Graphene at home qwerty 07. Graphene: new methods of production and latest achievements. The main direction of the new field of science
Relatively recently, a new field has appeared in science and technology, which is called nanotechnology. The prospects for this discipline are not just vast. They are huge. A particle called a “nano” is a quantity equal to one billionth of a value. Such sizes can only be compared with the sizes of atoms and molecules. For example, a nanometer is one billionth of a meter.
The main direction of the new field of science
Nanotechnologies are those that manipulate matter at the level of molecules and atoms. In this regard, this field of science is also called molecular technology. What was the impetus for its development? Nanotechnology in modern world appeared thanks to a lecture in which the scientist proved that there are no obstacles to creating things directly from atoms.
Means for effective manipulation tiny particles called assembler. This is a molecular nanomachine with which you can build any structure. For example, a natural assembler can be called a ribosome that synthesizes protein in living organisms.
Nanotechnology in the modern world is not just a separate field of knowledge. They represent a vast field of research directly related to many basic sciences. These include physics, chemistry and biology. According to scientists, it is these sciences that will receive the most powerful impetus for development against the backdrop of the coming nanotechnological revolution.
Application area
It is impossible to list all areas of human activity where nanotechnology is used today due to the very impressive list. So, with the help of this field of science the following are produced:
Devices designed for ultra-dense recording of any information;
- various video equipment;
- sensors, semiconductor transistors;
- information, computing and information technologies;
- nanoimprinting and nanolithography;
- energy storage devices and fuel cells;
- defense, space and aviation applications;
- bioinstrumentation.
For such scientific field, like nanotechnology, in Russia, the USA, Japan and a number of European countries, more and more funding is allocated every year. This is due to the broad prospects for the development of this area of research.
Nanotechnologies in Russia are developing according to a targeted Federal program, which provides not only large financial costs, but also a large volume of design and research work. To achieve the assigned tasks, the efforts of various scientific and technological complexes are combined at the level of national and transnational corporations.
New material
Nanotechnology has allowed scientists to make a carbon plate harder than diamond that is only one atom thick. It consists of graphene. This is the thinnest and strongest material in the entire Universe, which transmits electricity much better than silicon in computer chips.
The discovery of graphene is considered a real revolutionary event that will change a lot in our lives. This material has such unique physical properties, which radically changes a person’s understanding of the nature of things and substances.
History of discovery
Graphene is a two-dimensional crystal. Its structure is a hexagonal lattice consisting of carbon atoms. Theoretical research Research on graphene began long before the production of its actual samples, since this material is the basis for constructing a three-dimensional graphite crystal.
Back in 1947, P. Wallace pointed out some of the properties of graphene, proving that its structure is similar to metals, and some characteristics are similar to those possessed by ultrarelativistic particles, neutrinos and massless photons. However, the new material also has certain significant differences that make it unique in nature. But confirmation of these conclusions was received only in 2004, when Konstantin Novoselov first obtained carbon in a free state. This new substance, called graphene, became a major discovery by scientists. You can find this element in a pencil. Its graphite rod consists of many layers of graphene. How does a pencil leave a mark on paper? The fact is that, despite the strength of the layers that make up the rod, there are very weak connections between them. They disintegrate very easily upon contact with paper, leaving a mark when writing.
Using new material
According to scientists, sensors based on graphene will be able to analyze the strength and condition of the aircraft, as well as predict earthquakes. But only when a material with such amazing properties leaves the walls of laboratories will it become clear in which direction the development will go practical application of this substance. Today, physicists, as well as electronics engineers, have already become interested in the unique capabilities of graphene. After all, just a few grams of this substance can cover an area equal to a football field.
Graphene and its applications are potentially being considered in the production of lightweight satellites and aircraft. In this area, a new material can replace nanomaterials. The nanosubstance can be used instead of silicon in transistors, and its introduction into plastic will give it electrical conductivity.
Graphene and its use are also being considered in the manufacture of sensors. These devices are based on newest material, will be able to detect the most dangerous molecules. But the use of nanosubstance powder in the production of electric batteries will significantly increase their efficiency.
