Meera Senthilingam: Welcome to the Diamond Light Source Podcast with me, Meera Senthilingam. This month we’re understanding and protecting our planet as we discover the latest developments in environmental science. We’ll be finding out how bacteria can be used to clean up arsenic contaminated water in Bangladesh as well as discover a new form of solar cell made of plastic that will, hopefully, make this renewable source of energy available to all.
David Lidzey: Soon you can go down to your local DIY supermarket and buy a roll of this stuff and pin it to the side of your house and produce your electricity very cheaply.
Meera: David Lidzey will be explaining how this solar cell will work later in the show when we go back to the problem of contamination and discover a new hero in the form of green rust
Sam Shaw: The special properties of green rust are that it is able to immobilise particular contaminants by changing their chemical state and thereby reducing their impact on the environment and potentially be applied to remediate contaminated sites.
Meera: Sam Shaw will reveal how this green rust can be produced to clean up contaminated landsites. So lots of insights into cleaning up and reducing our impact on our environment, plus the latest news and events from Diamond, coming up in this September edition of this Diamond Light Source Podcast.
Meera: These days, we’re all aware of our environment. We recycle our cardboard, plastics and more, try to use our cars less and switch off our lights and our taps when not in use. The Scientists at Diamond are trying to help our environment too in a variety of ways, as Fred Mosslemans, Principal Beamline Scientist on the microfocus-spectroscopy line explains –
Fred Mosselmans: Well there are about 4 or 5 beamlines that have a lot of environmental science applications at diamond and there are other ones that do technology related to alleviating the effects of climate change, but the 3 or 4 main environmental science beamlines are the x-ray spectroscopy beamlines which are used to look at the oxidation state and the speciation, that is what form a metal or a different pollutant is in, in an environmental sample, say a soil sample from contaminated land waste. Then there’s another beamline which uses a technique called small angle scattering to look at development or various particles in waste streams and ways of developing remediation technology for the waste that’s in those streams and then there’s a big interest in the use of bacteria and bugs to clean up waste, and so one of our beamlines is an infrared beamline and that uses an infra-red microscope to look at organic parts of bugs and stuff and work out how they interact with different parts of the environment.
Meera: So there’s a wide range of environmental science taking place, but the key thing seems to be looking at contaminants and minerals and elements actually in our environment?
Fred: Yes, a key aspect of the synchrotron is its ability to look, in very great detail, at different mixtures. So soil is made up of lots of different materials and with a small sized synchrotron beam and our high resolution detectors we can look at individual particles of soil to tell what the contaminant phase is in its individual particles which can lead to better strategies to remediate and clean up the particular topic material we are looking at.
Meera: You’re the Principal Beamline Scientist on the microfocus spectroscopy beamline and we’re actually by that now in the control cabin area. Tell me a bit more about this particular beamline, what is microfocus spectroscopy and what kind of things does it enable you to look at?
Fred: A microfocus spectroscopy beamline focuses an x-ray beam down to about 2 microns. 1-2 microns, so that’s somewhere between 180th and 140th of the width of a human hair. We can then look at heterogeneous materials. Heterogeneous materials are basically, well soil is a heterogeneous materials, it has various different phases, so you have various iron minerals, manganese minerals, organic matter in very small particulate form. So if you go to a normal beamline, say which has a beamline size of half a millimetre, you end up looking at a lot of different materials. While with a microfocus spectroscopy beamline you can, by moving the sample in front of the beam, you can look at just one particular soil particle. In South East Asia there’s a very large problem with arsenic contaminating the water supply and the people that live in say Bangladesh, and what have you, have severe arsenic toxicity problems and there’s a group from Manchester who’ve been looking at the ways of possibly remediating this and understanding why that problem occurs using spectroscopy and now x-ray microfocus spectroscopy to understand. In particular, they are looking at ways they can use bacteria to make the arsenic insoluble, so depositing bugs in the wells to try to oxidise the arsenic and make it insoluble. So even if you put a well into arsenic contaminated land you can put some sort of filter with bugs in it that will change the arsenic and therefore coming out of the well is still clean water.
Meera: When looking at particular bugs that can be used for this remediation, is that done here at the beamline as well? Is that interaction possible to be seen at the beamline using spectroscopy?
