Microspheres containing ultrastable core-shell heterostructure nanocrystals and a preparation method thereof

Abstract

This application discloses a microsphere containing ultrastable core-shell heterostructure nanocrystals and its preparation method, belonging to the field of perovskite luminescence. It utilizes an S-Zn complex formed by octetranilol and zinc acetate dihydrate to passivate the Pb content on the surface of CsPbBr3 nanocrystals. 2+ Active site, Zn 2+ Doping improves lattice matching and enhances the fluorescence quantum yield of nanocrystals. The CsPbBr3 crystal phase on the nanocrystal surface undergoes a phase transition to Cs4PbBr6 under the synergistic effect of octylthiol and zinc acetate dihydrate, forming an ultrastable core-shell heterostructure. Composite microspheres of S-Zn@CsPbBr3 nanocrystals supported on polymethyl methacrylate (PMMA) were synthesized. The S-Zn@CsPbBr3@PMMA microspheres were constructed by precipitation polymerization of S-Zn@CsPbBr3 nanocrystals and methyl methacrylate prepolymer in n-hexane. The physical barrier effect of the PMMA matrix enhances the stability of the S-Zn@CsPbBr3 nanocrystals.

Description

Technical Field

[0001] This invention belongs to the field of perovskite luminescence technology, specifically relating to a microsphere containing ultrastable core-shell heterostructure nanocrystals and its preparation method. Background Technology

[0002] All-inorganic CsPbX3 (X = Cl, Br, or I) perovskite nanocrystals have attracted widespread attention due to their unique crystal structure and excellent photoluminescence properties, such as near 100% photoluminescence quantum yield, tunable bandgap, high color purity, and ease of preparation. Compared with organic-inorganic hybrid perovskites, they exhibit higher structural stability. However, these nanocrystals still face the challenge of emission spectrum broadening in practical applications. Spectral broadening in nanocrystals typically stems from two sources: first, enhanced exciton-phonon coupling caused by crystal defects or lattice disorder; and second, non-uniform particle size distribution resulting from aggregation or decomposition caused by unstable binding of original ligands on the surface during nanocrystal storage. These two points have been confirmed in numerous previous studies. As mentioned earlier, the key to achieving emission spectrum stability lies in simultaneously reducing electron-phonon coupling and obtaining a uniform particle size distribution. However, poor nanocrystal stability often leads to inconsistent crystal sizes, thus significantly broadening the spectrum. To address this, researchers have explored various strategies for controlling nanocrystals, such as using ligands to control crystal defects and reducing crystal defects through B-site doping. It is worth noting that B-site ion doping can directly affect the electronic structure and lattice matching degree of perovskite, thus significantly impacting the color purity of nanocrystals. Simultaneously, embedding perovskite nanocrystals into a polymer matrix to prepare nanocrystal-polymer composite microspheres is also a method to improve the optical performance of nanocrystals. Hydrophobic polymer microspheres can protect the embedded nanocrystals from corrosion by oxygen and moisture in the air, effectively improving the stability of the nanocrystals. However, the proposed methods for improving the stability of nanocrystals all have some problems, including the easy leakage of nanocrystals from the polymer microspheres, uneven distribution of nanocrystals within the microspheres, or non-uniform size and poor stability of the composite microspheres. On the other hand, due to the rapid nucleation rate of nanocrystals, they preferentially adhere to the surface of the microspheres, resulting in the polymer microspheres failing to provide adequate coating and protection for the nanocrystals. Furthermore, the microspheres synthesized in some methods are large in size (several micrometers) or have a wide size distribution, limiting their application in light-emitting devices.

