Category Archives: nanotechnology

Kevlar-wrapped batteries on an airplane

Researchers at the University of Michigan are not trying to bulletproof lithium-ion batteries with kevlar. Rather, they’re trying prevent fires. From a Jan. 27, 2015 University of Michigan news release (also on EurekAlert),

New battery technology from the University of Michigan should be able to prevent the kind of fires that grounded Boeing 787 Dreamliners in 2013.

The innovation is an advanced barrier between the electrodes in a lithium-ion battery.

Made with nanofibers extracted from Kevlar, the tough material in bulletproof vests, the barrier stifles the growth of metal tendrils that can become unwanted pathways for electrical current.

A U-M team of researchers also founded Ann Arbor-based Elegus Technologies to bring this research from the lab to market. Mass production is expected to begin in the fourth quarter 2016.

“Unlike other ultra strong materials such as carbon nanotubes, Kevlar is an insulator,” said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering. “This property is perfect for separators that need to prevent shorting between two electrodes.”

Lithium-ion batteries work by shuttling lithium ions from one electrode to the other. This creates a charge imbalance, and since electrons can’t go through the membrane between the electrodes, they go through a circuit instead and do something useful on the way.

But if the holes in the membrane are too big, the lithium atoms can build themselves into fern-like structures, called dendrites, which eventually poke through the membrane. If they reach the other electrode, the electrons have a path within the battery, shorting out the circuit. This is how the battery fires on the Boeing 787 are thought to have started.

“The fern shape is particularly difficult to stop because of its nanoscale tip,” said Siu On Tung, a graduate student in Kotov’s lab, as well as chief technology officer at Elegus. “It was very important that the fibers formed smaller pores than the tip size.”

While the widths of pores in other membranes are a few hundred nanometers, or a few hundred-thousandths of a centimeter, the pores in the membrane developed at U-M are 15-to-20 nanometers across. They are large enough to let individual lithium ions pass, but small enough to block the 20-to-50-nanometer tips of the fern-structures.

The researchers made the membrane by layering the fibers on top of each other in thin sheets. This method keeps the chain-like molecules in the plastic stretched out, which is important for good lithium-ion conductivity between the electrodes, Tung said.

“The special feature of this material is we can make it very thin, so we can get more energy into the same battery cell size, or we can shrink the cell size,” said Dan VanderLey, an engineer who helped found Elegus through U-M’s Master of Entrepreneurship program. “We’ve seen a lot of interest from people looking to make thinner products.”

Thirty companies have requested samples of the material.

Kevlar’s heat resistance could also lead to safer batteries as the membrane stands a better chance of surviving a fire than most membranes currently in use.

While the team is satisfied with the membrane’s ability to block the lithium dendrites, they are currently looking for ways to improve the flow of loose lithium ions so that batteries can charge and release their energy more quickly.

For anyone unfamiliar with the Boeing 787 Dreamliner fires, caused by lithium-ion batteries, these Boeing fires and others are mentioned in my May 29, 2013 post (Life-cycle assessment for electric vehicle lithium-ion batteries and nanotechnology is a risk analysis) scroll down about 50% of the way.

As for the research paper, here’s a link and a citation,

A dendrite-suppressing composite ion conductor from aramid nanofibres by Siu-On Tung, Szushen Ho, Ming Yang, Ruilin Zhang, & Nicholas A. Kotov. Nature Communications 6, Article number: 6152 doi:10.1038/ncomms7152 Published 27 January 2015

This paper is behind a paywall.

You can find out more about Elegus Technologies here.

A use for fullerenes—inside insulation plastic for high-voltage cables

A Jan. 27, 2015 news item on Nanowerk, describes research which suggests that there may a new use for buckminsterfullerenes (or what they’re calling ‘carbon nanoballs’),

Researchers at Chalmers University of Technology [Sweden] have discovered that the insulation plastic used in high-voltage cables can withstand a 26 per cent higher voltage if nanometer-sized carbon balls are added. This could result in enormous efficiency gains in the power grids of the future, which are needed to achieve a sustainable energy system.

The renewable energy sources of tomorrow will often be found far away from the end user. Wind turbines, for example, are most effective when placed out at sea. Solar energy will have the greatest impact on the European energy system if focus is on transport of solar power from North Africa and Southern Europe to Northern Europe.

“Reducing energy losses during electric power transmission is one of the most important factors for the energy systems of the future,” says Chalmers researcher Christian Müller. “The other two are development of renewable energy sources and technologies for energy storage.”

The Jan. 27, 2015 Chalmers University of Technology press release (also on EurekAlert) by Johanna Wilde, which originated the news item, provides more information about the research,

Together with colleagues from Chalmers and the company Borealis in Stenungsund, he [Müller] has found a powerful method for reducing energy losses in alternating current cables.  The results were recently published in Advanced Materials, a highly ranked scientific journal.

