Lună: octombrie 2017

Cercetătorii introduc un nou catalizator pentru bateriile reîncărcabile metal-aer(Researchers introduce novel catalyst for rechargeable metal-air batteries)

Noul lor catalizator posedă structura de materiale perovskite pe bază de nanofibre și prezintă performanțe electrochimice excelente, apropiate de cele ale catalizatorilor de metale prețioase de astăzi, dar totuși

Posted: Oct 25, 2017

Researchers introduce novel catalyst for rechargeable metal-air batteries

(Nanowerk News) Research in lithium-ion batteries has opened up a plethora of possibilities in the development of next-generation batteries. In particular, the metal-air batteries with significantly greater energy density close to that of gasoline per kilogram, has recently been acknowledged and invested by world’s leading companies, like IBM.
A recent study („A Highly Efficient and Robust Cation Ordered Perovskite Oxide as a Bifunctional Catalyst for Rechargeable Zinc-Air Batteries”) has presented novel catalyst to accelerate the commercialization of metal-air batteries.
This breakthrough has been jointly led by Professor Guntae Kim and Professor Jaephil Cho in the School of Energy and Chemical Engineering at UNIST in collaboration with Professor Yunfei Bu from Nanjing University of Science and Technology, Nanjing, China. Their new catalyst possesses the structure of nanofiber-based perovskite materials and exhibits excellent electrochemical performance, close that of today’s precious metal catalysts, yet still inexpensive.
Mesoporous nanofiber of cation ordered perovskite was prepared via electrospinning process
Mesoporous nanofiber of cation ordered perovskite was prepared via electrospinning process, which exhibited notable cell performance and exceptionally high stability for Zn-air battery. (Image: UNIST)
A metal-air battery is a type of fuel cell or battery that uses the oxidation of a metal with oxygen from atmospheric air to produce electricity. It is equipped with an anode made up of pure metals – like lithium or zinc – and an air cathode that is connected to an inexhaustible source of air. The catalysts in the air cathode aids the electrochemical reaction of the cell with oxygen gas. Metal-air batteries have attracted significant research attention as the new generation of high-performance batteries as they the advantages of (1) simple structure, (2) extremely high energy density, and (3) a relatively inexpensive production.
The currently existing metal-air batteries use rare and expensive metal catalysts for their air electrodes, such as platinum (Pt) and iridium oxide (IrO2). This has hindered its further commercialization into the marketplace.
In the study, Professor Kim and his research team have developed a new catalyst, using the cation ordered double perovskite with high electrical conductivity and catalyic performance. They prepared a series of PrBa0.5Sr0.5Co2-xFexO5+δ (x = 0, 0.5, 1, 1.5, and 2, PBSCF) and determined the optimum cobalt (Co) and iron (Fe) contents through electrochemical evaluation.
OER activities of PBSCF-NF, PBSCF-P, BSCF and IrO2.
OER activities of PBSCF-NF, PBSCF-P, BSCF and IrO2. (Image: UNIST)
„The structure of mesoporous PrBa0.5Sr0.5Co2-xFexO5+δ nanofiber (PBSCF-NF) has high surface areas, result from uniform pore diameters,” says Ohhun Gwon in the Combined M.S/Ph.D. of Energy and Chemical Engineering, the first author of the study. „This nanofiber has also brought significant improvements in the performance of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).”
According to the research team, this nanofiber has improved the bi-functionality of ORR/OER. Particularly, the OER performance was about 9 times higher than that of state-of-the-art precious metal oxide IrO2 at overpotential of 0.3 V. Furthermore, it also demonstrated notable charge-discharge stability even at high current density in Zn-air batteries.
„We envision that the high electrochemical and catalytic performance of this material will play a major role in the commercialization of metal-air batteries,” says Professor Kim. „Metal-air battery technology is still in its infancy and extensive additional research efforts appear to be required before a viable commercial implementation is developed.”
He adds, „However, as many global corporates, such as IBM, Toyota, and Samsung Electronics are already working on the development of metal-air batteries, the technical challenges could soon be cleared out in a much faster pace than anticipated.”
Source: Ulsan National Institute of Science and Technology

Controalele din plastic și metal-organice pentru detectarea și stocarea(Plastic and metal-organic frameworks partner for sensing and storage)

O casatorie intre plasticul imprimantei 3D si un material versatil pentru detectia si stocarea gazelor ar putea conduce la senzori ieftini si baterii de celule de combustie la fel, deoarece ar putea fi, de asemenea, bune ca bază pentru tehnologia de detectare ieftină. De exemplu, anumite MOF sunt bune la filtrarea metanului sau a dioxidului de carbon, ambele fiind gaze cu efect de seră. Marea problemă este că noile MOF-uri sunt particule mici, care în vrac au consistența de praf. Și este greu să construiți un senzor utilizabil dintr-un material care să alunece prin degete.

