, while the anode holds the immobilised mitochondria. 'Once the substrate comes in it can be completely oxidised to carbon dioxide, and when that happens, electrons go through the wire and do work.'

The bio battery is completely renewable and biodegradable, and is stable at room temperature and a neutral pH for up to 60 days. Minteer says the new batteries would be best suited to small devices that have intermittent use.

Right now, the test cell is in an open glass container in the lab, but for future commercial use, it would be in a hard plastic container. The fuel, any high energy dense liquid, would be added through a sealed, disposable cartridge that would be replaced as needed.

In the future, Minteer wants to increase the surface area within the device so they can increase the loading density of the mitochondria because at the moment they're limited by the amount can put on the electrode. They're also looking at ways to improve the energy density output, and reengineer the size of the device to be as compact as possible.

Evgeny Katz, an expert in biochemistry at Clarkson University in New York, US, describes this as 'an extremely interesting approach,' because the mitochondria can 'consume the whole biochemical, producing much more energy and power from the oxidation process'. He was also impressed with the very high stability of the mitochondrial battery. 'In most biofuel cells, the critical issue is not only how much power you produce but how long you can get it,' Katz explains.

Predicting drug response

27 August 2010

Scientists in China have developed a probe that could be used to test how well a patient will respond to certain drug treatments.

The new probe measures the activity of N-acetyltransferase 2 (NAT2), an enzyme that metabolises drugs and other toxins containing aryl amines and hydrazines. The activity of NAT2 differs between individuals, which affects how well a drug will work, and dysfunction of the enzyme has been linked to breast cancer, Parkinson's and other diseases. A simple measure of NAT2 activity could help ensure patients are given drugs that they can metabolise effectively with minimal side effects.

Xuhong Qian and colleagues at the East China University of Science and Technology in Shanghai found that the fluorescent molecule amonafide is metabolised specifically by NAT2. The enzyme acetylates the probe molecule, shifting its flourescence wavelength. Hence, this fluorescence change correlates to NAT2 activity. Current methods for predicting patient response to certain drugs require complex genetic analysis, but this probe could provide a simple and sensitive test.

Acetylation by NAT2 changes the fluorescence wavelength of amonafide

AP de Silva, an expert in fluorescent sensors at Queen's University Belfast, UK, admires the team's use of fluorescence in two colours to monitor an intracellular enzyme. He adds 'this work is likely to attract favourable attention.'

'The probe has significant potential applications in personal medicine,' Qian says. 'We also hope that it can be used to study the mechanism of different kinds of diseases related to NAT2.' The team now intends to design probes for other important enzymes.

Harriet Brewerton


A self-optimising microreactor system

26 August 2010

Chemists in the US have developed a microreactor system which automatically calculates the optimal conditions for the chemical reaction it is undertaking. Once computed, the conditions can then be applied to a larger-scale reaction system. The researchers say their approach can save hours or days of tedium in the laboratory, by eliminating many manual experiments that would otherwise be required, as well as reducing the amounts of reagent needed.

To demonstrate the system, the research team from the Massachusetts Institute of Technology used the reaction of 4-chlorobenzotrifluoride with 2,3-dihydrofuran - an example of a Heck reaction, widely used in organic synthesis. Three syringe pumps containing the various components of the reaction were fed into a mixer, which in turn was connected to a 140ul microreactor. The yield of product was measured by high performance liquid chromatography (HPLC), whose results were passed to a computer programmed with an 'optimisation algorithm'. This enables the computer to take information about parameters such as flow rate, temperature and concentration of reactants, relate them to the yield, and then adjust them intelligently - based on the readings from the previous cycle - to produce gradually higher yields of product. The computer is also connected to the apparatus that controls flow rate, temperature, reactant concentration and so on, enabling these adjustments to the experimental conditions to be made automatically.

Within 2 days and after multiple cycles the system had arrived at the optimal conditions for a product yield, in this case, of 83 per cent.

The combination of feedback control and continuous-flow operations in the microreactor allows the reaction to be optimised and then scaled up
© Angew. Chem. Int. Ed.

'We then wanted to see if we could use this information to scale the experiment up,' says team member Klavs Jensen. Using the conditions calculated by the microreactor system, the experiment was scaled up to a reactor representing a 50-fold increase in volume. 'The same optimal conditions applied at this larger scale,' says Jensen.

The researchers say that their system should be applicable to many reactions that can be conducted in a microreactor and could result in far less time and material being expended on finding the optimal conditions for a reaction - something that is key in organic chemistry. Furthermore a range of optimisation algorithms exist which can be applied to a variety of complex reaction scenarios. An added bonus, says Jensen, is that the system automatically calibrates the HPLC - 'one of the more tedious parts of doing this kind of work by hand.'

Commenting on the work, Kaspar Koch, managing director of FutureChemistry, a company based in the Netherlands specialising in microreactor technology, says, 'Conventional industrial optimisation methods are still laborious and environmentally unfriendly due to the large consumption of chemicals required. This new research exemplifies the advantages of microreactor technology in a low-waste reaction self-optimisation system consuming only minute amounts of starting materials - another significant step forward to smarter and greener chemistry.'

Simon Hadlington


Antibiotic nanoparticles go for gold

25 August 2010

Phillip Broadwith/Boston, US

Chemists in the UK and India have developed a simple, one step synthesis of gold nanoparticles incorporating an antibiotic, without using any other chemicals. The particles make the antibiotic more stable and could overcome some types of bacterial resistance.

Speaking at the American Chemical Society national meeting in Boston, US, Carole Perry from Nottingham Trent University described how her team discovered that the beta-lactam antibiotic cefaclor can be used to control the synthesis of gold nanoparticles.

Perry explains that the process gets around several problems with other methods used to attach antibiotics to metal nanoparticles. 'When you buy or make nanoparticles, you end up with (often toxic) chemicals on the particle surfaces,' she says. 'These have to be removed, then you need to find some way to attach the antibiotic to the surface, which usually involves further chemical modification steps.'

The team's method is very simple, requiring no fancy equipment: 'All you need is a balance to weigh out the components,' Perry says. The particles are made by simply mixing a gold salt with cefaclor in water between room temperature and 70°C and stirring for a few minutes or hours. Although the team have not fully investigated exactly how cefaclor transforms the gold ions into gold metal, Perry believes that the free amine group on cefaclor is responsible for the metal reduction.

There are two possible ways to synthesise the antimicrobial gold nanoparticles. The resulting particles could be useful in overcoming some kinds of bacterial resistance
© J. Mater. Chem.

