Quantum dots are nanoscale sensors for medicine and biology. Quantum dot LED is a new display technology

COURSE WORK

in the discipline "Biomedical transducers and sensory systems"

Quantum dots and biosensors based on them

Introduction. 3

Quantum dots. General information. five

Classification of quantum dots. 6

Photoluminescent quantum dots. nine

Obtaining quantum dots. eleven

Biosensors using quantum dots. Prospects for their application in clinical diagnostics. 13

Conclusion. 15

Bibliography. sixteen

Introduction.

Quantum dots (QDs) are isolated nanoobjects whose properties differ significantly from those of a bulk material of the same composition. It should be noted right away that quantum dots are rather a mathematical model than real objects. And this is due to the impossibility of forming completely isolated structures - small particles always interact with the environment, being in a liquid medium or a solid matrix.

To understand what quantum dots are and understand their electronic structure, imagine an ancient Greek amphitheater. Now imagine that a fascinating performance is unfolding on the stage, and the audience is filled with an audience who has come to watch the actors play. So it turns out that the behavior of people in the theater is in many ways similar to the behavior of electrons in a quantum dot (QD). During the performance, the actors move around the arena without leaving the audience, while the audience themselves watch the action from their seats and do not go down to the stage. The arena is the lower filled levels of the quantum dot, and the rows of spectators are the higher energy excited electronic levels. At the same time, as the viewer can be in any row of the hall, so the electron is able to occupy any energy level of a quantum dot, but cannot be located between them. Buying tickets to the show at the box office, everyone tried to get the best seats - as close to the stage as possible. Indeed, who would want to sit in the last row, from where the actor's face cannot be seen even through binoculars! Therefore, when the spectators sit down before the start of the performance, all the lower rows of the hall are filled, just as in the stationary state of the QD, which has the lowest energy, the lower energy levels are completely occupied by electrons. However, during the performance, one of the spectators may leave their place, for example, because the music on the stage is playing too loudly or simply an unpleasant neighbor is caught, and move to the free top row. Similarly, in a QD, an electron under the action of an external influence is forced to move to a higher energy level not occupied by other electrons, leading to the formation of an excited state of a quantum dot. You are probably wondering what happens to that empty space at the energy level where the electron used to be - the so-called hole? It turns out that through charge interactions the electron remains connected to it and can go back at any moment, just as a retired viewer can always change his mind and return to the place indicated in his ticket. The electron-hole pair is called an “exciton” from the English word “excited”, which means “excited”. Migration between the energy levels of QD, similar to the ascent or descent of one of the spectators, is accompanied by a change in the energy of the electron, which corresponds to the absorption or emission of a quantum of light (photon) when the electron moves to a higher or lower level, respectively. The behavior of electrons in a quantum dot described above leads to a discrete energy spectrum uncharacteristic for macroobjects, for which quantum dots are often called artificial atoms, in which the electron levels are discrete.

The strength (energy) of the bond between the hole and the electron determines the exciton radius, which is a characteristic quantity for each substance. If the particle size is less than the exciton radius, then the exciton is limited in space by its size, and the corresponding binding energy changes significantly in comparison with bulk matter (see "quantum size effect"). It is not difficult to guess that if the exciton energy changes, then the energy of the photon emitted by the system also changes during the transition of the excited electron to its original place. Thus, by obtaining monodisperse colloidal solutions of nanoparticles of various sizes, it is possible to control the transition energies in a wide range of the optical spectrum.

Quantum dots. General information.

The first quantum dots were metal nanoparticles, which were synthesized back in ancient Egypt for coloring various glasses (by the way, the Kremlin's ruby \u200b\u200bstars were obtained using a similar technology), although semiconductor GaN particles and colloidal solutions of CdSe nanocrystals grown on substrates are more traditional and widely known QDs. Currently, there are many ways to obtain quantum dots, for example, they can be "cut" from thin layers of semiconductor "heterostructures" using "nanolithography", and can be spontaneously formed in the form of nanoscale inclusions of structures of one type of semiconductor material in the matrix of another. With a significant difference in the parameters of the unit cell of the substrate and the deposited layer, it is possible to grow pyramidal quantum dots on the substrate by the method of "molecular beam epitaxy", for the study of the properties of which Academician Zh.I. Alferov was awarded the Nobel Prize. By controlling the conditions of the synthesis processes, it is theoretically possible to obtain quantum dots of certain sizes with desired properties.