Graphene and its applications are considered in optoelectronics. The new material will make a very light and durable plastic, containers from which will keep food fresh for several weeks.
The use of graphene is also expected to make a transparent conductive coating needed for monitors, solar panels and wind turbines that are stronger and more resistant to mechanical stress.
The best sports equipment, medical implants and supercapacitors will be made based on nanomaterials.
Graphene and its use are also relevant for:
High frequency high power electronic devices;
- artificial membranes separating two liquids in a tank;
- improving the conductivity properties of various materials;
- creating a display on organic light-emitting diodes;
- mastering a new technology for accelerated DNA sequencing;
- improvements to liquid crystal displays;
- creation of ballistic transistors.
Automotive use
According to researchers, the specific energy intensity of graphene is close to 65 kWh/kg. This figure is 47 times higher than that of the now so common lithium-ion batteries. Scientists used this fact to create a new generation of chargers.
The graphene-polymer battery is a device with which it is most effectively retained. Electric Energy. Currently, work on it is being carried out by researchers from many countries. Spanish scientists have achieved significant success in this matter. The graphene-polymer battery they created has an energy capacity hundreds of times higher than that of existing batteries. It is used to equip electric vehicles. The car in which it is installed can travel thousands of kilometers without stopping. It will take no more than 8 minutes to recharge an electric vehicle when the energy resource is exhausted.
Touch screens
Scientists continue to explore graphene, creating new and unique things. Thus, carbon nanomaterial has found its application in production of large-diagonal touch displays. In the future, a flexible device of this type may appear.
Scientists obtained a rectangular graphene sheet and turned it into a transparent electrode. It is he who is involved in the operation of the touch display, while being distinguished by durability, increased transparency, flexibility, environmental friendliness and low cost.
Obtaining graphene
Since 2004, when the newest nanomaterial was discovered, scientists have mastered a number of methods for its production. However, the most basic of them are the following methods:
Mechanical exfoliation;
- epitaxial growth in vacuum;
- chemical periphase cooling (CVD process).
The first of these three methods is the simplest. The production of graphene by mechanical exfoliation involves applying special graphite to the adhesive surface of an insulating tape. After this, the base, like a sheet of paper, begins to bend and unbend, separating the desired material. When using this method, the graphene obtained is of the highest quality. However, such actions are not suitable for mass production of this nanomaterial.
When using the epitaxial growth method, thin silicon wafers are used, the surface layer of which is silicon carbide. Next, this material is heated at a very high temperature (up to 1000 K). As a result of a chemical reaction, silicon atoms are separated from carbon atoms, the first of which evaporate. As a result, pure graphene remains on the plate. The disadvantage of this method is the need to use very high temperatures at which combustion of carbon atoms can occur.
The most reliable and in a simple way CVD process used for mass production of graphene. It is a method in which a chemical reaction occurs between a metal catalyst coating and hydrocarbon gases.
Where is graphene produced?
Today, the largest company producing the new nanomaterial is located in China. The name of this manufacturer is Ningbo Morsh Technology. He started graphene production in 2012.
The main consumer of the nanomaterial is Chongqing Morsh Technology. It uses graphene to produce conductive transparent films that are inserted into touch displays.
Relatively recently, the well-known company Nokia filed a patent for a photosensitive matrix. This element, so necessary for optical devices, contains several layers of graphene. This material, used on camera sensors, significantly increases their light sensitivity (up to 1000 times). At the same time, there is a decrease in electricity consumption. A good smartphone camera will also contain graphene.
Receipt at home
Is it possible to make graphene at home? It turns out yes! You just need to take a kitchen blender with a power of at least 400 W and follow the method developed by Irish physicists.
How to make graphene at home? To do this, pour 500 ml of water into the blender bowl, adding 10-25 milliliters of any detergent and 20-50 grams of crushed stylus. Next, the device should operate for 10 minutes to half an hour, until a suspension of graphene flakes appears. The resulting material will have high conductivity, which will allow it to be used in photocell electrodes. Also, graphene produced at home can improve the properties of plastic.
