Nanocrystal as well as preparation method and application thereof

Abstract

The embodiment of the invention provides a preparation method and device of nanocrystals. The preparation method comprises the following steps: S1, injecting a high-temperature precursor solution I and a normal-temperature precursor solution II into an ultrasonic atomization nozzle at the same time, mixing, and performing ultrasonic atomization to obtain precursor micro-nano liquid drops; s2, spraying the gas flow with the precursor micro-nano liquid drops into a temperature control chamber, and enabling a mixed solution of the precursor solution I and the precursor solution II in the micro-nano liquid to react for a set time at a set temperature, so as to obtain nanocrystalline micro-nano liquid drops; and S3, introducing the gas flow with the nanocrystalline micro-nano liquid drops into a low-pressure chamber, and performing low-pressure hot air drying to obtain the nanocrystalline material. The nanocrystalline material is prepared by adopting the double-chamber spray circulating device and process, the precursor micro-nano liquid drops react in the temperature control chamber, and the nanocrystalline micro-nano liquid drops are dried in the low-pressure hot air flow environment in the low-pressure chamber, so that the nanocrystalline material can be prepared with high efficiency and high material utilization rate, and the device and the process are suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanocrystal synthesis, in particular to a nanocrystal and a preparation method and application thereof. BACKGROUND

[0002] Nanocrystals, especially semiconductor nanocrystals (Quantum Dots, QDs), are extremely small inorganic liquid nanocrystals. The particle size is generally between 1\~20nm, the three-dimensional size is in the nanometer order, and the stable diameter is usually in the range of 2\~10nm, which is spherical or spherical. When nanocrystals are excited by external energy (light, electricity), they can emit different colors of light. The light-emitting color is determined by the composition and size of the quantum dots. Generally, the smaller the particle, the longer the absorption of blue light; the larger the particle, the shorter the absorption of red light. Nanocrystal materials are widely used in various fields due to their unique properties, such as displays, electronics, drug delivery, and biomedical applications. In the display field, nanocrystal display technology has become a high-performance wide color gamut display solution, which is recognized by more and more brand manufacturers and consumers.

[0003] Nanocrystal thermal injection method is a common method for synthesizing high-quality nanocrystals. It mainly involves heating the precursor solution to high temperature and then rapidly injecting it into a high-temperature reaction solution containing another precursor. The whole pyrolysis process is used to prepare related nanocrystals. In this process, the reaction precursor concentration is instantaneously supersaturated, exceeding the critical point of nucleation, and then rapidly obtaining monodisperse crystal nuclei to achieve rapid nucleation and slow growth of nanocrystals. Nanocrystals prepared by thermal injection method have high crystallinity, high uniformity and good dispersity. By changing the injection temperature, reaction time and other conditions, nanocrystals with different particle sizes and morphologies can be synthesized. Nanocrystals have wide application prospects in the fields of biology, optoelectronics, energy and others. Thermal injection method provides a high-quality material basis for them. Although the nanocrystals prepared by thermal injection method have high quality, it is not easy to realize in industrial production and is not suitable for large-scale production. SUMMARY

[0004] In order to better solve the above problems, the present application provides a preparation method and device of nanocrystals, which can realize large-scale production of nanocrystal materials, and has high material utilization and high production efficiency.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows: The application relates to a nanocrystal preparation device, which comprises an ultrasonic atomization nozzle and sequentially connected gas source mechanism, temperature control chamber and low-pressure chamber; the ultrasonic atomization nozzle comprises at least two liquid inlets, and feeding pumps for precursor solution I and precursor solution II are respectively connected to the liquid inlets; the outlet end of the ultrasonic atomization nozzle is connected with the gas inlet pipe of the temperature control chamber; the gas source mechanism is used for feeding gas flow into the temperature control chamber; the temperature control mechanism is arranged outside the temperature control chamber; the heating mechanism is arranged in the connecting pipeline between the outlet end of the temperature control chamber and the inlet end of the low-pressure chamber; the bottom of the low-pressure chamber is provided with a material collecting port; and the low-pressure chamber is further connected with a gas pump, which is used for keeping the low-pressure chamber at a set pressure.

[0006] Optionally, the preparation device further comprises a material collecting mechanism, which comprises a cyclone separator, a condenser, a solvent recovery tank and a gas recovery tank; the gas inlet end of the cyclone separator is connected with the gas pump; the gas inlet end of the condenser is connected with the gas outlet end of the cyclone separator; and the liquid collecting end and the gas outlet end of the condenser are respectively connected with the solvent recovery tank and the gas recovery tank.

[0007] A nanocrystal preparation method comprises the following steps: S0, controlling the gas source mechanism to feed gas flow into the temperature control chamber, controlling the gas pump to exhaust gas from the low-pressure chamber, keeping the low-pressure chamber at a set pressure, controlling the temperature control mechanism to start and keep the temperature in the temperature control chamber at a first set temperature, and controlling the heating mechanism to start and heat the gas flow flowing into the low-pressure chamber to a second set temperature; S1, simultaneously injecting high-temperature precursor solution I and normal-temperature precursor solution II into the ultrasonic atomization nozzle, mixing and ultrasonic atomizing the precursor solution I and the precursor solution II into precursor micro-nano liquid drops; S2, spraying the precursor micro-nano liquid drops in the gas flow into the temperature control chamber, making the mixed solution of the precursor solution I and the precursor solution II in the micro-nano liquid react at a set temperature for a set time, and obtaining nanocrystal micro-nano liquid drops; S3, feeding the nanocrystal micro-nano liquid drops in the gas flow into the low-pressure chamber, drying the nanocrystal micro-nano liquid drops in the low-pressure hot gas flow, and obtaining nanocrystal materials; wherein the size of the micro-nano liquid drops is 100 nm-100 mu m, and the particle size of the nanocrystal materials is 3 nm-90 nm.

