Lună: februarie 2018

Nus Defions Arsenal Democracy Blackside personalizat fabrică Glock 19/17 (G19 / 17) 9mm Combat (Nous Defions Arsenal Democracy Blackside Customized Factory Glock 19/17 (G19/17) 9mm Combat/Tactical Pistol Frames, AD Type 1 and Type 2 Glock Pistol Magwells)

În plus față de pistoalele de tip „Blackside Glock” de tipul „Blackside 19” („Mayhem Carry”) personalizate Glock 19 (G19) tip pistol de luptă / tactil de tip 9mm, AD personalizează pistoalele din gama Glock pentru clienți. Ele pot personaliza și optimiza diferite părți ale acestuia a la carte, cum ar fi rama, diapozitivul, butoaia etc. În special, pot să contureze / să contureze și să contureze cadrele și diapozitivele, să adauge AD Triggerul Blackside SWiTCH și / sau țintă = dreapta> Wolff Gunsprings și tijă de ghidare și tampon de nitruri negre, furnizați un magwell AD Blackside Type 1 și Type 2 și adăugați extensii magice AD ​​/ personalizate / texturi (+3 și +5 plăcuțe de bază pentru reviste) și altele .

Nous Defions Arsenal Democracy Blackside Customized Factory Glock 19/17 (G19/17) 9mm Combat/Tactical Pistol Frames, AD Type 1 and Type 2 Glock Pistol Magwells, and AD/Hyve Technologies Mag (Magazine) Extensions (Extended Magazine Base Pads)! 

Posted by: David Crane February 13, 2018

In addition to full-custom Nous Defions Arsenal Democracy (AD) Blackside Glock-type pistols like the AD Blackside 19MC (Mayhem Carry) custom Glock 19 (G19)-type 9mm combat/tactical pistol, AD still customizes Glock factory pistols for customers. They can customize and optimize various parts of it a la carte, like the frame, slide, barrel, etc. Most notably, they can stipple/texturize and contour the frames and slides, add their terrific AD Blackside SWiTCH Triggerand/or target=right>Wolff Gunsprings and black-nitrided guide rod and buffer, provide an AD Blackside Type 1 and Type 2 extended/flared magwell and add AD-customized/texturized Hyve Technologies mag extensions (+3 and +5 magazine base pads), and more.

In DefenseReview’s (DR) video below, you can see all of these mods on Gen-4 G19 frames and mags (magazines). Notice the chamfered groove on the front of the AD Blackside Glock magwells for easier and faster mag insertion during speed reloads, as well as the brass plug on the back/rear of the magwell that adds a little weight to the butt for enhanced balance and shootability during fast shooting strings, mitigating a little bit of felt recoil. Based on AD president/CEO Dave Pavlick’s explanation of the development and advantages of the AD Type-2 G19 magwell, it would be DR’s preferred G19 magwell over the Type 1.

The AD Blackside Type 2 Magwell sports a tailhook that acts as a ramp for mag insertion during speed reloads. Combined with the front groove, fast mag insertion’s a breeze while speed reloading. According to Pavlick, military operators who’ve used the AD Type 2 G19 magwell also like the feel of the tailhook’s flare against the heal of their palm.

DR also digs the AD Blackside customized Hyve Technologies +3 and +5 magazine base plates/mag extensions. The AD +3 mag extension fits flush with the AD Type-2 magwell, for a very streamlined look and feel. And, both AD mag extensions are Berry-compliant, with all high-quality US-made/sourced parts (including the screws) from companies like McMaster-Carr.

Check out Defense Review’s video to get more details on all the potential custom mods. If you’ve got a Glock pistol you’d like customized and optimized, DR highly recommends Nous Defions Arsenal Democracy’s services. All of their mods are designed to help you shoot better, and improve your weapons handling.

