quantum dot. Quantum dots - a new technology for the production of displays
Quantum dots and why they are put
- quantum technologies,
- Monitors and TV
Good time of the day, Khabrazhiteli! I think many have noticed that more and more advertisements for displays based on quantum dot technology, the so-called QD - LED (QLED) displays, began to appear and despite the fact that on this moment it's just marketing. Similar to LED TV and Retina, this is an LCD display technology that uses quantum dot LEDs as a backlight.
Your obedient servant decided to figure out what is quantum dots and what they are eaten with.
Instead of an introduction
quantum dot- a fragment of a conductor or semiconductor whose charge carriers (electrons or holes) are limited in space in all three dimensions. The size of a quantum dot must be so small that quantum effects are significant. This is achieved if the kinetic energy of the electron is noticeably greater than all other energy scales: first of all, it is greater than the temperature expressed in energy units. Quantum dots were first synthesized in the early 1980s by Alexei Ekimov in a glass matrix and Louis E. Brus in colloidal solutions. The term "quantum dot" was coined by Mark Reed.The energy spectrum of a quantum dot is discrete, and the distance between the stationary energy levels of the charge carrier depends on the size of the quantum dot itself as - ħ/(2md^2), where:
- ħ is the reduced Planck constant;
- d is the characteristic point size;
- m- effective mass electron on a point
For example, when an electron moves to energy level below, a photon is emitted; since it is possible to control the size of the quantum dot, it is also possible to change the energy of the emitted photon, which means changing the color of the light emitted by the quantum dot.
Types of quantum dots
There are two types:- epitaxial quantum dots;
- colloidal quantum dots.
Construction of quantum dots
Usually a quantum dot is a semiconductor crystal in which quantum effects are realized. An electron in such a crystal feels like it is in a three-dimensional potential well and has many stationary energy levels. Accordingly, when moving from one level to another, a quantum dot can emit a photon. With all this, the transitions are easy to control by changing the size of the crystal. It is also possible to throw an electron to a high energy level and receive radiation from the transition between lower levels and, as a result, we get luminescence. Actually, it was the observation of this phenomenon that served as the first observation of quantum dots.Now about displays
The history of full-fledged displays began in February 2011, when Samsung Electronics presented the development of a full-color display based on QLED quantum dots. It was a 4-inch display driven by an active matrix, i.e. each color quantum dot pixel can be turned on and off by a thin film transistor.To create a prototype, a layer of quantum dot solution is applied to the silicon board and a solvent is sprayed on. After that, a rubber stamp with a comb surface is pressed into the layer of quantum dots, separated and stamped onto glass or flexible plastic. This is how the strips of quantum dots are deposited on the substrate. In color displays, each pixel contains a red, green, or blue subpixel. Accordingly, these colors are used with different intensities to obtain the best possible more shades.
The next step in development was the publication of an article by scientists from the Indian Institute of Science in Bangalore. Where quantum dots were described that luminesce not only in orange, but also in the range from dark green to red.
Why is LCD worse?
The main difference between a QLED display and an LCD is that the latter can only cover 20-30% of the color range. Also, in QLED TVs, there is no need to use a layer with light filters, since the crystals, when voltage is applied to them, always emit light with a well-defined wavelength and, as a result, with the same color value.
There was also news about the sale of a quantum dot computer display in China. Unfortunately, I have not had a chance to check it with my own eyes, unlike the TV.
P.S. It is worth noting that the scope of quantum dots is not limited to LED - monitors, among other things, they can be used in field-effect transistors, photocells, laser diodes, they are also being studied for the possibility of using them in medicine and quantum computing.
P.P.S. If we talk about my personal opinion, then I believe that they will not be popular for the next ten years, not because they are little known, but because the prices for these displays are exorbitant, but still I would like to hope that quantum points will find their application in medicine, and will be used not only to increase profits, but also for good purposes.
Tags:
- QLED
- LED
- Quantum display
"Nanotechnologies" is a word with a complex history and context in the Russian language, unfortunately, slightly discredited. However, if we ignore the ironic socio-economic overtones, we can state that nanotechnologies last years From a scientific and theoretical concept, they began to take on forms that in the foreseeable future can become real commercial products and enter our lives.
An excellent example of this is quantum dots. Technologies using semiconductor nanoparticles are gradually finding applications in a completely various areas: medicine, printing, photovoltaics, electronics - some of the products still exist at the level of prototypes, somewhere the technology has been partially implemented, and some are already in practice.
