Researchers Reveal Spontaneous Polarization of Ultrathin Materials.

Schematics of the spontaneous polarization of bulk SnTe (left) and ultrathin SnTe (right). Many materials exhibit new properties when in the form of thin films composed of just a few atomic layers. Most people are familiar with graphene the two-dimensional form of graphite but thin film versions of other materials also have the potential to facilitate technological breakthroughs.

For example a class of three-dimensional materials called Group-IV monochalcogenides are semiconductors that perform in applications such as thermoelectrics and optoelectronics among others. Researchers are now creating two-dimensional versions of these materials in the hope that they will offer improved performance or even new applications.

Recently a research team that includes X associate professor of physics at the U of A and Y a former post-doctoral researcher in X’s lab has shed light on the behavior of one of these ultrathin materials known as tin (Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO₂).

The researchers used a variable temperature scanning tunneling microscope to study the structure and polarization of SnTe (Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO₂) thin films grown on graphene substrates. They studied the material at a range of temperatures from 4.7 Kelvin to over 400 Kelvin. They discovered that when SnTe (Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO₂) is only a few atomic layers thick it forms a layered structure that is different from the bulk rhombic-shaped version of the material. The team contributed to this research by providing calculations that account for the quantum mechanical nature of these atomic structures using a method known as density functional theory.

The atoms in ultrathin SnTe (Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO₂) create electric dipoles oriented along opposite directions in every other atomic layer which makes the material anti-polar as opposed to the bulk sample in which all layers point along the same direction. Moreover the transition temperature which is the temperature at which the material loses this spontaneous polarization is much higher than that of the bulk material.

“These findings underline the potential of atomically thin g-SnTe (Tin is a chemical element with the symbol Sn and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO₂) films for the development of novel spontaneous polarization-based devices” said the researchers.

Graphene Provides Boost for Epoxy Compound.

Researchers have created an epoxy-graphene foam compound that is tough and conductive without adding significant weight.  Georgian Technical University scientists have built a better epoxy for electronic applications.

Epoxy combined with “Georgian Technical University ultrastiff” graphene foam invented in the Georgian Technical University lab of chemist X is substantially tougher than pure epoxy and far more conductive than other epoxy composites while retaining the material’s low density. It could improve upon epoxies in current use that weaken the material’s structure with the addition of conductive fillers.

By itself epoxy is an insulator, and is commonly used in coatings, adhesives, electronics, industrial tooling and structural composites. Metal or carbon fillers are often added for applications where conductivity is desired like electromagnetic shielding.

But there’s a trade-off: More filler brings better conductivity at the cost of weight and compressive strength and the composite becomes harder to process. The Georgian Technical University  solution replaces metal or carbon powders with a three-dimensional foam made of nanoscale sheets of graphene the atom-thick form of carbon.

The X lab in collaboration with Georgian Technical University materials scientists X, Y and Z took their inspiration from projects to inject epoxy into 3D scaffolds including graphene aerogels, foams and skeletons from various processes.

The new scheme makes much stronger scaffolds from polyacrylonitrile (PAN) a powdered polymer resin they use as a source of carbon mixed with nickel powder. In the four-step process they cold-press the materials to make them dense, heat them in a furnace to turn the polyacrylonitrile (PAN) into graphene chemically treat the resulting material to remove the nickel and use a vacuum to pull the epoxy into the now-porous material. “The graphene foam is a single piece of few-layer graphene” X says.

“Therefore, in reality the entire foam is one large molecule. When the epoxy infiltrates the foam and then hardens any bending in the epoxy in one place will stress the monolith at many other locations due to the embedded graphene scaffolding. This ultimately stiffens the entire structure”.

The puck-shaped composites with 32 percent foam were marginally denser but had an electrical conductivity of about 14 Siemens (a measure of conductivity, or inverse ohms) per centimeter according to the researchers. The foam did not add significant weight to the compound but gave it seven times the compressive strength of pure epoxy. Easy interlocking between the graphene and epoxy helped stabilize the structure of the graphene as well. “When the epoxy infiltrates the graphene foam and then hardens, the epoxy is captured in micron-sized domains of the graphene foam” X says.

