How to create graphene at home. Graphene: new production methods and recent achievements. Receipt at home

12.12.2022

High tech at home. Laureate Nobel Prize 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.

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 take full advantage of graphene's unique properties in electronics, one must learn to produce 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.

Photography with a transmission electron microscope shows that after treatment with a microwave emitter, a highly ordered structure is formed in which oxygen functional groups are almost completely destroyed.

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).

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 to remove excess oxygen from GO ( , , , ), but GO (rGO) reduced by these methods remains a highly disordered material that is far from the properties of real pure graphene obtained by chemical vapor deposition (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.

In addition to electronics, MW-rGO is useful in the production of catalysts: it has shown an exceptionally low 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).

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, in 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 belongs to the class of unique carbon compounds with remarkable chemical and physical properties, such as excellent electrical conductivity, which is combined with amazing lightness and strength.

It is expected that over time it will be able to replace silicon, which is the basis of modern semiconductor production. Currently, this compound has firmly secured the status of “material of the future.”

Features of the material

Graphene, most often found under the designation “G,” is a two-dimensional form of carbon that has an unusual structure in the form of atoms connected in a hexagonal lattice. Moreover, its total thickness does not exceed the size of each of them.

For a clearer understanding of what graphene is, it is advisable to familiarize yourself with such unique characteristics as:

Record high thermal conductivity;
High mechanical strength and flexibility of the material, hundreds of times higher than the same indicator for steel products;
Incomparable electrical conductivity;
High melting point (more than 3 thousand degrees);
Impenetrability and transparency.

The unusual structure of graphene is evidenced by this simple fact: when combining 3 million sheets of graphene blanks, the total thickness of the finished product will be no more than 1 mm.

To understand the unique properties of this unusual material, it is enough to note that in its origin it is similar to ordinary layered graphite used in pencil lead. However, due to the special arrangement of atoms in the hexagonal lattice, its structure acquires the characteristics inherent in such a hard material as diamond.

When graphene is isolated from graphite, its most “miraculous” properties, characteristic of modern 2D materials, are observed in the resulting film atom thick. Today it is difficult to find such an area National economy, wherever this unique compound is used and where it is considered promising. This is especially evident in the field of scientific development, which aims to develop new technologies.

Methods of obtaining

The discovery of this material can be dated back to 2004, after which scientists mastered various methods for obtaining it, which are presented below:

Chemical cooling implemented by the phase transformation method (it is called the CVD process);
The so-called “epitaxial growth”, carried out under vacuum conditions;
“Mechanical exfoliation” method.

Let's look at each of them in more detail.

Mechanical

Let's start with the last of these methods, which is considered the most accessible for independent implementation. In order to obtain graphene at home, it is necessary to sequentially perform the following series of operations:

First you need to prepare a thin graphite plate, which is then attached to the adhesive side of a special tape;
After this, it folds in half and then returns to its original state (its ends move apart);
As a result of such manipulations, it is possible to obtain on the adhesive side of the tape double layer graphite;
If you perform this operation several times, it will not be difficult to achieve a small thickness of the applied layer of material;
After this, adhesive tape with split and very thin films is applied to the silicon oxide substrate;
As a result, the film partially remains on the substrate, forming a graphene layer.

The disadvantage of this method is the difficulty of obtaining a sufficiently thin film of a given size and shape that would be reliably fixed on the designated parts of the substrate.

Currently, most of the graphene used in everyday practice is produced in this way. Due to mechanical exfoliation, it is possible to obtain a fairly high quality compound, but for conditions mass production This method is completely unsuitable.

Industrial methods

One of the industrial methods for producing graphene is growing it in a vacuum, the features of which can be represented as follows:

To make it, a surface layer of silicon carbide is taken, which is always present on the surfaces of this material;
Then the pre-prepared silicon wafer is heated to a relatively high temperature (about 1000 K);
Due to the chemical reactions occurring in this case, the separation of silicon and carbon atoms is observed, in which the first of them immediately evaporate;
As a result of this reaction, pure graphene (G) remains on the plate.

The disadvantages of this method include the need for high-temperature heating, which often poses technical difficulties.