The researchers have shown that different variants of the C60 carbon ball, a nanomaterial in the fullerene molecular group, provide strong protection against breakdown of the insulation plastic used in high-voltage cables. Today the voltage in the cables has to be limited to prevent the insulation layer from getting damaged. The higher the voltage the more electrons can leak out into the insulation material, a process which leads to breakdown.

It is sufficient to add very small amounts of fullerene to the insulation plastic for it to withstand a voltage that is 26 per cent higher, without the material breaking down, than the voltage that plastic without the additive can withstand.

“Being able to increase the voltage to this extent would result in enormous efficiency gains in power transmission all over the world,” says Christian Müller. “A major issue in the industry is how transmission efficiency can be improved without making the power cables thicker, since they are already very heavy and difficult to handle.”

Using additives to protect the insulation plastic has been a known concept since the 1970s, but until now it has been unknown exactly what and how much to add. Consequently, additives are currently not used at all for the purpose, and the insulation material is manufactured with the highest possible degree of chemical purity.

In recent years, other researchers have experimented with fullerenes in the electrically conductive parts of high-voltage cables. Until now, though, it has been unknown that the substance can be beneficial for the insulation material.

The Chalmers researchers have now demonstrated that fullerenes are the best voltage stabilizers identified for insulation plastic thus far. This means they have a hitherto unsurpassed ability to capture electrons and thus protect other molecules from being destroyed by the electrons.

To arrive at these findings, the researchers tested a number of molecules that are also used within organic solar cell research at Chalmers. The molecules were tested using several different methods, and were added to pieces of insulation plastic used for high-voltage cables. The pieces of plastic were then subjected to an increasing electric field until they crackled. Fullerenes turned out to be the type of additive that most effectively protects the insulation plastic.

The press release includes some facts about buckyballs or buckminsterfullerenes or fullerenes or C60 or carbon nanoballs, depending on what you want to call them,

 Facts: Carbon ball C60

  • The C60 carbon ball is also called buckminsterfullerene. It consists of 60 carbon atoms that are placed so that the molecule resembles a nanometer-sized football. C60 is included in the fullerene molecular class.
  • Fullerenes were discovered in 1985, which resulted in the Nobel Prize in Chemistry in 1996. They have unique electronic qualities and have been regarded as very promising material for several applications. Thus far, however, there have been few industrial usage areas.
  • Fullerenes are one of the five forms of pure carbon that exist. The other four are graphite, graphene/carbon nanotubes, diamond and amorphous carbon, for example soot.

Here’s a link to and a citation for the research paper,

A New Application Area for Fullerenes: Voltage Stabilizers for Power Cable Insulation by Markus Jarvid, Anette Johansson, Renee Kroon, Jonas M. Bjuggren, Harald Wutzel, Villgot Englund, Stanislaw Gubanski, Mats R. Andersson, and Christian Müller. Advanced Materials DOI: 10.1002/adma.201404306 Article first published online: 12 DEC 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Here’s an image of wind turbines, an example of equipment which could benefit greatly from better insulation.,

Images: Lina Bertling, Jan-Olof Yxell, Carolina Eek Jaworski, Anette Johansson, Markus Jarvid, Christian Müller

Images: Lina Bertling, Jan-Olof Yxell, Carolina Eek Jaworski, Anette Johansson, Markus Jarvid, Christian Müller

You can find this image and others by clicking on the Chalmers University press release link (assuming the page hasn’t been moved). You can find more information about Borealis (the company Müller is working with) here.

SEMANTICS, a major graphene project based in Ireland

A Jan. 28, 2015 news item on Nanowerk profiles SEMANTICS, a major graphene project based in Ireland (Note: A link has been removed),

Graphene is the strongest, most impermeable and conductive material known to man. Graphene sheets are just one atom thick, but 200 times stronger than steel. The European Union is investing heavily in the exploitation of graphene’s unique properties through a number of research initiatives such as the SEMANTICS project running at Trinity College Dublin.

A Dec. 16, 2014 European Commission press release, which originated the news item, provides an overview of the graphene enterprise in Europe,

It is no surprise that graphene, a substance with better electrical and thermal conductivity, mechanical strength and optical purity than any other, is being heralded as the ‘wonder material’ of the 21stcentury, as plastics were in the 20thcentury.

Graphene could be used to create ultra-fast electronic transistors, foldable computer displays and light-emitting diodes. It could increase and improve the efficiency of batteries and solar cells, help strengthen aircraft wings and even revolutionise tissue engineering and drug delivery in the health sector.

It is this huge potential which has convinced the European Commission to commit €1 billion to the Future and Emerging Technologies (FET) Graphene Flagship project, the largest-ever research initiative funded in the history of the EU. It has a guaranteed €54 million in funding for the first two years with much more expected over the next decade.

Sustained funding for the full duration of the Graphene Flagship project comes from the EU’s Research Framework Programmes, principally from Horizon 2020 (2014-2020).