[0003] Here, considering the crucial role of ligands and B-site ions in synergistically optimizing the optical properties of nanocrystals, a modification strategy is proposed to restrict Pb nucleation sites through ligand-ion complexes. The surface of pre-synthesized nanocrystals is modified using an S-Zn complex formed from octetranil and zinc acetate dihydrate. This complex effectively passivates the surface Pb through steric hindrance. 2+ Active sites effectively suppress surface defect states; in addition, Zn 2+Doping with CsPbBr3 facilitates better lattice matching within the nanocrystals, thereby reducing crystal defects and achieving a more uniform lattice distribution. This effectively suppresses exciton-phonon coupling and avoids spectral broadening. Importantly, the phase transition from CsPbBr3 to Cs4PbBr6, under the synergistic effect of octylthiol and zinc acetate dihydrate, forms a stable heterostructure, significantly improving the optical properties and stability of the nanocrystals. To enhance the interaction between the nanocrystals and polymer microspheres, carboxyl-modified polymethyl methacrylate (PMMA) microspheres that can covalently bond with the nanocrystals are used to coat them. A method for synthesizing polymer microspheres with core-loaded nanocrystals is proposed, in which PMMA microspheres are grown in situ with the nanocrystals as the core, and CsPbBr3 nanocrystals are coated into the interior of the microspheres. The advantages of this method are obvious: i) CsPbBr3 nanocrystals are distributed in PMMA microspheres; ii) the relatively strong coordination interaction between Pb ions on the surface of nanocrystals and carbonyl groups in PMMA ensures that CsPbBr3 nanocrystals are firmly embedded in the microspheres; iii) the reaction conditions are mild and will not damage the optical properties of nanocrystals, and the reaction temperature and time can be controlled, so the size and uniformity of the nanocrystal composite microspheres can be tunable. Summary of the Invention

[0004] Technical problems addressed: This application addresses the shortcomings of existing technologies by resolving issues such as enhanced exciton-phonon coupling caused by crystal defects or lattice disorder, uneven particle size distribution due to aggregation or decomposition caused by unstable binding of original ligands on the surface during nanocrystal storage, poor nanocrystal stability often leading to inconsistent crystal sizes, easy leakage of nanocrystals from polymer microspheres, uneven distribution of nanocrystals within microspheres, or uneven size and poor stability of composite microspheres, inability of polymer microspheres to form good coating protection for nanocrystals, and large or wide size distribution of synthesized microspheres, which limit their application in light-emitting devices. It also addresses the instability of the crystal structure and optical properties of perovskite nanocrystals, and the resulting low device lifetime and poor performance stability during light-emitting device development. This invention proposes a method that can improve the optical performance and stability of nanocrystals while solving application bottlenecks such as unstable optical performance of nanocrystals, weak bonding between nanocrystals and microspheres, and uneven size distribution of composite microspheres.

[0005] Purpose of the invention: This application provides a microsphere containing ultrastable core-shell heterostructure nanocrystals and its preparation method. The optical properties and stability of the nanocrystals are enhanced by constructing a heterostructure and densely coating it with polymers. This will help realize the commercial application of halide perovskite nanocrystals in the field of light-emitting devices, and achieve uniform, dense and stable coating of the nanocrystals, thus possessing excellent optical properties, luminescence stability and commercial application feasibility.

[0006] To achieve the above objectives, this application provides the following technical solution: A method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals specifically includes the following steps: Step 1, Preparation of CsPbBr3 nanocrystals: Dissolve 0.2–0.6 mmol PbBr2 and 0.2–0.6 mmol CsBr in 5–15 mL of water at a molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20–40 kHz for 1–2 hours to completely disperse PbBr2 and CsBr in the DMF, serving as a precursor solution. Take 0.5–1.5 mL of the precursor solution, add 0.05–0.15 mL of oleic acid and 0.03–0.07 mL of oleylamine to the 0.5–1.5 mL precursor solution, and shake until well mixed. Add 5–15 mL of toluene solution to the precursor solution at a rate of 20–60 mL / min, and stir on a magnetic stirrer at a speed of 1000–2000 rpm for 10–30 minutes to obtain a CsPbBr3 nanocrystal solution. The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 2-4 minutes, the supernatant is discarded, and 2-4 mL of n-hexane is added to the precipitate at the bottom of the centrifuge tube to disperse it fully, so as to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: Take 2-4 mL of perovskite nanocrystal solution dispersed in n-hexane solution according to the mass-volume ratio, then add 9-11 μL of octyl mercaptan solution and 1-9 mg of zinc acetate dihydrate powder, stir at 1500-3000 rpm for 23-25 ​​hours at room temperature, then centrifuge at 2000-4000 rpm for 2-4 minutes, retain the supernatant to obtain the S-Zn@CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Azobisisobutyronitrile (ABN) 0.01~0.04 g, methyl methacrylate (MMA) 0.3~0.5 mL, and methacryloxypropyl-terminated polydimethylsiloxane (MTP) 0.4~0.6 mL were added sequentially to the S-Zn@CsPbBr3 nanocrystal solution. The mixed solution was injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 10-30 minutes, the vial was placed in an oven at 30-80℃ for 1-3 hours. The reaction was then terminated by placing the vial in an ice-water bath. The suspension was washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 0.5-1.5 hours to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0007] Further, in the first step, 0.4 mmol PbBr2 and 0.4 mmol CsBr are dissolved in 10 mL of [a specific solution] by molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr were sonicated at 30 kHz for 1.5 hours to completely disperse PbBr2 and CsBr in the DMF, serving as a precursor solution. 1 mL of the precursor solution was taken, and 0.1 mL of oleic acid and 0.05 mL of oleylamine were added to the 1 mL precursor solution, and the mixture was shaken until homogeneous. The precursor solution was then injected into 10 mL of toluene solution at a rate of 40 mL / min, and stirred at 1500 rpm for 20 minutes on a magnetic stirrer to obtain a CsPbBr3 nanocrystal solution.

