Northwestern University's International Institute for Nanotechnology (IIN) announced that chemist Joseph M. DeSimone of the University of North Carolina at Chapel Hill is the recipient of the inaugural $250,000 Kabiller Prize in Nanoscience and Nanomedicine. The Kabiller Prize and the $10,000 Kabiller Young Investigator Award in Nanoscience and Nanomedicine were established by the IIN earlier this year through a generous donation from Northwestern trustee and alumnus David G. Kabiller. Recipients are selected by an international committee of experts in the field. Kabiller Prize recipients Joseph DeSimone (third from left) and Warren Chan (far right) were honored by Northwestern's International Institute for Nanotechnology (IIN) at a private dinner Sept. 29. Also pictured are Northwestern trustee and alumnus David G. Kabiller (far left), whose gift established the prizes; Dr. Eric Neilson (second from left), vice president for medical affairs and Lewis Landsberg Dean at Northwestern University Feinberg School of Medicine; and Chad Mirkin (second from right), IIN director and the George B. Rathmann Professor of Chemistry. "These awards were established not only to recognize the people who are designing the technologies that will drive innovation in nanomedicine, but also to educate and shine a light on the great promises of nanomedicine," said Kabiller, co-founder of AQR Capital Management, a global investment management firm in Greenwich, Connecticut. The Kabiller Prize is among the largest monetary awards in the U.S. for outstanding achievement in the field of nanotechnology and its application to medicine and biology. "The world needs more people like David Kabiller," said Chad A. Mirkin, IIN director and the George B. Rathmann Professor of Chemistry in Northwestern's Weinberg College of Arts and Sciences. "He is dedicated to making a difference and to improving the world through advances in science." DeSimone's innovative research applying nanotechnology to medicine captures the vision of the Kabiller Prize. "Joe is a Renaissance scientist, who has made some of the most important advances in the field of nanomedicine," Mirkin said. One of those advances is PRINT (Particle Replication in Non-wetting Templates) technology, invented by DeSimone in 2005. The technology enables the fabrication of precisely defined, shape-specific nanoparticles for advances in disease treatment and prevention. Nanoparticles made with PRINT technology are being used to develop new cancer treatments, inhalable therapeutics for treating pulmonary diseases, such as cystic fibrosis and asthma, and next-generation vaccines for malaria, pneumonia and dengue. "I'm thrilled and humbled to be recognized with the inaugural Kabiller Prize by such a world-class institution as Northwestern's International Institute for Nanotechnology," DeSimone said. "The PRINT technology invented in my laboratory continues to be developed for many different applications to improve human health, and my students are leading that charge. This recognition is really a testament to their brilliant efforts." DeSimone is the Chancellor's Eminent Professor of Chemistry at the University of North Carolina at Chapel Hill (UNC-Chapel Hill). He also is the William R. Kenan Jr. Distinguished Professor of Chemical Engineering at North Carolina State University and of chemistry at UNC-Chapel Hill. DeSimone founded a startup company based on PRINT called Liquidia Technologies that is building on the promise of vaccine clinical trial results. The company already has spun out two more companies to use PRINT to improve human health, one in ophthalmology and one in oral health. "The invention of PRINT technology and its application toward improvements in human health will shape the field of nanomedicine for decades to come and improve the quality of life for many," said Dr. Eric Neilson, vice president for medical affairs and Lewis Landsberg Dean at Northwestern University Feinberg School of Medicine. The International Institute for Nanotechnology also announced that Warren Chan, a professor at the Institute of Biomaterials and Biomedical Engineering at the University of Toronto, is the recipient of the inaugural Kabiller Young Investigator Award. The award recognizes young researchers who have made a recent groundbreaking discovery with the potential to make a lasting impact in the same arena. Chan and his research group have developed an infectious disease diagnostic device for point-of-care use that can differentiate symptoms. A diagnosis occurs when a patient pricks his or her finger, the sample is amplified, and a disease is detected using a smartphone app. (More than one disease can be detected.) Results for patients infected with HIV and hepatitis B are available in less than one hour at 90 percent accuracy, and the diagnostic device costs less than $100. The device currently is being commercialized and could change the way diseases are diagnosed and tracked globally. "I am very honored to receive the Kabiller Young Investigator Award in Nanoscience and Nanomedicine, and I hope this recognition helps to inspire other young people in the field of nanotechnology," Chan said. DeSimone and Chan were celebrated at a private dinner last night in Chicago. The two will be publicly recognized and present their research Oct. 1 at the 2015 IIN Symposium, which will include talks from other prestigious speakers, including 2014 Nobel Prize in Chemistry winner William E. Moerner.