[0008] Optionally, the set pressure is 50 Pa-10000 Pa, the set time is 0.1-120 min, and the nanocrystal micro-nano liquid drops are dried in the low-pressure chamber for 3-600 s.

[0009] Optionally, the ratio of the feeding speeds of the precursor solution I and the precursor solution II is 1-5:1-10, the working frequency of the ultrasonic atomization nozzle is 5-80 kHz, and the feeding speed is 0.1 ml / s-4 ml / s.

[0010] Optionally, the temperature of the precursor solution I is 100-400℃, the temperature control mechanism controls the temperature in the temperature control chamber to be -40-400℃, and the heating mechanism heats the gas flow flowing therethrough to 60-300℃.

[0011] Optionally, the precursor solution I comprises at least one of a Group II metal ion compound, a Group III metal ion compound, an A-site cation compound or a B-site cation compound, and a Group I cation compound; the precursor solution II comprises at least one of a Group VI element compound, a Group V element compound, and a halogen element compound; and the nanocrystal material comprises a Group II-VI, a Group III-V, a metal halide perovskite, and a Group I-III-VI nanocrystal.

[0012] Optionally, the Group II metal ion compound is at least one of CdO, Cd(OH)2, CdX2, HgX2, Cd(CH3COO)2, Cd(acac)2, Cd(St)2, Cd(OA)2, ZnEt2, Zn(La)2, Zn(CH3COO)2, Zn(St)2, Mg(acac)2, X being a halogen element; the Group III metal ion compound is at least one of InX3, GaX3, In(acac)3, In(CH3COO)2, In(My)3, TMIn, TEGa, Ga(acac)3, Ga(CH3COO)2, Ga(tBu)3, TMAl, X being a halogen element; the A-site cation compound is at least one of Cs2CO3, Cs(CH3COO), CsX, FAX, MAX; the B-site cation compound is at least one of PbX2, Pb(CH3COO)2, PbCO3, SnX2, GeX2, X being a halogen element; the Group I cation compound is at least one of Cu(OA), CuX, Cu(acac)2, Cu(CH3COO)2, CuSCN, Ag2S, AgOA, AgNO3, AgTFA, Ag(CH3COO), AuX, AuSTm, X being a halogen element; and the Group VI element compound is at least one of S8, TOP-Se, TMS-Se, TOP-S, TMS-S, S-OAm, Te0, TOP-Te, TeO2, TMS-Te, (NH2)2CS, Se, (NH2)2CSe, (C6H5)2Se2, C3H6O2Se, C 12 H 25at least one of SH; the group V element compound is at least one of TMS3As, As0, (CH3)3CAsH2, SbCl3, Sb0, Sb(CH3COO)3, PH3, AsH3, (TMS)3P, (DMA)3P, (C4H9)PH2, (C4H9O)3PO, TOP, P4, P(NMe2)3; the halogen element compound is at least one of HX, NH4X, PX3, tetrabutylammonium halide TBAX, trimethylsilane halide TMS-X, X is a halogen element.

[0013] Optionally, in step S1, compound c is also injected into the ultrasonic atomization nozzle at the same time as the precursor solution I and the precursor solution II; the compound c is selected from at least one of oleic acid, oleylamine, oleic acid bromide, glycopyrronium bromide, dodecyl mercaptan, dodecylamine, tetrabutylammonium iodide, trioctylphosphine, trioctylphosphine oxide, tetradecylphosphonic acid, mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, mercaptoethylamine, cysteine, glutathione, ammonium perfluorooctanoate, polyethylene glycol mercaptan, dihydrolipoic acid, thiocyanate guanidine.

[0014] Optionally, the precursor solution I further comprises a solvent I; the solvent I is an organic solvent, and the organic solvent is at least one of N, N-dimethylformamide, dimethyl sulfoxide, n-hexane, octadecene, trimethyl phosphate, triethyl phosphate, N-methyl pyrrolidone, dimethylacetamide; and / or, the precursor solution II further comprises a solvent II, and the solvent II is at least one of tetrahydrofuran, amyl acetate, toluene, acetone, n-hexane, octane, octadecene.

[0015] Compared with the prior art, the present application has at least the following positive technical effects: (1) The present application realizes high-efficiency synthesis of II-VI group, III-V group, metal halide perovskite, and I-III-VI group nanocrystals by using a spray circulation method, which is carried out in anhydrous and oxygen-free environment throughout the process, and the utilization rate of raw materials except solvents can be improved to more than 80%, which is higher than that of traditional hot injection and anti-solvent methods. The nanocrystals prepared by traditional hot injection and anti-solvent methods still need to go through a centrifugal purification step, which reduces the utilization efficiency of raw materials. In the present application, the raw materials are controlled in the micro-nano droplets obtained by ultrasonic spraying for reaction, the content of raw materials in the micro-nano droplets is limited, and the size of the micro-nano droplets is also limited, and there is a steric hindrance effect between the micro-nano droplets and the surrounding droplets, which avoids the uncontrolled growth of raw materials in the reaction process. Therefore, the utilization rate of raw materials can be more than 80%, and the size uniformity is good.

[0016] (2) The spray circulation method is adopted in the present application, the process is simple, easy to scale up production, only needs to continuously add raw materials, the equipment components work normally, then can produce continuously, is suitable for large-scale production, and after the production of one batch by the hot injection method and the anti-solvent method, raw materials need to be prepared again, the organic solvents used in the circulation link can be recycled, has the characteristics of low production cost and green environmental protection.