Beta-lactam antibiotics like the penicillins and cephalosporins disrupt bacterial cell wall formation, but many strains of bacteria have developed resistance. Perry explains that the nanoparticles could overcome some of those resistance mechanisms by delivering a concentrated dose of cefaclor. The cell wall is then disrupted before the cefaclor can be broken down by the cells defensive enzymes. This then allows the nanoparticle to get inside the cell, where the gold can interfere with DNA replication.

'This synergy between the gold and a conventional antibiotic is very interesting,' says Ramanathan Nagarajan, who develops antibacterial textiles at the US Army Natick Soldier Research, Development and Engineering Center in Massachusetts, US. 'Classically people have used silver for a lot of antimicrobial applications, so it could be interesting to develop something that has different advantages compared to silver systems.'

Perry is enthusiastic about the scope of the discovery: 'Many other antibiotics have free amines that could work in the same way,' she says, 'and it could be useful for people designing new antibiotics to incorporate into the design process.' She adds that the extra stability of the gold-supported cefaclor has allowed the team to investigate applications such as sticking the particles to surfaces, with a view to using them in hospitals or wound dressings.

Rapid cell extraction using droplets

25 August 2010

An aqueous two-phase microdroplet system that isolates and extracts cells could aid research into tissue engineering and regenerative medicine, say UK scientists.

Droplet-based microfluidic systems, using a fluorescence-based detection method have been used to locate, identify and discriminate cells within a specific droplets and more recently two-phase systems have been investigated for their ability to separate different biological materials. Target cells distribute between phases by their own thermal motion to reach equilibrium but so far this has proved a slow process.

Now, Andrew deMello and his team at Imperial College London have devised a novel method to separate cells using microfluidic droplets. The process could enable high throughput cell separation which would be ideal for clinical applications such as cell therapy and regeneration.

A PEG microdroplet completely encases the DEX droplet

In deMello's device, human T lymphoma cells enter the microdroplet system within a dextran solution. At a T-junction in the device, the dextran meets a polyethylene glycol (Peg) inlet where a droplet of Peg completely encapsulates a dextran droplet. These droplets then follow a winding channel in the device that causes both phases to mix - forming an emulsion and allowing the cells to experience the environment of both phases. When the two phases separate back into a double droplet, the cells remain in the outer Peg phase.

Binding the cells with an antibody-N-isopropylacrylamide (Ab-NIPAM) is crucial to the separations explains deMello as this makes them favour the Peg phase. Without the Ab-NIPAM, 98 per cent of the cells remain located within the dextran. But once bound this reverses to 93 per cent moving to the outer Peg droplet.

Shashi Murthy, an expert in microfluidic devices design at Northeastern University in Boston, comments that conventional approaches 'are quite effective, but there's a lot of interest in trying to make them more simple and as microfluidic systems are being proposed as disposable and cheap alternatives to more expensive instrumentation, this is of significant interest.'

The team believe that the technique will be able to separate heterogeneous cell populations in a high-throughput manner. Also, the use of Ab-NIPAM conjugates can be applied to a wide range of other cell systems simply by changing the antibody.

Anna Watson


A better way to add radioactive fluorine

24 August 2010

Making compounds that contain the useful radioisotope fluorine-18 (18F) could be much easier in future, say researchers in the UK and Finland. The team integrated the isotope into a popular fluorinating agent called Selectfluor, which opens up a wide range of chemistry to build useful radiolabelled molecules.

18F has a half-life of around 2 hours and releases positrons as it decays, making it perfect as a radiotracer in positron emission tomography (PET). This type of medical imaging is increasingly popular for disease diagnosis and monitoring a patient's response to therapy, but it also has great potential in drug discovery.

By adding 18F to the organic structure of new drug candidates, PET scanning can be used to identify the biological interactions of the compounds. This gives chemists valuable information about the behaviour of new drugs early in their development, which helps pharmaceutical companies to make important decisions sooner in the pipeline.

But making compounds that contain 18F is awkward, explains Véronique Gouverneur, who led the research at the University of Oxford, UK. 'The only way to carry out electrophilic fluorination has been to use fluorine gas (F2), which is extremely reactive and corrosive. Very few places have the facilities to manipulate this dangerous gas.'

Selectfluor, has been radiolabeled with 18F. The new reagent is safe, nontoxic, and easy to handle. The combined use of [18F]Selectfluor bis(triflate) and silver triflate allows for the preparation of electron-rich 18F-aromatic compounds through a simple 'shake and mix' method at room temperature
© Angew. Chem. Int. Ed.

The high reactivity is a problem because F2 gas often over-fluorinates complex molecules or causes unintended side-reactions. Also, F2 gas is not made as two molecules of 18F - and the large amount of normal 19F present can cause low radiochemical yields.

To solve these problems, Gouverneur's team built 18F into a popular fluorinating agent called Selectfluor. The reagent is nontoxic and undergoes a variety of fluorination reactions that are quick and easy to handle. 'Our reagent has a much better reactivity and selectivity profile, and can be easily transported short distances to local sites that do not have the capacity to manufacture it themselves,' Gouverneur told Chemistry World.

'Selectfluor has been around for almost two decades now, and is the most versatile electrophilic fluorinating agent out there,' says Tobias Ritter, a fluorine chemist at Harvard University in Cambridge, US. 'Access to this labelled chemical will allow chemists to tap into a large manifold of reactions that could be extremely useful in the pharmaceutical industry.'

Lewis Brindley


Growing magnetic leaves

23 August 2010

A magnetic leaf has been created by researchers in Germany using a simple one-step process to synthesise a complex iron carbide microstructure that mimics the intricate structure of a leaf.

The team's biotemplating method could be an easy and efficient way to enhance the functionality of metal carbides for catalytic and electrochemical applications.

Metal carbides are a desirable material, especially for use in electrodes and extreme catalytic processes, because of their resistance to high temperatures and mechanical stress. These properties, however, make it difficult to control their crystal growth and thus enhance their structures for optimal performance.

Now, Zoe Schnepp and colleagues at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany have used a biological templating technique to synthesise a highly complex iron carbide structure. 'Iron carbide in particular is quite challenging to synthesise, even as a powder, and so the fact that we've got such a complex microstructure is a really big advance,' says Schnepp.

To make the iron carbide leaf, the team soaked a leaf skeleton in an iron acetate solution, which was then dried at 40°C in air and then heated under nitrogen to 700°C. During this process, the leaf skeleton (comprising lignin and cellulose)
decomposes to a carbon-rich matrix and the iron acetate decomposes to iron oxide.

Carbothermal reduction of the iron oxide by the carbon leaf matrix produces a porous iron carbide leaf replica

The intricate structure of a fig leaf was recreated as a magnetic iron carbide leaf
© Angew. Chem. Int. Ed.