Nanomaterial oxides
Scientists are actively studying the structure of graphene, which has attached oxygen-containing functional groups and/or molecules inside or along the edges of the carbon network. It is the oxide of the hardest nanosubstance and is the first two-dimensional material to reach the stage of commercial production. Scientists made centimeter-sized samples from nano- and microparticles of this structure.
Thus, graphene oxide in combination with diophilized carbon was recently obtained by Chinese scientists. This is a very light material, a centimeter cube of which is held on the petals of a small flower. But at the same time, the new substance, which contains graphene oxide, is one of the hardest in the world.
Biomedical Application
Graphene oxide has a unique selectivity property. This will allow this substance to find biomedical use. Thus, thanks to the work of scientists, it has become possible to use graphene oxide for diagnosing cancer. Unique optical and electrical properties nanomaterial.
Graphene oxide also allows for targeted delivery of medicines and diagnostics. Based on this material, sorption biosensors are created that indicate DNA molecules.
Industrial Application
Various sorbents based on graphene oxide can be used to decontaminate contaminated man-made and natural objects. In addition, this nanomaterial is capable of processing underground and surface water, as well as soils, having cleared them of radionuclides.
Graphene oxide filters can provide super clean rooms where electronic components are produced special purpose. The unique properties of this material will allow you to penetrate into subtle technologies chemical sphere. In particular, this can be the extraction of radioactive, trace and rare metals. Thus, the use of graphene oxide will make it possible to extract gold from low-grade ores.
Until last year the only one known to science The method for producing graphene was to apply a thin layer of graphite to adhesive tape and then remove the base. This technique is called the “Scotch tape technique.” However, scientists have recently discovered that there is a more efficient way to obtain a new material: they began to use a layer of copper, nickel or silicon as a base, which is then removed by etching (Fig. 2). In this way, rectangular sheets of graphene 76 centimeters wide were created by a team of scientists from Korea, Japan and Singapore. Not only did the researchers set a kind of record for the size of a piece of a single-layer structure made of carbon atoms, but they also created sensitive screens based on flexible sheets.
Figure 2: Obtaining graphene by etching method
Physicists first obtained graphene “flakes” only in 2004, when their size was only 10 micrometers. A year ago, Rodney Ruoff’s team from the University of Texas at Austin announced that they had managed to create centimeter-sized “scraps” of graphene.
Ruoff and his colleagues deposited carbon atoms on copper foil using chemical vapor deposition (CVD). Researchers in the laboratory of Professor Byun Hee Hong from Sunghyunkwan University went further and enlarged the sheets to the size of a full screen. The new “roll-to-roll” technology (roll-to-roll processing) makes it possible to produce a long ribbon from graphene (Fig. 3).
Figure 3: High-resolution transmission electron microscopy image of stacked graphene layers.
The physicists placed a layer of adhesive polymer on top of the graphene sheets, dissolved the copper substrates, then separated the polymer film - a single layer of graphene was obtained. To give the sheets greater strength, scientists used the same method to “grow” three more layers of graphene. Finally, the resulting “sandwich” was treated with nitric acid to improve conductivity. A new sheet of graphene is placed on a polyester substrate and passed between heated rollers (Fig. 4).
Figure 4: Roll technology for producing graphene
The resulting structure transmitted 90% of light and had an electrical resistance lower than that of the standard, but still very expensive, transparent conductor - indium tin oxide (ITO). By the way, using graphene sheets as the basis of touch displays, researchers discovered that their structure is also less fragile.
True, despite all the achievements, the technology is still very far from commercialization. Transparent films from carbon nanotubes They have been trying to displace ITO for quite some time, but manufacturers cannot cope with the problem of “dead pixels” that appear on film defects.