Quantum dots are available both as cores and as core-shell heterostructures. Due to their small size, QDs have properties that differ from bulk semiconductors. The spatial limitation of the motion of charge carriers leads to the quantum-size effect, which is expressed in the discrete structure of electronic levels, which is why QDs are sometimes called “artificial atoms”.

Quantum dots exhibit photoluminescence in the visible and near infrared ranges, depending on their size and chemical composition. Due to high uniformity in size (more than 95%), the proposed nanocrystals have narrow emission spectra (half-width of the fluorescence peak 20-30 nm), which provides phenomenal color purity.

Quantum dots can be supplied as solutions in non-polar organic solvents such as hexane, toluene, chloroform, or as dry powders.

CTs are still a “young” object of research, but the broad prospects of their use for the design of new generation lasers and displays are already quite obvious. The optical properties of CT are used in the most unexpected fields of science, which require tunable luminescent properties of the material, for example, in medical research, they make it possible to “illuminate” diseased tissues.

Classification of quantum dots.

Colloidal synthesis of quantum dots presents ample opportunities both in obtaining quantum dots based on various semiconductor materials and quantum dots with different geometry (shape). The possibility of synthesizing quantum dots composed of different semiconductors is also important. Colloidal quantum dots will be characterized by composition, size, shape.

Quantum dots composition (semiconductor material)

First of all, quantum dots are of practical interest as luminescent materials. The main requirements for semiconductor materials on the basis of which quantum dots are synthesized are as follows. First of all, this is the direct-gap nature of the band spectrum - it provides effective luminescence, and secondly, the low effective mass of charge carriers - the manifestation of quantum-size effects in a fairly wide range of sizes (of course, by the standards of nanocrystals). The following classes of semiconductor materials can be distinguished. Wide-gap semiconductors (oxides ZnO, TiO2) - ultraviolet range. Mid-season semiconductors (A2B6, for example, cadmium chalcogenides, A3B5) - visible range.

The ranges of variation of the effective bandgap of quantum dots at

change in size from 3 to 10 nm.

The figure shows the possibility of varying the effective band gap for the most common semiconductor materials in the form of nanocrystals with a size in the range of 3-10 nm. From a practical point of view, important optical ranges are visible 400-750 nm, near-IR 800-900 nm - blood transparency window, 1300-1550 nm - telecommunication range

Quantum dot shape

In addition to composition and size, the shape of quantum dots will also have a significant impact on their properties.

- Spherical (directly quantum dots) - most of the quantum dots. At the moment they have the greatest practical application. The easiest to manufacture.

- Ellipsoidal(nanorods) - nanocrystals, elongated along one direction.

Ellipticity coefficient 2-10. The indicated boundaries are conditional. From a practical point of view, this class of quantum dots is used as sources of polarized radiation. With high ellipticity coefficients\u003e 50, this type of nanocrystal is often called nanowires.

- Nanocrystals with complex geometry (like tetrapods). A sufficient variety of shapes can be synthesized - cubic, asterisks, etc., as well as branched structures. From a practical point of view, tetrapods can be used as molecular switches. At the moment, they are of great academic interest.

Multicomponent quantum dots

Colloidal chemistry methods make it possible to synthesize multicomponent quantum dots from semiconductors with different characteristics, primarily with different bandgaps. This classification is largely similar to that traditionally used in semiconductors.

Doped quantum dots

As a rule, the amount of the introduced impurity is small (1-10 atoms per quantum dot with an average number of atoms in a quantum dot of 300-1000). In this case, the electronic structure of the quantum dot does not change, the interaction between the impurity atom and the excited state of the quantum dot is dipole and is reduced to the transfer of excitation. The main dopants are manganese, copper (luminescence in the visible range).

Solid-solution quantum dots.

For quantum dots, the formation of solid solutions of semiconductors is possible if the mutual solubility of materials in the bulk state is observed. As in the case of bulk semiconductors, the formation of solid solutions leads to a modification of the energy spectrum - the effective characteristics are a superposition of values \u200b\u200bfor individual semiconductors. This approach allows you to change the effective bandgap at a fixed size - it provides another way to control the characteristics of quantum dots.

