Preparation method of double-mesoporous silica nanospheres

Abstract

The invention relates to a preparation method of double-mesoporous silica nanospheres, which comprises the following steps: (1) dissolving a cationic surfactant in water to form a uniform solution, adding an alcohol amine catalyst, and fully stirring to obtain a mixed solution; dissolving a silicon source in an organic solvent, and dropwise adding onto the mixed solution to form an upper-layer oil phase; (2) reacting the two-phase layered system obtained in the step (1) at 40-80 DEG C for 6-12 hours to obtain mesoporous silica nanospheres; (3) injecting a second catalyst into the lower-layer water phase, continuously reacting for 12-18 hours, and centrifugally separating after the reaction is finished; and (4) dispersing the product obtained in the step (3) into an ethanol-water solution, performing reflux extraction on the surfactant, and performing centrifugal separation after the reaction is finished to obtain the double-mesoporous silicon dioxide nanospheres. The preparation process is high in controllability, simple, convenient to operate and low in cost, and has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of nanospheres, and particularly relates to a method for preparing double-mesoporous silica nanospheres. Background Art

[0002] In recent years, the construction of porous materials with multi-level pore structures, such as macropore-mesopore, mesopore-micropore, etc., can give the materials more excellent performance, and therefore has attracted the attention of researchers. Research on mesopore-mesopore multi-level pore structures has also begun to emerge gradually, because different mesoporous structures can increase the specific surface area of ​​the material, can contact and interact with more guest molecules, and can increase the rapid diffusion of guest molecules inside the pores. This characteristic will inevitably promote the application of dual-mesoporous materials in adsorption, catalysis, sensing, and biomedicine. Among them, the preparation of spherical dual-mesoporous materials with ultra-small particle size has attracted much attention, mainly because the spherical morphology has the lowest surface energy, and the ultra-small particle size ensures that the mesoporous material can be absorbed by cells to achieve the transportation of drug molecules.

[0003] At present, there are not many methods for preparing double mesoporous silica. The most common one is the dual template method. This method requires the use of two different types of surfactants, accompanied by the volatilization of the solvent to form two stable, independent micelles of different sizes, and then control the two different types and sizes of micelles to co-assemble with the hydrolyzate of the silica precursor. This method requires the volatilization of the solvent, so the cost is relatively high, and the resulting material is a large bulk structure, and spherical nano-scale particles cannot be obtained.

[0004] The oil-water two-phase synthesis system is also a universal method for preparing dual-mesoporous silica nanospheres. It utilizes the pore expansion effect of the upper oil phase and replaces the type of the upper oil phase at a certain stage of the reaction to achieve pore size changes for subsequent reactions. Therefore, it is the simplest method to operate, but the replacement of the upper oil phase greatly increases the cost. Therefore, it is of great significance to develop a simple synthesis method to prepare silica nanospheres with dual mesoporous structures. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing double-mesoporous silica nanospheres, the preparation process of which is highly controllable, simple, easy to operate, low-cost and has good application prospects.

[0006] The present invention provides a method for preparing double-mesoporous silica nanospheres, comprising the following steps: (1) Dissolving the template in water to form a uniform solution, then adding an alcohol amine catalyst and stirring thoroughly to obtain a mixed solution; dissolving a silicon source in an organic solvent and dropping the mixture onto the mixed solution to form an upper oil phase; (2) reacting the two-phase stratified system obtained in step (1) at 40-80° C. for 6-12 hours to obtain mesoporous silica nanospheres; (3) injecting the second catalyst into the lower aqueous phase, continuing the reaction for 12-18 hours, and centrifuging after the reaction is completed; (4) The product obtained in step (3) is dispersed in an ethanol-water solution, and the template agent is extracted by reflux. After the reaction is completed, the product is centrifuged to obtain double mesoporous silica nanospheres.

[0007] Preferably, the template in step (1) is a quaternary ammonium salt cationic surfactant, and its concentration in the uniform solution is 5-15 wt %.

[0008] Preferably, the alcoholamine catalyst in step (1) is ethanolamine; and the mass ratio of the alcoholamine catalyst to the silicon source is 0.01-0.12:1.

[0009] Preferably, the silicon source in step (1) is selected from one or more of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate.

[0010] Preferably, the organic solvent in step (1) is selected from one or more of cyclohexane, n-hexane, decahydronaphthalene and olefins.

[0011] Preferably, the second catalyst in step (3) is ethylenediamine; and the mass ratio of the second catalyst to the alcoholamine catalyst is 0.05-0.25:1.

