The Best Practice Guide is the final output of NanoSafePack, a 36 month project funded under the European Union’s Seventh Framework Programme (FP7). The development of the guide was informed by novel research activities undertaken as part of this project, as well as wider state-of-the-art knowledge in the field of nanosafety.
Primarily intended for use by SMEs and larger companies involved in the manufacture of polymer-based nanocomposites for packaging applications, the Best Practice Guide provides practical advice and recommendations which are easy to understand, use and apply in an industrial setting. This includes technical information concerning the specific applications and properties of nanofillers and polymer-based nanocomposites, as well as new scientific knowledge and guidance on environmental, health, and safety issues.
To accompany the full version of Best Practice Guide, a shorter Mini-Guide has also been developed, which is freely available in five languages: English, French, Spanish, Portuguese, and Italian. The Mini-Guide, available to download from the NanoSafePack website, provides an overview of:
- the main benefits of nanotechnology in the packaging industry;
- the structure and contents of the full version of the Best Practice Guide; and
- recommendations for the safe handling and use of nanofillers and polymer-based nanocomposites, demonstrated using a number of case studies.
Further information and contact details are provided within the Mini-Guide on how to obtain the full version of the Best Practice Guide. About the NanoSafePack project The research leading to the development of the best practice guide has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 286362 – NanoSafePack. The main aim of the NanoSafePack project was to develop a best practices guide to allow the safe handling and use of nanomaterials in packaging industries, considering integrated strategies to control the exposure to nanoparticles in industrial settings, and provide SMEs with scientific data to minimise and control nanoparticle release and migration from the polymer nanocomposites placed on the market. To achieve this aim, a complete hazard and exposure assessment was conducted to obtain new scientific data about the safety of polymer composites reinforced using nanometer-sized particles. An evaluation of the effectiveness of risk management measures was also undertaken in order to select and design practical and cost effective strategies for implementation in industrial settings. In addition, a life cycle assessment of nanocomposites was performed, by evaluating their impacts during the processes of manufacture, use and disposal. Results of these studies have been used in combination with state-of-the-art knowledge in the field of nanosafety to inform the development of this guide. The NanoSafePack Consortium consists of 7 European organisations, namely: Techni-Plasper, S.L.; Centro Español de Plásticos (CEP); Associação Portuguesa da Indústria de Plásticos (APIP); European Plastics Converters (EuPC); Instituto Tecnológico del Embalaje, Transporte y Logística (Itene); Institute of Occupational Medicine (IOM); and Tec Star s.r.l.
Atomic Force Microscopy (AFM) images show pinholes in the spiro-MeOTAD when it is first prepared (top) and after air exposure for 24 hours (bottom). The average diameter of the pinholes is about 135 nanometers, with some as large as two microns. OIST researchers believe they have identified a key culprit for this problem. Miniscule pinholes in the spiro-MeOTAD layer -- so small they cannot be seen even with a light microscope -- may be creating easy pathways for water and other gas molecules in air to diffuse through the thin film and degrade the perovskite. “These pinholes may play a major role in the degradation of the lifetime of the solar cells,” said Zafer Hawash, a PhD student at OIST who discovered the pinholes. His findings were recently published in the journal ("Air-Exposure Induced Dopant Redistribution and Energy Level Shifts in Spin-Coated Spiro-MeOTAD Films"). Hawash noticed the pinholes while analyzing how independent components of air, like water, oxygen and nitrogen, interact with spiro-MeOTAD. At first he didn’t think they were important, but when he started looking into it, he found no mention of them in the scientific literature. “No one has really mentioned this,” said Hawash, who works in OIST’sEnergy Materials and Surface Sciences Unit. “I started realizing it was something important to report, to let people know these pinholes exist and that we should get rid of them to get better lifetime.” The pinholes appear to be related to how the spiro-MeOTAD layer is usually made – a solution is spin-coated onto a base layer to create a thin film a fraction of the thickness of a human hair. Another preparation method, vacuum evaporation, does not produce the pinholes, but is less convenient to use, explained Dr. Luis Ono, an Energy Materials and Surface Sciences Unit group leader and paper co-author. The OIST team is looking into how they can eliminate the pinholes while still keeping the cost low, perhaps by tweaking preparation process or adding other ingredients. “Currently we are making efforts in finding a way to fix the problem of the pinholes,” said Professor Yabing Qi, who heads the Energy Materials and Surface Sciences Unit. This latest finding builds on the Qi’s lab ongoing work to overcome the instabilities in perovskite solar cells and develop low-cost solar power.