Quantum dots based on heterojunctions.

This approach is implemented in quantum dots of the core-shell type (a core from one semiconductor, a shell from another). In general, it involves the formation of a contact between two parts from different semiconductors. By analogy with the classical theory of heterojunctions, two types of core-shell quantum dots can be distinguished.

Photoluminescent quantum dots.

Of particular interest are photoluminescent quantum dots, in which the absorption of a photon gives rise to electron-hole pairs, and the recombination of electrons and holes causes fluorescence. Such quantum dots have a narrow and symmetrical fluorescence peak, the position of which is determined by their size. Thus, depending on the size and composition, QDs can have fluorescence in the UV, visible, or IR spectral regions.

Quantum dots based on cadmium chalcogenides, depending on their size, fluoresce in different colors

For example, quantum dots ZnS, CdS and ZnSe fluoresce in the UV region, CdSeand CdTe in visible, and PbS, PbSe and PbTe in the near IR - region (700-3000 nm). In addition, the above compounds can be used to create heterostructures whose optical properties may differ from those of the initial compounds. The most popular is to grow the shell of a wider-gap semiconductor onto a core from a narrow-gap semiconductor, for example, onto a core CdSe build up the shell from ZnS :

Model of the structure of a quantum dot consisting of a CdSe core covered with a ZnS epitaxial shell (sphalerite structure type)

This technique makes it possible to significantly increase the stability of QDs to oxidation, as well as to significantly increase the quantum yield of fluorescence by reducing the number of defects on the surface of the nucleus. A distinctive feature of QDs is a continuous absorption (fluorescence excitation) spectrum in a wide wavelength range, which also depends on the QD size. This makes it possible to simultaneously excite different quantum dots at the same wavelength. In addition, CT scans have a higher brightness and better photostability than traditional fluorophores.

Such unique optical properties of quantum dots open up broad prospects for their use as optical sensors, fluorescent markers, photosensitizers in medicine, as well as for the manufacture of infrared photodetectors, high efficiency solar cells, subminiature LEDs, white light sources, single-electron transistors and nonlinear -optical devices.

Obtaining quantum dots

There are two main methods for producing quantum dots: colloidal synthesis, carried out by mixing precursors "in a flask", and epitaxy, i.e. oriented crystal growth on the substrate surface.

The first method (colloidal synthesis) is implemented in several versions: at high or room temperature, in an inert atmosphere in organic solvents or in an aqueous solution, with or without organometallic precursors, with or without molecular clusters facilitating nucleation. High-temperature chemical synthesis is also used, carried out in an inert atmosphere by heating inorganic precursors dissolved in high-boiling organic solvents. This makes it possible to obtain quantum dots of uniform size with a high quantum yield of fluorescence.

As a result of colloidal synthesis, nanocrystals are obtained, covered with a layer of adsorbed surface-active molecules:

Schematic representation of a colloidal quantum dot of the core-shell type with a hydrophobic surface. Orange shows the core of a narrow-gap semiconductor (for example, CdSe), red - a shell of a wide-gap semiconductor (for example, ZnS), black - an organic shell of surface-active molecules.

Due to the hydrophobic organic shell, colloidal quantum dots can be dissolved in any non-polar solvents, and, with appropriate modification, in water and alcohols. Another advantage of colloidal synthesis is the ability to produce quantum dots in sub-kilogram quantities.

The second method (epitaxy) - the formation of nanostructures on the surface of another material, as a rule, is coupled with the use of unique and expensive equipment and, moreover, leads to the production of quantum dots, "bound" to the matrix. The epitaxy method is difficult to scale to an industrial level, which makes it less attractive for mass production of quantum dots.

Biosensors using quantum dots. Prospects for their application in clinical diagnostics.

Quantum dot - a very small physical object, the size of which is less than the radius of the Bohr exciton, which leads to the appearance of quantum effects, for example, strong fluorescence.

The advantage of quantum dots is that they can be excited by a single radiation source. Depending on their diameter, they shine with different light, and one source excites quantum dots of all colors.