So what is a “quantum dot” and “what is it eaten with”?
A quantum dot is a nanocrystal of an inorganic semiconductor material (silicon, indium phosphide, cadmium selenide). "Nano" means measured in parts per billion, the sizes of such crystals vary from 2 to 10 nanometers. Due to such a small size, electrons in nanoparticles behave quite differently from those in bulk semiconductors.
The energy spectrum of a quantum dot is non-uniform, it has separate energy levels for an electron (negatively charged particle) and a hole. A hole in semiconductors is an empty valence bond, a positive charge carrier numerically equal to an electron, it appears when the bond between the nucleus and the electron is broken.
If conditions are created under which the charge carrier in the crystal passes from level to level, then a photon is emitted during this transition. By changing the particle size, one can control the absorption frequency and wavelength of this radiation. In practice, this means that, depending on the size of the particle, the dots will glow in different colors during irradiation.
The ability to control the wavelength of radiation through the particle size makes it possible to obtain stable substances from quantum dots that convert the energy they absorb into light radiation - photostable phosphors.
Solutions based on quantum dots are superior to traditional organic and inorganic phosphors in a number of parameters that are important for those areas of practical application in which precise tunable luminescence is required.
Advantages of quantum dots:
- Photostable, retain fluorescent properties for several years.
- High resistance to photofading: 100 to 1000 times higher than organic fluorophores.
- High quantum yield of fluorescence - up to 90%.
- Wide excitation spectrum: from UV to IR (400 - 200 nm).
- High color purity due to high fluorescence peaks (25-40 nm).
- High resistance to chemical degradation.
Another advantage, especially for printing, is that quantum dots can be used to make sols - highly dispersed colloidal systems with a liquid medium in which small particles are distributed. So from them it is possible to produce solutions suitable for inkjet printing.
Applications of quantum dots:
Protection of documents and products from falsification: securities, banknotes, identity cards, stamps, seals, certificates, certificates, plastic cards, trademarks. A multi-color coding system based on quantum dots can be commercially used for color marking products in the food, pharmaceutical, chemical industries, jewelry, and works of art.
Due to the fact that the liquid base can be water-based or UV-curable, almost any object can be marked with quantum dot ink - for paper and other absorbent substrates - water-based ink, and for non-absorbent substrates (glass, wood, metal, synthetic polymers). , composites) - UV ink.
Marker in medical and biological research. Due to the fact that biological markers, DNA and RNA fragments that react to a certain type of cells can be applied to the surface of quantum dots, they can be used as a contrast in biological research and cancer diagnostics. early stages when the tumor is not yet detected by standard diagnostic methods.
The use of quantum dots as fluorescent labels for the in vitro study of tumor cells is one of the most promising and rapidly developing fields of application of quantum dots in biomedicine.
The mass introduction of this technology is hindered only by the question of the safety of using contrasts with quantum dots in in vivo studies, since most of them are made from very toxic materials, and their dimensions are so small that they easily penetrate through any barriers of the body.
Quantum Dot Displays: QLED - the technology for creating LCD displays with LED backlighting based on quantum dots has already been tested by leading electronics manufacturers. The use of this technology allows to reduce the power consumption of the display, increase the luminous flux by 25-30% compared to LED screens, more juicy colors, clear color reproduction, color depth, the ability to make screens ultra-thin and flexible.
The prototype of the first display using this technology was presented by Samsung in February 2011, and the first computer display was released by Philips.
It uses quantum dots to produce red and green colors from the emission spectrum of blue LEDs, resulting in near-natural color reproduction. In 2013, Sony released a QLED screen that works on the same principle. Currently, this technology for the production of large screens is not widely used due to the high cost of production.
Quantum dot laser. A laser whose working medium is quantum dots in the emitting region has a number of advantages over traditional semiconductor lasers based on quantum wells. They have better performance in terms of frequency band, noise intensity, they are less sensitive to temperature changes.
Due to the fact that changing the composition and size of the quantum dot allows you to control the active medium of such a laser, it became possible to work at wavelengths that were previously unavailable. This technology is actively used in practice in medicine, with its help a laser scalpel was created.