Simon Hall, who investigates biotemplating as a way to create new materials at the University of Bristol, UK, thinks the work offers an 'elegant solution' to the problems of making metal carbides. 'Most work of this nature is concerned with the growth of oxides, carbonates and phosphates, so it is exceptional that a carbide phase has been synthesised using a one-step biotemplated approach.'
'Metal carbides offer some really remarkable and unique properties like hardness or high magnetisation and so new approaches for the synthesis of these materials are very important,' explains Schnepp. 'There are lots of properties of metal carbides which would be useful in a certain product shape, for example a high-surface area sponge or a thin film.'

Experiments with the iron carbide leaf revealed that it had magnetic and conductive properties suitable for water splitting and electrodeposition of platinum. However, although Schnepp says it's possible the magnetic leaf could find some applications, the work is more important as demonstrating a general route to complex metal carbide structures.

'In theory any carbon-based structure could be used with this method. You could choose your original template to have the structural characteristics you want in your magnetic and conductive iron carbide product,' she adds.

James Urquhart

Microscopic barcodes with extra stirring

23 August 2010

A way to label molecules with colourful barcodes has been developed by chemists in South Korea. The barcode particles, which resemble microscopic dice, have a pattern of coloured spots that gives them a unique spectral fingerprint. In addition, they can spin around and function as miniaturised stirrer bars to speed up reactions.

Labelling compounds is particularly helpful in drug discovery, where the best way to find active molecules is with high-throughput screening. This method tests millions of compounds for reactivity with a biological target, and a common technique is mixing thousands of candidates together in a biological assay. By labelling the molecules with fluorescent tags, any compounds that are 'hits' can be easily identified.

The secret to making the new particles, says Sunghoon Kwon, who led the research at Seoul National University, is 'magnetic ink' developed by his team last year. This is made from a mixture of UV-sensitive polymer and magnetic nanocrystal clusters that reflect specific wavelengths of light depending on an applied magnetic field.

As the magnetic field varies, the ink changes colour - and in combination with optical lithography, UV light can be used to 'freeze' the colour in small areas on the particles. This process can generate spots as small as 5um on a 200um tile, and takes less than a second.

The microparticles can be made in a range of shapes with multi-coloured spots, giving each a different spectral fingerprint
© Nature Materials

The new labels greatly increase the number of unique identifying tags that could be used at once, from around a thousand combinations up to well over a billion. But this is not the only advantage, Kwon says. 'Our geometric coding capacity dwarfs any previously developed encoding techniques - but the immediate advantage to biologists is the faster reaction time.'

Since the labels contain magnetic nanoparticles, a rotational magnetic field can be applied to spin them around, Kwon explains. 'We found that this process can reduce reaction times by a factor of ten,' he told Chemistry World.

The process may also be useful in sequencing DNA - where many different labels are required to tag and track samples. Another possibility is to develop new anti-counterfeiting techniques, as the unique spectral fingerprints generated would be impossible to replicate.

Robert Wilson, an expert on nanoparticle labelling at the University of Liverpool, UK, is interested by the research, but indicates that some improvements will be needed before the process is practical. 'Currently, the particles are too large for use in bioassays - most commercially used particles have diameters of about 10um rather than 200um,' he says. 'In addition, although making each particle in less than a second sounds fast - when you need to make thousands for each individual assay, it is very slow indeed.'

Lewis Brindley


Plastic oceans

19 August 2010

Plastic waste is a problem in the oceans, but it's not clear where it is - or how much there is. Kara Lavender Law and colleagues at the Sea Education Association in Woods Hole, Massachusetts, US, have been trying to pin down where plastic debris accumulates in the Atlantic, and were surprised to find that, despite the rise in plastic production, the amount of debris in the ocean hasn't really increased.

Fishing for plastic in the North Atlantic subtropical gyre
© Science

Law's team sampled the sea surface for biological organisms twice a day using a plankton net, about a metre wide at the mouth, and with a mesh size of about 0.33mm. 'As early as the late 1970s, we noticed that we were collecting tiny bits of plastic,' says Law. The team has now analysed data from the past 22 years - more than 6,000 net tows- to try and quantify the amount of plastic in the western Atlantic and the Caribbean.

'Surface currents transport the debris around the ocean, and the highest concentrations of plastics were found in subtropical latitudes where the currents come together. We're not sure yet how far east it goes as we've only studied up to just east of Bermuda,' she says. The fragments of plastic are mostly HDPE, LDPE and polypropylene, which are less dense than seawater - denser plastics like PET will sink.

Perhaps the most surprising result, she says, is that they didn't see an increase in debris over time. 'Global plastic production has increased rapidly, and while we don't have any direct measure of the amount of plastic entering the ocean, there is a strong inference it has increased,' she says. 'It's possible some is broken down into even smaller pieces that were not captured by the net, and organisms growing on the debris will increase its density and cause it to sink. Microbes have been known to adapt to available food sources, and this summer we collected samples to try and identify whether there's some class of organism that's taking advantage of the plastic as a food supply.'

'This is a very interesting study, [but] while this paper clearly shows no consistent trend in the abundance of debris near the sea surface in the north Atlantic, we should not extrapolate this to other regions or habitats,' says Richard Thompson of the University of Plymouth, who has studied plastic debris in the north Atlantic. 'There are reports of plastic accumulating in remote regions, including the Antarctic, and in substantial quantities in the deep sea. We need more work to establish rates of accumulation in remote regions and, in particular, rates of accumulation of very small microscopic fragments. Meanwhile, we all need to work much harder to dispose of plastics properly.'

Sarah Houlton

Deepwater data suggests oil is sticking around

19 August 2010

New data collected by a submersible robotic laboratory provides insights into the magnitude and potential impact of the Deepwater Horizon oil spill in the Gulf of Mexico. The submersible identified a two-kilometre wide plume of hydrocarbons that had travelled 35km from the site of the spill and which researchers think may persist for a long time.

Richard Camilli at Woods Hole Oceanographic Institution, Massachusetts, US and colleagues analysed the data for a study published in Science. They estimate that 6-7 per cent of all the benzene, toluene, ethylbenzene and xylene (BTEX) hydrocarbons leaked in the spill are contained within the plume. BTEX hydrocarbons make up just 1 per cent of the total amount of oil released. Yet to account for BTEX concentrations of over 50 micrograms per litre, thousands of kilograms of it must have been pouring into the plume each day.

Camilli says the plume is evidence that the oil is persisting for longer periods than some might have hoped. 'Many people speculated that subsurface oil droplets were being easily biodegraded,' he says. 'Well, we didn't find that. We found it was still there.' The team's surveys suggest the plume has already persisted for months.