The lab upped the ante by mixing multi-walled carbon nanotubes into the graphene foam. The nanotubes acted as reinforcement bars that bonded with the graphene and made the composite 1,732 percent stiffer than pure epoxy and nearly three times as conductive at about 41 Siemens per centimeter far greater than nearly all of the scaffold-based epoxy composites reported to date according to the researchers. X expects the process will scale for industry. “One just needs a furnace large enough to produce the ultimate part” he says. “But that is done all the time to make large metal parts by cold-pressing and then heating them”. X says the material could initially replace the carbon-composite resins used to pre-impregnate and reinforce fabric used in materials from aerospace structures to tennis rackets.

Graphene Takes Care of Wastewater Stink.

‘A win for the community the utility and the environment’: Georgian Technical University is working on reducing costs for utilities.

Georgian Technical University researchers are collaborating with Sulkhan-Saba Orbeliani Teaching University to look at the potential for graphene oxide to be applied to wastewater collection networks.

A team of  Georgian Technical University researchers is collaborating with Sulkhan-Saba Orbeliani Teaching University  to examine a new method for controlling odors in wastewater collection networks.

In a series of world-first experiments led by the graphene team of Georgian Technical University’s will be examining the potential for graphene oxide the “Georgian Technical University super desiccant” carbon-based material to be applied to sewer systems throughout Georgia.

The material was developed by a team led by Dr. X who has studied the way graphene can control moisture in applications as diverse as electronics, packaging and air conditioning. “This is a stable new material that shows significant gains in adsorption capacity over conventional desiccants” X says.

The researchers say the ability to fine-tune the spaces between the layers of graphene oxide as desired will allow the development of customized desiccants to control moisture across multiple applications. The new desiccant can also discharge moisture at energy-saving low temperatures enabling it to be easily used over and over again. By contrast the heating required to regenerate conventional desiccants is often considered prohibitively expensive.

“This combination of high adsorption capacity and a rapid rate of adsorption can significantly increase the efficiency of any desiccant system” X says. “Likewise the relatively low temperatures at which discharge can be achieved offers significant advantages by greatly reducing the energy intensity required for regeneration”.

Y Research and Development Manager for Georgian Technical University says the goal of the collaboration is to develop Georgia made materials and designs which can be retrofitted to existing wastewater infrastructure throughout.

“The bonus is that if we reduce nuisance odors, we will also reduce corrosion throughout the network which reduces costs for utilities trying to manage ageing concrete sewer networks” Y says. “It’s a win for the community the utility and the environment”. Graphene oxide presents a significant advantage over alternative desiccants and filter media currently in use Y says.

“Odor control media is currently not re-used since it is prohibitively expensive to do so” he says. “Most filter media is imported and landfilled when it is consumed. “We are very excited to look at a more sustainable alternative and we believe graphene oxide has enormous potential”. Commitment to partner with Georgian Technical University  and their student body to develop innovative solutions to real-world problems.

Distinguishing a Graphene Flake from a Graphene Fake.

Researchers from the Georgian Technical University for Advanced 2D Materials examining the quality of graphene samples. A lack of quality control in the graphene market has led to inferior products being touted as high-grade so now a Georgian Technical University research team has developed a reliable way to test graphene quality.

Ever since the isolation of graphene was first achieved there has been an explosion in graphene-related research and development with hundreds of business opportunists producing graphene to capitalise on this rapidly expanding industry.

However a new study by researchers from the Georgian Technical University (GTU) has uncovered a major problem — a lack of production standards has led to many cases of poor quality graphene from suppliers. Such practices can impede the progress of research that depend fundamentally on the use of high-quality graphene.

