Nanotech is Finally Here – feature for Science Uncovered

Hi all! If you follow me on Twitter, you may have noticed that I’ve mentioned Science Uncovered a few times lately…. the reason is, I have had an article published as the main cover story on the May issue that fantastic magazine! Cue me talking pictures of the magazine in-situ everywhere – Waterloo, Heathrow Airport, Ireland…. tragic I know, but it is very exciting! There were a few edits / additions to the final published piece that made me a little bit twitchy (typical physicist), but I’m just going to let it go and enjoy it :)

Anyway, you can find the magazine in all good newsagents, or you can download it from the official site (see link above). For my loyal readers, I’ve included a excerpt from the magazine below. I should say though that this is my original (unedited) text, which looks VERY dull without the cool images.

Screen Shot 2014-04-16 at 10.53.40 AM

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Nanotech is Finally Here – an excerpt!

  • Nano-medicine

What’s in your medicine cabinet? Ibuprofen and paracetamol? How about bottles of nanoparticles that can target specific infections and cells in your body… No? Well, that future is much closer than you might think. Engineered nanoparticles will change medicine, and how we diagnose and treat diseases.

Five years ago, gold nanoparticles coated with a polymer were found to penetrate a human cell without causing any damage to it. In 2013, a group from MIT expanded this work and showed that lots of different nanoparticles could be used – it was all do with the coating. Just one molecule thick, the coating is a mixture of hydrophobic (water-repellent) and hydrophilic (water-attracting) components. Cells tend to engulf things in contact with their surface, but this specific combination of chemicals in the coating actually fuses with the lipids (fats and vitamins) in the cell wall, and so, causes no damage. The size of the nanoparticle is also important – it can only pass harmlessly through the cell wall if its diameter falls below the critical size (~ 10 nm). Anything too large will damage the cell. But with the right coating and size, a nanoparticle can pass through the membrane, and once it has, the opening reseals itself. This means that nanoparticles coated in a drug could be inserted into infected cells – direct-to-cell drug delivery, which could be used to treat range of diseases. And at the end of 2013, another MIT group developed nanoparticles coated in insulin that could be delivered orally and absorbed through digestion. This would allow patients to simply take a pill instead of receiving injections.

Nanoparticles can also be used in cancer treatment. One option is to inject a cancer cell with gold nanoparticles. Because gold is an excellent x-ray absorber, if you bombard the cell with x-rays, and, it will heat up and effectively ‘cook’ the cell. A similar technique, using magnetic (iron) nanoparticles and an alternating magnetic field to destroy tumours is also in the animal-trial stage. If successful, the use of nanoparticles in cancer treatment would allow doctors to move away from whole-body treatments, such as chemotherapy, instead focussing on individual cancer cells, destroying them rapidly, but with minimal damage to adjacent healthy tissue. Researchers hope that human trials could begin within a decade.

  • Nano-solar cells

Solar cells have gradually entered the domestic market in the last decade, and can be seen on rooftops everywhere, but did you know that typically, they convert less than a fifth of the Sun’s available energy into electricity? Thankfully, recent breakthroughs in nanotechnology are changing the domestic solar cell game.

One of the issues with today’s solar cells is that they are reflective. And any sunlight reflected from the cell cannot be absorbed and converted into electricity. What’s needed is a non-reflective material, a sort of “solar sponge” that can absorb as much light (at different wavelengths) as possible. Ideally, you want this material to also be electrically conductive enough to allow electric charges flow through the cell. Enter III-V semiconductor nanowires – long, thin wires of specific materials (e.g. gallium arsenide, GaAs) that can be easy grown over large areas, like a nanoscale forest!  A team from the Australian National University discovered that because the wires are so tightly packed, any light reflected from one will be absorbed by another, and so, most of the light hitting the nanowire forest will be absorbed.

A thin layer of nanowires added to the surface of a domestic solar cell hugely improves its efficiency, and solar cells made with core-shell nanowires (which contain a combination of III-V materials), take this improvement even further by optimising how electric charges flow through the cell. Early results on these solar cells show efficiencies approaching that of the best domestic ones on the market, but using only a fraction of the amount of material, so at a reduced cost.