Application of graphenes in electrical engineering and electronics
The brightness of pixels in flat panel screens is determined by the voltage between two electrodes, one of which faces the viewer (Fig. 5). These electrodes must be transparent. Currently, tin-doped indium oxide (ITO) is used to produce transparent electrodes, but ITO is expensive and not the most stable substance. In addition, the world will soon run out of indium. Graphene is more transparent and more stable than ITO, and an LCD display with a graphene electrode has already been demonstrated.
Figure 5: Brightness of graphene screens as a function of applied voltage
The material has great potential in other areas of electronics. In April 2008, scientists from Manchester demonstrated the world's smallest graphene transistor. A perfectly regular layer of graphene controls the resistance of the material, turning it into a dielectric. It becomes possible to create a microscopic power switch for a high-speed nano-transistor to control the movement of individual electrons. The smaller the transistors in microprocessors, the faster they are, and scientists hope that graphene transistors in future computers will become molecule-sized, given that current silicon microtransistor technology has almost reached its limit.
Graphene is not only an excellent conductor of electricity. It has the highest thermal conductivity: atomic vibrations easily propagate throughout the carbon mesh of the cellular structure. Heat dissipation in electronics is a serious issue because there are limits to the high temperatures that electronics can withstand. However, scientists from the University of Illinois have discovered that transistors using graphene have an interesting property. They exhibit a thermoelectric effect, leading to a decrease in the temperature of the device. This could mean that graphene-based electronics will make radiators and fans a thing of the past. Thus, the attractiveness of graphene as a promising material for future microcircuits further increases (Fig. 6).
Figure 6: An atomic force microscope probe scanning the surface of a graphene-metal contact to measure temperature.
Scientists have had a difficult time measuring graphene's thermal conductivity. They invented a completely new way to measure its temperature by placing a 3-micron-long film of graphene over exactly the same tiny hole in a silicon dioxide crystal. The film was then heated with a laser beam, causing it to vibrate. These vibrations helped calculate temperature and thermal conductivity.
The ingenuity of scientists knows no bounds when it comes to using the phenomenal properties of a new substance. In August 2007, the most sensitive of all possible sensors based on it was created. It is able to react to one molecule of gas, which will help to promptly detect the presence of toxins or explosives. Foreign molecules peacefully descend into the graphene network, knocking electrons out of it or adding them. As a result, the electrical resistance of the graphene layer changes, which is measured by scientists. Even the smallest molecules are trapped by the durable graphene mesh. In September 2008, scientists from Cornell University in the USA demonstrated how a graphene membrane, like a thin balloon, is inflated due to a pressure difference of several atmospheres on both sides. This feature of graphene can be useful in determining the occurrence of various chemical reactions and in general when studying the behavior of atoms and molecules.
Producing large sheets of pure graphene is still very difficult, but the task can be simplified if a layer of carbon is mixed with other elements. At Northwestern University in the USA, graphite was oxidized and dissolved in water. The result was a paper-like material - graphene oxide paper (Fig. 7). It is very tough and quite easy to make. Graphene oxide is useful as a strong membrane in batteries and fuel cells.
Figure 7: Graphene oxide paper
A graphene membrane is an ideal substrate for objects to be studied under an electron microscope. Flawless cells merge in the images into a uniform gray background, against which other atoms clearly stand out. Until now, it was almost impossible to distinguish the lightest atoms in an electron microscope, but with graphene as a substrate, even small hydrogen atoms can be seen.
The possibilities for using graphene can be listed endlessly. Recently, physicists at Northwestern University in the USA discovered that graphene can be mixed with plastic. The result is a thin, super-strong material that can withstand high temperatures and is impervious to gases and liquids.
Its scope of application is the production of lightweight gas stations, spare parts for cars and aircraft, and durable wind turbine blades. You can package food products in plastic, keeping them fresh for a long time.
Graphene is not only the thinnest, but also the strongest material in the world. Scientists at Columbia University in New York verified this by placing graphene over tiny holes in a silicon crystal. Then, by pressing a very thin diamond needle, they tried to destroy the graphene layer and measured the pressure force (Fig. 8). It turned out that graphene is 200 times stronger than steel. If you imagine a graphene layer as thick as cling film, it would withstand the pressure of the tip of a pencil, on the opposite end of which an elephant or a car would balance.
