High-brightness quantum dot fluorescent microspheres and preparation method thereof based on alkali catalysis strategy

Abstract

The application discloses a high-brightness quantum dot fluorescent microsphere and a preparation method thereof based on an alkali catalysis strategy, and comprises the following steps: (1) preparing thiol-modified dendritic mesoporous silica microspheres; (2) assembling the thiol-modified dendritic mesoporous silica microspheres and quantum dots to obtain a dendritic silica / quantum dot assembly; (3) adding 3-mercaptopropyl triethoxysilane to the dendritic silica / quantum dot assembly, and performing organic silane modification on the dendritic silica / quantum dot assembly in a non-polar organic solvent by taking an organic alkali as an alkali catalyst; and (4) growing a silica shell layer on the surface of the organic silane-modified dendritic silica / quantum dot assembly by a method to obtain the high-brightness quantum dot fluorescent microsphere. The preparation method avoids fluorescence quenching of oil-phase quantum dots in the process of coating silica, and completely retains excellent optical properties of the oil-phase quantum dots.

Description

Technical Field

[0001] This invention relates to the field of quantum dot fluorescent materials technology, and in particular to a high-brightness quantum dot fluorescent microsphere and its preparation method based on an alkaline catalysis strategy. Background Technology

[0002] Quantum dots possess excellent optical properties such as high fluorescence emission efficiency, continuously tunable fluorescence emission spectrum, broad absorption spectrum, narrow emission spectrum, and resistance to photobleaching, making them a hot topic of widespread interest in the biomedical field in recent years.

[0003] Currently, quantum dots with high luminescence efficiency, narrow half-width, single-exponential fluorescence decay kinetics, and flicker-free luminescence are typically synthesized in organic phases, with their surfaces encapsulated by hydrophobic organic ligands such as fatty acids and aliphatic amines. This limits their direct application in biological systems. The key to their biological applications lies in how to modify the surface of quantum dots to impart water solubility while maintaining their excellent optical properties.

[0004] It has been reported that encapsulating silica in oil-phase quantum dots can impart water solubility to the quantum dots, which can be divided into two types. The first type is the sol-gel process. One method involves using quantum dots as seed liquid and a mixture of ethanol and water as reaction medium to grow silica under the catalysis of ammonia. The resulting silica spheres contain one or more quantum dots. However, the size distribution and dispersion of the quantum dot / silica particles prepared by this method are relatively poor (e.g., Ma Y, Li Y, Ma S, et al. Highly bright water-soluble silica coated quantum dots with excellent stability[J]. Journal of Materials Chemistry B, 2014, 2(31): 5043-5051.). Another method is a "water-in-oil" reverse microemulsion system. Hydrolyzed tetraethyl silicate undergoes ligand exchange with the hydrophobic ligands on the surface of the quantum dots, causing the quantum dots to transfer into hydrophilic micelles. Ammonia is used as a silane hydrolysis catalyst to achieve silica growth (e.g., Chinese Patent CN 110129025 A discloses a method for preparing silica-coated quantum dots).

[0005] Unfortunately, both of these methods require the use of polar reagents such as alcohols, water, and ammonia, which inevitably leads to the deterioration of the optical properties of oil-phase quantum dots and a significant reduction in fluorescence quantum yield.

[0006] Therefore, there is an urgent need for a novel method for preparing quantum dot fluorescent nanospheres that avoids the reduction of fluorescence properties during the process of encapsulating silica with oil-phase quantum dots. Summary of the Invention

[0007] This invention provides a high-brightness quantum dot fluorescent microsphere and its preparation method based on an alkaline catalysis strategy. The preparation method of this invention avoids fluorescence quenching of oil-phase quantum dots during the process of coating with silica.

[0008] The technical solution of the present invention is as follows:

[0009] A method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy includes the following steps:

[0010] (1) Preparation of mercapto-modified dendritic mesoporous silica microspheres;

[0011] (2) Thiol-modified dendritic mesoporous silica microspheres were assembled with quantum dots to obtain a dendritic silica / quantum dot assembly;

[0012] (3) Add 3-mercaptopropyltriethoxysilane to the dendritic silica / quantum dot assembly and modify the dendritic silica / quantum dot assembly with an organic base as a base catalyst in a non-polar organic solvent.