Fred: On our beamline we can’t actually look at the bugs themselves, because the bugs are generally organic matter and this beamline can only really look at elements from about Sulphur upwards in the periodic table. We can look at the effects of bugs, we can look at the arsenic before the bugs have treated it, after the bugs have treated it and tell the oxidation state and what mineral phase it’s associated with, but we can’t actually look at the bugs themselves on this beamline.
Meera: So that’s an example of work currently taking place, but what else can be done here? What is next coming up in terms of environmental science?
Fred: One of the projects I’m just starting to get involved in is a big consortium between several Universities, mainly in the North of England, Sheffield, Manchester and Leeds, which is a project looking at what may happen in thousands of years to nuclear waste if it is put into repositories which are buried deep within the earth. The idea of a nuclear repository is that you encase the nuclear waste in steel and then in concrete and that barrier will be intact for several thousand years, but some of the radionucleides that you are encasing have half lives in the thousands of years, so they’ll still be a substantial amount of radionucleides that are active and potentially harmful that are extent when the barriers have begun to break down.
Meera: That’s quite a way in the future to have to predict?
Fred: Yes, therefore you need as much basic information on the chemistry of the radionucleides in these environments so that you start accurate starting parameters to achieve what you hope is an accurate end result.
Meera: So as well as trying to solve current problems, such as arsenic contamination, Diamond’s beamlines can also be used in research predicting or preventing contamination, thousands of years into the future. That was Fred Mosslemans, Principal Beamline Scientist on Diamond’s microfocus spectroscopy beamline.
Meera: Now staying on the topic of contaminated land sites and spreading wider into the topic of land as a whole, Sam Shaw and Lianne Benning from the University of Leeds have been using Diamond’s beamlines to find out how inorganic materials, such as rust, and the organic processes of microbes, such as fungi, impact on our soils and could be used to benefit our environment.
Sam Shaw: Well my area of research is really understanding processes which occur in the environment on the nano and molecular scale and understanding how they can influence processes on a regional, or even global, scale. This is, for example, understanding the formation of minerals, soils and how that can be applied to contaminated land problems, or understanding formation of minerals or biological interaction of minerals in the marine environment, which has implications for the ocean chemistry, or even CO2 in the atmosphere relating to climate change etc.
Meera: Liane, looking down on this small scale, how important would you say it is and how bigger scale can the information you find out be on?
Liane: Well we know that many of the interactions which happen at the atomic or molecular scale drive actually the reactions of the other scale, but we do not understand the fundamental principles of interaction between, for example, bacteria, fungi, minerals and fluids which drive these reactions. For example, if a living organism attaches itself to a mineral it will affect how that mineral dissolves or changes, but we do not understand how that happens. And for that we use synchrotron radiation techniques, a variety of techniques to try to understand really that interface which drives a reaction and the product of that reaction can affect things like climate.
Meera: Sam, your particular area of research within all this is green rust. Most people know what rust is, but what is green rust?
Sam: Green rust is very similar to rust. It’s an iron oxide phase, but green rust gets its name simply from its colour, but it has a slightly different chemistry from normal rust. It contains both Fe2 and Fe3, the two different oxidation states of iron and that’s what gives it its green colour. Fe2 produces blue compounds, Fe3 is yellow and if you mix them together you get green rust. But the special properties of green rust are that it is able to immobilise particular contaminants by changing their chemical state and thereby reducing their impact on the environment and potentially be applied to remediate contaminated land sites.
Meera: What particular contaminants can it immobilise and where do you actually find green rust?
Sam: Well in terms of the contaminants, there’s a wide range of inorganic contaminants from Chromium, which is a particular problem across the world. There was an industrial legacy of Chromium smelting in Europe and America which has left a lot of chromium waste. Also radionucleides like uranium, technetium, which are potentially hazardous, for example leaking from a nuclear waste repository, but also organic contaminants, for example trichloroethylene which is a widely distributed contaminant. In terms of where you get it in nature, it is extremely rare. Because it contains this FE2 component, it’s very sensitive to air oxidation it’s very difficult to find. So when I actually say it’s rare, it’s very difficult to find it because it’s difficult to characterise because as soon as you dig it up, you might dig in the soil and find some green patches but they quickly turn brown, and this is one of the challenges of studying this phase because it’s very air sensitive that to actually study it, we have to mimic the conditions where it occurs in very low oxygen levels and that is what we’ve been doing on the synchrotron.