Figure 8: Pressure on the graphene of a diamond needle
Graphene is a revolutionary material of the 21st century. It is the strongest, lightest and most electrically conductive version of the carbon compound.
Graphene was discovered by Konstantin Novoselov and Andrei Geim, working at the University of Manchester, for which Russian scientists were awarded Nobel Prize. To date, about ten billion dollars have been allocated to research the properties of graphene over ten years, and there are rumors that it could be an excellent replacement for silicon, especially in the semiconductor industry.
However, two-dimensional structures similar to this carbon-based material have been predicted for other elements. Periodic table chemical elements and very unusual properties One of these substances was recently studied. This substance is called “blue phosphorus”.
Russian immigrants working in Britain, Konstantin Novoselov and Andrey Geim created graphene - a translucent layer of carbon one atom thick - in 2004. From that moment on, almost immediately and everywhere, we began to hear laudatory odes about a variety of amazing properties of the material, which has the potential to change our world and find its application in a variety of areas, from the production of quantum computers to the production of filters for obtaining pure drinking water. 15 years have passed, but the world under the influence of graphene has not changed. Why?
All modern electronic devices use electrons to transmit information. Currently, the development of quantum computers is in full swing, which many consider to be a future replacement for traditional devices. However, there is another, no less interesting way of development. Creation of so-called photonic computers. And recently, a team of researchers from the University of Exeter () discovered a particle property that could help in the design of new computer circuits.
Graphene fibers under a scanning electron microscope. Pure graphene is reduced from graphene oxide (GO) in a microwave oven. Scale 40 µm (left) and 10 µm (right). Photo: Jieun Yang, Damien Voiry, Jacob Kupferberg / Rutgers University
Graphene is a 2D modification of carbon, formed by a layer one carbon atom thick. The material has high strength, high thermal conductivity and unique physical and chemical properties. It exhibits the highest electron mobility of any known material on Earth. This makes graphene an almost ideal material for a wide variety of applications, including electronics, catalysts, batteries, composite materials, etc. All that’s left to do is learn how to produce high-quality graphene layers on an industrial scale.
Chemists from Rutgers University (USA) have found a simple and fast method for producing high-quality graphene by treating graphene oxide in a conventional microwave oven. The method is surprisingly primitive and effective.
Graphite oxide is a compound of carbon, hydrogen and oxygen in various proportions, which is formed when graphite is treated with strong oxidizing agents. To get rid of the remaining oxygen in graphite oxide and then obtain pure graphene in two-dimensional sheets requires considerable effort.
Graphite oxide is mixed with strong alkalis and the material is further reduced. The result is monomolecular sheets with oxygen residues. These sheets are commonly called graphene oxide (GO). Chemists have tried different ways removing excess oxygen from GO ( , , , ), but GO (rGO) reduced by such methods remains a highly disordered material, which in its properties is far from real pure graphene obtained by chemical vapor deposition (CVD or CVD).
Even in its disordered form, rGO has the potential to be useful for energy carriers ( , , , , ) and catalysts ( , , , ), but to extract maximum benefit from unique properties graphene in electronics, you need to learn how to obtain pure high-quality graphene from GO.
Chemists at Rutgers University propose a simple and fast way to reduce GO to pure graphene using 1-2 second pulses of microwave radiation. As can be seen in the graphs, graphene obtained by “microwave reduction” (MW-rGO) is much closer in its properties to the purest graphene obtained using CVD.
Physical characteristics of MW-rGO compared with pristine graphene oxide GO, reduced graphene oxide rGO, and chemical vapor deposition (CVD) graphene. Shown are typical GO flakes deposited on a silicon substrate (A); X-ray photoelectron spectroscopy (B); Raman spectroscopy and crystal size ratio (L a) to l 2D /l G peak ratio in the Raman spectrum for MW-rGO, GO and CVD (CVD).