… So now you’ve had a little preview – I hope you enjoyed it! If you’d like to read the rest of the feature, please head to your nearest newsagents or download the issue through iTunes or Google Play via http://www.science-uncovered.com/ - there are some fantastic articles in this month’s issue, so you’re in for a treat :)

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Exciting (if surreal) News

Hi everyone!

Firstly, forgive me. I know I have been completely useless of late. I’ve been going through some sad times, which I’m not going to talk about. But I thought I should tell you guys about some VERY EXCITING news.

I HAVE A BOOK DEAL!!!!!!!!!!

Yep, it still feels weird writing that. Totally surreal. But it is all true. Just over a month ago, I found out that my proposal for a popular science book has been approved! And if all goes well, it’ll be published in October 2016.

And I owe all of this to my blog and to Twitter. The lovely Jim Martin from Bloomsbury (yep, the HUGE publisher!!) found my blog via Twitter, and emailed me. He has launched a brand-new popular science imprint with Bloomsbury, called Sigma Science and was on the hunt for authors. After many many emails, some brain storming and a rather delicious lunch, I came up with the idea for a book on the science behind our cities.

I wrote a proposal and a draft chapter and off Jim went to various meetings and commissioning boards. And on 17th February 2014, I heard that my proposal had been accepted!!! So, I’m writing a book, like a real one, which you’ll all eventually be able to buy in a book shop. Mad stuff altogether.

I should be signing the contract next week and have set up Twitter and FB accounts that I’m hoping to use to build some interest in the book as I’m writing it, and to collect your thoughts! As a start, do you have any questions about the science / technology hidden in our cities?

Anyway, here is the book’s  title

SCIENCE AND THE CITY: Urban Technology and the Megacity Future

Do you like??

Just the small matter of writing the whole book now ;)

 

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Nanoscale Shape-Memory Oxide

Another story for Materials Today…

A team from Berkeley Lab have demonstrated a nanoscale shape-memory effect in an oxide that surpasses the best performance measured in any metal to date.

Move over shape-memory alloys, there is a new material in town – the shape-memory oxide – and its performance surpasses any shape-memory effect ever measured in a metal. Shape-memory alloys have been used in everything from medicine to the automotive industry since the 1960s because of their unusual property – they “remember” their original form. If the alloy is deformed by stress, it can return to its original shape just by being heated, and can do so repeatedly over time.

But there are some limitations – the best alloys can endure a maximum strain of just 8%, the thermal recovery process can be slow, and as the size of the alloys shrink toward the nanoscale, they become unstable due to oxidation and fatigue-led micro-cracking. To investigate nanoscale shape-memory effects, a team at Berkeley Lab moved away from alloys and instead focussed on bismuth ferrite (BFO), a multiferroic oxide comprised of bismuth, iron and oxygen. Their results on the oxide, published in the November 2013 issue of Nature Communications, open the door for a new generation of small-scale devices. Led by Ramamoorthy Ramesh, the team firstly developed a crystal growth routine that could produce a material with high mismatch strain. Then, by reducing its lateral stress, they deformed the BFO and analysed changes in the crystal structure under a scanning probe and in-situ transmission electron microscope. They found that bismuth ferrite could withstand strains of up to 14%, surpassing the previous highest value for an alloy of just 8%.

In addition, because of its multiferroic nature, Ramesh and his team found that an elastic-like phase transition could be induced in the bismuth ferrite using only an electric field – a much faster recovery route than thermal-mediation as used in alloys. This is the first time such a large shape-memory effect has been measured in an oxide, and its implications may be profound for small-scale systems. Although this material has yet to be used in a working device, it has been shown to be fully compatible with silicon, so could be used in existing microelectromechanical systems (MEMS). And with further characterisation and development, BFO may play a leading role in the development of the next generation of nanoelectromechanical systems and other state-of-the-art nanodevices.