 

 

 

 

Company Contact Info:

Nous Defions Arsenal Democracy (AD)
48 Commerce Lane, STE 7
Freeport, FL, 32439
Phone: 850-499-4375
Customer Service Email: [email protected]
Orders Email: [email protected]
Website: https://www.arsenaldemocracy.us/
Arsenal Democracy Facebook Fan Page: https://www.facebook.com/arsenaldemocracy?fref=ts

W. C. Wolff Company (Wolff Gunsprings)
P.O.Box 458
Newtown Square, PA 19073-0458
Orders and Tech Support: 800-545-0077
Main Phone: 610-359-9600
Fax: 610-359-9496
Customer Service Email: [email protected]
Tech Support Email: [email protected]
Website: https://www.gunsprings.com

Hyve Technologies
4905 Morena Blvd
Suite 1309
San Diego, CA 92117
Phone: 858-270-1987
Email: [email protected]
Website: https://hyvetechnologiesbuilder.com

McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs, CA 90670-2932
Sales Phone: 562-692-5911
Customer Service Phone: 562-641-2800
Fax: 562-695-2323
Email Sales: [email protected]
Website: https://www.mcmaster.com

Camera nouă va identifica IED-urile pentru soldați(New Camera Will Identify IEDs For Soldiers)

Soldații în situații de luptă trebuie să-și scaneze în permanență împrejurimile pentru dispozitivele explozive improvizate (IED), o armă de semnătură a războiului modern de gherilă

New Camera

Pătură de cauciuc la un nivel atomic(Rubber blanket at an atomic level)

Materialele bidimensionale, cum ar fi grafenul, care constau doar din unul sau mai multe straturi atomice, au fost un aspect foarte promițător al științei materialelor în ultimii ani. Acestea demonstrează proprietăți remarcabile care deschid posibilități tehnice complet noi, de la tehnologia senzorilor la celulele solare.
Cu toate acestea, există un fenomen important care nu a putut fi măsurat cu exactitate până în prezent: stresul și presiunea internă extremă pe care pot fi supuse astfel de materiale, care modifică adesea drastic proprietățile fizice ale materialului.

Posted: Feb 12, 2018

Rubber blanket at an atomic level

(Nanowerk News) Two-dimensional materials such as graphene, which consist of only one or a few atomic layers, have been a very promising aspect of materials science over recent years. They demonstrate remarkable properties that open up completely new technical possibilities, from sensor technology to solar cells.
However, there is one important phenomenon that could not be measured accurately up until now: the extreme internal stresses and strains that such materials may be subjected to, which often drastically alter the material’s physical properties. TU Wien has now successfully measured these distortions in 2D materials at microscopic level, which means it is now possible to observe precisely (point for point) how the properties of a material may be altered as a result of a simple distortion. These new measurement methods have now been published in the specialist journal Nature Communications („Optical imaging of strain in two-dimensional crystals”).
measuring distortions in 2D materials
The basic idea of the measurement method: red light hits the surface – blue light is sent back. (Image: TU Vienna)

Stretching and compression
When a material is stretched or compressed, the distance between the individual atoms changes, and this distance has an influence on the electronic properties of the material. This phenomenon has been used in semiconductor technology for years: silicon crystals, for example, can be grown so that they are permanently under internal mechanical stress.
However, two-dimensional materials, which consist only of an ultra-thin layer, offer much greater potential: „A crystal can be stretched by perhaps one percent before it breaks. With 2D materials, deformation of ten or twenty percent is possible”, says Prof. Thomas Müller from the Photonics Institute (Faculty of Electrical Engineering and Information Technology) at TU Wien. Depending on the deformation and mechanical stresses present within the material, the electronic properties may completely change, such as the ability of the electrons to absorb incoming light.
„Up until now, if you wanted to measure stresses present in this type of material you had to rely on extremely complicated measurement methods”, explains Lukas Mennel (TU Wien), lead author of the publication. For example, you could observe the surface using a transmission electron microscope, measure the average distance between the atoms and then deduce any stretching or compression from that. At TU Wien, this process has now been made much simpler and more accurate.