The Rosette submersible robotic laboratory being lowered into the ocean
© Science

One of the big concerns for fisheries in the short term is hypoxia - low oxygen levels - caused by bacterial blooms feeding on the oil as a carbon source. Matthew Jenny, who studies the effects of oil on marine animals at the University of Alabama, says bacteria blooms could potentially exacerbate an already recurring problem with hypoxia in the Gulf of Mexico. However, oxygen signals gathered in the study suggest that if the oil is being degraded by marine microbes, it isn't disappearing very quickly. On the other hand, this means the oil could travel further from the site of the spill.

Jenny says scientists can only speculate about what the research means for wildlife. 'We really do not know what the impacts on wildlife are going to be and it will be a year or two before we can really start to assess the impact,' he says. For instance, the toxic effects of the BTEX hydrocarbons the researchers focused on are only known for vertebrates and in particular, mammals. 'Far, far less' says Jenny, is known about their toxicity to marine invertebrates.

Hayley Birch

Strain creates rare type of magnet

19 August 2010

Scientists have created the world's strongest ferroelectric ferromagnet - a rare material that is electrically polarised while also having a permanent magnetic field. The new approach is an encouraging step towards developing these multiferroic materials for applications such as energy efficient computer memory, magnetic sensors and energy harvesting.

In 2006, Craig Fennie and Karin Rabe theoretically predicted that europium titanate (EuTiO3), which is antiferromagnetic, should exhibit both ferroelectric and ferromagnetic properties if grown as thin films on a substrate to induce a compressing strain on the material. Now, a large collaboration led by Darrell Schlom at Cornell University in Ithaca, US, have carried out experiments to confirm these predictions.

Straining a thin film of EuTiO3 on DyScO3 changes its magnetic behaviour
© Nature

The team discovered that when EuTiO3 was grown at a thickness of around 20nm on a slightly mismatched dysprosium scandate (DyScO3) substrate, the crystal lattice expanded by about 1 per cent. This created sufficient strain to cause the material to exhibit both ferromagnetic and ferroelectric properties 1000 times stronger than any previous known multiferroic material.

'Actually observing an antiferromagentic material turning into a ferroelectric and ferromagnetic material simply by straining it is quite amazing,' says Venkatraman Gopalan, a member of the team based at Pennsylvania State University, US. 'Our work confirms a theory-driven new route to multiferroics where magnetically ordered insulators that are neither ferroelectric nor ferromagnetic are transformed into ferroelectric ferromagnets using a single control parameter of strain,' he adds.

Being able to control magnetism with electric fields could be useful for next generation computer technology. 'In hard drives, you need magnetic fields to switch magnets, which is very power expensive,' explains Gopalan. 'Ideally you would want to do everything with 5 volts like in the rest of your computer, and a material that is both ferroelectric and ferromagnetic can allow that.'

The work is 'a magnificent example of theory-experiment collaboration in a field that is producing great results', says Beatriz Noheda, a materials scientist at the University of Groningen in the Netherlands. 'Although the current example only works at temperatures below 4K, it represents a great breakthrough because it shows that the theory works and that the materials can be grown.'

Gopalan agrees that the next step is to increase the temperature at which such a ferroelectric ferromagnetic phase can exist. 'We need a material that will show this behaviour at room temperature,' he says. 'Our theory collaborators are already predicting such materials and we are continuing to explore these predictions experimentally.'

James Urquhart


French plough money into green chemistry

18 August 2010

Green chemistry is one of five technologies set to benefit from a 1.35 billion (£1.11 billion) cash injection over the next 4 years in France. The investment, which was signed off on 8 August, aims to accelerate innovation and deployment of green technologies, explains Daniel Clement, assistant scientific director at the French Environment and Energy Management Agency (ADEME). There is no set quota on how the money will be distributed between the five technologies, he told Chemistry World, 'but it can be argued that aid for green chemistry will exceed 200 million'.

One of the primary objectives of ADEME's low carbon and renewable energy scheme is to stimulate research in chemical processes that start from plant raw materials. 'Eligible technologies are in the field of plant chemistry: biofuels, biomolecules, and building blocks,' Clement explains. 'It may also include disruptive processes, with a high risk but a potential for improving energy performance and high environmental impact.'

The other four technologies gaining funding alongside green chemistry are solar power, marine energy, geothermal energy and carbon capture and storage.

Overall ADEME will hand out 190 million for the project in 2010, and then 290 million every year until 2014. Two thirds of this will take the form of loans, with the remaining third being grants, and the government expects to attract over 2 billion in extra investment from private institutions.

The low carbon and renewable energy scheme was the first project to be signed off in an overall 35 billion strategic investment plan to boost the nation's scientific and technological competitiveness announced by the French government in December 2009.

James Clark, head of the green chemistry centre of excellence at the University of York in the UK, believes it's essential for European countries to make this kind of investment. 'It's fundamental,' says Clark. 'Traditional resources are going to get so pricey and so unreliable.' He points to a group of companies, associations and universities working on green chemistry in northern France called the IAR (Industries and Agro Resources) competitiveness cluster that he is collaborating with as a good example of the country's approach.

Such efforts gain particular importance, Clark says, when you consider countries beyond Europe, like Brazil and China who are already focussing heavily on green chemistry initiatives to meet local needs. 'The only way Europe is going to maintain a decent position is by being at the forefront of new technologies,' he says. 'If we don't get on with it, we'll be overtaken.'

Andy Extance

Photocatalytic production of hydrogen under visible light

18 August 2010

A simple and easy way to make mixed zinc-cadmium sulfide materials that produce hydrogen by splitting water under visible light has been developed by scientists in the US and China. The mixed materials can harvest a wider range of wavelengths than conventional materials, making them more efficient.

Photocatalytic conversion of sunlight to chemical energy, for example by producing hydrogen is an attractive alternative energy source and a feasible way to tackle the global energy and environmental pollution crises. Conventional photocatalysts, such as TiO2, CdS or ZnS, possess excellent activity and stability but only absorb near-ultraviolet light - which accounts for only 4 per cent of the solar spectrum. Expensive noble metal co-catalysts, such as platinum can be added to increase their absorption range but this increases their cost.

Now, Mietek Jaroniec from Kent State university, Ohio, and Jiaguo Yu from Wuhan University of Technology, have made mixed zinc-cadmium sulfide complexes doped with cadmium sulfide quantum dots (CdS QDs) that show high photocatalytic activity under visible light, without the need for noble metal additives.

CdS quantum dots increase the absorption range of the photocatalyst

'The high H2-production activity of the CdS quantum dot-sensitised material under visible light can be attributed to the facilitated electron transfer from CdS QDs,' says Jaroniec. The team made the mixed solid solution using a simple hydrothermal method to combine ZnS nanoparticles and Cd(NO3)2 salt. Followed by the thermodynamically favourable replacement of Zn2+ ions by Cd2+ ions using cation exchange.