At the Institute of Bioorganic Chemistry. academicians M.M. Shemyakin and Yu.A. Ovchinnikov RAS produce quantum dots in the form of colloidal nanocrystals, which allows them to be used as fluorescent labels. They are very bright, even with an ordinary microscope, individual nanocrystals can be seen. In addition, they are photo-resistant - they can glow for a long time when exposed to high power density radiation.

The advantage of quantum dots is that, depending on the material from which they are made, fluorescence can be obtained in the infrared range where biological tissues are most transparent. At the same time, the efficiency of fluorescence in them is incomparable with any other fluorophores, which makes it possible to use them for visualization of various formations in biological tissues.

Using the example of diagnosing an autoimmune disease - systemic sclerosis (scleroderma) - the possibility of quantum dots in clinical proteomics was demonstrated. Diagnostics is based on the registration of autoimmune antibodies.

In autoimmune diseases, the body's own proteins begin to affect their own biological objects (cell walls, etc.), which causes severe pathology. At the same time, autoimmune antibodies appear in biological fluids, which they used to diagnose and detect autoantibodies.

There are a number of antibodies to scleroderma. The diagnostic capabilities of quantum dots were demonstrated using two antibodies as an example. Antigens to autoantibodies were applied to the surface of polymer microspheres containing quantum dots of a given color (each antigen had its own color of the microsphere). The test mixture contained, in addition to microspheres, secondary antibodies bound to a signaling fluorophore. Next, a sample was added to the mixture, and if it contained the desired autoantibody, a complex was formed in the mixture microsphere - autoanbody - signaling fluorophore.

Essentially, the autoantibody was a linker that binds a colored microsphere to a signaling fluorophore. These microspheres were then analyzed by flow cytometry. The appearance of a simultaneous signal from the microsphere and a signaling fluorophore is evidence that binding has occurred and a complex has formed on the surface of the microsphere, which includes secondary antibodies with a signaling fluorophore. At this moment, crystals of microspheres and a signaling fluorophore that was bound to the secondary antibody actually shone.

The simultaneous appearance of both signals indicates that a detectable target is present in the mixture - an autoantibody, which is a disease marker. This is a classic "sandwich" registration method, when there are two recognition molecules, i.e. the possibility of simultaneous analysis of several markers was demonstrated, which is the basis for high diagnostic reliability and the possibility of creating drugs that allow determining the disease at the earliest stage

Use as biomarkers.

The creation of fluorescent labels based on quantum dots is very promising. The following advantages of quantum dots over organic dyes can be distinguished: the ability to control the luminescence wavelength, high extinction coefficient, solubility in a wide range of solvents, stability of luminescence to the action of the environment, and high photostability. It is also possible to note the possibility of chemical (or, moreover, biological) modification of the surface of quantum dots, which allows for selective binding with biological objects. The right figure shows the staining of cell elements using water-soluble quantum dots, luminescent in the visible range. The left figure shows an example of using non-destructive optical tomography. The photograph was taken in the near-infrared range using quantum dots with luminescence in the range of 800-900 nm (blood transparency window of warm-blooded animals) injected into a mouse.

Fig. 21. Using quantum dots as biolabels.

Conclusion.

Currently, medical applications using quantum dots are still limited, due to the fact that the effect of nanoparticles on human health has not been sufficiently studied. However, their use in the diagnosis of dangerous diseases seems to be very promising, in particular, on their basis, a method of immunofluorescence analysis has been developed. And in the treatment of oncological diseases, for example, the method of the so-called photodynamic therapy is already being used. Nanoparticles are injected into the tumor, then they are irradiated, and then this energy is transferred from them to oxygen, which turns into an excited state and “burns out” the tumor from the inside.

Biologists say it's easy to design quantum dots to respond at any wavelength, such as the near infrared spectrum. Then it will be possible to find tumors hidden deep inside the body.

In addition, certain nanoparticles can give a characteristic response in magnetic resonance imaging.

Further plans of the researchers look even more tempting. New quantum dots, connected to a set of biomolecules, will not only find a tumor and indicate it, but also deliver new generations of drugs exactly in place.

It is possible that this application of nanotechnology will be the closest to the practical and mass implementation of what we have seen in laboratories in recent years.