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Nano News
Brilliant colors from environmentally friendly quantum dots
Quantum dots have made it possible to substantially increase color quality in LCD displays. However, these cadmium-based nanocrystals have proven to be harmful to the environment. Fraunhofer researchers are working together with an industry partner to develop a promising alternative: quantum dots based on indium phosphide. Quantum dots make it possible to display any color in full brilliance. (Image: Fraunhofer IAP) The landscape is breathtaking. Because it is so real, you forget for a moment that the eagle circling the sky is not outside your window, but is instead on your television. Such deceptively realistic images are not only a result of the high resolution displays available on modern devices; the colors play a role as well, and they are becoming ever brighter and richer. This is possible thanks to tiny crystals known as quantum dots (QDs), which have a thickness of merely a few atoms. These nanoparticles located in the backlight units of QD LCD displays offer a cornucopia of colors, but also they possess another extraordinary characteristic. “One big advantage of quantum dots is that their optical properties can be selectively modified by changing their size,” explains Dr. Armin Wedel of the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam, Germany. “This means you no longer have to manufacture three separate materials for the colors red, green and blue; now it is possible to do the job with just one.” This saves both time and money. Over the last several years, Fraunhofer IAP researchers in Potsdam have been developing quantum dots for customers in a wide range of industry sectors. They manufacture the nanoparticles using chemical synthesis and customize them for each application. This initially results in very small particles that radiate blue light. At sizes above approximately 2 nanometers, the color changes to green. The largest of the quantum particles, at 7 nanometers in size, emit within the red spectral range. Currently, Wedel and his team are developing quantum dots for display backlighting on behalf of Dutch company NDF Special Light Products B.V. These quantum dots will improve the color rendering and color realism of the displays. Here, the crystals are manufactured for the different emission colors and embedded in plastics. These plastics are subsequently processed into films and built into the display as a conversion film. Alternative materials based on indium phosphide With this task, researchers are facing a new challenge. The EU Commission is currently considering a ban on cadmium in consumer goods by 2017, because of its damaging effect on the environment. However, it is also considered to be the ideal material for manufacturing the crystals – cadmium-based quantum dots can achieve a narrowband spectrum sharpness of just 20 to 25 nanometers. Display manufacturers around the world are now looking for suitable replacement materials with similar characteristics. Against this backdrop, Fraunhofer IAP looks to be on a promising path. “We are testing quantum dots based on indium phosphide together with NDF Special Light Products,” says Wedel. His team has already managed to achieve a spectral sharpness of 40 nanometers. At first glance, that does not seem too far away from the quality achievable with cadmium-based quantum dots, but the differences in color fidelity are still present. “We see this as a good first milestone, but we are still striving for further improvement,” says Wedel. This effort is set to pay off, as television manufacturers are not the only ones who covet these little color wonders. There is also great market potential for special applications such as medical or aeronautical equipment displays. Furthermore, quantum dots can also increase the efficiency of solar cells, or can be employed in bioanalytics. For such special cases, the optical characteristics of the quantum dots must be precisely configured to the specific application requirements. “We’re in a good position thanks to our extensive experience in manufacturing quantum dots to meet specific customer requirements,” says Wedel.