The aim of the Graphene Flagship project, likened in scale to NASA’s mission to put a man on the moon in the 1960s, or the Human Genome project in the 1990s, is to take graphene and related two-dimensional materials such as silicene (a single layer of silicon atoms) from a state of raw potential to a point where they can revolutionise multiple industries and create economic growth and new jobs in Europe.

The research effort will cover the entire value chain, from materials production to components and system integration. It will help to develop the strong position Europe already has in the field and provide an opportunity for European initiatives to lead in global efforts to fully exploit graphene’s miraculous properties.

Under the EU plan, 126 academics and industry groups from 17 countries will work on 15 individual but connected projects.

The press release then goes on to describe a new project, SEMANTICS,

… this is not the only support being provided by the EU for research into the phenomenal potential of graphene. The SEMANTICS research project, led by Professor Jonathan Coleman at Trinity College Dublin, is funded by the European Research Council (ERC) and has already achieved some promising results.

The ERC does not assign funding to particular challenges or objectives, but selects the best scientists with the best ideas on the sole criterion of excellence. By providing complementary types of funding, both to individual scientists to work on their own ideas, and to large-scale consortia to coordinate top-down programmes, the EU is helping to progress towards a better knowledge and exploitation of graphene.

“It is no overestimation to state that graphene is one of the most exciting materials of our lifetime,” Prof. Coleman says. “It has the potential to provide answers to the questions that have so far eluded us. Technology, energy and aviation companies worldwide are racing to discover the full potential of graphene. Our research will be an important element in helping to realise that potential.”

With the help of European Research Council (ERC) Starting and Proof of Concept Grants, Prof. Coleman and his team are researching methods for obtaining single-atom layers of graphene and other layered compounds through exfoliation (peeling off) from the multilayers, followed by deposition on a range of surfaces to prepare films displaying specific behaviour.

“We’re working towards making graphene and other single-atom layers available on an economically viable industrial scale, and making it cheaply,” Prof. Coleman continues.

“At CRANN [Centre for Research on Adaptive Nanostructures and Nanodevices at Trinity College Dublin], we are developing nanosheets of graphene and other single-atom materials which can be made in very large quantities,” he adds. “When you put these sheets in plastic, for example, you make the plastic stronger. Not only that – you can massively increase its electrical properties, you can improve its thermal properties and you can make it less permeable to gases. The applications for industry could be endless.”

Prof. Coleman admits that scientists are regularly taken aback by the potential of graphene. “We are continually amazed at what graphene and other single-atom layers can do,” he reveals. “Recently it has been discovered that, when added to glue, graphene can make it more adhesive. Who would have thought that? It’s becoming clear that graphene just makes things a whole lot better,” he concludes.

So far, the project has developed a practical method for producing two-dimensional nanosheets in large quantities. Crucially, these nanosheets are already being used for a range of applications, including the production of reinforced plastics and metals, building super-capacitors and batteries which store energy, making cheap light detectors, and enabling ultra-sensitive position and motion sensors. As the number of application grows, increased demand for these materials is anticipated. In response, the SEMANTICS team has scaled up the production process and is now producing 2D nanosheets at a rate more than 1000 times faster than was possible just a year ago.

I believe that new graphene production process is the ‘blender’ technique featured here in an April 23, 2014 post. There’s also a profile of the ‘blender’ project  in a Dec. 10, 2014 article by Ben Deighton for the European Commission’s Horizon magazine (Horizon 2020 is the European Union’s framework science funding programme). Deighton’s article hosts a video of Jonathan Coleman speaking about nanotechnology, blenders, and more on Dec. 1, 2014 at TEDxBrussels.

Nanowaste or the end of the life cycle for nanoscale materials

A Jan. 27, 2015 Nanwerk spotlight article on nanowaste presents a comprehensive picture of possible issues (Note: Footnotes have been removed),

Based on their special chemical and physical properties, synthetically produced nanomaterials (engineered nanomaterials, ENMs) are currently being used in a wide range of products and applications. The Nanomaterial Databank of Nanowerk … currently lists nanomaterials composed of 28 different elements as well as of carbon (fullerenes, CNT, graphene), quantum dots consisting of several semi-conductor materials, a large number of simple nanoparticulate compounds (oxides, carbonates, nitrides) and those made up of complex compounds containing several components. On the one hand, the application of nanomaterials promises reduction potentials and sustainability effects for the environment, for example through resource and material savings ….

