Quantum dot / liquid crystal nanocomposite, preparation method and application thereof

Abstract

The application belongs to the field of nanometer and solid light emitting materials, and particularly relates to a quantum dot / liquid crystal nanocomposite material and a preparation method and application thereof. A 3-mercapto propionic acid modified CdSe-ZnS green light quantum dot with a core-shell structure is prepared by a hot injection method; a thermotropic liquid crystal unit with a double sulfur end group is synthesized through an esterification reaction between thioctic acid and cholesterols; and then, the 3-mercapto propionic acid ligand on the CdSe-ZnS green light quantum dot is replaced by the thermotropic liquid crystal unit with the double sulfur end group through a chemical exchange reaction, so as to construct a liquid crystal functionalized CdSe-ZnS green light quantum dot material. The composite material provided by the application ingeniously combines the flexible tunable advantage of the liquid crystal itself and the controllable semiconductor fluorescent characteristics of the quantum dot, realizes the synergistic fluorescent regulation of the composite material in display application through the interaction between different components, and provides a new way for improving the structure and performance of a liquid crystal display panel.

Description

Technical Field

[0001] This invention belongs to the field of synthesis of nano and solid luminescent materials, and relates to a method for preparing green liquid crystal quantum dots, specifically to a quantum dot / liquid crystal nanocomposite material, its preparation method and its application in liquid crystal display panels. Background Technology

[0002] As the government places increasing emphasis on the development of the LCD industry, quantum dot TVs are attracting more and more attention. Unlike traditional LCD TVs, quantum dot TVs add a quantum dot film to the LED backlight. This structure significantly reduces wasted light, resulting in more vibrant and realistic colors. However, the presence of the liquid crystal layer increases the overall thickness of the display panel, which not only affects the aesthetics and portability of the TV but may also cause problems such as low refresh rates and slow response times, thus affecting the display of dynamic images. Furthermore, the poor flexibility of quantum dot materials severely hinders the application of quantum dot TVs in the field of flexible displays, contradicting the market trend of demanding thin, flexible display devices.

[0003] To address these challenges, researchers have made significant efforts to find suitable display materials for quantum dot-liquid crystal composites. One such attempt is the construction of quantum dot-liquid crystal binary systems, aiming to leverage the properties of quantum dots to improve the performance of liquid crystal-based devices, such as enhancing luminous efficiency, improving memory effect, and optimizing conductivity. However, the doping process for quantum dots is complex and delicate, requiring the proportion of quantum dots in the mixed system to be strictly limited to below 5% to avoid phase separation or nanoparticle deposition, both of which could negatively impact the stability and lifespan of the display panel. Therefore, how to flexibly construct quantum dot / liquid crystal nanocomposites, enabling luminescent quantum dots to effectively integrate with liquid crystal materials to achieve liquid crystal-quantum dot integration, has become a key technical challenge in developing high-performance quantum dot television LCD display panels. Summary of the Invention

[0004] In view of this, the present invention provides a quantum dot / liquid crystal nanocomposite material, its preparation method and application, based on the existing problems of quantum dot TV liquid crystal display panels. It can not only solve the shortcomings of quantum dot TV liquid crystal display panels in terms of thickness, quantum efficiency and flexibility, but also promote the development of display panels towards thinner, more efficient and more flexible directions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first technical objective of this invention is to provide a method for preparing quantum dot / liquid crystal nanocomposite materials. The composite material is prepared by hot injection method using 3-mercaptopropionic acid modified CdSe-ZnS green quantum dots with a core-shell structure; thermotropic liquid crystal units with disulfide end groups are synthesized through esterification reaction between lipoic acid and cholesterol; and then, some of the 3-mercaptopropionic acid ligands on the CdSe-ZnS green quantum dots are replaced with thermotropic liquid crystal units with disulfide end groups through chemical exchange reaction, thereby constructing a liquid crystal functionalized CdSe-ZnS green quantum dot material.

