Nanosheets Soak Up Spills

My eleventh news bit for the awesome Naked Scientists – originally appeared here (you can also listen here too): http://www.thenakedscientists.com/HTML/news/news/1000158/

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A material capable of absorbing up to 33 times its own weight in oils and organic solvents has been developed by scientists in Australia.

The clean-up of oil spills has historically been an expensive and lengthy process, and recent large-scale spillages – such as that from the Deepwater Horizon oil rig in 2010 – highlighted the urgent need for new and reliable water cleaning techniques. Freshwater supplies are also at risk of contamination with organic solvents and dyes discharged by the textile, tannery and paper industries.

But a solution may be in hand. A group from Deakin University in Australia, led by Ying Chen, have developed a porous boron nitride nanopowder, capable of rapidly soaking up over 30 times its own weight in oils, organic solvents and dyes.

To work like this, a material must have a high capacity and large surface area, it must be capable of accommodating high strains (so that it can swell up), and it should be lightweight and easy to separate from water. The material made by Chen and his team ticks all of these boxes.

Their powder consists of individual sheets of boron nitride (BN). At just 1.1 nanometres thick, they’re thousands of times thinner than the average human hair. Large pores in each sheet gives the material an incredibly high surface area, allowing it to absorb large quantities of dyes. The BN nanosheets are also hydrophobic, meaning that they repel water and can float on the surface of a spill. Chen also found that when the sheets absorbed engine oil, they could swell by up to 37%, but without causing long-term damage to the structure of the sheet.

1 g of the nanosheets can absorb up to 33 g of impurities; everything from solvents like ethanol and toluene, to heavy-duty engine and pump oils. The process is also very fast; according to Chen, “After just two minutes, all oil has been taken up by the nanosheets”.

BN nanosheets are also cost effective – the raw materials are inexpensive, and the production of the final flakes follows a standard industrial process, according to Weiwei Lei, another author of this study. Once the sheets are saturated by the spill, they can be easily collected, cleaned by burning, heating or washing, and recycled, ready to be used several times more.

Other efficient absorption materials for water purification exist, but these are based mostly on carbon. Currently, only these BN nanosheets offer a low- cost, high-capacity, recyclable material which is suitable for use on a wide range of pollutants. Lei is confident that they can scale up their production process, saying “I can’t see much technical obstacle from large-scale application”, so it shouldn’t be too long before we see these nanosheets on the market.

References

• Porous boron nitride nanosheets for effective water cleaning. Lei, W et al.

A Boy and His Atom

I’m sure you’ve already seen this – the smallest movie ever made, by scientists at IBM. But I LOVE it, so I just wanted to stick it on my blog.

http://www.youtube.com/watch?v=oSCX78-8-q0

And I’m sorry to be pedantic, but what you see are not atoms, they are pairs of atoms – each ball is a carbon monoxide molecule, one atom of carbon and one of oxygen, stacked on top of each other. The molecules are moved around on a copper plate using a scanning tunelling microscope, or STM (a technique actually invented by IBM scientists in 1986, but now used by scientists all over the world).

As someone who uses STM, along with its sister technique atomic force microscopy, I have some idea of just how difficult and time-consuming this would have been to do. So I am very very impressed by this.

And for those of you who will say “Don’t scientists have something better to do?” etc, I say NO. For me, science is about two things – dialogue and exploration.

A project like this summarises those two things wonderfully – it probably started as a chat over lunch or a beer….wouldn’t it be cool if we could try this? Cue an afternoon playing around in the lab, just to see, just to explore all possibilities.

And as a scientist and science communicator, this kind of thing makes me very happy – just have a look on Twitter for the hashtag #aboyandhisatom – look at the huge numbers of people talking about this video, look at the countries they’re from, look at their profiles…. all sorts of people, all talking about atoms and molecules. Dialogue win

No More Droopy LEDs?

This is a piece I wrote and chatted about on the Naked Scientists podcast last week. It also marked my TENTH appearance as their physics / tech reporter-type person

It originally appeared here: http://www.thenakedscientists.com/HTML/news/news/1000148/

Reducing the Droop in LED Efficiency

Wed, 24th Apr 2013

A team from the University of California, Santa Barbara (UCSB) have answered an important question in LED performance – called ‘efficiency droop’ – which has limited the development of high-performance LEDs, capable of replacing incandescent and fluorescent bulbs.

Light Emitting Diodes (LEDs) are highly efficient, durable, and long lasting, and they’ve found uses in everything from remote controls to traffic lights. Unlike incandescent and fluorescent bulbs, they don’t have a filament that will burn out, they don’t get particularly hot, and with a lifetime of tens of thousands of hours, they greatly surpass the performance of an incandescent bulb.

But LEDs have traditionally suffered from an effect called ‘efficiency droop’, a drop in the light output of an LED that occurs when a high current is applied to the device. This has meant that an LED’s “cost per lumen” – a metric that reigns supreme in the lighting world – is higher than that of the more traditional large-scale lighting solutions, and this is holding back the more wide scale implementation of this novel light source.