Red light in, blue light out
Here, a remarkable effect called frequency doubling is used: „If you irradiate specific materials – in our case a layer of molybdenum disulphide – with a suitable laser beam, the material may reflect back light of a different colour”, explains Thomas Müller. Two photons in the incoming laser beam are combined to form one photon with double the energy, which is emitted from the material.
However, the intensity of this effect depends on the internal symmetry of the material. Usually, molybdenum disulphide has a honeycomb-like structure, i.e. hexagonal symmetry. If the material is stretched or compressed, this symmetry is slightly distorted – and this small distortion has a dramatic effect on the intensity of the light reflected back from the material.
If you place a layer of molybdenum disulphide over a microstructure, like putting a rubber blanket over a climbing frame, the result is a complex pattern of local distortions. You can now use a laser to scan the material point for point and thus obtain a detailed map of these stretches and compressions. „In doing so, not only can we measure the severity of these deformations, but we can also see the exact direction in which they run”, explains Lukas Mennel.
These imaging methods can now be used for the local, targeted adjustment of material properties. „For example, custom material deformations in solar cells could ensure that free charge carriers are diffused away in the right direction as quickly as possible”, says Thomas Müller. This research on 2D materials means that a new, powerful tool is now available.
Source: Vienna University of Technology

Cercetătorii au inventat nanoantenele emise de lumină bazate pe perovskite de halogenuri(Researchers invented light-emitting nanoantennas based on halide perovskites)

au dezvoltat noi surse de lumină eficiente nanometrice bazate pe perovskitul halogenurilor. Nanosursele considerate sunt nanoparticule cu lungime subwave, care servesc atât ca emițători, cât și ca nanoantenne și permit intensificarea emisiilor de lumină în mod inerent, fără dispozitive suplimentare. Mai mult decât atât, perovskitul permite reglarea spectrelor de emisie într-un interval vizibil prin modificarea compoziției materialului. Acest lucru face ca noile nanoparticule să fie o platformă promițătoare pentru crearea de dispozitive optoelectronice compacte, cum ar fi chips-uri optice, diode emițătoare de lumină sau senzori.

Posted: Feb 12, 2018

Researchers invented light-emitting nanoantennas based on halide perovskites

(Nanowerk News) Young scientists from ITMO University developed new effective nanoscale light sources based on halide perovskite. The considered nanosources are subwavelength nanoparticles, which serve both as emitters and nanoantennas and allow enhancing light emission inherently without additional devices. Moreover, perovskite enables tuning emission spectra throughout a visible range by varying the composition of the material. This makes the new nanoparticles a promising platform for creating compact optoelectronic devices such as optical chips, light-emitting diodes, or sensors. The results were published in Nano Letters („Light-Emitting Halide Perovskite Nanoantennas”).
light-emitting nanoantennas based on halide perovskites
The nanoscale light sources and nanoantennas have already found a wide range of applications in several areas, such as ultra compact pixels, optical detection, or telecommunications. However, the fabrication of nanostructure-based devices is rather complicated due to the limited luminescence efficiency of the materials used typically as well as non-directional and relatively weak light emission of single quantum dots or molecules. An even more challenging task is placing a nanoscale light source precisely near a nanoantenna.
A research group from ITMO University managed to combine a nanoantenna and a light source in a single nanoparticle. It can generate, enhance and route emission via excited resonant modes coupled with excitons. „We used hybrid perovskite as a material for such nanoantennas,” says Ekaterina Tiguntseva, the first author of the publication. “Unique features of perovskite enabled us to make nanoantennas from this material. We basically synthesized perovskite films, and then transferred material particles from the film surface to another substrate by means of pulsed laser ablation technique. Compared to alternatives, our method is relatively simple and cost-effective.”
While studying the obtained perovskite nanoparticles, the scientists discovered that their emission can be enhanced if its spectra match with the Mie-resonant mode. „Such resonances were named in honor of Gustav Mie, an outstanding German scientist,” explains George Zograf, Engineer at the Laboratory of Hybrid Nanophotonics and Optoelectronics at ITMO University. “He developed a general theory describing how the light interacts with sphere-like objects smaller than the wavelength. Currently, scientists are particularly interested in Mie-resonances related to dielectric and semiconductor nanoparticles. Perovskites used in our work are also semiconductors with luminescence efficiency much higher than that of many other materials. Our study shows that combination of excitons with the Mie resonance in perovskite nanoparticles makes them efficient light sources at room temperature.”
In addition, the radiation spectrum of the nanoparticles can be changed by varying the anions in the composition of the material. „The structure of the material remains the same, we simply use another component in the synthesis of perovskite films. Therefore, it is not necessary to adjust the method each time. It remains the same, yet the emission color of our nanoparticles changes,” says Ekaterina.
„As far as we know, no one could get subwavelength perovskite nanoantennas with an adjustable emission spectrum before,” adds George. “When we submitted this paper our senior colleagues jokingly demanded that we bake some pastry reflecting the concept of our work in case the article is accepted. As a result, we celebrated the publication of the work with cupcakes in the colors of our nanoparticles’ emission. We adopted this nice tradition from a research group led by Prof. Jeremey Baumberg at the University of Cambridge.”
The scientists are currently continuing the research of light-emitting perovskite nanoantennas using various components for their synthesis. In addition, they are developing new designs of perovskite nanostructures which may improve ultra compact optical and transmission devices.
Source: ITMO University

