Atomii -materiale cuantice topologice

clase de materiale complet noi, cunoscut sub numele de „materiale cuantice topologice^

Posted: May 31, 2016
Atome mit dem gewissen Twist (Nanowerk News) Gewisse Materialien wie Metalle leiten den Strom, andere, sogenannte Isolatoren wie Glas oder Keramik nicht. Nun ist es Forschern der Universität Hamburg erstmals gelungen, die zentrale Kenngröße einer Klasse ganz neuer Materialien, der sogenannten „topologischen Quantenmaterialien“ zu vermessen. Von diesem speziellen „Twist“, einer trickreichen Verdrehung der Wege der Elektronen, hängen zum Beispiel die Leitfähigkeit und andere Eigenschaften ab.
Die Ergebnisse eröffnen ganz neue Perspektiven für die Entwicklung neuer Quantenmaterialien, auch mit potenziellen Anwendungen bei zukünftigen Quantencomputern. Sie wurden nun im Fachmagazin Science veröffentlicht („Experimental reconstruction of the Berry curvature in a Floquet Bloch band”).

Künstlerische Darstellung der berechneten Geometrie der Eigenstände der zwei Bloch-Bänder. (Bild: UHH/Sengstock)
In üblichen Materialien müssen sich Elektronen, die für den Stromtransport verantwortlich sind, ihren Weg durch gleichmäßig verteilte Hindernisse im Festkörper bahnen. In den topologischen Quantenmaterialien können sich Teilchen dagegen nur auf gewissen, mehr oder weniger verdrehten Wegen (die einen Twist beinhalten) bewegen und verhalten sich entsprechend den Gesetzen der Quantenphysik zudem wie Teilchen und Wellen gleichzeitig.
Es gibt eine zentrale Eigenschaft, die die Topologie, also den Quanten-Twist dieser Materialien, komplett beschreiben kann: die „Berry Krümmung“, benannt nach dem englischen Physiker Michael Berry, der das Grundkonzept dazu bereits in den 1980er Jahren angelegt hat. Das Team um Prof. Dr. Klaus Sengstock und Dr. Christof Weitenberg vom Institut für Laserphysik der Universität Hamburg konnte die Berry Krümmung in einem Quantenmaterial nun erstmalig vollständig vermessen.
Die Physiker nutzten bewusst ein künstliches Quantenmaterial, das heute weltweit intensiv eingesetzt wird: atomare Wolken – sogenannte „ultrakalte Quantengase“ – in einem künstlichen Festkörper, gebildet aus Laserlicht. Nachdem die Atome, die in diesen Experimenten die Rolle von Elektronen in Festkörpern übernahmen, in das künstliche Material, das die zu untersuchende Topologie enthielt, eingebracht worden waren, konnte mithilfe weiterer Laser diese Topologie sehr präzise gemessen werden.
Dr. Weitenberg, der die Experimente betreute, betont: „Wir konnten bereits in diesen ersten Experimenten die Topologie eines künstlichen Materials bestimmen, und das ist erst der Anfang, wir alle sind sehr begeistert von den Möglichkeiten dieser neuen Methode.“ Prof. Sengstock ergänzt: „Neuartige Quantenmaterialien werden schon in naher Zukunft eine wichtige Rolle in den absehbaren Quantentechnologien spielen; Quantencomputer sind dabei besonders visionär und nur durch neue Konzepte zu verwirklichen.“ Materialien mit dem gewissen Twist können vermutlich dazu wichtige Beiträge liefern: „Es ist besonders spannend, in diesem Bereich zu forschen, da das Forschungsfeld dieser neuen Quantenmaterialien erst ganz am Anfang steht, vieles ist noch gar nicht erforscht“, so Prof. Sengstock.

Source: Universität Hamburg

Nanotehnologii sunt pași mici spre fabricarea atomică la scară 3D

se va deschide porțile pentru tehnologiile emergente în calcul, energie, cataliza, și o serie de alt articol de revizuire recente fields.A (în ACS Nano „Directing Materia: Spre Nanofabrication Atomic-Scale 3D „) Ilustrează utilizarea fascicule de electroni și ioni concentrat (e-grinzi și traverse) pentru a induce reacții chimice foarte localizate la interfețe solide la vapori și solid-lichid, amorfe transformări de fază cristaline cu precizie strat atomic, iar mișcarea atom specific dopant unic, în barilor de cristal, punând astfel bazele pentru asamblarea atomically precis direcționată a materialelor și a creșterii devices.