[0013] (4) Through The method grows a silica shell on the surface of an organosilane-modified dendritic silica / quantum dot assembly to obtain high-brightness quantum dot fluorescent microspheres.

[0014] This invention utilizes the coordination interaction between metal and sulfur groups to assemble oil-phase quantum dots on a dendritic mesoporous silica microsphere template; then, using 3-mercaptopropyltriethoxysilane (MPTMS) as a silane reagent, and an organic base as a base catalyst in a nonpolar organic solvent, a silane-modified dendritic silica / quantum dot composite material is obtained, realizing the transformation of quantum dots from lipophilic to hydrophilic; finally, through... The method involves growing a silica shell on the surface of an organosilane-modified dendritic silica / quantum dot assembly. This preparation method avoids fluorescence quenching of oil-phase quantum dots during silica coating, while the chemically inert silica shell acts as a barrier, isolating external factors from the optical properties of the quantum dots and significantly improving the stability of the quantum dot microspheres.

[0015] Preferably, step (1) includes: preparing dendritic mesoporous silica by template method, and then modifying the surface of dendritic mesoporous silica with thiol groups to obtain thiol-modified dendritic mesoporous silica microspheres.

[0016] More preferably, step (1) includes:

[0017] (1-1) Using hexadecyltrimethylammonium bromide (CTAB) as a template, sodium salicylate (NaSaI) as a structure directing agent, triethanolamine (TEA) as a catalyst, and water as a solvent, the reaction was stirred at 50-100℃ for 0.5-2h, and then a silicon source was added and the reaction was stirred for another 2-3.5h to obtain dendritic mesoporous silica.

[0018] (1-2) Add 3-mercaptopropyltriethoxysilane (MPTMS) and an alkaline solution to dendritic mesoporous silica, and stir the reaction at room temperature to obtain mercapto-modified dendritic mesoporous silica microspheres.

[0019] In step (1-1), a series of reaction parameters, such as the amount of raw materials fed and the reaction time, are adjusted to obtain dendritic silica of different sizes.

[0020] Preferably, in step (1-1), the mass ratio of hexadecyltrimethylammonium bromide, sodium salicylate, and triethanolamine is 1:0.1-1.1:0.1-0.2.

[0021] Preferably, the particle size of the thiol-modified dendritic mesoporous silica microspheres is 100-500 nm.

[0022] Preferably, in step (2), the mass ratio of thiol-modified dendritic mesoporous silica microspheres to quantum dots is 1:1-2.

[0023] Preferably, step (2) includes: adding oil-soluble quantum dots to a mercapto-modified dendritic mesoporous silica microsphere dispersion, and sonicating for 5-30 minutes to obtain a dendritic silica / quantum dot assembly.

[0024] Preferably, the quantum dots are at least one of CdSe / CdS / ZnS, CdZnSeS / ZnS, CdSe / CdZnS, InP / ZnSe / ZnS, and CuInS2 / ZnS; and the ligands on the surface of the quantum dots are at least one of oleic acid, decaic acid, stearic acid, and n-dodecyl mercaptan.

[0025] Preferably, step (3) includes: adding 3-mercaptopropyltriethoxysilane to the dendritic silica / quantum dot assembly, using an organic base as a base catalyst in a nonpolar organic solvent, and stirring at room temperature for 60-120 min to obtain an organosilane-modified dendritic silica / quantum dot assembly.

[0026] More preferably, in step (3), the nonpolar organic solvent is at least one of toluene, chloroform, octane, and cyclohexane.

[0027] More preferably, in step (3), the organic base is at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and hexamethyldiammonium hydroxide.

[0028] More preferably, in step (3), the volume ratio of 3-mercaptopropyltriethoxysilane to organic base is 1:0.3-1.

[0029] Preferably, step (4) includes: adding a silicon source to the dispersion of the organosilane-modified dendritic silica / quantum dot assembly, and stirring the reaction at room temperature for 18-36 h under the action of an alkaline catalyst to obtain high-brightness quantum dot fluorescent microspheres.