Compozit-piezoelectric de cea mai înaltă calitate de astăzi(Today’s highest quality composite-piezoelectric)

au reușit să dezvolte un material compozit care are astăzi cele mai bune proprietăți piezoelectrice.Piezoelectrica este unul dintre cele mai uimitoare materiale din lume.Materialele compozite bazate pe polimeri și feroelectrice clasice, care au proprietăți piezo- și piroelectrice, au un număr de avantaje în comparație cu ceramica pură: densitatea, capacitatea de a produce părți de orice dimensiune și formă, elasticitatea mecanică, stabilitatea proprietăților electrofizice și simplitatea și costul relativ scăzut al producției. În plus, compozitul sintetizat sa dovedit a fi excelent la presiuni ridicate, ceea ce îl face o bază excelentă pentru senzori de presiune „.

Posted: Feb 12, 2018

Today’s highest quality composite-piezoelectric

(Nanowerk News) NUST MISIS scientists jointly with an international group of scientists have managed to develop a composite material that has the best piezoelectric properties today. The research results were published in Scientific Reports („Evolution of poled state in P(VDF-TrFE)/(Pb,Ba)(Zr,Ti)O3 composites probed by temperature dependent Piezoresponse and Kelvin Probe Force Microscopy”).
Piezoelectrics are one of the world`s most amazing materials. It is possible to literally squeeze electricity from them. That is, an electric charge appears at the time of the material`s compression (or stretching). This is called the piezoelectric effect. Piezoelectric materials can be applied in many fields – from pressure sensors and sensitive elements of a microphone to the controller ink pressing in ink-jet printers and quartz resonators.
Composite-Piezoelectric
Topography (a), PFM images of a pristine state (b) and after poling by +/ 60V (c). (Image: NUST MISIS)
Lead zirconate titanate is one of the most popular piezoelectric materials. However, it has several disadvantages: it is heavy and inflexible. Additionally, lead production often causes great harm to the environment. That is why scientists are constantly looking for new materials with low lead content as well as with less weight and greater flexibility. In particular, the creation of flexible piezoelectric materials (while maintaining the key properties) would greatly expand piezoelectric materials` possibilities both as acoustic membrane and as pressure sensors.
An international team of scientists from the University of Duisburg-Essen (Germany), NUST MISIS, National Research Tomsk State University and the National Research University of Electronic Technology, working with the financial support of the Russian Science Foundation (grant 16-19-10112), has managed to create such a material and analyze its properties. For this, the nanoparticles consisting of titanate-zicronate barium-lead were placed in a complex polymer consisting of vinylidene disluoride and trifluoroethylene. By diversifying the composition of the components, scientists were able to get the most ideal composite.
„The Russian-German group of scientists, including Dmitri Kiselev, a Senior Researcher at the NUST MISIS R&D Center for Materials Science & Metallurgy, has managed to create a composite material based on ceramics and organic polymer whose properties exceed today`s best piezoelectric materials. The research’s experimental part was carried out with an atomic-force microscope in the University of Duisburg-Essen (Germany). Thanks to this scientific collaboration, Dmitri Kiselev has gained skills from the world`s best scanning probe microscope, which he can later apply at NUST MISIS”, said Alevtina Chernikova, Rector of NUST MISIS.
According to Dmitri Kiselev, the developed material has a very distinct field of application due to its polymer component: „Composite materials based on polymer and classic ferroelectrics, which have piezo- and pyroelectric properties, have a number of advantages compared to pure ceramics: low density, the ability to manufacture parts of any size and shape, mechanical elasticity, stability of electrophysical properties, and the simplicity and relatively low cost of production. Additionally, the synthesized composite has proved to be excellent at high pressures which makes it an excellent base for pressure sensors”.
According to Kiselev, to study the composite they had to modify the standard technique which allowed them to correctly visualize the nanoparticles of ceramics in the volume of the polymer matrix: „In order to capture the electrical signal more clearly, we heated our sample in a certain way from room temperature to 60 degrees Celsius. It allowed us to measure the material’s characteristics very qualitatively and reproducibly. Our method will greatly simplify the work of our colleagues in the study of composites, so I hope that it will be in demand among our colleagues microscopists”.
Source: National University of Science and Technology MISIS

