CsPbBr3 (at) MSNs (at) SiO2 composite material with high load rate as well as preparation method and application thereof

Abstract

The invention belongs to the field of full-inorganic perovskite photoelectric materials, and particularly relates to a CsPbBr3-coated MSNs-coated SiO2 composite material with high load rate and excellent stability, and a preparation method and application thereof. Comprising the following steps: firstly preparing uniformly dispersed mesoporous silica nanospheres, grafting amino and carboxyl, growing CsPbBr3 quantum dots in situ in holes of the nanospheres, and sealing the holes by SiO2 obtained by hydrolysis of a silicon source to obtain the CsPbBr3 (at) MSNs (at) SiO2 composite material with high load rate. The method is simple and good in repeatability, the nanospheres are subjected to amino and carboxyl grafting modification, perovskite quantum dots can be subjected to controlled nucleation growth in holes, the size is small enough, the perovskite quantum dots enter mesoporous sphere channels as much as possible, the loading rate is high, SiO2 generated through hydrolysis of a silicon source is used for sealing the holes of the mesoporous spheres, and stability is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of all-inorganic perovskite photoelectric materials, and more specifically, relates to a CsPbBr3@MSNs@SiO2 composite material with high loading rate and excellent stability, a preparation method and application thereof. Background Art

[0002] All-inorganic halide perovskites are a new type of optoelectronic material. Unlike traditional semiconductor nanocrystals, they possess not only the properties of traditional semiconductors but also the complex defect physics of ionic crystals. They also exhibit strong ionic interactions with surface ligands, resulting in a variety of interesting surface properties. The surface properties of CsPbBr3 quantum dots ultimately influence the self-assembly ability of the particles and the structure and properties of the material. Due to their unique crystal structure, high light absorption coefficient, high photoluminescence quantum yield, narrow emission linewidth, and tunable electronic properties, perovskite quantum dots exhibit excellent optoelectronic properties, attracting widespread attention in lighting, display applications, solar cells, sensors, photodetectors, lasers, and light-emitting diodes.

[0003] However, all-inorganic halide perovskites also face some challenges. When lead halide perovskites are exposed to light, heat, oxygen, and other stimuli, they will aggregate and decompose due to their ionic crystal structure, which can easily affect the integrity of the crystal structure and reduce the luminescence efficiency of the perovskite. Therefore, poor stability is still the main disadvantage limiting the practical application and commercialization of halide perovskites.

[0004] Encapsulation is an effective method for enhancing the stability of lead halide cesium perovskite quantum dots by specially treating them. The isolation effect created by loading perovskite quantum dots into other media can effectively prevent the perovskite from being eroded by polar solvents, atmospheric conditions, and high temperatures.

[0005] However, most of the research reported in the literature focuses on wet chemical methods, known as impregnation, to encapsulate perovskite nanocrystals into the pores of mesoporous silica. However, the open pores still make the perovskite susceptible to corrosion by polar solvents. Furthermore, existing research still has limitations in the loading rate of perovskite quantum dots onto mesoporous silica. Therefore, it is crucial to select a suitable loading method that allows the controlled nucleation and growth of perovskite quantum dots within the pores of the mesoporous matrix, ultimately increasing the loading rate. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for preparing a high-loading rate CsPbBr3@MSNs@SiO2 composite material, in which mesoporous silica nanospheres are modified by grafting amino and carboxyl groups so that perovskite quantum dots can be controlled to nucleate and grow in the pores of the mesoporous spheres, thereby synthesizing quantum dots with a sufficiently small size that can enter the pores of the mesoporous spheres as much as possible. The preparation method is simple and has good repeatability.

[0007] The second object of the present invention is to provide a high-loading rate CsPbBr3@MSNs@SiO2 composite material with strong stability and high quantum dot loading.

[0008] The third object of the present invention is to provide an application of a high-loading rate CsPbBr3@MSNs@SiO2 composite material.

[0009] The solution adopted to achieve one of the objectives of the present invention is: a method for preparing a high-loading rate CsPbBr3@MSNs@SiO2 composite material, comprising the following steps: preparing uniformly dispersed mesoporous silica nanospheres; Grafting amino and carboxyl groups onto mesoporous silica nanospheres; CsPbBr3 quantum dots were in situ grown in the pores of mesoporous silica nanospheres grafted with amino and carboxyl groups to obtain CsPbBr3@MSNs composite materials. The pores of the mesoporous silica nanospheres are sealed by SiO2 obtained by hydrolysis of a silicon source, and a secondary coating is performed to finally obtain the high-loading rate CsPbBr3@MSNs@SiO2 composite material.