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Phoenix effect: Resurrected proteins double their natural activity
Proteins play a large role in sustaining life functions. These molecules ensure that vital reactions, such as DNA replication or metabolism catalysis, are carried out within cells. When proteins die, the so-called process of denaturation takes place, which is accompanied by the unfolding of the native three-dimensional structure of the protein and hence the loss of its activity. By reassembling this polymer tangle back, it is possible to renature the protein and restore its activity, but this procedure requires much effort. Denatured proteins often pile up to form toxic aggregates, which is the underlying reason for many illnesses such as Alzheimer, Parkinson and Huntington. Therefore the investigation of denaturation and renaturation mechanisms cannot be overestimated. In a new study ("Enzyme renaturation to higher activity driven by the sol-gel transition: Carbonic anhydrase"), David Avnir, professor at the Hebrew University in Jerusalem, and Vladimir Vinogradov, head of the International Laboratory of Solution Chemistry of Advanced Materials and Technologies at ITMO University, found that bringing proteins back to life is not only possible, but can be carried out with an improvement over their original activity. This strange phenomenon owes to a new technique of protein renaturation based on combining thermally denatured proteins (carbonic anhydrase) with a colloid solution of inorganic aluminum oxide nanoparticles. As the solution turns into a gel, the nanoparticles start binding together, exerting mechanical pressure on the protein molecules. As a result, each molecule ends up entrapped in its own individual porous shell, which prevents the malign process of protein aggregation and eventually restores their original spatial structure. Having compared the level of activity of proteins before denaturation and after renaturation, the chemists discovered that the resurrected ones were 180 percent more active than their native predecessors. "Every protein molecule has its active center, which allows the molecule to interact with the environment. The active center, however, constitutes only 5 - 10 percent of the molecule surface," explains Vladimir Vinogradov. "During renaturation we deal with a long unfolded molecule containing an active center and several extending tails. The active center and nanoparticles have similar charges and will repel, while the tails have an opposite charge and will gravitate towards the nanoparticles. In the end, when a shell forms around the molecule, the active center will be as far away from the wall of the shell as possible. Instead, the active center will be directed right into the pore in the shell, thus increasing the protein's chances to interact with the substrate." Researchers say that this technique only works with unfolded denatured proteins. The orientation of native proteins within the shell cannot be controlled in the same way, because the active center can find itself anywhere, including facing the wall, which entirely excludes the possibility of interacting with the substrate. As professor David Avnir explains, one possible application of the discovery could help optimize the fabrication of drugs based on active proteins: "Some of the most effective drugs are based on active proteins that are harvested from cell cultures. However, from all proteins grown in such a way only 20 percent are native and suitable for use, while the remaining 80 percent are the so-called inclusion bodies, that is, non-functioning denatured proteins. Obviously, knowing how to convert denatured proteins to their native state, and on top of it with increased level activity, would allow pharmaceutical companies to lower the price of many drugs making them more affordable."
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New research puts us closer to do-it-yourself spray-on solar cell technology
In a 2014 study, published in the journal ("Fully solution processed all inorganic nanocrystal solar cells"), St. Mary's College of Maryland energy expert Professor Troy Townsend introduced the first fully solution-processed all-inorganic photovoltaic technology. While progress on organic thin-film photovoltaics is rapidly growing, inorganic devices still hold the record for highest efficiencies which is in part due to their broad spectral absorption and excellent electronic properties. Considering the recorded higher efficiencies and lower cost per watt compared to organic devices, combined with the enhanced thermal and photo stability of bulk-scale inorganic materials, Townsend, in his 2014 study, focused on an all-inorganic based structure for fabrication of a top to bottom fully solution-based solar cell. A spray-on nanocrystal solar cell array. (Image courtesy of St. Mary's College of Maryland) A major disadvantage compared to organics, however, is that inorganic materials are difficult to deposit from solution. To overcome this, Townsend synthesized materials on the nanoscale. Inorganic nanocrystals encased in an organic ligand shell are soluble in organic solvents and