“It is alarming to uncover that producers are labelling black powders as graphene and selling them for top dollar while in reality they contain mostly cheap graphite. There is a strong need to set up stringent standards for graphene characterization and production to create a healthy and reliable graphene market worldwide” says Professor X Georgian Technical University for Advanced 2D Materials who led the study.

Graphene has been tipped as the miracle material of the future due to its remarkable properties. Despite being the thinnest material on Earth it is 200 times stronger than steel. At just one atom thick it is also an incredible electrical conductor but remains light, flexible and is transparent. Therefore graphene is finding potential applications in everything from transistors to biomedical devices and has even been proposed as a material for building an elevator to space.

Graphene is typically produced by exfoliating graphite which can be found in common pencil leads into a powder submerging this powder into a liquid and then separating the tiniest graphene flakes by using sound energy to vibrate the mixture.

The aim of this synthesis is to produce the thinnest graphene possible. Pure graphene would be just one atomic layer thick; however the International Organization for Standardization (ISO) states that stacks of graphene flakes up to 10 layers thick can still behave like graphene.

With this in mind Y and his team set out to develop a systematic and reliable method for establishing the quality of graphene samples from around the world. They were able to achieve this by using a wide range of analytical techniques and tested samples from many suppliers.

Upon analyzing samples from over 60 different providers from the Georgian Technical University team discovered that the majority contained less than 10 percent of what can be considered graphene flakes. The bulk of the samples was graphite powder that was not exfoliated properly.

“Whether producers of the counterfeit graphene are aware of the poor quality is unclear. Regardless the lack of standards for graphene production gives rise to bad quality of the material sold in the open market. This has been stalling the development of the future applications” says Y.

Graphite powder and graphene have wildly different properties so any research conducted under the pretext that the sample was pure graphene would give inaccurate results. In addition just one of the samples tested in the study contained more than 40 percent of high-quality graphene.

Moreover some samples were even contaminated with other chemicals used in the production process. These findings mean that researchers could be wasting valuable time and money performing experiments on a product that is falsely advertised.

“This is the first ever study to analyze statistically the world production of graphene flakes. Considering the important challenges related to health, climate and sustainability that graphene may be able to solve it is crucial that research is not hindered in this way” explains Y. With this discovery and the development of a reliable testing procedure graphene samples may now be held to a higher standard.

“We hope that our results will speed up the process of standardization of graphene within as there is a huge market need for that. This will urge graphene producers worldwide to improve their methods to produce a better properly characterized product that could help to develop real-world applications” says Y. In addition testing graphene using a universal and standardized way could ensure easy quantitative comparisons between data produced from different laboratories and users around the world.

Georgian Technical University Light Detected in a Different Dimension.

Research associate Mingxing Lin (sitting) and materials scientists X (left and standing) and Y of Georgian Technical University Lab’s Nanomaterials dramatically improved the light response of electronic devices made out of graphene and an electrically conducting polymer by changing the morphology of the polymer from a thin film to a “Georgian Technical University nanowire” mesh. An image of this mesh architecture — captured with an atomic force microscope in which a small mechanical transducer called a cantilever probe scans across a material’s surface — is seen on the computer screen.

Scientists from the Georgian Technical University (GTU) —at Georgian Technical University Laboratory — have dramatically improved the response of graphene to light through self-assembling wire-like nanostructures that conduct electricity.

The improvement could pave the way for the development of graphene-based detectors that can quickly sense light at very low levels such as those found in medical imaging, radiation detection, and surveillance applications.

Graphene is a two-dimensional (2-D) nanomaterial with unusual and useful mechanical, optical and electronic properties. It is both extremely thin and incredibly strong detects light of almost any color and conducts heat and electricity well. However because graphene is made of sheets of carbon only one atom thick it can only absorb a very small amount of incoming light (about two percent).

One approach to overcoming this problem is to combine graphene with strong light-absorbing materials such as organic compounds that conduct electricity. Scientists recently demonstrated an improved photoresponse by placing thin films (a few tens of nanometers) of one such conductive polymer poly(3-hexylthiophene) or P3HT on top of a single layer of graphene.