[0010] Preferably, the method specifically includes the following steps: (1) Prepare uniformly dispersed mesoporous silica nanospheres; (2) uniformly dispersing the mesoporous silica nanospheres prepared in step (1) in a dispersing solvent, adding an amino modifier and stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain amino-grafted mesoporous silica nanospheres; (3) uniformly dispersing the amino-grafted mesoporous silica nanospheres obtained in step (2) in a dispersing solvent, and gradually adding a dispersing solvent containing a carboxyl modifier, stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain mesoporous silica nanospheres grafted with amino and carboxyl groups; (4) uniformly mixing the cesium source, the lead source, the mesoporous silica nanospheres grafted with amino and carboxyl groups obtained in step (3), oleic acid, oleylamine, and octadecene, and removing excess water and oxygen; (5) Heating under an inert atmosphere, injecting a bromine source at a certain temperature to react, and then quenching the reaction in an ice-water bath; (6) The product obtained in step (5) is centrifuged and washed to obtain a CsPbBr3@MSNs composite material; (7) The CsPbBr3@MSNs composite material obtained in step (6) is dispersed in a non-polar solvent, a silicon source is added dropwise and stirred to fully hydrolyze it, and the CsPbBr3@MSNs@SiO2 composite material is obtained after centrifugation and washing.

[0011] The preparation method of the present invention first adopts independent cesium sources, lead sources and bromine sources, so that the component ratio of cations and bromide ions in perovskite quantum dots can be precisely controlled.

[0012] Compared with monodisperse CsPbBr3 quantum dots, perovskite quantum dots can be controllably grown in the pores of mesoporous silica and encapsulated. Not only does the stability of perovskite quantum dots greatly improve, but the average size of quantum dots is also significantly reduced, the fluorescence spectrum shows a significant blue shift, the fluorescence lifetime is shortened, and the photoluminescence quantum efficiency is improved. These key features can be used in sensors and various smart display devices and lighting equipment.

[0013] Preferably, in step (1), the preparation method of the mesoporous silica nanospheres is as follows: cetyltrimethylammonium p-toluenesulfonate, triethanolamine and water are mixed in a ratio of 0.96-0.98 g:0.16 g:50-60 ml, and stirred at 80-100 ° C at 500-1000 rpm until dissolved and mixed uniformly to obtain a transparent precursor solution; tetraethyl orthosilicate is added to the precursor solution, and stirred continuously at 80-100 ° C at a speed of 500-1000 rpm for 2-4 hours, wherein the mixing ratio of tetraethyl orthosilicate to the precursor solution is 8 ml:50-80 ml; the obtained reaction solution is collected, centrifuged, washed, dried, and then calcined at 550 ° C to obtain the mesoporous silica nanospheres.

[0014] Preferably, in step (2), the amino modifier is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the dispersing solvent is a polar solvent.

[0015] Specific dispersing solvents include toluene, n-hexane, cyclohexane, and the like.

[0016] Preferably, in step (3), the carboxyl modifier is at least one of succinic anhydride, benzoic acid, and chloroacetic acid, and the dispersing solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and acetone.

[0017] Preferably, in step (4), the cesium source is Cs2CO3, CsNO3, or CH3COOCs, the lead source is at least one of Pb(OAc)2, Pb(NO3)2, and hydrates thereof, and the molar ratio of cesium to lead is 1:1-1.5.

[0018] Preferably, in step (5), the temperature is raised to 130-150° C. and a bromine source is added to carry out the reaction. The reaction time is within 20 seconds. The bromine source is at least one of benzoyl bromide and vinyl bromide. The molar ratio of the bromine source to the cesium source is 1:3-7.

[0019] Preferably, in step (7), the non-polar solvent is at least one of n-hexane, cyclohexane, and toluene, and the silicon source is at least one of tetraethyl orthosilicate, tetramethoxysilane, and phenyltriethoxysilane.

[0020] The solution adopted to achieve the second purpose of the present invention is: a high-loading rate CsPbBr3@MSNs@SiO2 composite material is prepared by the preparation method, and the mass ratio of CsPbBr3 to MSNs is 1:0.6-1.

[0021] The solution adopted to achieve the third purpose of the present invention is: an application of a high-loading rate CsPbBr3@MSNs@SiO2 composite material prepared by the preparation method, and applying the high-loading rate CsPbBr3@MSNs@SiO2 composite material to the fields of lighting, display applications, solar cells, sensors, photodetectors, lasers and light-emitting diodes. The beneficial effects of the present invention are as follows: The preparation method of the present invention is simple and has good repeatability. The mesoporous silica nanospheres are modified by grafting amino and carboxyl groups so that the perovskite quantum dots can be controlled to nucleate and grow in the pores of the mesoporous spheres, thereby synthesizing a sufficiently small size, increasing the number of quantum dots that enter the pores of the mesoporous spheres as much as possible, and making the loading rate higher. The SiO2 generated by the hydrolysis of the silicon source is used to seal the pores of the mesoporous spheres, thereby enhancing the stability. The composite material has a reduced fluorescence lifetime due to its accelerated carrier migration rate.

