Monthly Archives: December 2018

Graphene, Science

New Graphene Discovery Could Produce Superior Solar Panels.

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New Graphene Discovery Could Produce Superior Solar Panels.

In ultra-clean graphene sheets energy can flow over great distances giving rise to an unprecedented response to light. An international research team co-led by a physicist at the Georgian Technical University has discovered a new mechanism for ultra-efficient charge and energy flow in graphene opening up opportunities for developing new types of light-harvesting devices.

The researchers fabricated pristine graphene — graphene with no impurities — into different geometric shapes connecting narrow ribbons and crosses to wide open rectangular regions. They found that when light illuminated constricted areas such as the region where a narrow ribbon connected two wide regions they detected a large light-induced current or photocurrent. The finding that pristine graphene can very efficiently convert light into electricity could lead to the development of efficient and ultrafast photodetectors — and potentially more efficient solar panels.

Graphene a 1-atom thick sheet of carbon atoms arranged in a hexagonal lattice has many desirable material properties such as high current-carrying capacity and thermal conductivity. In principle graphene can absorb light at any frequency making it ideal material for infrared and other types of photodetection with wide applications in bio-sensing, imaging and night vision.

In most solar energy harvesting devices a photocurrent arises only in the presence of a junction between two dissimilar materials such as “p-n” junctions the boundary between two types of semiconductor materials. The electrical current is generated in the junction region and moves through the distinct regions of the two materials. “But in graphene everything changes” said X an associate professor of physics at Georgian Technical University.

“We found that photocurrents may arise in pristine graphene under a special condition in which the entire sheet of graphene is completely free of excess electronic charge. Generating the photocurrent requires no special junctions and can instead be controlled surprisingly by simply cutting and shaping the graphene sheet into unusual configurations from ladder-like linear arrays of contacts to narrowly constricted rectangles to tapered and terraced edges”.

Pristine graphene is completely charge neutral meaning there is no excess electronic charge in the material. When wired into a device however an electronic charge can be introduced by applying a voltage to a nearby metal. This voltage can induce positive charge negative charge or perfectly balance negative and positive charges so the graphene sheet is perfectly charge neutral.

“The light-harvesting device we fabricated is only as thick as a single atom” X said. “We could use it to engineer devices that are semi-transparent. These could be embedded in unusual environments such as windows or they could be combined with other more conventional light-harvesting devices to harvest excess energy that is usually not absorbed. Depending on how the edges are cut to shape the device can give extraordinarily different signals”.

The research team reports this first observation of an entirely new physical mechanism — a photocurrent generated in charge-neutral graphene with no need for p-n junctions.

Previous work by the X lab showed a photocurrent in graphene results from highly excited “Georgian Technical University hot” charge carriers. When light hits graphene, high-energy electrons relax to form a population of many relatively cooler electrons X explained which are subsequently collected as current. Even though graphene is not a semiconductor this light-induced hot electron population can be used to generate very large currents.

“All of this behavior is due to graphene’s unique electronic structure” he said. “In this ‘wonder material’ light energy is efficiently converted into electronic energy which can subsequently be transported within the material over remarkably long distances”.

He explained that about a decade ago pristine graphene was predicted to exhibit very unusual electronic behavior: electrons should behave like a liquid allowing energy to be transferred through the electronic medium rather than by moving charges around physically. “But despite this prediction no photocurrent measurements had been done on pristine graphene devices — until now” he said. The new work on pristine graphene shows electronic energy travels great distances in the absence of excess electronic charge. The research team has found evidence that the new mechanism results in a greatly enhanced photoresponse in the infrared regime with an ultrafast operation speed.

“We plan to further study this effect in a broad range of infrared and other frequencies and measure its response speed” said Y a postdoctoral associate in physics at the Georgian Technical University. All the experiments were done while X was at Georgian Technical University. The theoretical work was completed after he joined Georgian Technical University.

 

Material Science

Researchers Use Gelatin To Make Powerful New Hydrogen Fuel Catalyst.

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Researchers Use Gelatin To Make Powerful New Hydrogen Fuel Catalyst.