[0007] Furthermore, the preparation method of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure includes the following steps:

[0008] 1) Add cadmium sulfate solution and 3-mercaptopropionic acid solution to sodium hexametaphosphate solution, stir, and then add sodium hydroxide solution to obtain cadmium precursor solution;

[0009] 2) Selenium dioxide was added to a nitric acid solution, stirred, and then diluted with deionized water to obtain a selenium precursor solution;

[0010] 3) Under stirring conditions, the above selenium precursor solution was added to the cadmium precursor solution, hydrazine hydrate solution was added, the mixture was heated under reflux, centrifuged, and deionized water was added to obtain CdSe quantum dot solution;

[0011] 4) Under nitrogen purging and stirring, zinc sulfate solution and sodium sulfide solution were added dropwise to CdSe quantum dot solution, and the mixture was heated under reflux to obtain the reaction solution;

[0012] 5) Chloroform and 3-mercaptopropionic acid were added to the above reaction solution, and after heating and drying, CdSe-ZnS green quantum dots with a core-shell structure modified by 3-mercaptopropionic acid were obtained.

[0013] In step 1), the concentration of cadmium sulfate solution is 8-10 mmol / L, the mass fraction of 3-mercaptopropionic acid solution is 85-95%, the concentration of sodium hexametaphosphate solution is 12-16 mmol / L, the concentration of sodium hydroxide solution is 2-5 mol / L, and sodium hydroxide solution is added until the pH value of the precursor solution reaches ~12. The volume ratio of cadmium sulfate solution, 3-mercaptopropionic acid solution and sodium hexametaphosphate solution is 1000:1 to 3:1000.

[0014] In step 2), the mass fraction of the nitric acid solution is 65-75%, the volume ratio of the nitric acid solution to the selenium precursor solution is 1:3-5, and the selenium precursor solution is diluted to a selenium ion concentration of 0.05-0.15 mmol / L.

[0015] In steps 1) and 2), the molar ratio of cadmium sulfate to selenium dioxide is 1 to 2:13.

[0016] In step 3), the mass fraction of the hydrazine hydrate solution is 75-85%, the heating temperature is 90-110℃, the reflux time is 4-6h, the centrifugation speed is 6000-8000r / min, and the volume ratio of the hydrazine hydrate solution to the CdSe quantum dot solution is 1-2:25.

[0017] In step 4), the nitrogen purging time is 20-40 min, the concentration of zinc sulfate solution is 8-12 mol / L, the concentration of sodium sulfide solution is 8-12 mol / L, the dropping rate is 1 mL / min, the volume ratio of zinc sulfate solution to sodium sulfide solution is 1:1-2, the heating temperature is 90-110℃, and the reflux time is 6-8 h.

[0018] In step 5), the concentration of 3-mercaptopropionic acid is 0.08–0.12 mol / L, the volume ratio of chloroform to 3-mercaptopropionic acid is 10:1–2, the heating temperature is 50–70°C, and the heating time is 1–2 h.

[0019] Furthermore, the method for preparing the thermotropic liquid crystal unit with disulfide terminal groups includes the following steps:

[0020] 1) Add cholesterol, lipoic acid, and 4-dimethylaminopyridine to dichloromethane solvent, stir, and then add N,N'-diisopropylcarbodiimide;

[0021] 2) After stirring the above solution, rotary evaporation, column chromatography, and rotary evaporation were performed to obtain thermotropic liquid crystal units with disulfide terminal groups.

[0022] In step 1), the molar ratio of cholesterol, lipoic acid, 4-dimethylaminopyridine and N,N'-diisopropylcarbodiimide is 1-2:4:4:2, the volume ratio of dichloromethane solution and N,N'-diisopropylcarbodiimide is 20:1-2, and the stirring time is 30-50 min.

[0023] The stirring time in step 2) is 5 to 7 days, and the eluent used in the column chromatography is a mixed solution of ethyl acetate and n-hexane with a volume ratio of 1:4 to 10.

[0024] Furthermore, the preparation method of the liquid crystal functionalized CdSe-ZnS green quantum dot material includes the following steps:

[0025] 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure and thermotropic liquid crystal units with disulfide terminal groups were added to dichloromethane solvent and stirred. After centrifugation, the liquid crystal functionalized CdSe-ZnS green quantum dot material was obtained.

[0026] The mass ratio of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure to the thermotropic liquid crystal unit with disulfide terminal groups is 1-2:5; the volume of the dichloromethane solvent is 3-6 mL; the stirring time is 3-5 days; and the centrifugation speed is 6000-8000 r / min.