[0030] More preferably, in step (4), the alkaline catalyst is at least one of ammonia, dimethylamine, ethylenediamine, triethylamine, and tetramethylammonium hydroxide.

[0031] More preferably, in step (4), the alkaline catalyst is 25-28 wt% ammonia water; the silicon source is tetraethyl silicate; and the volume ratio of silicon source to alkaline catalyst is 1:1-3.

[0032] The present invention also provides a high-brightness quantum dot fluorescent microsphere prepared by the above preparation method.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention modifies the surface of oil-phase quantum dots using 3-mercaptopropyltriethoxysilane, and uses an organic base as a catalyst and a non-polar organic solvent as a solvent. Under the condition of not using any polar solvent, the transformation of oil-phase quantum dots from oleophilic to hydrophilic is achieved, and the excellent optical properties of oil-phase quantum dots are completely preserved. The resulting quantum dot microspheres have a high fluorescence quantum yield. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the preparation process for high-brightness quantum dot composite microspheres.

[0036] Figure 2 Transmission electron microscope (TEM) images of CdSe / CdS / ZnS quantum dots (a), 250nm dendritic mesoporous silica (b), dendritic mesoporous silica / CdSe / CdS / ZnS quantum dots (c), and dendritic mesoporous silica / CdSe / CdS / ZnS quantum dot / silica composite microspheres (d) in Example 1. The inset in (a) is a high-resolution TEM image of the quantum dots.

[0037] Figure 3 This is a comparison of fluorescence intensity before and after oil-phase quantum dots are coated with silica in Example 1.

[0038] Figure 4 This is a comparison of fluorescence kinetic decay curves before and after oil-phase quantum dots are coated with silica in Example 1.

[0039] Figure 5 The relative fluorescence intensity of the quantum dot composite microspheres in Example 1 at different NaCl concentrations is given.

[0040] Figure 6 The relative fluorescence intensity of the quantum dot composite microspheres in Example 1 at different pH values ​​is given.

[0041] Figure 7 The relative fluorescence intensity of the quantum dot composite microspheres in Example 1 after 30 days of storage. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0043] The preparation process of the high-brightness quantum dot composite microspheres of the present invention is as follows: Figure 1 As shown.

[0044] Example 1

[0045] (1) Synthesis of dendritic mesoporous silica (dSiO2) support with a size of 250 nm

[0046] 68 mg of triethanolamine (TEA) was dissolved in 25 mL of deionized water and stirred at 80 °C for 30 min. Then, 380 mg of cetyltrimethylammonium bromide (CTAB) and 168 mg of sodium salicylate (NaSaI) were added, and the reaction was continued at 80 °C for 1 h. Afterward, 4 mL of tetraethyl silicate (TEOS) was added to the solution, and the reaction was continued at 80 °C for 2 h. After the reaction was complete, the precipitate was collected by centrifugation with ethanol. Purification was performed using a 100 mL hydrochloric acid / methanol mixture (volume ratio 1:1) and stirred at 60 °C for 6 h. This step was repeated three times to remove excess organic template agent cetyltrimethylammonium bromide. Finally, the mixture was centrifuged three times with ethanol at 9000 rpm for 3 min each time, and then redispersed in 100 mL of ethanol to prepare dendritic silica spheres with a size of 250 nm.

[0047] (2) Surface thiolization treatment of dendritic mesoporous silica

[0048] Add 1 mL of 3-mercaptopropyltriethoxysilane (MPTMS) and 2.5 mL of ammonia solution (mass concentration of 25-28 wt%) to the ethanol solution of dendritic mesoporous silica prepared in step (1), stir the reaction at room temperature for 15 h, centrifuge three times with ethanol, centrifuge at 8000 rpm for 5 min, and disperse the collected precipitate again in 50 mL of ethanol to obtain thiol-functionalized dendritic silica (dSiO2-SH) template.