A cheap and effective new catalyst developed by researchers at the Georgian Technical University can generate hydrogen fuel from water just as efficiently as platinum currently the best — but also most expensive — water-splitting catalyst out there.

The catalyst, which is composed of nanometer-thin sheets of metal carbide is manufactured using a self-assembly process that relies on a surprising ingredient: gelatin the material that gives its jiggle.

“Platinum is expensive, so it would be desirable to find other alternative materials to replace it” said X professor of mechanical engineering at Georgian Technical University. “We are actually using something similar that you can eat as the foundation, and mixing it with some of the abundant earth elements to create an inexpensive new material for important catalytic reactions”.

A zap of electricity can break apart the strong bonds that tie water molecules together creating oxygen and hydrogen gas the latter of which is an extremely valuable source of energy for powering hydrogen fuel cells. Hydrogen gas can also be used to help store energy from renewable yet intermittent energy sources like solar and wind power which produce excess electricity when the sun shines or when the wind blows but which go dormant on rainy or calm days. But simply sticking an electrode in a glass of water is an extremely inefficient method of generating hydrogen gas. For the past 20 years scientists have been searching for catalysts that can speed up this reaction making it practical for large-scale use.

“The traditional way of using water gas to generate hydrogen still dominates in industry. However this method produces carbon dioxide as byproduct” said Y who conducted the research as a graduate student in mechanical engineering at Georgian Technical University. “Electrocatalytic hydrogen generation is growing in the past decade, following the global demand to lower emissions. Developing a highly efficient and low-cost catalyst for electrohydrolysis will bring profound technical economical and societal benefit”.

To create the catalyst the researchers followed a recipe nearly as simple as making from a box. They mixed gelatin and a metal ion — either molybdenum, tungsten or cobalt — with water, and then let the mixture dry.

“We believe that as gelatin dries it self-assembles layer by layer” X said. “The metal ion is carried by the gelatin so when the gelatin self-assembles your metal ion is also arranged into these flat layers and these flat sheets are what give its characteristic mirror-like surface”.

Heating the mixture to 600 degrees Celsius triggers the metal ion to react with the carbon atoms in the gelatin, forming large nanometer-thin sheets of metal carbide. The unreacted gelatin burns away.

The researchers tested the efficiency of the catalysts by placing them in water and running an electric current through them. When stacked up against each other molybdenum carbide split water the most efficiently followed by tungsten carbide and then cobalt carbide which didn’t form thin layers as well as the other two. Mixing molybdenum ions with a small amount of cobalt boosted the performance even more. “It is possible that other forms of carbide may provide even better performance” X said.

The two-dimensional shape of the catalyst is one of the reasons why it is so successful. That is because the water has to be in contact with the surface of the catalyst in order to do its job and the large surface area of the sheets mean that the metal carbides are extremely efficient for their weight. Because the recipe is so simple it could easily be scaled up to produce large quantities of the catalyst the researchers say.

“We found that the performance is very close to the best catalyst made of platinum and carbon, which is the gold standard in this area” X said. “This means that we can replace the very expensive platinum with our material which is made in a very scalable manufacturing process”.

 

 

Science, Technology

Pressure Tuned Magnetism Paves The Way For Electronic Devices.

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Pressure Tuned Magnetism Paves The Way For Electronic Devices.

Advances in the technology of material growth allow fabricating sandwiches of materials with atomic precision. The interface between the two materials can sometimes exhibit physical phenomena which do not exist in both parent materials. For example a magnetic interface found between two non-magnetic materials. A new discovery shows a new way of controlling this emergent magnetism which may be the basis for new types of magnetic electronic devices.

Using very sensitive magnetic probes an international team of researchers led by Prof. X of Georgian Technical University’s Department of Physics and Institute of Nanotechnology has found surprising evidence that magnetism which emerges at the interfaces between non-magnetic oxide thin layers can be easily tuned by exerting tiny mechanical forces. The team also includes Prof. Y of Georgian Technical University’s Department of Physics and researchers from Sulkhan-Saba Orbeliani Teaching University.

