Categorie: Materiale noi cu structura compozita

Senzori pentru senzorii de cameră: Un material, multe aplicații(Nanomushroom sensors: One material, many applications)

Diapozitivul este fabricat dintr-un material „nanoplasmonic” – suprafața sa este acoperită în milioane de nanostructuri de aur, fiecare cu doar câteva miliarde de metri pătrați. Materialele plasmonice absorb și dispersează lumina în moduri interesante, oferindu-le proprietăți senzoriale unice. Materialele nanoplasmonice au atras atenția biologilor, chimistilor, fizicienilor și oamenilor de știință cu posibilități de utilizare într-o gamă diversă de domenii, precum biosensibilizarea, stocarea datelor, generarea de lumină și celulele solare.materialele nanoplasmonice pot fi integrate chiar și în tehnologii emergente, cum ar fi sistemele fără fir în dispozitivele microfluidice, permițând utilizatorilor să ia lecturi de la distanță și astfel să reducă la minimum riscul de contaminare.dezvoltat un nou material plasmonic pentru monitorizarea calității produselor alimentare în timpul procesului de fabricație.

Posted: Feb 23, 2018

Nanomushroom sensors: One material, many applications

(Nanowerk News) A small rectangle of pink glass, about the size of a postage stamp, sits on Professor Amy Shen’s desk. Despite its outwardly modest appearance, this little glass slide has the potential to revolutionize a wide range of processes, from monitoring food quality to diagnosing diseases.
The slide is made of a ‘nanoplasmonic’ material – its surface is coated in millions of gold nanostructures, each just a few billionths of a square meter in size. Plasmonic materials absorb and scatter light in interesting ways, giving them unique sensing properties. Nanoplasmonic materials have attracted the attention of biologists, chemists, physicists and material scientists, with possible uses in a diverse array of fields, such as biosensing, data storage, light generation and solar cells.
Nanomushroom Biosensors
Schematic illustration of cells (blue mountain-like shapes) on top of nanoscale mushroom-like structures with silicone dioxide stems and gold caps, which have the potential to detect cell proliferation in real-time. (Image: OIST)
In several recent papers, Prof. Shen and colleagues at the Micro/Bio/Nanofluidics Unit at the Okinawa Institute of Science and Technology (OIST), described their creation of a new biosensing material that can be used to monitor processes in living cells.
„One of the major goals of nanoplasmonics is to search for better ways to monitor processes in living cells in real time,” says Prof. Shen. Capturing such information can reveal clues about cell behavior, but creating nanomaterials on which cells can survive for long periods of time yet don’t interfere with the cellular processes being measured is a challenge, she explains.

Counting Dividing Cells
One of the team’s new biosensors is made from a nanoplasmonic material that is able to accommodate a large number of cells on a single substrate and to monitor cell proliferation, a fundamental process involving cell growth and division, in real time. Seeing this process in action can reveal important insights into the health and functions of cells and tissues.
Researchers in OIST’s Micro/Bio/Nanofluidics Unit described the sensor in a study recently published in the journal Advanced Biosystems („Large-Scale Nanophotonic Structures for Long-Term Monitoring of Cell Proliferation”).
Nanoplasmonic Biosensing Material
Using their innovative printing technique, the Micro/Bio/Nanofluidics Unit at OIST has developed a nanoplasmonic material containing millions of mushroom-like structures covered with a uniform layer of biomolecules. (Image: OIST)
The most attractive feature of the material is that it allows cells to survive over long time periods. „Usually, when you put live cells on a nanomaterial, that material is toxic and it kills the cells,” says Dr. Nikhil Bhalla, a postdoctoral researcher at OIST and first author of the paper. „However, using our material, cells survived for over seven days.” The nanoplasmonic material is also highly sensitive: It can detect an increase in cells as small as 16 in 1000 cells.
The material looks just like an ordinary pieces of glass. However, the surface is coated in tiny nanoplasmonic mushroom-like structures, known as nanomushrooms, with stems of silicon dioxide and caps of gold. Together, these form a biosensor capable of detecting interactions at the molecular level.
The biosensor works by using the nanomushroom caps as optical antennae. When white light passes through the nanoplasmonic slide, the nanomushrooms absorb and scatter some of the light, changing its properties. The absorbance and scattering of light is determined by the size, shape and material of the nanomaterial and, more importantly, it is also affected by any medium in close proximity to the nanomushroom, such as cells that have been placed on the slide. By measuring how the light has changed once it emerges through the other side of the slide, the researchers can detect and monitor processes occurring on the sensor surface, such as cell division.
„Normally, you have to add labels, such as dyes or molecules, to cells, to be able to count dividing cells,” says Dr. Bhalla. „However, with our method, the nanomushrooms can sense them directly.”