On the other hand, we know very little about the behavior of nanomaterials or about environmental and health risks when these products enter various waste streams at the end of their life cycles. A better understanding of the risks in the so-called End-of-Life-Phase (EOL) calls for considering the different disposal pathways and potential transformation processes that nanomaterials undergo in waste treatment plants. In the disposal phase no consideration is being given to either the special properties of nanomaterials or to potential recovery and re-use. …

There is no special legal framework in place for a separate treatment of nanomaterial containing wastes … or the monitoring of the processes. A prerequisite for such a framework would be exact knowledge about the nanomaterials being used, their form (species) and composition, potential transformation processes as well as about amounts and concentrations. Such information, however, is not available, and virtually no studies have been conducted on the EOL phase of products containing nanomaterials. Very little is known about how nanomaterial-containing wastes behave in thermal, biological or mechanical-biological waste treatment plants or in landfills. …

The spotlight article appears to be a reprint of an ITA (Institute of Technology Assessment) NanoTrust Dossier [“Nanowaste” – Nanomaterial-containing products at the end of their life cycle (NanoTrust Dossier No. 040en – August 2014)] by Sabine Greßler, Florian Part, and André Gazsó,

Abstract:
Based on their special chemical and physical properties, synthetically produced nanomaterials are currently being used in a wide range of products and applications. At the end of their product life cycle, nanomaterials can enter waste treatment plants and landfills via diverse waste streams. Little, however, is known about how nanomaterials behave in the disposal phase and whether potential environmental or health risks arise. There are no specific legal requirements for a separate treatment of nanomaterial-containing wastes. Virtually no information is available about the nanomaterials currently in use, their form and composition, or about their amounts and concentrations. The current assumption is that stable nanoparticles (e.g. metal oxides) are neither chemically nor physically altered in waste incineration plants and that they accumulate especially in the residues (e.g. slag). These residues are ultimately dumped. The disposal problem in the case of stable nanoparticles is therefore merely shifted to the subsequent steps in the waste treatment process. Carbon nanotubes (CNT) are almost completely combusted in incineration plants. Filter systems seem to be only partially efficient, and a release of nanoparticles into the environment cannot be excluded. Incinerating nanomaterials contained in products can also promote the development of organic pollutants as undesired by-products. Only few studies are available on the behavior of nanomaterials in landfills. Moreover, recycling such products could release nanomaterials, most likely when these are shredded and crushed.

This dossier offers a good review of the current state of affairs with regard to nanowaste. I haven’t read it exhaustively but it coincides with my understanding of the situation including the fact that there’s not much research on the topic.

BTW, NanoTrust is a project of the Austrian Academy of Sciences’ Institute of Technology Assessment (ITA). The nanowaste dossier is also available in German.

Canadian nanoscientist, Federico Rosei, picks up a new honour (this one is from China)

I covered two of Federico Rosei’s awards last year in a Jan. 27, 2014 post about his Canadian Society for Chemistry award and in a Feb. 4, 2014 post about his E.W.R. Steacie Memorial Fellowship from Canada’s Natural Sciences and Engineering Research Council. This year, China has honoured the Dr. Rosei with a scholar’s award that requires regular visits to China. From a Jan. 28, 2015 news item on Azonano,

Professor Federico Rosei of the INRS Énergie Matériaux Télécommunications Research Centre has won the Chang Jiang Scholars Award, a highly prestigious distinction for world-class researchers given by the Chinese government. Professor Rosei was honoured for his work in the field of organic and inorganic nanomaterials. This is the first time the award has been given to an INRS faculty member. [INRS is Québec’s Institut national de la recherche scientifique; the Université de Québec’s research branch]

A Jan. 23, 2015 INRS news release by Gisèle Bolduc, which originated the news item, fills in some more details about the award and Dr. Rosei,

As a Chang Jiang scholar, Professor Rosei will make regular visits to the University of Electronic Science and Technology of China (UESTC) over the next three years, where he will help set up an R&D platform in nanomaterials and electronic and optoelectronic devices. In addition to these joint research projects, Professor Rosei will train young Chinese researchers, make scientific presentations, and forge international academic ties.

Federico Rosei’s tenure as a Chang Jiang scholar will complement and enhance his work as UNESCO Chair on Materials and Technologies for Energy Conversion, Saving and Storage (MATECSS). This INRS research chair is part of a North-South/South-South initiative to promote the international sharing of technical and scientific knowledge in the areas of renewable energies and sustainable development.

“Dr. Federico Rosei is an outstanding professor and researcher, and a true world leader in his field,” noted Yves Bégin, vice president (or principal) of research and academic affairs. “INRS is extremely proud to have Professor Rosei among its professors. Beyond his major scientific advances in his field, his presence in our institution helps build invaluable bridges between the local team of professors and large-scale international research projects.”

About the Chang Jiang Scholars Awards

Founded in 1998 by the Chinese Ministry of Education, the Chang Jiang Scholars program annually brings some 50 eminent international scholars, mainly in science and technology, to Chinese universities. The program’s aim is to raise standards of research in Chinese universities through collaboration with leading scientists from the world over.

