High-performance quantum dot material with core-shell structure as well as preparation method and application of high-performance quantum dot material

Abstract

The invention provides a core-shell structure high-performance quantum dot material and a preparation method and application thereof, and belongs to the technical field of quantum dot materials. A NaHTe aqueous solution is added into a solution containing sodium citrate and cadmium salt, glutathione and a zinc precursor solution are added, a reaction is performed to prepare sodium citrate modified CdTe / CdS / ZnS quantum dots, the sodium citrate modified CdTe / CdS / ZnS quantum dots react with black phosphorus quantum dots, nitrogen-doped sulfur quantum dots and mercaptoacetic acid to prepare a compound, and then the compound is coated with a silicon dioxide layer to prepare the core-shell structure high-performance quantum dot material. The core-shell structure high-performance quantum dot material prepared by the invention has better photoelectric efficiency and high quantum efficiency, the service life is prolonged, the resistance of quantum dots to environments such as oxygen and moisture is improved, the retention rate of optical performance is increased, and the core-shell structure high-performance quantum dot material has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of quantum dot materials technology, specifically to a core-shell structured high-performance quantum dot material, its preparation method, and its applications. Background Technology

[0002] Quantum dots (QDs) are nanomaterials with a particle size ranging from 1 to 20 nanometers and possessing a crystalline structure. They exhibit excellent optical properties, such as narrow full width at half maximum (FWHM), strong optical stability, continuously controllable wavelength, and high quantum efficiency, and have been widely used in many fields, including displays, lighting, solar energy, and biomarking. Because the size of quantum dots is within the bulk exciton radius, and excitons always reside on the surface of the quantum dot, the exciton state properties of quantum dots are greatly influenced by the surface properties of the quantum dots. After nearly forty years of development in quantum dot synthesis, in order to reduce the impact of surface effects on quantum dot performance, materials researchers have regrown one or more shell materials or inert inorganic shells with continuously widened band gaps on the surface of quantum dot nuclei. This can effectively reduce the defect state energy levels introduced by lattice defects on the surface of quantum dot nuclei, and avoid the energy loss in the excited state of quantum dots in the form of light or heat due to the capture of electrons and holes by defect energy levels. The coating of wide band gap shells improves the optical properties and stability of quantum dot nuclei, such as CdS, ZnSe, ZnS, ZnSeS, CdZnSe, and CdZnS.

[0003] Currently, the common methods for coating the surface of quantum dot nuclei are high-temperature implantation and alternating ion layer adsorption growth. High-temperature implantation involves injecting the precursor material required for the shell layer onto the surface of the quantum dot nucleus in a single step. However, due to the simultaneous introduction of large amounts of anion and cation precursors, mutual nucleation between the anion and cation precursors is inevitable. Alternating ion layer adsorption growth involves alternately implanting anion and cation precursors onto the surface of the quantum dot nucleus, sequentially coating the surface with a shell layer. While this method effectively avoids the mutual nucleation problem of the high-temperature implantation method, it requires layer-by-layer shell growth on the surface of the quantum dot nucleus, taking several hours per preparation, resulting in a long processing time. Furthermore, due to the anisotropy of the crystal planes, the quantum dot morphology tends to develop anisotropically, making it difficult to obtain quantum dot materials with regular morphologies using either high-temperature implantation or alternating ion layer adsorption growth. Summary of the Invention

[0004] The purpose of this invention is to propose a core-shell structured high-performance quantum dot material, its preparation method, and its applications. This material has good photoelectric efficiency, high quantum efficiency, and extended lifespan. It also improves the quantum dot's resistance to environments such as oxygen and humidity, and extends the retention rate of its optical properties, thus showing broad application prospects.

[0005] The technical solution of this invention is implemented as follows: This invention provides a method for preparing a core-shell structured high-performance quantum dot material. NaHTe aqueous solution is added to a solution containing sodium citrate and cadmium salt, followed by the addition of glutathione and zinc precursor solutions. The reaction yields sodium citrate-modified CdTe / CdS / ZnS quantum dots, which are then reacted with black phosphorus quantum dots, nitrogen-doped sulfur quantum dots, and mercaptoacetic acid to obtain a composite. Finally, a silica layer is coated onto the composite to obtain the core-shell structured high-performance quantum dot material.