[0008] Further, in the second step, the CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 5000 rpm for 3 minutes, the supernatant is discarded, and the precipitate at the bottom of the centrifuge tube is added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane solution.

[0009] Further, in the third step, 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 6 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 2500 rpm for 24 hours at room temperature, and then centrifuged at 2500 rpm for 3 minutes to induce a phase transition and form core-shell heterostructure nanocrystals. The supernatant was retained to obtain the CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate, namely the S-Zn@CsPbBr3 nanocrystal solution.

[0010] Further, in the fourth step, 0.02 g of azobisisobutyronitrile (ABN), 0.3 mL of methyl methacrylate (MMA), and 0.5 mL of methacryloyloxypropyl-terminated polydimethylsiloxane (MTP) were sequentially added to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-volume ratio.

[0011] Furthermore, in the fourth step, the mixed solution is injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap, degassed with argon for 20 minutes, and then baked in an oven at 50°C for 2 hours.

[0012] Furthermore, in the fourth step, the reaction is terminated by placing the wide-mouth vial in an ice-water bath, and the suspension is washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0013] This application also discloses microspheres containing ultrastable core-shell heterostructure nanocrystals prepared by any of the above preparation methods.

[0014] Explanation of principle: A surface post-treatment strategy is adopted, utilizing the S-Zn complex formed by octylthiol and zinc acetate dihydrate to passivate the Pb on the surface of CsPbBr3 nanocrystals. 2+ The active site, through steric hindrance, effectively suppresses surface defect states; simultaneously, Zn 2+ Doping improves lattice matching, reduces crystal defects, and suppresses exciton-phonon coupling, thereby effectively enhancing the fluorescence quantum yield of nanocrystals. Furthermore, the CsPbBr3 crystal phase on the nanocrystal surface undergoes a phase transition to Cs4PbBr6 under the synergistic effect of octylthiol and zinc acetate dihydrate, forming an ultrastable core-shell heterostructure, which significantly enhances the optical stability of the nanocrystals. Further, a simple method was used to synthesize S-Zn@CsPbBr3 nanocrystals supported on polymethyl methacrylate (PMMA) composite microspheres. This method involves the precipitation of S-Zn@CsPbBr3 nanocrystals and PMMA prepolymer in hexane. The method for preparing high-performance nanocrystalline microspheres proposed in this invention is simple and efficient, which is conducive to the commercial application of perovskite nanocrystalline light-emitting devices. It effectively overcomes the problems of poor optical performance and stability of perovskite nanocrystalline materials, and provides an effective way to solve the key problems faced by perovskite nanocrystalline light-emitting devices.