About Federico Rosei

Professor Federico Rosei’s work in material physics has led to scientific innovations and practical applications in electronics, energy, and the life sciences. He is a Fellow of the Royal Society of Canada, distinguished lecturer at IEEE Nanotechnology Council (NTC), UNESCO Chair on Materials and Technologies for Energy Conversion, Saving and Storage (MATECSS), and recipient of the NSERC 2014 E.W.R. Steacie Memorial Fellowship from NSERC. Professor Rosei has won numerous awards including the 2014 José Vasconcelos World Award of Education from the World Cultural Council, the 2011 Friedrich Wilhelm Bessel award from the Alexander von Humboldt Foundation, the 2013 Herzberg Medal from the Canadian Association of Physicists, and the 2011 Rutherford Memorial Medal in Chemistry from the Royal Society of Canada. Dr. Rosei is a member of the European Academy of Sciences, a senior member of the Institute of Electrical and Electronics Engineers (IEEE) and the Society for Photo-Image Engineers (SPIE), and a Fellow of the American Physical Society; the U.S. Association for the Advancement of Science; the Engineering Institute of Canada; the Institute of Physics; the Royal Society of Chemistry; the Institute of Materials, Minerals and Mining; the Institute of Engineering and Technology; the Institute of Nanotechnology; and the Australian Institute of Physics.

Odd, there’s no mention of the Canadian Society for Chemistry award but since this man seems to be the recipient of many awards, I imagine some hard choices had to be made when writing him up.

For anyone who’d prefer to read about Rosei in French or would like to test their French reading skills, here’s Gisèle Bolduc’s 21 janvier 2015 actualité.

Silver nanowires have a surprising ability to self-heal

It seems there could be a new member of the flexible electronics materials community, silver nanowires, according to a Jan. 23, 2015 news item on ScienceDaily,

Wth its high electrical conductivity and optical transparency, indium tin oxide is one of the most widely used materials for touchscreens, plasma displays, and flexible electronics. But its rapidly escalating price has forced the electronics industry to search for other alternatives.

One potential and more cost-effective alternative is a film made with silver nanowires–wires so extremely thin that they are one-dimensional–embedded in flexible polymers. Like indium tin oxide, this material is transparent and conductive. But development has stalled because scientists lack a fundamental understanding of its mechanical properties.

A Jan. 23, 2015 Northwestern University news release (also on EurekAlert), which originated the news item, explains what makes silver nanowires a candidate as an alternative to indium tin oxide for use in flexible electronics,

… Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at Northwestern University’s McCormick School of Engineering, has led research that expands the understanding of silver nanowires’ behavior in electronics.

Espinosa and his team investigated the material’s cyclic loading, which is an important part of fatigue analysis because it shows how the material reacts to fluctuating loads of stress.

“Cyclic loading is an important material behavior that must be investigated for realizing the potential applications of using silver nanowires in electronics,” Espinosa said. “Knowledge of such behavior allows designers to understand how these conductive films fail and how to improve their durability.”

By varying the tension on silver nanowires thinner than 120 nanometers and monitoring their deformation with electron microscopy, the research team characterized the cyclic mechanical behavior. They found that permanent deformation was partially recoverable in the studied nanowires, meaning that some of the material’s defects actually self-healed and disappeared upon cyclic loading. These results indicate that silver nanowires could potentially withstand strong cyclic loads for long periods of time, which is a key attribute needed for flexible electronics.

“These silver nanowires show mechanical properties that are quite unexpected,” Espinosa said. “We had to develop new experimental techniques to be able to measure this novel material property.”

The findings were recently featured on the cover of the journal Nano Letters. Other Northwestern coauthors on the paper are Rodrigo Bernal, a recently graduated PhD student in Espinosa’s lab, and Jiaxing Huang, associate professor of materials science and engineering in McCormick.

“The next step is to understand how this recovery influences the behavior of these materials when they are flexed millions of times,” said Bernal, first author of the paper.

Here’s a link to and citation for the paper,

Intrinsic Bauschinger Effect and Recoverable Plasticity in Pentatwinned Silver Nanowires Tested in Tension by Rodrigo A. Bernal, Amin Aghaei, Sangjun Lee, Seunghwa Ryu, Kwonnam Sohn, Jiaxing Huang, Wei Cai, and Horacio Espinosa. Nano Lett., 2015, 15 (1), pp 139–146 DOI: 10.1021/nl503237t Publication Date (Web): October 3, 2014
Copyright © 2014 American Chemical Society

This particular version of the paper is behind a paywall. However, access to the paper is possible although I make no claims as to which version it is or whether it will continue to be freely accessible.

Opals, Diana Ross, and nanophotonic hybridization

It was a bit of a stretch to include Diana Ross in a Jan. 12, 2015 news item on Nanowerk about nanophotonic research at the University of Twente’s MESA+ Institute for Nano­technology  but I’m glad they did,

Ever since the early 1900s work of Niels Bohr and Hendrik Lorentz, it is known that atoms display characteristic resonant behavior to light. The hallmark of a resonance is its characteristic peak-trough behavior of the refractive index with optical frequency. Scientists from the Dutch MESA+ Institute for Nano­technology at the University of Twente have recently infiltrated cesium atoms in a self-assembled opal to create a hybrid nanophotonic system. By tuning the opal’s forbidden gap relative to the atomic resonance, dra­matic changes are observed in reflectivity. In the most extreme case, the atomic reflection spectrum is turned upside down[1] compared to the traditional case. Since dispersion is crucial in the control of optical signal pulses, the new results offer opportunities for optical information manipulation. As atoms are exquisite storage de­vices for light quanta, the results open vistas on quantum information processing, as well as on new nanoplasmonics.