[0022] The high-loading-rate CsPbBr3@MSNs@SiO2 composite material prepared by the preparation method of the present invention has a loading rate of up to 28%, which is 2.3 times the loading rate before modification.

[0023] The high-loading rate CsPbBr3@MSNs@SiO2 composite material prepared by the preparation method of the present invention can be used in various intelligent display devices and lighting devices, has a high loading rate and excellent stability, and has a reduced fluorescence lifetime. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1is the Fourier transform infrared spectra of nMSNs and MSNs in Comparative Example 1 and Example 1; Figure 2 TEM images of MSNs, CsPbBr3@MSNs, and CsPbBr3@MSNs@SiO2 prepared in Example 1; Figure 3 The fluorescence spectra of CsPbBr3, CsPbBr3@MSNs, and CsPbBr3@MSNs@SiO2 at room temperature with a feed mass ratio of 1:1 in Example 1 are shown; Figure 4 PL diagrams of CsPbBr3 and CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:1 in Example 1, where RT refers to room temperature; Figure 5 The fluorescence lifetime curves of CsPbBr3 in Example 1 and CsPbBr3, CsPbBr3@MSNs, and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:1 at room temperature are shown; Figure 6 The nitrogen isothermal adsorption-desorption curves and pore size distribution diagrams of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a mass ratio of MSNs to feed of 1:1 in Example 1 are shown; Figure 7 is the relative PL intensity of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a CsPbBr3 to MSNs mass ratio of 1:1 under continuous 365 nm laser irradiation in Example 1; Figure 8 TEM and corresponding elemental mapping of CsPbBr3@MSNs with a feed mass ratio of 1:1 in Comparative Example 1; Figure 9 Schematic diagram of the luminescence of the anti-counterfeiting QR code made of the CsPbBr3@MSNs@SiO2 composite material prepared in Example 1 after being stored for different periods of time; Figure 10 are SEM images of MSNs, CsPbBr3@MSNs, and CsPbBr3@MSNs@SiO2 in Example 1; Figure 11 The fluorescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature with a feed mass ratio of 1:0.8 in Example 2 are shown in FIG. Figure 12 TEM images of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.8 in Example 2; Figure 13 The fluorescence lifetime curves of CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.8 and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:1 at room temperature in Example 2 are shown; Figure 14 The fluorescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature with a feed mass ratio of 1:0.6 in Example 3 are shown; Figure 15 TEM images of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.6 in Example 3; Figure 16 The fluorescence spectrum of CsPbBr3@nMSNs at room temperature corresponding to the CsPbBr3 and nMSNs feeding mass ratio of 1:1 in Comparative Example 1 is 526 nm; Figure 17 TEM and corresponding elemental mapping of CsPbBr3@nMSNs with a feed mass ratio of 1:1 in Comparative Example 1; Figure 18 is the fluorescence spectrum of CsPbBr3@MSNs prepared in Comparative Example 2; Figure 19 TEM images of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.3 in Comparative Example 3; Figure 20 The fluorescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature with a feed mass ratio of 1:0.3 in Comparative Example 3 are shown; Figure 21 Normalized intensity photoluminescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 composites prepared according to different mass ratios of CsPbBr3 to MSNs (1:1, 1:0.8, 1:0.6, 1:0.3); Figure 22 These are the actual pictures of CsPbBr3@MSNs@SiO2 prepared according to the mass ratio of CsPbBr3:MSNs of 1:1, 1:0.8, 1:0.6 and 1:0.3 under natural light (left) and ultraviolet light (right). DETAILED DESCRIPTION

[0025] The present invention is further explained below through specific examples.

[0026] In the present invention, nMSNs refers to mesoporous silica nanospheres grafted with only amino groups but not carboxyl groups; MSNs refers to mesoporous silica nanospheres grafted with both amino groups and carboxyl groups.

[0027] The present invention specifically includes the following steps: (1) Preparation of uniformly dispersed mesoporous silica nanospheres; (2) uniformly dispersing the mesoporous silica nanospheres prepared in step (1) in a dispersing solvent, adding an amino modifier and stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain amino-grafted mesoporous silica nanospheres; (3) uniformly dispersing the amino-grafted mesoporous silica nanospheres obtained in step (2) in a dispersing solvent, and gradually adding a dispersing solvent containing a carboxyl modifier, stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain mesoporous silica nanospheres grafted with amino and carboxyl groups; (4) uniformly mixing the cesium source, the lead source, the mesoporous silica nanospheres grafted with amino and carboxyl groups obtained in step (3), oleic acid, oleylamine, and octadecene, and removing excess water and oxygen; (5) Heating under an inert atmosphere, injecting a bromine source at a certain temperature to react, and then quenching the reaction in an ice-water bath; (6) The product obtained in step (5) is centrifuged and washed to obtain a CsPbBr3@MSNs composite material; (7) The CsPbBr3@MSNs composite material obtained in step (6) is dispersed in a non-polar solvent, a silicon source is added dropwise and stirred to fully hydrolyze it, and the CsPbBr3@MSNs@SiO2 composite material is obtained after centrifugation and washing.