This is a 3-D model of IBN's rapid test kit that detects dengue-specific antibodies. (Image: IBN, A*STAR) IBN Executive Director Professor Jackie Y. Ying shared, "Our rapid diagnostic kit can detect a key dengue antibody from saliva that is present in early-stage secondary infection. The ability to differentiate between primary and secondary dengue infections makes it a valuable early diagnosis tool that would help to ensure timely treatment and proper care of patients." Patients with secondary infection, who have previously been infected with other serotypes of dengue virus, stand a higher risk of developing dengue hemorrhagic fever or dengue shock syndrome. According to Singapore's National Environment Agency, dengue fever and its more severe form, dengue hemorrhagic fever, are the most common mosquito-borne viral diseases in the world. This disease poses a serious health threat, and is a leading cause of illness and death in tropical and subtropical climates. There are four known serotypes of the dengue virus but no vaccine or medicine has been developed to treat the illness. The incubation period before symptoms develop generally ranges from 4 to 10 days after infection. Therefore, early diagnosis would enable the patient to receive prompt medical attention and avoid further complications. Currently, dengue infection is diagnosed in the laboratory by testing the patient's blood sample for the presence of dengue antigens or antibodies. IBN's device, on the other hand, is capable of detecting IgG, a dengue-specific antibody found at the onset of secondary infections, directly from saliva in one step. Unlike blood samples, saliva can be collected easily and painlessly for rapid point-of-care diagnostics. However, unlike other body fluids, it cannot be applied directly to commercially available test kits as it would cause the sensor nanoparticles to stick haphazardly to the test strip. In addition, conventional paper-based tests are not designed to handle the larger sample volume of saliva required. As described in the journal ("A stacking flow immunoassay for the detection of dengue-specific immunoglobulins in salivary fluid"), the IBN researchers used an innovative stacking flow design to overcome key challenges faced by existing lateral flow designs, such as those used in pregnancy test kits. In IBN's device, different flow paths are created for samples and reagents through a multiple stacked system. This allows the saliva sample to flow separately through a fiber glass matrix, which removes the substances that would interfere with the nanoparticle-based sensing system before it mixes with the sensor nanoparticles. IBN's device configuration also helps to regulate the flow in the test strip, generating uniform test lines for more accurate results. IBN's diagnostic kit can also be adapted to detect other infectious diseases such as HIV and Syphilis. The IBN researchers are also investigating the use of other common fluid samples, such as blood, urine and serum for rapid, high-sensitivity test kits. The Institute is currently collaborating with ARKRAY Inc., a pioneer in the field of automated analysis systems, to commercialize its paper-based diagnostic technology. In 2013, ARKRAY opened its first Asian research center outside Japan in IBN with an investment of S$9.1 million over five years. The research center is focused on developing novel detection kits for infectious diseases based on IBN's innovative diagnostic platforms. Mr. Atsushi Murakami, General Manager of the R&D Division of ARKRAY Inc., said: "We have developed an excellent working relationship with IBN over the past two years, and our research activities have progressed rapidly. Together, we will continue to focus on the successful commercialization of new technologies for the diagnosis of tropical infectious diseases." IBN has been focused on research in medical technologies since 2003, and has created unique devices and assays for the rapid and accurate diagnosis of diseases. The institute has an active portfolio of 500 patents/patent applications, of which 86 have been licensed. It has spun off seven companies in the medical technology sector and its innovations have attracted major interest from the industry.
Quantum chemical models are used to form a picture of the forces and tensions at play between the atoms and electrons of a molecule,” says Simen Reine (left) and Trygve Helgaker, who for the last thirty years has taken the international lead on the design of a computer system for calculating quantum chemical reactions in molecules. Quantum chemical calculations are needed to explain what happens to the electrons’ trajectories within a molecule. Consider what happens when UV radiation sends energy-rich photons into your cells. This increases the energy level of the molecules. The outcome may well be that some of the molecules break up. This is exactly what happens when you sun-bathe. “The extra energy will affect the behaviour of electrons and can destroy the chemical bonding within the molecule. This can only be explained by quantum chemistry. The quantum chemical models are used to produce a picture of the forces and tensions at play between the atoms and the electrons of a molecule, and of what is required for a molecule to dissociate,” says Trygve Helgaker. The absurd world of the electrons The quantum chemical calculations solve the Schrödinger equation for molecules. This equation is fundamental to all chemistry and describes the whereabouts of all electrons within a molecule. But here we need to pay attention, for things are really rather more complicated than that. Your high school physics teacher will have told you that electrons circle the atom. Things are not that simple, though, in the world of quantum physics. Electrons are not only particles, but waves as well. The electrons can be in many places at the same time. It’s impossible to keep track of their position. However, there is hope. Quantum chemical models describe the electrons’ statistical positions. In other words, they can establish the probable location of each electron. The results of a quantum chemical calculation are often more accurate than what is achievable experimentally. Among other things, the quantum chemical calculations can be used to predict chemical reactions. This means that the chemists will no longer have to rely on guesstimates in the lab. It is also possible to use quantum chemical calculations in order to understand what happens in experiments. Enormous calculations The calculations are very demanding. “The Schrödinger equation is a highly complicated, partial differential equation, which cannot be accurately solved. Instead, we need to make do with heavy simulations”, says researcher Simen Kvaal. The computations are so demanding that the scientists use one of the University’s fastest supercomputers. “We are constantly stretching the boundaries of what is possible. We are restricted by the available machine capacity,” explains Helgaker. Ten years ago it took two weeks to carry out the calculations for a molecule with 140 atoms. Now it can be done in two minutes. “That’s 20,000 times faster than ten years ago. The computation process is now running 200 times faster because the computers have been doubling their speed every eighteen months. And the process is a further 100 times faster because the software has been undergoing constant improvement,” says senior engineer Simen Reine. This year the research group has used 40 million CPU hours, of which twelve million were on the University’s supercomputer, which is fitted with ten thousand parallel processors. This allows ten thousand CPU hours to be over and done with in 60 minutes. “We will always fill the computer’s free capacity. The higher the computational capacity, the bigger and more reliable the calculations.” Thanks to ever faster computers, the quantum chemists are able to study ever larger molecules. Today, it’s routine to carry out a quantum chemical calculation of what happens within a molecule of up to 400 atoms. By using simplified models it is possible to study molecules with several thousand atoms. This does, however, mean that some of the effects within the molecule are not being described in detail. The researchers are now getting close to a level which enables them to study the quantum mechanics of living cells. “This is exciting. The molecules of living cells may contain many hundred thousand atoms, but there is no need to describe the entire molecule using quantum mechanical principles. Consequently, we are already at a stage when we can help solve biological problems.” Hunting for the electrons of the insulin molecule The chemists are thus able to combine sophisticated models with simpler ones. “This will always be a matter of what level of precision and detail you require. The optimal approach would have been to use the Schrödinger equation for everything.” 