Another direction is optoelectronics and LEDs of a new type - economical, miniature, bright. It uses such advantages of quantum dots as their high photostability (which guarantees the long-term operation of devices based on them) and the ability to provide any color (with an accuracy of one to two nanometers on the wavelength scale) and any color temperature (from 2 degrees Kelvin up to 10 thousand and above). In the future, based on LEDs, it is possible to make displays for monitors - very thin, flexible, with high image contrast.

Bibliography.

1.http: //www.nanometer.ru/2007/06/06/quantum_dots_2650.html

Tananaev PN, Dorofeev SG, Vasiliev RB, Kuznetsova TA .. Obtaining CdSe nanocrystals doped with copper // Inorganic materials. 2009. T. 45. No. 4. S. 393-398.
Oleinikov V.A., Sukhanova A.V., Nabiev I.R. Fluorescent semiconductor nanocrystals

in biology and medicine // Nano. - 2007 .-- S. 160 173.

Snee P.T., Somers R.C., Gautham N., Zimmer J.P., Bawendi M.G., Nocera D.G. A Ratiometric CdSe / ZnS Nanocrystal pH Sensor // J. Am. Chem. Soc .. - 2006. - V. 128. P. 13320 13321.
Kulbachinsky V. A. Semiconductor quantum dots // Soros educational journal. - 2001. - T. 7. - No. 4. - P. 98 - 104.

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Quantum dots are small crystals that emit light with a precisely controlled color value. They significantly improve image quality without affecting the final cost of the devices.

Quantum dot LED - new screen technology Conventional LCD TVs are capable of transmitting only 20-30% of the color range perceived by the human eye. The OLED display is more realistic, but the technology is not suitable for mass production of large displays. But recently a new one has come in its place, providing the ability to display accurate color values. We are talking about the so-called quantum dots. In early 2013, Sony introduced the first Quantum dot LED (QLED) TV. This year, other models of devices will be launched into mass production, while they will cost like conventional LCD TVs and significantly less than OLED solutions. What is the difference between displays produced using the new technology and standard LCD screens?

LCD TVs don't have solid colors

Liquid crystal displays are made up of five layers: the reference point is white light emitted from LEDs and passed through several filters. Front and rear polarizing filters, in combination with liquid crystals, regulate the transmitted light output, decreasing or increasing brightness. This is possible thanks to the pixel transistors, which affect how much light passes through the light filters (red, green, blue). The combination of the colors of these three subpixels, which are filtered, ultimately give a specific color value for the pixel. Color mixing is not a problem, but pure red, green, or blue cannot be achieved this way. The reason here lies in the filters that transmit not one wave of a certain length, but a whole beam of different wavelengths. For example, orange light also passes through a red filter.

The LED glows when voltage is applied to it. This allows electrons to be transferred from the N-type material to the P-type material. N-type material contains atoms with excess electrons. P-type material contains atoms that lack electrons. When excess electrons hit the latter, they release energy in the form of light. In a typical semiconductor crystal, this is typically white light produced by many different wavelengths. The reason for this is that electrons can be at different energy levels. Therefore, the emitted photons have different energies, which is expressed in different radiation wavelengths.

Quantum dots - stable light

In QLED displays, quantum dots - crystals several nanometers in size - act as a light source. At the same time, the need for a layer with light filters disappears, since when voltage is applied to them, the crystals always emit light with a clearly defined wavelength, and therefore a color value - the energy zone is reduced to one energy level. This effect is explained by the tiny size of a quantum dot, in which an electron, like in an atom, can only move in a limited space. As in an atom, an electron of a quantum dot can occupy only strictly defined energy levels. Due to the fact that these energy levels also depend on the material, it becomes possible to purposefully adjust the optical properties of quantum dots. For example, to obtain red, crystals of an alloy of cadmium, zinc and selenium (CdZnSe) are used, the sizes of which are about 10–12 nm. An alloy of cadmium and selenium is suitable for yellow, green and blue colors, the latter can also be obtained using nanocrystals from a compound of zinc and sulfur with a size of 2–3 nm.