Quantitative analysis shows that the photocatalytic H2-production of the new material is more than 50 times greater than CdS on its own, as well as being significantly better than platinum-doped ZnS under UV and visible light.

Max Lu, an expert in clean energy and environmental technologies at the University of Queensland, Australia, says, 'the results are quite exciting, and the CdS quantum dots are shown to be powerful in facilitating photocatalytic water splitting even without the use of Pt. If the stability is proven to be good, this system should offer opportunity to substantially lift the rate of hydrogen production under visible light irradiation.' Next, the team plan to find other quantum dot-based materials, which could be used to enhance hydrogen generation.

Jennifer Newton

Wet weather coatings

17 August 2010

Ever wished that your waterproof jacket could actively remove water from the inside? Now, scientists in Australia and the US have coated a fabric so that it could do just that by transferring water exclusively in one direction.

Water spreads in the plainweave polyester fabric and forms a droplet on the TiO2-silica coated polyester fabric
© J. Mater. Chem.

Directional transport of water is common in nature, where it is usually done by channel proteins that move water from one side of a membrane to another. However, most 'breathable' clothing membranes rely on temperature and concentration gradients to push water vapour from sweat through to the outside. Water can also be moved about by exploiting mechanical pressure gradients, or by making use of surface tension differences. However, these possibilities have only been studied on flat surfaces and not in porous materials like fabrics.

Tong Lin at Deakin University, Australia, and his colleagues coated a porous polyester fabric on both sides with a mixture of titanium dioxide and organosilanes. This combination is similar to a common coating for so-called superhydrophobic surfaces, which strongly repel water. They then shone UV light on one side of the fabric, which initiated a reaction that changed the coating. Because the effect of the light diminishes the further it penetrates into the fabric, a gradient forms from one side to the other. The side without UV light remains hydrophobic while the other side becomes hydrophilic. When water is dropped onto the hydrophobic side of the fabric, it is quickly transported through the polyester to the hydrophilic side, where it then stays.

The team was surprised by the findings as the researchers were simply aiming for a fabric with different properties on each side: 'We found it has an incredibly different property: water proactively passes through the fabric from the superhydrophobic to the hydrophilic side, but not the opposite way unless extra pressure is applied,' Lin explains. The team believes the simple coating technique could be used to produce high-performance fabrics for sports and military use, and even industrial membranes.

Howard Stone, who works on surface wetting and flow at Princeton University, US, is impressed by the work. 'I would have expected this strategy to work so long as the contact angles [the angle the droplet makes with the surface] went from 90 degrees toward zero degrees, but the authors show this works even when the initial contact angle on the hydrophobic side is greater than 90 degrees.' He suggests that the unexpected behaviour could be due to gravitational influences but says it needs further investigation.

Carol Stanier

A MOF you can scoff

17 August 2010

Chemists have accidentally discovered a new type of metal organic framework, or MOF, which is made from edible components. The materials needed to create the new structures are cheap, renewable and widely available and the conditions needed to create the frameworks are benign. That they can be made from molecules that are safe to eat could give the new compounds a role in the development of new food and pharmaceutical products.

MOFs consist of a network of metal-based nodes connected by organic struts. Their huge porosity and the ability to include chemical functionality within the pores have propelled MOFs to the forefront of a number of technologies including gas storage and capture, catalysis and drug delivery.

Fraser Stoddart's team at Northwestern University in Illinois, US, was attempting to make new interlocked molecular architectures based on the eight-membered sugar ring gamma-cyclodextrin, a low-cost derivative of starch. Dissolving potassium hydroxide with the cyclodextrin in water, then diffusing methanol through the system produced well-defined colourless crystals. 'When we obtained the x-ray structure of the crystals it was clear we had produced something surprising,' says team member Ron Smaldone.

Researchers have developed a MOF made from edible components

Working with colleagues from the University of St Andrews in the UK and the University of California Los Angeles, the researchers showed that six cyclodextrin rings had formed the faces of a cubic structure, held together by co-ordinating potassium ions, and these small cubes in turn fitted together in a large three-dimensional cubic framework. Each individual cube has a central pore of around 1.7nm across, with windows in each face of 0.8nm in diameter, which run through the structure as channels connecting the pores.

'We showed that the structure is stable in the absence of the solvent and that it was capable of absorbing nitrogen on a par with other MOFs,' says researcher Ross Forgan.

Most MOFs to date have been constructed from organics derived from petrochemical feedstocks. If MOFs become mass produced, structures derived from a renewable, carbon-neutral source could be attractive, Smaldone says. There is also scope to experiment with other natural macrocycles, using different metal centres and functionalising the internal space of the cubic units. The fact that the new MOF is made from molecules that have been approved for human consumption could make the structures useful for the food and pharmaceutical industries.

Lee Cronin, an expert on MOFs at the University of Glasgow in the UK, says, 'I think it is a remarkable discovery - something that is so simple but with such good physical properties in terms of nitrogen absorption. The fact that we can make high value materials from sugar is mind-blowing. The organic chemistry to manipulate these molecules is well known, so I think we could now have a whole new sub-field of chemistry in this area.'

Simon Hadlington

Nanosprings go for gold

16 August 2010

Squeezing gold nanowires inside a polymer case causes them to coil up into tiny springs, researchers in Singapore have found. These nanosprings store energy during the coiling process, and release it again when straightened back out.

Nanomachines may still be the stuff of science-fiction, but the miniscule components they would require are getting ever closer. Scientists have already made nanosized springs but it hasn't been easy to make them out of single metal wires, until now. Metallic nanosprings, analogous to the macrosized springs we use extensively in everyday life, are desirable due to metal's flexibility and resilience.

Metal nanosprings offer flexibility and resilience

Most nanosprings made so far have been naturally coiled and required energy to be straightened out. But Hongyu Chen and his team at Nanyang Technological University and the National University of Singapore, have made springs that instead release energy when uncoiled.

To make the springs, the team encapsulated gold nanowires in a polymer container called a micelle. The solvent around the micelle was then changed causing it to shrink in size. Each micelle was found to contain a single coil of five to 10 loops, and the team believe that the micelle shrinkage triggered the coiling up of the wire. When the polymer is removed - or the micelle is allowed to swell again in an appropriate solvent - the springs straighten back out, releasing energy.

'We wanted to make the wires fold into random coils by crumpling them in a restricted volume and we were surprised when we found that the springs were ordered,' explains Chen.