Meera: So how do you set about recreating these conditions and then looking at the reactions of green rust here at the synchrotron?
Sam: Well what we’ve done is developed a reaction cell which can mimic the conditions of green rust formation in, say, a soil or potentially in a contaminated land site. To mimic the pH, the acidity or the alkaline nature of the solution and also the redox potential, so how oxidising or how reducing the environment is, so that’s really controlled by how much oxygen is present in the system. By doing this, we can synthesise and form the green rust, but also by flowing the solution, where we’re forming the green rust, through the synchrotron beam, through a capillary which is mounted on the synchrotron beam, we can characterise the formation reaction and the process by which the molecular structure of green rust is built.
Meera: So what is the structure of green rust and what have you been able to see about how it actually immobilises various contaminants?
Sam: Well we’ve been using x-ray scattering to characterise the formation of the structure and what we’ve found is by using in-situ wide and small angle scattering x-ray on I22 here at Diamond, the formation reaction is a multi stage process where we get initial formation of poorly ordered, fairly amorphous nano-particles, and then the Fe2 absorbs onto their surface and this induces a re-crystallisation reaction which forms the green rust. We’ve also been adding contaminants, particularly uranium and selenium, to look at when these contaminants become immobilised during the formation process
Meera: So knowing this information, how could these contaminants be treated or immobilised? It seems green rust can only exist in very limited conditions, so given that, how is it then possible to create it to then decontaminate land?
Sam: That’s a very good question and what we’ve learned using the synchrotron, is that we’ve really understood the geo-chemical conditions in which green rust is stable and from this we’ve been able to develop key formulations and recipes of green rust which we’re beginning to use to immobilise particular contaminants. But it’s true, the sensitive nature of the rust is a problem and we have gone some way to stabilising the green rust, but the future work we’re doing will be to develop a more stable form with wider applications for the green rust materials.
Meera: Great, thanks Sam. Now, staying on minerals, but now the association of bugs, bacteria, fungi, with minerals and that’s what you look into Leanne?
Sam: Yes. What Sam has talked about is how we have developed techniques to make minerals, to follow their formation, but in the transformation of rocks, for example, into soils, in our environment, has for many years been believed to be a purely inorganic process. That means it’s just rocks reacting with water. But in the last couple of decades, we have realised that the presence of bacteria and specifically more recently the presence of fungi, are key players in the breaking of minerals i.e. the weathering process. Now if you think of weathering, yes it is a global scale, and if you have mountains which rise, weathering increases, there is more link to CO2 and climate. That means that fungi and bacteria can affect how global cycles can actually occur. But we do not understand how they actually break a mineral, or how they help break a mineral, and what the molecular fundamental processes are in that process, in that reaction.
Meera: And which particular bacteria do fungi do you look into and how do you actually look into them?
Liane: Well the work I’ve done specifically at Diamond, but previously at the Daresbury Synchrotron, was using infrared spectroscopy because infrared spectroscopy has an area called the mid infrared which is called the fingerprint region which is extremely good for detecting changes in organic molecules. So we are using bacteria in my previous work and at the moment we are working primarily on fungi, to understand how the biochemical nature of a fungal strain which is growing over a mineral changes, and how that affects the bottom, the reaction with the interface and how the mineral changes with the actions of this fungi growing over them. By using the beamline B22 here, which is a new infrared beamline, we try to map out, on a very small scale, you have to remember that these fungi are about 5 microns in diameter. Now 5 microns is very, very, very small! But they can be hundreds of microns long. As they grow over a surface, they change their chemistry, because they have to be active at the tip and the tip is chemically very different than the end of the fungi. So as they change their chemistry, they affect the substrate which they grow over and they destroy it.
Meera: and so what do they do at these various stages along them?
Liane: As a fungi grows over a surface, the first thing it does is attaches itself to the surface. Now the mineral we’ve been looking at is a mineral which is a sheet silicate, so it’s very flat but has many, many layers, and by attaching to the surface, they actually bend it and we call that the biomechanical force. So they actually disrupt the layers within the mineral and by doing that they allow chemistry to take place. And the reason they grow over this mineral is because they are interested in food and this mineral has one particular element which is potassium, which is a key nutrient for this fungi. If I grew those over a quartz crystal, they wouldn’t care. They need food, so they grow for nutrients and that’s the reason that they break this mineral because they want to extract the potassium which is their food.