[0017] (3) The II-VI group, III-V group, metal halide perovskite and I-III-VI group nanocrystal materials prepared by the present application have uniform sizes, can be blended with various photoresists, UV glue, pressure-sensitive adhesive, transparent polymer film and various organic solvents and the like, and various processes such as dispensing, inkjet printing, screen printing, casting, photolithography and the like are used to prepare light-emitting dots, lines, films and the like of the light-emitting materials, which are applied to Micro / Mini LED direct display and LED lighting devices and liquid crystal display backlight and the like of small-size devices, and the application range of the nanocrystal materials is widened. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 It is a structure schematic diagram of the nanocrystal preparation device of the present application embodiment one; Figure 2 It is a real object diagram of the green CsPbBr3 perovskite nanocrystal material prepared in the present application experimental example 1; Figure 3 It is a fluorescence spectrum diagram of the green CsPbBr3 perovskite nanocrystal material prepared in the present application experimental example 1 under blue light excitation; Figure 4 It is a scanning electron microscope diagram of the green CsPbBr3 perovskite nanocrystal material prepared in the present application experimental example 1; Figure 5 It is a schematic diagram of the light conversion film of the green CsPbBr3 perovskite nanocrystal material in the present application experimental example 1; Figure 6 It is an effect diagram of the light conversion film prepared by the green CsPbBr3 perovskite nanocrystal in the present application experimental example 1, showing the decay of photoluminescence intensity with time at high temperature; Figure 7 It is a fluorescence spectrum of the black PbS II-VI group nanocrystal material prepared in the present application experimental example 2 under blue light excitation.

[0020] Reference signs: 1, gas source mechanism; 2, ultrasonic atomization nozzle; 3, temperature control mechanism; 4, temperature control chamber; 5, heating mechanism; 6, low pressure chamber; 7, material collection port; 8, air pump; 9, cyclone separator; 10, condenser. DETAILED DESCRIPTION

[0021] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application. Therefore, based on the specific embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0023] In the embodiments of the present application, the raw materials and raw material components used are all commercially available products well known to those skilled in the art, unless otherwise specified. The test methods used are all conventional methods well known to those skilled in the art, unless otherwise specified. EMBODIMENT

[0024] The present embodiment provides a preparation device for nanocrystals, as shown in Figure 1 The preparation device is a double-chamber spray circulation device, which includes an ultrasonic atomization nozzle 2 and a gas source mechanism 1, a temperature control chamber 4 and a low pressure chamber 6 connected in sequence. Specifically, the gas source mechanism 1 is connected to the inlet end of the temperature control chamber 4 through an air inlet pipe, the outlet end of the temperature control chamber 4 is connected to the inlet end of the low pressure chamber 6, and the outlet end of the ultrasonic atomization nozzle 2 is connected to the air inlet pipe between the gas source mechanism 1 and the temperature control chamber 4.

[0025] The gas source mechanism 1 is used to introduce gas into the temperature control chamber 4, and the gas can form an air environment or an inert gas environment for nanocrystal preparation in the temperature control chamber 4 and the low pressure chamber 6. Here, the gas can be selected from air, nitrogen, helium, argon and the like. The gas source mechanism 1 can include a corresponding gas storage tank. The gas source mechanism 1 introduces gas into the temperature control chamber 4 and forms a gas flow in the air inlet pipe. The gas flow can carry the micro-nano droplets of the precursor sprayed into the air inlet pipe into the temperature control chamber 4, so that the micro-nano droplets of the precursor are sprayed in the temperature control chamber 4.

[0026] The ultrasonic atomization nozzle 2 has at least two liquid inlets, respectively connected with the feed pumps of the precursor solution I and the precursor solution II. The two feed pumps are respectively used to inject the precursor solution I and the precursor solution II into the ultrasonic atomization nozzle 2. Here, the two feed pumps can be independently controlled, so that the feeding speed of the two precursor solutions can be independently controlled, and the two precursor solutions can be controlled to be fed at different speeds. The ultrasonic atomization nozzle 2 is used to ultrasonic atomize the mixture of the precursor solution I and the precursor solution II, and spray micro-nano droplets. Here, the size of the precursor micro-nano droplets sprayed by the ultrasonic atomization nozzle 2 can be controlled by controlling the ultrasonic vibration frequency.

[0027] The temperature control chamber 4 is used for the reaction of the mixture of the precursor solution I and the precursor solution II in the precursor micro-nano droplets to form nanocrystals. The temperature control mechanism 3 is arranged outside the temperature control chamber 4, which is used to heat the outer wall of the temperature control chamber 4 to keep the inside of the temperature control chamber 4 at a set temperature, so that the precursor micro-nano droplets sprayed into the temperature control chamber 4 can react at a suitable temperature, and after a certain time of reaction, nanocrystals are formed, and micro-nano droplets containing nanocrystals are obtained. Here, the temperature control mechanism 3 can include a heating layer composed of uniformly arranged electric heating wires arranged outside the temperature control chamber 4, and a temperature sensor arranged in the temperature control chamber 4, which is used to adjust the temperature in the temperature control chamber 4 in real time, so as to ensure the temperature at which the precursor micro-nano droplets react.

[0028] The low-pressure chamber 6 is used for drying the nanocrystal micro-nano droplets to obtain nanocrystal materials. The heating mechanism 5 is arranged in the communication pipeline between the outlet end of the temperature control chamber 4 and the inlet end of the low-pressure chamber 6. The heating mechanism 5 is used to heat the gas flow flowing through it, so that a low-pressure hot gas flow is formed in the low-pressure chamber 6, and the nanocrystals are quickly separated from the solvent by using the low-pressure hot gas flow, and nanocrystal materials are obtained. Here, the heating mechanism 5 can include an array of electric heating wires laterally supported in the communication pipeline. The gas flow flowing out of the temperature control chamber 4 flows into the low-pressure chamber 6 through the array of electric heating wires. The array of electric heating wires can heat the gas flow to a set temperature, so that the nanocrystal micro-nano droplets flowing into the low-pressure chamber 6 with the gas flow can be quickly dried. The bottom of the low-pressure chamber 6 is provided with a material collection port 7. The nanocrystal materials obtained after drying by the low-pressure hot gas flow will fall into the bottom of the low-pressure chamber 6, and can be collected into a material collection tank through the material collection port 7. Here, one or more material collection ports 7 can be designed according to the specific structure and size of the chamber, and a switch valve is arranged at the material collection port to open when a certain amount of nanocrystal materials is stored.