A Jan. 12, 2015 MESA+ Institute for Nano­technology at the University of Twente press release, which originated the news item, provides an illustrative diagram and a wealth of technical detail about the research,

Courtesy of the University of Twente

Courtesy of the University of Twente

While the speed of light c is proverbial, it can readily be modified by sending light through a medium with a certain refractive index n. In the medium, the speed will be decreased by the index to c/n. In any material, the refractive index depends on the frequency of the light. Usually the refractive index increases with frequency, called normal dispersion as it prevails at most frequencies in most materials such as a glass of water, a telecom fiber, or an atomic vapor. Close to the resonance frequency of the material, the index strongly decreases, called anomalous dispersion.

Dispersion is essential to control how optical bits of information – encoded as short pulses – is manipulated optical circuits. In modern optics at the nanoscale, called nanophotonics, dispersion is controlled with classes of complex nanostruc­tures that cause novel behavior to emerge. An example is a photonic crystal fiber, which does not consist of only glass like a traditional fiber, but of an intricate arrange­ment of holes and glass nanostructures.

The Twente team led by Harding devised a hybrid system consisting of an atomic vapor infiltrated in an opal photonic crystal. Photonic crystals have attracted considerable attention for their ability to radically control propagation and emission of light. These nanostructures are well-known for their ability to control the emission and propagation of light. The opals have a periodic variation of the refractive index (see Figure 1) that ensures that a certain color of light is forbidden to exist inside the opal. The light cannot enter the opal as it is reflected, which is called a gap (see Figure 1). In an analogy to semiconductors, such an effect is called a “photonic band gap”. Photonic gaps are at the basis of tiny on-chip light sources and lasers, efficient solar cells, invisibility cloaks, and devices to process optical information.

The Twente team changed the index of refraction of the voids in a photonic crystal by substituting the air by a vapor of atoms with a strong resonance, as shown in Figure 1. The contrast of the refractive index between the vapor and the opal’s silica nano­spheres was effectively used as a probe. The density of the cesium vapor was greatly varied by changing the temperature in the cell up to 420 K. At the same time, the photonic gap of the opal shifted relative to the atomic resonance due to a slow chemical reaction between the opal’s backbone material (silica) and the cesium.

On resonance, light excites an atom to a higher state and subsequently the atom reemits the light. Hence, an atom behaves like a little cavity that stores light. Simultaneously the index of refraction changes strongly for colors near resonance. For slightly longer wavelengths the index of refraction is high, on resonance it is close to one, and slightly shorter wavelengths it can even decrease below one. This effect of the cesium atoms is clearly visible in the reflectivity spectra, shown in Figure 2 [not included here], as a sharp increase and decrease of the reflectivity near the atomic resonance. Intriguingly, the characteristic peak-and-trough behavior of atoms (seen at 370 K) was turned upside down at the highest temperature (420 K), where the ce­sium reso­nance was on the red side of the opal’s stopgap.

In nanophotonics, many efforts are currently being devoted to create arrays of nanoresonators in photonic crystals, for exquisite optical signal control on a chip. Unfortunately, however, there is a major challenge in engineering high-quality pho­tonic resonators: they are all different due to inevitable fabrication variations. Hence, it is difficult to tune every resonator in sync. “Our atoms in the opal may be consid­ered as the equivalent of an carefully engineered array of nano-resonators” explains Willem Vos, “Nature takes care that all resonators are all exactly the same. Our hy­brid system solves the variability problem and could perhaps be used to make pho­tonic memories, sensors or switches that are naturally tuned.” And leading Spanish theorist Javier Garcia de Abajo (ICFO) enthuses: “This is a fine and exciting piece of work, initiating the study of atomic resonances with photonic modes in a genuinely new fashion, and suggesting many exciting possibilities, for example through the extension of this study towards combinations with metal nanoplasmonics.”

Here’s a link to and a citation for the paper published in Physical Review B,

Nanophotonic hybridization of narrow atomic cesium resonances and photonic stop gaps of opaline nanostructures by Philip J. Harding, Pepijn W. H. Pinkse, Allard P. Mosk, and Willem L. Vos. Phys. Rev. B 91, 045123 – Published 20 January 2015 DOI: http://dx.doi.org/10.1103/PhysRevB.91.045123

This paper is behind a paywall but there is an earlier iteration of the paper available on the open access arXiv.org website operated by Cornell University,

Nanophotonic hybridization of narrow atomic cesium resonances and photonic stop gaps of opaline nanostructures by Philip J. Harding, Pepijn W.H. Pinkse, Allard P. Mosk, Willem L. Vos. (Submitted on 11 Sep 2014) arXiv:1409.3417

As I understand it, the arXiv.org website is intended to open up access to research and to offer an informal peer review process.