[0049] (3) Preparation of dendritic silica / quantum dot (dSiO2 / QDs) assemblies

[0050] The ethanol solution of the mercapto-modified silica template from step (2) was centrifuged at 8000 rpm for 5 min, the supernatant was discarded, the precipitate was dried and 10 mg was accurately weighed, and 1 mL of purified CdSe / CdS / ZnS quantum dot chloroform solution (purifying agent is a mixed solution of chloroform, acetone and methanol, volume ratio of 1:1:1, quantum dot concentration of 15 mg / mL) was added, and the mixture was sonicated for 10 min. In this step, CdSe / CdS / ZnS quantum dots were assembled in the pores of dendritic silica. After centrifugation at 10000 rpm for 5 min, the precipitate was washed with chloroform to remove free quantum dots, yielding dendritic silica / quantum dot (dSiO2 / QDs) assemblies, which were dispersed in 5 mL of toluene solution for later use.

[0051] (4) Preparation of dendritic silica / quantum dot / silica (SQS) fluorescent nanospheres

[0052] The dSiO2 / QDs assembly was dispersed in 20 mL of toluene solution, followed by the addition of 30 μL of 3-mercaptopropyltriethoxysilane (MPTMS) and 30 μL of tetramethylammonium hydroxide. The mixture was stirred at room temperature for 1 h to obtain organosilane-modified dendritic silica / quantum dots (dSiO2 / QDs / MPTMS). The dSiO2 / QDs / MPTMS was centrifuged at 10000 rpm for 5 min, and the precipitate was washed again with ethanol. Further processing was carried out... To grow a silica shell, the above precipitate was dispersed in 20 mL of ethanol, and 100 μL of tetraethyl orthosilicate, 200 μL of ammonia, and 200 μL of water were added. The mixture was stirred at room temperature for 18 h. The solution was centrifuged and washed three times with ethanol to obtain high-brightness dendritic silica / quantum dot / silica fluorescent nanospheres.

[0053] Depend on Figure 2 Transmission electron microscope images show that the quantum dots, dendritic silica carriers, dendritic silica / quantum dot assemblies, and dendritic silica / quantum dot / silica composite microspheres in Example 1 exhibit good monodispersity and uniform particle size.

[0054] The dendritic silica / quantum dot / silica nanospheres prepared in this embodiment exhibit excellent optical properties and a quantum yield exceeding 95%. Figure 3 It can be seen that the position, full width at half maximum (FWHM), and intensity of the fluorescence spectrum of the quantum dot microspheres before and after being coated with silica do not change significantly. Figure 4 This indicates that the fluorescence kinetic decay curves of the quantum dot microspheres before and after coating with silica can still be fitted by a single exponential function, and no new non-radiative recombination channels are generated. This shows that the dendritic silica / quantum dot / silica nanospheres prepared in this embodiment maintain good optical properties.

[0055] The dendritic silica / quantum dot / silica nanospheres prepared in this embodiment exhibit ultra-stable optical properties. Figure 5 It can be seen that the fluorescence intensity of dendritic silica / quantum dot / silica nanospheres remains almost unchanged even at salt concentrations as high as 1M NaCl. Figure 6 It can be seen that the fluorescence intensity of dendritic silica / quantum dot / silica nanospheres remains above 90% at different pH values. (From...) Figure 7 It can be seen that the change in fluorescence intensity of dendritic silica / quantum dot / silica nanospheres after 30 days of storage is negligible.

[0056] Example 2

[0057] (1) Synthesis of dendritic mesoporous silica (dSiO2) support with a size of 360 nm

[0058] 68 mg of triethanolamine was dissolved in 25 mL of deionized water and stirred at 80 °C for 30 min. Then, 380 mg of cetyltrimethylammonium bromide (CTAB) and 268 mg of sodium salicylate (NaSaI) were added, and the reaction was continued at 80 °C for 1.5 h. Afterward, 4 mL of tetraethyl orthosilicate (TEOS) was added to the solution, and the reaction was continued at 80 °C for 3 h. After the reaction was complete, the precipitate was collected by centrifugation with ethanol. Purification was performed using a 100 mL hydrochloric acid / methanol mixture (1:1 volume ratio) and stirring at 60 °C for 6 h. This step was repeated at least three times to remove excess CTAB template agent. Finally, the precipitate was purified three times by centrifugation at 9000 rpm for 3 min and then redispersed in 100 mL of ethanol to prepare dendritic silica with a size of 360 nm.