[0015] Beneficial effects: This application provides a microsphere containing ultrastable core-shell heterostructure nanocrystals and its preparation method, which has the following advantages compared with the prior art: 1. This invention utilizes S-Zn formed from octylthiol and zinc acetate dihydrate to passivate the surface of pre-synthesized nanocrystals; this complex passivates the surface Pb through steric hindrance effect. 2+ Active sites effectively suppress surface defect states; simultaneously, Zn 2+ Doping improves lattice matching, reduces crystal defects, and forms an ultra-stable core-shell heterostructure, thereby effectively enhancing the optical performance and stability of nanocrystals; and by constructing S-Zn@CsPbBr3@PMMA microspheres through the physical barrier effect of the PMMA matrix, the luminescence performance stability of S-Zn@CsPbBr3 nanocrystals is further enhanced. 2. This invention modifies the surface of CsPbBr3 nanocrystals using an S-Zn complex formed from octylthiol and zinc acetate dihydrate, leveraging the steric hindrance effect of the complex to fully passivate the Pb on the nanocrystal surface. 2+ Active sites effectively suppress surface defect states; 3. This application Zn 2+ Doping improves lattice matching, reduces crystal defects, and suppresses exciton-phonon coupling, thereby effectively enhancing optical performance and stability. 4. Under the synergistic effect of octylthiol and zinc acetate dihydrate, CsPbBr3 undergoes a phase transition to Cs4PbBr6, forming ultrastable core-shell heterostructured nanocrystals. 5. The fluorescence quantum yield of S-Zn-modified CsPbBr3 nanocrystals was increased by 54% to 95%. Due to the passivation of defect states and the improvement of carrier recombination efficiency, the fluorescence lifetime increased from the initial 24.87 ns to 42.76 ns. In terms of stability, S-Zn-modified nanocrystals exhibited significantly improved environmental tolerance. S-Zn@CsPbBr3 nanocrystals could still maintain more than 85% of the initial fluorescence intensity T after 120 hours. 85 Its photochemical stability is comparable to that of the original nanocrystalline T 85 It increased by nearly 60 times in approximately 2 hours, demonstrating its superior resistance to degradation. 6. The S-Zn@CsPbBr3@PMMA microspheres synthesized using an in-situ preparation method achieved controllable modulation of particle size and narrow distribution. Furthermore, the physical barrier effect of the PMMA matrix further enhanced the stability of the S-Zn@CsPbBr3 nanocrystals. UV irradiation stability tests showed that the fluorescence intensity of the S-Zn@CsPbBr3 nanocrystal film could maintain 85% of its initial value after 190 hours of UV irradiation. In contrast, the UV irradiation time required for the S-Zn@CsPbBr3@PMMA microsphere film to reach the same degree of fluorescence intensity decay increased to 350 hours. This indicates that the PMMA polymer matrix significantly improved the performance stability of the nanocrystals. 7. The innovative strategy proposed in this invention, which combines ultrastable core-shell heterostructure nanocrystals with polymer microsphere encapsulation, is simple and efficient, enabling the low-cost, mass production technology of high-quality perovskite nanocrystals to take a solid step towards commercial application. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of S-Zn@CsPbBr3 nanocrystals and their PMMA composite microspheres in this application; Figure 2 The images show the absorption spectrum, fluorescence spectrum, fluorescence intensity statistics, and fluorescence peak position and full width at half maximum (FWHM) statistics of CsPbBr3 nanocrystals before and after modification with different concentrations of S-Zn in Examples 1 to 4 of this application. In the images, a is the absorption spectrum, b is the fluorescence spectrum, c is the fluorescence intensity statistics, and d is the fluorescence peak position and FWHM statistics. Figure 3 The images shown are transmission electron microscope (TEM) images of CsPbBr3 nanocrystals, S-Zn modified CsPbBr3 nanocrystals, particle size distributions of CsPbBr3 nanocrystals, and particle size distributions of S-Zn modified CsPbBr3 nanocrystals in Examples 1 and 3 of this application. Specifically, a is a TEM image of CsPbBr3 nanocrystals, b is a TEM image of S-Zn modified CsPbBr3 nanocrystals, c is a particle size distribution of CsPbBr3 nanocrystals, and d is a particle size distribution of S-Zn modified CsPbBr3 nanocrystals. Figure 4 This is an elemental distribution diagram of the S-Zn modified CsPbBr3 nanocrystals in Example 3 of this application; Figure 5 The images show the fluorescence and absorption spectra, fluorescence quantum yield, fluorescence lifetime, and UV-induced stability data of CsPbBr3 nanocrystals before and after S-Zn modification in Examples 1 and 3 of this application. In these images, a represents the fluorescence and absorption spectra and fluorescence quantum yield, b represents the fluorescence lifetime, and c represents the UV-induced stability data of the nanocrystals before and after S-Zn modification. Figure 6 The images show the XRD patterns of CsPbBr3 nanocrystals before and after S-Zn modification in Examples 1 and 3 of this application, as well as the Pb 4f, S 2p, and Zn 2p energy spectra of the CsPbBr3 nanocrystals before and after S-Zn modification. Specifically, a is the XRD pattern of CsPbBr3 nanocrystals before and after S-Zn modification, b is the Pb 4f energy spectrum, c is the S 2p energy spectrum, and d is the Zn 2p energy spectrum. Figure 7The images shown are SEM images, particle size distribution charts, and TEM images of S-Zn@CsPbBr3@PMMA microspheres in Example 3 of this application, where a is an SEM image, b is a particle size distribution chart, c is a TEM image of S-Zn@CsPbBr3@PMMA microspheres, and d is a local square image. Figure 8 This is a graph showing the UV irradiation stability data of the S-Zn@CsPbBr3 nanocrystalline film and the S-Zn@CsPbBr3@PMMA microsphere film in Example 3 of this application. Detailed Implementation