Scaling Up
This work builds on a new method, developed by scientists at the Micro/Bio/Nanofluidics Unit at OIST, for fabricating nanomushroom biosensors. The technique was published in the journal ACS Applied Materials and Interfaces in December 2017 („Plasma-Assisted Large-Scale Nanoassembly of Metal–Insulator Bioplasmonic Mushrooms”).
Producing large-scale nanoplasmonic materials is challenging because it is difficult to ensure uniformity across the entire material surface. For this reason, biosensors for routine clinical examinations, such as disease testing, are still lacking.
In response to this problem, the OIST researchers developed a novel printing technique to create large-scale nanomushroom biosensors. With their method, they were able to develop a material consisting of approximately one million mushroom-like structures on a 2.5cm by 7.5cm silicon dioxide substrate.
Nanomushroom biosensors can be used to count dividing cells and detect biomolecules
Nanomushroom biosensors can be used to count dividing cells and detect biomolecules. (Image: OIST)
„Our technique is like taking a stamp, covering it with ink made from biological molecules, and printing onto the nanoplasmonic slide,” says Shivani Sathish, a PhD student at OIST and co-author of the paper. The biological molecules increase the sensitivity of the material, meaning it can sense extremely low concentrations of substances, such as antibodies, and thus potentially detect diseases in their earliest stages.
„Using our method, it is possible to create a highly sensitive biosensor that can detect even single molecules,” says Dr. Bhalla, first author of the paper.
Plasmonic and nanoplasmonic sensors offer important tools for many fields, from electronics to food production to medicine. For example, in December 2017, second year Ph.D student Ainash Garifullina from the Unit developed a new plasmonic material for monitoring the quality of food products during the manufacturing process. The results were published in the journal Analytical Methods („Probing specific gravity in real-time with graphene oxide plasmonics „).
Prof. Shen and her unit say that, in the future, nanoplasmonic materials may even be integrated with emerging technologies, such as wireless systems in microfluidic devices, allowing users to take readings remotely and thereby minimizing the risk of contamination.
Source: By Sophie Protheroe, Okinawa Institute of Science and Technology (OIST) Graduate University

Cercetatorii combina metalens cu un muschi artificial (w / video)(

Inspirata de ochiul uman, cercetatorii de la Harvard John A. Paulson Scoala de Inginerie si Stiinte Aplicate (SEAS) au dezvoltat o metalens adaptive, care este in esenta un ecran plat, controlat electronic. Metalena adaptivă controlează simultan trei dintre cei mai importanți contribuitori la imagini neclare: focalizare, astigmatism și schimbare de imagine.Toate sistemele optice cu componente multiple – de la camere la microscoape și telescoape – au o ușoară aliniere sau solicitări mecanice asupra componentelor lor, în funcție de modul în care au fost construite și de mediul lor actual, care vor determina întotdeauna mici cantități de astigmatism și alte aberații ar putea fi corectat de un element optic adaptiv „, a spus ea. „Deoarece metalendurile adaptive sunt plane, puteți corecta aceste aberații și puteți integra diferite capabilități optice într-un singur plan de control”.
În continuare, cercetătorii urmăresc să îmbunătățească în continuare funcționalitatea obiectivului și să reducă tensiunea necesară pentru controlul acestuia.

Posted: Feb 23, 2018

Researchers combine metalens with an artificial muscle (w/video)

(Nanowerk News) Inspired by the human eye, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed an adaptive metalens, that is essentially a flat, electronically controlled artificial eye. The adaptive metalens simultaneously controls for three of the major contributors to blurry images: focus, astigmatism, and image shift.
The research is published in Science Advances („Adaptive metalenses with simultaneous electrical control of focal length, astigmatism, and shift”).
an adaptive metalens focuses light rays onto an image sensor
The adaptive metalens focuses light rays onto an image sensor. An electrical signal controls the shape of the metalens to produce the desired optical wavefronts (shown in red), resulting in better images. In the future, adaptive metalenses will be built into imaging systems, such as cell phone cameras and microscope, enabling flat, compact autofocus as well as the capability for simultaneously correcting optical aberrations and performing optical image stabilization, all in a single plane of control. (Image: Capasso Lab/Harvard SEAS)
„This research combines breakthroughs in artificial muscle technology with metalens technology to create a tunable metalens that can change its focus in real time, just like the human eye,” said Alan She, a graduate student at SEAS and first author of the paper. „We go one step further to build the capability of dynamically correcting for aberrations such as astigmatism and image shift, which the human eye cannot naturally do.”
„This demonstrates the feasibility of embedded optical zoom and autofocus for a wide range of applications including cell phone cameras, eyeglasses and virtual and augmented reality hardware,” said Federico Capasso, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper. „It also shows the possibility of future optical microscopes, which operate fully electronically and can correct many aberrations simultaneously.”
The Harvard Office of Technology Development has protected the intellectual property relating to this project and is exploring commercialization opportunities.
To build the artificial eye, the researchers first needed to scale-up the metalens.
Prior metalenses were about the size of a single piece of glitter. They focus light and eliminate spherical aberrations through a dense pattern of nanostructures, each smaller than a wavelength of light.
„Because the nanostructures are so small, the density of information in each lens is incredibly high,” said She. „If you go from a 100 micron-sized lens to a centimeter sized lens, you will have increased the information required to describe the lens by ten thousand. Whenever we tried to scale-up the lens, the file size of the design alone would balloon up to gigabytes or even terabytes.”
metalens (made of silicon) mounted on a transparent, stretchy polymer film
Photo of the metalens (made of silicon) mounted on a transparent, stretchy polymer film, without any electrodes. The colorful iridescence is produced by the large number of nanostructures within the metalens. (Image courtesy of the Capasso Lab/Harvard SEAS)
To solve this problem, the researchers developed a new algorithm to shrink the file size to make the metalens compatible with the technology currently used to fabricate integrated circuits. In a paper recently published in Optics Express, the researchers demonstrated the design and fabrication of metalenses up to centimeters or more in diameter.
„This research provides the possibility of unifying two industries: semiconductor manufacturing and lens-making, whereby the same technology used to make computer chips will be used to make metasurface-based optical components, such as lenses,” said Capasso.
Next, the researchers needed to adhere the large metalens to an artificial muscle without compromising its ability to focus light. In the human eye, the lens is surrounded by ciliary muscle, which stretches or compresses the lens, changing its shape to adjust its focal length. Capasso and his team collaborated with David Clarke, Extended Tarr Family Professor of Materials at SEAS and a pioneer in the field of engineering applications of dielectric elastomer actuators, also known as artificial muscles.
The researchers chose a thin, transparent dielectic elastomer with low loss – meaning light travels through the material with little scattering – to attach to the lens. To do so, they needed to developed a platform to transfer and adhere the lens to the soft surface.
„Elastomers are so different in almost every way from semiconductors that the challenge has been how to marry their attributes to create a novel multi-functional device and, especially how to devise a manufacturing route,” said Clarke. „As someone who worked on one of the first scanning electron microscopes (SEMs) in the mid 1960’s, it is exhilarating to be a part of creating an optical microscope with the capabilities of an SEM, such as real-time aberration control.”
The elastomer is controlled by applying voltage. As it stretches, the position of nanopillars on the surface of the lens shift. The metalens can be tuned by controlling both the position of the pillars in relation to their neighbors and the total displacement of the structures. The researchers also demonstrated that the lens can simultaneously focus, control aberrations caused by astigmatisms, as well as perform image shift.
Together, the lens and muscle are only 30 microns thick.
„All optical systems with multiple components – from cameras to microscopes and telescopes – have slight misalignments or mechanical stresses on their components, depending on the way they were built and their current environment, that will always cause small amounts of astigmatism and other aberrations, which could be corrected by an adaptive optical element,” said She. „Because the adaptive metalens is flat, you can correct those aberrations and integrate different optical capabilities onto a single plane of control.”
Next, the researchers aim to further improve the functionality of the lens and decrease the voltage required to control it.
Source: By Leah Burrows, Harvard John A. Paulson School of Engineering and Applied Sciences