[0006] As a further improvement to the present invention, the following steps are included: S1. Preparation of NaHTe aqueous solution: Tellurium powder and reducing agent are mixed and added to water, placed in a sealed container, and the gas produced by the reaction is discharged through an outlet tube. The reaction is stirred, allowed to stand, centrifuged, and the supernatant is collected to obtain NaHTe aqueous solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: Cadmium salt was dissolved in water, sodium citrate was added, the pH of the solution was adjusted, NaHTe aqueous solution was added under inert gas protection to form CdTe precursor solution, heated to boiling, and then glutathione and zinc precursor solutions were added. The reaction was carried out under ultraviolet light irradiation to obtain sodium citrate-modified CdTe / CdS / ZnS quantum dots. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and sulfuric acid were used as anode, cathode and electrolyte respectively. A voltage was applied to the black phosphorus electrode at low temperature to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous filter membrane. The separated nano-black phosphorus was washed with deoxygenated water until neutral. Inert gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: Sublimed sulfur, ethylenediamine, and thiourea were mixed and subjected to hydrothermal reaction. The solvent was removed under reduced pressure, ethanol was added to precipitate the mixture, centrifuged, the solid was collected, and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: Black phosphorus quantum dots and nitrogen-doped sulfur quantum dots were added to water, and sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and mercaptoacetic acid. The reaction was carried out under inert gas protection and irradiated with ultraviolet light to obtain the composite material. S6. Preparation of high-performance quantum dot materials with core-shell structure: The composite was added to a mixed solution of ammonia and NaOH and incubated for reaction. Then, alkyl orthosilicate and polydiallyl dimethylammonium hydrochloride were added and mixed evenly to obtain an aqueous phase. Cyclohexane, n-hexanol, and surfactant were mixed evenly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for reaction. Then, isopropanol was added to break the emulsion. After centrifugation, washing, and drying, the high-performance quantum dot material with core-shell structure was obtained.

[0007] As a further improvement of the present invention, the mass ratio of tellurium powder to reducing agent in step S1 is 2-4:1-3, the reducing agent is sodium borohydride, and the stirring reaction is carried out under an ice-water bath for 1-3 hours.

[0008] As a further improvement of the present invention, the cadmium salt in step S2 is cadmium chloride or cadmium nitrate, and the mass ratio of the cadmium salt, sodium citrate, NaHTe aqueous solution, glutathione and zinc precursor solution is 2-4:1-2:15-25:4-6:10-15. The pH value of the solution is adjusted to 8.5-9.5, and the heating and boiling time is 0.5-1.5 h. The zinc precursor solution is prepared as follows: 0.5-0.7 parts by weight of zinc acetate is dissolved in 100 parts by weight of water, 2-4 parts by weight of mercaptoacetic acid is added, and the pH value of the solution is adjusted to 8.5-9.5 to obtain the zinc precursor solution. The heat preservation and ultraviolet light irradiation reaction time is 20-40 min, and the ultraviolet light wavelength range is 300-400 nm.

[0009] As a further improvement of the present invention, the concentration of sulfuric acid in step S3 is 0.5-1.5 mol / L, the low temperature is -5 to -10°C, the applied voltage is 8-10V, and the diameter of the microporous filter membrane is 0.1 μm.

[0010] As a further improvement of the present invention, the mass ratio of sublimed sulfur, ethylenediamine and thiourea in step S4 is 1-3:15-25:0.01-0.015, the hydrothermal reaction temperature is 160-180℃ and the time is 4-6h.

[0011] As a further improvement of the present invention, the mass ratio of black phosphorus quantum dots, nitrogen-doped sulfur quantum dots, sodium citrate-modified CdTe / CdS / ZnS quantum dots and mercaptoacetic acid in step S5 is 1-3:3-5:7-10:2-4, the heating and ultraviolet irradiation reaction time is 20-40 min, the temperature is 80-90℃, and the ultraviolet wavelength range is 300-400 nm.

[0012] As a further improvement of the present invention, the concentration of ammonia in step S6 is 20-25 wt%, the concentration of NaOH solution is 0.5-1.5 mol / L, the incubation reaction time is 30-50 min, the mass ratio of the complex, water, ammonia, NaOH solution, alkyl orthosilicate, and polydiallyl dimethylammonium hydrochloride is 3-5:70:1-2:1-2.2:5-8:2-4, the volume ratio of cyclohexane, n-hexanol, and surfactant is 10-15:1-3:2-4, and the stirring reaction time is 2-4 days.