Now this may be about to change. In 2011, a team led by Chis van de Walle at UCSB, theorised that behind this droop was a complex non-radiative process called Auger recombination. When this happens, the charge carriers in the LED material, known as electrons and holes, lose energy as heat rather than light. Now a team led by another UCSB scientist, Claude Weisbuch, has proved the theory by analysing the electron emission spectrum of Indium Gallium Nitride (InGaN) LEDs.

In their paper, in Physical Review Letters, they study an LED made using thin layers of GaN-based material grown on a sapphire surface. By measuring the LED’s light intensity, while directly observing the energy spectrum of electrons emitted from the device, Weisbuch and his team confirmed that Auger recombination was the culprit of the efficiency droop. The charge-carriers (electrons or holes) were interacting without giving off light, fully accounting for the drop in LED efficiency at higher currents.

In LEDs, electrons and holes are continuously created. When they recombine into electron-hole pairs, they release energy in the form of light, making recombination fundamental to an LED’s operation. In nitride-based LEDs, three- particle – or Auger – interactions can also occur. Here, although an electron-hole pair is created, the resulting energy is not released as light, but instead promotes an unstable electron into a higher energy level – i.e. it heats that electron up. As you increase the current applied to an LED, you increase the number of unstable high-energy electrons in your material, increasing the change of forming a three-particle interaction.

Although this recombination effect cannot be eliminated, it can be minimised by engineering new materials designed specifically to combat it. So this study is likely to lead to new LEDs with significantly higher light emission efficiencies.

The U.S. Department of Energy recently estimated that 12% of total U.S. electricity consumption is is used for lighting, so this development has far wider implications than just the academic. Higher-efficiency LEDs have enormous potential for use in long-lived, reliable lighting for residential and commercial applications.

• “Direct Measurement of Auger Electrons Emitted from a Semiconductor Light-Emitting Diode under Electrical Injection: Identification of the Dominant Mechanism for Efficiency Droop”, Iveland, J et al.

My TEDx appearance

I promised that I would share my TEDx video when it appeared on YouTube.

So here it is!

http://www.youtube.com/watch?v=eKziv1x4DMw

PS: I really REALLY don’t like watching myself

Super-Strong Spider Silk

This is a blog post I wrote for Materials Today last month – it originally appeared here: http://www.materialstoday.com/blog/2013/4/3/super-strong-spider-silk-laurie-winkless/852.aspx

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Spider silk has often been regarded as one of Nature’s “wonder materials”, with an unmatched combination of low density, high extensibility and enormous tensile strength, five times greater than that of steel. Historically, the physics of spider silk has been poorly understood, due to the complexities of measuring these fine fibres. But as efforts to develop a synthetic equivalent to spider silk intensify, the search to find the secret of the fibre’s extreme toughness has picked up pace.

Spider silk consists of long chains of repeating protein sequences, which are stored in the silk gland in a highly concentrated form. The silk gland also contains a high concentration of salt, which prevents the formation of threads inside the duct. It’s only when the protein molecules move into the spinning chamber – just before being used – that they start to orient into the long chains recognisable as spider silk.

In late 2011, a team at the Technical University of Munich were the first to demonstrate that during the spinning process, it was a change of pH, combined with a removal of salt that allowed the silk proteins to form into crystallites and assemble into cross-linked fibres. And it is this cross-linking that ultimately gives spider silk its high tensile strength.

A recent paper in Nature Materials has also added a major piece to the puzzle – a team from Stanford have become the first to measure the complete first-order mechanical response of spider webs, a measurement consisting of five independent elastic constants. And they have done this using a century-old technique called Brillouin spectroscopy. The team also directly measured a huge increase in the silk stiffness in the presence of high humidity – a property of spider silk called supercontraction that had been known but never previously measured. Their non-contact, laser-based technique also found some ‘unknown unknowns’ – the stiffness of a web was found to greatly vary between threads, junctions and glue spots, an unexpected result in what was thought to be a uniform fibre.

The human fascination with spider silks may stretch well beyond the scientific – webs are found everywhere from fashion to superheroes – but it is the silk’s impressive mechanical properties that interests materials engineers. By learning more about spider silk, we may be able to engineer new materials that mimic, or even go beyond, those that exist in nature.

Guitars

For someone who doesn’t actually play guitar, the instrument seems to play a rather important role in my life. I am lucky enough to live with three particularly handsome guitars, along with an even more handsome player-of-guitars

And I just love them. How they look. How they sound (when played properly). And, at the risk of sounding a bit philosophical, I love what they represent – I see them as an incredibly intimate way to tell stories, and as a passport to the world – music and maths are the only truly international languages – so I’m envious of those who use them to bare their soul.

Aren’t they gorgeous?

But when those storytellers are young, or at least younger than me, my envy turns to pride. That they have found an outlet, a friend, that adds so much to their lives, and that they choose to introduce us all  to them through their music.

Mark Durnin is a young musician from my hometown – Dundalk, Ireland, who is now based in Glasgow. He has been described as “an exceptionally talented singer/songwriter…who’s lyrical poetry and subtle, sweet melodies will engulf the senses” (Dundalk Leader). Yep, I agree on all fronts. But I think that Mark’s real talent lies in his ability to speak directly to you, and you alone. It’s rare to find someone who brings you into their songs, rather than expecting you sit back and enjoy them. And Mark’s lyrics are wonderful, so…. effortless. The combined effect is that after a set, you feel like you know and understand him, not just that you liked his stuff.