Working with Aarhus University, Simen Reine has calculated the tensions between the electrons and atoms of an insulin molecule. An insulin molecule consists of 782 atoms and 3,500 electrons. (Illustration: Simen Reine-UiO) By way of compromise they can give a detailed description of every electron in some parts of the model, while in other parts they are only looking at average numbers. “We are always having to find a good balance between the details we need and those we don’t need.” Simen Reine has been using the team’s computer program, while working with Aarhus University, on a study of the insulin molecule. An insulin molecule consists of 782 atoms and 3,500 electrons. “All electrons repel each other, while at the same time being pulled towards the atom nuclei. The atom nuclei also repel each other. Nevertheless, the molecule remains stable. In order to study a molecule to a high level of precision, we therefore need to consider how all of the electrons move relative to one another. Such calculations are referred to as correlated equations and are very reliable.” A complete correlated equation of the insulin molecule takes nearly half a million CPU hours. If they were given the opportunity to run the program on the University’s supercomputer, the calculations would theoretically take two days. “In ten years, we’ll be able to make these calculations in two minutes.” Medically important Vice Rector Knut Fægri at the University of Oslo points out that quantum chemical calculations may become important to life sciences. “Quantum chemical calculations can help describe phenomena at a level that may be difficult to access experimentally, but may also provide support for interpreting and planning experiments. Today, the calculations will be put to best use within the fields of molecular biology and biochemistry,” says Knut Fægri. Associate Professor Michele Cascella at the Centre for Theoretical and Computational Chemistry has recently been recruited from Italy to introduce quantum chemistry into life sciences. “Quantum chemistry is a fundamental theory which is important for explaining molecular events, which is why it is essential to our understanding of biological systems,” says Michele Cascella. By way of an example, he refers to the analysis of enzymes. Enzymes are molecular catalysts that boost the chemical reactions within our cells. Cascella also points to nanomedicines, which are drugs tasked with distributing medicine round our bodies in a much more accurate fashion. “In nanomedicine we need to understand physical phenomena on a nano scale, forming as correct a picture as possible of molecular phenomena. In this context, quantum chemical calculations are important,” explains Michele Cascella. Proteins and enzymes Professor K. Kristoffer Andersson at the Department of Biosciences uses the simpler form of quantum chemical calculations to study the details of protein structures and the chemical atomic and electronic functions of enzymes. “It is important to understand the chemical reaction mechanism, and how enzymes and proteins work. Quantum chemical calculations will teach us more about how proteins go about their tasks, step by step. We can also use the calculations to look at activation energy, i.e. how much energy is required to reach a certain state. It is therefore important to understand the chemical reaction patterns in biological molecules in order to develop new drugs,” says Andersson. His research will also be useful in the search for cancer drugs. He studies radicals, which may be important to cancer. Among other things, he is looking at the metal ions function in proteins. These are ions with a large number of protons, neutrons and electrons. Photosynthesis Professor Einar Uggerud at the Department of Chemistry has uncovered an entirely new form of chemical bonding through sophisticated experiments and quantum chemical calculations. Working with research fellow Glenn Miller, Professor Uggerud has found an unusually fragile key molecule, in a kite-shaped structure, consisting of magnesium, carbon and oxygen. The molecule may provide a new understanding of photosynthesis. Photosynthesis, which forms the basis for all life, converts CO2 into sugar molecules. The molecule reacts so fast with water and other molecules that it has only been possible to study in isolation from other molecules, in a vacuum chamber. “Time will tell whether the molecule really has an important connection with photosynthesis,” says Einar Uggerud.
Nanodiamonds are tiny crystals only a few nanometres in size. (Image: Mohamed Sennour, MINES ParisTech) “The interaction between the nanodiamonds and the neighbouring molecules and ions is especially strong in water”, say Petit. The adsorption of active pharmaceutical ingredients on nanodiamonds can be influenced, for example, by adding salts or changing the pH value. Petit and his colleagues have now discovered that the electronic signature of surface states of nanodiamonds in aqueous dispersions are considerably different from those of nanodiamonds on a solid-state substrate. With the help of micro-jet technology developed by Emad Aziz at HZB, they examined liquid samples in vacuum using X-ray spectroscopy and developed a detailed picture of the filled and unfilled electron states in valence and conduction bands. Their results show that holes, i.e. missing electrons in the valence band, formed on the surfaces of the nanodiamonds in the aqueous dispersion. “This suggests that electrons at the surface of nanodiamonds are donated to the surrounding water molecules”, Petit suggests. The physicists suspect they might also influence the nanoparticles’ chemical, optical, and catalytic properties through changes to their electronic structure. They would like to determine in future studies whether the catalytic effect of nanodiamonds in aqueous environment can be increased in order to split water molecules into oxygen and hydrogen using light.