Finally, for anyone who’s nostalgic or perhaps has never heard Diana Ross sing ‘Upside Down’,

Islamic Educational Scientific and Cultural Organization (ISESCO) for Science and Technology and an award for Dr. Mahiran Basri

Professor Dr Mahiran Basri of the Universiti Putra Malaysia (UPM) received an award from the Islamic Educational Scientific and Cultural Organization (ISESCO) for Science and Technology (I believe the similarity of ISESCO to UNESCO is intentional, which makes it smart marketing) for her work in oil palm research. This event has occasioned a Jan. 21, 2015 news item on phys.org,

The use of oils and fats has been successfully diversified, resulting in an innovation formulated through nanotechnology that is beneficial to pharmaceutical and cosmetics industries.

A Faculty of Science, Universiti Putra Malaysia (UPM) lecturer, Professor Dr Mahiran Basri, not only succeeded in producing new useful substances made of oils and fats for the industry, but also managed to produce them through environmental-friendly ways.

A Jan. 22, 2015 UPM news release (Malaysia is on the other side of the date line) by Azaman Zakaria, which originated the news item, describes her work and award in more detail,

“This organic synthesis uses enzymes and it is produced through nanotechnology. Our focus is to process new substances derived from oils and fats,” she said in an interview at her office.

In the field of cosmetics, for instance, she said there are antioxidants and anti-aging substances, through the use of nanotechnology, those substances can easily absorb through the skin.

This way, they would be more effective, she added.

“What is also important is that the materials are clean and safe,” said the winner of the Islamic Educational Scientific and Cultural Organization (ISESCO) for Science and Technology 2014 award, which was held in Rabat, Morocco, in December.

The recognition was based on her active research and excellent performance in the field of chemistry including her far-reaching oil palm research that has contributed to the pharmaceutical and cosmetics industries.

The award was presented by the ISESCO Director General, Dr Abdulaziz Othman Altwaijri as Prof Mahiran took home a certificate, a medal and a cash prize of USD$5,000.

The biennial award has been organised by the Organisation of the Islamic Conference (OIC) since 1979 to foster and strengthen collaboration in the fields of science, education and culture among the OIC members.

According to Mahiran, efforts have been formulated to commercialise the innovation although it may take time.

“At this stage, we have obtained a pre-commercial project from Malaysian Technology Development Corporation (MTDC),” she said.

Professor Mahiran said in pharmaceuticals, an innovation has successfully produced a drugs delivery method to penetrate the ‘blood brain barrier’, especially for diseases that are associated with the brain, such as Alzheimer, Parkinson, epilepsy and meningitis.

“Drugs are normally hard to reach beyond the ‘blood brain barrier’. Thus we created drugs through nanotechnology, and that way we hope they are more effective,” she said.

She added, the innovation has been tested on animals and there were visible positive effects.

Meanwhile, in the agro-chemcial field, Professor Mahiran said, the formulation was made in a nano form to kill weeds and also perform as a cleaning agent to the environment, thus improve the development of the agricultural industry.

“The ingredients in the cosmetic, pharmaceutical and agro-chemical formulations are made through nanotechnology to produce the best for their efficacy, bio-availability in the products and ensure the safety of the consumers” she affirmed.

Professor Dr Mahiran has led 20 research projects in more than 3 decades since 1982, with provisions of grants worth more than RM7 million.

Her series of scientific research have also garnered her numerous awards including the prestigious Archer Daniels Midlands Award from the American Oil Chemists’ Society and the Ram Rais Biotechnology Award at the International Invention and Innovation Exhibition (ITEX) 2004 – UPM.

For anyone curious about ISESCO you can find the website here (with your pick of three languages). There’s also this description in its Wikipedia entry,

Islamic Educational, Scientific and Cultural Organization (ISESCO) was established by the Organisation of the Islamic Cooperation (OIC) in May 1979. ISESCO is one of the largest international Islamic organizations and specializes in the fields of education, science, and culture. Its headquarters are in Rabat, Morocco.

By the way, UNESCO (United Nations Organization for Education, Science and Culture) was founded in 1945.

A nanoparticle for a medical imaging machine that doesn’t exist yet

Researchers at the University of Buffalo (New York state) have created a nanoparticle that can be detected by six imaging devices according to a Jan. 20, 2015 news item on ScienceDaily,

It’s technology so advanced that the machine capable of using it doesn’t yet exist.

Using two biocompatible parts, University at Buffalo researchers and their colleagues have designed a nanoparticle that can be detected by six medical imaging techniques:

• computed tomography (CT) scanning;

• positron emission tomography (PET) scanning;

• photoacoustic imaging;

• fluorescence imaging;

• upconversion imaging; and

• Cerenkov luminescence imaging.