Meera: so they are there with a purpose?
Liane: They have a purpose and we have seen things where we actually put little wells where we have quartz and a mineral which has potassium or a mineral which has phosphorous which is another key nutrient and they literally just jump. They go aerial, they fly over it, they go to where the food is.
Meera: So what results from the chemical reactions taking place there then?
Liane: Well, what we’ve seen is that the weathering of these fungi is obviously a progressive stage, but we have not quantified the rates of weathering by fungi in comparison to the rates of weathering by a purely inorganic system. In certain conditions it’s orders of magnitude faster, so they break the rock much more efficiently because they are after the potassium, they are hungry.
Meera: So knowing this about them, what can be done using or understanding this?
Liane: Well, you have to realise that the reason we started doing this is because as humankind, we actually consume more soil than we produce worldwide and eventually, the world will run out of soil to make food. We do not understand how our soils are formed and the important thing in this as well is that every single plant, well 80% of the world’s plants, have fungi associated with their roots. Think about 1 kilogram of soil having up to 200 kilometres of fungal networks in it.
Meera: That’s quite a lot!
Liane: So these are rough numbers, but it gives you an idea that this is a big biomass and it’s a lot of surfaces that they can interact with. So they can break down rocks very, very fast. But now we are starting to understand how at this interface, between the fungi and the rocks, the processes occur and therefore actually understand how it happens in nature.
Meera: Sam Shaw and Liane Benning from the University of Leeds showing how understanding the science of rust and fungi on the nano-scale can help our environment on the global scale.
Did you know that Diamond’s Storage ring is made up of 456 magnets, 48 dipoles, 168 quadrupoles and 240 sextapoles and that’s not including the insertion devices!
Meera: You’re listening to the Diamond Light Source Podcast and this month we’re finding out new ways to clean up and power our environment. Still to come, we discover a new form of solar cell made using plastics that could make this source of power more accessible and resourceful. But before that, let’s join Sarah Bucknall from Diamond’s Communication Team for a round up of the latest news and events from Diamond.
Sarah Bucknall: We had the Annual Synchrotron Users Meeting at the beginning of September which went really well. There was variety of satellite sessions which covered a number of the different areas which Diamond benefits, such as Chemical Processes, Infrared Microprobes, surface and Interface Structure, so lots of interesting discussions taking place. And the meeting coincided with the release of our 2010 Annual Report which features a selection of key research undertaken at Diamond over the past year.
Meera: So as well as this though, you’ve just had a busy summer period leading up to this meeting anyway and the Users have too with various public engagement events that you’ve had taking place, including of course the Royal Society which is where we recorded from last time.
Sarah Bucknall: Yes, summer’s been a very busy time at Diamond. We’ve had a number of meetings and workshops, plus the Royal Society Summer Science Exhibition which was an extremely successful event. We’ve found out that almost 50,000 people visited the exhibition over the 10 days .
Meera: That’s an incredible number of visitors. I imagine that Diamond would have had a lot of exposure through that.
Well, we were certainly kept very busy! Every day we had streams of people coming up to us, to the stand asking questions about the machine and also about the applications that it can be used for. You can still look at some of the science that we were talking about on a special website which is www.insidediamond.org
Meera: That sounds like an exciting time in terms of getting Diamond’s message and science out there, but another way that Diamond’s gone about getting people aware of what’s taking place is a Diffraction Pattern, or the World’s Largest one. Tell me more about this and is it ready now?
Sarah: So this is a Science and Arts project that began about a year and a half ago. It’s actually the World’s largest diffraction pattern and it was finally unveiled in July this year by Professor Venki Ramakrishnan, who was the 2009 winner of the Nobel Prize for Chemistry. It’s actually a piece of textile art made up of thousands of cross stitches and they were gathered far and wide over the past 18 months from as far as Chicago to Paris and then also closer to home.
Meera: Have you seen the finished product yourself? What does it look like, what do you think?