[0029] The low-pressure chamber 6 is also connected with a gas pump 8 for pumping gas from the low-pressure chamber 6 to keep the low-pressure chamber 6 at a set pressure. The gas source mechanism 1 supplies gas to the temperature control chamber 4, the gas flows into the low-pressure chamber 6, and the gas pump 8 pumps the gas out of the low-pressure chamber 6, thereby forming a gas flow of the gas source mechanism 1-temperature control chamber 4-low-pressure chamber 6 in the preparation device, which can carry the precursor micro-nano droplets into the temperature control chamber 4 and carry the nanocrystal micro-nano droplets into the low-pressure chamber 6. Here, by controlling the flow rate and flow of the gas supplied by the gas source mechanism 1 and the flow rate and flow of the gas pumped by the gas pump 8, the low-pressure environment in the temperature control chamber 4 and the low-pressure chamber 6 can be kept at a set pressure, the boiling point of the solvent (such as the commonly used organic solvent octadecene) in the nanocrystal micro-nano droplets can be reduced, the nanocrystal and the solvent can be quickly separated, and the drying can be quickly completed; on the other hand, the overall gas flow rate in the preparation device can also be controlled, thereby the time of the precursor micro-nano droplets staying in the temperature control chamber 4 and the time of the nanocrystal micro-nano droplets staying in the low-pressure chamber 6 can be controlled, and in combination with the size of the temperature control chamber 4 and the low-pressure chamber 6, the reaction time of the precursor micro-nano droplets and the drying time of the nanocrystal micro-nano droplets can be controlled.

[0030] In the embodiment, the preparation device further includes a material collecting mechanism, which includes a cyclone separator 9, a condenser 10, a solvent recovery tank and a gas recovery tank. The gas inlet end of the cyclone separator 9 is connected with the gas pump 8, the gas inlet end of the condenser 10 is connected with the gas outlet end of the cyclone separator 9, and the liquid collecting end and the gas outlet end of the condenser 10 are respectively connected with the solvent recovery tank and the gas recovery tank. The gas pumped out of the low-pressure chamber 6 by the gas pump 8 is a high-temperature gas flow carrying evaporated solvent vapor and part of the nanocrystal material. After entering the cyclone separator 9, the nanocrystal material enters the hopper of the cyclone separator 9, the gas flow carrying the solvent vapor enters the condenser 10, and after condensation, the solvent vapor condenses into solvent and enters the solvent recovery tank at the liquid collecting end, and the gas flows into the gas recovery tank at the gas outlet end. Here, the gas recovery tank can be replaced by an induced draft fan (or a gas pump) and a ventilation pipeline for introducing the gas into the air inlet pipe connected with the temperature control chamber 4 to form a recycling of the gas.

[0031] The nanocrystal preparation device of the embodiment can efficiently prepare nanocrystals by the design of double-chamber spray circulation, the flow of the ultrasonic atomized precursor micro-nano droplets in the double-chamber by the gas flow, the reaction of the precursor micro-nano droplets at a suitable temperature by the temperature control chamber, and the rapid drying of the nanocrystal micro-nano droplets in the low-pressure chamber by the low-pressure hot gas flow. The preparation device has high raw material utilization rate and simple operation, and can realize continuous preparation of nanocrystals by only adding raw materials, which is suitable for large-scale industrial production.

[0032] In actual application, the preparation device can further include other devices or components, or the actual installation position of each device or component can be adjusted, so as to realize the actual installation and application of the preparation device and other functions. For example, the preparation device further includes a controller and a detection component (such as a pressure sensor), which are used to realize the control of the nanocrystal preparation process; for another example, the inner walls of the temperature control chamber 4, the low-pressure chamber 6 and the connecting pipeline are polished, so as to reduce the adhesion of materials. Embodiment

[0033] The embodiment provides a nanocrystal preparation method based on a double-chamber spray circulation method for synthesizing nanocrystals. The nanocrystal preparation method uses the preparation device in the above embodiment one and adopts an ultrasonic atomization drying technology.

[0034] The nanocrystal preparation method of the embodiment includes the following steps. S0, the gas source mechanism 1 is controlled to introduce a gas flow into the temperature control chamber 4, the gas pump 8 is controlled to exhaust gas from the low-pressure chamber 6, so that the low-pressure chamber 6 is kept at a set pressure; the temperature control mechanism 3 is controlled to start to keep the temperature in the temperature control chamber 4 at a first set temperature, and the heating mechanism 5 is controlled to start to heat the gas flow flowing into the low-pressure chamber 6 to a second set temperature; S1, the high-temperature precursor solution I and the normal-temperature precursor solution II are simultaneously injected into the ultrasonic atomization nozzle 2, mixed and ultrasonically atomized into precursor micro-nano droplets; S2, the gas flow carries the precursor micro-nano droplets to spray in the temperature control chamber 4, so that the mixed solution of the precursor solution I and the precursor solution II in the micro-nano liquid reacts at a set temperature for a set time, and nanocrystal micro-nano droplets are obtained; S3, the gas flow carries the nanocrystal micro-nano droplets into the low-pressure chamber 6, and the nanocrystal material is obtained through low-pressure hot gas flow drying.

[0035] In the preparation method, the step S0 corresponds to a preparation step. According to the information of the nanocrystal material to be prepared and the categories of the precursor solutions in actual working conditions, key parameters such as the reaction time of the precursor mixed solution and the drying time of the nanocrystal micro-nano droplets in the preparation process are determined, and the flow rate and flow of the introduced gas flow, the exhaust speed and flow of the gas pump 8, the temperature in the temperature control chamber 4 and the temperature of the hot gas flow are adjusted in this step, so as to prepare the nanocrystal.