[0028] In step (1), the preparation method of the mesoporous silica nanospheres is as follows: hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine and water are mixed in a ratio of 0.96-0.98g:0.16g:50-60ml, and stirred at 80-100°C at 500-1000 rpm until dissolved and mixed uniformly to obtain a transparent precursor solution; tetraethyl orthosilicate is added to the precursor solution, and stirred continuously at 80-100°C at a speed of 500-1000 rpm for 2-4h, wherein the mixing ratio of tetraethyl orthosilicate to the precursor solution is 8ml:50-80ml; the obtained reaction solution is collected, centrifuged, washed, dried, and then calcined at 550°C to obtain the mesoporous silica nanospheres.

[0029] In step (2), the amino modifier is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the dispersing solvent is a polar solvent.

[0030] Specific dispersing solvents include toluene, n-hexane, cyclohexane, and the like.

[0031] In step (3), the carboxyl modifier is at least one of succinic anhydride, benzoic acid, and chloroacetic acid, and the dispersing solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and acetone.

[0032] In step (4), the cesium source is Cs2CO3, CsNO3, or CH3COOCs, the lead source is at least one of Pb(OAc)2, Pb(NO3)2, and hydrates thereof, and the molar ratio of cesium to lead is 1:1-1.5.

[0033] In the step (5), the temperature is raised to 130-150° C. and a bromine source is added to carry out the reaction. The reaction time is within 20 seconds. The bromine source is at least one of benzoyl bromide and vinyl bromide. The molar ratio of the bromine source to the cesium source is 1:3-7.

[0034] In the step (7), the non-polar solvent is at least one of n-hexane, cyclohexane, and toluene, and the silicon source is at least one of tetraethyl orthosilicate, tetramethoxysilane, and phenyltriethoxysilane.

[0035] The feed mass ratio of CsPbBr3 to MSNs is 1:0.6-1.

[0036] Example 1 The preparation method of a CsPbBr3@MSNs@SiO2 composite material with a high loading and good stability and a feed mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: (1) Preparation of mesoporous silica nanospheres grafted with amino and carboxyl groups: Weigh 0.96 g of hexadecyltrimethylammonium p-toluenesulfonate and 0.16 g of triethanolamine, and place them with 50 ml of deionized water in a three-necked flask, wherein two of the three-necked flask's ports are sealed, and the other port is connected to a condenser to introduce nitrogen. Stir the mixture at a stirring speed of 1000 rpm for 1 h in an 80°C oil bath to obtain a transparent precursor solution; quickly inject 8 ml of tetraethyl orthosilicate into the precursor solution, maintain the oil bath temperature at 80°C, and stir the mixture at a speed of 1000 rpm for 2 h. Collect the obtained reaction solution, centrifuge it at 10,000 rpm for 10 minutes, wash it three times with water and ethanol respectively, dry it at 60°C, grind it, sieve it, place it in a ceramic boat, and calcine it in a muffle furnace at 550°C for 6 h to obtain uniformly dispersed mesoporous silica nanospheres; The mesoporous silica nanospheres prepared above were evenly dispersed in 10 ml of toluene, and 0.4 ml of 3-aminopropyltriethoxysilane was added and stirred at 500 rpm overnight to obtain amino-grafted mesoporous silica spheres. The amino-grafted mesoporous silica spheres were then dried at 60 ° C overnight, ground and sieved, and 1 g of amino-grafted mesoporous silica spheres was weighed and evenly dispersed in 15 ml of N, N-dimethylformamide to obtain an amino-grafted mesoporous silica sphere solution. 1 g of the amino-grafted mesoporous silica spheres was then weighed and evenly dispersed in 15 ml of N, N-dimethylformamide to obtain an amino-grafted mesoporous silica sphere solution. .15g of succinic anhydride was dissolved in about 10ml of N,N-dimethylformamide, and the succinic anhydride solution was added dropwise into the solution of mesoporous silica spheres grafted with amino groups. The mixture was stirred at 200 rpm overnight to allow the succinic anhydride to be fully hydrolyzed. The mixture was then centrifuged at 10,000 rpm for 10 minutes and washed twice with ethanol. Finally, the mixture was dried in an oven at 60°C overnight, ground and sieved to obtain uniformly dispersed mesoporous silica nanospheres (MSNs) grafted with amino groups and carboxyl groups.