The most reliable industrial method that avoids the difficulties described above is the so-called “CVD process”. When it is implemented, it occurs chemical reaction flowing on the surface of a metal catalyst when it is combined with hydrocarbon gases.

As a result of all the approaches discussed above, it is possible to obtain pure allotropic compounds of two-dimensional carbon in the form of a layer only one atom thick. A feature of this formation is the connection of these atoms into a hexagonal lattice due to the formation of so-called “σ” and “π” bonds.

Carriers electric charge in the graphene lattice are characterized by a high degree of mobility, significantly exceeding this indicator for other known semiconductor materials. It is for this reason that it is able to replace classic silicon, traditionally used in the production of integrated circuits.

Possibilities practical application graphene-based materials are directly related to the features of its production. Currently, many methods are practiced for obtaining individual fragments of it, differing in shape, quality and size.

Among all the known methods, the following approaches stand out:

Production of a variety of graphene oxide in the form of flakes, used in the production of electrically conductive paints, as well as various types of composite materials;
Obtaining flat graphene G, from which components of electronic devices are made;
Growing the same type of material used as inactive components.

The main properties of this compound and its functionality are determined by the quality of the substrate, as well as the characteristics of the material with which it is grown. All this ultimately depends on the method of its production used.

Depending on the method of obtaining this unique material, it can be used for a variety of purposes, namely:

Graphene obtained by mechanical exfoliation is mainly intended for research, which is explained by the low mobility of free charge carriers;
When graphene is produced by a chemical (thermal) reaction, it is most often used to create composite materials, as well as protective coatings, inks, and dyes. Its mobility of free carriers is somewhat higher, which makes it possible to use it for the manufacture of capacitors and film insulators;
If the CVD method is used to obtain this compound, it can be used in nanoelectronics, as well as for the manufacture of sensors and transparent flexible films;
Graphene obtained by the “silicon wafers” method is used to manufacture elements of electronic devices such as RF transistors and similar components. The mobility of free charge carriers in such compounds is maximum.

The listed features of graphene open up broad horizons for manufacturers and allow them to concentrate efforts on its implementation in the following promising areas:

In alternative areas of modern electronics related to the replacement of silicon components;
In leading chemical industries;
When designing unique products (such as composite materials and graphene membranes);
In electrical engineering and electronics (as an “ideal” conductor).

In addition, cold cathodes, rechargeable batteries, as well as special conductive electrodes and transparent film coatings can be manufactured based on this compound. Unique properties This nanomaterial provides it with a large supply of possibilities for its use in promising developments.

Advantages and disadvantages

Advantages of graphene-based products:

High degree of electrical conductivity, comparable to that of ordinary copper;
Almost perfect optical purity, thanks to which it absorbs no more than two percent of the visible light range. Therefore, from the outside it appears almost colorless and invisible to the observer;
Mechanical strength superior to diamond;
Flexibility, in terms of which single-layer graphene is superior to elastic rubber. This quality allows you to easily change the shape of the films and stretch them if necessary;
Resistance to external mechanical influences;
Incomparable thermal conductivity, in terms of which it is tens of times higher than that of copper.

The disadvantages of this unique carbon compound include:

The impossibility of obtaining in volumes sufficient for industrial production, as well as achieving the physical and chemical properties required to ensure high quality. In practice, it is possible to obtain only small-sized sheet fragments of graphene;
Industrially manufactured products are most often inferior in their characteristics to samples obtained in research laboratories. It is not possible to achieve them using ordinary industrial technologies;
High non-labor costs, which significantly limit the possibilities of its production and practical application.

Despite all these difficulties, researchers do not abandon their attempts to develop new technologies for the production of graphene.

In conclusion, it should be stated that the prospects for this material are simply fantastic, since it can also be used in the production of modern ultra-thin and flexible gadgets. In addition, on its basis it is possible to create modern medical equipment and drugs that can fight cancer and other common tumor diseases.

How to create graphene at home. Graphene: new production methods and recent achievements. Receipt at home

Application of graphenes in electrical engineering and electronics

Features of the material

Methods of obtaining

Mechanical

Industrial methods

Advantages and disadvantages

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