[0013] This invention further protects a core-shell structured high-performance quantum dot material prepared by the above-described preparation method.

[0014] This invention further protects the application of the above-mentioned core-shell structured high-performance quantum dot material in the preparation of display-related products.

[0015] The present invention has the following beneficial effects: Cadmium-based quantum dots possess remarkable optical and electrical properties and are generally spherical in structure. However, due to the presence of numerous defect states on their surface after synthesis and their tendency to aggregate, the optical performance and stability of the materials are greatly affected. Therefore, it is necessary to effectively improve the fluorescence performance of quantum dots and enhance the photoelectric effect by adding shell structures and surface ligand coatings.

[0016] This invention prepares sodium citrate-modified core-shell quantum dots (CdTe / CdS / ZnS), which provide the foundation for excellent optical performance. The high carrier migration characteristics of black phosphorus quantum dots compensate for the insufficient charge transport of traditional quantum dots, while nitrogen-doped sulfur quantum dots enhance surface activity through heteroatom regulation. These three components synergistically improve the optical response, charge transport, and surface functionality of the prepared composite. Mercaptoacetic acid (MGA) is highly sensitive to ultraviolet light; under ultraviolet light, MGA undergoes cleavage, releasing sulfur dioxide (S). 2- This provides raw materials for the growth of the ZnS shell. Simultaneously, the introduction of mercaptoacetic acid achieves tight bonding between quantum dots through coordination. The combination of inert gas and ultraviolet light suppresses oxidation side reactions during the recombination process, ensuring the integrity of the composite structure. This overcomes the performance limitations of single quantum dots, solving the problem of easy charge recombination in traditional quantum dots in optoelectronic devices, and significantly improves quantum efficiency.

[0017] Finally, this invention employs a reverse microemulsion method to construct a silicon-based shell. Utilizing the nanoscale spatial confinement effect of microemulsion droplets, precise control of the shell thickness can be achieved, solving the problem of uneven particle size in traditional coatings. The cationic properties of polydiallyl dimethylammonium hydrochloride and the electrostatic interaction with the quantum dot surface ligands ensure uniform deposition of the silicon source on the composite particle surface. The mixed alkali system of ammonia and NaOH provides a suitable pH environment for the hydrolysis and polycondensation of orthosilicate alkyl esters, thus enabling the formation of a uniform shell. The inner layer of this composite material is passivated by dual ligands of glutathione and sodium citrate, reducing the surface defect state density of the composite core. The outer layer, a dense silicon shell prepared by the reverse microemulsion method, not only blocks corrosive media such as oxygen and water but also, through doping modification with the electrolyte polydiallyl dimethylammonium hydrochloride, imparts a certain degree of conductivity to the shell, avoiding the obstruction of charge transport by traditional insulating shells. This achieves a balance between stability and functionality, improving service life and the retention of optical performance.

[0018] The core-shell structured high-performance quantum dot material prepared by this invention has good photoelectric efficiency, high quantum efficiency, and extended service life. It also improves the resistance of quantum dots to environments such as oxygen and humidity, and prolongs the retention rate of its optical properties, showing broad application prospects. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a TEM image of the core-shell structured high-performance quantum dot material prepared in Example 1. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 This embodiment provides a method for preparing a core-shell structured high-performance quantum dot material, including the following steps: S1. Preparation of NaHTe deionized water solution: Mix 2g tellurium powder and 1g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 1h under an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 2g of cadmium chloride was dissolved in 100mL of deionized water, 1g of sodium citrate was added, the pH of the solution was adjusted to 8.5, and under nitrogen protection, 15g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 0.5h, and then 4g of glutathione and 10g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 20min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.5g of zinc acetate is dissolved in 100mL of deionized water, 2g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 8.5 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 0.5 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 8V was applied to the black phosphorus electrode at -5℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: 1g of sublimed sulfur, 15g of ethylenediamine and 0.01g of thiourea were mixed and hydrothermally reacted at 160℃ for 4h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: 1g of black phosphorus quantum dots and 3g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, 7g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 2g of mercaptoacetic acid, and the mixture was heated to 80℃ under nitrogen protection and irradiated with ultraviolet light for 20min. The ultraviolet light wavelength range was 30nm to obtain the composite. S6. Preparation of high-performance quantum dot materials with core-shell structure: 3g of the composite was added to 70g of water, followed by 2g of 25wt% ammonia and 2.2g of 0.5mol / L NaOH solution. The mixture was incubated for 30min. Then, 5g of tetraethyl orthosilicate and 2g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 100mL of cyclohexane, 10mL of n-hexanol, and 20mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 2 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure. Figure 1 The image shows a TEM image of the core-shell structured high-performance quantum dot material. As can be seen from the image, a core-shell structure has been formed.