Sarah: It’s quite stunning to look at. It’s clearly inspired by a scientific image. It‘s actually based on a diffraction pattern and the resulting 3D structure of a protein called Serine Racemase. This was an important biological target in the fight against pain and neurodegenerative disorders such as Alzheimer's disease and one of Diamond’s Industrial Users, the Pharmaceutical Company Evotec, used Diamond to solve the structure of Serine Racemase. So you can clearly see that influence in the piece and as you get closer you can notice the thousands of individual cross stitches and you get an idea just how many people have contributed to it.
Meera: So it’s quite impressive by the sounds of it, I’d quite like to see it. I mean it’s been taken around the world for stitches to be added to it, where can people go along to see it, is it just at diamond?
Sarah: Well at the moment it’s on display inside the Synchrotron building at Diamond, so if people come to one of our Open days you can see it there. There are also plenty of photos on our website to see its journey along the way. You can see that the former Science Minister added a stitch, along with a number of British Ambassadors. Eventually we hope to be able to tour it potentially around the county.
Meera: Brilliant, well I look forward to seeing it, but if I do make it down to Diamond as well you had a new Beamline opening?
Sarah: Earlier this year B18 became Diamond’s 18th Beamline to go into operation. It’s the Core EXAFS Beamline and it adds to our Spectroscopy Suite. It offers X-ray Absorption Spectroscopy which is an established technique providing essential element specific information about the local atomic geometry and the chemical state of the absorbing atom.
Meera: What kinds of science will be taking place there?
Sarah: Really diverse subjects such as Platinum Fuel Cells, Mineral Formation in the Earth’s Crust, to Catalysis, Corrosion, Framework Molecule and Nanoparticles.
Meera: Lots going on really for the Users, for the Public, for you yourself at diamond. Lots to look at, lots of research taking place. What about the future, what’s coming up?
Sarah: Well we’ve got a number of events coming up towards the end of the year. We’ll be welcoming a number of A-Level students in November during our special ‘Schools Inside Diamond Day’, as well as an event called Engineering Your Future. This is a day of workshops which demonstrate the variety of engineering jobs that are out there, so students can come along to learn about the Jet fusion facility which is nearby, engineering jobs in the RAF and the kind of work that’s carried out in the Space Department at the Rutherford Appleton Laboratory next door. And then for the public, we’ve got our next Inside Diamond Day on Saturday 13th November. Registration will be opening soon and more details can be found on our website.
Meera: And just to reiterate then, what’s the web address where people can go to register for it?
they can go straight to our home page and link from there. It’s www.diamond.ac.uk
Meera: Thanks Sarah. Sarah Bucknall from Diamond’s Communication Team, who’ll be back in the next edition with more news from Diamond. Now moving back to the science taking place at Diamond, more specifically how the science there is hoping to benefit our environment, we now discover a new form of solar cell that uses plastic instead of silicone. David Lidzey from the University of Sheffield explains more.
David Lidzey: The materials that we are interested in are very special plastics so they have been synthesized for us by synthetic chemists here at Sheffield. They’ve got 2 really important properties; firstly they absorb light over a broad range of wavelengths, so where you might see a film of polythene which essentially is largely transparent, the materials that we have can absorb light all the way from green wavelengths right the way through to the near infrared and of course if you want to harvest sunlight energy, you want to pick up as much of the sunlight as possible. So that’s one property which is important, the second property is that they are electrical semi-conductors, so basically once you’ve put a charged carrier, a electron for example, in these materials, then that will flow through the material if you apply a field to it. So, the photovoltaics are made from these thin films of semiconductors and essentially we have our plastic which is mixed with another material which is called a Fullerene .Now Fullerene is basically carbon-60, so this is a molecule which was discovered 20 years ago or so. It’s one of the pure forms of carbon.
Meera: So how would this actually work? I assume it’s reasonably new, you’re always looking to use plastic and people haven’t up to now, so what are the challenges really faced with using this as a material?