A scanning electron micrograph of one of the one-dimensional diamond crystal cavities. (Image: MIT) Impurities trapped in diamond The memory elements described in this research are the spin states of electrons in nitrogen-vacancy (NV) centers in diamond. The NV consists of a nitrogen atom in the place of a carbon atom, adjacent to a crystal vacancy inside the carbon lattice of diamond. The up or down orientation of the electron spins on these NV centers can be used to encode information in a way that is somewhat analogous to how the charge of many electrons is used to encode the "0"s and "1"s in a classical computer. The scientists preferentially orient the NV's spin, whose direction is naturally randomly oriented, along a particular direction. This step prepares a quantum state of "0". From there, scientists can manipulate the electron spins into "1" or back into "0" using microwaves. The "0" state has brighter fluorescence than the "1" state, allowing scientists to measure the state in an optical microscope. The trick is getting the electron spins in the NV centers to hold onto the stable spin states long enough to perform these logic-gate operations—and being able to transfer information among the individual memory elements to create actual computing networks. "It is already possible to transfer information about the electron spin state via photons, but we have to make the interface between the photons and electrons more efficient. The trouble is that photons and electrons normally interact only very weakly. To increase the interaction between photons and the NV, we build an optical cavity—a trap for photons—around the NV," Englund said. 
Building quantum memories on a chip: Diamond photonic crystal cavities (ladder-like structures) are integrated on a silicon substrate. Green laser light (green arrow) excites electrons on impurity atoms trapped within the cavities, picking up information about their spin states, which can then be read out as red light (red arrow) emitted by photoluminescence from the cavity. The inset shows the nitrogen-vacancy (NV)-nanocavity system, where a nitrogen atom (N) is substituted into the diamond crystal lattice in place of a carbon atom (gray balls) adjacent to a vacancy (V). Layers of diamond and air keep light trapped within these cavities long enough to interact with the nitrogen atom's spin state and transfer that information via the emitted light. (Image: MIT) Light and mirrors These cavities, nanofabricated at Brookhaven by MIT graduate student Luozhou Li with the help of staff scientist Ming Lu of the CFN, consist of layers of diamond and air tightly spaced around the impurity atom of an NV center. At each interface between the layers there's a little bit of reflection—like the reflections from a glass surface. With each layer, the reflections add up—like the reflections in a funhouse filled with mirrors. Photons that enter these nanoscale funhouses bounce back and forth up to 10,000 times, greatly enhancing their chance of interacting with the electrons in the NV center. This increases the efficiency of information transfer between photons and the NV center's electron spin state. The devices' performance was characterized in part using optical microscopy in a magnetic field at the CFN, performed by CFN staff scientist Mircea Cotlet, Luozhou Li, and Edward Chen, who is also a graduate student studying under the guidance of Englund at MIT. "Coupling the NV centers with these optical resonator cavities seemed to preserve the NV spin coherence time—the duration of the memory," Cotlet said. Added Englund: "These methods have given us a great starting point for translating information between the spin states of the electrons among multiple NV centers. These results are an important part of validating the scientific promise of NV-cavity systems for quantum networking." In addition, said Li, "The transferred hard mask lithography technique that we have developed in this work would benefit most unconventional substrates that aren't suitable for typical high-resolution patterning by electron beam lithography. In our case, we overcame the problem that hundred-nanometer-thick diamond membranes are too small and too uneven. " The methods may also enable the long-distance transfer of quantum-encoded information over fiber optic cables. Such information could be made completely secure, Englund said, because any attempt to intercept or measure the transferred information would alter the photons' properties, thus alerting the sender and the recipient to the possible presence of an eavesdropper.