[0023] Example 2 This embodiment provides a method for preparing a core-shell structured high-performance quantum dot material, including the following steps: S1. Preparation of NaHTe deionized water solution: Mix 4g tellurium powder and 3g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 3h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 4g of cadmium nitrate was dissolved in 100mL of deionized water, 2g of sodium citrate was added, the pH of the solution was adjusted to 9.5, and under nitrogen protection, 25g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1.5h, and then 6g of glutathione and 15g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 40min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.7g of zinc acetate is dissolved in 100mL of deionized water, 4g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9.5 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 1.5 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 10V was applied to the black phosphorus electrode at -10℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: 3g of sublimed sulfur, 25g of ethylenediamine and 0.015g of thiourea were mixed and hydrothermally reacted at 180℃ for 6h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: 3g of black phosphorus quantum dots and 5g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, 10g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 4g of mercaptoacetic acid, and the mixture was heated to 90℃ under nitrogen protection and irradiated with ultraviolet light for 40min. The ultraviolet light wavelength range was 350nm to obtain the composite. S6. Preparation of high-performance quantum dot materials with core-shell structure: 5g of the composite was added to 70g of water, along with 1g of 25wt% ammonia and 1g of 1.5mol / L NaOH solution. The mixture was incubated for 50min. Then, 8g of tetraethyl orthosilicate and 4g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 150mL of cyclohexane, 30mL of n-hexanol, and 40mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 4 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0024] Example 3 This embodiment provides a method for preparing a core-shell structured high-performance quantum dot material, including the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, 1.5g of sodium citrate was added, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 1 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 9V was applied to the black phosphorus electrode at -7℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: 2g of sublimed sulfur, 20g of ethylenediamine and 0.012g of thiourea were mixed and hydrothermally reacted at 170℃ for 5h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: 2g of black phosphorus quantum dots and 4g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, 8.5g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 3g of mercaptoacetic acid, and the mixture was heated to 85℃ under nitrogen protection and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm to obtain the composite. S6. Preparation of high-performance quantum dot materials with core-shell structure: 4g of the composite was added to 70g of water, along with 1.5g of 22wt% ammonia and 1.8g of 1mol / L NaOH solution. The mixture was incubated for 40min. Then, 7g of tetraethyl orthosilicate and 3g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 120mL of cyclohexane, 20mL of n-hexanol, and 30mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 3 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0025] Comparative Example 1 The difference from Example 3 is that sodium citrate was not added in step S2.

[0026] Includes the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 1 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 9V was applied to the black phosphorus electrode at -7℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: 2g of sublimed sulfur, 20g of ethylenediamine and 0.012g of thiourea were mixed and hydrothermally reacted at 170℃ for 5h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: 2g of black phosphorus quantum dots and 4g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, 8.5g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 3g of mercaptoacetic acid, and the mixture was heated to 85℃ under nitrogen protection and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm to obtain the composite. S6. Preparation of high-performance quantum dot materials with core-shell structure: 4g of the composite was added to 70g of water, along with 1.5g of 22wt% ammonia and 1.8g of 1mol / L NaOH solution. The mixture was incubated for 40min. Then, 7g of tetraethyl orthosilicate and 3g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 120mL of cyclohexane, 20mL of n-hexanol, and 30mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 3 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0027] Comparative Example 2 The difference from Example 3 is that black phosphorus quantum dots were not added in step S5.

[0028] Includes the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, 1.5g of sodium citrate was added, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of nitrogen-doped sulfur quantum dots: 2g of sublimed sulfur, 20g of ethylenediamine and 0.012g of thiourea were mixed and hydrothermally reacted at 170℃ for 5h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S4. Nitrogen-doped sulfur quantum dot embedding: 6g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, 8.5g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 3g of mercaptoacetic acid were added, and the mixture was heated to 85℃ under nitrogen protection and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm to obtain the composite. S5. Preparation of high-performance quantum dot materials with core-shell structure: 4g of the composite was added to 70g of water, along with 1.5g of 22wt% ammonia and 1.8g of 1mol / L NaOH solution. The mixture was incubated for 40min. Then, 7g of tetraethyl orthosilicate and 3g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 120mL of cyclohexane, 20mL of n-hexanol, and 30mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 3 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0029] Comparative Example 3 The difference from Example 3 is that nitrogen-doped sulfur quantum dots were not added in step S5.