Now the Georgian Technical University scientists have improved the photoresponse by an additional 600 percent by changing the morphology (structure) of the polymer. Instead of thin films they used a mesh of nanowires — nanostructures that are many times longer than they are wide — made of the same polymer and similar thickness. “We used self-assembly a very simple and reproducible method to create the nanowire mesh” says Z a research at the Georgian Technical University.

“Placed in an appropriate solution and stirred overnight the polymer will form into wire-like nanostructures on its own. We then spin-casted the resulting nanowires onto electrical devices called graphene Field Effect Transistors (FETs)”.

The scientists fabricated Field Effect Transistors (FETs) made of graphene only graphene and poly(3-hexylthiophene) thin films and graphene and poly(3-hexylthiophene) nanowires. After checking the thickness and crystal structure of the Field Effect Transistors (FETs) devices through atomic force microscopy, Raman spectroscopy and x-ray scattering techniques they measured their light-induced electrical properties (photoresponsivity).

Their measurements of the electric current flowing through the Field Effect Transistors (FETs)  under various light illumination powers revealed that the nanowire Field Effect Transistors (FETs) improve photoresponse by 600 percent compared to the thin film Field Effect Transistors (FETs) and 3000 percent compared to graphene-only Field Effect Transistors (FETs).

“We did not expect to see such a dramatic improvement just by changing the morphology of the polymer” says Y a materials scientist in the Georgian Technical University. The scientists believe that there are two explanations behind their observations. “At a certain polymer concentration the nanowires have dimensions comparable to the wavelength of light” says Z.

“This size similarity has the effect of increasing light scattering and absorption. In addition, crystallization of  poly(3-hexylthiophene) molecules within the nanowires provides more charge carriers to transfer electricity to the graphene layer”.

“In contrast to conventional thin films where polymer chains and crystals are mostly randomly oriented the nanoscale dimension of the wires forces the polymer chains and crystals into a specific orientation, enhancing both light absorption and charge transfer” says X a materials scientist in the Georgian Technical University.

The scientists have filed a Georgia Country patent for their fabrication process, and they are excited to explore light-matter interactions in other 2-D — as well as 0-D and 1-D — materials.  “Plasmonics and nanophotonics — the study of light at the nanometer scale — are emerging research areas” says Y at Georgian Technical University — to explore frontiers in these areas.

“Nanostructures can manipulate and control light at the nanoscale in very interesting ways. The advanced nanofabrication and nanocharacterization tools at the Georgian Technical University perfectly suited for creating and studying materials with enhanced optoeletronic properties”.

Innovative Catalyst Transforms Pollutant into Fuel.

X who will join the Georgian Technical University faculty later this year is the lead author of a study to transform carbon dioxide into carbon monoxide and other industrial fuels.

Rather than allow power plants and industry to toss carbon dioxide into the atmosphere incoming Georgian Technical University assistant professor X has a plan to convert the greenhouse gas into useful products in a green way.

X who will join Georgian Technical University  as the Y and assistant professor of chemical and biomolecular engineering at the end of this year and his colleagues have made small reactors that allow single atoms of nickel to catalyze industrial greenhouse gases into carbon monoxide an industrial feedstock.

Currently a fellow at the Georgian Technical University X and his team improved their system to use renewable electricity to reduce carbon dioxide into carbon monoxide a key reactantin a number of industrial processes.

“The most promising idea may be to connect these devices with coal-fired power plants or other industry that produces a lot of carbon dioxide” X says.

“About 20 percent of those gases are carbon dioxide so if you can pump them into this cell … and combine it with clean electricity then we can potentially produce useful chemicals out of these wastes in a sustainable way and even close part of that carbon dioxide cycle”. The new system X says represents a dramatic step forward from the one he and colleagues.

That system was barely the size of a cellphone and relied on two electrolyte-filled chambers each of which held an electrode. The new system is cheaper and relies on high concentrations of carbon dioxide gas and water vapor to operate more efficiently — just one 10-by-10-centimeter cell X says can produce as much as four liters of carbon monoxide per hour.