Nature Communications (2013) doi:10.1038/ncomms3768

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Exfoliating 2-D Materials for Printable Electronics

This story appeared in the Feb issue of Materials Today, but you can read it for free below

Chemists at the National University of Singapore have developed a new chemical exfoliation technique that could herald a step-change in printable electronics.

The field of flexible and printable electronics continues to develop at a rapid pace, with the use of two-dimensional transition metal dichalcogenides attracting particular attention in recent literature. But there has been a bottleneck in their development – current processes for producing high-quality monolayers of a range of chalcogenides are slow, complex and produce very low yields.

But, it seems that a team from Singapore and Korea has smashed that bottleneck, using a new exfoliation method to produce the largest single sheets of molybdenum disulphide yet reported in the literature. The method, published in the January issue of Nature Communications, also applies to other two-dimensional chalcogenides, such as tungsten diselenide and titanium disulfide, and results in high yield exfoliation for all of these materials.

Transition metal dichalcogenides (TMDs) have been heralded as the next generation of 2D materials due to their unique electronic and optoelectronic properties, and their high thermal and mechanical stability. Unlike graphene, TMDs are semiconductors and so, have a bandgap that could be used in a range of nanoscale transistors and optoelectronic devices. This work, led by Loh Kian Ping, is the first to report on a chemical exfoliation route that can produce the large area, high-quality monolayers of TMDs that are needed to make a practical device. The team used a comparative approach, using the metal adducts of naphthalene (compounds of lithium, sodium and potassium) as the basis for their process. Using a two-step expansion and intercalation method, Kian Ping and his team produced single-layer molybdenum disulphide sheets, 400 μm2 in size, greatly surpassing the “sub-micrometre” size more typical of 2D chalcogenides.

The paper also demonstrated that the exfoliated sheets can be made into a printable solution, with the high viscosity of the sheets rendering them highly suitable for inkjet printing. Recent work from that team at the National University of Singapore has focused on making their TMD sheets more suitable for use industrial processing methods, including the development of TMD-inks and the characterisation of their non-linear optical properties. It is hoped that the development of this high-yield process will help to make the next-generation of large area thin film technologies a reality. Potential applications for these materials include flexible logic circuits, photodetectors and solar cells.

Nature Communications (2013) doi:10.1038/ncomms3995

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Nano-Recycling?

Another news piece that appeared in the November 2013 issue of Materials Today. I was very impressed by this paper (reference at the end) so hope that the news piece does it justice!

Turning Plastic Bags into Carbon Nanotubes

The University of Adelaide have developed a process for transforming waste plastic bags into well-organised carbon nanotube membranes.

We all try to reuse and recycle the plastic bags we get from supermarkets, but some Australian researchers have gone one high-tech step further – a team from the University of Adelaide have used these non-degradable bags to produce carbon nanotubes (CNTs), and they hope that this discovery will help develop the next generation of advanced filtration materials.

Most current approaches to CNT synthesis rely on expensive carbon precursors such as methane, and iron- or cobalt-based catalysts. But this work, published in Carbon, is based on a catalyst- and solvent-free chemical vapour deposition (CVD) approach for producing CNT-alumina membranes, using commercially available supermarket plastic bags as the carbon source.

The Adelaide team, led by Prof. Dusan Losic, was driven by the need to find a method of cheaply producing large quantities of high-quality CNTs. And by using a waste material as the source of carbon, they may also have found a way to recycle the countless plastic bags thrown away every year. In their system, small squares (1 cm2) of linear low-density polyethylene (LLDPE) bags are thermally decomposed. Under an inert atmosphere, the carbon from the LLDPE is deposited in the form of CNTs within templates of nanoporous anodic alumina membranes (NAAMs).

NAAMs feature hexagonally arranged nanopores that cut through the membrane, allowing the team to control the geometry and orientation of the CNTs, without the need for a catalyst. The surface chemistry of the CNTs could also be controlled by further functionalization stages. The team showed that these CNTs membranes (CNT-NAAMs) could be precisely engineered to recognise particular molecules, and so, could be used as low-dimensional high-efficiency filters in separation applications (e.g. desalination of water). These membranes could also be recycled by thermal cleaning and/or sonication.