Nanotechnology’s tiny steps toward atomic-scale 3D fabrication

(Nanowerk Spotlight) Over the past few decades, the development of electron microscopy has gone hand in hand with techniques for atomically precise fabrication of 3D structures based on electron and ion beams.All material functionality is governed by the type, arrangement, and bonding of atoms. Enabling the capacity to perform atomically precise directed assembly of matter will open the doors to emerging technologies in computing, energy, catalysis, and a plethora of other fields.A recent review article in ACS Nano („Directing Matter: Toward Atomic-Scale 3D Nanofabrication”) illustrates the use of focused electron and ion beams (e-beams and i-beams) to induce highly localized chemical reactions at solid-vapor and solid-liquid interfaces, amorphous to crystalline phase transformations with atomic layer precision, and the motion of specific single dopant atoms within crystal lattices, thus laying the foundation for atomically precise directed assembly of materials and devices.The growth of plasmonic gold nanostructures by electron beam induced deposition (EBID) has been demonstrated already 10 years ago and the physics behind this nanofabrication technique has been explored (see for instance: „Scientists unveil new physics behind the nanofabrication technique of electron beam induced deposition„). The process has been improved over the years and researchers are now able to grow structures much faster with a broad range of precursors (see: „A new process for rapidly fabricating complex 3D nanostructures„).In their review, the authors emphasize the synergy between imaging, nanofabrication, and modeling in order to reveal the fundamental mechanisms of charged particle-surface interaction.They present several recent examples that suggest the feasibility of atomically precise fabrication in the bulk, including creating specific dopant configurations, ordered vacancy planes, and other structures.The article covers EBID/IBID from gas or liquid precursors, e-beam-induced crystallization in the bulk, and the ability to image and to analyze single atoms and defects in 2D structures.(a) Patterning of a MoSe nanowire network, where each nanowire is sculpted individually. (b) Ramified Y junction made of three MoSe nanowires. (c-l) Serial snapshots of the sculpting process of individual MoSe (c-g) and MoS (h-l) nanowires. All images are STEM Z-contrast images, false-colored for better visibility. Scale bars, 2 nm (a), 0.5 nm (b-l). (© Nature Publishing Group) (click on image to enlarge)Electron-beam/ion-beam-induced deposition from gas precursorsDiscussing Focused Electron-Beam-Induced Processing – a nanoscale direct-write synthesis technique where an electron beam directs assembly of a surface-adsorbed precursor via an electron-stimulated chemical reaction – and Focused Ion-Beam-Induced Processing – where the deposition and etching of nanoscale materials is induced by a focused ion beam – the authors show how these techniques were developed; they discuss their benefits but also obstacles to large-scale implementation.Eelectron-beam/ion-beam-induced deposition from liquid precursorsAn alternative pathway to using gas precursors for direct nanofabrication is direct-write with electron and/or ion beams with a liquid precursor. This method utilizes the e-beam or i-beam as an ionizing source that decomposes solvent molecules to generate solvated electrons and other radicals in a complex cascade of reaction pathways.When using electrons to direct-write in solution, the minimal size of the created structures is limited to the nanometer scale due to the fundamental physics of the interactions between the electron beam and the liquid, including the lateral transport of solvated electrons and ionic species. The helium ion beam, on the other hand, might offer the potential for improved resolution.Atomically precise e-beam-induced crystallization in the bulkE-beam and i-beam patterning are popular and versatile approaches for creating structures on ∼10-100 nm scales, typically in SEM-like geometry. However, in the field of imaging, high-resolution transmission electron microscopy (TEM) has long been a tool of choice because it allows for atomic-scale studies of crystals and nanoparticles.As the authors note, over the last 15 years, aberration correction has pushed the achievable resolution into the sub-angstrom range and allowed for much greater localization of the probe in STEM geometry, suggesting that higher precision patterning should be achievable using these improved electron probes.Provided that the electron beam path can be programmed, localization of features in the areas illuminated by the beam and the ability to control their growth allows for more complex patterning.The team writes that the manufacturing of epitaxial crystalline nanostructures with predefined shapes is particularly interesting, as adjustable strain states could yield ways to control properties, and the ordered final structures can be more easily modeled than amorphous structures.(a,d) ADF Z-contrast images of two representative stable Si6 cluster configurations embedded in a graphene pore. (b,e) Two- and (c,f) three-dimensional structures obtained from first-principles calculations. Si and C atoms below the graphene plane are shaded. L or R labels are used to highlight when the oscillating Si atom is either at the left or right sites. Scale bar, 0.2 nm. (© Nature Publishing Group) (click on image to enlarge)Single-atom dynamics and beyondThe difficulties in manipulating single atoms for nanoscale engineering were famously highlighted by Stemmer („Three-dimensional imaging of individual dopant atoms in SrTiO3„).The use of an electron beam might provide an answer to this dilemma by allowing the direct addressing of single atoms in bulk 3D materials.The review highlights results („Direct Observation of Dopant Atom Diffusion in a Bulk Semiconductor Crystal Enhanced by a Large Size Mismatch”) that show the interplay between the materials science aspect of calculated diffusion barriers and the energy supplied to the sample by the electron beam.As the authors point out: „This relation is important because it is possible to directly control the accelerating voltage in a (S)TEM, thereby altering the energy transferred to the material. This concept raises several tantalizing prospects for the future as to what extent the final position of the dopant can be controlled. If single dopants could be directly manipulated, an obvious application would be toward quantum computing.”Link theory and dataIncreasing computer power and more sophisticated analytical software allows analyzing experimental data in near real-time. This provides the ability to have rapid feedback to and from models and simulations that both inform and validate the simulations/model, which may ultimately provide predictive capabilities to guide experiments.Until recently, advances in microscopy relied on improvements in the instrumentation platforms, focused probes, lenses, detectors, measurement modalities, and mathematical tools for extraction of materials-specific parameters from imaging data. However, in almost all cases, due to the complexity and size of the available signals, only a small, manually selected subset of the fully generated information volume is recorded and an even smaller subset of this is processed.In the future, new tools will allow the (real-time) monitoring and analysis of the full data stream from the microscope. This would also allow researchers to take full advantage of all of the information contained in experimental data to provide input into computational methods to predict and understand materials.The authors conclude that „in order to see what is happening as it is happening, a significant emphasis must be placed on forming a tight loop between expansive dynamic streaming EELS (electron energy loss spectroscopy), tomographic, and ptychographic data sets provided by experimental platforms and the model-driven interpretation of the data. As the techniques mature, these theory-in-the-loop approaches will also significantly expedite the quality control process, an important facet in transitioning from scientific test-beds to high-volume manufacturing.”By Michael Berger – Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny.

Sprijinirea dezvoltării responsabile a nanotehnologiei

Se pot detecta acum nanoparticule cu mult sub nivelurile de toxicitate cunoscute și sub pragul acțiunilor de reglementare economice și rezonabile Înlătură probleme complexe de determinare a biomarkerilor expunerii legate de boală problemei complexe de determinare a biomarkerilor expunerii legate de boală.