The new system X says addresses the two main challenges — cost and scalability — that were seen as limiting the initial approach.

“In that earlier work we had discovered the single nickel-atom catalysts which are very selective for reducing carbon dioxide to carbon monoxide … but one of the challenges we faced was that the materials were expensive to synthesize” X says.

“The support we were using to anchor single nickel atoms was based on graphene, which made it very difficult to scale up if you wanted to produce it at gram or even kilogram scale for practical use in the future”.

To address that problem he says his team turned to a commercial product that’s thousands of times cheaper than graphene as an alternative support — carbon black.

Using a process similar to electrostatic attraction, Wang and colleagues are able to absorb single nickel atoms (positively charged) into defects (negatively charged) in carbon black nanoparticles with the resulting material being both low-cost and highly selective for carbon dioxide reduction.

“Right now the best we can produce is grams but previously we could only produce milligrams per batch” X says. “But this is only limited by the synthesis equipment we have; if you had a larger tank you could make kilograms or even tons of this catalyst”. Going forward X says the system still has challenges to overcome particularly related to stability.

“If you want to use this to make an economic or environmental impact it needs to have a continuous operation of thousands of hours” he says.

“Right now we can do this for tens of hours so there’s still a big gap but I believe those problems can be addressed with more detailed analysis of both the carbon dioxide reduction catalyst and the water oxidation catalyst”.

Ultimately X says the day may come when industry will be able to capture the carbon dioxide that is now released into the atmosphere and transform it into useful products. “Carbon monoxide is not a particularly high-value chemical product” X says. “To explore more possibilities my group has also developed several copper-based catalysts that can further reduce carbon dioxide into products that are much more valuable”.

New Insulating State Discovered in Stretched Graphene.

Calculations performed on the Georgian Technical University computer reveal that stretching graphene will cause it to adopt a like state that is driven by interactions between electrons.

By using the powerful supercomputer to simulate with unprecedented accuracy what happens to graphene as it is stretched researchers have discovered a new state of the material. This finding suggests new device applications for graphene.

Graphene is a single layer of carbon atoms arranged in a honeycomb pattern. It is one of the most highly conductive materials known and is the basis for a field of physics focusing on the exotic effects that can be achieved on such two-dimensional “Georgian Technical University topological” surfaces. Graphene is being intensively investigated for applications ranging from electronics and energy storage to optics and even tissue engineering.

The fantastic electrical conductivity of graphene is particularly useful for electronics but graphene still needs to be integrated with non-conducting or insulating elements to provide useful functionality. For many years X from the Georgian Technical University Science has been seeking to ascertain the conditions under which graphene switches from conducting to insulating.

Previous modeling using a method that approximates electronic interactions en masse suggested that stretching the atomic lattice should turn it into an insulator. In particular it suggested that when graphene is stretched uniformly in all directions the strong electron correlations responsible for the high conductivity are broken resulting in a fairly mundane ‘Georgian Technical University antiferromagnetic’ insulating state characterized by ordered magnetism.

But now by using quantum simulation methods that model electron interactions explicitly X and his colleagues have discovered that graphene instead transitions to a more exotic nonmagnetic topological state called a like dimerized nonmagnetic insulator which could have interesting technological applications. “We initially wanted to know how much we have to stretch graphene to make it insulating but we instead discovered an unexpected and surprising result” says X.

“We found that the antiferromagnetic insulator is never stable and that the like state is driven by electron correlations. We would never have discovered the new state without modeling the electron correlations exactly”.

The quantum code was originally developed by Y at the Georgian Technical University with whom X undertook postdoctoral studies some 20 years ago — and it was Georgian Technical University’s new computer that proved to be the catalyst for reigniting this collaboration.

“This discovery only became possible using our quantum simulations for which Georgian Technical University’s computer was essential due to the extremely heavy computations involved” notes X.