In a series of experiments over the last five years, Igor Sokolov used an atomic force microscope like the one at left to look for physical differences between cancer cells and healthy cells. Sokolov’s instrument of choice is the atomic force microscope (AFM), which uses its minuscule finger-like probe to measure tiny forces at a very small scale, “pretty much between individual atoms,” he says. He first came across this technology as a graduate student studying the origins of the universe more than 20 years ago, about the time the AFM was invented. He used it to look for evidence of theoretical elementary particles. When Sokolov didn’t find any, his work helped put those ideas to bed. Soon Sokolov turned the instrument toward more earthly concerns. By 1994, as a member of the microbiology department at the University of Toronto, he was among the first to use AFM to study bacteria. Zooming in on a probiotic bacterium used to make Swiss cheese, Sokolov revealed a never-before-documented process by which the cell repairs its surface after sustaining chemical damage. The experiment also demonstrated AFM’s ability to detect mechanical changes in living cells at unprecedented resolution—something that would be useful in Sokolov’s later work. “That was the beginning of my love of biomedical applications,” says Sokolov, who also has appointments in the departments of biomedical engineering and physics. Closer Look at Cancer More recently, Sokolov and his colleagues have used atomic force microscopy on some of the most mysterious cells of all—malignant ones. Most existing diagnostic tools use the cells’ chemical footprint to identify cancer. In a series of experiments over the last five years, he looked for physical differences between cancer cells and healthy cells that could help physicians diagnose cancer earlier and more accurately. Early detection substantially increases patients’ chances of survival. He and his collaborators have had some promising results in preliminary studies using cervical and bladder cancer cells—“cancers where you can harvest cells without biopsies—very un-invasive methods,” he points out. In 2009, Sokolov and his colleagues at Clarkson University in New York studied healthy and diseased cells that were virtually identical, biochemically speaking. Searching for some physical or mechanical difference that could help distinguish the two types of cells, the researchers found that the surface coat surrounding cancer cells—what Sokolov calls the pericellular brush layer—was markedly different from that of the normal ones. “That was definitely new,” he says, noting that similar results were recently published by researchers using more traditional biochemical methods. “The authors called those findings the result of the change of paradigm of looking at cancer.” The pericellular brush layer is something like a cell’s fur coat, and it can resemble that of a Persian cat or that of a mangy mutt. It’s in the density and size of this brush layer that the researchers found significant differences between cancer cells and healthy cells. In a 2009 paper published in , the team reported observing a relatively uniform brush layer in healthy cells, while in cancerous cells, they saw a two-tiered brush layer, with sparse long hairs and dense short bristles. When the scientists dusted cell cultures with fluorescent particles, they could see—even with the naked eye—that the particles had stuck to the cancerous cells, leaving glowing evidence of the disease. “You don’t need any device to see the difference. It created a very strong visible gradient for cancer cells,” Sokolov says. That fact turned out to be more interesting than useful as a diagnostic tool, though. That’s because the suspect cells have to be cultured in a dish—and scientists can already identify cancerous cells simply by watching them grow. The Fractal Time Bomb So Sokolov’s team searched for other parameters that might alert pathologists to the presence of cancer. After testing many cellular characteristics, the researchers found one key variation, a trait called “fractal dimensionality.” Fractals are defined as “self-similar” patterns that look about the same at various scales. They occur often in nature. Think of a tree: the thinnest leaf-bearing twigs repeat the patterns of the broader branches below. They look about the same as you zoom in or out; you lose your sense of scale without another object to tip you off. “Fractals typically occur in nature from chaotic behavior. Cancer has been associated with chaos as well. Therefore, many researchers predicted connection between cancer and fractals,” Sokolov explains. And when his team used AFM to look at the surface of cells, the researchers saw virtually a 100 percent difference in the fractal dimensionality of normal and cancer cells, a finding they reported in the journal in 2011. 
A detail of a map of the mechanical properties of a plant cell created by Igor Sokolov using a new technique with the atomic force microscope. More recently, Sokolov and his colleagues were able to determine that this fractal geometry occurs during a specific, intermediary phase of cancer progression. The results—recently submitted for publication—might one day help doctors not just diagnose the disease but also monitor its progression. “So far what we have seen is pretty precise, way more precise that anything that is available to doctors to diagnose cervical cancer today,” says Sokolov. He notes that the common Pap smear test is prone to turning up false positives and missing early cancers. Though the test has brought mortality rates down since its introduction, it has never been the subject of a randomized controlled trial—the gold standard of scientific research—and there are no universally accepted definitions of the test results, according to the National Cancer Institute. “It still has insufficient accuracy, leading to costly and unpleasant unnecessary biopsies,” says Sokolov. The cancer research is just one of several projects Sokolov and his two postdoctoral fellows together with four graduate students—two mechanical engineers and two biomedical engineers—have underway in their labs at 200 Boston Avenue. The group, with collaborators from Tufts Medical Center, Dartmouth College and institutions all over Boston, is also looking for other nanotech approaches to diagnosing cancer. They’ve already developed a high-resolution, high-speed test that could eventually lead to a new way to study changes in cells when they become malignant. Thinking more long-range, Sokolov floats the idea of a nanoparticle patrolling the body that can change color when it detects something bad. “Like a time bomb, some of these cells will turn cancerous,” he says. “At early stages, cancer is pretty easily killed, so early diagnosis may help eradicate it.”