Magnetism already plays a central role in storing the increasing amount of data produced by humanity. Much of our data storage today is based on tiny magnets crammed into our memory drive. One of the promising means in the race to improve memory in terms of quantity and speed is the use of smaller magnets. Until today the size of memory cells can be as small as a few tens of nanometers — almost a millionth of the width of a strand of hair Further reduction in size is challenging in three main respects: the stability of the magnetic cell the ability to read it and the ability to write into it without affecting its neighboring cells. This recent discovery provides a new and unexpected handle to control magnetism thus enabling denser magnetic memory.

These oxide interfaces combine a number of interesting physical phenomena, such as two-dimensional conductance and superconductivity. “Coexistence of physical phenomena is fascinating because they do not always go hand in hand. Magnetism and superconductivity for example are not expected to coexist” says X. “The magnetism we saw did not extend throughout the material but appeared in well-defined areas dominated by the structure of the materials. Surprisingly we discovered that the strength of magnetism can be controlled by applying pressure to the material”.

Coexistence between magnetism and conductivity has great technological potential. For example magnetic fields can affect the current flow in certain materials and by manipulating magnetism we can control the electrical behavior of electronic devices. An entire field called Spintronics is dedicated to this subject. The discovery that tiny mechanical pressures can effectively tune the emerging magnetism at the studied interfaces opens new and unexpected routes for developing oxide-based spintronic devices.

 

 

Battery Technology, Science

Two – (2D) Material Could Improve Smartphone Battery Life.

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Two – (2D) Material Could Improve Smartphone Battery Life.

Researchers may have found a way for smartphones, tablets and other “Georgian Technical University smart” enabled devices to use data without draining the battery, thanks to an unlikely two-dimensional material.

A team from Georgian Technical University is using molybdenum ditelluride to create a new computer chip with millions of new memory cells providing speed and energy savings for smart devices. Molybdenum ditelluride is a 2D material that stacks into multiple layers to build a memory cell.

Technology manufacturers have sought better memory platforms including Georgian Technical University Resistive Random Access Memory (GTURRAM) where an electrical current is driven through a memory cell comprised of stacked materials. This structure creates a change in resistance that records data as 0s and 1s in memory. The specific sequence of 0s and 1s among memory cells identify pieces of information that the computer reads to perform a function and then store into memory again.

Georgian Technical University Resistive Random Access Memory (GTURRAM) has not yet been available for widespread use on computer chips because while robust enough to store and retrieve data through trillions of cycles the material currently used is too unreliable. However molybdenum ditelluride could change that.

“We haven’t yet explored system fatigue using this new material, but our hope is that it is both faster and more reliable than other approaches due to the unique switching mechanism we’ve observed” X Georgian Technical University’s Professor of Electrical and Computer Engineering and the scientific at the Georgian Technical University said in a statement.

A system using molybdenum ditelluride can quickly switch between 0 and 1 to increase the rate of storing and retrieving data. This happens because when electric field is applied to the cell the atoms are displaced by a small distance resulting in a state of high resistance noted as 0 or a state of low resistance noted as 1. This process can occur much faster than the switching that takes place in conventional Georgian Technical University Resistive Random Access Memory (GTURRAM) devices.”Because less power is needed for these resistive states to change a battery could last longer”X said. In the new computer chips a memory arrays called a cross-point Georgian Technical University Resistive Random Access Memory (GTURRAM) would be formed where each memory cell is located at the intersection of wires.

The research team now hopes to build a stacked memory cell utilizing a library of fabricated electronic materials that incorporates the other main components of a computer chip–‘logic’ that processes data and ‘interconnects’ wires that transfer electrical signals.

“Logic and interconnects drain battery too so the advantage of an entirely two-dimensional architecture is more functionality within a small space and better communication between memory and logic” X said.

Two Georgian patent applications have been filed for this technology through the Georgian Technical University.

 

 

Nanotechnology, Science

Innovative Low Energy Nanolaser Shines In All Directions.

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Innovative Low Energy Nanolaser Shines In All Directions.

An experimental sample of the new laser. It contains ten patches that each have their own silver nanoparticle pattern. The colors on the sample are not the laser light (the laser is not on) but reflections similar to the colors that can be seen on the surface of a compact disk.