Posted: May 31, 2016
Supporting responsible development of nanotechnology (Nanowerk News) Nanotechnology environmental, health, and safety (nanoEHS) activities have become a hallmark of the National Nanotechnology Initiative (NNI). Well-coordinated nanoEHS research and development (R&D) is essential to ensuring a future in which responsible development of nanotechnology provides maximum benefit to society and the environment. These efforts are pivotal in contributing to American innovation and to advancing manufacturing and economic competitiveness.
Progress in nanoEHS research is vital to establishing the regulatory certainty and public confidence needed for companies to bring their nanotechnology products to market and to ensuring that these products are safe and sustainable throughout their life cycles.
Three reports recently released highlight Federal investments and activities in this area, progress and needs in understanding exposure from consumer products, and how businesses can protect their nanotechnology workforce. In addition, an upcoming workshop will explore the work of joint U.S.–European Union nanoEHS communities of research in developing a shared repertoire of protocols and methods.
The recently released NNI Supplement to the President’s Budget for Fiscal Year 2017, which serves as the annual report for the NNI, highlights the programs and coordinated activities taking place across the many departments, independent agencies, and commissions participating today in the NNI—an initiative that continues to serve as a model for effective coordination of Federal science and technology R&D.
As detailed in this report, nanoEHS activities continue to account for about 10 percent of the annual NNI budget, with cumulative Federal R&D investments in this area exceeding $1 billion over the past decade. This report includes descriptions of a wide variety of individual agency and coordinated activities supporting the responsible development of nanotechnology.
To understand and control the risks of using any new materials in consumer products, it is important to understand the potential for exposure and any associated hazards across product life cycles. Last month, the NNI released a report, Quantifying Exposure to Engineered Nanomaterials (QEEN) from Manufactured Products: Addressing Environmental, Health, and Safety Implications, summarizing a workshop on this topic sponsored by the U.S. Consumer Product Safety Commission (CPSC).
The main goals of the workshop were to assess progress in developing tools and methods for quantifying exposure to engineered nanomaterials across the product life cycle, and to identify new research needed to advance exposure assessment for nanotechnology-enabled products. As noted in the report, significant progress has been made in the ability to quantify nanomaterial exposures, such that available methods can now detect nanoparticles well below known toxicity levels and beneath the threshold of economical and reasonable regulatory action. However, greater understanding of exposure risks in “real-world” scenarios is needed, along with techniques, based on alternative testing models and high-throughput methods for rapidly estimating exposures.
The technical experts who participated in CPSC’s workshop recommended that future work focus on the complex issue of determining biomarkers of exposure linked to disease, which will require substantive public–private collaboration, partnership, and knowledge sharing. Recognizing these needs, the President’s 2017 Budget request for CPSC (pdf) includes funds for a new nanotechnology center led by the National Institute of Environmental Health Sciences (NIEHS) to develop test methods and to quantify and characterize the presence, release, and mechanisms of consumer exposure to nanomaterials in consumer products. This cost-effective, interagency collaboration will enable CPSC—through NIEHS—to collect the needed data to inform the safety of nanotechnology in consumer products and allow CPSC to benefit from NIEHS’s scientific network and experience.
Managing EHS risks across a product’s lifecycle includes protecting the workers who manufacture those products. The National Institute for Occupational Safety and Health has issued a series of documents providing guidance to this emerging industry, including the recently released publication Building a Safety Program to Protect the Nanotechnology Workforce: A Guide for Small to Medium-Sized Enterprises. This guide provides business owners with the tools necessary to develop and implement a written health and safety program to protect their employees.
The responsible development of nanotechnology is a goal that the United States shares with many countries. The United States and the European Union are engaged in notable cooperation on this front. European and American scientists engaged in nanoEHS research convene annually for a joint workshop to identify areas of shared interest and mechanisms for collaboration to advance nanoEHS science. The 2016 joint workshop will be held on June 6–7, 2016 in Arlington, VA, and is free and open to the public. Registration opened on April 6, 2016, on a first-come, first-served basis.

Source: By Lloyd Whitman, Assistant Director for Nanotechnology and Advanced Materials at the White House Office of Science and Technology Policy

Creșterea cristalelor perfecte prin umplerea golurilor

Cristalele sunt materiale solide compuse din blocuri microscopice, dispuse în modele foarte ordonat. Ei au nenumărate aplicații, variind de la metalurgie la electronice la bijuterii. Multe dintre proprietățile au făcut cristale utile depind de modelul detaliat al aranjament al constituenților lor, care, la rândul său, este extrem de sensibil la detaliile interacțiunii dintre blocurile de construcție. In cristalele moleculare si atomice forțele interparticule sunt fixate de Natura, iar singura modalitate de tuning aranjament microscopic este de a varia fie condițiile externe (temperatură, presiune, etc.) sau de a modifica particulele Înșiși.amestecurilor de coloizi si particule pe baza de polimeri numiti polimeri stele

Posted: May 31, 2016
Growing perfect crystals by filling the gaps (Nanowerk News) Be it in phyics, metallurgy, gemology or engineering, the applications of crystals are very broad. A research team including Christos Likos and Lorenzo Rovigatti from the Faculty of Physics of the University of Vienna, in collaboration with the National Institute of Standards and Technology (NIST, USA) and Princeton University (USA) has developed a new method to assemble large, periodic crystals. The results have been published in the Journal ACS Nano („Bottom-Up Colloidal Crystal Assembly with a Twist”).

The scientists have shown that long-range order can be restored by employing mixtures of colloids and polymer-based particles called star polymers (Image: Christos Likos, Universität Wien)
Crystals are solid materials composed of microscopic building blocks arranged in highly ordered patterns. They have countless applications, ranging from metallurgy to jewellery to electronics. Many of the properties that make crystals useful depend on the detailed pattern of arrangement of their constituents, which, in turn, is highly sensitive to the details of the interaction between the building blocks. In molecular and atomic crystals the interparticle forces are fixed by Nature, and the only way of tuning the microscopic arrangement is to either vary the external conditions (temperature, pressure, etc.) or change the particles themselves.
By contrast, insoft matter Physics , where the building blocks are orders of magnitude larger and much more complex than atoms, it is possible to design and engineer building blocks with extremely tunable properties. Consequently, much effort has been devoted to the synthesis of colloids that self-assemble into highly symmetric patterns with technologically relevant properties. For instance, there exist specific crystal lattices that exhibit very exciting optical properties, the so-called photonic crystals – periodic structures that allow certain bands of wavelengths of light to propagate through their interior while blocking other ones.
A natural example of a photonic crystal is the opal, whose fascinating coloration is due to the way the light interacts with its microscopic structure of colloidal particles arranged on a regular lattice. The multicolored iridescence of the precious opal, the source of its charming appearance, is due to the presence of several small crystals, known as crystallites, which are randomly oriented with respect to the one another.
In addition, the assembly of colloidal crystals is often confounded by polymorphism: „Different structures are characterised by comparable thermodynamic stabilities, making it difficult to produce a single morphology at will”, says Christos Likos from the Faculty of Physics of the University of Vienna.
The resulting lack of long-range order is detrimental for many applications. Accordingly, strategies need to be developed that enhance the growth of long-ranged, monocrystalline samples in (real or numerical) experiments. Accordingly, scientists have been working hard to deveop strategies that enhance the growth of large, monocrystalline structures. Employing computer simulations, a new method has now been developed that allows the assembly of technologically relevant, non-polymorphic crystals.
„The system crystallises into a mixture of difference micocrystals. However, the competing structures assembled by the colloids have different geometries and different internal void distributions. This difference can be exploited by tuning the size of polymer additive to interact uniquely with the void symmetry of the desired crystal, effectively stabilising it against the competitor”, explains Lise-Meitner Fellow Lorenzo Rovigatti, working at the group of Christos Likos.
The results of the research team serve not only to illustrate an alternative to existing approaches which, in many cases, produce unsatisfactory results, but also to guide experimental realizations of highly-ordered colloidal open crystals in the near future.