The individual CNTs produced by this technique were multi-walled, could be reputably produced, and compared favourably with those synthesised by other methods. And unlike traditional catalyst-based CVD techniques, the geometry of the CNTs produced by Losic and his team could be tightly controlled.

Producing carbon nanotube membranes in this way offers a scalable way to synthesise CNTs, while reducing the use of poisonous compounds, and may lead to a new breed of filtration materials. Nanotechnological recycling of your shopping bags may be only a few years away.

Carbon (2013) doi:10.1016/j.carbon.2013.07.003

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Carbon Nanotube Computer Becomes Reality

This is a piece I wrote for Materials Today. It originally appeared in the November 2013 issue but can be read here for free :)

A team from Stanford have built the world’s first functioning computer based on carbon nanotube (CNT) transistors.

The need for smaller electronic devices has driven the semiconductor industry towards the miniaturization of components, and has brought about reduced costs and major improvements in computational power and energy efficiency. But for silicon-based components, smaller, cheaper, faster also means hotter – as components shrink, and more transistors packed on each chip, the power density increases, and they generate more heat.

Digital circuits based on semiconducting carbon nanotube (CNT) transistors have the potential to outperform silicon by improving the energy–delay product, a metric of energy efficiency used in logic systems, by more than an order of magnitude. It is almost 15 years since carbon nanotubes were first used to produce transistors, where CNTs replaced silicon as the channel material within a MOSFET. But in a major development published in Nature, a team from Stanford has built a fully-functioning computer, built entirely from these CNT-based transistors.

With Cedric, as the system has been dubbed, Stanford have overcome the inherent difficulties in using CNTs that have limited their practical use as transistors. In their two-pronged attack, the researchers removed any metallic CNTs and accounted for any misalignment of the tubes. By biasing the gate, and pulsing a large current through the system, the semiconducting CNTs are retained while Joule heating causes the metallic CNTs to vaporise. The team also developed an algorithm and fabrication technique to identify and isolate those misaligned CNTs that would cause logic fail.

The CNT computer is capable of multitasking – running a basic operating system that can switch between counting and number sorting. And their system can also run MIPS – a commercial instruction set developed in the 1980s. Cedric is a Turing Complete, meaning that it could be used to solve any computational problem. It consists of 178 CNT transistors, meaning that it operates on one bit of data, and can count to 32. But this limit is not a physical one; it is due to the scale of the university chip fabrication facilities. Their design is compatible with current industry processes, so can be scaled up.

This paper demonstrates the promise of CNTs for use in complex computing systems. The team are confident that although large-scale development may be years away, Cedric offers a major breakthrough in low-power nanoscale computing, and may herald the end of silicon.

Nature (2013) doi:10.1038/nature12502

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Active Galactic Nuclei

See! I promised science and here it is :) Over the Christmas break, I spent some time going through old hard-drives etc, and I came across my BSc thesis from Trinity College Dublin. So I thought I’d share it with you :) It is more than a little cringe-worthy (and I thought it was SO GOOD when I did it) but it might be of interest to at least a few of you, so you’ll find it here in PDF format: LW_Astrophys_TCD

At optical wavelengths, the emission from most galaxies is dominated by that from the stars. However in at least 10% of galaxies (called active galaxies), additional intense emission is also detected from the centre (nucleus) of the galaxy. This emission often far out-shines that from the surrounding stars (often by factors >102).

It turns out that Active Galactic Nuclei (AGN) are the most luminous, long-lived sources in the universe. They emit strongly over the entire observable wavelength range, from x-rays and γ- rays through to radio. The most powerful examples can radiate a thousand times as much energy as the galaxies in which they are embedded. Many AGN vary in brightness by substantial amounts over timescales as short as years, months, days, or even hours.

I looked at several of these active sources using data from three telescopes – the Hubble, the Tytler (an optical telescope actually called the Lick Observatory in San Jose) and the International Ultraviolet Explorer. I found that there was a large scatter in the data from each scope (unsurprising really!) and investigated the potential for using AGN as “standard candles

Anyway, enjoy! and please let me know if you have any questions :)

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