[0012] Preferably, the water content in the ethanol-water solution in step (4) is 10-20%.

[0013] Beneficial Effects (1) The present invention uses highly alkaline ethylenediamine as the catalyst for the second stage. Since ethylenediamine is more likely to etch the silica structure than alcohol amine, the silica component grown in the second stage can be selectively etched during the hydrothermal treatment to obtain a dual mesoporous structure.

[0014] (2) The present invention adopts an ethanol-water reflux system to achieve a dual mesoporous structure.

[0015] (3) The present invention adopts a two-step catalytic oil-water two-phase method and an ethanol-water reflux system. During the ethanol-water reflux process, the ethanol component effectively extracts the surfactant, and the water component etches part of the silica synthesized in the second stage. Since the microscopic existence forms of the silica synthesized twice are different: the silica synthesized in the first step contains alcoholamine inside, and the silica synthesized in the second step contains ethylenediamine and alcoholamine inside. Therefore, during high-temperature reflux treatment, ethylenediamine can easily etch part of the silica component to obtain a monodisperse double-mesoporous silica nanosphere material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a characteristic transmission electron microscope (TEM) image of the double mesoporous silica nanospheres in Example 1.

[0017] Figure 2 This is the pore size distribution diagram of the double-mesoporous silica nanospheres in Example 1.

[0018] Figure 3 This is a characteristic transmission electron microscope (TEM) image of the double mesoporous silica nanospheres in Example 2.

[0019] Figure 4 This is the pore size distribution diagram of the double-mesoporous silica nanospheres in Example 2.

[0020] Figure 5 Characteristic transmission electron microscopy (TEM) images of the mesoporous silica nanospheres obtained in Comparative Example 1 (adding excess ethylenediamine) before (a) and after (b) reflux extraction.

[0021] Figure 6 This is a characteristic transmission electron microscope (TEM) image of the mesoporous silica nanospheres obtained in Comparative Example 2 (without adding ethylenediamine). DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] Example 1 (1) Dissolve 3.0 g of hexadecyltrimethylammonium bromide and 0.10 g of monoethanolamine in 60 mL of deionized water, control the oil bath temperature to 40°C, and stir gently to form a colorless and transparent solution. Carefully add 20 mL of 30% TEOS cyclohexane solution to the above solution, stirring at a speed that keeps the lower aqueous phase stirring while the oil phase is basically still, and react for 12 hours under this stable condition.

[0024] (2) Use a syringe to inject 0.01 g of ethylenediamine into the lower aqueous phase and continue the reaction for 12 hours. After the reaction is completed, centrifuge at high speed (12000 rpm, 5 min) for centrifugal separation.

[0025] (3) The silica sphere material produced in step (2) was ultrasonically dispersed in a mixed solution of 48 mL ethanol and 12 mL water, and the surfactant was extracted by reflux at an oil bath temperature of 100°C. After the reaction was completed, centrifugal separation was performed to obtain a double mesoporous silica nanosphere material, the TEM image of which is shown in FIG. Figure 1 shown.

[0026] The mesoporous silica nanospheres prepared above clearly show different particle size distributions, such as Figure 2 As shown, the spheres inside have smaller pores, about 5.8nm, and their particle size is about 160nm. The mesoporous channels in the outer layer are significantly larger, about 11.3nm, with a thickness of about 25nm and an overall particle size of about 210nm.

[0027] Example 2 (1) Dissolve 9.0 g of hexadecyltrimethylammonium chloride and 0.3 g of triethanolamine in 60 mL of deionized water, control the oil bath temperature to 75°C, and stir gently to form a colorless and transparent solution. Carefully drop 20 mL of 15% TEOS in decahydronaphthalene solution into the above solution, stirring at a speed that keeps the lower aqueous phase stirring while the oil phase is basically still, and react under this stable condition for 6 hours.

[0028] (2) Use a syringe to inject 0.06 g of ethylenediamine into the lower aqueous phase and continue the reaction for 12 hours. After the reaction is completed, centrifuge at high speed (12000 rpm, 5 min) for centrifugal separation.

[0029] (3) The silica sphere material produced in step (2) was ultrasonically dispersed in a mixed solution of 54 mL ethanol and 6 mL water, and the surfactant was extracted by reflux at an oil bath temperature of 60°C. After the reaction was completed, centrifugal separation was performed to obtain a double mesoporous silica nanosphere material, the TEM image of which is shown in FIG. Figure 3 shown.