Noi materiale pentru forțele viitoare(New Wearables For Future Forces)

Un sistem numit Arielle combină elemente precum casca de înaltă tehnologie și armura corpului, printre alte articole de îmbrăcăminte, care pot regla temperatura corpului forțelor de luptă de mâine în timp real – ceea ce reprezintă un avantaj pentru forțele în climatul tropical înfundat

New

Putine straturi de telur ca succesor promitator al fosforului negru(Few-layer tellurium as a promising successor of black phosphorus)

Acest material reușește majoritatea proprietăților izbitoare ale BP și, în plus, oferă o stabilitate mai bună a mediului, un cost de fabricație mult mai mic (cu metode de chimie umedă) și o absorbție mai puternică a luminii decât cele ale BP. În acest scenariu, FL-α-Te ar putea fi considerat un succesor superior al BP.

Posted: Feb 09, 2018

Few-layer tellurium as a promising successor of black phosphorus

(Nanowerk News) Two-dimensional (2D) layered materials have received considerable attention because of their potential applications in various fields since the experimental discovery of graphene.
Two-dimensional elementary semiconductors are particularly desired owing to their superior features in terms of fabrication, purification and doping.
Few-layer black phosphorus (BP) is the first 2D mono-elementary semiconductor showing high electronic carrier mobility, strong optical absorption, linear dichroism, promising figure of merit and high tunability with external fields. All the properties immediately put few-layer BP under spotlights since its discovery in 2014.
However, the flawed air-stability and difficulties in largescale fabrication were found to be two remaining issues that obscure practical applications of few-layer BP in the industry. People thus get started to question if a promising or even superior successor of BP exists. The target semiconductor is preferably an elementary one. It should also allow low-cost and large-scale synthesis and offer good environmental stability without sacrificing those striking properties offered by BP.
Professor Wei Ji has led a research group at Renmin University of China to theoretically model surfaces and interfaces of emerging electronic materials and to predict physical properties of devices comprised of these materials.
Recently, they collaborated with Prof. Yang Chai from the Hong Kong Polytechnic University to report a theoretical study of a novel chain-like 2D-material, namely few-layer α-Tellurium (FL-α-Te), and predicted this material to have extremely high carrier mobility with a layer-tunable bandgap, strong light absorption, mixing of vibrational modes, layer-dependent energy maps of valence and conduction bands and among other striking properties („Few-layer Tellurium: one-dimensional-like layered elementary semiconductor with striking physical properties”).
few-layer alpha-Tellurium
A chain-like two-dimensional material, few-layer alpha-Tellurium, has intrinsically geometric anisotropy, anisotropic inter-chain (-layer) vibrational behaviors, higher mobility along the non-covalent bonding direction and isotropic light absorption, as governed by the found covalent-like quasi-bonding for the inter-chain (-layer) interactions. (© Science China Press) (click on image to enlarge)
The FL-α-Te is a representative material of layered one-dimensional materials, which are a novel and fast developing category of 2D-materials. They first examined the stability of three likely few-layer phases using state-of-the-art density functional theory calculations.
Their calculation shows α-Tellurium is the most stable phase for bilayer and thicker layers. Given the stability unveiled, they found that a covalent-like quasi-bonding (CLQB) dominates the inter-chain interaction in both intra- and inter-layer directions. This CLQB is in analogy to the found interlayer interactions in BP, PtS2 or PtSe2, in which it shows wavefunction hybridization but does not provide extra energy gain.
They managed to correlate this bonding with the layer-dependent geometric and electronic structures and their resulting behaviors in terms of electric, optical, and vibrational properties.
Few-layer α-Te has extremely high hole-mobility up 105 cm2/Vs exceptionally along the non-covalent-bound (CLQB) direction and 103 cm2/Vs for the covalent-bound direction, tunable bandgap from 0.31 eV (Bulk) to 1.17 eV (2L), anisotropic inter-chain (-layer) vibrational behaviors, a crossover of interlayer shear and breathing force constants, large ideal strength (over 20%) and nearly isotropic strong light absorption (up to 9% per layer) from a highly anisotropic geometry.
They also found, specifically in few-layer α-Te, that the energy surfaces of both valence and conduction bands substantially develop from bulk to bilayer, exhibiting an „M-like” line profile of the hole pocket, which was usually found in topological insulators and is ideal for thermoelectrics.
This material succeeds most of the striking properties of BP and additionally offers a better environmental stability, a much lower fabrication cost (with wet-chemistry methods) and a stronger light absorption than those of BP. In this scenario, FL-α-Te could be regarded as a superior successor of BP.
The extraordinarily high carrier mobility revealed in the CLQB direction conceptually updates the understanding of the role of non-covalent interactions in carrier mobility and may open a new avenue for seeking high carrier mobility materials.
Source: Science China Press