Betonul infuzat cu nanocristale din lemn este mai puternic(Concrete infused with wood nanocrystals is stronger)

Cercetatorii spun ca munca in scaling la beton si pregatirea pentru pod in California este un parteneriat intre Purdue, Universitatea de Stat din Oregon, P3Nano si altii. P3Nano este un parteneriat public-privat conceput pentru a sprijini comercializarea nanomaterialelor celulozice. P3Nano a fost implicat activ în studiile la scară largă și este sponsorul proiectului de la Universitatea de Stat din Oregon pentru a demonstra aplicațiile la scară largă ale nanocristalelor de celuloză în poduri și plăci plate. Puntea exactă din California, unde se va utiliza betonul infuzat cu celuloză, nu a fost încă determinată.

Posted: Feb 22, 2018

Concrete infused with wood nanocrystals is stronger

(Nanowerk News) Purdue University researchers studying whether concrete is made stronger by infusing it with microscopic-sized nanocrystals from wood are moving from the laboratory to the real world with a bridge that will be built in California this spring.
The researchers have been working with cellulose nanocrystals, byproducts generated by the paper, bioenergy, agriculture and pulp industries, to find the best mixture to strengthen concrete, the most common man-made material in the world.
“Simply getting out there where people can actually drive on it, I think, is a huge step because you can’t just say it’s a lab curiosity at that point. It has real-world implications,” said Jeffrey Youngblood, a Purdue professor of materials engineering.
Strengthening concrete could have other implications, such as making items made with concrete thinner and lighter while retaining the same strength with a potential side benefit of decreasing carbon dioxide released into the atmosphere. Cement plants account for an estimated 8 percent of global emissions of carbon dioxide, a main cause of climate change.
The catalyst for this potentially transformative change is a cellulose nanocrystal about 100 nanometers long and 5 nanometers wide, too small to be seen using an ordinary microscope. It can be seen only using an electron microscope. For perspective, a human hair is about 100,000 nanometers wide. Yet cellulose is the most common polymer in the world because it can be obtained from wood products, plants, bacteria and algae.
concrete cellulose
This transmission electron microscope shows cellulose nanocrystals, tiny structures derived from renewable sources that might be used to create a new class of biomaterials with many potential applications. The structures have been shown to increase strength of concrete. (Image: Purdue Life Sciences Microscopy Center)
The cellulose nanocrystals make the concrete stronger through a chemical reaction that increases the hydration of the cement particles, making the concrete stronger, the researchers say. “The strength of concrete scales with the degree of hydration. So the more hydrated it is, the stronger it is,” Youngblood said. “So you’d think if you add more water it would be stronger. The problem is, water adds pores that make it weaker. But cellulose nanocrystals enhance hydration with less water, making the concrete stronger.”
Pablo Zavattieri, a professor in the Lyles School of Civil Engineering, said the cellulose nanocrystals provide an avenue for the water to go where it is needed. Not all cement particles are hydrated when concrete is mixed, which hampers the strength and durability of the concrete.
“The good thing about cellulose nanocrystals is it kind of creates a rail for the water to go into a particle, Zavattieri said.
Jason Weiss, the Miles Lowell and Margaret Watt Edwards Distinguished Chair in Engineering at Oregon State University, who previously was a professor at Purdue, said the cellulose nanocrystals make concrete more efficient because less mass is needed to make something that is equally strong.
“So it can be more sustainable and more efficient,” he said.
Youngblood said another benefit is that the cellulose-infused concrete sets faster, which means less waiting for concrete to cure when using forms to make bridges or for oil drilling.
“Because every day that a crew is out there not pumping oil is a day losing money,” Youngblood said.
concrete cellulose samples
This photo shows cement samples embedded in epoxy ready for microscopy analysis. Purdue University researchers have been working to find the best ratio of mixing cellulose nanocrystals into cement to make it stronger.(Image: PurdueUniversity)
The researchers say the cost of using the cellulose nanocrystals may be offset by being able to use less cement, but the exact cost hasn’t been determined. They say how widely cellulose nanocrystals are used will be a factor. But even if only a small percentage of all the concrete produced used the cellulose nanocrystals, it would have a big impact just because concrete use is so ubiquitous.
The researchers say the work in scaling to concrete and preparing for the bridge in California is a partnership between Purdue, Oregon State University, P3Nano and others. P3Nano is a public-private partnership designed to support the commercialization of cellulosic nanomaterial. P3Nano has been actively involved in the full-scale trials and is the sponsor of the project at Oregon State University to demonstrate full-scale applications of cellulose nanocrystals in bridges and flat slabs. The exact bridge in California where the cellulose-infused concrete will be used has not yet been determined.
The Purdue researchers began looking into cellulose a decade ago in collaboration with Robert Moon, a researcher from the U.S. Forest Service Forest Products Laboratory, who was based at Purdue at the time. The Forest Service was looking for uses for diseased, damaged and small-diameter logs, which are plentiful in forests.
Youngblood, who works primarily with plastics, said the challenge initially was determining where the water-soluble cellulose nanocrystals could be used. The idea of using it in concrete came to him while digging a posthole and preparing concrete. That’s where the research began.
Youngblood said the researchers quickly found that the cellulose nanocrystals made the concrete stronger, but they didn’t know why.
“I walked down to the office of Jason Weiss and showed him the data and he said it shouldn’t work because the cellulose nanocrystals are too small. That’s when we realized we had something, because if something based on how things normally work, based on theories or whatever, shouldn’t work and it does, that’s when you usually have found something important,” Youngblood said. “That’s how it all started.”
Source: Purdue University