Christoph Weder, professor of polymer chemistry at the Adolphe Merkle Institute in Fribourg, Switzerland, thinks that the concept is an exciting one. 'The wire is only indirectly involved with the self-assembly process, which makes this an interesting concept - they are not trying to manipulate the wire growth directly but exploit the assembly of the polymer,' he says. Weder sees the method being used to induce coiling in other materials too.

Chen believes that multiple component systems are the way forward for nanotechnology. 'With this combination of two components we have been able to achieve something that cannot be achieved with any of the single components,' he says. Chen hopes that this is another 'tree in the forest' of nanofabrication.

Carol Stanier


Visualising DNA sequences

16 August 2010

A new, fast way to analyse DNA has been developed by European scientists that could be used to sequence the genomes of viruses and in the future help tackle genetic disorders such as schizophrenia and congenital heart defects.

Current DNA sequencing methods are able to sequence short regions of the genome (302 to 15002 bases in length). Regions that are either duplicated or deleted relative to a reference genome are an important cause of structural variation in the human genome with links to a variety of genetic disorders. Using current sequencing methods, studying these repeats is time consuming and labour intensive.

Now, Robert Neely and colleagues, at Catholic University Leuven, Belgium, have used a DNA methyltransferase enzyme to label the 5'-GCGC-3' DNA sequences with a fluorescent marker. Immobilising and stretching the DNA on a surface then produces a unique and reproducible pattern when combined with the fluorescent markers. The result is a 'fluorocode' - a simple description of the DNA sequence, which can be read and analyzed like a barcode.

Sequences of DNA are tagged with a fluorescent marker

DNA barcodes using fluorescent tagging can be read quickly as labelled samples pass a detector, but Neely's fluorocode gives significantly enhanced resolution and uses a much smaller number of DNA molecules. 'The method from unlabelled DNA to fluorocode can be achieved in less than 8 hours for a DNA molecule that is around 50000 bases in length' says Neely. Current single molecule mapping methods have a timeframe of around one week for analysing individual genomes.

Kalim Mir, an expert in DNA sequencing and genomics at the Wellcome Trust Centre for Human Genetics, University of Oxford, comments, 'the advantage the system has over conventional optical mapping is that it can provide ultra-high density mapping of genomic DNA and could easily be extended to much longer fragments from larger genomes, from bacteria to humans. The most significant challenge the authors face is to scale the technique up to the human genome.'

The group now plan to scale the fluorocode up from viral genomes to bacterial and on to eukaryotic genomes with the immediate aim of producing multi-coloured fluorocodes with even more detail.

Carl Saxton


Zooming in on intermolecular bonds

13 August 2010

German researchers have captured clear images of intermolecular bonds for the first time using a modified form of scanning tunnelling microscopy (STM). The technique could help scientists studying the functionalisation of surfaces with molecules to develop new materials including semiconductors and fuel cells.

Stefan Tautz and colleagues at the Jülich Research Centre in Germany first demonstrated the technique in 2008 when they produced images of various phases of the aromatic hydrocarbon molecule 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on a gold surface.1 By dousing the tip of a low temperature scanning tunnelling microscope with liquid hydrogen, images of the molecule's internal structure were produced that looked remarkably like textbook drawings of atomic structures.

Now, the team have gone a step further and optimised the scanning tunnelling hydrogen microscopy (STHM) technique to image the types of interactions occurring between PTCDA molecules on a gold surface.2 'This has been impossible up to now with any method that I am aware of,' says Tautz. In the latest experiments, the team condensed deuterium at temperatures between 5 and 10 Kelvin at the microscope's tip and doped the gold surface with potassium.

STM image (left) and STHM image (middle) of PTCDA on a K-doped Au surface. Right: STHM image with structure formulas of PTCDA superimposed
© J. Am. Chem. Soc.

The resulting images produced much greater contrast than an STM with a bare tip to reveal local, noncovalent intermolecular interactions of a PTCDA molecular layer. The team managed to resolve two bonds (O · · H-C and O · · K) which appear as thin lines or as sharp boundary lines between areas of different brightness. 'Although the mechanism is still not completely clear, we seem to have a handle now to actually visualise these interactions directly,' says Tautz, 'That certainly makes a big difference for studying the functionalisation of surfaces with molecules if this can be confirmed for other systems.'

Leo Gross at IBM Research in Zuruich, Switzerland, who earlier this month reported a new technique to image molecular structures using atomic force microscopy, thinks the new study is an important development. The images obtained by the STHM technique show remarkable intramolecular resolution and greatly advance the investigation of molecular monolayer structures,' he comments.

'I think it has the potential of becoming a method which is complimentary to ordinary STM but which can also be carried out on the same instrument which is a very big advantage,' Tautz adds. 'If you have the instrument already in your lab then it is very cheap and simple thing to do.'

James Urquhart


Electrochemical sensor for toxic compound

13 August 2010

Scientists develop a highly efficient and chemically stable hydrazine sensor using carbon modified zinc oxide nanorods.

Hydrazine, N2H4 is highly neurotoxic and carcinogenic and can cause sever damage to the liver, lungs and kidneys. It is used extensively in industry, primarily as a foaming agent in the manufacture of polymer foams, as well as a precursor in the synthesis of catalysts, agrochemicals and pharmaceuticals. Therefore, for safety considerations, a reliable hydrazine sensor is highly desirable.

Of the wide range of hydrazine detection techniques reported, electrochemical devices are the most promising since they are low cost, portable and generally offer fast response times and good sensitivity. Nanoparticle modified electrodes, such as zinc oxide nanostructures, are particularly advantageous because of their increased surface area, reduced resistance and a high signal-to-noise ratio. But, while highly sensitive the electrodes are insufficiently stable in various electrolytes for practical application.

Carbon-modified zinc nanorod array has impoved sensing ability

Jinping Liu and colleagues at Huazong Normal University in China have overcome this problem by coating zinc oxide nanorods in a layer of carbon just a few nanometers thick using a simple immersion-calcination method. The high electrical conductivity of carbon improves the sensitivity of the sensor by facilitating the electron transport related to hydrazine oxidation. In addition, the chemical inertness of carbon improves the stability of the sensor by protecting the ZnO nanorod from corrosion by the electrolyte.

'While the sensitivity and stability of sensor have been improved, our electrode design also avoids conventional electrode fabrication processes, which are typically laborious and expensive,' adds Liu.

Gregory Wildgoose, an expert in carbon nanotube surfaces for enhanced sensing and catalytic applications at the University of East Anglia, comments, 'the synergy between the amorphous graphitic coating and the underlying ZnO material that gives rise to improved electroanalytical performance when compared to vertically aligned carbon nanotube arrays is intriguing. There are clearly some interesting nano-scale interactions occurring in this system worthy of further investigation.'
The fabricated electrode may also find application in other devices such as batteries and photoelectrochemical cells. Liu says, 'the next step is to further optimise the synthetic techniques to allow very large-scale, uniform and reproducible growth of carbon coated nanorod arrays directly onto the current collector.'