can be deposited from solution (i.e., spin-, dip-, spray-coat) whereas traditional inorganic materials require a high temperature vacuum chamber. The solar devices are fabricated from nanoscale particle inks of the light absorbing layers, cadmium telluride/cadmium selenide, and metallic inks above and below. This way, the entire electronic device can be built on non-conductive glass substrates using equipment you can find in your kitchen. The outstanding challenge facing the (3-5 nm) inorganic nanocrystals is that they must be annealed or heated to form larger 'bulk scale' grains (100 nm to 1 µm) in order to produce working devices. Townsend recently teamed with Navy researchers to explore this process. "When you spray on these nanocrystals, you have to heat them to make them work," explained Townsend, "but you can't just heat the crystals by themselves, you have to add a sintering agent and that, for the last 40 years, has been cadmium chloride, a toxic salt used in commercial thin-film devices. No one has tested non-toxic alternatives for nanoscale ink devices, and we wanted to explore the mechanism of the sintering process to be able to implement safer salts." In his latest study, published this year in the ("Safer salts for CdTe nanocrystal solution processed solar cells: the dual roles of ligand exchange and grain growth"), Townsend, along with Navy researchers, found that ammonium chloride is a non-toxic, inexpensive viable alternative to cadmium chloride for nanocrystal solar cells. This discovery came after testing several different salts. Devices made using ammonium chloride (which is commonly used in bread making) had comparable device characteristics to those made with cadmium chloride, and the move away from cadmium salt treatments alleviates concerns about the environmental health and safety of current processing methods. The team also discovered that the role of the salt treatment involves crucial ligand removal reactions. This is unique to inorganic nanocrystals and is not observed for bulk-scale vacuum deposition methods. "A lot of exciting work has been done on nanocrystal ligand exchange, but, for the first time, we elucidated the dual role of the salt as a ligand exchange agent and a simultaneous sintering agent. This is an important distinction for these devices, because nanocrystals are typically synthesized with a native organic ligand shell. This shell needs to be removed before heating in order to improve the electronic properties of the film," said Townsend about the discovery. Because nanomaterials are at the forefront of emerging new properties compared to their bulk counterpart, the study is important to the future of electronic device fabrication. The research comes in the wake of the Obama Administration's announcement in July to put more solar panels on low-income housing and expand access to solar power for renters, and recent pledge to get 20 percent of the U.S. total electricity from renewable sources by the year 2030. "Right now, solar technology is somewhat unattainable for the average person," said Townsend. "The dream is to make the assembly and installation process so cheap and simple that you can go to your local home improvement store and buy a kit and then spray it on your own roof. That is why we we're working on spray-on solar cells." Townsend plans for further research to increase the efficiency of the all-inorganic nanocrystal solar cells (currently reaching five percent), while building them with completely non-toxic components.
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New electrode gives micro-supercapacitor macro storage capacity
Micro-supercapacitors are a promising alternative to micro-batteries because of their high power and long lifetime. They have been in development for about a decade but until now they have stored considerably less energy than micro-batteries, which has limited their application. Now researchers in the Laboratoire d’analyse et d’architecture des systèmes (LAAS-CNRS)1 in Toulouse and the INRS2 in Quebec have developed an electrode material that means electrochemical capacitors produce results similar to batteries, yet retain their particular advantages. This work was published on September 30, 2015 in ("3D RuO2 Microsupercapacitors with Remarkable Areal Energy"). Image obtained from scanning tunneling microscopy on a porous 3D-gold structure. (Image: Anaïs Ferris – LAAS) With the development of on-board electronic systems3 and wireless technologies, the miniaturization of energy storage devices has become necessary. Micro-batteries are very widespread and store a large quantity of energy due to their chemical properties. However, they are affected by temperature variations and suffer from low electric power and limited lifetime (often around a few hundred charge/discharge cycles). By contrast, micro-supercapacitors have high power and theoretically infinite lifetime, but only store a low amount of energy. Micro-supercapacitors have been the subject of an increasing amount of research over the last ten years, but no concrete applications have come from it. Their lower energy density, i.e. the amount of energy that they can store