[0037] (2) Synthesis of CsPbBr3@MSNs solution: Weigh 0.016g of cesium carbonate (Cs2CO3), 0.076g of lead acetate trihydrate (Pb(COO)2·3H2O), and 0.058g of mesoporous silica nanospheres (MSNs) grafted with amino and carboxyl groups and place them in the same three-necked flask. Connect the middle opening of the flask to a condenser, and connect the upper end of the condenser to a double-row tube system. Add 0.3ml of oleic acid, 1ml of oleylamine, and 5ml of octadecene from the side opening of the flask. After placing a rotor, seal the two side openings. Vacuum dry for 3h to remove air, maintain a vacuum degree of 90℃, and stir overnight to remove moisture. Turn on the vacuum pump again and vacuum dry for 1h. Then, under a nitrogen atmosphere, heat to 130℃ and quickly inject 0.08ml of benzoyl bromide into the three-necked flask. After 1-2s, cool to room temperature in an ice-water bath.

[0038] (3) Centrifugal washing treatment: n-hexane was added to the reaction solution described in step (2) above, and the mixture was centrifuged at 10,000 rpm for 10 minutes. The supernatant was removed, and 5 ml of n-hexane was added to evenly disperse the precipitate. The mixture was centrifuged again at 10,000 rpm for 10 minutes, and the supernatant was removed to obtain CsPbBr3@MSNs precipitate.

[0039] (4) Synthesis of CsPbBr3@MSNs@SiO2 solution: The CsPbBr3@MSNs precipitate described in step (3) above was placed in a glass scintillation counting bottle. 15 ml of n-hexane and 0.04 ml of tetraethyl orthosilicate were measured and added to the glass scintillation counting bottle using a pipette. A rotor was added and stirred at a stirring speed of 200 rpm overnight.

[0040] (5) Centrifugation: The stirred solution described in step (4) was transferred to a centrifuge tube, centrifuged at 10,000 rpm for 10 minutes, and the supernatant was removed to obtain a CsPbBr3@MSNs@SiO2 composite material.

[0041] Figure 1 Figure 4 is the Fourier transform infrared spectrum of nMSNs and MSNs. It can be seen from the figure that compared with the infrared spectrum of nMSNs, there are obvious amino and carboxyl absorption peaks in the infrared spectrum of MSNs, proving that amino and carboxyl groups have been grafted on MSNs.

[0042] Figure 2 These are the TEM images of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a CsPbBr3 to MSNs feed mass ratio of 1:1. By comparison, it can be seen that the three are all dispersed spherical, with a size of about 72.5nm, uniform size, good dispersion, high loading rate, and complete secondary coating.

[0043] Figure 3 These are the fluorescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature with a CsPbBr3:MSNs feed mass ratio of 1:1. By comparison, it can be seen that the luminescence position of the composite material after loading undergoes a blue shift, with an emission wavelength of 480nm, emitting blue light.

[0044] Figure 4 The figure shows the temperature-dependent PL (fluorescence spectrum) of CsPbBr3, CsPbBr3@MSNs with a feed mass ratio of 1:1, and CsPbBr3@MSNs@SiO2. Compared with pure CsPbBr3, the thermal stability of the composite material is significantly improved. Among them, CsPbBr3@MSNs has not yet quenched fluorescence at 240°C, and CsPbBr3@MSNs@SiO2 has not undergone fluorescence quenching at 300°C.

[0045] Figure 5 Figure 3 is the fluorescence lifetime curve of CsPbBr3, CsPbBr3@MSNs with a feed mass ratio of 1:1, and CsPbBr3@MSNs@SiO2 at room temperature. Through fitting and calculation, the average fluorescence lifetime of CsPbBr3@MSNs@SiO2 is shorter than that of CsPbBr3, and the decay rate becomes faster.

[0046] Figure 6 These are the nitrogen isothermal adsorption-desorption curves and pore size distribution diagrams of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a CsPbBr3 to MSNs feed mass ratio of 1:1. By comparison, it can be seen that there is no obvious pore size distribution after loading, indicating the disappearance of the mesoporous structure.

[0047] Figure 7The relative PL intensity of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a CsPbBr3 to MSNs mass ratio of 1:1 under continuous irradiation of a 365nm laser. It can be seen from the figure that the CsPbBr3@MSNs@SiO2 material after secondary coating still retains a high luminescence intensity after continuous ultraviolet irradiation for 23 hours, and has strong photostability.

[0048] Figure 8 This is the TEM of CsPbBr3@MSNs with a feed mass ratio of 1:1 and the corresponding elemental mapping. The size is about 72.5nm, the size is uniform, the dispersion is good, and the loading is relatively good. Figure 17 Better, with more highlighted Cs, Pb, and Br elements.

[0049] Figure 9 This is an anti-counterfeiting QR code made of CsPbBr3@MSNs@SiO2 composite material. As can be seen from the figure, it still has good luminescence intensity after being stored for 30 days.

