Lună: iunie 2018

Oamenii de știință dezvoltă materiale care ar putea regenera emailul dentar(Scientists develop material that could regenerate dental enamel)

Cercetatorii de la Universitatea Queen Mary din Londra au dezvoltat un nou mod de a dezvolta materiale mineralizate care ar putea regenera tesuturile tari, cum ar fi smaltul si osul dentar.Materialele ar putea fi utilizate pentru o mare varietate de complicații dentare, cum ar fi prevenirea și tratamentul cariilor dentare sau sensibilității la dinți – cunoscută și sub numele de hipersensibilitate la dentină.

Posted: Jun 01, 2018

Scientists develop material that could regenerate dental enamel

(Nanowerk News) Researchers at Queen Mary University of London have developed a new way to grow mineralised materials which could regenerate hard tissues such as dental enamel and bone.
Enamel, located on the outer part of our teeth, is the hardest tissue in the body and enables our teeth to function for a large part of our lifetime despite biting forces, exposure to acidic foods and drinks and extreme temperatures. This remarkable performance results from its highly organised structure.
However, unlike other tissues of the body, enamel cannot regenerate once it is lost, which can lead to pain and tooth loss. These problems affect more than 50 per cent of the world’s population and so finding ways to recreate enamel has long been a major need in dentistry.
The study, published in Nature Communications („Protein disorder–order interplay to guide the growth of hierarchical mineralized structures”), shows that this new approach can create materials with remarkable precision and order that look and behave like dental enamel.
Close-up of enamel-like material
Close-up of the enamel-like material. (Image: Alvaro Mata)
The materials could be used for a wide variety of dental complications such as the prevention and treatment of tooth decay or tooth sensitivity – also known as dentin hypersensitivity.
Dr Sherif Elsharkawy, a dentist and first author of the study from Queen Mary’s School of Engineering and Materials Science, said: „This is exciting because the simplicity and versatility of the mineralisation platform opens up opportunities to treat and regenerate dental tissues. For example, we could develop acid resistant bandages that can infiltrate, mineralise, and shield exposed dentinal tubules of human teeth for the treatment of dentin hypersensitivity.”
The mechanism that has been developed is based on a specific protein material that is able to trigger and guide the growth of apatite nanocrystals at multiple scales – similarly to how these crystals grow when dental enamel develops in our body. This structural organisation is critical for the outstanding physical properties exhibited by natural dental enamel.
Lead author Professor Alvaro Mata, from Queen Mary’s School of Engineering and Materials Science, said: „A major goal in materials science is to learn from nature to develop useful materials based on the precise control of molecular building-blocks. The key discovery has been the possibility to exploit disordered proteins to control and guide the process of mineralisation at multiple scales. Through this, we have developed a technique to easily grow synthetic materials that emulate such hierarchically organised architecture over large areas and with the capacity to tune their properties.”
Enabling control of the mineralisation process opens the possibility to create materials with properties that mimic different hard tissues beyond enamel such as bone and dentin. As such, the work has the potential to be used in a variety of applications in regenerative medicine. In addition, the study also provides insights into the role of protein disorder in human physiology and pathology.
Source: Queen Mary University of London

Puzzle cu graphene foto excitat rezolvat(Photoexcited graphene puzzle solved)

Folosirea grafenului ca material sensibil la lumină pentru detectoarele de lumină poate oferi îmbunătățiri semnificative în ceea ce privește materialele folosite în zilele noastre.
De exemplu, grafenul poate detecta lumina de aproape orice culoare și dă un răspuns electronic extrem de rapid, într-o singură milionime dintr-o milionă de secundă. Astfel, pentru a proiecta corect detectorii de lumină pe bază de grafen, este esențial să înțelegem procesele care au loc în interiorul grafenului după ce absoarbe lumina.