[0027] The second technical objective of this invention is to provide a quantum dot / liquid crystal nanocomposite material prepared by the method described above, wherein the quantum dot / liquid crystal nanocomposite material is a liquid crystal functionalized CdSe-ZnS green quantum dot material.

[0028] The third technical objective of this invention is to provide an application of the quantum dot / liquid crystal nanocomposite material prepared by the method described above in a liquid crystal display panel.

[0029] Compared with the prior art, the superior effects of the present invention are as follows:

[0030] (1) This invention constructs CdSe-ZnS green quantum dot / liquid crystal functional material by chemical bonding method, combining the flexible and tunable advantages of liquid crystal itself with the controllable semiconductor fluorescence properties of quantum dots, and develops a composite material with both light emission and liquid crystal functions.

[0031] (2) In this invention, the fluorescence emission peak of the green liquid crystal quantum dot is mainly distributed at 547nm, which is a high-intensity green light visible to the naked eye. The liquid crystal phase temperature range of the quantum dot is 64.1-90.7℃. After liquid crystal functionalization modification, the "quantum efficiency" of the quantum dot is greatly improved to 56%, which is suitable for use as a quantum dot TV liquid crystal display panel. The synthesis process is simple, easy to operate, and highly safe, making it suitable for laboratory research and industrial production. Attached Figure Description

[0032] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] Figure 1 The X-ray diffraction (XRD) pattern (a), absorption spectrum (b), and laser spectrum (c) of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure obtained in Example 1 are shown.

[0034] Figure 2 The images shown are polarized light microscope (POM) images (ac) and differential scanning calorimetry (DSC) images (d) of the thermotropic liquid crystal cell with disulfide terminal groups obtained in Example 1.

[0035] Figure 3 Transmission electron microscopy (TEM) images (a and b), POM image (c), and proton nuclear magnetic resonance (NMR) spectrum of the liquid crystal functionalized CdSe-ZnS green quantum dot material obtained in Example 1. 1 H NMR (d and e) and DSC plot (f).

[0036] Figure 4 The absorption spectrum (a), laser spectrum (b), and quantum efficiency spectrum (c) of the liquid crystal functionalized CdSe-ZnS green quantum dot material obtained in Example 1 are shown.

[0037] Figure 5 This is a thin-layer chromatography (TLC) chromatogram of the target liquid crystal cell obtained as a comparative example. Detailed Implementation

[0038] 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0040] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and techniques not specifically mentioned herein refer to experimental methods and techniques commonly used by one of ordinary skill in the art. Without conflict, the technical features disclosed in the embodiments of this application can be arbitrarily combined, and the resulting technical solutions belong to the content disclosed in the embodiments of this application.

[0041] To better understand the present invention, the following embodiments further illustrate the invention in detail, but these should not be construed as limiting the invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description are also considered to fall within the scope of protection of the present invention. The present invention will be further described in detail below with reference to the accompanying drawings, embodiments, and comparative examples.

[0042] Example 1:

[0043] 1. The preparation method of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure described in this embodiment is as follows:

[0044] 1) Add 20 mL (8.5 mmol / L) of cadmium sulfate solution and 60 μL of 3-mercaptopropionic acid solution (90%) to 20 mL (15 mmol / L) of sodium hexametaphosphate solution. After stirring, add (3 mol / L) sodium hydroxide solution until the pH value reaches ~12 to obtain the cadmium precursor solution.

[0045] 2) Add 0.029 g of selenium dioxide to 5 mL of nitric acid solution (70%), stir until completely dissolved, then add deionized water to dilute to 20 mL so that the concentration of selenium ions is 0.01 mmol / L, to obtain the selenium precursor solution.

[0046] 3) Under stirring conditions, the above selenium precursor solution was added to the cadmium precursor solution, 4 mL of hydrazine hydrate solution (80%) was added, and the mixture was heated under reflux at 100℃ for 5 h. After centrifugation with acetone solvent (7500 r / min, 5 min / time), deionized water was added to obtain CdSe quantum dot solution.