[0050] Figure 10 are the SEM images of MSNs, CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2. The mesoporous structures of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 disappear.

[0051] Table 1 shows the PLQY table of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a CsPbBr3 to MSNs feed mass ratio of 1:1.

[0052] Table 1

[0053] It can be seen from the data in Table 1 that after loading and coating, the PLQY of the obtained product increased significantly.

[0054] Table 2 shows the average specific surface area and pore volume data of nMSNs, MSNs, CsPbBr3@nMSNs, CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:1.

[0055] Table 2

[0056] From the data in Table 2, it can be seen that MSNs can significantly improve its loading capacity for perovskite quantum dots.

[0057] Example 2 A method for preparing a CsPbBr3@MSNs@SiO2 composite material with a high loading and good stability and a mass ratio of CsPbBr3 to MSNs of 1:0.8 is as follows: The preparation steps of MSNs are the same as those in Example 1.

[0058] Synthesis of CsPbBr3@MSNs solution: Only the mass of MSNs was changed. 0.0464 g of MSNs was weighed and the prepared sample was dispersed in n-hexane. The other steps were the same as in Example 1.

[0059] Figure 11 This is the fluorescence spectrum of CsPbBr3@MSNs and CsPbBr32MSNs@SiO2 at room temperature with a feed mass ratio of 1:0.8. After loading, the luminescence position of the composite material shifts to the blue, and the emission wavelength is 496nm, emitting bluish-cyan light.

[0060] Figure 12 This is the TEM image of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.8. The size is about 72.5nm, the size is uniform, the dispersion is good, and the loading capacity is high.

[0061] Figure 13 Figure 2 shows the fluorescence lifetime curves of CsPbBr3@MSNs with a feed mass ratio of 1:0.8 and 1:1 at room temperature. Fitting and calculation show that the average fluorescence lifetime of the 1:1 sample is shorter than that of the 1:0.8 sample, indicating a faster decay rate.

[0062] Example 3 A method for preparing a CsPbBr3@MSNs@SiO2 composite material with a high loading and good stability and a mass ratio of CsPbBr3 to MSNs of 1:0.6 is as follows: The preparation steps of MSNs are the same as those in Example 1.

[0063] Synthesis of CsPbBr3@MSNs solution: Only the mass of MSNs was changed, and 0.0348 g of MSNs was weighed. The other steps were consistent with Example 1.

[0064] Figure 14 This is the fluorescence spectrum of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature with a feed mass ratio of 1:0.6. After loading, the luminescence position of the composite material shifts to the blue, and the emission wavelength is 505nm, emitting cyan light.

[0065] Figure 15This is the TEM image of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.6. The size is about 72.5nm, the size is uniform, the dispersion is good, and the loading condition is good.

[0066] Table 3 shows the inductively coupled plasma analysis of CsPbBr3@MSNs and CsPbBr3@nMSNs with a feed mass ratio of 1:1, and CsPbBr3@MSNs with a feed mass ratio of 1:0.8 and 1:0.6, which qualitatively describes the loading amount.

[0067] Table 3

[0068] From the data in Table 3, it can be seen that the sample with a ratio of 1:0.8 has the highest loading capacity. However, combined with the TEM image of the sample with a ratio of 1:0.6-1, the perovskite quantum dots formed by the samples with a ratio of 1:0.8 and 1:0.6 are larger in size and many are distributed on the surface of MSNs, while the perovskite quantum dots of the sample with a ratio of 1:1 are smaller, have a better loading effect, and the loading capacity is significantly improved.

[0069] Example 4 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the reaction time after hot injection of the bromine source in step (5) was extended to 12 s, and the other steps remained the same as in Example 1.

[0070] The corresponding scanning images and transmission images of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, with an emission wavelength of 482 nm and blue light.

[0071] Example 5 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the carboxyl modifier in step (3) was changed to benzoic acid or chloroacetic acid, and the other steps were consistent with Example 1. The Fourier transform infrared transform spectrum of the MSNs after carboxyl grafting showed obvious amino and carboxyl absorption peaks, proving that both amino and carboxyl groups had been grafted onto the MSNs.

[0072] The corresponding scanning images, transmission images and other experimental results of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, with an emission wavelength of 480±5nm and blue light.

[0073] Example 6 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine and deionized water in step (1) were mixed in a ratio of 0.98 g:0.16 g:60 ml, and the stirring speed was 500 rpm or 750 rpm. The other steps were consistent with Example 1.

[0074] The TEM images of MSNs are similar to those in Example 1. Figure 2 Similarly, the average pore size and average comparison area are basically unchanged compared with Example 1. The corresponding scanning images, transmission images and other experimental results of CsPbBr3@MSNs@SiO2 at room temperature are similar to those of Example 1, with an emission wavelength of 480nm and blue light.