Due to the complexity and cost involved in mass-producing blue crystals, the TV presented by Sony is not a “pure” quantum dot QLED TV. At the back of the displays produced by QD Vision is a layer of blue LEDs, the light of which passes through a layer of red and green nanocrystals. As a result, they, in fact, replace the currently widespread light filters. This increases the color gamut by 50% compared to conventional LCD TVs, but falls short of the level of a “pure” QLED screen. The latter, in addition to a wider color gamut, have another advantage: they allow you to save energy, since there is no need for a layer with light filters. As a result, the front of the screen in QLED TVs also receives more light than conventional TVs, which only transmit about 5% of the light output.

Quantum Dots in HD TV

Our eyes are capable of seeing more colors than HDTVs can display. Displays based on quantum dots can change this situation. Quantum dots are tiny particles a few nanometers in diameter that emit light at one specific wavelength and always with the same color value. If we talk about the light filters used in modern TVs, they provide only washed out colors.

Screens without light filters

In modern TVs, the white light of LED lamps (backlight) becomes colored thanks to light filters. In a quantum dot display (QLED), color is generated directly at the light source. Systems for dimming by means of liquid crystals and polarization have not changed.

Light cells in comparison

In LEDs, electrons are transferred from an N-type material to a P-type material, releasing energy in the form of white light at different wavelengths. The filter forms the desired color. In QLED TVs, nanocrystals emit light with a specific wavelength, and therefore color.

Wider color gamut

Quantum dot displays are capable of displaying more natural colors (red, green, blue) than traditional televisions, covering a wider color range that is closest to our color perception.

Size and material determine the color

When an electron (e) combines with a quantum dot, energy is released in the form of photons (P). By using various materials and changing the size of nanocrystals, it is possible to influence the value of this energy and, as a consequence, the length of the light wave.

« Quantum dots are artificial atoms whose properties can be controlled»

J.I. Alferov, 2000 Nobel Prize Laureate in physics for the development of semiconductor heterostructures for high-speed and optoelectronics

Quantum dots are still a "young" object of research, but the broad prospects of their use for the design of new generation lasers and displays are already quite obvious. The optical properties of CT are used in the most unexpected fields of science, which require tunable luminescent properties of the material, for example, in medical research, they make it possible to “illuminate” diseased tissues. People who dream of "quantum computers" see quantum dots as promising candidates for constructing qubits.

Literature

N. Kobayashi. Introduction to nanotechnology. M .: BINOM. Knowledge laboratory, 2007, 134 p.

V. Ya. Demikhovsky, G.A. Vugalter Physics of quantum low-dimensional structures. M .: Logos, 2000.

Any substance of microscopic size is a nanoparticle, a material used by nanotechnology researchers to develop and create new technologies based on the use of elements in this tiny form. We read carefully, because we will need to delve into the essence of the text a little.

Quantum dots are nanoparticles made from any semiconductor material, such as silicon, cadmium selenide, cadmium sulfide, or indium arsenide, that glow in a specific color when illuminated with light.

The color with which they glow depends on the size of the nanoparticle. By placing quanta of different sizes, you can achieve the presence of red, green and blue in each pixel of the display screen, which will make it possible to create a full spectrum of colors in these pixels (any existing color is obtained by mixing these colors).

When quantum dots are illuminated with UV light, some of the electrons receive enough energy to free themselves from atoms. This ability allows them to move around the nanoparticle, creating a conduction zone in which electrons can freely move through the material and conduct electricity.

When electrons descend into the outer orbit around an atom (valence band), they emit light. The color of this light depends on the energy difference between the conduction and valence bands.

The smaller the nanoparticle, the higher the energy difference between the valence and conduction bands, resulting in a deeper blue color. For a larger nanoparticle, the difference in energy between the valence and conduction bands is lower, which shifts the glow towards red.

Quantum Dots and Displays

For LCDs, the benefits are numerous. Let's take a look at the most important and interesting features that have gotten LCD screens from quantum dots.

Higher peak brightness

One of the reasons manufacturers are so thrilled about quantum dots is the ability to create screens with much higher peak brightness than other technologies. In turn, the increased peak brightness provides much greater scope for HDR and Dolby Vision.

Dolby Vision is a video image standard that has a high dynamic range, that is, a very large difference in light between the brightest and darkest point on the screen, which makes the picture more realistic and contrasting.