This image shows a one-pot selective monofunctionalization of CPP via a chromium complex. (Image: ITbM, Nagoya University) Arenes are known to coordinate to transition metals and the corresponding metal complexes exhibit different reactivities relative to the free arene. CPPs, which consist of a chain of arenes, also reacted with chromium carbonyl to successfully generate the first chromium complex of CPP. Interestingly, the main product was a CPP with one chromium moiety complexed to one arene on the outer side of the ring, as confirmed by 1H NMR (nuclear magnetic resonance) spectroscopy, high-resolution mass spectrometry and X-ray crystallography. "Chromium arene chemistry is a well-established area and we decided to apply this organometallic method to synthesize the first CPP chromium complex," says Itami, the Director of the JST-ERATO project and the Institute of Transformative Bio-Molecules. "As CPPs have a number of arene rings, we initially expected that chromium would form a complex with each arene ring," says Segawa, a group leader of the JST-ERATO project. "However, we were surprised to see that CPP reacted with chromium in a 1:1 ratio in all the conditions that we tried. Simulation of the molecular structure suggested that the first equivalent of chromium complexed to CPP lowers its reactivity, thus preventing the reaction with a second chromium moiety." Upon finding that a monometallic CPP complex could be obtained, Itami's team explored the possibility of obtaining monofunctionalized CPPs from this complex. Itami and Segawa describe the steps in achieving this. "This was not an easy task as chromium arene complexes are usually air and light sensitive, and CPP chromium complexes were no exception. But Natsumi worked persistently to obtain a pure crystal of the first CPP chromium complex," says Itami. "We then performed the subsequent reactions in one-pot, to synthesize monofunctionalized CPPs after addition of base/electrophiles and removal of the metal from the CPP chromium complex," says Segawa. Selective monofunctionalizations of CPPs i.e. installation of one functional group at a single position on the arene ring, are difficult to achieve as all carbon-hydrogen bonds on the arene rings are chemically equivalent. Direct functionalization of metal-free CPPs usually leads to multiple substitutions on the arene rings in an uncontrolled manner. Despite CPPs being desirable components for carbon nanotubes, there has been no efficient method to obtain directly functionalized CPPs up to now. "We were pleased to see that a functional group could be selectively installed on one arene ring via chromium coordination of CPPs," says Segawa. "As electrophiles, we utilized silyl, boryl and ester groups, which act as handles that can be easily transformed to other useful functionalities," he continues. Itami says, "We hope that this new approach evolves to become a valuable method to construct carbon nanotubes with unique structures and properties."
Illustration of controlled energy flow from electrons into photons and plasmons. (Image: ICFO) Erbium ions are commonly used in optical amplifiers, emitting light at the near-infrared wavelength of 1.5 microns. This wavelength is in an important band for optical telecommunications, as there is very little energy loss in the range, and thus an efficient transmission of information. In the paper, the first author of which is Klaas-Jan Tielrooij, the researchers show that energy flow from erbium into photons or plasmons can be controlled by applying a small voltage between the erbium and graphene layers. Surface plasmons in graphene are very strongly confined, with a plasmon wavelength two orders of magnitude smaller than the wavelength of emitted photons. As the charge carrier density of the graphene sheet is gradually increased, the erbium ions shift from exciting electrons in the graphene sheet to emitting photons or plasmons. These experiments reveal long-sought-after graphene plasmons at the near-infrared frequencies used in telecommunications applications. In addition, the strong concentration of optical energy observed offers new possibilities for data storage and manipulation through active plasmonic networks. ICFO quantum nano-optoelectronics group leader and study co-author Frank Koppens says: "This work shows that electrical control of light at the nanometer scale is possible and efficient, thanks to the optoelectronics properties of graphene." Commenting on the role of the Graphene Flagship, Koppens adds: "The Graphene Flagship is an excellent platform for collaborative efforts on complex projects. It fosters the exchange of ideas, materials and devices, and at the same provides a path forward for the realisation of practical applications."
Broadly speaking, organic solar cells convert light into electric current in four steps. First, the cell absorbs sunlight, which excites electrons in the active layer of the cell. Each excited electron leaves behind a hole in the active layer. The electron and hole is collectively called an exciton. In the second step, called diffusion, the exciton hops around until it encounters an interface with another organic material in the active layer. When the exciton meets this interface, you get step three: dissociation. During dissociation, the exciton breaks apart, freeing the electron and respective hole. In step four, called charge collection, the free electron makes its way through the active layer to a point where it can be harvested. In previous organic solar cell research, there was ambiguity about whether differences in efficiency were due to dissociation or charge collection – because there was no clear method for distinguishing between the two. Was a material inefficient at dissociating excitons into free electrons? Or was the material just making it hard for free electrons to find their way out? To address these questions, the researchers developed a method that takes advantage of a particular characteristic of light: if light is polarized so that it “runs” parallel to the long axis of organic solar cell molecules, it will be absorbed; but if the light runs perpendicular to the molecules, it passes right through it. The researchers created highly organized nanostructures within a portion of the active layer of an organic solar cell, meaning that the molecules in that portion all ran the same way. They left the remaining regions of the cell disorganized, meaning the molecules ran in a bunch of different directions. This design allowed the researchers to make the organized areas of the cell effectively invisible by controlling the polarity of light aimed at the active layer. In other words, the researchers could test just the organized section or just the disorganized section – even though they were on the same active layer of the same solar cell. Because the charge collection would be the same for both regions (since they were on the same active layer), the technique allowed the researchers to measure the degree to which structural organization affected the material’s dissociation efficiency. “We found that there was no relationship between dissociation efficiency and structural organization,” O’Connor says. “It was really a surprise, and it tells us that we don’t need highly ordered nanostructures for efficient free electron generation. “In practical terms, this technique will help distinguish efficiency losses of newly developed materials, helping define which material and nanostructure features are needed to advance organic solar cell technology.”