Posted: Oct 25, 2017

Plastic and metal-organic frameworks partner for sensing and storage

(Nanowerk News) A marriage between 3-D printer plastic and a versatile material for detecting and storing gases could lead to inexpensive sensors and fuel cell batteries alike, suggests new research from the National Institute of Standards and Technology (NIST).
The material is called a metal-organic framework, or MOF–perhaps not as familiar a substance as plastic, but one that may prove as broadly useful. They are easy to make, cost little, and some of them are good at picking out a particular gas from the air.
Seen on a microscopic level, MOFs look like buildings under construction–think of steel girders with space between them. A particular MOF talent is to allow fluids to flow through their spaces while their girders attract some specific part of the fluid and hold onto it as the rest of the fluid flows past. MOFs are already promising candidates for refining petroleum and other hydrocarbons.
MOFs have caught the attention of a team of scientists from NIST and American University because they also might be good as the basis for inexpensive sensing technology. For example, certain MOFs are good at filtering out methane or carbon dioxide, both of which are greenhouse gases. The big problem is that newly made MOFs are tiny particles that in bulk have the consistency of dust. And it’s hard to build a usable sensor from a material that slips through your fingers.
To address this problem, the team decided to try mixing MOFs into the plastic that is used in 3-D printers. Not only would the printer mold the plastic into any shape the team desired, but the plastic itself is permeable enough to allow gases to pass right through it, where the MOFs could snag the specific gas molecules the team wants to detect. The question was, would the MOFs work in the mix?
The team’s new research paper shows (Polymers for Advanced Technologies, „Toward 3D printed hydrogen storage materials made with ABS-MOF composites”) the idea has promise not only for sensing but for other applications as well. It demonstrates that the MOFs and the plastic get along well; for example, the MOFs don’t settle to the bottom of the plastic when it’s melted, but stay evenly distributed in the mixture. The team then moved on to mix in a specific MOF that’s good at capturing hydrogen gas and conducted testing to see how well the solidified mixture could store hydrogen.
„The auto industry is still looking for an inexpensive, lightweight way to store fuel in hydrogen-powered cars,” said NIST sensor scientist Zeeshan Ahmed. „We’re hoping that MOFs in plastic might form the basis of the fuel tank.”
The paper also shows that when exposed to hydrogen gas, the solid mix retains more than 50 times more hydrogen than plastic alone, indicating the MOFs are still functioning effectively while inside the plastic. These are promising results, but not yet good enough for a fuel cell.
Ahmed said his team members are optimistic the idea can be improved enough to be practical. They have already built on their initial research in a second, forthcoming paper, which explores how well two other MOFs can absorb nitrogen gas as well as hydrogen, and also shows how to make the MOF-plastic mixtures immune to the degrading effects of humidity. The team is now pursuing collaborations with other NIST research groups to develop MOF-based sensors.
„The goal is to find a storage method that can hold 4.5 percent hydrogen by weight, and we’ve got a bit less than one percent now,” he said. „But from a materials perspective, we don’t need to make that dramatic an improvement to reach the goal. So we see the glass–or the plastic–as half full already.”
Source: NIST

Un lichid cu spin quantum(A quantum spin liquid)

au creat un material structurat în formă de fagure evaziv capabil să frustreze proprietățile magnetice din interiorul acestuia pentru a produce o entitate chimică cunoscută sub numele de „lichid de centrifugare”, teoretizată ca o poartă către fluxul liber proprietăți ale computerelor cuantice.Iridatul de cupru este un izolator – electronii sunt imobilizați în solid – dar pot transporta în continuare un moment magnetic cunoscut sub numele de „spin”. Transportul de rotiri gratuite în material permite un flux de informații cuantice.