Posted: Jun 01, 2018

Photoexcited graphene puzzle solved

(Nanowerk News) Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for light detectors can offer significant improvements with respect to materials being used nowadays.
For example, graphene can detect light of almost any color, and it gives an extremely fast electronic response within one millionth of a millionth of a second. Thus, in order to properly design graphene-based light detectors it is crucial to understand the processes that take place inside the graphene after it absorbs light.
The Mainz-based researchers Dr. Hai Wang, Professor Dmitry Turchinovich, Professor Mathias Kläui, and Professor Mischa Bonn, in collaboration with scientists from various European labs, have now succeeded in understanding these processes. The project was led by Dr. Klaas-Jan Tielrooij from ICFO in Spain, who was recently elected visiting professor at the Materials Science in Mainz (MAINZ) Graduate School of Excellence.
ultrafast optical pump
Schematic representation of the ultrafast optical pump – terahertz probe experiment, where the optical pump induces electron heating and the terahertz pulse is sensitive to the conductivity of graphene directly after this heating process. (Image: Fabien Vialla)
Published recently in Science Advances („The ultrafast dynamics and conductivity of photoexcited graphene at different Fermi energies”), their work gives a thorough explanation of why the graphene conductivity in some cases increases after light absorption while it decreases in others.
The researchers were able to show that this behavior correlates with the way in which the energy from the absorbed light flows to the graphene electrons: After light is absorbed by the graphene, the processes through which graphene electrons heat up happen extremely fast and with a very high efficiency.
For highly doped graphene with many free electrons present, ultrafast electron heating leads to carriers with elevated energy, so-called hot carriers. This, in turn, leads to a decrease in conductivity. Interestingly enough, for weakly doped graphene with less free electrons, electron heating leads to the creation of additional free electrons and, thus, an increase in conductivity. These additional carriers are the direct result of the gapless nature of graphene. In gapped materials, electron heating does not lead to additional free carriers.
This simple scenario of light-induced electron heating in graphene can explain many observed effects. Aside from describing the conductive properties of the material after light absorption, it can explain carrier multiplication, where under specific conditions one absorbed light particle, i.e., a photon, can indirectly generate more than one additional free electron and thus create an efficient photo response within a device.
The results of the paper and, in particular, understanding electron heating processes accurately, will definitely mean a great boost in the design and development of graphene-based light detection technology.
Source: Johannes Gutenberg University Mainz

Elon Musk spune că nanotehnologia este „BS” – iată cum schimbă deja lumea(Elon Musk says nanotechnology is ‘BS’ – here’s how it’s already changing the world)

Nu poți să spui nanotech fără să creezi grafen. A fost numit un material de minune datorită rezistenței sale, conductivității și elasticității. Făcată din matrice bidimensionale de atomi de carbon aranjate într-un model de tip fagure, foile de grafen se pot întinde doar cu câteva atomi, dar cu o suprafață totală mai aproape de dimensiunea unui poster.
Când este amestecat cu rășini și materiale plastice, materialul rezultat va fi incredibil de puternic și ușor. Materialele compozite pe bază de grafen sunt deja utilizate pentru o gamă largă de aplicații, inclusiv echipamente sportive și panouri de caroserie. Între timp, proprietățile electrice ale grafenului înseamnă că pot îmbunătăți și tehnologiile bateriei.

Posted: Jun 01, 2018

Elon Musk says nanotechnology is ‘BS’ – here’s how it’s already changing the world

(Nanowerk News) You might expect Elon Musk, the business magnate, engineer and serial entrepreneur would be a fan of all things techy. After all, his radical enterprises are built on pushing science to its limit. He’s behind a raft of visionary projects ranging from Tesla’s driverless electric cars and SpaceX’s self-landing reusable rockets to plans for 1,000kph “hyperloop” trains. But it appears there is a size limit to Musk’s technophilia. He recently tweeted that he thinks nanotechnology is “BS”.
So is nanotech just a buzzword used to jazz up some otherwise dull research? Or is it a real branch of scientific discovery that’s actually making a difference to the world?
Nano means small, really small. One nanometre is just one billionth of metre. At this scale we’re dealing with individual molecules and atoms (a carbon atom is about 0.3 nanometres across). So nanotech is about arranging matter that’s between one nanometre and 100 nanometres across in at least one dimension, to create usable medicines, electronics and materials.
The idea of deliberately doing science and engineering at this scale may well have started back in 1959, with a talk entitled There’s Plenty of Room at the Bottom by the great physicist Richard Feynman. But, in fact, people in ancient times used nanotechnology to create stunning works of art, without realising the scales at which they were manipulating matter.

Quantum dots
Today we’ve purposefully harnessed nanotechnology to do some incredible things. Take quantum dots. They may sound like the name of a Belgian indie band but, in fact, these real and incredibly versatile nanomaterials are being used in medical imaging, display technologies and photovoltaic solar cells.
A quantum dot is a particle of semiconducting material just a few nanometres in diameter. Due to their miniscule size, they have electronic properties that sit between what you would expect for a single molecule and a larger bulk material. One of the most useful outcomes of this is that the dots fluoresce (glow) with a colour that depends on the size of the particle. This means that by tweaking the size of the dot you can tune the colours they give off. And that property makes them an ideal candidate for use in your next flat screen TV.