[0036] In step S1, the temperature of the precursor solution I is 100-400°C, and the temperature of the precursor solution II is normal temperature. The two precursor solutions are respectively fed into the ultrasonic atomization nozzle 2 through independently controlled feed pumps, mixed into a precursor mixed solution in the ultrasonic atomization nozzle 2, and then atomized into precursor micro-nano droplets by ultrasonic atomization. Here, the ratio of the feeding speed of the precursor solution I to the feeding speed of the precursor solution II is 1-5:1-10, the working frequency of the ultrasonic atomization nozzle 2 is 5-80 kHz, and the feeding speed is 0.1-4 ml / s. The size of the micro-nano droplets is 100 nm-100 μm, which can be realized by controlling the ultrasonic vibration frequency and the feeding speed of the precursor solution.

[0037] In step S2, the ultrasonic atomization nozzle 2 sprays the precursor micro-nano droplets into a gas flow, and the precursor micro-nano droplets flow into the control chamber with the gas flow. Under the action of the temperature control mechanism 3, the temperature control chamber 4 is kept at a set temperature, which can be-40-400°C. In this step, the reaction time of the precursor micro-nano droplets in the temperature control chamber 4 is 0.1-120 min. The specific set temperature and set reaction time can be determined according to the actual working conditions of the nanocrystalline material to be synthesized and the type of precursor raw material, which can ensure that the precursor micro-nano droplets are successfully reacted into nanocrystalline micro-nano droplets.

[0038] In step S3, the nanocrystalline micro-nano droplets flow into the low-pressure chamber 6 with the gas flow, and the heating mechanism 5 heats the gas flow flowing through to 60-300°C, so that the nanocrystalline micro-nano droplets are dried in the low-pressure chamber 6, the solvent evaporates, and the nanocrystalline material and the solvent are separated after drying. The pressure in the low-pressure chamber 6 in this step is 50-10000 Pa. The solvent in the micro-nano droplets can be quickly evaporated in the low-pressure gas flow, the nanocrystalline material and the solvent are quickly separated, and the drying time is 3-600 s.

[0039] In this embodiment, the particle size of the synthesized nanocrystalline material is 3-90 nm, which can be controlled by controlling the size of the micro-nano droplets generated by the ultrasonic atomization nozzle 2 and the concentration of the two precursor solutions. The set reaction time of the precursor micro-nano droplets in the temperature control chamber 4 is preferably 0.1-30 min, and the set drying time of the nanocrystalline micro-nano droplets in the low-pressure chamber 6 is preferably 3-200 s. The reaction time and the set time can be controlled by controlling the speed and flow of the gas flow into the temperature control chamber 4 and the gas flow extracted from the low-pressure chamber 6 according to the actual working conditions of the nanocrystalline material to be synthesized and the type of precursor raw material required by the production of the double-chamber size.

[0040] The preparation method further comprises a collecting step. After the nanocrystal micro-nano liquid drops are dried by the low-pressure hot gas flow, the nanocrystal material is separated from the solvent, the nanocrystal material with a larger size falls into the collecting port 7 at the bottom of the low-pressure chamber 6, and is collected by a collecting tank; the nanocrystal material with a small size and the solvent vapor are pumped into a cyclone separator 9 by a gas pump 8, and the nanocrystal material is collected in a hopper of the cyclone separator 9; the gas is introduced into a condenser 10 by the cyclone separator 9, the solvent is recovered at the condenser 10, and the recovered gas is recycled. Embodiment

[0041] The embodiment provides a preparation method of nanocrystals. The preparation method of nanocrystals in the embodiment is different from the preparation method of nanocrystals in the second embodiment. The nanocrystal material prepared in the embodiment comprises II-VI group, III-V group, metal halide perovskite or I-III-VI group nanocrystals. The precursor solution I provides at least one of II group metal ions, III group metal ions, A site cations or B site cations and I group cations. The precursor solution I comprises a solvent I and at least one of II group metal ion compounds, III group metal ion compounds, A site cation compounds or B site cation compounds and I group cation compounds. The precursor solution II provides at least one of VI group elements, V group elements and halogen elements. The precursor solution II comprises a solvent II and at least one of VI group element compounds, V group element compounds and halogen element compounds.

[0042] The II group metal ion compound comprises at least one of CdO, Cd(OH)2, CdX2, HgX2, cadmium acetate Cd(CH3COO)2, cadmium acetylacetone Cd(acac)2, cadmium stearate Cd(St)2, cadmium oleate Cd(OA)2, diethyl zinc ZnEt2, zinc laurate Zn(La)2, zinc acetate Zn(CH3COO)2, zinc stearate Zn(St)2, magnesium acetylacetone Mg(acac)2 and the like, and X is a halogen element. The III group metal ion compound comprises at least one of InX3, GaX3, indium acetylacetone In(acac)3, indium acetate In(CH3COO)2, indium myristate In(My)3, trimethyl indium TMIn, triethyl gallium TEGa, gallium acetylacetone Ga(acac)3, cadmium acetate Ga(CH3COO)2, tri-tert-butyl gallium Ga(tBu)3 and trimethyl aluminum TMAl, and X is a halogen element. The A site cation compound comprises at least one of Cs2CO3, cesium acetate Cs(CH3COO), CsX, FAX and MAX. The B site cation compound comprises at least one of PbX2, lead acetate Pb(CH3COO)2, PbCO3, SnX2 and GeX2, and X is a halogen element. Group I cationic compounds include at least one of Cu(OA), CuX, copper acetylacetonate Cu(acac)2, copper acetate Cu(CH3COO)2, cuprous thiocyanate CuSCN, Ag2S, AgOA, AgNO3, silver trifluoroacetate AgTFA, silver acetate Ag(CH3COO), AuX, gold thiomalate AuSTm, etc., X is a halogen element; Solvent I is an organic solvent, which can include at least one of N,N-dimethylformamide, dimethyl sulfoxide, n-hexane, octadecene, trimethyl phosphate, triethyl phosphate, N-methyl pyrrolidone, dimethylacetamide.