Source: Universität Wien

Camera de atracție pentru nanostructuri

O tehnologie care ar putea transfera și de a salva datele codificate pe undele de lumina ar fi de 100.000 de ori mai rapid decât sistemele actuale. O interacțiune materie de lumină, care ar putea deschide calea de a căuta produse electronice bazate pe lumina a fost investigata de catre oamenii de stiinta de la Laboratorul de Attosecond Fizica (PLA) Ludwig-Maximilians-University (LMU) și Institutul Max Planck de Optică Cuantică (MPQ ), în colaborare cu colegii de la Catedra de fizica cu laser de la Universitatea din Erlangen-Nuremberg. Cercetatorii au trimis impulsuri laser intens pe un nanofire mic din aur. Cele ultrascurte impulsului laser excitat vibrația electronilor se deplasează liber în metal.
Acest lucru a dus la electromagnetic „lângă câmpuri“ la suprafața firului. Cvasi-câmpuri a oscilat cu o schimbare de câteva sute de attoseconds în ceea ce privește câmpul cu laser interesant (un Attosecond este o miliardime de miliardime de secundă). Această schimbare ce Măsurat folosind impulsuri de lumina Attosecond pe care oamenii de știință trimis ulterior Onto nanowire.
Atunci când lumina se aprinde metale, aceasta poate duce la lucruri curioase în microcosmos la suprafață. Câmpul electromagnetic al luminii excită vibratii ale electronilor din metal. Această interacțiune determină formarea „aproape-câmpuri“ – câmpuri electromagnetice localizate în apropierea suprafeței metalului.

Posted: May 31, 2016
Attosecond camera for nanostructures (Nanowerk News) Physicists of the Laboratory for Attosecond Physics at the Max Planck Institute of Quantum Optics and the Ludwig-Maximilians-Universität Munich in collaboration with scientists from the Friedrich-Alexander-Universität Erlangen-Nürnberg have observed a light-matter phenomenon in nano-optics, which lasts only attoseconds („Attosecond nanoscale near-field sampling”).
The interaction between light and matter is of key importance in nature, the most prominent example being photosynthesis. Light-matter interactions have also been used extensively in technology, and will continue to be important in electronics of the future.

When laser light interacts with a nanoneedle (yellow), electromagnetic near-fields are formed at its surface. A second laser pulse (purple) emits an electron (green) from the needle, permitting to characterize the near-fields. (Image: Christian Hackenberger)
A technology that could transfer and save data encoded on light waves would be 100.000-times faster than current systems. A light-matter interaction which could pave the way to such light-driven electronics has been investigated by scientists from the Laboratory for Attosecond Physics (LAP) at the Ludwig-Maximilians-Universität (LMU) and the Max Planck Institute of Quantum Optics (MPQ), in collaboration with colleagues from the Chair for Laser Physics at the Friedrich-Alexander-Universität Erlangen-Nürnberg. The researchers sent intense laser pulses onto a tiny nanowire made of gold. The ultrashort laser pulses excited vibrations of the freely moving electrons in the metal.
This resulted in electromagnetic ‘near-fields’ at the surface of the wire. The near-fields oscillated with a shift of a few hundred attoseconds with respect to the exciting laser field (one attosecond is a billionth of a billionth of a second). This shift was measured using attosecond light pulses which the scientists subsequently sent onto the nanowire.
When light illuminates metals, it can result in curious things in the microcosm at the surface. The electromagnetic field of the light excites vibrations of the electrons in the metal. This interaction causes the formation of ‘near-fields’ – electromagnetic fields localized close to the surface of the metal.
How near-fields behave under the influence of light has now been investigated by an international team of physicists at the Laboratory for Attosecond Physics of the Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics in close collaboration with scientists of the Chair for Laser Physics at the Friedrich-Alexander-Universität Erlangen-Nürnberg.
The researchers sent strong infrared laser pulses onto a gold nanowire. These laser pulses are so short that they are composed of only a few oscillations of the light field. When the light illuminated the nanowire it excited collective vibrations of the conducting electrons surrounding the gold atoms. Through these electron motions, near-fields were created at the surface of the wire.
The physicists wanted to study the timing of the near-fields with respect to the light fields. To do this they sent a second light pulse with an extremely short duration of just a couple of hundred attoseconds onto the nanostructure shortly after the first light pulse. The second flash released individual electrons from the nanowire. When these electrons reached the surface, they were accelerated by the near-fields and detected. Analysis of the electrons showed that the near-fields were oscillating with a time shift of about 250 attoseconds with respect to the incident light, and that they were leading in their vibrations. In other words: the near-field vibrations reached their maximum amplitude 250 attoseconds earlier than the vibrations of the light field.
“Fields and surface waves at nanostructures are of central importance for the development of lightwave-electronics. With the demonstrated technique they can now be sharply resolved.”, explained Prof. Matthias Kling, the leader of the team carrying out the experiments in Munich.
The experiments pave the way towards more complex studies of light-matter interaction in metals that are of interest in nano-optics and the light-driven electronics of the future. Such electronics would work at the frequencies of light. Light oscillates a million billion times per second, i.e. with petahertz frequencies – about 100.000 times faster than electronics available at the moment. The ultimate limit of data processing could be reached.