Energy
Based on quantum dots, several models of thin-film solar cells have also been developed. They are based on the following principle of operation: photons of light fall on a photoelectric material containing quantum dots, stimulate the appearance of a pair of an electron and a hole, the energy of which is equal to or exceeds the minimum energy required for an electron of a given semiconductor in order to go from a bound state to a free state. By changing the size of the nanocrystals of the material, it is possible to vary the "energy performance" of the photovoltaic material.
Based on this principle, several original working prototypes have already been created. various kinds solar batteries.
In 2011, researchers at the University of Notre Dame proposed a "solar paint" based on titanium dioxide, which, when applied, can turn any object into solar battery. It has a rather low efficiency (only 1%), but it is cheap to manufacture and can be produced in large volumes.
In 2014, scientists from the Massachusetts Institute of Technology presented a method for manufacturing solar cells from ultrathin layers of quantum dots, the efficiency of their development is 9%, and the main know-how lies in the technology of combining quantum dots into a film.
In 2015, the Solar Photovoltaic Center of Excellence Laboratory at Los Alamos proposed its 3.2% efficiency solar window project, consisting of a transparent luminescent quantum concentrator that can occupy a fairly large area, and compact solar photovoltaic cells.
But researchers from the US National Renewable Energy Laboratory (NREL), in search of the optimal combination of metals to produce a cell with maximum quantum efficiency, created a real performance record holder - the internal and external quantum efficiency of their battery in tests was 114% and 130%, respectively.
These parameters are not the efficiency of the battery, which now shows a relatively small percentage - only 4.5%, however, optimizing the collection of photoflow was not the key goal of the study, which consisted only in selecting the most effective combination of elements. However, it is worth noting that prior to the NREL experiment, no battery showed a quantum efficiency above 100%.
As we can see, the potential areas of practical application of quantum dots are wide and varied, theoretical developments proceed in several directions at once. Mass introduction of them into various fields prevents a number of restrictions: the high cost of production of the points themselves, their toxicity, imperfection and economic inexpediency of the production technology itself.
In the very near future, a system of color coding and ink marking based on quantum dots may become widespread. Realizing that this market niche is not yet occupied, but is promising and science-intensive, the IQDEMY company, as one of the research tasks of its chemical laboratory (Novosibirsk), determined the development of an optimal formulation of UV-curable and water-based inks containing quantum dots.
The first print samples received are impressive and open up further prospects for the practical development of this technology:
Simply put, a quantum dot is a semiconductor whose electrical characteristics depend on its size and shape. By adjusting the size of the quantum dot, we can change the energy of the emitted photon, which means we can change the color of the light emitted by the quantum dot. The main advantage of a quantum dot is the ability to fine-tune the wavelength of the emitted light by changing its size.
Description:
Quantum dots are fragments of a conductor or semiconductor (eg InGaAs, CdSe or GaInP/InP) whose charge carriers (electrons or holes) are limited in space in all three dimensions. The size of a quantum dot must be so small that quantum effects are significant. This is achieved if the kinetic energy of the electron is noticeably greater than all other energy scales: first of all, it is greater than the temperature expressed in energy units.
Simply put, a quantum dot is a semiconductor whose electrical characteristics depend on its size and shape. How smaller size crystal, the greater the distance between the energy levels. When an electron moves to a lower energy level, a photon is emitted. By adjusting the size of the quantum dot, we can change the energy of the emitted photon, which means we can change the color of the light emitted by the quantum dot. The main advantage of a quantum dot is the ability to fine-tune the wavelength of the emitted light by changing its size.
quantum dots different sizes can be assembled into gradient multilayer nanofilms.
There are two types of quantum dots (according to the method of creation):
— colloidal quantum dots.
Characteristics:
Application:
— for various biochemical and biomedical studies, including for multicolor visualization of biological objects (viruses, cell organelles, cells, tissues) in vitro and in vivo, as well as passive fluorescent markers and active indicators for assessing the concentration of a certain substance in a particular sample,
— for multi-channel optical coding, e.g. in flow cytometry and high-throughput analysis of proteins and nucleic acids,
— to study the spatial and temporal distribution of biomolecules by the confocal method microscopy,
— in immunoanalysis,
— in situ diagnostics of cancer markers,
— in blotting,
— as a source white,
— V LEDs,
— in semiconductor technologies,
Linen thermal insulation and sound insulation...
Equipment for the production of animal feed - at... Superconducting conductors of the second generation... Hydroacoustic systems, hydroacoustic kits... Means of protection against pests and plant diseases... Composite fences pultrusion Hydrogen fuel cells... Mobile robots Servosil "Engineer"...