[0030] Includes the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, 1.5g of sodium citrate was added, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 1 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 9V was applied to the black phosphorus electrode at -7℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Black phosphorus quantum dot encapsulation: 6g of black phosphorus quantum dots were added to 100mL of deionized water, 8.5g of sodium citrate was added to modify CdTe / CdS / ZnS quantum dots and 3g of mercaptoacetic acid were added, and the mixture was heated to 85℃ under nitrogen protection and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm to obtain the complex. S5. Preparation of high-performance quantum dot materials with core-shell structure: 4g of the composite was added to 70g of water, along with 1.5g of 22wt% ammonia and 1.8g of 1mol / L NaOH solution. The mixture was incubated for 40min. Then, 7g of tetraethyl orthosilicate and 3g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 120mL of cyclohexane, 20mL of n-hexanol, and 30mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 3 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0031] Comparative Example 4 The difference from Example 3 is that steps S3 to S5 were not performed.

[0032] Includes the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, 1.5g of sodium citrate was added, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of high-performance quantum dot materials with core-shell structure: 4g of sodium citrate-modified CdTe / CdS / ZnS quantum dots were added to 70% water, along with 1.5g of 22wt% ammonia and 1.8g of 1mol / L NaOH solution. The mixture was incubated for 40min. Then, 7g of tetraethyl orthosilicate and 3g of polydiallyl dimethylammonium hydrochloride were added and mixed thoroughly to obtain an aqueous phase. Separately, 120mL of cyclohexane, 20mL of n-hexanol, and 30mL of Triton X-100 were mixed thoroughly to obtain a reverse microemulsion system. The aqueous phase was added to the reverse microemulsion system and stirred for 3 days. Then, 200mL of isopropanol was added to break the emulsion. The mixture was centrifuged, washed, and dried to obtain the high-performance quantum dot material with core-shell structure.

[0033] Comparative Example 5 The difference from Example 3 is that step S6 was not performed.

[0034] Includes the following steps: S1. Preparation of NaHTe deionized water solution: Mix 3g tellurium powder and 2g sodium borohydride and add to 100mL deionized water. Add to a sealed container and use an outlet tube to remove the gas generated by the reaction. Stir the reaction for 2h in an ice deionized water bath, let it stand at 4℃ for 6h, centrifuge, collect the supernatant, and obtain NaHTe deionized water solution. S2. Preparation of sodium citrate-modified core-shell quantum dots: 3g of cadmium chloride was dissolved in 100mL of deionized water, 1.5g of sodium citrate was added, the pH of the solution was adjusted to 9, and under nitrogen protection, 20g of NaHTe deionized water solution was added to form a CdTe precursor solution. The solution was heated to boiling for 1h, and then 5g of glutathione and 12g of zinc precursor solution were added. The solution was kept warm and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm, and sodium citrate-modified CdTe / CdS / ZnS quantum dots were obtained. The zinc precursor solution is prepared as follows: 0.6 g of zinc acetate is dissolved in 100 mL of deionized water, 3 g of mercaptoacetic acid is added, and the pH of the solution is adjusted to 9 to obtain the zinc precursor solution. S3. Preparation of black phosphorus quantum dots: Black phosphorus, platinum wire and 1 mol / L sulfuric acid were used as the anode, cathode and electrolyte, respectively. A voltage of 9V was applied to the black phosphorus electrode at -7℃ to prepare nano-black phosphorus. Unpeeled black phosphorus was filtered out. The nano-black phosphorus in the filtrate was separated by a microporous membrane with a diameter of 0.1 μm. The separated nano-black phosphorus was washed with deoxygenated deionized water until neutral. Nitrogen gas was introduced during the washing process to prevent oxidation of the nano-black phosphorus. The product was freeze-dried to obtain black phosphorus quantum dots. S4. Preparation of nitrogen-doped sulfur quantum dots: 2g of sublimed sulfur, 20g of ethylenediamine and 0.012g of thiourea were mixed and hydrothermally reacted at 170℃ for 5h. The solvent was removed under reduced pressure, 50mL of ethanol was added to precipitate for 1h, centrifuged, the solid was collected and freeze-dried to obtain nitrogen-doped sulfur quantum dots. S5. Black phosphorus quantum dot / nitrogen-doped sulfur quantum dot composite encapsulation: 2g of black phosphorus quantum dots and 4g of nitrogen-doped sulfur quantum dots were added to 100mL of deionized water, along with 8.5g of sodium citrate to modify CdTe / CdS / ZnS quantum dots and 3g of mercaptoacetic acid. Under nitrogen protection, the mixture was heated to 85℃ and irradiated with ultraviolet light for 30min. The ultraviolet light wavelength range was 350nm. The composite material was obtained, which is a core-shell structured high-performance quantum dot material.