[0059] (2) Surface thiolization treatment of dendritic mesoporous silica

[0060] Add 1 mL of 3-mercaptopropyltriethoxysilane (MPTMS) and 3 mL of ammonia solution (25-28 wt%) to the ethanol solution of the dendritic mesoporous silica synthesized in step (1). Stir slowly at room temperature for 15 h. Finally, centrifuge three times with ethanol at 8000 rpm for 5 min. Disperse the collected precipitate again in 50 mL of ethanol to obtain a thiol-functionalized dendritic silica (dSiO2-SH) template.

[0061] (3) Preparation of dendritic silica / quantum dot (dSiO2 / QDs) assemblies

[0062] The ethanol solution of the mercapto-modified silica template was centrifuged at 8000 rpm for 5 min, the supernatant was discarded, the precipitate was dried and 15 mg was accurately weighed, and 1 mL of purified CdSe / CdZnS quantum dot toluene solution (the purification agent was a mixture of chloroform, acetone and methanol in a volume ratio of 1:1:1, and the quantum dot concentration was 20 mg / mL) was added. The solution was sonicated for 10 min to obtain a homogeneous and transparent solution. In this step, CdSe / CdZnS quantum dots were assembled in the pores of dendritic silica. The dendritic silica / quantum dot (dSiO2 / QDs) assembly was collected by centrifugation at 10000 rpm for 5 min. The precipitate was washed with chloroform to remove free quantum dots and then redispersed in 5 mL of toluene solution for later use.

[0063] (4) Preparation of dendritic silica / quantum dot / silica (SQS) fluorescent nanospheres

[0064] The dSiO2 / QDs assembly was dispersed in 20 mL of toluene solution, followed by the addition of 50 μL of 3-mercaptopropyltriethoxysilane and 40 μL of tetramethylammonium hydroxide. The mixture was stirred at room temperature for 2 h to obtain organosilane-modified dendritic silica / quantum dots (dSiO2 / QDs / MPTMS). The dSiO2 / QDs / MPTMS was centrifuged at 10000 rpm for 5 min, and the precipitate was washed again with ethanol. Further processing was carried out... To grow a silica shell, the above precipitate was dispersed in 20 mL of ethanol, and 150 μL of tetraethyl orthosilicate, 300 μL of ammonia, and 300 μL of water were added. The mixture was stirred at room temperature for 30 h. The solution was centrifuged and washed three times with ethanol to obtain high-brightness dendritic silica / quantum dot / silica fluorescent nanospheres.

[0065] Example 3

[0066] (1) Synthesis of dendritic mesoporous silica (dSiO2) support with a size of 120 nm

[0067] 68 mg of triethanolamine was dissolved in 25 mL of deionized water and stirred at 80 °C for 30 min. Then, 380 mg of cetyltrimethylammonium bromide (CTAB) and 60 mg of sodium salicylate (NaSaI) were added, and the reaction was continued at 80 °C for 1.5 h. Next, 4 mL of tetraethyl orthosilicate (TEOS) was added to the solution, and the reaction was continued at 80 °C for 4 h. After the reaction was complete, the precipitate was collected by centrifugation with ethanol. Finally, the precipitate was purified by centrifugation with 100 mL of a 1:1 hydrochloric acid / methanol mixture and stirred at 60 °C for 6 h. This step was repeated three times to remove excess CTAB template agent. Finally, the precipitate was purified three times by centrifugation with ethanol and dispersed in 100 mL of ethanol to prepare dendritic silica with a size of 120 nm.

[0068] (2) Surface thiolization treatment of dendritic mesoporous silica

[0069] Add 1.5 mL of 3-mercaptopropyltriethoxysilane (MPTMS) and 3 mL of ammonia solution (25-28 wt%) to the ethanol solution of dendritic mesoporous silica in step (1). Stir slowly at room temperature for 12 h. Finally, centrifuge three times with ethanol at 8000 rpm for 5 min, collect the precipitate and redisperse it in 50 mL of ethanol.