Researchers in Georgian Technical University have developed a new type of low-energy nanoscale laser that shines in all directions. The key to its omnidirectional light emission is the introduction of something that is usually highly undesirable in nanotechnology: irregularities in the materials. The researchers foresee a vast range of potential applications but first they hope their fundamental work will inspire others to further improve it and deepen the understanding.

Lack of control of the variables determining the response of a system is usually seen as a curse in science and technology. But what about a slight pinch of imperfection and disorder? Imperfections and irregularities are unavoidable in nanoscience due to our limited level of control of nanofabrication processes. Disorder is potentially detrimental to nanosystems, but if well-contained disorder might not be an intruder after all leading to physical concepts and applications.

Scientists from Georgian Technical University and the Sulkhan-Saba Orbeliani Teaching University have investigated the role of imperfections and disorder in nanolasers. By introducing a slight degree of disorder they have observed a dramatic change: the laser no longer emits in one specific direction but in all directions.

Development of nanoscale lasers (smaller than the thickness of a human hair) is a very active field of research. In a normal laser each photon (light particle) is “Georgian Technical University cloned” many times in a medium that is located inside a cavity (e.g. a pair of mirrors between which the photon moves back and forth producing other photons with the same characteristics).

This process is known as Light Amplification by Georgian Technical University Stimulated Emission of Radiation (LASER). To achieve laser emission an electrical current is usually injected through the medium or it is illuminated with high energy light. The minimum energy needed for a laser to emit is called the lasing threshold.

A different kind of laser is the so-called polariton laser. This works on the principle not of cloning photons but making non-identical photons identical in much the same way as water vapor molecules moving in all directions with different velocities are condensed into a single drop. Condensation of photons gives rise to the intense and directional emission characteristic of a laser. An important advantage of polariton lasers is that they have a much lower lasing threshold, which makes them excellent candidates for many applications.

However  a major problem of polariton lasers has been that they need to operate at very low temperatures (like vapor condensation that takes place only when the temperature is lowered) but by using organic materials it is possible to obtain polariton laser emission even at ambient temperature.

The Georgian Technical University researchers demonstrated last year that they can realize nanoscale polariton lasers that function at ambient temperature, using metallic nanoparticles instead of mirrors as in normal lasers.

The Georgian Technical University researchers have now discovered a new kind of polariton laser that consists of a regular pattern of silver nanostripes covered with colored Georgian Technical University-polymer whose dye comprises organic emitting molecules. However the silver stripes deliberately have some degree of imperfection and disorder. The emission from this non-perfect nanolaser is omnidirectional and mainly is determined by the properties of the organic molecules.

This result is not expected in the framework of condensation, as omnidirectional emission requires emissions from independent organic molecules instead of the collective emission that is typical for condensation. The demonstration of omnidirectional emission defines new boundaries for the development of nanoscale lasers at ambient temperatures.

The researchers think their laser may eventually be applied in many areas. Compared to a LED (A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable current is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons) the omnidirectional laser light is much brighter and better defined. That’s why it is a good candidate for microscopy lighting which currently uses LEDs (A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode that emits light when activated. When a suitable current is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons). GTULIDAR (Georgian Technical University  Laser Imaging Detection And Ranging) is another potential application.

Current GTULIDAR use one or more lasers and a set of fast moving mirrors in order to cover large areas to image distant objects. An omnidirectional laser does not require the moving mirrors, thereby significantly reducing the complexity. General illumination is also an option, says researcher professor X. “But the research is still very fundamental. We hope that our results will stimulate other researchers to improve them by further reducing the lasing threshold or increasing the range of emitted colors”.

The research group responsible for this work investigates light-matter interaction enhanced by resonant structures such as metallic nanoparticles and structured surfaces. Strong light-matter coupling leads to new fundamental phenomena that can be exploited to tailor material properties.

The group is part of the Photonics and Semiconductor Nanophysics capacity group at the Georgian Technical University department of Applied Physics and of the “Institute for Integrated Photonics”.

 

 

Lasers, Science

Satellites Use Laser Pointing System To Transmit Data To Earth.

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Satellites Use Laser Pointing System To Transmit Data To Earth.