Aplicat în nanoparticule deformate în apă și aplicația sa pentru moartea celulelor induse de fotografie(Water-soluble warped nanographene and its application for photo-induced cell death)

Nanographene are grila hexagonală de carbon din grafen, dar constă doar din câteva inele de carbon cu proprietăți electronice reglabile. Una dintre problemele sale majore care împiedică aplicarea pe scară largă a dispozitivelor optoelectronice sau a biomedicinei este insolubilitatea sa. Prin urmare, pentru a suprima stivuirea și agregarea, s-a sintetizat un nou tip de nanograf cu o structură îndoită, așa-numitul nanographene deformat.

Posted: Feb 09, 2018

Water-soluble warped nanographene and its application for photo-induced cell death

(Nanowerk News) Graphene and its nano-sized little sibling, nanographene, are well known for their remarkable photoelectronic properties. However, biomedical applications are hampered by the insolubility of the materials, especially in water.
A Japanese team of scientists has now introduced substituted “warped nanographene,” which is soluble in a broad range of solvents while maintaining its photophysical properties. In their publication in Angewandte Chemie („A Water-Soluble Warped Nanographene: Synthesis and Applications for Photoinduced Cell Death”), the authors also emphasize its photodynamic potential to selectively kill cells upon irradiation.
Water-Soluble Warped Nanographene
Water-Soluble Warped Nanographene – Synthesis of a water-soluble warped nanographene and its application for photo-induced cell death. (© Wiley-VCH)
Nanographene has the hexagonal carbon lattice of graphene but consists of only a few carbon rings with tunable electronic properties. One of its big issues hampering widespread application in optoelectronic devices or biomedicine is its insolubility. Therefore, to suppress stacking and aggregation, a new type of nanographene with a bended structure has been synthesized, the so-called warped nanographene.
Kenichiro Itami at Nagoya University, Japan, and his colleagues have now found a way to furnish the warped nanographene even further to obtain a fully soluble, amphiphilic product. The new structure was biocompatible, but upon irradiation it killed its host cell. This effective photosensitization behavior could inspire future research in photodynamic cancer therapy, the authors believe.
The poor solubility of graphene-like materials has been regarded problematic since the discovery of graphene as an intriguing one-layer carbon modification in 2004. To improve solubility, Itami and his colleagues have developed warped nanographene molecules with chemical substituents at the outer rim of the aromatic structure.
The substituents were introduced by the relatively simple and powerful strategy of borylation. Once the molecule is borylated, the boron substituent can be replaced by other substituents, in this case, by an aromatic molecule bearing highly soluble tetra(ethylene glycol) chains (TEG).
Applying this substitution–replacement strategy twice, the scientists accomplished the synthesis of a warped, i.e., bended, nanographene molecule that was stable in a broad range of solvents including water. Excited with a laser, it exhibited green fluorescence.
This fluorescence points to applications in biology, for example, as a dye in bioimaging. A further application came rather unexpected, the scientists reported. Upon excitation, the molecule, which was otherwise not harmful to the cells, killed the cell population of the human HeLa cell line to almost 100 percent.
The authors proposed: “Although the mechanism is unclear, the relatively high efficiency of the singlet oxygen generation of [the soluble warped nanographene] may contribute to its HeLa cell death.” Thus, a mechanism similar to dye sensitization and production of reactive oxygen species can be assumed.
These second-generation nanographenes combine the remarkable optoelectronic properties of graphene with biocompatibility. They may well play a future role in bioimaging, photodynamic therapy, and similar applications.
Source: Wiley