[0070] (3) Preparation of dendritic silica / quantum dot (dSiO2 / QDs) assemblies

[0071] The ethanol solution of the mercapto-modified silica template was centrifuged at 8000 rpm for 5 min, the supernatant was discarded, the precipitate was dried and 15 mg was accurately weighed, and 1 mL of purified CdZnSeS / ZnS quantum dot chloroform solution (the purification agent was a mixture of chloroform, acetone and methanol in a volume ratio of 1:1:1, and the quantum dot concentration was 15 mg / mL) was added. The solution was sonicated for 10 min to obtain a homogeneous and transparent solution. In this step, CdZnSeS / ZnS quantum dots were assembled in the pores of dendritic silica. The dendritic silica / quantum dot assembly was collected by centrifugation at 10000 rpm for 5 min. The precipitate was washed again with chloroform to remove free quantum dots and then redispersed in 5 mL of toluene solution for later use.

[0072] (4) Preparation of dendritic silica / quantum dot / silica (SQS) fluorescent nanospheres

[0073] The dSiO2 / QDs assembly was dispersed in 20 mL of toluene solution, followed by the addition of 50 μL of 3-mercaptopropyltriethoxysilane and 40 μL of tetramethylammonium hydroxide. The mixture was stirred at room temperature for 2 h to obtain organosilane-modified dendritic silica / quantum dots (dSiO2 / QDs / MPTMS). The dSiO2 / QDs / MPTMS was centrifuged at 10000 rpm for 5 min, and the precipitate was washed again with ethanol. Further processing was carried out... To grow a silica shell, the above precipitate was dispersed in 20 mL of ethanol, and 100 μL of tetraethyl orthosilicate, 200 μL of ammonia, and 300 μL of water were added. The mixture was stirred at room temperature for 18 h. The solution was centrifuged and washed three times with ethanol to obtain high-brightness dendritic silica / quantum dot / silica fluorescent nanospheres.

[0074] Example 4

[0075] (1) Synthesis of dendritic mesoporous silica (dSiO2) support with a size of 470 nm

[0076] 68 mg of triethanolamine was dissolved in 25 mL of deionized water and stirred at 80 °C for 30 min. Then, 380 mg of cetyltrimethylammonium bromide (CTAB) and 420 mg of sodium salicylate (NaSaI) were added, and the reaction was continued at 80 °C for 1 h. Afterward, 4 mL of tetraethyl orthosilicate (TEOS) was added to the solution, and the reaction was continued at 80 °C for 2 h. After the reaction was complete, the precipitate was collected by centrifugation with ethanol. Finally, the precipitate was purified by centrifugation with 100 mL of a 1:1 hydrochloric acid / methanol mixture and stirred at 60 °C for 6 h. This step was repeated three times to remove excess CTAB template agent. Finally, the precipitate was purified three times by centrifugation with ethanol and dispersed in 100 mL of ethanol to prepare dendritic silica with a size of 470 nm.

[0077] (2) Surface thiolization treatment of dendritic mesoporous silica

[0078] Add 1 mL of 3-mercaptopropyltriethoxysilane (MPTMS) and 2.5 mL of ammonia solution (mass concentration of 25-28 wt%) to the ethanol solution of dendritic mesoporous silica synthesized in step (1), stir slowly at room temperature for 24 h, and finally centrifuge three times with ethanol at 9000 rpm for 3 min, collect the precipitate and redisperse it in 50 mL of ethanol.

[0079] (3) Preparation of dendritic silica / quantum dot (dSiO2 / QDs) assemblies

[0080] The ethanol solution of the mercapto-modified silica template was centrifuged at 9000 rpm for 3 min, the supernatant was discarded, the precipitate was dried and 15 mg was accurately weighed, and 1 mL of purified InP / ZnSe / ZnS quantum dot toluene solution (purification agent was a mixture of octane and ethanol, volume ratio 1:2, quantum dot concentration 15 mg / mL) was added. The solution was sonicated for 10 min to obtain a homogeneous and transparent solution. In this step, InP / ZnSe / ZnS quantum dots were assembled in the pores of dendritic silica. The dendritic silica / quantum dot assembly was collected by centrifugation at 10000 rpm for 5 min. The precipitate was washed with chloroform to remove free quantum dots and then redispersed in 5 mL of toluene solution for later use.