Good time of the day, Khabrazhiteli! I think many have noticed that more and more advertisements for displays based on quantum dot technology, the so-called QD - LED (QLED) displays, began to appear, despite the fact that at the moment this is just marketing. Similar to LED TV and Retina, this is an LCD display technology that uses quantum dot LEDs as a backlight.
Your humble servant nevertheless decided to figure out what quantum dots are and what they are eaten with.
Instead of an introduction
quantum dot- a fragment of a conductor or semiconductor whose charge carriers (electrons or holes) are limited in space in all three dimensions. The size of a quantum dot must be so small that quantum effects are significant. This is achieved if the kinetic energy of the electron is noticeably greater than all other energy scales: first of all, it is greater than the temperature expressed in energy units. Quantum dots were first synthesized in the early 1980s by Alexei Ekimov in a glass matrix and Louis E. Brus in colloidal solutions. The term "quantum dot" was coined by Mark Reed.The energy spectrum of a quantum dot is discrete, and the distance between the stationary energy levels of the charge carrier depends on the size of the quantum dot itself as - ħ/(2md^2), where:
- ħ is the reduced Planck constant;
- d is the characteristic point size;
- m is the effective mass of an electron at a point
For example, when an electron moves to a lower energy level, a photon is emitted; since it is possible to control the size of the quantum dot, it is also possible to change the energy of the emitted photon, which means changing the color of the light emitted by the quantum dot.
Types of quantum dots
There are two types:- epitaxial quantum dots;
- colloidal quantum dots.
Construction of quantum dots
Usually a quantum dot is a semiconductor crystal in which quantum effects are realized. An electron in such a crystal feels like it is in a three-dimensional potential well and has many stationary energy levels. Accordingly, when moving from one level to another, a quantum dot can emit a photon. With all this, the transitions are easy to control by changing the size of the crystal. It is also possible to throw an electron to a high energy level and receive radiation from the transition between lower levels and, as a result, we get luminescence. Actually, it was the observation of this phenomenon that served as the first observation of quantum dots.Now about displays
The history of full-fledged displays began in February 2011, when Samsung Electronics presented the development of a full-color display based on QLED quantum dots. It was a 4-inch display driven by an active matrix, i.e. each color quantum dot pixel can be turned on and off by a thin film transistor.To create a prototype, a layer of quantum dot solution is applied to the silicon board and a solvent is sprayed on. After that, a rubber stamp with a comb surface is pressed into the layer of quantum dots, separated and stamped onto glass or flexible plastic. This is how the strips of quantum dots are deposited on the substrate. In color displays, each pixel contains a red, green, or blue subpixel. Accordingly, these colors are used with different intensities to obtain as many shades as possible.
The next step in development was the publication of an article by scientists from the Indian Institute of Science in Bangalore. Where quantum dots were described that luminesce not only in orange, but also in the range from dark green to red.
Why is LCD worse?
The main difference between a QLED display and an LCD is that the latter can only cover 20-30% of the color range. Also, in QLED TVs, there is no need to use a layer with light filters, since the crystals, when voltage is applied to them, always emit light with a well-defined wavelength and, as a result, with the same color value.
There was also news about the sale of a quantum dot computer display in China. Unfortunately, I have not had a chance to check it with my own eyes, unlike the TV.
P.S. It is worth noting that the scope of quantum dots is not limited to LED - monitors, among other things, they can be used in field-effect transistors, photocells, laser diodes, they are also being studied for the possibility of using them in medicine and quantum computing.
P.P.S. If we talk about my personal opinion, then I believe that they will not be popular for the next ten years, not because they are little known, but because the prices for these displays are exorbitant, but still I would like to hope that quantum points will find their application in medicine, and will be used not only to increase profits, but also for good purposes.