Nanobiotechnology
Nature has a jump on us when it comes to nanotech. The protein molecules that replicate your DNA, digest your food and fight off infections are all nano-sized machines perfectly evolved to do a specific job in your bodies. This makes them ideal places to look for inspiration when trying to engineer something on the nanoscale.
A great example of this in action is a technique known as nanopore DNA sequencing. This technology involves proteins called porins that are normally used by bacteria to allow materials to enter and leave the cells. The porins are placed in a membrane to create channels or pores through it, and an electrical field is then applied. When DNA is forced through the pores the electrical current changes in response to the part of the DNA molecule (the base) that is in the pore.
By measuring the current as the molecule passes through the pore you can work out what the bases that comprise it are and sequence the DNA. This can be done at breakneck speed – up to 450 bases a second – using a tiny desktop device.

Graphene
You can’t mention nanotech without graphene cropping up. It’s been dubbed a wonder material due to its strength, conductivity and elasticity. Made up of two-dimensional arrays of carbon atoms arranged in a honeycomb pattern, graphene sheets can be just a few atoms thick but with a total area nearer the size of a poster.
When mixed with resins and plastics, the resulting material will be incredibly strong and lightweight. Graphene-based composite materials are already being used for a range of applications including sporting equipment and vehicle body panels. Meanwhile graphene’s electrical properties mean it can also enhance battery technologies.
Doesn’t that sound like something an electric car manufacturer might want to look into?
Source: By Mark Lorch, Professor of Science Communication and Chemistry, University of Hull

Izolatori noi cu muchii de conducere(Novel insulators with conducting edges)

Clasa nouă de materiale: Izolatori topologici de înaltă calitate;o nouă clasă de izolatori topologici care au proprietăți de conducere pe marginea cristalelor, mai degrabă decât pe suprafața lor;Cercetatorii spera ca in viitor nanofirele fabricate din izolatii topologice de ordin superior pot fi folosite ca trasee de conducere in circuitele electrice. Acestea ar putea fi combinate cu materiale magnetice și superconductoare și utilizate pentru construirea calculatoarelor cuantice.

Posted: Jun 01, 2018

Novel insulators with conducting edges

(Nanowerk News) Topology examines the properties of objects and solids that are protected against perturbations and deformations. Materials known so far include topological insulators, which are crystals that insulate on the inside but conduct electrical current on their surface. The conducting surfaces are topologically protected, which means that they cannot easily be brought into an insulating state.

New class of materials: Higher-order topological insulators
Theoretical physicists at the University of Zurich have now predicted a new class of topological insulators that have conducting properties on the edges of crystals rather than on their surface.
The research team, made up of scientists from UZH, Princeton University, the Donostia International Physics Center and the Max Planck Institute of Microstructure Physics in Halle, dubbed the new material class „higher-order topological insulators” (Science Advances, „Higher-order topological insulators”).
This is a schematic of a higher-order topological insulator in the shape of a nanowire, with conducting channels on its edges.
This is a schematic of a higher-order topological insulator in the shape of a nanowire, with conducting channels on its edges. (Image: University of Zurich)
The extraordinary robustness of the conducting edges makes them particularly interesting: The current of topological electrons cannot be stopped by disorder or impurities. If an imperfection gets in the way of the current, it simply flows around the impurity.

Like a highway for electrons
In addition, the crystal edges do not have to be specially prepared to conduct electrical current. If the crystal breaks, the new edges automatically also conduct current.
„The most exciting aspect is that electricity can at least in theory be conducted without any dissipation,” says Titus Neupert, professor at the Department of Physics at UZH. „You could think of the crystal edges as a kind of highway for electrons. They can’t simply make a U-turn.”
This property of dissipationless conductance, otherwise known from superconductors at low temperatures, is not shared with the previously known topological insulator crystals that have conducting surfaces, but is specific to the higher-order topological crystals.

Further theoretical and experimental research needed
The physicists’ study still mostly relies on theoretical aspects. They have proposed tin telluride as the first compound to show these novel properties. „More material candidates have to be identified and probed in experiments,” says Neupert.
The researchers hope that in the future nanowires made of higher-order topological insulators may be used as conducting paths in electric circuits. They could be combined with magnetic and superconducting materials and used for building quantum computers.
Source: University of Zurich