Electronic and electrocatalytic properties of MW-rGO compared to rGO. Illustrations: Rutgers University
The technological process for obtaining MW-rGO consists of several stages.
- Oxidation of graphite using the modified Hummers method and dissolving it into single-layer graphene oxide flakes in water.
- Annealing GO to make the material more susceptible to microwave irradiation.
- Irradiate GO flakes in a conventional 1000 W microwave oven for 1-2 seconds. During this procedure, GO is quickly heated to a high temperature, desorption of oxygen groups and excellent structuring of the carbon lattice occurs.
Transmission electron microscope images show the structure of graphene sheets with a scale of 1 nm. On the left is single-layer rGO, which has many defects, including oxygen functional groups (blue arrow) and holes in the carbon layer (red arrow). In the center and on the right are perfectly structured two-layer and three-layer MW-rGO. Photo: Rutgers University
The excellent structural properties of MW-rGO when used in field-effect transistors allow the maximum electron mobility to be increased to approximately 1500 cm 2 /V s, which is comparable to the outstanding performance of modern high electron mobility transistors.
In addition to electronics, MW-rGO is useful in the production of catalysts: it showed exceptional small value Tafel coefficient when used as a catalyst in the oxygen evolution reaction: approximately 38 mV per decade. The MW-rGO catalyst also remained stable in the hydrogen evolution reaction, which lasted for more than 100 hours.
All this suggests excellent potential for the use of microwave-reduced graphene in industry.
Research Article "High-quality graphene via microwave reduction of solution-exfoliated graphene oxide" published on September 1, 2016 in the magazine Science(doi: 10.1126/science.aah3398).
High technology at home. Nobel Prize winner Konstantin Novoselov told how you can make graphene yourself from scrap materials. It has created a real sensation in the world of science, and in the future it can be used in all areas - from cooking to space flights.
Building a stage for a Nobel laureate is, of course, not inventing graphene. The screen for displaying photo and video slides was assembled in just a few minutes. Frame, fastenings and here it is, the magic of minimalism. Equipment for telling the loudest scientific discovery Recently, Konstantin Novoselov brought it with him in an ordinary backpack.
There was a laptop inside. The Nobel Prize winner in physics is used to traveling light. The first question from the audience - and immediately an answer that excites the imagination. It turns out that almost anyone can get material that is predicted to have a great future.
"All you need is to buy good graphite. In principle, you can use pencils, but it's better to buy good graphite. You'll spend $100 on that. You'll have to spend $20 on silicon wafers, $1 on tape. That's $121 dollar, I promise you that you will learn how to make amazing graphene,” the scientist said.
It is no coincidence that the world of science immediately said about this discovery: everything ingenious is simple. Graphite-based material could revolutionize electronics. We are already accustomed to the fact that modern gadgets are mobile phone, both a computer and a camera in one device. With graphene, these devices will become much thinner, and also transparent and flexible. Thanks to unique features matter, such a device is not scary to drop.
“It has very interesting electronic properties. It can be used for transistors. And, in particular, many companies are trying to make high-speed transistors from this material to use, for example, in mobile communications,” he explained Nobel laureate.
In the future, according to experts, this material will be able to completely replace gradually aging silicon in all electronic devices. So far this technique seems like a miracle. However, more recently, the same surprise was caused, for example, by LCD TVs or the Internet. By the way, the Worldwide Computer Network using graphene will become tens of times faster. In biology, along with new material, progressive technologies for deciphering the chemical structure of DNA will appear. The use of ultra-light and high-strength graphene will find application in aviation and construction spaceships.
“The material that is the thinnest, the strongest, the most conductive. The most impenetrable, the most elastic. In general, the very best, this will be graphene,” Novoselov emphasized.
The Nobel Prize in Physics was awarded for advanced experiments with graphene in 2010. This is the first time that a material turned product scientific research, so quickly moves from academic laboratories to industrial production. In Russia, interest in the developments of Konstantin Novoselov is exceptional. The site of the Bookmarket festival and Gorky Park is open to everyone. And cool weather and rain are not a hindrance to real science.