Amintește-te foarte repede(Remembering really fast)

În compozitele proiectate, conductivitatea electrică poate fi controlată atât de un câmp magnetic aplicat cât și de o temperatură. Activitatea echipei evidențiază o nouă abordare a controlului conductivității în aceste filme subțiri. Astfel de materiale ar putea revoluționa designul dispozitivelor de memorie.
Putem construi dispozitive de memorie noi pentru a face citirea și scrierea datelor la frecvențe terahertz astfel încât dispozitivele noastre personale să poată funcționa la o viteză mult mai mare?Cercetările sugerează promisiunea acestui sistem material pentru viitoarele componente optice și electronice terahertz, cum ar fi modulatorii magnetici.

Posted: Feb 22, 2018

Remembering really fast

(Nanowerk News) Electronics could work faster if they could read and write data at terahertz frequency, rather than at a few gigahertz. Creating such devices would be eased with materials that can undergo a huge change in how easily they conducted electricity in response to a magnetic field at room temperature. Scientists believe thin films of perovskite oxides hold promise for such uses. However, such behavior has never been seen at these frequencies in these films.
Until now. Via terahertz pulses, scientists at Center for Integrated Nanotechnologies and the United Kingdom discovered colossal changes in electricity’s flow at the desired frequencies and temperature (Nano Letters, „Colossal Terahertz magnetoresistance at room temperature in epitaxial La0.7Sr0.3MnO3 nanocomposites and single-phase thin films”).
interactions of terahertz pulses (pink) with a vertically aligned nanocomposite
A graphic depicts the interactions of terahertz pulses (pink) with a vertically aligned nanocomposite. B is the magnetic field and ETHz is the THz electric field. The nanocomposite film includes vertical zinc oxide (ZnO) tiny pillars (red) embedded in lanthanum strontium manganite film matrix (yellow). (Image: Chris Sheehan, Center for Integrated Nanotechnologies, Los Alamos National Laboratory)
In the designer composites, electrical conductivity can be controlled by both an applied magnetic field and temperature. The team’s work highlights a new approach to control conductivity in these thin films. Such materials might revolutionize the design of memory devices.
Can we build novel memory devices to do data reading and writing at terahertz frequencies so that our personal devices can operate at a much higher speed?
A team of researchers from the Center for Integrated Nanotechnologies and universities in the United Kingdom found a colossal magnetoresistance at terahertz frequencies at room temperature in high-quality functional nanocomposites. The terahertz conductivity of nanocomposites can be controlled by both an applied magnetic field and temperature.
For example, in the presence of an external field (for example, 2 terahertz), the terahertz conductivity changes over two orders of magnitude.
These findings demonstrated a new approach of utilizing optic pulses at terahertz frequencies to probe magnetoresistance, which can revolutionize the design of future memory devices. Different from conventional colossal magnetoresistance observed at high magnetic fields and low temperatures, this newly developed colossal magnetoresistance at terahertz frequencies can be seen at room temperature and intermediate magnetic fields.
The team studied the underlying physical mechanisms with terahertz time-domain magnetospectroscopy. Researchers can use the results to guide the future development of novel functional thin films with better performance. The experiments show that colossal magnetoresistance at terahertz frequencies may be used in extremely small electronics and in terahertz optical components controlled by magnetic fields.
The research suggests the promise of this material system for future terahertz optical and electronic components, such as magnetically driven modulators.
Source: U.S. Department of Energy, Office of Science
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Filme adezive antimicrobiene inovatoare pentru reducerea riscului de infecție în spitale(Innovative antimicrobial adhesive films to reduce infection risk in hospitals)