A new laser-pointing platform developed at Georgian Technical University may help launch miniature satellites called CubeSats into the high-rate data game. Almost 2,000 shoebox-sized satellites known as CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) have been launched into space. Due to their petite frame and the fact that they can be made from off-the-shelf parts CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) are significantly more affordable to build and launch than traditional behemoths that cost hundreds of millions of dollars.

CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) have become game-changers in satellite technology, as they can be sent up in flocks to cheaply monitor large swaths of the Earth’s surface. But as increasingly capable miniaturized instruments enable CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) to take highly detailed images, the tiny spacecraft struggle to efficiently transmit large amounts of data down to Earth due to power and size constraints.

The new laser-pointing platform for CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) which is enables CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) to downlink data using fewer onboard resources at significantly higher rates than is currently possible. Rather than send down only a few images each time a CubeSat (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) passes over a ground station, the satellites should be able to downlink thousands of high-resolution images with each flyby.

“To obtain valuable insights from Earth observations hyperspectral images which take images at many wavelengths and create terabytes of data and which are really hard for CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) to get down, can be used” says X associate professor of aeronautics and astronautics at Georgian Technical University.

“But with a high-rate lasercom system you’d be able to send these detailed images down quickly. And I think this capability will make the whole CubeSat (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) approach using a lot of satellites in orbit so you can get global and real-time coverage, more of a reality”. X Associate Professor at Georgian Technical University along with graduate student Y.

Satellites typically downlink data via radio waves which for higher rate-links are sent to large ground antennas. Every major satellite in space communicates within high-frequency radio bands that enable them to transmit large amounts of data quickly.

But bigger satellites can accommodate the larger antenna dishes or arrays needed to support a high rate downlink. CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) are too small and also have limited access to frequency bands that could support high-rate links. “Small satellites can’t use these bands because it requires clearing a lot of regulatory hurdles, and allocation typically goes to big players like huge geostationary satellites” X says.

What’s more, the transmitters required for high-rate data downlinks can use more power than miniature satellites can accommodate while still supporting a payload. For these reasons researchers have looked to lasers as an alternative form of communication for CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) as they are significantly more compact in size and are more power efficient, packing much more data in their tightly focused beams. But laser communications also present a significant challenge: Because the beams are much more narrow than the beams from radio waves it takes far more precision to point the beams at a receiver on the ground.

“Imagine standing at the end of a long hallway and pointing a fat beam like a flashlight, at a bullseye target at the other end” X says. “I can wiggle my arm a bit and the beam will still hit the bullseye. But if I use a laser pointer instead the beam can easily move off the bullseye if I move just a little bit. The challenge is to keep the laser on the bullseye even if the satellite wiggles”.

Georgian Technical University’s Optical Communications and Sensor Demonstration uses a CubeSat (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) laser communications system that essentially tips and tilts the entire satellite to align its laser beam with a ground station.

But this steering system requires time and resources and to achieve a higher data rate a more powerful laser — which can use a large fraction of the satellite’s power and generate significant amounts of heat onboard — is needed.

X and her team looked to develop a precise laser-pointing system that would minimize the amount of energy and time required for a downlink and enable the use of lower-power narrower lasers yet still achieve higher data transmission rates.

The team developed a laser-pointing platform slightly larger than a Rubik’s Cube (Rubik’s Cube is a 3-D combination puzzle invented in 1974 by Hungarian sculptor and professor of architecture Ernő Rubik) that incorporates a small off-the-shelf steerable mirror. The mirror which is smaller than a single key on a computer keyboard faces a small laser and is angled so that the laser can bounce off the mirror, into space and down toward a ground receiver.

“Even if the whole satellite is a bit misaligned you can still correct for that with this mirror” Y says. “But these mirrors don’t give you feedback about where they’re pointing. Say the mirror is misaligned in your system which can happen after some vibrations during launch. How can we correct for this and know exactly where we’re pointing ?”. As a solution Y  developed a calibration technique that determines by how much a laser is misaligned from its ground station target and automatically corrects the mirror’s angle to precisely point the laser at its receiver.