[0043] Group VI element compounds include cyclic sulfur S8, trioctylphosphine-selenium TOP-Se, trimethylsilylselenium TMS-Se, trioctylphosphine-sulfur TOP-S, trimethylsilylthiol TMS-S, S-OAm, tellurium powder Te0, trioctylphosphine-tellurium TOP-Te, TeO2, trimethylsilyltellurium TMS-Te, thiourea (NH2)2CS, Se, selenourea (NH2)2CSe, diphenyl diselenide (C6H5)2Se2, ethyl selenoacetate C3H6O2Se, dodecanethiol C 12 H 25 SH, etc. Group V element compounds include at least one of tris(trimethylsilyl)arsenic TMS3As, arsenic powder As0, tert-butylarsane (CH3)3CAsH2, SbCl3, antimony powder Sb0, antimony acetate Sb(CH3COO)3, PH3, AsH3, tris(trimethylsilyl)phosphorus (TMS)3P, tris(dimethylamine)phosphorus (DMA)3P, butylphosphine (C4H9)PH2, tributyl phosphate (C4H9O)3PO, trioctylphosphine TOP, white phosphorus P4, tris(dimethylamine)phosphine P(NMe2)3, etc. Halogen element compounds include at least one of HX, NH4X, PX3, tetrabutylammonium halide TBAX, trimethylsilyl halide TMS-X, etc., X is a halogen element; Solvent II includes at least one of tetrahydrofuran, amyl acetate, toluene, acetone, n-hexane, octane, octadecene.

[0044] In this embodiment, the precursor mixed solution further includes a compound c, which includes at least one of oleic acid, oleylamine, oleic acid bromide, glycofurol, dodecyl mercaptan, dodecylamine, tetrabutylammonium iodide, tri-octyl phosphine, tri-octyl phosphine oxide, tetradecyl phosphonic acid, mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, mercaptoethylamine, cysteine, glutathione, ammonium perfluorooctanoate, polyethylene glycol thiol, dihydrolipoic acid, thiocyanic acid guanidine, etc. Specifically, in step S1, the compound is also injected into the ultrasonic atomization nozzle 2 at the same time as the precursor solution I and the precursor solution II, and after mixing the precursor mixed solution, ultrasonic atomization is performed. Here, the ultrasonic atomization nozzle 2 can include a third liquid inlet for injecting the compound c, which is atomized into precursor micro-nano droplets after being mixed with the precursor solution I and the precursor solution II in the ultrasonic atomization nozzle 2.

[0045] The II-VI, III-V, metal halide perovskite or I-III-VI nanocrystal material prepared by the embodiment of the present application can be applied in display devices, lighting devices, photovoltaic light conversion materials, patterned thin films and fluorescent anti-counterfeiting inks. For example, the display device can include Micro / Mini LED direct display, LED lighting device and liquid crystal display backlight.

[0046] Experimental Example 1, Preparation of Green CsPbBr3 Perovskite Nanocrystal Material PbBr2, OA and OLA were dissolved in 5 ml of ODE in a molar ratio of 0.2:1:1 to form a precursor solution I. 0.4 mmol of CsCO3 was dissolved in 6 ml of OA to form a precursor solution II. After stirring for 2 hours, the two precursor solutions were subjected to spray drying, using the preparation device of the above embodiment one and the preparation method of the above embodiment two. The working frequency of the ultrasonic atomization nozzle 2 was 50 kHz, the feeding speed of the precursor solution I was 2 ml / s, the feeding speed of the precursor solution II was 0.2 ml / s, the mixed solution of the precursor solution I and the precursor solution II in the micro-nano droplets flowed into the temperature control chamber 4 with nitrogen gas, the temperature in the temperature control chamber 4 was 50°C, the generated green CsPbBr3 perovskite nanocrystal micro-nano droplets flowed into the low-pressure chamber 6 with nitrogen gas, the gas pressure in the low-pressure chamber 6 was 200 Pa, and the nitrogen gas was heated to 220°C by the resistance wire, and then dried to obtain the green CsPbBr3 perovskite nanocrystal material.

[0047] The obtained green CsPbBr3 perovskite nanocrystal material is as shown in Figure 2 The powder is uniformly dispersed and bright green. Its luminescence spectrum is as shown in Figure 3The emission peak is located at 522 nm with a half-peak width of 23 nm, and the fluorescence quantum yield of the quantum dot film is over 90%. According to the optical properties, it can be inferred that the size of the green CsPbBr3 perovskite nanocrystal material in the powder is about 5 nm. The scanning electron microscope image is as shown in Figure 4 As shown in the figure, it can be clearly seen that the size of the microparticles is about 5 μm.

[0048] Meanwhile, through calculation and comparison, when the green CsPbBr3 perovskite nanocrystal is synthesized by using the ordinary hot injection method, the utilization rate of the raw material PbBr2 is 68%, the anti-solvent method is 72%, and the preparation method of the embodiment of the present application can reach 84%.

[0049] The green CsPbBr3 perovskite nanocrystal material obtained is added into the UV curing glue compatible with quantum dots at a mass ratio of 1:10, stirred until completely dispersed, and a green light conversion film is formed between two layers of polyethylene terephthalate (PET) films by using a scraping process, as shown in Figure 5 As shown in the figure, it can be clearly seen that the size of the microparticles is about 5 μm.

[0050] The film of the green CsPbBr3 perovskite nanocrystal material is placed in a 100% relative humidity environmental test chamber for aging test, and the stability of the material is good.