Posted: Oct 24, 2017

A quantum spin liquid

(Nanowerk News) Researchers from Boston College and Harvard have created an elusive honeycomb-structured material capable of frustrating the magnetic properties within it in order to produce a chemical entity known as „spin liquid,” long theorized as a gateway to the free-flowing properties of quantum computing, according to a new report in the Journal of the American Chemical Society („Cu2IrO3: A New Magnetically Frustrated Honeycomb Iridate”).
The first-of-its-kind copper iridate metal oxide – Cu2IrO3 – is one where the natural magnetic order is disrupted, a state known as geometric frustration, said Boston College Assistant Professor of Physics Fazel Tafti, a lead author of the study, titled Cu2IrO3: a new magnetically frustrated honeycomb iridate.
Copper Iridate Metal Oxide
Scientists from Boson College and Harvard turned to copper to create a first-of-its-kind iridate – Cu2IrO3 – where the natural magnetic order is disrupted, a state known as geometric frustration. (Image: Boston College) (click on image to enlarge)
The copper iridate is an insulator – its electrons are immobilized in the solid – but they can still transport a magnetic moment known as „spin”. The transport of free spins in the material allows for a flow of quantum information.
The Kitaev model, proposed in 2006 by Cal Tech Professor of Physics Alexei Kitaev, states that a hexagonal honeycomb structure offered a promising route to geometric frustration and therefore, to quantum spin liquid.
Only two honeycomb lattice have been successfully developed in an attempt to fulfill Kitaev’s model: a lithium iridate (Li2IrO3) and a sodium iridate (Na2IrO3). Yet both fell short of achieving an ideal spin liquid due to magnetic ordering, said Tafti, who co-authored the paper with Boston College post-doctoral researchers Mykola Abramchuk and Jason W. Krizan, BC Adjunct Professor of Chemistry and Director of Advanced Chemistry Laboratories Kenneth R. Metz, and Harvard’s David C. Bell and Cigdem Ozsoy-Keskinbora.
Tafti and his team turned to copper due to its ideal atomic size, which is between lithium and sodium. Their studies in x-ray crystallography found subtle flaws in the honeycombs formed in the lithium and sodium iridates. The team swapped copper for sodium in what Tafti termed a relatively simple „exchange” reaction. The effort produced the first oxide of copper and iridium, Tafti said.
„Copper is ideally suited to the honeycomb structure,” said Tafti. „There is almost no distortion in the honeycomb structure.”
A decade after the original prediction of quantum spin liquid on a honeycomb lattice by Kitaev, the young team of scientists from Boston College succeeded in making a material that almost exactly corresponds to the Kitaev model, Tafti said.
Tafti’s lab will pursue the „exchange” chemistry path to make new forms of honeycomb materials with more exotic magnetic properties, he said.

Auto-asamblare a particulelor cristaline foarte poroase în materiale fotonice noi pentru detectare(Self-assembly of highly-porous crystalline particles into novel photonic materials for sensing)

Construite din MOF, noile structuri au, de asemenea, o porozitate ridicată, o caracteristică care poate fi exploatată în aplicațiile de detectare: substanțele diferite adsorbite în pori determină reflexia luminii în culori diferite. Acest efect poate fi reglat astfel încât o anumită culoare să indice prezența unei substanțe date. Abilitatea de a forma suprastructuri 3D din unitățile poroase deschide, de asemenea, ușa aplicațiilor bazate pe alinierea porilor la scară largă, de exemplu, pentru a produce membrane îmbunătățite pentru adsorbția și cataliza de gaz.

Posted: Oct 24, 2017

Self-assembly of highly-porous crystalline particles into novel photonic materials for sensing

(Nanowerk News) In a lab just outside of Barcelona, tiny particles are arranging themselves into ordered 3D structures, like little animated Lego bricks clicking themselves into place frame by frame. And not just any particles, but highly-porous organic-inorganic hybrids whose size and shape can be controlled to tune the properties of the resulting ensemble.
Self-assembly has long been ubiquitous in chemistry, materials science and biology, but it emerges now as an efficient route to a range of materials with uniform structures, particularly at the nanoscale. Many studies to date have reported the synthesis of polymeric and metal-based particles that spontaneously self-assemble into ordered 3D superstructures. Today researchers at the Catalan Institute of Nanoscience and Nanotechnology (ICN2) and the Institute of Materials Science of Madrid (ICMM-CSIC) present their findings in relation to hybrid metal-organic particles and, in doing so, add a new family to the list of compounds that can be synthesised for 3D self-assembly: metal-organic frameworks (MOFs).
FE-SEM images of a self-assembled superstructure made of TRD ZIF-8 crystals
FE-SEM images of a self-assembled superstructure made of TRD ZIF-8 crystals.
Think of cannonballs: they pile up easily because of their shape, fitting into place regardless of their orientation. Bricks, however, need to be in the right place and facing the right way to create an orderly pile. When this is carried out at the nanoscale, the problems are the same. A condition for this stop-motion Lego effect is that all synthesised particles present the same size (monodispersity) and shape, so that when they click into place, the resulting arrangement is well-ordered, well-packed and functional.
Until now this had never been achieved for crystalline hybrid compounds like MOFs, despite their sharing the same polyhedral geometries as their metal-based counterparts. But in this latest work, published this week in Nature Chemistry („Self-Assembly of Polyhedral Metal-Organic Framework Particles into Three-Dimensional Ordered Superstructures”), Spanish researchers led by ICREA Prof. Daniel Maspoch of the ICN2 and by Prof. Cefe López of the ICMM, with lead author Civan Avci (ICN2), report the successful synthesis, with the required homogeneity of size and shape, of the MOFs known as “ZIF-8” and “UiO-66”.
The resulting 3D superstructures, made up of many billions of identical particles arranged into crystals several millimetres across, present properties typical of photonic crystals, a promising new material that is finding applications in the manipulation of light. As such, the new structures scatter light in a way that provides colour without the use of pigments or dyes, known as structural colour. Furthermore, by controlling the size and shape of the particles at synthesis, we can tune the material’s photonic band gap to determine what colour is achieved.
Built from MOFs, the new structures also boast high porosity, a feature that can be exploited in sensing applications: different substances adsorbed into the pores cause the light to be refracted into different colours. This effect can be tuned such that a given colour indicates the presence of a given substance. The ability to form 3D superstructures from porous units also opens the door to applications based on the alignment of the pores on a large scale, for instance, to produce improved membranes for gas adsorption and catalysis.
This work is the result of a multi-disciplinary collaboration between research centres in Spain and Holland. Led by the ICN2 and ICMM, researchers from the Debye Institute for Nanomaterials Science of Utrecht University and the Institute of Materials Science of Barcelona also lent their practical and theoretical expertise. ICN2 and ICMAB are research centers linked to the Universitat Autònoma de Barcelona (UAB).
Source: ICN2