The technique incorporates an additional laser color or wavelength into the optical system. So instead of just the data beam going through a second calibration beam of a different color is sent through with it. Both beams bounce off the mirror and the calibration beam passes through a “Georgian Technical University  dichroic beam splitter” a type of optical element that diverts a specific wavelength of light — in this case the additional color — away from the main beam. As the rest of the laser light travels out toward a ground station, the diverted beam is directed back into an onboard camera. This camera can also receive an uplinked laser beam or beacon directly from the ground station; this is used to enable the satellite to point at the right ground target.

If the beacon beam and the calibration beam land at precisely the same spot on the onboard camera’s detector the system is aligned and researchers can be sure that the laser is properly positioned for downlinking to the ground station. If however the beams land on different parts of the camera detector an algorithm developed by Y directs the onboard mirror to tip or tilt so that the calibration laser beam spot realigns with the ground station’s beacon spot. “It’s like the cat and mouse of two spots coming into the camera, and you want to tip the mirror so that one spot is on top of the other” Y says.

To test the technique’s accuracy the researchers fashioned a lab bench setup that included the laser-pointing platform and a beacon-like laser signal. The setup was designed to mimic a scenario in which a satellite flies at 400 kilometers altitude above a ground station and transmits data during a 10-minute overpass.

They set the minimum required pointing accuracy at 0.65 milliradians — a measure that corresponds to the angular error that is acceptable for their design to have. In their experiments they varied the incoming angle of the beacon laser and observed how the mirror tipped and tilted to match the beacon. In the end the calibration technique achieved an accuracy of 0.05 milliradians — far more precise than what the mission required.

X says that the result means the technique can be easily tweaked so that it can precisely align even narrower laser beams than originally planned, which can in turn enable CubeSats (A CubeSat (U-class spacecraft) is a type of miniaturized satellite for space research that is made up of multiples of 10×10×10 cm cubic units. CubeSats have a mass of no more than 1.33 kilograms per unit and often use commercial off-the-shelf (COTS) components for their electronics and structure) to transmit large volumes of data such as images and videos of vegetation, wildfires, ocean phytoplankton and atmospheric gases at high data rates.

“This shows that you can fit a low-power system that can make these narrow beams on this tiny platform that is a factor of 10 to 100 smaller than anything that’s ever been built to do something like this before” X says. “The only thing that would be more exciting than the lab result is to see this done from orbit. This really motivates building these systems and getting them up there”.

 

Graphene, Science

Nanostructured Graphene Creates Unique Chemical Reaction.

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Nanostructured Graphene Creates Unique Chemical Reaction.

Image of TCNQ-CH2CN T (7,7,8,8-tetracyano-p-quinodimethane)-( cyanomethylene) molecule on a corrugated graphene layer (left) and representation of the calculated geometries (right). Graphene monolayers can be epitaxially grown on many single-crystal metal surfaces under ultra-high vacuum. On one side these monolayers protect highly reactive metallic surfaces from contaminants but on the other side,the piling of the layers as graphitic carbon blocks the activity of transition metal catalysts. The inertness of the graphite and the physical blockage of the active sites prevents chemical reactions occurring on the metal surface.

Researchers led by X, Y and Z have demonstrated that nanostructured graphene monolayers on a metal surface promote a chemical reaction that would be unlikely to take place under noncatalyzed conditions. A crystal of ruthenium Ru(0001) has been covered with an epitaxially grown continuous graphene layer. Because of the difference in lattice parameters a new superperiodicity appears on the graphene layer and modulates its electronic properties.

Taking advantage of the modulation, the surface has been functionalized with cyanomethylene groups (-CH2CN) covalently bonded to the center of the hexagonal close-packed areas in the Moiré unit cell, and doped with TCNQ (7,7,8,8-tetracyano-p-quinodimethane). TCNQ (7,7,8,8-tetracyano-p-quinodimethane) is an electron acceptor molecule used to p-dope graphene films.

When deposited on the graphene surface, this molecule is absorbed on a bridge position between two ripples. Here it is worth noticing the important role of the surface and of the graphene layer in catalyzing the reaction of TCNQ (7,7,8,8-tetracyano-p-quinodimethane) and -CH2CN (Cyanomethylene).