Aceste filme de plastic antimicrobiene vor fi utilizate în spitale pentru a reduce riscul de infecție. În acest sens, obiectivul principal al FLEXPOL este acela ca materialul să fie utilizat pe suprafețe mari, cum ar fi pereții și podelele, precum și pe cele mai mici, cum ar fi mesele, paturile sau ușile, unde cresc tot mai multe bacterii. Din acest motiv, produsul va fi testat în medii medicale actuale, și anume la Spitalul Universitar Donostia, partener de proiect, pentru a evalua cât de eficiente, durabile și rezistente la infecții sunt aceste filme, precum și compatibilitatea acestora cu protocoalele de curățare și dezinfectare loc.

Posted: Feb 09, 2018

Innovative antimicrobial adhesive films to reduce infection risk in hospitals

(Nanowerk News) In Europe each year, over 500,000 people get infected in hospitals, in unsterilised transit areas such as toilets, corridors or rooms. The University of Alicante Research Group in Polymer and Nanomaterial Analysis (NANOBIOPOL), together with research and industry staff from Italy, Spain, Portugal, the UK and Germany, is involved in the FLEXPOL project to make an antimicrobial adhesive film reducing infection risk in hospitals.
In hospitals, patients, visitors and staff are at high risk of fatal bacterial infections. FLEXPOL, funded by the European Commission, is intended to develop a pilot line for cost-effectively producing these transparent, antimicrobial, polypropylene-based films.
To that end, two factors are essential: nanostructures on the plastic surface and capsules containing a mixture of oils with antimicrobial properties. The surface structure, combined with the material, can kill several types of germs and inhibit bacterial growth with a 99% effectiveness rate. Specifically, the structures employed cause mechanical damage to cell membranes, thus killing pathogens.
This strategy will guarantee patients and medical staff’s health protection and bring considerable economic benefits, as spending on detergents and disinfectants will be reduced. A promising solution requiring various steps and contributions from the ten project partners.
In this sense, the researchers from the University of Alicante’s NANOBIOPOL group, Alfonso Jiménez, María del Carmen Garrigós and Carlos Pelegrín, are designing formulations with antimicrobial properties from essential oils extracted from plants such as thyme or oregano, for use as bactericidal agents. According to Jiménez, “our main role is to develop the polypropylene film with the antimicrobial essential oils in the laboratory. These oils are extracted from natural plants such as thyme or rosemary, which can be found near Alicante and are integrated in the basic material of the film”.

Applications
These antimicrobial plastic films will be used in hospitals to reduce infection risk. In this regard, FLEXPOL’s main goal is for the material to be used on large surfaces, such as walls and floors, as well as on smaller ones, like tables, beds or doorknobs, where more and more bacteria grow. For this reason, the product will be tested in actual medical environments, namely at Donostia University Hospital, a project partner, to evaluate how effective, durable and infection-resistant these films are, as well as their compatibility with the cleaning and disinfection protocols in place.

FLEXPOL meeting at the UA
On 23 and 24 January 2018, the UA San Vicente del Raspeig campus hosted a meeting of the FLEXPOL project consortium, formed by Germany’s Fraunhofer Institute for Production Technology (IPT), project coordinator; Naturality, Propagroup S.p.A. and Granta Design Ltd. (a Spanish, an Italian and a British company, respectively); two research centres, IK4-TENIKER and the Catalan Institute for Nanoscience and Nanotechnology (ICN2); the Universities of Alicante and Minho, Portugal; and Donostia University Hospital.
The FLEXPOL project, launched in January 2017, will be running for three years and is set to receive €5.17 million of funding from the European Union.
Source: Asociación RUVID

Cristale de divizare pentru conductivitatea metalică 2D(Splitting crystals for 2D metallic conductivity)

Materialele sunt fabricate din atomi de stronțiu, niobiu și oxigen, cu o structură stratificată derivată din perovskit. Acești compuși ai niobatului de stronțiu promite dezvoltarea electronică avansată datorită conductivității metalice cvasi-dimensionale.