[0030] The mesoporous silica nanospheres prepared above clearly showed two different particle size distributions: Figure 4 As shown, the spheres inside have smaller pores, about 6.7nm, and their particle size is about 160nm. The mesoporous channels in the outer layer are significantly larger, about 13.7nm, with a thickness of about 20nm and an overall particle size of about 200nm.

[0031] Comparative Example 1 (1) Dissolve 3.0 g of hexadecyltrimethylammonium bromide and 0.10 g of ethanolamine in 60 mL of deionized water, control the oil bath temperature to 40°C, and stir gently to form a colorless and transparent solution. Carefully add 20 mL of 30% TEOS cyclohexane solution to the above solution, stirring at a speed that keeps the lower aqueous phase stirring while the oil phase is basically still, and react for 12 hours under this stable condition.

[0032] (2) Use a syringe to inject 0.10 g of ethylenediamine into the lower aqueous phase and continue the reaction for 12 hours. After the reaction is completed, centrifuge at high speed (12000 rpm, 5 min) for centrifugal separation.

[0033] (3) The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 48 mL ethanol and 12 mL water, and the surfactant is extracted by reflux at an oil bath temperature of 100°C. After the reaction is completed, centrifugal separation is performed to obtain a mesoporous silica nanosphere material.

[0034] The mesoporous silica nanospheres prepared above are Figure 5 As shown in the figure, the particle size before reflux extraction is about 210nm, the surface is relatively smooth, the pore size is relatively small, and a set of mesoporous structures are clearly present. After reflux extraction, the pore size of the sphere is reduced to about 170nm, and the surface is obviously very messy, indicating that during the reflux extraction stage, excessive ethylenediamine will completely etch the outer mesopores.

[0035] Comparative Example 2 (1) Dissolve 3.0 g of hexadecyltrimethylammonium bromide and 0.10 g of monoethanolamine in 60 mL of deionized water, control the oil bath temperature to 40°C, and stir gently to form a colorless and transparent solution. Carefully add 20 mL of 30% TEOS cyclohexane solution to the above solution, stirring at a speed that keeps the lower aqueous phase stirring while the oil phase is basically still, and react for 12 hours under this stable condition.

[0036] (2) The reaction was continued for 12 hours. After the reaction was completed, the mixture was centrifuged at high speed (12000 rpm, 5 min) for centrifugal separation.

[0037] (3) The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 48 mL ethanol and 12 mL water, and the surfactant is extracted by reflux in an oil bath at a temperature of 100°C. After the reaction is completed, the silica nanosphere material with a mesoporous structure is obtained by centrifugation.

[0038] The mesoporous silica nanospheres prepared above clearly present a set of mesoporous structures, such as Figure 6 As shown, the pore size of the sphere is about 170 nm, indicating that without the addition of ethylenediamine, the particle size and pore size do not change significantly with the increase of reaction time, and no etching occurs during the reflux extraction stage.

Claims

1. A method for preparing double mesoporous silica nanospheres, characterized in that: The steps include: (1) Dissolving the template in water to form a uniform solution, then adding an alcohol amine catalyst and stirring thoroughly to obtain a mixed solution; dissolving a silicon source in an organic solvent and dropping the mixture onto the mixed solution to form an upper oil phase; (2) reacting the two-phase stratified system obtained in step (1) at 40-80° C. for 6-12 hours to obtain mesoporous silica nanospheres; (3) injecting a second catalyst into the lower aqueous phase, continuing the reaction for 12-18 hours, and centrifuging after the reaction is completed; (4) The product obtained in step (3) is dispersed in an ethanol-water solution, and the template agent is extracted by reflux. After the reaction is completed, the product is centrifuged to obtain double mesoporous silica nanospheres.

2. The preparation method according to claim 1, characterized in that: The template in step (1) is a quaternary ammonium salt cationic surfactant, and its concentration in the uniform solution is 5-15wt%.

3. The preparation method according to claim 1, characterized in that: The alcohol amine catalyst in step (1) is ethanolamine; the mass ratio of the alcohol amine catalyst to the silicon source is 0.01-0.12:

1.

4. The preparation method according to claim 1, characterized in that: The silicon source in step (1) is selected from one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

5. The preparation method according to claim 1, characterized in that: The organic solvent in step (1) is selected from one or more of cyclohexane, n-hexane, decahydronaphthalene and olefins.

6. The preparation method according to claim 1, characterized in that: The second catalyst in step (3) is ethylenediamine; the mass ratio of the second catalyst to the alcoholamine catalyst is 0.05-0.25:

1.

7. The preparation method according to claim 1, characterized in that: The water content in the ethanol-water solution in step (4) is 10-20%.

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