[0051] Experimental Example 2, Preparation of Black PbS Group II-VI Nanocrystal Material PbO and ODE are dissolved in 500 ml of oleic acid (OA) at a molar ratio of 0.5:1 to form a light yellow lead oleate precursor solution I, and TMS and ODE are mixed at a volume ratio of 0.2:10 to form a precursor solution II. After stirring for 2 hours, the precursor solution I is heated to 130°C for 1 hour, and then spray drying is performed after it is stabilized. The preparation device of the above embodiment one and the preparation method of the above embodiment two are used. The working frequency of the ultrasonic atomization nozzle 2 is 60 kHz, the feeding speed of the precursor solution I is 2 ml / s, the feeding speed of the precursor solution II is 0.5 ml / s, and the mixed solution of the precursor solution I and the precursor solution II in the micro-nano droplets is introduced into the temperature control chamber 4 with nitrogen flow. The temperature in the temperature control chamber 4 is 120°C, the generated black PbS group II-VI nanocrystal micro-nano droplets are introduced into the low-pressure chamber 6 with nitrogen flow, the gas pressure in the low-pressure chamber 6 is 200 Pa, and the nitrogen gas is heated to 220°C by the resistance wire at the same time. After drying, the black PbS group II-VI nanocrystal material is obtained.

[0052] The luminescence spectrum of the obtained black PbS group II-VI nanocrystal material is as shown in Figure 7As shown, the emission peak is located at 1435 nm, the half-peak width is 39 nm, and the fluorescence quantum yield is over 70%. According to the optical properties, it can be inferred that the size of the black PbS II-VI nanocrystal material is about 4 nm. Meanwhile, through calculation and comparison, when the black PbS II-VI nanocrystal is synthesized by using the ordinary hot injection method, the utilization rate of the raw material PbO is 75%, the anti-solvent method is 78%, and the preparation method of the embodiment of the present application can reach 89%.

[0053] Experimental Example 3, Preparation of Green InP III-V Nanocrystal Material InCl3, OAm and ODE were mixed in a molar ratio of 0.2:3:7, vacuum dried at 100℃ for 1h, then heated to 130℃ and kept for 1h to form precursor solution I; 2mmol (DMA)3P was added to 3.626ml DDE and stirred uniformly to form precursor solution II. The spray drying operation was carried out by using the preparation device of the above-mentioned embodiment one and the preparation method of the above-mentioned embodiment two. The working frequency of the ultrasonic atomization nozzle 2 was 50khz, the feeding speed of the precursor solution I was 3ml / s, the feeding speed of the precursor solution II was 0.3ml / s, the mixed solution of the precursor solution I and the precursor solution II in the micro-nano droplets flowed into the temperature control chamber 4 with nitrogen, the temperature in the temperature control chamber 4 was 200℃, the generated green InP III-V nanocrystal micro-nano droplets flowed into the low-pressure chamber 6 with nitrogen, the gas pressure in the low-pressure chamber 6 was 200Pa, and the nitrogen was heated to 220℃ by the resistance wire, and the green InP III-V nanocrystal material was obtained after drying. Through calculation and comparison, when the green InP III-V nanocrystal is synthesized by using the ordinary hot injection method, the utilization rate of the raw material InCl3 is 72%, the anti-solvent method is 82%, and the preparation method of the embodiment of the present application can reach 90%.

[0054] Experimental Example 4, Recycling of Solvent I and Solvent II in the Preparation Process of Green CsPbBr3 Perovskite Nanocrystal Material On the basis of the experimental example 1, the green CsPbBr3 perovskite nanocrystal material was separated from the evaporated solvent by the cyclone separator 9 after drying in the low-pressure chamber 6, entered the material collecting tank, the evaporated solvent was introduced into the recovery tank body after condensation in the condenser, the recovery tank body was kept at 5℃ for 2 hours, and the mixed solution of the solvent I (ODE) and the solvent II (OA) was collected after removing the wall sticking materials by the rotary scraper treatment, and the OA crystal was obtained by centrifugal separation at 3000rpm, and the crystal was washed with n-hexane at 0℃ to remove the residual ODE; the supernatant was passed through the basic alumina column (pH=9~10) to adsorb a small amount of OA; the ODE recovery rate was 93.5%, and the purity was 99.7% (FTIR verified no carboxyl peak); the OA recovery rate was 88.2%, and the APHA colority of the esterified OA was reduced from 120 to 15, which could save the solvent cost.

[0055] It should be noted that according to the needs of implementation, each method / step described in the embodiments of the present application can be split into more methods / steps, two or more methods / steps or parts of methods / steps can be combined into new methods / steps, and part of the raw materials can be replaced by other kinds of raw materials with corresponding functions to achieve the purpose of the embodiments of the present application.

[0056] The above embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as the limitation of the patent scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An apparatus for preparing nanocrystals, characterized by, The ultrasonic atomization nozzle and the sequentially connected gas source mechanism, temperature control chamber and low pressure chamber are included. The ultrasonic atomization nozzle includes at least two liquid inlets, and the feed pumps of the precursor solution I and the precursor solution II are connected to the liquid inlets respectively. The outlet end of the ultrasonic atomization nozzle is connected to the gas inlet pipe of the temperature control chamber. The gas source mechanism is used to introduce gas flow into the temperature control chamber. The temperature control mechanism is arranged outside the temperature control chamber, and the heating mechanism is arranged in the connecting pipe between the outlet end of the temperature control chamber and the inlet end of the low pressure chamber.

2. The apparatus of claim 1, wherein the apparatus is configured to produce nanocrystals having a size of less than 100 nm. The bottom of the low pressure chamber is provided with a material collecting port, and the low pressure chamber is further connected to the air pump for keeping the low pressure chamber at a set pressure.