[0047] 4) Under nitrogen purging for 30 min and stirring, 1 mL (10 mol / L) zinc sulfate solution and 1 mL (10 mol / L) sodium sulfide solution were added dropwise to CdSe quantum dot solution at a rate of 1 mL / min. The solution was heated under constant temperature and reflux at 100℃ for 7 h to obtain the reaction solution.

[0048] 5) Add 1 mL of chloroform and 0.1 mL (0.1 mol / L) of 3-mercaptopropionic acid to 20 mg of the above reaction solution, heat at 60 °C for 1 h and dry to obtain 3-mercaptopropionic acid modified CdSe-ZnS green quantum dots with core-shell structure.

[0049] 2. The method for preparing the thermotropic liquid crystal unit with disulfide terminal groups described in this embodiment is as follows:

[0050] 1) Add 8.4g of cholesterol, 15.84g of lipoic acid, and 8.88g of 4-dimethylaminopyridine to 450ml of dichloromethane solvent, stir for 40min, and then add 38.4ml of N,N'-diisopropylcarbodiimide.

[0051] 2) After stirring the above solution for 6 days, rotary evaporation, column chromatography (eluent is a mixed solution of ethyl acetate and n-hexane with a volume ratio of 1:6), and rotary evaporation were performed to obtain thermotropic liquid crystal units with disulfide terminal groups.

[0052] 3. The preparation method of the liquid crystal functionalized CdSe-ZnS green quantum dot material described in this embodiment is as follows:

[0053] 3 mg of 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure and 10 mg of thermotropic liquid crystal units with disulfide terminal groups were added to 3 mL of dichloromethane solvent. After stirring for 3 days, the mixture was centrifuged with ethanol (6000 r / min, 5 min / time) to obtain the liquid crystal functionalized CdSe-ZnS green quantum dot material.

[0054] Example 2:

[0055] 1) Add 20 mL (8.5 mmol / L) of cadmium sulfate solution and 60 μL of 3-mercaptopropionic acid solution (90%) to 20 mL (15 mmol / L) of sodium hexametaphosphate solution. After stirring, add (3 mol / L) sodium hydroxide solution until the pH value reaches ~12 to obtain the cadmium precursor solution.

[0056] 2) Add 0.029 g of selenium dioxide to 5 mL of nitric acid solution (70%), stir until completely dissolved, then add deionized water to dilute to 20 mL so that the concentration of selenium ions is 0.01 mmol / L, to obtain the selenium precursor solution.

[0057] 3) Under stirring conditions, the above selenium precursor solution was added to the cadmium precursor solution, 4 mL of hydrazine hydrate solution (80%) was added, and the mixture was heated under reflux at 100℃ for 5 h. After centrifugation with acetone solvent (7500 r / min, 5 min / time), deionized water was added to obtain CdSe quantum dot solution.

[0058] 4) Under nitrogen purging for 30 min and stirring, 1 mL (12 mol / L) zinc sulfate solution and 1 mL (12 mol / L) sodium sulfide solution were added dropwise to CdSe quantum dot solution at a rate of 1 mL / min. The solution was heated under reflux at 100 °C for 7 h to obtain the reaction solution.

[0059] 5) Add 1 mL of chloroform and 0.1 mL (0.1 mol / L) of 3-mercaptopropionic acid to 20 mg of the above reaction solution, heat at 60 °C for 1 h and dry to obtain 3-mercaptopropionic acid modified CdSe-ZnS green quantum dots with core-shell structure.

[0060] Example 3:

[0061] 1) Add 20 mL (8.5 mmol / L) of cadmium sulfate solution and 60 μL of 3-mercaptopropionic acid solution (90%) to 20 mL (15 mmol / L) of sodium hexametaphosphate solution. After stirring, add (3 mol / L) sodium hydroxide solution until the pH value reaches ~12 to obtain the cadmium precursor solution.

[0062] 2) Add 0.029 g of selenium dioxide to 5 mL of nitric acid solution (70%), stir until completely dissolved, then add deionized water to dilute to 20 mL so that the concentration of selenium ions is 0.01 mmol / L, to obtain the selenium precursor solution.