See, I DO know Mark. Very well in fact. He is my nephew, making me his proud auntie Mark has been a guitar man for a long time, and had been in several bands as a teenager. And we’re a pretty musical family (I blame the parents), so I always assumed he’d be good. But honestly, when I first went to one of Mark’s gigs, I was completely blown away, and I continue to be, every time he pops up on my iPhone.

As a starter, may I recommend this SoundCloud page: https://soundcloud.com/mark-durnin/sets/acoustic-recordings-1 - it will give you all a flavour of just how bloody brilliant Mark is. You can thank me later  Or better yet, you can buy his stuff!

My second young guitar storyteller is Jodie Goffe, a 17-yr old singer songwriter from Balham, South London, who is in the midst of prepping for her A-levels. Jodie is signed to Smugglers Records, who describe her as having “a presence, poetry and wisdom well beyond her years”. I totally agree – Jodie is an old soul. Teenagers get a pretty tough time of it these days, constantly accused of being stupid, lazy, useless. Jodie’s music shows that, at least in her case, those ridiculous stereotypes are WAY off. She writes and performs like someone who has lived several lives, instead of being pretty close to the start of just one.

I’m also lucky enough to know Jodie very well. Mark is part of my ACTUAL family, but Jodie is part of my London family – the wonderful group of people I have been lucky enough to gather around me in my (almost) eight years in this great city. I used to tutor her big sister Ellie – herself a talented performer – and I help Jodie out with exam practise on occasion too. I’m hoping that on her gap year, Jodie will find time to write some more wonderful music, but in the meantime, here is her Soundcloud page – listen and enjoy: https://soundcloud.com/jodiegoffe

My love and I recently spent a happy afternoon in a guitar shop in Bath, and then another in one on Denmark Street. That time, we came home with a hollow-body-Gretsch (middle one in the picture), and every time he gets his dexterous hands on it , I smile. That’s the power of music I think, and especially guitar-driven music (for me). It’s the emotion, of both the performer and of those of us lucky enough to listen.

I’ll leave you with a beautiful song from John Denver – my love introduced me to this, and I will be forever thankful. Just wonderful. Enjoy  http://www.youtube.com/watch?v=m__yVh5h3e0

Naked News – Thurs 4th April – Lithium Batteries Get a Sulphur Makeover

This story originated from Germany, and it’s all about the development of lower-cost (and potentially safer Lithium-based batteries) for use in the car industry. It was part of a great series of news stories – you can listen to / download the whole show here: http://www.thenakedscientists.com/HTML/podcasts/naked-scientists/show/20130404/

Story originally appeared here: http://www.thenakedscientists.com/HTML/news/news/1000128/

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German scientists have designed a high-efficiency, low-cost lithium-sulphur battery, which they believe will increase the use of electric vehicles in Germany and beyond.

Earlier this year, the UK government announced an £11M investment in public and private charging points for electric vehicles, which, its hoped will help increase the popularity of electric cars. At present though, the numbers are still small. According to Germany’s Federal Ministry of Transport, there are over 40 million cars on the country’s roads, but only a tiny fraction of them – around 6,400 – are powered by electrical energy.

The high price of both batteries and vehicles may be a factor in this low uptake, but a more real concern is the comparatively short range of electric cars – their lithium-ion batteries need to be recharged after just 100 km of driving. But a team at the Fraunhofer Institute in Dresden have developed a new lithium-sulphur battery, which is significantly more powerful and less expensive than the standard Li-ion batteries.

Previously, lithium-sulphur batteries have had such short lifetimes (just 200 charge-discharge cycles) that they’ve been unsuitable for use in cars, but the team’s new design increases the lifetime of lithium-sulphur batteries by a factor of seven. They have done this by altering the standard combination of anode and cathode material in a lithium battery. The interaction between these electrodes and the liquid electrolyte between them is the critical factor in determining a battery’s performance.

The team, led by Dr. Holger Althues, replaced the usual lithium anode with one made from a silicon- carbon compound, which is much more stable during the charge-discharge cycle. This improved stability reduces the risk of unwanted interactions between the anode and the electrolyte, which, in extreme conditions can lead to a fatal short circuit within the battery. In lithium-ion batteries, the main cathode material is cobalt, a rare, and therefore expensive, material. The Fraunhofer team have replaced the cobalt with elemental sulphur, greatly reducing the cost of the battery. And they have introduced porous carbon into the electrode, which traps the sulphur within the pores, slowing down interactions between the sulphur cathode and the electrolyte.

Suitable large-scale manufacturing methods for these Li-S batteries are now under review, but Althues has also shown that, with further optimisation, the energy density of their lithium-sulphur battery can reach 500 Wh/kg – more than double that of the lithium-ion batteries currently in use in electric cars – meaning that for the same weight of battery, you could drive double the distance.

• Research news: A longer life for lithium-sulfur batteries