The fabrications were made in a steel sheet with lasers and are chiral microstructures, which means the top and bottom layers are identical in composition but arranged asymmetrically. It’s the first such material to be made out of a single medium. (Image: Guoliang Huang) "Methods of controlling and manipulating subwavelength acoustic and elastic waves have proven elusive and difficult; however, the potential applications--once the methods are refined--are tremendous," said Guoliang Huang, associate professor of mechanical and aerospace engineering in the College of Engineering at MU. "Our team has developed a material that, if used in the manufacture of new devices, could have the ability to sense sound and elastic waves. By manipulating these waves to our advantage, we would have the ability to create materials that could greatly benefit society--from imaging to military enhancements such as elastic cloaking--the possibilities truly are endless." In the past, scientists have used a combination of materials such as metal and rubber to effectively 'bend' and control waves. Huang and his team designed a material using a single component: steel. The engineered structural material possesses the ability to control the increase of acoustical or elastic waves. Improvements to broadband signals and super-imaging devices also are possibilities. The material was made in a single steel sheet using lasers to engrave "chiral," or geometric microstructure patterns, which are asymmetrical to their mirror images (see photo). It's the first such material to be made out of a single medium. Huang and his team intend to introduce elements they can control that will prove its usefulness in many fields and applications. "In its current state, the metal is a passive material, meaning we need to introduce other elements that will help us control the elastic waves we send to it," Huang said. "We're going to make this material much more active by integrating smart materials like microchips that are controllable. This will give us the ability to effectively 'tune in' to any elastic sound or elastic wave frequency and generate the responses we'd like; this manipulation gives us the means to control how it reacts to what's surrounding it." Going forward, Huang said there are numerous possibilities for the material to control elastic waves including super-resolution sensors, acoustic and medical hearing devices, as well as a "superlens" that could significantly advance super-imaging, all thanks to the ability to more directly focus the elastic waves.
Generally, adsorbates from the ambient (such as moisture or oxygen) and residuals from lithography processes used during device fabrication adhere to the graphene and change its doping level unintentionally. As these contaminants are unstable under normal conditions, the doping level and hence the electrical and optical properties of graphene devices also change. The variation in these parameters is a major roadblock for using graphene devices in applications. The researchers at AMO GmbH and Graphenea SE have identified this problem and investigated the encapsulation of graphene field effect devices using aluminum oxide, an encapsulation material well known for OLEDs. The key parameter for device passivation found in this study is the growth of an oxide layer using a properly in-situ oxidized aluminum seed layer. The employed passivation layer is able to persistently stabilize the device characteristics over several months when stored and measured in ambient atmosphere. This is a major step towards the use of graphene devices in real applications. The research work is published in the Royal Society of Chemistry journal ("Highly Air Stable Passivation of Graphene Based Field Effect Devices"). The work is financially supported by the European Commission under the projects GRAFOL (contract no. 285275), Flagship Graphene (contract no. 604391), and by the German Science Foundation under the project Ultragraphen (contract no. BA3788/2-1).
Monitoring of the condensation of xenon: Depicted in scanning tunneling microscopy are three different quantum wells that contain one, two and three xenon atoms. The team headed by Professor Thomas Jung, which consists of researchers from the Swiss Nanoscience Institute, Department of Physics at the University of Basel and the Paul Scherrer Institute, developed a method enabling the condensation of individual atoms to be mapped on a step by step basis for the first time. The researchers allowed atoms of the noble gas xenon to condensate in quantum wells and monitored the resulting accumulations using a scanning tunneling microscope. Quantum wells as beakers The autonomous organization of specifically 'programmed' molecules facilitates the creation of a porous network on a substrate surface – these are the quantum wells used as measuring beakers with a specifically defined size, shape and atomic wall and floor structure. The atoms' freedom of movement is restricted in the quantum wells, allowing the arrangement of the atoms to be closely monitored and mapped depending on the composition. With this data, the researchers were able to show that the xenon atoms always arrange themselves according to a certain principle. For example, some units consisting of four atoms are only formed when there are at least seven atoms in the quantum well. And if there are twelve atoms in the quantum well, this results in the creation of three highly stable four-atom units. Conclusions about the nature of bonding The images and structures of nano-condensates recorded for the first time allow key conclusions to be drawn as to the nature of the physical bonds formed by the xenon atoms. "But this system is not restricted exclusively to noble gases," says Sylwia Nowakowska, lead author of the publication. "We can also use it to research other atoms and the way that they bond." As the newly developed method accurately maps atomic bonding and determines the stability of the various states, it can also be used to verify theoretical calculations about bonds.