Source: Max Planck Institute of Quantum Optics

Văzând nanofibrele „vii” în timp real

care poseda flexibilitatea si diversitatea de functii care exista intr-o celula vii.Putem controla auto-sortarea cu moleculele artificiale,putem lucra pentru a dezvolta inteligente

Posted: May 31, 2016
Seeing ‘living’ nanofibers in real time (w/video) (Nanowerk News) The Greek goddess Psyche borrowed help from ants to sort a room full of different grains. Cells, on the other hand, do something similar without Olympian assistance, as they organize molecules into robust, functional fibers. Now scientists are able to see self-sorting phenomena happen in real time with artificial molecules.
The achievement, reported in Nature Chemistry („In situ real-time imaging of self-sorted supramolecular nanofibers”), elucidates how two different types of nanofibers sort themselves into organized structures under artificial conditions.

Real-time imaging of supramolecular nanofibers?Video: Itaru Hamachi)
„Basic cellular structures, such as actin filaments, come into being through the autonomous self-sorting of individual molecules, even though a tremendous variety of proteins and small molecules are present inside the cell,” says lead author Hajime Shigemitsu, a researcher in Itaru Hamachi’s lab at Kyoto University.
„Imagine a box filled with an assortment of building blocks – it’s as if the same type of blocks started sorting themselves into neat bundles all on their own. In living cells, such phenomena always happen, enabling accurate self-assembling of proteins, which is essential for cell functions.”
„If we are able to control self-sorting with artificial molecules, we can work toward developing intelligent, next-generation biomimics that possess the flexibility and diversity of functions that exist in a living cell.”
Study co-author Ryou Kubota explains that previous studies have already made artificial molecules build themselves into fibers – but only when there was one type of molecule around. Having a jumble of types, on the other hand, made the molecules confused.
„The difficulty in inducing self-assembly with artificial molecules is that they don’t recognize the same type of molecule, unlike molecules in the natural world. Different types of artificial molecules interact with each other and make an unsorted cluster.”
From a database of structural analyses, Hamachi and colleagues discovered a combination of nanofibers – namely a peptide-based and lipid-based hydrogelator – that would make sorted fibers without mixing with the other. They then tethered the fibers with fluorescent probes; with a type of microscope typically used in cell imaging, the team was able to observe directly and in real-time how the artificial molecules sorted themselves.
„Ultimately, this finding could help develop new materials that respond dynamically to different environments and stimuli,” elaborates Hamachi. „This insight is not only useful for materials science, but may also provide useful clues for understanding self-organization in cells.”

Source: Kyoto University

Materialele slabe oferă posibilități puternice pentru electronică

crisal compus din bismut combinat fie cu iod sau bromÎnlătură termen: izolatoare topologice izolatoare topologiceÎnlătură termen: Materialele conductive din punct de vedere electric Materialele conductive din punct de vedere electric

Posted: May 31, 2016
Weak materials offers strong possibilities for electronics (Nanowerk News) New fundamental research by University of Texas at Dallas physicists may accelerate the drive toward more advanced electronics and more powerful computers.
The scientists are investigating materials called topological insulators, whose surface electrical properties are essentially the opposite of the properties inside.
“These materials are made of the same thing throughout, from the interior to the exterior,” said Dr. Fan Zhang, assistant professor of physics at UT Dallas. “But, the interior does not conduct electrons — it’s an insulator — while the electrons on the surface are free to move around. The surface is therefore a conductor, like a metal, but it is in fact more robust than a metal.”
There are two types of topological insulators: strong and weak. The difference between them is subtle and involves complex physics, but is critically important.
“If you had a cube of material that is a strong topological insulator, all six faces can conduct electrons,” Zhang said. “For the weak one, only the four sides are conducting, while the top and bottom surfaces remain insulating.”
Strong topological insulators were made experimentally shortly after they were theoretically proposed. Zhang said they are common in nature, and several dozen variations have been identified and experimentally confirmed.
On the other hand, weak topological insulators have been more elusive. Scientists have proposed various ways to construct a weak topological insulator, but because of its distinctive properties, researchers have not been able to say definitively that they have experimentally produced one.

UT Dallas scientists have made crystals of bismuth iodide and are investigating the material’s exotic electrical properties for possible use in advanced electronics.
Zhang, a theoretical physicist, has devised a new way to make a weak topological insulator, one that involves a relatively simple mix of two chemical elements: a crystal composed of bismuth combined with either iodine or bromine. He and his colleagues published the research recently in the journal Physical Review Letters („Weak Topological Insulators and Composite Weyl Semimetals: β-Bi4X4 (X=Br, I)”) and presented their work at the March meeting of the American Physical Society.
In the 1970s, German scientists grew bismuth iodides and bismuth bromides, but they didn’t understand their potential as weak topological insulators, Zhang said.
“This class of materials we are proposing is a unique platform for exploring exotic physics with fairly simple chemistry,” he said. “With further research and experimentation, our findings could lead to significant advances in technology, especially in electronics and quantum computing.”
Electrically conductive materials are the fundamental building blocks of the traditional transistors that power electronic devices including cellphones and computers. Researchers are developing new theories and experiments with innovative physics and materials to create new transistor-like technologies that run devices and make computers more powerful.
With such exotic electrical properties, topological insulators offer a potential option, Zhang said.
“Our lives have been modified over time by our understanding of the conduction of electrons and the exploitation of this physics for use in electronic devices,” he said. “We now need to revolutionize transistors. One possible substitution is a so-called topological field effect transistor, which could be made of a thin film of a weak topological insulator.”
Computers also are heading for a fundamental redesign, and those efforts might be aided by Zhang’s research.
“The fundamental computing scale is now very limited,” he said. “For many applications, like weather forecasting and information encoding and decoding, today’s computers are way too slow. However, quantum computers have been proposed that would use the principles of quantum physics to compute exponentially faster than today’s computers.
“Weak topological insulators could make quantum computing feasible.”
As a theorist, Zhang used old-fashioned pencil and paper to construct the basis of his theory about the bismuth compounds. His postdoctoral researcher Dr. Cheng-Cheng Liu, the study’s lead author and now an assistant professor at Beijing Institute of Technology, then crunched specific numbers using high-speed supercomputers at the Texas Advanced Computing Center based at UT Austin.
Zhang’s UT Dallas colleague, Dr. Bing Lv, assistant professor of physics, has made samples of bismuth iodide.
“The next step will be to characterize the material to explore the unique properties that a weak topological insulator can offer to fundamental physics and to our everyday lives,” Zhang said.