[0017] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments.

[0018] Example 1: A method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals, specifically including the following steps: Step 1, Preparation of CsPbBr3 nanocrystals: 0.4 mmol PbBr2 and 0.4 mmol CsBr were dissolved in 10 mL of water at a molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20-40 kHz for 1-2 hours to completely disperse PbBr2 and CsBr in the DMF, which serves as a precursor solution. Take 1 mL of the precursor solution and add 0.1 mL of oleic acid and 0.05 mL of oleylamine to the 1 mL of the precursor solution, and shake until well mixed. Add the precursor solution to 10 mL of toluene solution at a rate of 20-60 mL / min, and stir on a magnetic stirrer at a speed of 1000-2000 rpm for 10-30 minutes to obtain a CsPbBr3 nanocrystal solution. The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 3 minutes, the supernatant is discarded, and the precipitate at the bottom of the centrifuge tube is added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 1 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 1500~3000 rpm for 24 hours at room temperature, and then centrifuged at 2000~4000 rpm for 3 minutes. The supernatant was retained to obtain the S-Zn@CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Azobisisobutyronitrile (ABN) 0.01~0.04 g, methyl methacrylate (MMA) 0.3~0.5 mL, and methacryloxypropyl-terminated polydimethylsiloxane (MTP) 0.5 mL were sequentially added to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-to-volume ratio. The mixed solution was injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 20 minutes, the vial was placed in an oven at 50°C for 2 hours. Then, the reaction was terminated by placing the vial in an ice-water bath. The suspension was washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0019] Example 2, a method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals, specifically includes the following steps: Step 1, Preparation of CsPbBr3 nanocrystals: 0.4 mmol PbBr2 and 0.4 mmol CsBr were dissolved in 10 mL of water at a molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20-40 kHz for 1-2 hours to completely disperse PbBr2 and CsBr in the DMF, which serves as a precursor solution. Take 1 mL of the precursor solution and add 0.1 mL of oleic acid and 0.05 mL of oleylamine to the 1 mL of the precursor solution, and shake until well mixed. Add the precursor solution to 10 mL of toluene solution at a rate of 20-60 mL / min, and stir on a magnetic stirrer at a speed of 1000-2000 rpm for 10-30 minutes to obtain a CsPbBr3 nanocrystal solution. The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 3 minutes, the supernatant is discarded, and the precipitate at the bottom of the centrifuge tube is added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 3 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 1500~3000 rpm for 24 hours at room temperature, and then centrifuged at 2000~4000 rpm for 3 minutes. The supernatant was retained to obtain the S-Zn@CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Azobisisobutyronitrile (ABN) 0.01~0.04 g, methyl methacrylate (MMA) 0.3~0.5 mL, and methacryloxypropyl-terminated polydimethylsiloxane (MTP) 0.5 mL were sequentially added to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-to-volume ratio. The mixed solution was injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 20 minutes, the vial was placed in an oven at 50°C for 2 hours. Then, the reaction was terminated by placing the vial in an ice-water bath. The suspension was washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0020] Example 3, a method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals, specifically includes the following steps: Step 1, Preparation of CsPbBr3 nanocrystals: 0.4 mmol PbBr2 and 0.4 mmol CsBr were dissolved in 10 mL of [a solution / concentration] by molar volume. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20-40 kHz for 1-2 hours to completely disperse PbBr2 and CsBr in DMF, which serves as a precursor solution. Take 1 mL of the precursor solution and add 0.1 mL of oleic acid and 0.05 mL of oleylamine to the 1 mL of the precursor solution, and shake until well mixed. Add the precursor solution to 10 mL of toluene solution at a rate of 20-60 mL / min, and stir on a magnetic stirrer at a speed of 1000-2000 rpm for 10-30 minutes to obtain a CsPbBr3 nanocrystal solution. The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 3 minutes, the supernatant is discarded, and the precipitate at the bottom of the centrifuge tube is added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 6 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 1500~3000 rpm for 24 hours at room temperature, and then centrifuged at 2000~4000 rpm for 3 minutes. The supernatant was retained to obtain the S-Zn@CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Azobisisobutyronitrile (ABN) 0.01~0.04 g, methyl methacrylate (MMA) 0.3~0.5 mL, and methacryloxypropyl-terminated polydimethylsiloxane (MTP) 0.5 mL were sequentially added to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-to-volume ratio. The mixed solution was injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 20 minutes, the vial was placed in an oven at 50°C for 2 hours. Then, the reaction was terminated by placing the vial in an ice-water bath. The suspension was washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0021] Example 4: A method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals, specifically including the following steps: Step 1, Preparation of CsPbBr3 nanocrystals: 0.4 mmol PbBr2 and 0.4 mmol CsBr were dissolved in 10 mL of water at a molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20-40 kHz for 1-2 hours to completely disperse PbBr2 and CsBr in the DMF, which serves as a precursor solution. Take 1 mL of the precursor solution and add 0.1 mL of oleic acid and 0.05 mL of oleylamine to the 1 mL of the precursor solution, and shake until well mixed. Add the precursor solution to 10 mL of toluene solution at a rate of 20-60 mL / min, and stir on a magnetic stirrer at a speed of 1000-2000 rpm for 10-30 minutes to obtain a CsPbBr3 nanocrystal solution. The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 3 minutes, the supernatant is discarded, and the precipitate at the bottom of the centrifuge tube is added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 9 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 1500 rpm for 24 hours at room temperature, and then centrifuged at 2000~4000 rpm for 3 minutes. The supernatant was retained to obtain the CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate, namely the S-Zn@CsPbBr3 nanocrystal solution. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Azobisisobutyronitrile (ABN) 0.01~0.04 g, methyl methacrylate (MMA) 0.3~0.5 mL, and methacryloxypropyl-terminated polydimethylsiloxane (MTP) 0.5 mL were sequentially added to the S-Zn@CsPbBr3 nanocrystal solution. The mixed solution was injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 20 minutes, the vial was baked at 50°C for 2 hours. Then, the reaction was terminated by placing the vial in an ice-water bath. The suspension was washed three times with fresh n-hexane by centrifugation and redispersion, and then dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