If you do not know, the developers are constantly trying to play the Lord God and create what he created (well, or who created all this around us, maybe the universe?), Only to transfer it to the screen.

That is, for example, a normal sky on a clear day has a brightness of about 20,000 nits (a unit of brightness), while the best TVs can deliver about 10 less brightness. So, the Dolby Vision standard is still ahead of the rest, but they are still very far from the Creator :)

Accordingly, screens based on quantum dots are another step towards a brighter image. Perhaps someday we will be able to see an almost real sunrise and / or sunset, or maybe other unique wonders of nature, without leaving home.

Better color rendering

Another great benefit of quantum dots is the improved color accuracy. Since each pixel has a CT of red, blue and green, this gives you access to the full palette of colors, which, in turn, allows you to achieve an incredible number of shades of any color.

Improved battery life for mobile devices

Quantum dot screens promise not only superb picture quality, but also extremely low power consumption.

Quantum Dots and Samsung QLED

Samsung's quantum dot TVs, or simply, are actually not really quantum dots in the correct understanding of this technology. QLED is more of a hybrid, something in between quantum dots and LED screens. Why? Because these TVs still use LED backlighting, and in a real screen on quantum dots, light must be created precisely by dots.

Therefore, even if the new TVs from the South Korean giant show better than conventional LED screens, they are still not quantum dot TVs, but quantum dot TVs instead of a light filter.

Comments:

Ivan Ivanovich

In order to get a general idea of \u200b\u200bthe properties of material objects and the laws according to which the macrocosm familiar to everyone "lives", it is not at all necessary to graduate from a higher educational institution, because every day everyone encounters their manifestations. Although recently the principle of similarity has been increasingly mentioned, the supporters of which argue that the micro and macrocosm are very similar, nevertheless, there is still a difference. This is especially noticeable with very small bodies and objects. Quantum dots, sometimes called nanodots, represent one of these cases.

Less less

Let's remember the classical structure of the atom, for example, hydrogen. It includes a nucleus, which, due to the presence of a positively charged proton in it, has a plus, that is, +1 (since hydrogen is the first element in the periodic table). Accordingly, an electron (-1) is located at a certain distance from the nucleus, forming an electron shell. Obviously, if you increase the value, then this will entail the addition of new electrons (recall: in general, the atom is electrically neutral).

The distance between each electron and the nucleus is determined by the energy levels of the negatively charged particles. Each orbit is constant, the total particle configuration determines the material. Electrons can jump from one orbit to another, absorbing or releasing energy through photons of one frequency or another. The most distant orbits contain electrons with the maximum energy level. Interestingly, the photon itself exhibits a dual nature, being defined simultaneously as a massless particle and electromagnetic radiation.

The word "photon" itself is of Greek origin, it means "particle of light". Therefore, it can be argued that when the electron changes its orbit, it absorbs (emits) a quantum of light. In this case, it is appropriate to explain the meaning of another word - "quantum". In fact, there is nothing complicated. The word comes from the Latin "quantum", which literally translates as the smallest value of any physical quantity (here - radiation). Let us explain with an example what a quantum is: if, when measuring weight, the smallest indivisible quantity was a milligram, then it could be called that. This is how a seemingly complex term is simply explained.

Quantum dots explained

Often in textbooks you can find the following definition for a nanodot - it is an extremely small particle of some material, the dimensions of which are comparable to the value of the emitted wavelength of an electron (the full spectrum covers the limit from 1 to 10 nanometers). Inside it, the value of a single negative charge carrier is less than outside, so the electron is limited in its movements.

However, the term "quantum dots" can be explained differently. An electron that has absorbed a photon "rises" to a higher energy level, and a "shortage" forms in its place - the so-called hole. Accordingly, if the electron has -1 charge, then the hole is +1. In an effort to return to its previous stable state, the electron emits a photon. The connection of charge carriers "-" and "+" in this case is called an exciton and in physics it is understood as a particle. Its size depends on the level of absorbed energy (higher orbit). Quantum dots are precisely these particles. The frequency of the energy emitted by an electron is directly dependent on the particle size of the given material and the exciton. It should be noted that the color perception of light by the human eye is based on different