David: Well there are a number of challenges. One is extending the red absorption wave length, so we want to go further and further into the infrared, and the second challenge is actually getting these charges out of the thin films. So basically you have this Fullerene molecule and when the polymer is excited by the absorption of a photon, an electron jumps from the polymer molecule to the Fullerene molecule and this act of what’s called ‘charge transfer’ essentially creates a tiny current inside the device. When that happens over millions and millions of molecules, we can extract enough of a current out of the device because of this charge transfer process. The thing is though, when we take our polymer and we mix it with this fullerene molecule, the polymer and the fullerene phase separate so, of course you’ve seen a salad dressing made by the mixture of oil and vinegar and of course the oil and vinegar separate, when we mix the polymer and the fullerene together, they’ll also phase separate. Now this is beneficial for us because we want to create parts of the film which are polymer-rich and other parts of the film which are fullerene-rich, and these almost create little charge-transfer wire inside the material. If they actually phase separate on too large a length scale, then this makes the device not work very efficiently. If it phase separates on a very fine length scale then they also don’t work very efficiently because you can’t form these little charge-transfer pathways. So essentially one of the tricks is to actually know how to get the film to phase separate on exactly the right length scale and this is one of the things that we’ve been very interested in. And we’ve been using the Diamond Light Source and other techniques to actually study the structure of the film.
Meera: What has this enabled you to see then in detail about the process?
David: Now what we find is that for most of the time when this solution is drying, actually nothing much happens at all and this, I guess, is a sort of watching the paint dry phase. But when the solvent evaporates to leave only about 50% of the film containing solvent, things actually suddenly get very exciting. And what happens is we see a very rapid crystallization of the polymer. This process happens in about 5-10 seconds and suddenly we see that the solvent, as the polymer molecules start to crystallize, it’s very difficult for the solvent to leave the film. The kinetics of the crystallization of the polymer tells us that the crystals first form around impurities, or little aggregates, that exist within the film and we see a crystallization that happens essentially in one dimension. So we see a one-dimensional crystallization of the polymer. And thirdly, we actually find that as the polymer crystallizes, we can actually see that the crystallization and the arrangement of the molecules in the crystallites improves, basically their packing gets tighter and tighter, there’s a general reduction in kinks and twists in the molecules. So it’s really the whole picture, the way that the solvent evaporates, the dynamics of the crystallization, and the improved packing of the molecules tells us, gives us an overall picture, of the processes that occur as the film dries.
Meera: So having been able to see this, what stage would you say your research is at the moment? Have you got a final design that you would want to go into production to have plastic incorporated into our solar cells?
David: Well at the moment the sort of solar cells that we are producing at Sheffield and obviously other groups are producing them around the world, have efficiency between say 4 and 8%. So this means that between 4 and 8% of the suns energy that falls onto the solar cell, or is absorbed by the solar cell, is actually converted into electrical power. Now silicone, our big rival as it were, has an efficiency of between 15 and 20%, so you can see that we’re actually quite far behind than silicone really. So one of the big challenges now is to actually improve the efficiency of the organic based system up towards the efficiencies of the inorganic based systems. It is possible that we will never actually get to the efficiencies that you get with the inorganic, but the big advantage of using polymers is that they are very, very cheap to produce and they are very, very cheap to make thin films from.
Meera: So although it may not match the efficiency of silicone, the fact that it’s cheaper will hopefully mean that more places and more people will be using it.
David: Well exactly, and so the idea is that if you could produce these things on a plastic substrate that essentially you could go down to you local DIY Supermarket and buy a big roll of this stuff and just pin it to your side of your house and produce your electricity very, very cheaply. And really there’s a huge amount of land area which is essentially redundant in parts of the country, so the rues of out of town supermarkets or the sidings of railways or motorways, you don’t actually want to do very much with them and if you could actually cover these at very, very low cost with a very thin, flexible photovoltaic film, you could actually produce a huge amount of electricity.
David Lidzey from the University of Sheffield. Now that is it for this edition of the Diamond Light Podcast, but make sure to join us again in November for more insight into the science taking place at Diamond. In the meantime though, if you have any questions about the research or science taking place at Diamond, the email address is email@example.com
, you can also listen to previous editions of this program online at www.diamond.ac.uk/podcast
. you can also subscribe to the Diamond podcast on iTunes. Thank you this month to Fred Mosselmans, Sam Shaw, Liane Benning, Sarah Bucknall and David Lidzey. I’m Meera Senthilingam , thank you for listening and I’ll see you next time.
The Diamond podcast is brought to you by Diamond Light source and produced by the Nakedscientists.com. There’s more information on our website at www.diamond.ac.uk/podcast