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A.V. Fedorov, A.V. Baranov | ||||||||||||
Ln[ K(τ ) ] | ||||||||||||
τ , ps | ||||||||||||
Rice. 4.32. a is the logarithm of the envelope of the coherent control signal as a function of the mutual delay between pulses for different relative contributions of the Lorentz homogeneous and Gaussian inhomogeneous broadenings (r = 2 = ! ). The solid line is a purely Lorentzian homogeneous broadening with ~ 2 = 21:25 µeV; dashed line –r =1/1; dotted line –r =1/2.5; dash-dotted –r = 1/14. Absolute values2 and! were chosen in such a way that the HWHM of the photoluminescent line of a single quantum dot was kept constant (21:25 μeV) in accordance with the work . b – Voigt contour of the photoluminescent line of a single quantum dot, calculated for the same parameters as in case a.
measuring device and fitting with a Voigt contour. This leads to additional errors. On fig. 4.32b, the photoluminescence line shapes of a single quantum dot are plotted for the same ratios 2 = ! , as in Figure 4.32 a. It can be seen that the most informative part of the spectral lines is their wings, where it is difficult to achieve good relationship signal/noise. At the same time, the corresponding changes in K() are most pronounced in the region where the coherent control signal can be obtained with sufficient accuracy. Thus, the method of coherent control can be used to study the effects of charge environment fluctuations in optical and relaxation processes.
4.3. Applications of quantum dots
4.3.1. Quantum dot lasers for fiber communications
The development of fiber-optic telecommunications has led to the need to create efficient semiconductor lasers and optical amplifiers operating in the spectral region of the minimum losses of waveguides (1.25–1.65 μm). The longest wavelength achieved by InGaAs/GaAs quantum well lasers is 1230 nm for end-firing devices and 1260 nm for vertical cavity lasers. Sufficiently large threshold currents, low operating temperature and low
4. Optics of quantum dots |
the temperature stability of such lasers does not always meet the requirements for high-speed telecommunication devices.
Progress in the fabrication of multilayer structures of self-assembled quantum dot compounds A3 B5, sufficiently uniform in size and shape at high surface density, has led to the creation of semiconductor lasers with quantum dots as an active medium. As a result, the spectral region 1.0–1.7 µm became available for generation both for conventional lasers and vertical cavity lasers using InGaAs quantum dots and GaAs substrates. In particular, both types of lasers can generate 1.3 µm radiation with extremely low threshold currents and high output power. A broadband quantum dot laser has recently been demonstrated, emitting at 1.5 µm with a current density of only 70 A/cm2 per quantum dot layer at room temperature. Optical amplifiers based on quantum dot structures are of interest for high-speed signal processing at rates above 40 Gbit/s. It is important that the developed GaAs technologies make it possible to fabricate fairly cheap monolithic vertical-cavity quantum dot lasers with distributed Bragg mirrors based on AlAs/GaAs and AlOx/GaAs pairs.
It should be noted that due to the inhomogeneous broadening electronic transitions in quantum dots, it becomes possible to expand the region of continuous tuning of the lasing wavelength. With some increase in the threshold currents, it can reach 200 nm (1.033–1.234 μm) .
Lasers using InAs quantum dots and InP substrates are also of interest, since they allow lasing in a longer wavelength range (1.8–2.3 μm), which is important for applications in molecular spectroscopy and remote monitoring of gaseous atmospheres using lidars. At the same time, the generation of radiation with a wavelength of 1.9 and 2 μm from a laser with an active medium from such a heterostructure has been obtained so far only at a low (77 K) temperature. Interestingly, lasing at wavelengths of 1.6 and 1.78 μm was also demonstrated for lasers based on InAs quantum wires—one-dimensional quantum structures on a (001)InP substrate. Finally, continuous lasing in the 2 μm region was obtained at room temperature using InAsSb-based quantum dots grown on a (001)InP substrate as the active laser medium.
The intensive development of this direction has led to the fact that at present some types of semiconductor lasers with an active medium based on quantum dots have become commercially available, .
260 A.V. Fedorov, A.V. Baranov
4.3.2. Quantum dots in biology and medicine
One of the most actively developing areas of application of semiconductor quantum dots is the use of colloidal quantum dots (semiconductor nanocrystals in organic and aqueous solutions) as luminescent labels for visualizing the structure of biological objects. different type and for ultra-sensitive detection of biochemical reactions, which are essential in molecular and cellular biology, medical diagnostics and therapy. A luminescent label is a phosphor associated with a linker molecule, which can selectively bind to a detectable biostructure (target). The labels must be soluble in water, have a high absorption coefficient, and have a high luminescence quantum yield in a narrow spectral band. The latter is especially important for the registration of multicolor images, when different targets in the cell are marked with different labels. Organic dyes are commonly used as phosphors for labels. Their disadvantages are low resistance to photobleaching, which does not allow long-term measurements, the need to use several light sources to excite various dyes, as well as the large width and asymmetry of the luminescence bands, which make it difficult to analyze multicolor images.