in a given volume or surface area, has meant that they were not able to power sensors or microelectronic components. Researchers in the Intégration de systèmes de gestion de l’énergie team at LAAS-CNRS, in collaboration with the INRS of Quebec, have succeeded in removing this limitation by combining the best of micro-supercapacitors and micro-batteries. They have developed an electrode material whose energy density exceeds all the systems available to date. The electrode is made of an extremely porous gold structure into which ruthenium oxide has been inserted. It is synthesized using an electrochemical process. These expensive materials can be used here because the components are tiny: of the order of square millimeters. This electrode was used to make a micro-supercapacitor with energy density 0.5 J/cm2, which is about 1000 times greater than existing micro-supercapacitors, and very similar to the density characteristics of current Li-ion micro-batteries. With this new energy density, their long lifetime, high power and tolerance to temperature variations, these micro-supercapacitors could finally be used in wearable, intelligent, on-board microsystems. Notes 1 LAAS is part of the Instituts Carnot. Members of this renowned network conduct upstream research that refreshes their scientific and technological skills, and promote a deliberate joint research policy to benefit enterprise partners. 2 Institut national de la recherche scientifique. 3 On-board systems are wearable electronic systems. They must often meet size and consumption constraints.
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Invisibility cloak might enhance efficiency of solar cells
Success of the energy turnaround will depend decisively on the extended use of renewable energy sources. However, their efficiency partly is much smaller than that of conventional energy sources. The efficiency of commercially available photovoltaic cells, for instance, is about 20%. Scientists of Karlsruhe Institute of Technology (KIT) have now published an unconventional approach to increasing the efficiency of the panels. Optical invisibility cloaks guide sunlight around objects that cast a shadow on the solar panel, such as contacts for current extraction ("Cloaked contact grids on solar cells by coordinate transformations: designs and prototypes"). A special invisibility cloak (right) guides sunlight past the contacts for current removal to the active surface area of the solar cell. (Image: Martin Schumann, KIT) Energy efficiency of solar panels has to be improved significantly not only for the energy turnaround, but also for enhancing economic efficiency. Modules that are presently mounted on roofs convert just one fifth of the light into electricity, which means that about 80% of the solar energy are lost. The reasons of these high losses are manifold. Up to one tenth of the surface area of solar cells, for instance, is covered by so-called contact fingers that extract the current generated. At the locations of these contact fingers, light cannot reach the active area of the solar cell and efficiency of the cell decreases. “Our model experiments have shown that the cloak layer makes the contact fingers nearly completely invisible,” doctoral student Martin Schumann of the KIT Institute of Applied Physics says, who conducted the experiments and simulations. Physicists of KIT around project head Carsten Rockstuhl, together with partners from Aachen, Freiburg, Halle, Jena, and Jülich, modified the optical invisibility cloak designed at KIT for guiding the incident light around the contact fingers of the solar cell. Normally, invisibility cloak research is aimed at making objects invisible. For this purpose, light is guided around the object to be hidden. This research project did not focus on hiding the contact fingers visually, but on the deflected light that reaches the active surface area of the solar cell thanks to the invisibility cloak and, hence, can be used. To achieve the cloaking effect, the scientists pursued two approaches. Both are based on applying a polymer coating onto the solar cell. This coating has to possess exactly calculated optical properties, i.e. an index of refraction that depends on the location or a special surface shape. The second concept is particularly promising, as it can potentially be integrated into mass production of solar cells at low costs. The surface of the cloak layer is grooved along the contact fingers. In this way, incident light is refracted away from the contact fingers and finally reaches the active surface area of the solar cell (see Figure). By means of a model experiment and detailed simulations, the researchers demonstrated that both concepts are suited for hiding the contact fingers. In the next step, it is planned to apply the cloaking layer onto a solar cell in order to determine the efficiency increase. The physicists are optimistic that efficiency will be improved by the cloak under real conditions: “When applying such a coating onto a real solar cell, optical losses via the contact fingers are supposed to be reduced and efficiency is assumed to be increased by up to 10%,” Martin Schumann says.