[0063] 3) Under stirring conditions, the above selenium precursor solution was added to the cadmium precursor solution, 4 mL of hydrazine hydrate solution (80%) was added, and the mixture was heated under reflux at 100℃ for 5 h. After centrifugation with acetone solvent (7500 r / min, 5 min / time), deionized water was added to obtain CdSe quantum dot solution.

[0064] 4) Under nitrogen purging for 30 min and stirring, 1 mL (10 mol / L) zinc sulfate solution and 1 mL (10 mol / L) sodium sulfide solution were added dropwise to CdSe quantum dot solution at a rate of 1 mL / min. The solution was heated under constant temperature and reflux at 100℃ for 7 h to obtain the reaction solution.

[0065] 5) Add 1 mL of chloroform and 0.1 mL (0.12 mol / L) of 3-mercaptopropionic acid to 20 mg of the above reaction solution, heat at 60 °C for 1 h and dry to obtain 3-mercaptopropionic acid modified CdSe-ZnS green quantum dots with core-shell structure.

[0066] Example 4:

[0067] 1) Add 8.4g of cholesterol, 15.84g of lipoic acid, and 8.88g of 4-dimethylaminopyridine to 600ml of dichloromethane solvent, stir for 40min, and then add 38.4ml of N,N'-diisopropylcarbodiimide.

[0068] 2) After stirring the above solution for 6 days, rotary evaporation, column chromatography (eluent is a mixed solution of ethyl acetate and n-hexane with a volume ratio of 1:6), and rotary evaporation were performed to obtain thermotropic liquid crystal units with disulfide terminal groups.

[0069] Example 5:

[0070] 1) Add 8.4g of cholesterol, 15.84g of lipoic acid, and 8.88g of 4-dimethylaminopyridine to 450ml of dichloromethane solvent, stir for 40min, and then add 38.4ml of N,N'-diisopropylcarbodiimide.

[0071] 2) After stirring the above solution for 7 days, rotary evaporation, column chromatography (eluent is a mixed solution of ethyl acetate and n-hexane with a volume ratio of 1:6), and rotary evaporation were performed to obtain thermotropic liquid crystal units with disulfide terminal groups.

[0072] Example 6:

[0073] 6 mg of 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure and 20 mg of thermotropic liquid crystal units with disulfide terminal groups were added to 6 mL of dichloromethane solvent. After stirring for 3 days, the mixture was centrifuged with ethanol (6000 r / min, 5 min / time) to obtain the liquid crystal functionalized CdSe-ZnS green quantum dot material.

[0074] Example 7:

[0075] 4.5 mg of 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure and 15 mg of thermotropic liquid crystal ligand were added to 4.5 mL of dichloromethane solvent. After stirring for 3 days, the mixture was centrifuged with ethanol (6000 r / min, 5 min / time) to obtain the liquid crystal functionalized CdSe-ZnS green quantum dot material.

[0076] Comparative example:

[0077] 1) Add 8.4g of cholesterol, 15.84g of lipoic acid, and 2.22g of 4-dimethylaminopyridine to 450ml of dichloromethane solvent, stir for 40min, and then add 38.4ml of N,N'-diisopropylcarbodiimide.

[0078] 2) After stirring the above solution for another 6 days, rotary evaporation and column chromatography (using a 1:6 volume ratio of ethyl acetate and n-hexane as the eluent) were performed to obtain the target liquid crystal unit.

[0079] To further verify the superior effects of the technology of this invention, the inventors also conducted the following experiments:

[0080] Figure 1 The images show the XRD pattern, absorption spectrum, and emission spectrum of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure obtained in Example 1. For ease of comparison, [the images are shown in the original text]. Figure 1 The standard powder diffraction patterns of CdSe and ZnS crystals with a zincblende structure are listed (standard PDF card numbers: CdSe, 88-2346; ZnS, 77-2100). The XRD patterns of the CdSe-ZnS quantum dot powder samples are between those of CdSe and ZnS crystals, confirming the core-shell structure of the CdSe-ZnS quantum dots. The excitation and absorption spectra of the prepared CdSe-ZnS quantum dots were measured in a quartz cuvette. The figures show that the maximum fluorescence emission wavelength of the obtained 3-mercaptopropionic acid-modified CdSe-ZnS quantum dots with a core-shell structure is 540 nm, the ultraviolet absorption wavelength is 515 nm, and the "quantum efficiency" is 28%.