Source: University of Texas at Dallas

Sondă nanometrica ar putea produce îmbunătățiri majore în baterii și celule de combustie

îmbunătățiri majore în baterii și celule de combustie îmbunătățiri majore în baterii și celule de combustie.Proprietățile materialelor pot afecta performanța bateriilor și a altor sisteme electrochimice.

Posted: May 31, 2016
Tiny probe could produce big improvements in batteries and fuel cells (Nanowerk News) A team of American and Chinese researchers has developed a new tool that could aid in the quest for better batteries and fuel cells.
Although battery technology has come a long way since Alessandro Volta first stacked metal discs in a „voltaic pile” to generate electricity, major improvements are still needed to meet the energy challenges of the future, such as powering electric cars and storing renewable energy cheaply and efficiently.
The key to the needed improvements likely lies in the nanoscale, said Jiangyu Li, a professor of Mechanical Engineering at the University of Washington in Seattle. The nanoscale is a realm so tiny that the movement of a few atoms or molecules can shift the landscape. Li and his colleagues have built a new window into this world to help scientists better understand how batteries really work. They describe their nanoscale probe in the Journal of Applied Physics („Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale”).

This is a nanoscale map of the metal ceria produced with the new probe shows a higher response, represented by a yellow color, near the boundary between grains of metal. The higher response corresponds to a higher concentration of charged species. (Image: Ehsan Nasr Esfahani/University of Washington) (click on image to enlarge)
Batteries, and their close kin fuel cells, produce electricity through chemical reactions. The rates at which these reactions occur determine how fast the battery can charge, how much power it can provide, and how quickly it degrades.
Although the material in a battery electrode may look uniform to the human eye, to the atoms themselves, the environment is surprisingly diverse.
Near the surface and at the interfaces between materials, huge shifts in properties can occur – and the shifts can affect the reaction rates in complex and difficult-to-understand ways.
Research in the last ten to fifteen years has revealed just how much local variations in material properties can affect the performance of batteries and other electrochemical systems, Li said.
The complex nanoscale landscape makes it tricky to fully understand what’s going on, but „it may also create new opportunities to engineer materials properties so as to achieve quantum leaps in performance,” he said.
To get a better understanding of how chemical reactions progress at the level of atoms and molecules, Li and his colleagues developed a nanoscale probe. The method is similar to atomic force microscopies: A tiny cantilever „feels” the material and builds a map of its properties with a resolution of nanometers or smaller.
In the case of the new electrochemical probe, the cantilever is heated with an electrical current, causing fluctuations in temperature and localized stress in the material beneath the probe. As a result, atoms and ions within the material move around, causing it to expand and contract. This expansion and contraction causes the cantilever to vibrate, which can be measured accurately using a laser beam shining on the top of the cantilever.
If a large concentration of ions or other charged particles exist in the vicinity of the probe tip, changes in their concentration will cause the material to deform further, similar to the way wood swells when it gets wet. The deformation is called Vegard strain.
Both Vegard strain and standard thermal expansion affect the vibration of the material, but in different ways. If the vibrations were like musical notes, the thermally-induced Vegard strain is like a harmonic overtone, ringing one octave higher than the note being played, Li explained.
The device identifies the Vegard strain-induced vibrations and can extrapolate the concentration of ions and electronic defects near the probe tip. The approach has advantages over other types of atomic microscopy that use voltage perturbations to generate a response, since voltage can produce many different kinds of responses, and it is difficult to isolate the part of the response related to shifts in ionic and electronic defect concentration. Thermal responses are easier to identify, although one disadvantage of the new system is that it can only probe rates slower than the heat transfer processes in the vicinity of the tip.
Still, the team believes the new method will offer researchers a valuable tool for studying electrochemical material properties at the nanoscale. They tested it by measuring the concentration of charged species in Sm-doped ceria and LiFePO4, important materials in solid oxide fuel cells and lithium batteries, respectively.
„The concentration of ionic and electronic species are often tied to important rate properties of electrochemical materials – such as surface reactions, interfacial charge transfer, and bulk and surface diffusion – that govern the device performance,” Li said. „By measuring these properties locally on the nanoscale, we can build a much better understanding of how electrochemical systems really work, and thus how to develop new materials with much higher performance.”

Source: American Institute of Physics

Mantis crevete inspiră următoarea generație de materiale ultra-puternice

Descoperirea structurii de heringbone rezistente la impacturi .Se foloseste la automobile, armuri,inclusiv aerospațial . Materiale compozite super-puternnice. Proiectează următoarea generație de materiale pentru o varietate de aplicații .Structură unică de heringbone în stratul exterior al clubului dactil.

Posted: May 31, 2016
Mantis shrimp inspires next generation of ultra-strong materials (Nanowerk News) Mantis shrimp are available in the lab and can be photographed or videoed.
A video that media are free to use is here: https://www.youtube.com/watch?v=_8K3bx42jVM – The next generation of airplanes, body armor and football helmets crawled out from under a rock–literally.
Researchers at the University of California, Riverside and Purdue University are one step closer to developing super strong composite materials, thanks to the mantis shrimp, a small, multicolored marine crustacean that crushes the shells of its prey using a fist-like appendage called a dactyl club.
Their latest research, to be published in the journal Advanced Materials („A Sinusoidally Architected Helicoidal Biocomposite”), describes for the first time a unique herringbone structure, not previously reported in nature, within the appendage’s outer layer. It is this tough herringbone structure that not only protects the club during impact, but also enables the mantis shrimp to inflict incredible damage to its prey.