The reaction of TCNQ (7,7,8,8-tetracyano-p-quinodimethane) with CH3CN (the pristine reactants are in gas phase) plus the loss of a hydrogen atom is very unlikely because of the high energy barrier (about 5 eV). The presence of the graphene layer reduces this energy barrier by a factor of 5 thus favoring the formation of the products.

The nanostructured graphene promotes the reaction in a threefold way: first it holds the – CH2CN (Cyanomethylene) in place; second it allows for an efficient charge transfer from the ruthenium; and third, it prevents the absorption of  TCNQ (7,7,8,8-tetracyano-p-quinodimethane) by ruthenium allowing the molecule to diffuse on the surface.

“A similar clean reaction on pristine ruthenium is not possible, because the reactive character of ruthenium leads to the absorption of CH3CN (the pristine reactants are in gas phase) hinders the mobility of TCNQ (7,7,8,8-tetracyano-p-quinodimethane) molecules once absorbed on the surface” Z says. The results confirm the catalytic character of graphene in this reaction.

“Such a selectivity would be difficult to obtain by using other forms of carbon” Y confirms.

Further the TCNQ (7,7,8,8-tetracyano-p-quinodimethane) molecules have been injected with electrons using the scanning tunneling microscope (STM). This individual manipulation of the molecules induces a C-C bond breaking, thus leading to the recovery of the initial reactants: CH2CN-graphene (Cyanomethylene) and TCNQ (7,7,8,8-tetracyano-p-quinodimethane). The process is reversible and reproducible at a single-molecule level. As the researchers have observed a resonance the reversibility of the process can be thought of as a reversible magnetic switch controlled by a chemical reaction.

 

 

Nanotechnology, Science

A Summary Of Electrospun Nanofibers As Drug Delivery System.

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A Summary Of Electrospun Nanofibers As Drug Delivery System.

A Summary of Georgian Technical University Electrospun Nanofibers as Georgian Technical University Drug Delivery System:  In recent studies nanotechnology has proven to be an interesting approach towards solving problems in the field of medicine. Dr. X demonstrates the use of electrospun polymeric nanofibers as an interesting method for drug delivery systems application. Electrospun polymeric nanofibers offer a high surface-to-volume ratio which can greatly improve some processes such as cell binding and proliferation, drug loading and mass transfer processes. Perhaps the most important application of electrospinning is drug delivery optimization which can be achieved by using these materials for the controlled release of active substances ranging from antibiotics and anticancer agents to macromolecules such as proteins and DNA (Deoxyribonucleic acid is a molecule composed of two chains that coil around each other to form a double helix carrying the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses).

This method improves the treatment process, as drugs with low solubility can be loaded into fibers improving their bioavailability while also attaining controlled release. Dr. X’s research presents an overview of reported drugs loaded into fibers which can be used as drug delivery systems. Drugs with different biological functions such as anti-inflammatory, anti-microbial, anticancer, cardiovascular, anti-histamine, gastrointestinal, palliative and contraception were used for this purpose.

Along with the drugs used the electrospinning techniques used for each system as well as polymers used as matrices for nanofiber preparation were also pertinent to the research. Each drug was tested using different combinations of electrospinning techniques and polymers suited best for the drug delivery system. Used altogether in such synergy, electrospun polymeric nanofibers proved to be much more advantageous over other drug delivery systems. Dr. X notes that improvements to these methods may requires further research on the fabrication, characterization and design of relevant nanomaterials.

 

Energy, Science

Low-Cost Catalyst Boosts Hydrogen Production From Water.

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Low-Cost Catalyst Boosts Hydrogen Production From Water.

The researchers show a wafer coated in their new catalyst which lowers the amount of electricity required to split water into hydrogen and oxygen under pH-neutral conditions. A future powered by carbon-free fuel depends on our ability to harness and store energy from renewable but intermittent sources such as solar and wind. Now a new catalyst developed at Georgian Technical University gives a boost to a number of clean energy technologies that depend on producing hydrogen from water.