[0075] Example 7 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the reaction time after hot injection of the bromine source in step (5) was extended to 15 s, and the other steps were consistent with Example 1.

[0076] The corresponding scanning images and transmission images of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, with an emission wavelength of 485 nm and blue light.

[0077] Example 8 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the reaction time after hot injection of the bromine source in step (5) was extended to 20 s, and the other steps remained the same as in Example 1.

[0078] The corresponding scanning images and transmission images of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, with an emission wavelength of 490 nm and blue-cyan light.

[0079] Example 9 The preparation method of CsPbBr3@MSNs@SiO2 composite material with a mass ratio of CsPbBr3 to MSNs of 1:1 is as follows: Only the heating temperature in step (5) was changed to 150° C., and the other steps remained the same as in Example 1.

[0080] The corresponding scanning images and transmission images of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, with an emission wavelength of 490 nm and blue-cyan light.

[0081] Comparative Example 1 The difference between this comparative example and Example 1 is that only amino groups are grafted onto the mesoporous silica nanospheres without carboxyl groups, and the other steps are consistent with Example 1. A CsPbBr3@nMSNs@SiO2 composite material was prepared with a feed mass ratio of CsPbBr3 to nMSNs of 1:1.

[0082] Figure 16 The fluorescence spectra of CsPbBr3@nMSNs and CsPbBr3@nMSNs@SiO2 at room temperature with a feed mass ratio of 1:1 are shown. The emission wavelength is 526nm, which is green light with no blue shift. This indicates that after the carboxyl groups are grafted, the carboxyl groups control the nucleation of more perovskite quantum dots, reducing the average size of the prepared perovskite quantum dots. When the size reaches the Bohr radius, a quantum confinement effect occurs. At this time, the emission wavelength depends not only on the structure of the material, but also on the size and shape. Therefore, after the carboxyl groups are grafted, the emission wavelength of the perovskite quantum dots blue-shifts. In the sample without the carboxyl groups, the perovskite quantum dots failed to controllably nucleate, and the emission wavelength of the prepared sample was close to that of the pure perovskite quantum dots.

[0083] Figure 17 The TEM and corresponding elemental mapping of CsPbBr3@nMSNs with a feed mass ratio of 1:1 are shown. The size is about 72.5nm, with uniform size and good dispersion. Figure 8 Compared with Figure 8 shown.

[0084] Comparative Example 2 The difference between this comparative example and Example 1 is that only the heating temperature in step (5) is increased to 180° C., and the other steps are consistent with Example 1.

[0085] The corresponding scanning images and transmission images of CsPbBr3@MSNs@SiO2 at room temperature are similar to those in Example 1, and the fluorescence spectrum emission wavelength is 513nm, emitting green light.

[0086] Figure 18 This is the fluorescence spectrum of CsPbBr3@MSNs prepared in Comparative Example 2. It can be seen from the figure that the emission wavelength is 513nm, emitting green light, indicating that the temperature is too high, which will promote the growth of quantum dots, the size of the formed quantum dots will become larger, and the emission wavelength will red-shift.

[0087] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of CsPbBr3 to MSNs is changed to 1:0.3, and the remaining steps are the same as those in Example 1.

[0088] Figure 19TEM images of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 with a feed mass ratio of 1:0.3 show that the perovskite tends to form nanorods due to the low content of mesoporous spheres. This is due to the long precursor stirring time and the low carboxyl content, which is insufficient to control the formation of more perovskite nuclei, and the lattice tends to reorganize and form nanorods.

[0089] Figure 20 Figure 2 shows the fluorescence spectra of CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 at room temperature, with a feed ratio of 1:0.3. The loaded composite exhibits a red-shifted emission wavelength of 519 nm. Due to the low MSN content in the 1:0.3 sample, there are not enough carboxyl groups to control nucleation, causing the perovskite to form nanorods, resulting in a red-shifted emission position.

[0090] Figure 21 The following are the photoluminescence spectra of various samples. CsPbBr3@MSNs and CsPbBr3@MSNs@SiO2 composites were prepared at different CsPbBr3:MSNs mass ratios (1:1, 1:0.8, 1:0.6, and 1:0.3). As can be seen from the figure, the emission wavelength gradually shifts to the blue with increasing MSN content. This indicates that after carboxyl grafting, the carboxyl groups control the nucleation of more perovskite quantum dots, reducing the average size of the prepared perovskite quantum dots. When the size reaches the Bohr radius, quantum confinement occurs. At this point, the emission wavelength depends not only on the material structure but also on its size and shape. Therefore, the carboxyl grafting causes a blue shift in the emission wavelength of the perovskite quantum dots.