Recent achievements in the field of nanotechnology allow us to speak about the creation of a new class of luminescent labels using semiconductor quantum dots - colloidal nanocrystals - as a phosphor.
The synthesis of nanocrystals based on A2 B6 (CdSe, CdS, CdTe, ZnS) and A3 B5 (InP and GaAs) compounds has been known for a long time. Back in 1993, high-temperature organometallic synthesis of CdSe quantum dots was proposed and nanocrystals with a good crystal structure and a narrow size distribution, but with a quantum yield not exceeding 10%, were obtained. A sharp increase in the quantum yield of quantum dots up to 85% at room temperature was achieved when nanocrystals began to be coated with a thin (1–2 monolayers) shell of another material with a larger band gap (for example, for CdSe, this is ZnS, CdS, CdO). Such structures are called core/shell quantum dots (core/shell QDs). The diameter of quantum dots (from 1.5 nm and above) can be controlled by varying the reaction time, which takes place at a temperature of about 300o C, from minutes to several hours, or simply by selecting required amount product through different time after the start of the reaction. As a result, it turned out to be possible to obtain a set of quantum dots of the same composition, but with different sizes. For example, the position of the luminescence band of CdSe/ZnS QDs can vary in the range from 433 to 650 nm (2.862–1.906 eV) with a band width of about 30 meV. The use of other materials makes it possible to significantly expand the spectral region of the tuning of the luminescence band of nanocrystals (Fig. 4.33). Essentially,
Optics of quantum dots | |||||
Intensity | |||||
Wavelength, | |||||
Rice. 4.33. Luminescence spectra of semiconductor nanocrystals of various compositions and sizes. Solid lines correspond to CdSe nanocrystals with diameters of 1.8, 3.0, and 6.0 nm; dotted lines correspond to InP nanocrystals with diameters of 3.0 and 4.6 nm; dashed lines correspond to InAs nanocrystals with sizes of 2.8, 3.6, 4.6, and 6.0 nm.
that nanocrystals exhibit narrower and more symmetrical luminescence bands than conventional organic dyes. This is an extremely important advantage when analyzing multicolor images. On fig. 4.34, as an example, the luminescence spectra of CdSe/ZnS nanocrystals and rhodamine 6G molecules are compared.
Intensity, rel. units
Rhodamine 6 F |
quantum dots
Wavelength, nm
Rice. 4.34. Comparison of the luminescence bands of quantum dots and molecules of rhodamine 6G.
An additional advantage is that nanocrystals of the same composition usually have a broad absorption band with a high molar extinction coefficient (up to 10–6 cm–1 M–1) corresponding to transitions to high-energy states. Its position weakly depends on the quantum dot size. Therefore, unlike dyes, it is possible
262 A.V. Fedorov, A.V. Baranov
efficient excitation of luminescence of nanocrystals of different sizes by a single laser light source. However, the main advantage is that nanocrystals have excellent photoresistance: they do not fade for several hours or even days, while the characteristic photobleaching times of conventional phosphors are limited to a few minutes (Fig. 4.35 AlexaFluor® 488Fig. 4.35. Photoinduced degradation of luminescence of labels based on CdSe/ZnS nanocrystals CdSe/ZnS and traditional molecular phosphors under the action of mercury lamp radiation.
The surface of such quantum dots obtained as a result chemical reaction, coated with hydrophobic molecules used in the synthesis, so they are soluble only in organic solvents. Because the biological objects(proteins, DNA, peptides) exist only in aqueous solutions, methods have been developed to modify the surface of nanocrystals, which make them water-soluble with both positively and negatively charged surfaces. Several types of linker molecules have been proposed that make it possible to selectively bind nanocrystals to analyzed biomolecules. As an example, Fig. 4.36 shows an example of a CdSe nanocrystal coated with a ZnS shell, which is covalently bound to a protein by a mercaptoacetic acid molecule.
At the very Lately luminescent labels based on semiconductor quantum dots for targets various types became commercially available.
To use quantum dots in vivo, it is necessary to take measures to reduce their toxicity. For this purpose, it was proposed to place quantum dots in inert polymer spheres with diameters of 50–300 nm and use them as phosphors in cases where the relatively large size of nanospheres does not prevent their use. Use-
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