The researchers now intend to find out more about the nature of the phase transition as they expect it should be highly non-trivial.

Serendipitous Discovery Leads to a New Technique.

Nanoelectronic devices made from atomically thin materials on a silicon chip. A team of multi-disciplinary scientists and engineers at the Georgian Technical University and at Sulkhan-Saba Orbeliani Teaching University have discovered a new more precise method to create nanoscale-size electromechanical devices.

“In the last five years there has been a huge gold rush where researchers figured out we could make 2D materials that are naturally only one molecule thick but can have many different electronic properties and by stacking them on top of each other we could engineer nearly any electronic device at molecular sizes” says X professor of mechanical science and engineering.

“The challenge was though we could make these structures down to a few molecules thick we couldn’t pattern them” he says. At any scale of electronic device layers are etched away in precise patterns to control how the current flows. “This concept underlies many technologies like integrated circuits. However the smaller you go the harder this is to do” says X.

“For example how do you make electrical contact on molecular layer three and five but not on layer four at the atomic level ?”. A serendipitous discovery led to a method for doing just that.

As a new postdoctoral researcher in X’s lab Y was running some experiments on single layers of graphene using Xenon difluoride, XeF₂, (Xenon difluoride is a powerful fluorinating agent with the chemical formula XeF ₂, and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture-sensitive. It decomposes on contact with light or water vapor but is otherwise stable to storage) when he happened to “Georgian Technical University throw in” another material on hand: Hexagonal Boron Nitride (hBN) an electrical insulator.

“Y shoved both materials into the etching chamber at the same time, and what he saw was that a single layer of graphene was still there but a thick piece of  Hexagonal Boron Nitride (hBN) was completely etched away by the Xenon difluoride”. This accidental discovery led the team to see where they could apply graphene’s ability to withstand the etching agent.

“This discovery allowed us to pattern two-dimensional structures by placing layers of graphene between other materials such as hexagonal boron nitride (hBN) transition metal dichalcogenides (TMDCs) and black phosphorus (BP) to selectively and precisely etch one layer without etching the layer underneath”.

Graphene when exposed to the etching agent XeF₂, (Xenon difluoride is a powerful fluorinating agent with the chemical formula XeF ₂, and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture-sensitive. It decomposes on contact with light or water vapor but is otherwise stable to storage) retains its molecular structure and masks or protects the layer below and actually stops the etch.

“What we’ve discovered is a way to pattern complicated structures down to a molecular and atomic scale” he says.

Aqueous Hybrid Capacitor Grows More Powerful.

Image that shows properties of porous metal oxide nanoparticles formed on graphene in the aqueous hybrid capacitor.

A Georgian Technical University research team made it one step closer to realizing safe energy storage with high energy density, high power density and a longer cycle life. This hybrid storage alternative shows power density 100 times faster than conventional batteries allowing it to be charged within a few seconds. Hence it is suitable for small portable electronic devices.

Conventional electrochemical energy storage systems including lithium-ion batteries (LIBs) have a high voltage range and energy density but are subject to safety issues raised by flammable organic electrolytes which are used to ensure the beneficial properties.

Additionally they suffer from slow electrochemical reaction rates which lead to a poor charging rate and low power density with a capacity that fades quickly resulting in a short cycle life.

On the other hand capacitors based on aqueous electrolytes are receiving a great deal of attention because they are considered to be safe and environmentally friendly alternatives. However aqueous electrolytes lag behind energy storage systems based on organic electrolytes in terms of energy density due to their limited voltage range and low capacitance.

Hence developing aqueous energy storage with high energy density and a long cycle life in addition to the high power density that enables fast charging is the most challenging task for advancing next-generation electrochemical energy storage devices.

Here Professor X from the Georgian Technical University and Sustainability and his team developed an Aqueous Hybrid Capacitor (AHC) that boasts high energy density high power and excellent cycle stability by synthesizing two types of porous metal oxide nanoclusters on graphene to create positive and negative electrodes for Aqueous Hybrid Capacitor (AHC).