[0035] Test Example 1 The high-performance quantum dot materials with core-shell structure prepared in Examples 1-3 and Comparative Example 5 were tested in phosphate buffer solutions with different pH values ​​to determine whether aggregation occurred. The results are shown in Table 1.

[0036] Table 1

[0037] As shown in the table above, the core-shell structured high-performance quantum dot materials prepared in Examples 1-3, protected by a silica shell, did not aggregate under various pH conditions. In contrast, Comparative Example 5, which was not protected, readily aggregated under both acidic and alkaline conditions.

[0038] Test Example 2 The core-shell structured high-performance quantum dot materials prepared in Examples 1-3 and Comparative Examples 1-5 were added to n-octane and ultrasonically dispersed to obtain a suspension. This suspension was then spin-coated onto a polycarbonate film at 3000 r / min for 60 s. The other side was treated in the same way and dried to obtain a quantum dot color conversion film. The brightness and quantum yield of the prepared quantum dot color conversion film were calculated by measuring the brightness spectrum using a spectroradiometer. A backlight unit of an LED (maximum emission wavelength of 620 nm) and a light guide plate were stacked on one surface of the prepared quantum dot color conversion film. A prism sheet and a dual brightness enhancement film (DBEF) were stacked on the other surface of the quantum dot color conversion film, and then the brightness spectrum of the film was measured. Initial values ​​were set such that the brightness of the LED lamp was 600 nits (nits) in the absence of the quantum dot color conversion film when measuring the brightness spectrum. The results are shown in Table 2.

[0039] Table 2

[0040] As can be seen from the table above, the quantum dot color conversion films prepared by spin coating of the core-shell structured high-performance quantum dot materials obtained in Examples 1-3 of this invention have high brightness and high quantum yield.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a core-shell structure high-performance quantum dot material, characterized in that, The NaHTe aqueous solution is added into a solution containing sodium citrate and cadmium salt, a glutathione and zinc precursor solution is added, and reaction is performed to prepare sodium citrate modified CdTe / CdS / ZnS quantum dots, which are reacted with black phosphorus quantum dots, nitrogen-doped sulfur quantum dots and mercaptoacetic acid to prepare a composite, and then a silica layer is coated to prepare a high-performance quantum dot material with a core-shell structure.