[0022] The above description is only a preferred embodiment of the present invention. It should be noted that, under the premise of following the principles of the present invention, improved experimental schemes should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals, characterized in that, Specifically, the steps include the following: Step 1, Preparation of CsPbBr3 nanocrystals: Dissolve 0.2–0.6 mmol PbBr2 and 0.2–0.6 mmol CsBr in 5–15 mL of water by molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr are sonicated at a frequency of 20-40 kHz for 1-2 hours to completely disperse PbBr2 and CsBr in DMF, serving as a precursor solution. Take 0.5-1.5 mL of the precursor solution, add 0.05-0.15 mL of oleic acid and 0.03-0.07 mL of oleylamine to the 0.5-1.5 mL precursor solution, and shake until well mixed; add 5-15 mL of toluene solution to the precursor solution at a rate of 20-60 mL / min, and stir on a magnetic stirrer at a speed of 1000-2000 rpm for 10-30 minutes to obtain a CsPbBr3 nanocrystal solution; The second step is the purification of nanocrystals: CsPbBr3 nanocrystal solution is mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 1-2 hours until a precipitate appears to obtain a mixed solution; then the mixed solution is placed in a centrifuge and centrifuged at 4000-6000 rpm for 2-4 minutes, the supernatant is discarded, and 2-4 mL of n-hexane is added to the precipitate at the bottom of the centrifuge tube to disperse it fully, so as to obtain a perovskite nanocrystal solution dispersed in n-hexane solution; The third step is the preparation of S-Zn@CsPbBr3 nanocrystals: Take 2-4 mL of perovskite nanocrystal solution dispersed in n-hexane solution according to the mass-volume ratio, then add 9-11 μL of octyl mercaptan solution and 1-9 mg of zinc acetate dihydrate powder, stir at 1500-3000 rpm for 23-25 ​​hours at room temperature, then centrifuge at 2000-4000 rpm for 2-4 minutes, retain the supernatant to obtain the S-Zn@CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate. Step 4: Preparation of S-Zn@CsPbBr3@PMMA microspheres: Add 0.01~0.04 g of azobisisobutyronitrile (ABN), 0.3~0.5 mL of methyl methacrylate (MMA), and 0.4~0.6 mL of methacryloxypropyl-terminated polydimethylsiloxane (MTP) sequentially to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-to-volume ratio. Pour the mixed solution into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After argon degassing for 10-30 minutes, bake in an oven at 30-80℃ for 1-3 hours. Then, place the vial in an ice-water bath to terminate the reaction. Wash the suspension three times with fresh n-hexane by centrifugation and redispersion, and dry in a freeze dryer for 0.5-1.5 hours to obtain S-Zn@CsPbBr3@PMMA microspheres.

2. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that: In the first step, 0.4 mmol PbBr2 and 0.4 mmol CsBr are dissolved in 10 mL of water at a molar volume ratio. N , N In dimethylformamide (DMF), PbBr2 and CsBr were sonicated at a frequency of 30 kHz for 1.5 hours to completely disperse PbBr2 and CsBr in DMF, serving as a precursor solution. Take 1 mL of the precursor solution, add 0.1 mL of oleic acid and 0.05 mL of oleylamine to the 1 mL precursor solution, and shake until well mixed; add the precursor solution to 10 mL of toluene solution at a rate of 40 mL / min, and stir at 1500 rpm for 20 minutes on a magnetic stirrer to obtain CsPbBr3 nanocrystal solution.

3. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that, In the second step, the CsPbBr3 nanocrystal solution was mixed with methyl acetate at a volume ratio of 1:3 and allowed to stand for 2 hours until a precipitate appeared to obtain a mixed solution. Then, the mixed solution was placed in a centrifuge and centrifuged at 5000 rpm for 3 minutes. The supernatant was discarded, and the precipitate at the bottom of the centrifuge tube was added to 3 mL of n-hexane for thorough dispersion to obtain a perovskite nanocrystal solution dispersed in n-hexane.

4. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that, In the third step, 3 mL of perovskite nanocrystal solution dispersed in n-hexane solution was taken according to the mass-volume ratio, and then 10 μL of octyl mercaptan solution and 6 mg of zinc acetate dihydrate powder were added. The mixture was stirred at 2500 rpm for 24 hours at room temperature, and then centrifuged at 2500 rpm for 3 minutes to induce a phase transition and form core-shell heterostructure nanocrystals. The supernatant was retained to obtain the CsPbBr3 core-shell heterostructure nanocrystal solution co-modified by octyl mercaptan and zinc acetate dihydrate, namely S-Zn@CsPbBr3 nanocrystal solution.

5. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that, In the fourth step, 0.02 g of azobisisobutyronitrile (ABN), 0.3 mL of methyl methacrylate (MMA), and 0.5 mL of methacryloyloxypropyl-terminated polydimethylsiloxane (MTP) were added sequentially to the S-Zn@CsPbBr3 nanocrystal solution according to the mass-volume ratio.

6. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that, In the fourth step, the mixed solution is injected into a 10 mL wide-mouth vial with a rubber stopper and a central hole cap. After purging with argon gas for 20 minutes, it is placed in an oven at 50°C and baked for 2 hours.

7. The method for preparing microspheres containing ultrastable core-shell heterostructure nanocrystals according to claim 1, characterized in that, In the fourth step, the reaction is terminated by placing the wide-mouth vial in an ice-water bath. The suspension is then washed three times with fresh n-hexane by centrifugation and redispersion, and dried in a freeze dryer for 1 hour to obtain S-Zn@CsPbBr3@PMMA microspheres.

8. A microsphere containing ultrastable core-shell heterostructure nanocrystals prepared by any one of the preparation methods described in claims 1-7.

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