Posted: Feb 21, 2018

Splitting crystals for 2D metallic conductivity

(Nanowerk News) Adding oxygen atoms to a perovskite-like crystal material splits it into layers, giving it unique electrical properties.
Sheets of electrons that are highly mobile in only two dimensions, known as 2D electron gas, have unique properties that can be leveraged for faster and novel electronic devices. Researchers have been exploring 2D electron gas, which was only discovered in 2004, to see how it can be used in superconductors, actuators, and electronic memory devices, among others.
Researchers at Japan’s Tohoku University, with an international team of colleagues, recently identified the atomic structure of a group of perovskite-related materials showing interesting 2D conductive properties.
atomic structure alternately arranged in the three-layer and the zig-zag two-layer thick chain-like slabs
The scanning transmission electron micrograph shows that the atomic structure was alternately arranged in the three-layer and the zig-zag two-layer thick chain-like slabs, showing quasi-1D metallic conductivity in the former.
The materials are made of strontium, niobium and oxygen atoms, with a layered structure derived from perovskite. These strontium niobate compounds show promise for developing advanced electronics because of their ‘quasi-one-dimensional’ metallic conductivity.
Yuichi Ikuhara of Tohoku University’s Advanced Institute for Materials Research with Johannes Georg Bednorz of Zürich Research Laboratory and colleagues used atom-resolved scanning transmission electron microscopy combined with theoretical calculations to learn how adding oxygen atoms to strontium niobates affects their conductivity. Four different materials formed depending on the concentration of oxygen atoms.
The researchers found that three of the materials were conductors of electricity while the fourth was an insulator. At the atomic scale, they discovered the materials were formed of alternating chain-like and zigzag slabs. Depending on the concentration of oxygen atoms, the chain-like slabs were two, three, or four layers thick, sometimes varying within the same material. The zigzag slabs were insulating layers in all the materials, while the chain-like slabs were conducting layers in three of the four materials.
The team determined that local electrical conductivity within the material directly depended on the shapes of the niobate octahedra in the layers. When positive ions of niobium were displaced toward the centers of the niobate octahedra, a local conducting nature was induced.
2D conducting layers are commonly formed by creating an interface between two insulators. It should now be possible to achieve the same goal by segmenting 3D conducting materials into stacks of 2D conducting layers separated by insulating layers, the researchers say in their study published in the journal ACS Nano, („Atomic-Scale Origin of the Quasi-One-Dimensional Metallic Conductivity in Strontium Niobates with Perovskite-Related Layered Structures”). This could lead to applications in the development of 2D electrical conducting materials and devices.
Source: Tohoku University

Experimentele de precizie relevă lacune în teoria lui van der Waals(Precision experiments reveal gaps in van der Waals theory)

Descoperirea grafenului, cu raportul său ridicat de rezistență la greutate, flexibilitate, conductivitate electrică și capacitatea de a forma o barieră impenetrabilă, a condus la o explozie de interes în solidele 2D. TiS 2 este un material arhetipal van der Waals, cu straturi care conțin foi de titan și sulf care interacționează prin legături chimice puternice, unde electronii sunt împărțiți între atomi, rezultând o structură relativ fixă. Între aceste foi, interacțiunile S … S van der Waals atrage straturile unul către altul, permițându-le să se dezvolte, formând materiale solide

Posted: Feb 16, 2018

Precision experiments reveal gaps in van der Waals theory

(Nanowerk News) The discovery of graphene, with its high strength-to-weight ratio, flexibility, electrical conductivity, and ability to form an impenetrable barrier, led to an explosion of interest in 2D solids. Weak, long-range interactions give 2D solids some of their most interesting behaviors; therefore, understanding these interactions is crucial for further developing these materials. However, experimental support for theoretical modelling of the van der Waals interactions that hold these materials’ layers together has been wanting.
Now, an international research group led by the University of Tsukuba and Aarhus University has performed synchrotron X-ray diffraction experiments on titanium disulfide (TiS2)—a transition metal dichalogenide (TMD) material with a layered 2D structure—and compared the results with theoretical calculations. Their benchmark work was recently published in Nature Materials („X-ray electron density investigation of chemical bonding in van der Waals materials”).
Precision experiments reveal gaps in van der Waals theory
“The interaction between layers in van der Waals materials such as TiS2 has a significant bearing on their modification, processing, and assembly,” study co-author Eiji Nishibori says. “By modelling experimental synchrotron data and comparing it with density functional theory calculations, we revealed surprising information about the nature of the electron sharing between layers in these materials.”
TiS2 is an archetypal van der Waals material, with layers comprising sheets of titanium and sulfur interacting through strong chemical bonds, where electrons are shared between atoms, resulting in a relatively fixed structure. Between these sheets, long-range S…S van der Waals interactions attract the layers to one another allowing them to build up, forming solid materials. These interactions are known to be much weaker than those within the 2D sheets, however, using high-energy synchrotron X-ray radiation to precisely measure a single TiS2 crystal, the researchers were able to show that the interlayer interactions are in fact stronger than theory indicates, and involve significant electron sharing.
“This work provides a fundamental understanding of an exciting class of materials with numerous potential applications in technologies such as ion batteries, catalysis, and superconductors,” lead author Hidetaka Kasai says. “Our experiments are the first to reveal the true nature of the interactions that make 2D materials so interesting, and we hope they will underpin many future developments in this area.”
The outstanding agreement of the synchrotron diffraction data with theoretical calculations in describing the intralayer Ti-S interactions, supports the validity of these new-found differences for the long-range interactions across the interlayer gaps. The findings are expected to substantially contribute to the fundamental understanding of weak chemical bonding in 2D layered materials in general, and to the development of TMD materials.
Source: University of Tsukuba

Membranele de grafină fac Sydney Harbor „băutură”(Graphene membranes make Sydney Harbour ‘drinkable’)

De-a lungul timpului, poluanții chimici și pe bază de ulei acoperă și împiedică filtrele de apă, ceea ce înseamnă că contaminanții trebuie îndepărtați înainte ca filtrele să înceapă. Testele au arătat că Graphair a continuat să funcționeze chiar și atunci când este acoperit cu poluanț”În Graphair am găsit un filtru perfect pentru purificarea apei, care poate înlocui procesele complexe, consumatoare de timp și cu mai multe etape, necesare în prezent, cu un singur pas”.
În timp ce grafenul este cel mai puternic material din lume și poate fi doar un singur atom de carbon subțire, acesta este, de obicei, hidrofug.