3. A method for producing nanocrystals using the production apparatus according to claim 1 or 2, characterized by, The preparation device further includes a material collecting mechanism, which includes a cyclone separator, a condenser, a solvent recovery tank and a gas recovery tank. The preparation device further includes a material collecting mechanism, which includes a cyclone separator, a condenser, a solvent recovery tank and a gas recovery tank. The preparation device further includes a material collecting mechanism, which includes a cyclone separator, a condenser, a solvent recovery tank and a gas recovery tank. S0, the gas source mechanism is controlled to introduce gas flow into the temperature control chamber, the air pump is controlled to exhaust air from the low pressure chamber, and the low pressure chamber is kept at a set pressure; the temperature control mechanism is controlled to start to keep the temperature in the temperature control chamber at a first set temperature, and the heating mechanism is controlled to start to heat the gas flow flowing into the low pressure chamber to a second set temperature; S1, the high-temperature precursor solution I and the normal-temperature precursor solution II are simultaneously injected into the ultrasonic atomization nozzle, mixed and ultrasonically atomized into precursor micro-nano droplets; S2, the gas flow carries the precursor micro-nano droplets to spray in the temperature control chamber, so that the mixed solution of the precursor solution I and the precursor solution II in the micro-nano liquid reacts at a set temperature for a set time to obtain nanocrystal micro-nano droplets; 4. The method of claim 3, wherein the nanocrystals are prepared by the method of claim 1 or 2. S3, the gas flow carries the nanocrystal micro-nano droplets into the low pressure chamber, and the nanocrystal micro-nano droplets are dried by the low pressure hot gas flow to obtain nanocrystal materials.

5. The method of claim 3, wherein the nanocrystals are prepared by the method of claim 1. The size of the micro-nano droplets is 100 nm to 100 μm, and the particle size of the nanocrystal materials is 3 nm to 90 nm.

6. The method for preparing nanocrystals according to claim 3, characterized in that, The set pressure is 50 Pa to 10,000 Pa, the set time is 0.1 min to 120 min, and the nanocrystal micro-nano droplets are dried in the low pressure chamber for 3 s to 600 s. The ratio of the feeding speed of the precursor solution I to the feeding speed of the precursor solution II is 1:1 to 5:10, the working frequency of the ultrasonic atomization nozzle is 5 kHz to 80 kHz, and the feeding speed is 0.1 ml / s to 4 ml / s. The temperature of the precursor solution I is 100℃ to 400℃, the temperature control mechanism controls the temperature in the temperature control chamber to be-40℃ to 400℃, and the heating mechanism heats the flowing gas flow to 60℃ to 300℃.

7. The method of claim 3-6, wherein the method further comprises, The precursor solution I comprises at least one of a group II metal ion compound, a group III metal ion compound, an A-site cation compound or a B-site cation compound, a group I cation compound; the precursor solution II comprises at least one of a group VI element compound, a group V element compound, a halogen element compound; and the nanocrystal material comprises a group II-VI, a group III-V, a metal halide perovskite and a group I-III-VI.

8. The method of claim 7, wherein the nanocrystals are prepared by a method comprising: The group II metal ion compound is at least one of CdO, Cd(OH)2, CdX2, HgX2, Cd(CH3COO)2, Cd(acac)2, Cd(St)2, Cd(OA)2, ZnEt2, Zn(La)2, Zn(CH3COO)2, Zn(St)2, Mg(acac)2, wherein X is a halogen element; The group III metal ion compound is at least one of InX3, GaX3, In(acac)3, In(CH3COO)2, In(My)3, TMIn, TEGa, Ga(acac)3, Ga(CH3COO)2, Ga(tBu)3, TMAl, wherein X is a halogen element; The A-site cation compound is at least one of Cs2CO3, Cs(CH3COO), CsX, FAX, MAX, and the B-site cation compound is at least one of PbX2, Pb(CH3COO)2, PbCO3, SnX2, GeX2, wherein X is a halogen element; The group I cation compound is at least one of Cu(OA), CuX, Cu(acac)2, Cu(CH3COO)2, CuSCN, Ag2S, AgOA, AgNO3, AgTFA, Ag(CH3COO), AuX, AuSTm, wherein X is a halogen element; S8, TOP-Se, TMS-Se, TOP-S, TMS-S, S-OAm, TeO, TOP-Te, TeO2, TMS-Te, (NH2)2CS, Se, (NH2)2CSe, (C6H5)2Se2, C3H6O2Se, C 12 H 25 at least one of S, SH, and Se. The group V element compound is at least one of TMS3As, As0, (CH3)3CAsH2, SbCl3, Sb0, Sb(CH3COO)3, PH3, AsH3, (TMS)3P, (DMA)3P, (C4H9)PH2, (C4H9O)3PO, TOP, P4, P(NMe2)3; The halogen element compound is at least one of HX, NH4X, PX3, tetrabutylammonium halide TBAX, trimethylsilane halide TMS-X, wherein X is a halogen element.

9. The method for preparing nanocrystals according to claim 7, characterized in that, In step S1, the compound c is also injected into the ultrasonic atomization nozzle at the same time as the precursor solution I and the precursor solution II; the compound c is selected from at least one of oleic acid, oleylamine, oleic acid bromide, bromo-octylamine, dodecyl mercaptan, dodecylamine, tetrabutylammonium iodide, trioctylphosphine, trioctylphosphine oxide, tetradecylphosphonic acid, mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, mercaptoethylamine, cysteine, glutathione, ammonium perfluorooctanoate, polyethylene glycol mercaptan, dihydrolipoic acid, guanidine thiocyanate.

10. The method of claim 7, wherein the nanocrystals are prepared by a method comprising: The precursor solution I further comprises a solvent I; the solvent I is an organic solvent selected from at least one of N,N-dimethylformamide, dimethylsulfoxide, n-hexane, octadecene, trimethylphosphate, triethylphosphate, N-methylpyrrolidone, dimethylacetamide; and / or, ​ The precursor solution II further comprises a solvent II selected from at least one of tetrahydrofuran, pentyl acetate, toluene, acetone, n-hexane, octane, octadecene.

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