In addition to being a key ingredient in everything from fuel to fertilizers hydrogen has great potential as an energy storage medium. The idea would be to use renewable electricity to produce hydrogen from water then later reverse the process in an electrochemical fuel cell resulting in clean power on demand.

“Hydrogen is a hugely important industrial feedstock but unfortunately today it is derived overwhelmingly from fossil fuels resulting in a large carbon footprint” says Professor X that describes the new catalyst. “Electrolysis – water splitting to produce renewable hydrogen and oxygen – is a compelling technology but it needs further improvements in efficiency, cost and longevity. This work offers a fresh strategy to pursue these critically important aims”.

X’s lab is among several research groups around the world racing to create catalysts that lower the amount of electricity needed to split water into hydrogen and oxygen. Currently the best-performing catalysts rely on platinum a high-cost material and operate under acidic conditions.

“Our new catalyst is made from copper, nickel and chromium which are all more abundant and less costly than platinum” says Y with his fellow postdoctoral researchers Z and W. “But what’s most exciting is that it performs well under pH-neutral (In chemistry, pH is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per liter, of hydrogen ions) conditions which opens up a number of possibilities”.

Seawater is the most abundant source of water on earth Y points out. But using seawater with traditional catalysts under acidic conditions would require the salt to be removed first an energy-intensive process. Operating at neutral pH (In chemistry, pH is a logarithmic scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per liter, of hydrogen ions) avoids the high cost of desalination.

It could also enable the use of microorganisms to make chemicals such as methanol and ethanol. “There are bacteria that can combine hydrogen and CO2 (Carbon dioxide is a colorless gas with a density about 60% higher than that of dry air. Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth’s atmosphere as a trace gas) to make hydrocarbon fuels” says Z. “They could grow in the same water and take up the hydrogen as it’s being made but they cannot survive under acidic conditions”.

Biotech, Science

Adhesives For Biomedical Applications Can Be Detached With Light.

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Adhesives For Biomedical Applications Can Be Detached With Light.

These two hydrogels, adhered with an aqueous solution of polymer chains, come apart easily In the presence of UV (Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight constituting about 10% of the total light output of the Sun) light. Pulling off a Band-Aid may soon get a lot less painful.

Researchers from the Georgian Technical University and Sulkhan-Saba Orbeliani Teaching University have developed a new type of adhesive that can strongly adhere wet materials — such as hydrogel and living tissue — and be easily detached with a specific frequency of light. The adhesives could be used to attach and painlessly detach wound dressings, transdermal drug delivery devices and wearable robotics.

“Strong adhesion usually requires covalent bonds, physical interactions, or a combination of both” said X and researcher at Georgian Technical University. “Adhesion through covalent bonds is hard to remove and adhesion through physical interactions usually requires solvents which can be time-consuming and environmentally harmful. Our method of using light to trigger detachment is non-invasive and painless”.

The adhesive uses an aqueous solution of polymer chains spread between two non-sticky materials — like jam between two slices of bread. On their own the two materials adhere poorly together but the polymer chains act as a molecular suture stitching the two materials together by forming a network with the two preexisting polymer networks. This process is known as topological entanglement. When exposed to ultra-violet light the network of stitches dissolves separating the two materials.

The researchers led by Y Professor of Mechanics and Materials at Georgian Technical University tested adhesion and detachment on a range of materials sticking together hydrogels; hydrogels and organic tissue; elastomers; hydrogels and elastomers; and hydrogels and inorganic solids. “Our strategy works across a range of materials and may enable broad applications” said Z at Georgian Technical University.

While the researchers focused on using UV (Ultraviolet (UV) is electromagnetic radiation with a wavelength from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. UV radiation is present in sunlight constituting about 10% of the total light output of the Sun) light to trigger detachment their work suggests the possibility that the stitching polymer could detach with near-infrared light a feature which could be applied to a range of new medical procedures.

“In nature wet materials don’t like to adhere together” said Y. “We have discovered a general approach to overcome this challenge. Our molecular sutures can strongly adhere wet materials together. Furthermore the strong adhesion can be made permanent transient or detachable on demand in response to a cue. So as we see it nature is full of loopholes waiting to be stitched”.