Jacob Bush


Light-rechargeable batteries

11 August 2010

Researchers have developed a new molecular system that could be used as the basis for a battery that can be recharged by light. In the system, light generates charge which is then stored until it is needed. In an ordinary photovoltaic cell, the charge must be used immediately or it rapidly becomes neutralised.

The team, led by Ifor Samuel at the University of St Andrews in the UK, synthesised tree-like organic semiconducting dendrimer molecules with a cationic cyanine-based core associated with an iodide anion. The organic semiconductor and iodide are blended together into a layer between two contacts.

The team used dendrimer molecules with a cationic cyanine-based core associated with an iodide anion (pink) in the photo battery device
© Adv. Mater.

Upon exposure to light, the cyanine core absorbs light, forming an excited state that is initially neutral - an exciton. Charge separation then occurs as a result of an electron being transferred from the anion. The researchers suggest that charge can be stored because the charged state of the cyanine results in a stable conformational isomer. Upon completion of a circuit, the charge moves to the contacts and the system discharges.

'For test purposes we did ten charge and discharge cycles and saw little degradation,' says Samuel. 'So we expect it, like a battery, to be able to sustain far more.'

Samuel says that the amounts of stored power are, as yet, small. 'So far it is an exciting proof of principle. However, most technologies start like that and it is reasonable to expect large improvements with further work.'

Samuel says that a photo-rechargeable battery system would be useful because while solar power is abundant, it is not always available - for example at night. 'There is a real need to generate power and then store it. The interest of our device is that it combines both functions. That makes it more compact, easier to make and easier to integrate into electronic devices such as calculators.'

Hiroyuki Nishide, an electronic materials expert from Waseda University in Japan, says, 'Although the energy and power densities need to be increased, this new idea of a battery configuration could be one of the special features to stimulate further studies on organic materials for energy-related applications.'

Simon Hadlington


Nanoparticles and ultrasound team up to treat tumours

03 August 2010

A new, non-invasive method to deliver drugs to the brain has been developed by Taiwanese researchers. Using a combination of magnetic nanoparticles and focused ultrasound to pinpoint specific areas, the technique could be very helpful in treating brain tumours.

'The difficulty with treating brain tumours is that the brain is protected by the blood-brain barrier,' explains Pin-Yuan Chen, who led the research at Chang Gung Memorial Hospital in Taiwan. 'This prevents chemotherapy drugs from entering the brain. However, we can open up this barrier in desired locations using focused ultrasound. This allows us to target our treatment effectively and safely.'

Chen's team injected magnetic nanoparticles coated with therapeutic compounds into rats, then applied an external magnetic field to increase the concentration of the nanoparticles in the brain. Next, a low-energy burst of ultrasound was targeted on desired areas, which increased the permeability of the blood-brain barrier and allowed the nanoparticles to diffuse through across. The effect of the ultrasound is temporary, and the barrier returns to normal after a few hours.

Ordinarily the blood-brain barrier would prevent nanoparticles crossing to the brain (A), but ultrasound can disrupt the barrier so that the particles can diffuse across (B) and using magnetic targeting helps direct the particles to the desired location (C)
© Proc. Natl. Acad. Scis. USA

The advantage of using magnetic nanoparticles is twofold. Firstly, since the nanoparticles can be localised in the brain, far smaller doses are required, which would dramatically reduce any side-effects from the treatment and potentially allow stronger drugs to be used.

Secondly, the magnetic particles show up on magnetic resonance imaging (MRI) scans, so that doctors can follow the progress of the treatment and monitor drug concentrations in the brain. This is important because tumours can have widely differing morphologies and may take up the drug in different amounts.

Chen notes however that further research and development will be needed before the treatment finds its way into hospitals. In particular, the safety of the nanoparticles needs to be assessed as well as determining the best way to apply a magnetic field to localise nanoparticles in the brain.

'This is a fascinating article,' says Jinwoo Cheon, who develops magnetic nanoparticles for cancer treatment at Yonsei University in Seoul, South Korea. 'Many people in nanomedicine have been pursuing so-called "theranostics" - which is therapy plus diagnostics - as a next generation concept that will be essential for personalised medicine with high efficacy. I would say this is one of the most significant successful showcases in this research area.'

Lewis Brindley

No nanotube fertility risk

08 August 2010

US and Chinese researchers have found that carbon nanotubes injected into male mice cause damage to the testes, but the harm is reversible and does not affect fertility.1 The work adds to the growing debate over the toxic effects of carbon nanotubes and their potential use for biomedical applications such as drug delivery vehicles.

Previous reports have suggested that carbon nanotubes could be as toxic as asbestos,2 while other work has shown that an enzyme present in human immune cells can break down nanotubes.3 Yet other studies on mice have shown that carbon nanotubes could cause cancer and lung damage.4

Now, Bing Yan at St Jude's Children's Research Hospital in Memphis Tennessee, and colleagues in China have investigated the toxicity of carbon nanotubes on the reproductive system of male mice. The team administered up to 5 intravenous doses of water-soluble multiwalled carbon nanotubes to mice over a period of 13 days. Within 24 hours, nanotubes were found in the testis. By day 15, the nanotubes had caused oxidative stress and tissue damage, but by days 60 and 90, the damage had been repaired with no observed effects on hormonal levels, sperm health, or fertility.

The researchers found that administering carbon nanotubes had no long-lasting effects on the mouse reproductive system

'We revealed effects of carbon nanotubes on male reproductive health at molecular, cellular, organ, and animal levels and provided a solid foundation for defining a safe dose for carbon nanotube use in humans,' says Yan. 'Our work paves the way for safe development of numerous medicinal applications of carbon nanotubes in terms of male reproductive safety.'

Krzysztof Koziol who works with carbon nanotubes at the University of Cambridge, UK, agrees that the work shows promise. 'Carbon nanotubes have the potential for a wide range of biomedical and pharmaceutical applications, therefore it is very important to demonstrate any possible health risks,' he says. 'Importantly, the paper demonstrates no effect of surface treated nanotubes on the function of the animal reproductive organs, with respect to normal production of hormones and sperm.'

However, toxicology expert James Bonner at North Carolina State University in Raleigh, US, still has concerns over using carbon nanotubes for drug delivery. 'The authors clearly showed cellular stress and damage to cells in the testes, and while this effect was repaired and didn't ultimately affect fertility, the study suggests to me that longer exposures, as would be used for drug delivery, might ultimately affect fertility.'