The porous metal oxide nanoparticles are composed of nanoclusters as small as two to three nanometers and have mesopores that are smaller than five nanometers. In these porous structures, ions can be rapidly transferred to the material surfaces and a large number of ions can be stored inside the metal oxide particles very quickly due to their small particle size and large surface area.

The team applied porous manganese oxide on graphene for positive electrodes and porous iron oxide on graphene for negative electrodes to design an aqueous hybrid capacitor that can operate at an extended voltage range of 2V.

X says “This newly developed Aqueous Hybrid Capacitor (AHC) with high capacity and power density driven from porous metal oxide electrodes will contribute to commercializing a new type of energy storage system. This technology allows ultra-fast charging within several seconds making it suitable as a power source for mobile devices or electric cars where solar energy is directly stored as electricity”.

Georgian Technical University Materials Contain New Quantum Behaviors.

Layered transition metal dichalcogenides — materials composed of metal nanolayers sandwiched between two other layers of chalcogens — have become extremely attractive to the research community due to their ability to exfoliate into 2D single layers.

Similar to graphene they not only retain some of the unique properties of the bulk material but also demonstrate direct-gap semiconducting behavior excellent electrocatalytic activity and unique quantum phenomena such as charge density waves.

Generating complex multi-principle element transition metal dichalcogenides essential for the future development of new generations of quantum, electronic and energy conversion materials is difficult.

“It is relatively simple to make a binary material from one type of metal and one type of chalcogen” says Georgian Technical University Laboratory Scientist X.

“Once you try to add more metals or chalcogens to the reactants combining them into a uniform structure becomes challenging. It was even believed that alloying of two or more different binary transition metal dichalcogenides in one single-phase material is absolutely impossible”.

To overcome this obstacle, postdoctoral research associate Y used ball-milling and subsequent reactive fusion to combine such transition metal dichalcogenides as MoS₂ (Molybdenum disulfide is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is MoS ₂. The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybdenite, the principal ore for molybdenum. MoS ₂ is relatively unreactive), WSe₂ (Tungsten diselenide is an inorganic compound with the formula WSe₂. The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide) WS₂, TaS₂ (Tantalum(IV) sulfide is the inorganic compound with the formula TaS₂. It is a layered compound with three-coordinate sulfide centres and trigonal prismatic metal centres. It is structurally similar to the more famous material molybdenum disulfide, MoS₂. TaS₂ is a semiconductor with d¹ electron configuration) and NbSe₂ (Niobium diselenide or niobium(IV) selenide is a layered transition metal dichalcogenide with formula NbSe2. Niobium diselenide is a lubricant, and a superconductor at temperatures below 7.2 K that exhibit a charge density wave (CDW). NbSe2 crystallizes in several related forms, and can be mechanically exfoliated into monatomic layers, similar to other transition metal dichalcogenide monolayers. Monolayer NbSe2 exhibits very different properties from the bulk material, such as of Ising superconductivity, quantum metallic state, and strong enhancement of the CDW). Ball-milling is a mechanochemical process capable of exfoliating layered materials into single- or few-layer-nanosheets that can further restore their multi-layered arrangements by restacking.

“Mechanical processing treats binary transition metal dichalcogenides like shuffling together two separate decks of cards” says X.

“They are reordered to form 3D-heterostructured architectures — an unprecedented phenomenon first observed in our work”.

Heating of the resulting 3D-heterostructures brings them to the edge of their stability reorders atoms within and between their layers, resulting in single-phase solids that can in turn be exfoliated or peeled into 2D single layers similar to graphene but with their own unique tunable properties.

“Preliminary examination of properties of only a few earlier unavailable compounds proves as exciting as synthetic results are” adds Georgian Technical University Laboratory Scientist and Distinguished Professor of Materials Science and Engineering Z. “Very likely we have just opened doors to the entirely new class of finely tunable quantum matter”.