This is the herringbone structure of the outer layer (impact region) of the mantis shrimp dactyl club. (Image: UC Riverside) (click on image to enlarge)
Mantis shrimp, also called stomatopods, come in two varieties: ‘smashers’ and ‘spearers.’ While spearers kill prey by driving a spear into soft-bodied sea creatures, smashers kill hard-shelled prey such as crabs and snails by pulverizing them with incredible speed and force. The dactyl club can reach an acceleration of 10,000g, unleashing a barrage of impacts with the speed of a .22 caliber bullet.
For the past eight years, David Kisailus, the Winston Chung Endowed Professor in Energy Innovation in UCR’s Bourns College of Engineering, and his team have been studying smashers’ dactyl clubs and using them as inspiration in their development of next generation composite materials. Their research is already being translated into real-world products by Nature Inspired Industries, a recent startup led by Kisailus that spun out from UC Riverside’s Office of Research and Economic Development.

Mantis shrimp in the lab of David Kisailus at the University of California, Riverside. Kisailus studies the structure of the fist-like club of the mantis shrimp to develop tougher and stronger materials.
In previous work, including a 2012 study published in the journal Science („The Stomatopod Dactyl Club: A Formidable Damage-Tolerant Biological Hammer”), the researchers identified several different regions of the dactyl club, including an interior region–called the periodic region–with an energy-absorbent structure that also filters out damaging shear waves, which travel through objects when they are under stress. This energy absorbing „periodic region” consists of two phases: an organic phase made of chitin–a compound found in the shells of insects and crustaceans–arranged in a helicoidal structure that resembles a spiral staircase, and an inorganic phase comprising amorphous calcium phosphate and calcium carbonate.
The current research, funded by the Air Force Office of Scientific Research under a $7.5M Multi-University Research Initiative that Kisailus leads, describes for the first time a unique herringbone structure within the dactyl club’s outer layer, called the impact region.
The impact region is a crack-resistant layer that shields the club as the mantis shrimp pummels its prey. However, unlike the periodic region, the impact region consists of crystalline calcium phosphate (the same mineral found in human bone) surrounding the organic chitin fibers. The researchers found that these heavily mineralized fibers were compacted to form a „herringbone structure” that is significantly stiffer than the structure in the periodic region. The highly ordered compacted herringbone structure is a pitch-graded sinusoidal arrangement of helicoidal chitin fibers mineralized with highly textured calcium phosphate.
This unique herringbone structure not only protects the club from failure, but also enables the mantis shrimp to inflict incredible damage to its prey by transferring more momentum upon impact.
Although the mechanism of the formation of the herringbone structure has yet to be confirmed, Kisailus speculates that the difference in stresses during the formation of the crystalline material in the impact region causes the helicoidal arrangement to buckle, which can be viewed under high power microscopy as a herringbone pattern.
Adding an additional layer of complexity, the very outer layer of the impact region is different again, offering a thin, particle-like coating around the surface of the dactyl club that acts to delocalize stress that might induce catastrophic failure within the club.
Nicholas Yaraghi, a graduate student in Kisailus’ group who led the current research, said this is the first time the unique herringbone structure has been observed in Nature.
„We knew from previous studies that the impact region allows the mantis shrimp to transfer incredible momentum to its prey while resisting fracture, but it was exciting to reveal through our research that the properties of this highly impact-resistant material are created by the novel herringbone structure,” he said.
In order to confirm their hypotheses, Kisailus and his research group teamed up with Pablo Zavattieri, Associate Professor of Civil Engineering and University Faculty Scholar at Purdue University, and his team to perform finite element analyses to understand the role of these structures. The researchers also fabricated the herringbone structure using synthetic materials and a 3D printer.
Zavattieri and his student Nicolas Guarín-Zapata built computational models that replicate the local details of the herringbone structure. These models explained that damaging stress can be more uniformly distributed, mitigating catastrophic structural failure. Compression testing of the 3D printing biomimetic composite also helped prove that the herringbone structure makes the impact region even more effective than the periodic region in redistributing stress and deflecting cracks.
„While the computational modeling results gave us compelling confirmation of the redistribution of stresses in these structures, the „wow” moment came when we tested our 3D printing samples,” Guarín-Zapata said.
Kisailus said the discovery of the highly impact-resistant herringbone structure adds new inspiration as his team designs the next generation of materials for a variety of applications, including aerospace, automotive and armor.
„The smasher mantis shrimp has evolved this exceptionally strong and impact-resistant dactyl club for one primary purpose–to be able to eat. However, the more we learn about this tiny creature and it’s multi-layered structural designs, the more we realize how much it can help us as we design better planes, cars, sports equipment and armor,” Kisailus said.
Kisailus said recent advances in 3D printing techniques and modeling are making it easier than ever to translate the mantis shrimp’s weapon into new materials.
„By using 3D printing techniques like those used by Zavattieri’s team, we can actually take what we’ve learned about the architecture of the dactyl club and manufacture new composites with traditional engineering materials like polymers and carbon fiber,” Kisailus said. In fact, he says that his team is already fabricating the second generation of composites that incorporates not only the energy-absorbing component, but the stiff outer layer inspired from the mantis. He has demonstrated this by producing a helmet with this hard coating.

Source: University of California – Riverside

Noua tehnică permite vizualizarea defectelor pe suprafața grafenului

Folosind tehnici imagistice avansate, cercetatorii au descoperit, dass die clusterele de paladiu atașați Selectiv la gemäß suprafața grafen la modele specifice, FUNCȚIE cum reactiv centrele de carbon sunt. Particulele de paladiu individuale rezolva Onto defectelor punctuale, acumulări locale de particule sunt prezente pe defecte mai mari și lanțuri scurte contur defecte liniare

Posted: May 31, 2016
New technique allows to visualize defects on the surface of graphene (Nanowerk News) The technique, developed by researchers at the Zelinsky Institute of Organic Chemistry in a collaborative project, employs the metal palladium, which interacts with “carbon reactivity centres” found on graphene. Graphene is an incredibly strong one-atom-thick layer of carbon touted to be an excellent conductor of heat and electricity.
Several types of defects on graphene surfaces are known to increase the reactivity of its carbon atoms: i.e. their ability to form chemical bonds. If researchers can locate these defects and manipulate them, they will be able to maximize the use of graphene’s properties.
For example, locating and removing defects is important for applications that require perfectly smooth graphene.
In other applications, such as in catalysis and certain biomedical materials, some defects are actually beneficial because they allow the incorporation of additional elements, such as metals, into the graphene.