Yan admits that higher doses and a more frequent dosing schedule would likely result in cause for concern in terms of reproductive toxicity, adding that further studies on the reproductive toxicity of nanomaterials are urgently needed. 'How to evaluate the combined effects with other pollutants and factors and how to realise a quicker evaluation of nano-reproductive toxicity are all challenges facing future research in this area.'

James Urquhart

Wet batteries power up

08 August 2010

The performance of water-based lithium-ion batteries has been greatly boosted by removing oxygen from the power cells, report Chinese researchers. Safer and cheaper than conventional solvent-based batteries, the aqueous cells have great potential for large-scale applications, such as storing the power from wind turbines or solar panels.

Lithium-ion batteries are ubiquitous in consumer electronics - from mobile phones to laptops - but the toxicand flammable organic solvents contained inside can be a safety hazard. Manufacturing is awkwardand expensive, and in cases of overcharging or short-circuiting they can rupture or catch fire. This is of particular concern when scaling up the batteries for larger applications such as car batteries or power generation.

The batteries are made from two electrodes held in a liquid electrolyte - typically an organic solvent such as ethylene carbonate. On charging and discharging, lithium ions move through the electrolyte between the two electrodes.

Lithium-ion batteries are used in many consumer products, but their components can be a safety hazard

Switching to a water-based electrolyte would be cheaper and safer - and is feasible using specially-designed electrodes - but water-based batteries have not been as reliable as their organic counterparts. Until now, the best aqueous cells to be developed lose around 50 per cent of their storage capacity after being recharged 100 times.

Now, researchers believe they have pinned down the cause of the poor stability. 'The materials used to make negative electrodes react with water and oxygen when discharged,' explains Yong-Yao Xia, who led the research at Fudan University, Shanghai, China. 'By completely eliminating oxygen from the system and using carbon-coated electrodes, we were able to greatly improve the stability.'

Xia's team used carbon-coated electrodes of lithium iron phosphate (LiFePO4) and lithium titanium phosphate (LiTi2(PO4)3) and ensured that the cells were as oxygen-free as possible. With these modifications, the battery performance dramatically improved - showing the ability to retain 90 per cent of capacity after being discharged and recharged over 1000 times.

'This is a big step forward, but there is still a long way to go before these batteries find practical applications,' Xia told Chemistry World. We now plan to hunt for electrode materials that cannot dissolve in the water - or find a surface modification that reduces this process even more.'

'Due to the energy density of water, aqueous lithium-ion batteries store less power than organic-based batteries, but reducing the price and solving the safety issues are very important,' says Yi Cui, an expert in battery design at Stanford University in California, US. 'The batteries probably won't replace the ones that are currently used in mobile phones - but they have big advantages for larger scale energy storage.

Lewis Brindley


Fast Forensic Test Can Match Suspects' DNA With Crime Samples in Four Hours

ScienceDaily (Aug. 5, 2010) — A newly developed test could make checking DNA from people arrested for crimes with DNA samples from crime scenes stored in forensic databases almost as easy as matching fingerprints. With the test, police could check on whether a person's DNA matches that found at past crime scenes while suspects are still being processed and before a decision on whether to release them on bail. A report on the fast forensic test appears in the ACS' Analytical Chemistry.

Andrew Hopwood, Frederic Zenhausern, and colleagues explain that some criminals are arrested, spend less than a day in jail, and then commit crimes while they are out on bail. If police could quickly test the suspects' DNA, to see if their genetic material matches entries in crime databases, they may be able to keep the most dangerous people locked up. But currently, most genetic tests take 24-72 hours, and by the time that the results are back, the suspects often have been released.

To increase the speed of forensic DNA testing, the scientists built a chip that can copy and analyze DNA samples taken from a cotton swab. Forensic technicians can collect DNA from suspects by swabbing their mouth, mixing the sample with a few chemicals, and warming it up. The DNA-testing-lab-on-a-chip does the rest. The entire process takes only four hours at present. Hopwood and Zenhausern teams are already optimizing it and reducing the cycle time down to two hours. Once that is done, police could even double-check their DNA evidence before releasing a suspect.


Dry Moon discovery

05 August 2010

Was there water on the Moon when it first formed? US geochemists say the distribution of chlorine isotopes in lunar rocks suggest not, or at least not as much as other recent studies have proposed.1

Zach Sharp from the University of New Mexico in Albuquerque is quick to point out that his team's study relates to the Moon's interior, rather than water on the surface that may have been deposited by cosmic dust and comets or formed by proton bombardment by the solar wind. However, two studies published earlier this year2,3 indicated that there was water present when some lunar rocks formed.

Sharp's findings hinge on the distribution of the two stable isotopes of chlorine, 37Cl and 35Cl. On Earth, Sharp explains, the ratio of the two isotopes is very homogeneous, varying by at most about 0.1 per cent.

Is the Moon dry inside?

This is because the magma or lava that forms rocks on Earth contains quite a lot of water - in which chlorine is very soluble - so the chlorine is always given off as HCl gas. 'The H-Cl bond is very strong [compared to the bonding in the magma], so it preferentially incorporates 37Cl; but the lighter, faster moving 35Cl is lost into the vapour preferentially,' says Sharp. 'These two effects tend to cancel out, so the isotope ratio stays the same in the HCl and the remaining rock.'

What the team found when they looked at samples brought back by the Apollo Moon missions, was that the isotope ratios varied by 25 times as much as in Earth materials, with most of the samples being enriched in 37Cl relative to Earth samples. 'That was quite a shock,' says Sharp, adding that they had to check their analysis very carefully to verify the huge variation. 'The only explanation we could come up with that matches all of our observations was that the lunar magmas were anhydrous.'

If there was no hydrogen (in the form of water) around on the early Moon when the magmas were cooling and crystallising, then chlorine would not be vaporised as HCl but as metal chlorides. 'But the bonding in those metal chlorides is about the same strength as in the magma,' says Sharp, which means the force driving vaporisation of 37Cl is eliminated and 35Cl ends up being removed preferentially as its lightness and mobility wins out. He adds that the theory fits with other observations that have found deposits of metal chloride salts on the surface of Moon rocks.

'The way we think the Moon formed requires a vastly dry source, depleted of volatile elements. If you don't have that, nothing else makes sense' says Steve Mojzsis, a geochemist from the University of Colorado, US. He adds that if Sharp's team are correct, it's possible that the water that other teams have found comes from a shallow subsurface layer that has been contaminated with water from an exogenous source, but that would be hard to test. 'If we can explain that the interior of the Moon really is dry,' says Mojzsis, 'then that helps put some of the pieces together.'

Phillip Broadwith