[0081] (4) Preparation of dendritic silica / quantum dot / silica (SQS) fluorescent nanospheres

[0082] The dSiO2 / QDs assembly was dispersed in 20 mL of toluene solution, followed by the addition of 50 μL of 3-mercaptopropyltriethoxysilane and 35 μL of tetramethylammonium hydroxide. The mixture was stirred at room temperature for 2 h to obtain organosilane-modified dendritic silica / quantum dots (dSiO2 / QDs / MPTMS). The dSiO2 / QDs / MPTMS was centrifuged at 8000 rpm for 5 min, and the precipitate was washed again with ethanol. Further processing was carried out... To grow a silica shell, the above precipitate was dispersed in 20 mL of ethanol, and 200 μL of tetraethyl orthosilicate, 250 μL of ammonia, and 300 μL of water were added. The mixture was stirred at room temperature for 36 h. The solution was centrifuged and washed three times with ethanol to obtain high-brightness dendritic silica / quantum dot / silica fluorescent nanospheres.

[0083] The dendritic silica / quantum dot / silica fluorescent nanospheres prepared in Examples 2-4 have similar optical properties to the microspheres prepared in Example 1.

[0084] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy, characterized in that, Includes the following steps: (1) Preparation of mercapto-modified dendritic mesoporous silica microspheres; (2) A dendritic mesoporous silica microsphere modified with mercapto groups is assembled with quantum dots to obtain a dendritic silica / quantum dot assembly; wherein the quantum dots are at least one of CdSe / CdS / ZnS, CdZnSeS / ZnS, CdSe / CdZnS, InP / ZnSe / ZnS, CuInS2 / ZnS; and the ligands on the surface of the quantum dots are at least one of oleic acid, decaic acid, stearic acid, and n-dodecyl mercaptan. (3) Add 3-mercaptopropyltriethoxysilane to the dendritic silica / quantum dot assembly, and modify the dendritic silica / quantum dot assembly with an organic base as a base catalyst in a non-polar organic solvent; wherein the non-polar organic solvent is at least one of toluene, chloroform, octane, and cyclohexane; wherein the organic base is at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and hexamethyldiammonium hydroxide. (4) A silica shell was grown on the surface of an organosilane-modified dendritic silica / quantum dot assembly by the Stöber method to obtain high-brightness quantum dot fluorescent microspheres.

2. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 1, characterized in that, Step (1) includes: preparing dendritic mesoporous silica by template method, and then modifying the surface of dendritic mesoporous silica with thiol groups to obtain thiol-modified dendritic mesoporous silica microspheres.

3. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 2, characterized in that, Step (1) includes: (1-1) Using hexadecyltrimethylammonium bromide as a template, sodium salicylate as a structure directing agent, triethanolamine as a catalyst, and water as a solvent, the reaction was stirred at 50-100 °C for 0.5-2 h, and then a silicon source was added and the reaction was stirred for another 2-3.5 h to obtain dendritic mesoporous silica. (1-2) Add 3-mercaptopropyltriethoxysilane and an alkaline solution to dendritic mesoporous silica and stir the reaction at room temperature to obtain mercapto-modified dendritic mesoporous silica microspheres.

4. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 1, characterized in that, The thiol-modified dendritic mesoporous silica microspheres have a particle size of 100-500 nm.

5. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 1, characterized in that, In step (2), the mass ratio of mercapto-modified dendritic mesoporous silica microspheres to quantum dots is 1:1-2.

6. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 1, characterized in that, Step (4) includes: adding a silicon source to the dispersion of the organosilane-modified dendritic silica / quantum dot assembly, and stirring the reaction at room temperature for 18-36 h under the action of an alkaline catalyst to obtain high-brightness quantum dot fluorescent microspheres.

7. The method for preparing high-brightness quantum dot fluorescent microspheres based on an alkaline catalysis strategy according to claim 6, characterized in that, In step (4), the alkaline catalyst is 25-28 wt% ammonia water; the silicon source is tetraethyl silicate; and the volume ratio of silicon source to alkaline catalyst is 1:1-3.

8. A high-brightness quantum dot fluorescent microsphere, characterized in that, Prepared by the method described in any one of claims 1-7.

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