Posted: Feb 15, 2018

Graphene membranes make Sydney Harbour ‘drinkable’

(Nanowerk News) Using their own specially designed form of graphene, ‘Graphair’, CSIRO scientists have supercharged water purification, making it simpler, more effective and quicker.
The new filtering technique is so effective, water samples from Sydney Harbour were safe to drink after passing through the filter.
The breakthrough research was published today in Nature Communications („Anti-fouling graphene-based membranes for effective water desalination”).
Graphair sample
A Graphair sample. (Image: CSIRO)
„Almost a third of the world’s population, some 2.1 billion people, don’t have clean and safe drinking water,” the paper’s lead author, CSIRO scientist Dr Dong Han Seo said.
„As a result, millions – mostly children – die from diseases associated with inadequate water supply, sanitation and hygiene every year.
„In Graphair we’ve found a perfect filter for water purification. It can replace the complex, time consuming and multi-stage processes currently needed with a single step.”
While graphene is the world’s strongest material and can be just a single carbon atom thin, it is usually water repellent.
Using their Graphair process, CSIRO researchers were able to create a film with microscopic nano-channels that let water pass through, but stop pollutants.
As an added advantage Graphair is simpler, cheaper, faster and more environmentally friendly than graphene to make.
It consists of renewable soybean oil, more commonly found in vegetable oil.
Looking for a challenge, Dr Seo and his colleagues took water samples from Sydney Harbour and ran it through a commercially available water filter, coated with Graphair.
Researchers from QUT, the University of Sydney, UTS, and Victoria University then tested and analysed its water purification qualities.
The breakthrough potentially solves one of the great problems with current water filtering methods: fouling.
Over time chemical and oil based pollutants coat and impede water filters, meaning contaminants have to be removed before filtering can begin. Tests showed Graphair continued to work even when coated with pollutants.
Without Graphair, the membrane’s filtration rate halved in 72 hours.
When the Graphair was added, the membrane filtered even more contaminants (99 per cent removal) faster.
„This technology can create clean drinking water, regardless of how dirty it is, in a single step,” Dr Seo said.
„All that’s needed is heat, our graphene, a membrane filter and a small water pump. We’re hoping to commence field trials in a developing world community next year.”
CSIRO is looking for industry partners to scale up the technology so it can be used to filter a home or even town’s water supply.
It’s also investigating other applications such as the treatment of seawater and industrial effluents.

Gel utilizează nanoparticule pentru controlul la cerere al picăturilor(

Folosind acest procedeu simplu, două lichide nemiscibile au produs prima structură torturoasă, cu totul lichidă, cu canale submicrometrice interconectate (mai îngust decât părul uman) și cu o formă persistentă. Astfel de „bijeli” (emulsie bicomponentă blocată) pot avea avantaje ca materiale pentru cataliză și stocare a energiei, dar dificultățile în producerea lor și reducerea dimensiunii canalului au limitat valoarea lor până în prezent.
Această abordare nanoparticulo-surfactant este mai simplă și a condus la bijeli cu dimensiuni canale reglabile – chiar până la zece ori mai mici decât este posibil în prezent. Poate fi utilizată o gamă largă de chimicale și concentrații lichide, nanoparticule și polimeri.

Posted: Feb 15, 2018

Gel uses nanoparticles for on-demand control of droplet shapes

(Nanowerk News) Until now, producing liquids that can be shaped and reshaped on demand hasn’t been possible. Scientists discovered a simple way to form stabilized droplets in a variety of structures. Tightly packed nanoparticle-polymer assemblies at droplet surfaces were squeezed into desired shapes assemblies with an electric field. This new approach is a simple route to form droplets of one liquid phase in another liquid. This could lead to the continuous production of discrete, responsive, and reconfigurable all-liquid systems.
This is a unique platform for printing liquids into structures such as small tubes or special sponge-like gels with desired channel dimensions. This printing can structure, re-organize, and indefinitely lock-in the spatial arrangement of liquids. The result? The printed liquids can create optimized pathways for the flow of mechanical, electrical, or optical energy through a material. Tuning compression at the surface may lead to advanced—even revolutionary—energy storage and catalyst technologies.
A water droplet with a trapped nanoparticle-surfactant assembly at its surface
Paralleling your favorite oil-based salad dressing, combining nanoparticles and a soap-like material (surfactant) goes one step further—tunable channels are stabilized in the mixture. Left: A water droplet with a trapped, a.k.a. jammed, nanoparticle-surfactant assembly at its surface. Withdrawing the “water-liking” phase caused the single layer of assemblies to compress. The visible wrinkles developed immediately, suggesting a “solid-like” nature of the squeezed assemblies. And, the process is reversible. Right: A confocal fluorescence image shows the bicontinuous structure of the nanoparticle-surfactant mixtures. (Image: Lawrence Berkeley National Laboratory)
Biological cells compartmentalize the functions of proteins and enzymes within organelles and organize into tissues that coordinate to perform work. Trapping, a.k.a. jamming, nanoparticles at water droplet surfaces offers unparalleled routes to similarly compartmentalize human-made matter resulting in the assembly of structured liquids.
Scientists at Lawrence Berkeley National Laboratory have demonstrated that two liquids that do not mix (called immiscible) can be shaped on demand into stable non-spherical structures. The key is tightly packed nanoparticle surfactants (soap-like materials) at droplet surfaces that are squeezed by an electric field.
A water droplet containing nanoparticles decorated with negatively charged functional groups was first created. The water droplet was in an oil containing polymers with complementary positively charged groups at one end. This allowed the opposite charges to form assemblies at the water-oil interface. An electric field was applied across the droplet, deforming it into an elongated shape with increased surface area.
This allowed more assemblies to form at the droplet surface. Upon removal of the electric field, the droplet attempted to revert to a lower surface area shape (sphere). However, the assemblies were compressed and jammed at the interface. This caused the shape of the liquid to be fixed, “arresting” the liquid in an otherwise highly unstable shape.
Suppressing the instability enables development of a continuous process for forming highly uniform droplets with a wide range of shapes. Moreover, droplet configuration can be controllably changed. Subsequent application of a force such as an electric or magnetic field can cause the droplet to deform. The jammed assemble becomes fluid. This allows its spatial organization to be reconfigured and a new droplet shape to form after removal of the field.
Using this simple process, two immiscible liquids produced the first torturous, all-liquid structure with interconnected sub-micrometer (narrower than a human hair) channels and a persistent shape. Such “bijels” (bicontinuous jammed emulsion) may have advantages as materials for catalysis and energy storage, but difficulties in producing them and reducing the size of their channel have limited their value to date.
This nanoparticle-surfactant approach is simpler and led to bijels with tunable channel sizes—even down to ten times lower than currently possible. A wide range of liquid, nanoparticle, and polymer chemistries and concentrations can be used.
These findings provide valuable guidance for the selection of functionalized nanoparticles and polymers to tune the droplet assembly process to generate structured liquids in a predictable manner.