The advantages are obvious should somebody, somewhere create a hexamodal (aka, multimodal, aka hypmodal) sensing device capable of exploiting the advantages of this nanoparticle as the researchers hope.

A Jan. 20, 2015 University of Buffalo news release (also on EurekAlert) by Charlotte Hsu, which originated the news item, describes the ideas underlying the research,

This kind of “hypermodal” imaging — if it came to fruition — would give doctors a much clearer picture of patients’ organs and tissues than a single method alone could provide. It could help medical professionals diagnose disease and identify the boundaries of tumors.

“This nanoparticle may open the door for new ‘hypermodal’ imaging systems that allow a lot of new information to be obtained using just one contrast agent,” says researcher Jonathan Lovell, PhD, UB assistant professor of biomedical engineering. “Once such systems are developed, a patient could theoretically go in for one scan with one machine instead of multiple scans with multiple machines.”

When Lovell and colleagues used the nanoparticles to examine the lymph nodes of mice, they found that CT and PET scans provided the deepest tissue penetration, while the photoacoustic imaging showed blood vessel details that the first two techniques missed.

Differences like these mean doctors can get a much clearer picture of what’s happening inside the body by merging the results of multiple modalities.

A machine capable of performing all six imaging techniques at once has not yet been invented, to Lovell’s knowledge, but he and his coauthors hope that discoveries like theirs will spur development of such technology.

The news release also offers a description of the nanoparticles,

The researchers designed the nanoparticles from two components: An “upconversion” core that glows blue when struck by near-infrared light, and an outer fabric of porphyrin-phospholipids (PoP) that wraps around the core.

Each part has unique characteristics that make it ideal for certain types of imaging.

The core, initially designed for upconversion imaging, is made from sodium, ytterbium, fluorine, yttrium and thulium. The ytterbium is dense in electrons — a property that facilitates detection by CT scans.

The PoP wrapper has biophotonic qualities that make it a great match for fluorescence and photoacoustic imagining. The PoP layer also is adept at attracting copper, which is used in PET and Cerenkov luminescence imaging.

“Combining these two biocompatible components into a single nanoparticle could give tomorrow’s doctors a powerful, new tool for medical imaging,” says Prasad, also a SUNY Distinguished Professor of chemistry, physics, medicine and electrical engineering at UB. “More studies would have to be done to determine whether the nanoparticle is safe to use for such purposes, but it does not contain toxic metals such as cadmium that are known to pose potential risks and found in some other nanoparticles.”

“Another advantage of this core/shell imaging contrast agent is that it could enable biomedical imaging at multiple scales, from single-molecule to cell imaging, as well as from vascular and organ imaging to whole-body bioimaging,” Chen adds. “These broad, potential capabilities are due to a plurality of optical, photoacoustic and radionuclide imaging abilities that the agent possesses.”

Lovell says the next step in the research is to explore additional uses for the technology.

For example, it might be possible to attach a targeting molecule to the PoP surface that would enable cancer cells to take up the particles, something that photoacoustic and fluorescence imaging can detect due to the properties of the smart PoP coating. This would enable doctors to better see where tumors begin and end, Lovell says.

The researchers have provided two images,

This transmission electron microscopy image shows the nanoparticles, which consist of a core that glows blue when struck by near-infrared light, and an outer fabric of porphyrin-phospholipids (PoP) that wraps around the core. Credit: Jonathan Lovell

This transmission electron microscopy image shows the nanoparticles, which consist of a core that glows blue when struck by near-infrared light, and an outer fabric of porphyrin-phospholipids (PoP) that wraps around the core.
Credit: Jonathan Lovell

University at Buffalo researchers and colleagues have designed a nanoparticle detectable by six medical imaging techniques. This illustration depicts the particles as they are struck by beams of energy and emit signals that can be detected by the six methods: CT and PET scanning, along with photoacoustic, fluorescence, upconversion and Cerenkov luminescence imaging. Credit: Jonathan Lovell

University at Buffalo researchers and colleagues have designed a nanoparticle detectable by six medical imaging techniques. This illustration depicts the particles as they are struck by beams of energy and emit signals that can be detected by the six methods: CT and PET scanning, along with photoacoustic, fluorescence, upconversion and Cerenkov luminescence imaging.
Credit: Jonathan Lovell

Here’s a link to and a citation for the paper,

Hexamodal Imaging with Porphyrin-Phospholipid-Coated Upconversion Nanoparticles by James Rieffel, Feng Chen, Jeesu Kim, Guanying Chen, Wei Shao, Shuai Shao, Upendra Chitgupi, Reinier Hernandez, Stephen A. Graves, Robert J. Nickles, Paras N. Prasad, Chulhong Kim, Weibo Cai, and Jonathan F. Lovell. Advanced Materials DOI: 10.1002/adma.201404739 Article first published online: 14 JAN 2015

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