Stivuirea pe grafen(Stacking on the graphene)

Cercetătorii din Japonia au găsit o modalitate de a forma două materiale, fiecare realizat din trei straturi de grafen. Ghepena fiecărui material este stivuită diferit și are proprietăți electrice unice. Munca lor are implicații pentru dezvoltarea unor noi dispozitive electronice, cum ar fi senzorii foto care convertesc lumina în energie electrică.

Posted: Feb 09, 2018

Stacking on the graphene

(Nanowerk News) Researchers in Japan have found a way to form two materials, each made of three layers of graphene. Each material’s graphene is stacked differently and has unique electrical properties. Their work has implications for the development of novel electronic devices, such as photo sensors that convert light into electrical energy.
In 2004, two scientists realized they had isolated a single layer of carbon atoms on a scotch tape used to clean a graphite crystal. Since then, graphene has captured the imagination of researchers due to its fascinating properties: it is 200 times stronger than steel, is very flexible, and it is an excellent conductor of electricity.
Graphene’s carbon atoms are arranged into hexagons, forming a honeycomb-like lattice. Placing one layer of graphene on top of another leads to the formation of bilayer graphene. The layers can be arranged in one of two positions: the centres of the carbon hexagons of each layer can be organized immediately above one another, called AA-stacking, or they can be displaced forwards so that a hexagon centre in one layer is above a carbon atom below it, called AB-stacking. AB-stacking of two layers of graphene leads to the formation of a material with semiconducting properties by applying an external electric field.
The schematic crystal structures of (a) ABA- and (b) ABC- stacked three layer graphene
The schematic crystal structures of (a) ABA- and (b) ABC- stacked three layer graphene. (Image: Katsuaki Sugawara)
Deliberately stacking three layers of graphene has proven difficult. But doing so could help researchers study how the physical properties of tri-layered materials change based on how the layers are stacked. This could lead to the development of novel electrical devices.
Researchers at Japan’s Tohoku University and Nagoya University have now fabricated two different types of trilayer graphene with different electrical properties.
They heated silicon carbide using one of two methods. In one experiment, silicon carbide was heated to 1,510°C under pressurized argon. In another, it was heated to 1,300°C in a high vacuum. Both materials were then sprayed with hydrogen gas in which the bonds were broken to form single hydrogen atoms. Two types of trilayer graphene then formed. The silicon carbide heated under pressurized argon formed into ABA-stacked graphene, in which the hexagons of the top and bottom layers were exactly aligned while the middle layer was slightly displaced. The silicon carbide heated in a vacuum developed into ABC-stacked graphene, in which each layer was slightly displaced in front of the one below it.
The researchers then examined the physical properties of each material and found that their electrons behaved differently.
The ABA graphene was an excellent electrical conductor, similar to monolayer grapheme. The ABC grapheme, on the other hand, acts more like AB graphene in that it had semi-conductor properties.
„The present success in selective fabrication of ABA and ABC trilayer graphene would widen the feasibility of graphene-based nano-electronic devices with variable layer numbers and stacking sequences,” conclude the researchers in their study published in the journal NPG Asia Materials(„Selective fabrication of free-standing ABA and ABC trilayer graphene with/without Dirac-cone energy bands”).
Source: Tohoku University