[0081] Figure 2The images show the POM and DSC diagrams of the thermotropic liquid crystal cell with disulfide terminal groups obtained in Example 1. The figures show that the liquid crystal cell exhibits a chiral phase array texture, and the liquid crystal phase temperature range is 78.2-98.1℃.

[0082] Figure 3 TEM and POM images of the liquid crystal functionalized CdSe-ZnS green quantum dot material obtained in Example 1. 1 HNMR and DSC images. The NMR results show that thermotropic liquid crystal units with disulfide terminal groups were successfully linked to CdSe-ZnS green quantum dots via chemical bonding. The size of the prepared green quantum dot / liquid crystal nanocomposite is approximately 4.9 nm. Under polarized light microscopy, the composite material exhibits birefringence and liquid crystal phase behavior, with a liquid crystal phase temperature range of 64.1–90.7 °C.

[0083] Figure 4 The figures show the absorption and laser spectra of the liquid crystal-functionalized CdSe-ZnS green quantum dot material obtained in Example 1. The figures indicate that, due to the increased volume of liquid crystal units on the quantum dot surface compared to 3-mercaptopropionic acid, the ultraviolet absorption wavelength of the prepared green liquid crystal quantum dots exhibits a redshift to 515 nm, and the maximum fluorescence emission wavelength is 547 nm (redshift), resulting in high-intensity green light visible to the naked eye. Because the liquid crystal units are strongly attached to the quantum dot surface via Zn-2S bonds, the number of trapped states on the surface is reduced (surface defects are passivated), and the quantum dots modified with liquid crystal functionalization exhibit birefringence, thereby enhancing fluorescence intensity. Therefore, the "quantum efficiency" of the green liquid crystal quantum dots is significantly increased to 56%.

[0084] Figure 5 The image shows the TLC plot of the target liquid crystal cell obtained in the comparative example. The plot indicates that the esterification reaction hardly occurred, and the product could not be effectively collected. Therefore, these reaction conditions are unfavorable for preparing thermotropic liquid crystal cells with disulfide terminal groups.

[0085] In summary, this invention innovatively constructs a quantum dot / liquid crystal nanocomposite material, effectively combining the inherent flexibility and tunability of liquid crystal with the controllable semiconductor fluorescence properties of quantum dots through chemical bonding. This results in a composite material possessing both luminescent and liquid crystal functions. The integration of liquid crystal and quantum dots is achieved through the interaction between different components, providing a new approach to improving the structure and performance of liquid crystal display panels. Furthermore, the preparation method of this invention is simple and easy to implement, effectively saving time and costs.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a quantum dot / liquid crystal nanocomposite material, characterized in that, 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure were prepared by hot injection method; thermotropic liquid crystal units with disulfide terminal groups were synthesized through esterification reaction between lipoic acid and cholesterol; then, some of the 3-mercaptopropionic acid ligands on the CdSe-ZnS green quantum dots were replaced with thermotropic liquid crystal units with disulfide terminal groups through chemical exchange reaction, thereby constructing liquid crystal functionalized CdSe-ZnS green quantum dot materials; The method for preparing the thermotropic liquid crystal unit with disulfide terminal groups includes the following steps: 1) Add cholesterol, lipoic acid, and 4-dimethylaminopyridine to dichloromethane solvent, stir, and then add N,N'-diisopropylcarbodiimide; 2) After further stirring of the above solution, rotary evaporation, column chromatography, and rotary evaporation were performed to obtain thermotropic liquid crystal units with disulfide terminal groups; The preparation method of the liquid crystal functionalized CdSe-ZnS green quantum dot material includes the following steps: 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure and thermotropic liquid crystal units with disulfide terminal groups were added to dichloromethane solvent and stirred. After centrifugation, the liquid crystal functionalized CdSe-ZnS green quantum dot material was obtained.