Publications
A. Toor, B. Helms, and T.P. Russell, “Effect of nanoparticle surfactants on the breakup of free-falling water jets during continuous processing of reconfigurable structured liquid droplets.External link” Nano Letters 17, 3119 (2017). [DOI: 10.1021/acs.nanolett.7b00556]
C. Huang, J. Forth, W. Wang, K. Hong, G. Smith, B.A. Helms, and T.P. Russell, “Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactantsExternal link.” Nature Nanotechnology 12, 1060 (2017). [DOI: 10.1038/nnano.2017.182]

 

Compania trei: noul aliaj stabilește indicatorul de magnetism(Three’s company: New alloy sets magnetism benchmark)

anunță săptămâna aceasta că au construit un film subțire stabil din fier, cobalt și mangan, care se mândrește cu literele fizice aplicate ( „momente mari în filmul subțire al aliajului FexCoyMnz din aliajele ternare” ) un moment atomic mediu cu 50% mai mare decât limita Slater-Pauling. Realizată printr-o tehnică cunoscută sub denumirea de epitaxie cu fascicule moleculare (MBE), aliajul cubic (bcc) centrat pe corp ternar prezintă o densitate de magnetizare de 3,25 magnetoni Bohr pe atom, depășind maximul considerat anterior de 2,45.

Posted: Feb 13, 2018

Three’s company: New alloy sets magnetism benchmark

(Nanowerk News) The burgeoning field of spintronics leverages electron spins – as opposed to their charge – to enhance solid-state devices like hard drives and cell phone components by prolonging battery life. Spintronic developments, however, are increasingly running up against a barrier known as the Slater-Pauling limit, the maximum for how tightly a material can pack its magnetization. Now, a new thin film is poised to break through this decades-old benchmark.
A team of researchers from Montana State University and Lawrence Berkeley National Laboratory announces this week in Applied Physics Letters („Large moments in bcc FexCoyMnz ternary alloy thin films”), that they constructed a stable thin film made from iron, cobalt and manganese that boasts an average atomic moment potentially 50 percent greater than the Slater-Pauling limit. Made with a technique known as molecular beam epitaxy (MBE), the ternary body-centered cubic (bcc) alloy features a magnetization density of 3.25 Bohr magnetons per atom, besting the previously considered maximum of 2.45.
„What we have is a potential breakthrough in one of the most important parameters of magnetic materials,” said Yves Idzerda, an author on the paper from Montana State University. „Large magnetic moments are like the strength of steel – the bigger the better.”
The Slater-Pauling curve describes magnetization density for alloys. For decades, iron-cobalt (FeCo) binary alloys have reigned supreme, posting a maximum average atomic moment of 2.45 Bohr magnetons per atom and defining the current limit for stable alloy magnetization density. Previously, researchers mixed FeCo alloys with high-magnetic-moment transition metals, like manganese. When these ternary alloys are made, however, they lose much of their bcc structure, a key component to their high magnetism.
Instead, this team turned to MBE, a meticulous technique akin to draping a substrate with beads of individual metal atoms, one layer at a time, to create a 10-20 nanometer film of Fe9Co62Mn29. Roughly 60 percent of the available compositions kept the bcc structure as a thin film, compared to only 25 percent in bulk.
To better understand the alloy’s composition and structure, the group used X-ray absorption spectroscopy and reflection high-energy-electron diffraction. The X-ray magnetic circular dichroism results showed that the new material yielded an average atomic moment of 3.25 Bohr magnetons per atom. When tested with a more standard vibrating sample magnetometry, even though this magnetization density dropped, it was still significantly above the Slater-Pauling limit – 2.72.
Idzerda said this discrepancy will provide areas of future research, adding that the interface between manganese and the substrate within the crystal might account for the gap.
„I have guarded optimism for this because the technique we used is a little bit nonstandard and we have to convince the community of this material’s performance,” Idzerda said.
Idzerda and his team will now investigate the robustness of iron-cobalt-manganese alloys, and more efficient fabrication techniques. They also plan to explore how molecular beam epitaxy might lead to other highly magnetic thin films, potentially mixing together four or more transition metals.
Source: American Institute of Physics