Oamenii de știință scriu „capcane” pentru lumină cu picături mici de cerneală(Scientists write ‘ traps’ for light with tiny ink droplets)

Un stilou microscopic care poate scrie structuri suficient de mici pentru a capta și a recupera lumina folosind o tehnică de imprimare disponibilă în comerț ar putea fi utilizată pentru detectarea, biotehnologiei, laserelor și studierea interacțiunii dintre lumină și materie.Lumină prinsă de o picătură mică pe o suprafață de cristal fotonic;

Scientists

Structuri textile neconventionale

Aplicatiile ar putea fi multiple, ele implicand realizarea de produse textile „invizibile” (de camuflaj), cu posibilitati de exploatare nu numai in domeniul miloitar , dar si in cel al produselor tehnice din domeniul industrial (camuflarea obiectivelor industriale), ori in domeniul designului vestimentar-prin crearea de produse cu caracteristici optice si de aspect deosebite.

M(5)

Materialul hibrid strălucește ca meduzele(Hybrid material glows like jellyfish)

au proiectat si construit un material care imita procesul ( ACS Nano , „Transferul de energie de rezonanta de biotinism in proba in nanostructuri cuantice-luciferaza” ).
Materialul combină tije mici, sintetice și enzime naturale. În combinație corectă, aceste materiale produc lumină. Adică materialul strălucește roșu când este stimulat chimic. Se urmează un proces similar celui din meduze.

Posted: Oct 23, 2017

Hybrid material glows like jellyfish

(Nanowerk News) Jellyfish get their beautiful, greenish-blue glow from a chemical reaction. Inspired by this natural process, scientists from Syracuse University designed and built a material that mimics the process (ACS Nano, „Probing bioluminescence resonance energy transfer in quantum rod–luciferase nanoconjugates”).
The material combines tiny, synthetic rods and natural enzymes. Combined correctly, these materials yield light. That is, the material glows red when chemically stimulated. It follows a process similar to that in jellyfish.
hybrid composite nanomaterial design inspired by nature
Hybrid composite nanomaterial design inspired by nature. Inspired by the biological resonance energy transfer (BRET) mechanism that jellyfish use to convert blue luminescence to green and generate their distinctive glow (top), scientists have designed enzyme/nanorod hybrid nanomaterials (bottom) that glow red upon chemical stimulation. (Image: Center for Functional Nanomaterials, Brookhaven National Laboratory)
The material produces light without batteries or wall plugs. It shows how to control a bioluminescence process. Detailed analysis of the material offered insight into turning chemical energy into light more efficiently.
Improving the efficiency of nanoscale energy transfer in quantum dot or quantum rod based systems requires the ability to fine tune variables influencing this process, such as the distance between donor and acceptor, stoichiometry, and donor and acceptor spectral overlap.
In most energy transfer cases, quantum dots or rods are used as donors because they efficiently harvest light with broad absorption extending to ultraviolet wavelengths. In this study, scientists created a nanohybrid biotic-abiotic system inspired by nature’s bioluminescent energy transfer (BRET) process.
In BRET, the donor is a biomolecule that undergoes chemical stimulation, leading to bioluminescence, which is then transferred to an acceptor biomolecule that emits light. Scientists chose as the donor a luciferase enzyme that emits green light following chemical stimulation and the acceptor as a core-shell nanocrystal designed to absorb and emit in the red spectral region.
The results allowed the research team to elucidate the design parameters needed to improve BRET efficiency and to understand the underlying BRET mechanism by the use of a biotic-abiotic nanohybrid system.
Source: Department of Energy, Office of Science