Artistic image on the concept of imaging of carbon defect areas by palladium markers. (Graphene defects marked by Pd). (Image : Ananikov Laboratory, Zelinsky Institute of Organic Chemistry)
When the palladium complex Pd2(dba)3 is dissolved in chloroform, it forms a dark red solution under normal circumstances. But when graphene or another carbon material is added to the solution, the palladium is completely consumed. As a result, the solution turns from dark red to colourless.
Using advanced imaging techniques, the researchers found that the palladium clusters selectively attach to graphene’s surface according to specific patterns, depending on how reactive the carbon centres are. Individual palladium particles settle onto point defects, local accumulations of particles are present on larger defects, and short chains outline linear defects.
These defects are normally invisible under an electron microscope. The palladium particles act like a contrast agent, allowing the spatial imaging of the chemical reactivity, and thus the defects, of graphene layers.
“Metal mapping of carbon materials provides unique insights and reveals hidden information about fascinating properties at the molecular level,” says project leader Professor Valentine Ananikov.
The team’s findings indicate that using palladium markers, more than 2,000 surface defects, or reactivity centres, on graphene can be individually located, per square micrometre of surface area. The researchers say that the unexpected capacity of graphene to accommodate so many reactivity centres challenges scientists to re-examine their understanding of the electronic and structural properties of carbon materials.
Now that the researchers have learned how to recognise and characterise the defects, their next step is to develop a technique to control them. Some defects possess a dynamic nature and have the ability to “migrate” over graphene’s surface. If the researchers can control this migration, they will have a unique opportunity to form materials with customised properties. This is an outstanding direction for future studies, they say

Source: Zelinsky Institute of Organic Chemistry

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Corpurile rapide, elastice ar putea da naștere unui nou val de electronice portabile

Înlătură termen: dimensiuni ale lungimii de undă cuprinse între un milimetru și un metru dimensiuni ale lungimii de undă cuprinse între un milimetru și un metruÎnlătură termen: frecvențele radio cu microunde sunt unde electromagnetice care utilizează frecvențe în intervalul de la 3 gigahertzi la 300 gigahertzi. Aceasta se încadrează direct în domeniul 5G frecvențele radio cu microunde sunt unde electromagnetice care utilizează frecvențe în intervalul de la 3 gigahertzi la 300 gigahertzi. Aceasta se încadrează direct în domeniul 5GÎnlătură termen: noile circuite integrate ar putea fi utilizate în electronice portabile care aderă la piele noile circuite integrate ar putea fi utilizate în electronice portabile care aderă la piele

Posted: May 30, 2016
Fast, stretchy circuits could yield new wave of wearable electronics (Nanowerk News) The consumer marketplace is flooded with a lively assortment of smart wearable electronics that do everything from monitor vital signs, fitness or sun exposure to play music, charge other electronics or even purify the air around you – all wirelessly.
Now, a team of University of Wisconsin-Madison engineers has created the world’s fastest stretchable, wearable integrated circuits, an advance that could drive the Internet of Things and a much more connected, high-speed wireless world.
Led by Zhenqiang „Jack” Ma, the Lynn H. Matthias Professor in Engineering and Vilas Distinguished Achievement Professor in electrical and computer engineering at UW-Madison, the researchers published details of these powerful, highly efficient integrated circuits in the journal Advanced Functional Materials („Stretchable Twisted, Pair Transmission Lines for Microwave Frequency Wearable Electronics”).

Fabricated in interlocking segments like a 3-D puzzle, the new integrated circuits could be used in wearable electronics that adhere to the skin like temporary tattoos. Because the circuits increase wireless speed, these systems could allow health care staff to monitor patients remotely, without the use of cables and cords. (Image: Yei Hwan Jung and Juhwan Lee/University of Wisconsin-Madison)
The advance is a platform for manufacturers seeking to expand the capabilities and applications of wearable electronics – including those with biomedical applications – particularly as they strive to develop devices that take advantage of a new generation of wireless broadband technologies referred to as 5G.
With wavelength sizes between a millimeter and a meter, microwave radio frequencies are electromagnetic waves that use frequencies in the .3 gigahertz to 300 gigahertz range. That falls directly in the 5G range.
In mobile communications, the wide microwave radio frequencies of 5G networks will accommodate a growing number of cellphone users and notable increases in data speeds and coverage areas.
In an intensive care unit, epidermal electronic systems (electronics that adhere to the skin like temporary tattoos) could allow health care staff to monitor patients remotely and wirelessly, increasing patient comfort by decreasing the customary tangle of cables and wires.
What makes the new, stretchable integrated circuits so powerful is their unique structure, inspired by twisted-pair telephone cables. They contain, essentially, two ultra-tiny intertwining power transmission lines in repeating S-curves.
This serpentine shape – formed in two layers with segmented metal blocks, like a 3-D puzzle – gives the transmission lines the ability to stretch without affecting their performance. It also helps shield the lines from outside interference and, at the same time, confine the electromagnetic waves flowing through them, almost completely eliminating current loss. Currently, the researchers’ stretchable integrated circuits can operate at radio frequency levels up to 40 gigahertz.
And, unlike other stretchable transmission lines, whose widths can approach 640 micrometers (or .64 millimeters), the researchers’ new stretchable integrated circuits are just 25 micrometers (or .025 millimeters) thick. That’s tiny enough to be highly effective in epidermal electronic systems, among many other applications.
Ma’s group has been developing what are known as transistor active devices for the past decade. This latest advance marries the researchers’ expertise in both high-frequency and flexible electronics.
„We’ve found a way to integrate high-frequency active transistors into a useful circuit that can be wireless,” says Ma, whose work was supported by the Air Force Office of Scientific Research. „This is a platform. This opens the door to lots of new capabilities.”

Source: By Renee Meiller, University of Wisconsin-Madison

Atome mit dem gewissen Twist

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Seeing ‘living’ nanofibers in real time (w/video)

Weak materials offers strong possibilities for electronics

Tiny probe could produce big improvements in batteries and fuel cells

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New technique allows to visualize defects on the surface of graphene

Fast, stretchy circuits could yield new wave of wearable electronics