2. The method for preparing quantum dot / liquid crystal nanocomposite materials according to claim 1, characterized in that, The preparation method of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure includes the following steps: 1) Add cadmium sulfate solution and 3-mercaptopropionic acid solution to sodium hexametaphosphate solution, stir, and then add sodium hydroxide solution to obtain cadmium precursor solution; 2) Selenium dioxide was added to a nitric acid solution, stirred, and then diluted with deionized water to obtain a selenium precursor solution; 3) Under stirring conditions, the selenium precursor solution was added to the cadmium precursor solution, followed by the addition of hydrazine hydrate solution. After heating under reflux and centrifugation, deionized water was added to obtain the CdSe quantum dot solution. 4) Under nitrogen purging and stirring, zinc sulfate solution and sodium sulfide solution were added dropwise to CdSe quantum dot solution, and the mixture was heated under reflux to obtain the reaction solution; 5) Chloroform and 3-mercaptopropionic acid were added to the reaction solution, and after heating and drying, CdSe-ZnS green quantum dots with a core-shell structure modified by 3-mercaptopropionic acid were obtained.

3. The method for preparing quantum dot / liquid crystal nanocomposite materials according to claim 2, characterized in that, In step 1), the concentration of cadmium sulfate solution is 8-10 mmol / L, the mass fraction of 3-mercaptopropionic acid solution is 85-95%, the concentration of sodium hexametaphosphate solution is 12-16 mmol / L, and the concentration of sodium hydroxide solution is 2-5 mol / L. Sodium hydroxide solution is added until the pH value of the precursor solution reaches ~12. The volume ratio of cadmium sulfate solution, 3-mercaptopropionic acid solution and sodium hexametaphosphate solution is 1000:1~3:1000. In step 2), the mass fraction of the nitric acid solution is 65-75%, the volume ratio of the nitric acid solution to the selenium precursor solution is 1:3-5, and the selenium precursor solution is diluted to a selenium ion concentration of 0.05-0.15 mmol / L. In steps 1) and 2), the molar ratio of cadmium sulfate to selenium dioxide is 1~2:13; In step 3), the mass fraction of the hydrazine hydrate solution is 75-85%, the heating temperature is 90-110 °C, the reflux time is 4-6 h, the centrifugation speed is 6000-8000 r / min, and the volume ratio of the hydrazine hydrate solution to the CdSe quantum dot solution is 1-2:

25. In step 4), the nitrogen purging time is 20-40 min, the concentration of zinc sulfate solution is 8-12 mol / L, the concentration of sodium sulfide solution is 8-12 mol / L, the dropping rate is 1 mL / min, the volume ratio of zinc sulfate solution to sodium sulfide solution is 1:1-2, the heating temperature is 90-110 ℃, and the reflux time is 6-8 h. In step 5), the concentration of 3-mercaptopropionic acid is 0.08~0.12 mol / L, the volume ratio of chloroform to 3-mercaptopropionic acid is 10:1~2, the heating temperature is 50~70 ℃, and the heating time is 1~2 h.

4. The method for preparing quantum dot / liquid crystal nanocomposite materials according to claim 1, characterized in that, In step 1), the molar ratio of cholesterol, lipoic acid, 4-dimethylaminopyridine and N,N'-diisopropylcarbodiimide is 1~2:4:4:2, the volume ratio of dichloromethane solution and N,N'-diisopropylcarbodiimide is 20:1~2, and the stirring time is 30~50 min. The stirring time in step 2) is 5 to 7 days, and the eluent used in the column chromatography is a mixed solution of ethyl acetate and n-hexane with a volume ratio of 1:4 to 10.

5. The method for preparing quantum dot / liquid crystal nanocomposite materials according to claim 1, characterized in that, The mass ratio of the 3-mercaptopropionic acid-modified CdSe-ZnS green quantum dots with a core-shell structure to the thermotropic liquid crystal unit with disulfide terminal groups is 1~2:5, the volume of the dichloromethane solvent is 3~6 mL, the stirring time is 3~5 days, and the centrifugation speed is 6000~8000 r / min.

6. A quantum dot / liquid crystal nanocomposite material prepared by the method according to any one of claims 1-5, characterized in that, The quantum dot / liquid crystal nanocomposite material is a liquid crystal functionalized CdSe-ZnS green quantum dot material.

7. The application of a quantum dot / liquid crystal nanocomposite material prepared by the method of any one of claims 1-5 or the quantum dot / liquid crystal nanocomposite material as described in claim 6 in a liquid crystal display panel.

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