2. The production method according to claim 1, characterized by, The method comprises the following steps: S1. Preparation of NaHTe aqueous solution: Te powder and a reducing agent are mixed and added into water, a closed container is used, a gas generated in the reaction is led out through a lead-out pipe, stirring reaction is performed, standing is performed, centrifugation is performed, and supernatant is collected to prepare the NaHTe aqueous solution; S2. Preparation of sodium citrate modified core-shell quantum dots: cadmium salt is dissolved in water, sodium citrate is added, the pH value of the solution is adjusted, under the protection of inert gas, the NaHTe aqueous solution is added to form a CdTe precursor solution, heating and boiling are performed, then the glutathione and zinc precursor solution is added, and ultraviolet light irradiation reaction is performed under heat preservation to prepare the sodium citrate modified CdTe / CdS / ZnS quantum dots; S3. Preparation of black phosphorus quantum dots: black phosphorus, platinum wire and sulfuric acid are used as an anode, a cathode and an electrolyte respectively, a voltage is applied to the black phosphorus electrode at low temperature to prepare nano black phosphorus, unpeeled black phosphorus is filtered out, the nano black phosphorus in the filtrate is separated by using a microporous filter membrane, the separated nano black phosphorus is washed to be neutral by using deoxygenated water, inert gas is introduced in the washing process to prevent oxidation of the nano black phosphorus, and the product is freeze-dried to prepare the black phosphorus quantum dots; S4. Preparation of nitrogen-doped sulfur quantum dots: sublimed sulfur, ethylenediamine and thiourea are mixed, hydrothermal reaction is performed, the solvent is removed under reduced pressure, ethanol is added for precipitation, centrifugation is performed, the solid is collected, and freeze-drying is performed to prepare the nitrogen-doped sulfur quantum dots; S5. Composite embedding of black phosphorus quantum dots / nitrogen-doped sulfur quantum dots: the black phosphorus quantum dots and the nitrogen-doped sulfur quantum dots are added into water, the sodium citrate modified CdTe / CdS / ZnS quantum dots and mercaptoacetic acid are added, and reaction is performed under heating and ultraviolet light irradiation under the protection of inert gas to prepare a composite; S6. Preparation of high-performance quantum dot material with a core-shell structure: the composite is added into a mixed solution of ammonia water and NaOH, incubation reaction is performed, then tetraethyl orthosilicate and polydiallyldimethylammonium chloride hydrochloride are added, the water phase is obtained after mixing uniformly; in addition, cyclohexane, n-hexanol and a surfactant are mixed uniformly to obtain a reverse microemulsion system; the water phase is added into the reverse microemulsion system, stirring reaction is performed, then isopropyl alcohol is added for demulsification, centrifugation, washing and drying are performed to prepare the high-performance quantum dot material with a core-shell structure.

3. The preparation method according to claim 2, characterized in that, In step S1, the mass ratio of the Te powder and the reducing agent is 2-4:1-3, the reducing agent is sodium borohydride, and the stirring reaction is performed under an ice water bath for 1-3 h.

4. The production method according to claim 2, characterized by, The cadmium salt in step S2 is cadmium chloride or cadmium nitrate, the mass ratio of the cadmium salt, sodium citrate, NaHTe aqueous solution, glutathione and zinc precursor solution is 2-4:1-2:15-25:4-6:10-15, the pH value of the adjusting solution is 8.5-9.5, the heating boiling time is 0.5-1.5h, the zinc precursor solution is prepared by dissolving 0.5-0.7 parts by weight of zinc acetate in 100 parts by weight of water, adding 2-4 parts by weight of mercaptoacetic acid, and adjusting the pH value of the solution to 8.5-9.5, the holding ultraviolet light irradiation reaction time is 20-40min, and the ultraviolet light wavelength range is 300-400nm.

5. The preparation method according to claim 2, characterized in that, The concentration of sulfuric acid in step S3 is 0.5-1.5mol / L, the temperature of the low temperature is-5 to-10℃, the applied voltage is 8-10V, and the diameter of the microporous filter membrane is 0.1μm.

6. The preparation method according to claim 2, characterized in that, The mass ratio of sublimed sulfur, ethylenediamine and thiourea in step S4 is 1-3:15-25:0.01-0.015, the hydrothermal reaction temperature is 160-180℃, and the time is 4-6h.

7. The preparation method according to claim 2, characterized in that, The mass ratio of black phosphorus quantum dots, nitrogen-doped sulfur quantum dots, sodium citrate modified CdTe / CdS / ZnS quantum dots and mercaptoacetic acid in step S5 is 1-3:3-5:7-10:2-4, the heating ultraviolet light irradiation reaction time is 20-40min, the temperature is 80-90℃, and the ultraviolet light wavelength range is 300-400nm.

8. The preparation method according to claim 2, characterized in that, The concentration of ammonia water in step S6 is 20-25wt%, the concentration of NaOH solution is 0.5-1.5mol / L, the incubation reaction time is 30-50min, the mass ratio of the complex, water, ammonia water, NaOH solution, tetraethyl orthosilicate and polydiallyldimethylammonium chloride hydrochloride is 3-5:70:1-2:1-2.2:5-8:2-4, the volume ratio of cyclohexane, n-hexanol and surfactant is 10-15:1-3:2-4, and the stirring reaction time is 2-4 days.

9. A core-shell structure high-performance quantum dot material prepared by the preparation method of any one of claims 1-8.

10. The use of the core-shell structure high-performance quantum dot material of claim 9 in the preparation of display-related products.

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