A closeup shows how the nanotextured square of silicon completely blocks reflection compared with the surrounding silicon wafer. Preventing reflections requires controlling an abrupt change in "refractive index," a property that affects how waves such as light propagate through a material. This occurs at the interface where two materials with very different refractive indices meet, for example at the interface between air and silicon. Adding a coating with an intermediate refractive index at the interface eases the transition between materials and reduces the reflection, Black explained. "The issue with using such coatings for solar cells," he said, "is that we'd prefer to fully capture every color of the light spectrum within the device, and we'd like to capture the light irrespective of the direction it comes from. But each color of light couples best with a different antireflection coating, and each coating is optimized for light coming from a particular direction. So you deal with these issues by using multiple antireflection layers. We were interested in looking for a better way." For inspiration, the scientists turned to a well-known example of an antireflective surface in nature, the eyes of common moths. The surfaces of their compound eyes have textured patterns made of many tiny "posts," each smaller than the wavelengths of light. This textured surface improves moths' nighttime vision, and also prevents the "deer in the headlights" reflecting glow that might allow predators to detect them. "We set out to recreate moth eye patterns in silicon at even smaller sizes using methods of nanotechnology," said Atikur Rahman, a postdoctoral fellow working with Black at the CFN and first author of the study. The scientists started by coating the top surface of a silicon solar cell with a polymer material called a "block copolymer," which can be made to self-organize into an ordered surface pattern with dimensions measuring only tens of nanometers. The self-assembled pattern served as a template for forming posts in the solar cell like those in the moth eye using a plasma of reactive gases—a technique commonly used in the manufacture of semiconductor electronic circuits. The resulting surface nanotexture served to gradually change the refractive index to drastically cut down on reflection of many wavelengths of light simultaneously, regardless of the direction of light impinging on the solar cell. 
Details of the nanotextured antireflective surface as revealed by a scanning electron microscope at the Center for Functional Nanomaterials. The tiny posts, each smaller than the wavelengths of light, are reminiscent of the structure of moths' eyes, an example of an antireflective surface found in nature. "Adding these nanotextures turned the normally shiny silicon surface absolutely black," Rahman said. Solar cells textured in this way outperform those coated with a single antireflective film by about 20 percent, and bring light into the device as well as the best multi-layer-coatings used in the industry. "We are working to understand whether there are economic advantages to assembling silicon solar cells using our method, compared to other, established processes in the industry," Black said. Hidden layer explains better-than-expected performance One intriguing aspect of the study was that the scientists achieved the antireflective performance by creating nanoposts only half as tall as the required height predicted by a mathematical model describing the effect. So they called upon the expertise of colleagues at the CFN and other Brookhaven scientists to help sort out the mystery. "This is a powerful advantage of doing research at the CFN—both for us and for academic and industrial researchers coming to use our facilities," Black said. "We have all these experts around who can help you solve your problems." Using a combination of computational modeling, electron microscopy, and surface science, the team deduced that a thin layer of silicon oxide similar to what typically forms when silicon is exposed to air seemed to be having an outsized effect. "On a flat surface, this layer is so thin that its effect is minimal," explained Matt Eisaman of Brookhaven's Sustainable Energy Technologies Department and a professor at Stony Brook University. "But on the nanopatterned surface, with the thin oxide layer surrounding all sides of the nanotexture, the oxide can have a larger effect because it makes up a significant portion of the nanotextured material." Said Black, "This 'hidden' layer was the key to the extra boost in performance." The scientists are now interested in developing their self-assembly based method of nanotexture patterning for other materials, including glass and plastic, for antiglare windows and coatings for solar panels.
Three strategies for producing colors of pixels containing four aluminum nanodisks. Row 1: varying the nanodisk diameter (d) gives 15 colors. Row 2: Varying both the spacing (s) and diameter (d) of the nanodisks gives over 300 colors. Row 3: Varying the diameters (d1 and d2) of the two pairs of diametrically opposite nanodisks gives over 100 colors. (© American Chemical Society) (Also see our Nanowerk Spotlight on this research: "Photorealistic plasmonic printing with aluminum nanostructures") Conventional pigments produce colors by selectively absorbing light of different wavelengths — for example, red ink appears red because it absorbs strongly in the blue and green spectral regions. A similar effect can be realized at a much smaller scale by using arrays of metallic nanostructures, since light of certain wavelengths excites collective oscillations of free electrons, known as plasmon resonances, in such structures. An advantage of using metal nanostructures rather than inks is that it is possible to enhance the resolution of color images by a hundred fold. This enhanced resolution, at the diffraction limit of light, is critical for data storage, digital imaging and security applications. Aluminum — because of its low cost and good stability — is a particularly attractive material to use. Joel Yang and Shawn Tan at the A*STAR Institute of Materials Research and Engineering and co-workers used an electron beam to form arrays of approximately 100-nanometer-tall pillars. They then deposited a thin aluminum layer on top of the pillars and in the gaps between them. In these arrays, each pixel was an 800-nanometer-long square containing four aluminum nanodisks. The plasmon resonance wavelength varies sensitively with the dimensions of the nanostructures. Consequently, by varying the diameter of the four aluminum nanodisks in a pixel (all four nanodisks having the same diameter), the scientists were able to produce about 15 distinct colors — a good start, but hardly enough to faithfully reproduce full-color images. By allowing two pairs of diametrically opposite nanodisks to have different diameters from each other, then varying the two diameters enabled them to increase this number to over 100. Finally, they generated over 300 colors by varying both the nanodisk diameter (but keeping all four diameters within a pixel the same) and the spacing between adjacent nanodisks in a pixel (see image). “This method is analogous to half-toning used in ink-based printing and results in a broad color gamut,” comments Yang. The researchers demonstrated the effectiveness of their extended palette using a Monet painting. They reproduced the image using both a limited and extended palette, with a much better color reproduction from the extended palette. Amazingly, they shrank the image from 80 centimeters to a mere 300 micrometers — a 2,600-fold reduction in size. “The use of a more cost-effective metal has the potential to move this technology closer to adoption,” Tan notes.