Metasuprafețele permit o performanță îmbunătățită a obiectivelor optice(Metasurfaces enable improved optical lens performance)

Obiectivele lentile apochromatice – cele care focalizează în mod corespunzător cele trei culori roșu, albastru și verde – care au o curbură mai mică și sunt mai subțiri și mai ușoare ar putea îmbunătăți camerele telefonului mobil și permit fabricarea de telefoane celulare mai subțiri. De asemenea, acestea ar putea face camere mai ușoare, mai bune pentru corp, camere pentru cască, zone de lunetist, dispozitive de imagistică termică și vehicule aeriene fără pilot sau dronuri. În esență, orice lucru care folosește lentile pentru imagine poate fi simplificat și mai ușor.

Posted: Feb 09, 2018

Metasurfaces enable improved optical lens performance

(Nanowerk News) Producing the perfect color images we need and love often requires multiple, heavy lenses so that each color focuses in exactly the same plane. Now Penn State engineers have developed a new theory that solves the problem using a single thin lens comprised of gradient index materials and metasurface layers to properly direct the light.
„If we want high performance optical systems, then we have to overcome material dispersion,” said Sawyer D. Campbell, assistant research professor in electrical engineering. „If we don’t, we get smeary colors, which significantly degrades image quality.”
Single apochromatic lenses – ones that properly focus the three colors red, blue and green – that have less curvature and are thinner and lighter could improve cell phone cameras and allow manufacture of thinner cell phones. They also could make lighter, better body cameras, helmet cameras, sniper scopes, thermal imaging devices and unmanned aerial vehicles or drones. In essence, anything that uses lenses to image could be made simpler and lighter.
„Usually there are several lenses, but that increases the weight,” said Jogender Nagar, graduate student in electrical engineering. „Our aim is to improve SWaP – reduce size and weight while increasing performance.”
The researchers thought to combine two technologies: that of gradient-index (GRIN) lens, and metasurfaces – ultra-thin optical layers with sub-wavelength features that manipulate the wavefront in a desired manner. The researchers report the results of their work in the current issue of Optica („Multi-element, multi-frequency lens transformations enabled by optical wavefront matching”).
focussing light through lenses
Traditional glass lenses (a) focus different colors to different points resulting in color separation and image blurring. In contrast, newly developed metasurface-augmented gradient-index lenses (b) correct for color separation by focusing blue, green, and red light to the same point. (Image: Jogender Nagar, Penn State)
„Our system uses one lens,” said Nagar. „We use the curvature of the lens, the distribution of materials in the lens, and a metasurface – a pattern placed on the surface – to make the lens thinner, lighter, but still focus properly.”
Most lenses use curvature to control the focal point, but three separate conventional lenses are needed to focus the three separate colors to one focal point and produce a high quality image. By spatially varying the material composition inside the lens, one GRIN lens can perfectly focus two colors. Then, by adding a metasurface to the GRIN lens, one layered lens can perfectly focus all three colors and do the work of three conventional lenses.
„The gradient in the lens can be axial – varying along the direction of light propagation, or optical axis; or radial – varying outwardly from the optical axis,” said Douglas H. Werner, John L. and Genevieve H. McCain Chair Professor in electrical engineering. „Or it could be more complex.”
The researchers developed a theoretical model and simulation framework for creating these lenses.
„We had to use some advanced tools that were specially developed in the lab,” said Werner. „Tools for modeling, simulation and optimization that we created for solving such a challenging design problem.”
The theoretical model specifies the proper surface curvature and gradient in the GRIN lens and the proper patterning for the metasurface to satisfy the requirements of perfect focusing of all three colors. The model optimizes both the lens and the metasurface to work together.
„The theory is very general and covers a wide range of conditions,” said Werner. „Fabrication will be the challenge initially. We hope development of the theory will steer the fabrication, making it possible to produce such lenses at a low cost and high volume.”
Source: Penn State