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New processes in modern ReRAM memory cells decoded
Resistive memory cells or ReRAMs for short are deemed to be the new super information-storage solution of the future. At present, two basic concepts are being pursued, which, up to now, were associated with different types of active ions. But this is not quite correct, as Jülich researchers working together with their Korean, Japanese and American colleagues were surprised to discover. In valence change memory (VCM) cells, not only are negatively charged oxygen ions active, but – akin to electrochemical metallization memory (ECM) cells – so too are positively charged metal ions. The effect enables switching characteristics to be modified as required and makes it possible to move back and forth from one concept to the other, as reported by the researchers in the journals ("Nanoscale cation motion in TaOx, HfOx and TiOx memristive systems") and ("Graphene-Modified Interface Controls Transition from VCM to ECM Switching Modes in Ta/TaOx Based Memristive Devices"). Formation of metallic Tantalum (Ta) filament within Ta/TaOx/Pt ReRAM memory cell. Positively charged Ta5+-ions and oxygen vacancies (VO) contribute to the process. (Image: Forschungszentrum Jülich / RWTH Aachen / Pössinger) ReRAM cells have a unique characteristic: their electrical resistance can be altered by applying an electric voltage. The cells behave like a magnetic material that can be magnetized and demagnetized again. In other words, they have an ON and an OFF state. This enables digital information to be stored, i.e. information that distinguishes between “1” and “0”. The most important advantages of ReRAMs are that they can be switched rapidly, consume little energy, and maintain their state even after long periods of time with no external voltage. The memristive behaviour of ReRAMs relay on mobile ions. These ions move in a similar manner to in a battery, flowing back and forth between two electrodes in a metal oxide layer no more than a few nanometres thick. For a long time, researchers believed that VCMs and ECMs functioned very differently. In ECMs, the ON and OFF states are achieved when metal ions move and form whisker-like filaments. This happens when an electric voltage is applied, causing such filaments to grow between the two electrodes of the cell. The cell is practically short-circuited and the resistance decreases abruptly. When the process is carefully controlled, information can be stored. The switching behaviour of VCMs, in contrast, were primarily associated with the displacement of oxygen ions. Contrary to metal ions, they are negatively charged. When a voltage is applied, the ions move out of an oxygen-containing metal compound. The material abruptly becomes more conductive. In this case as well, the process needs to be more carefully controlled. Jülich researchers working together with their partners from the Chonbuk National University, Jeonju, the National Institute for Materials Science in Tsukuba and the Massachusetts Institute of Technology (MIT) in Boston discovered an unexpected second switching process in VCMs: metal ions also help to form filaments in VCMs. The process was made visible because the scientists suppressed the movement of the oxygen ions. To do so, they modified the surface by applying a thin carbon layer directly at the interface of the electrode material with the solid electrolyte. In one case, they used the “miracle material” graphene, which comprises only one single layer of carbon. “Graphene was used to suppress the transport of oxygen ions through the phase boundary and to slow down the oxygen reactions. Suddenly, we observed a switching characteristic similar to that of an ECM cell and therefore assume that free metal ions are also active in VCMs. This was additionally verified using scanning tunnelling microscopy (STM) and diffusion experiments. It appears that the metal ions provide additional support for the switching process,” says Dr. Ilia Valov, electrochemist at Jülich’s Peter Grünberg Institute (PGI-7). A look into the Oxide Cluster at Forschungszentrum Jülich in which resistive cells and other layers of material are produced and examined in an ultrahigh vacuum. (Image: Forschungszentrum Jülich) Incorporating such a carbon interlayer would make it possible to jump from one switching process to the other in VCMs. This would lead to new options for designing ReRAMs. “Depending on the application, our findings could be exploited and the effect purposely enhanced or intentionally suppressed,” says Valov. The scientists’ findings give rise to several questions. “Existing models and studies will have to be reworked and adapted on the basis of these findings,” says the Jülich scientist. Further tests will clarify how such novel components behave in practice.
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