[0091] Figure 22 These are the actual pictures of CsPbBr3@MSNs@SiO2 prepared according to the mass ratio of CsPbBr3:MSNs of 1:1, 1:0.8, 1:0.6 and 1:0.3 under natural light (left) and ultraviolet light (right).

[0092] The above description is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and changes can be made without departing from the principles of the present invention. These improvements and changes are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a high-loading rate CsPbBr3@MSNs@SiO2 composite material, characterized in that: The following steps are involved: preparing uniformly dispersed mesoporous silica nanospheres; Grafting amino and carboxyl groups onto mesoporous silica nanospheres; CsPbBr3 quantum dots were in situ grown in the pores of mesoporous silica nanospheres grafted with amino and carboxyl groups to obtain CsPbBr3@MSNs composite materials. The pores of the mesoporous silica nanospheres are sealed by SiO2 obtained by hydrolysis of a silicon source, and a secondary coating is performed to finally obtain the high-loading rate CsPbBr3@MSNs@SiO2 composite material.

2. The method for preparing the high-loading rate CsPbBr3@MSNs@SiO2 composite material according to claim 1, characterized in that: The specific steps include: (1) Prepare uniformly dispersed mesoporous silica nanospheres; (2) uniformly dispersing the mesoporous silica nanospheres prepared in step (1) in a dispersing solvent, adding an amino modifier and stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain amino-grafted mesoporous silica nanospheres; (3) uniformly dispersing the amino-grafted mesoporous silica nanospheres obtained in step (2) in a dispersing solvent, and gradually adding a dispersing solvent containing a carboxyl modifier, stirring until the reaction is fully completed, centrifuging, washing, and drying to obtain mesoporous silica nanospheres grafted with amino and carboxyl groups; (4) uniformly mixing the cesium source, the lead source, the mesoporous silica nanospheres grafted with amino and carboxyl groups obtained in step (3), oleic acid, oleylamine, and octadecene, and removing excess water and oxygen; (5) Heating under an inert atmosphere, injecting a bromine source at a certain temperature to react, and then quenching the reaction in an ice-water bath; (6) The product obtained in step (5) is centrifuged and washed to obtain a CsPbBr3@MSNs composite material; (7) The CsPbBr3@MSNs composite material obtained in step (6) is dispersed in a non-polar solvent, a silicon source is added dropwise and stirred to fully hydrolyze it, and the CsPbBr3@MSNs@SiO2 composite material is obtained after centrifugation and washing.

3. The method for preparing the high-loading rate CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In step (1), the preparation method of the mesoporous silica nanospheres is as follows: hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine and water are mixed in a ratio of 0.96-0.98g:0.16g:50-60ml, and stirred at 80-100°C at 500-1000 rpm until dissolved and mixed uniformly to obtain a transparent precursor solution; tetraethyl orthosilicate is added to the precursor solution, and stirred continuously at 80-100°C at a speed of 500-1000 rpm for 2-4h, wherein the mixing ratio of tetraethyl orthosilicate to the precursor solution is 8ml:50-80ml; the obtained reaction solution is collected, centrifuged, washed, dried, and then calcined at 550°C to obtain the mesoporous silica nanospheres.

4. The method for preparing the high-loading rate CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In step (2), the amino modifier is at least one of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the dispersing solvent is a polar solvent.

5. The method for preparing the high-loading rate CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In step (3), the carboxyl modifier is at least one of succinic anhydride, benzoic acid, and chloroacetic acid, and the dispersing solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and acetone.

6. The method for preparing the high-loading CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In step (4), the cesium source is Cs2CO3, CsNO3, or CH3COOCs, the lead source is at least one of Pb(OAc)2, Pb(NO3)2, and hydrates thereof, and the molar ratio of cesium to lead is 1:1-1.

5.

7. The method for preparing the high-loading CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In the step (5), the temperature is raised to 130-150° C. and a bromine source is added to carry out the reaction. The reaction time is within 20 seconds. The bromine source is at least one of benzoyl bromide and vinyl bromide. The molar ratio of the bromine source to the cesium source is 1:3-7.

8. The method for preparing the high-loading CsPbBr3@MSNs@SiO2 composite material according to claim 2, characterized in that: In the step (7), the non-polar solvent is at least one of n-hexane, cyclohexane, and toluene, and the silicon source is at least one of tetraethyl orthosilicate, tetramethoxysilane, and phenyltriethoxysilane.

9. A high-loading CsPbBr3@MSNs@SiO2 composite material, characterized in that: The preparation method according to any one of claims 1 to 8 is adopted, wherein the feeding mass ratio of CsPbBr3 to MSNs is 1:0.6-1.

10. An application of a high-loading CsPbBr3@MSNs@SiO2 composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The high-loading CsPbBr3@MSNs@SiO2 composite material is applied in the fields of lighting, display applications, solar cells, sensors, photodetectors, lasers and light-emitting diodes.

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