Preparation method of a double mesoporous silica nanosphere

Abstract

The present invention relates to a method for preparing double mesoporous silica nanospheres, comprising the following steps: (1) Dissolve a cationic surfactant in water to form a homogeneous solution, then add an alkanolamine catalyst and stir well to obtain a mixed solution; dissolve a silicon source in an organic solvent and drop it onto the above mixed solution to form an upper oil phase; (2) React the two-phase layered system obtained in step (1) at 40-80 °C for 6-12 h to obtain mesoporous silica nanospheres; (3) Inject a second catalyst into the lower aqueous phase and continue to react for 12-18 hours, and after the reaction is completed, centrifuge and separate; (4) Disperse the product obtained in step (3) into an ethanol-aqueous solution, reflux and extract the surfactant, and after the reaction is completed, centrifuge and separate to obtain double mesoporous silica nanospheres. The preparation process of the present invention has strong controllability, simple process, convenient operation and low cost, and has good application prospects.

Description

Technical Field

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

[0002] In recent years, constructing porous materials with hierarchical pore structures, such as macroporous-mesoporous, mesoporous-microporous, etc., can endow the materials with more excellent properties, so they have attracted the attention of researchers. The research on the hierarchical pore structure of mesoporous-mesoporous has also gradually emerged. Because different mesoporous structures can increase the specific surface area of the material, can contact and interact with more guest molecules, and at the same time can increase the rapid diffusion of guest molecules inside the pores. This characteristic will surely promote the application of double mesoporous materials in the fields of adsorption, catalysis, sensing, and biomedicine. Among them, the preparation of spherical double mesoporous materials with ultra-small particle sizes has attracted much attention, mainly because the spherical morphology has the lowest surface energy, and at the same time the ultra-small particle size ensures that the mesoporous material can be absorbed by cells to realize the transportation of drug molecules.

[0003] At present, there are not many preparations for synthesizing double mesoporous silica. Among them, the double-template method is the most common. This method requires two different types of surfactants, and the solvent is volatilized to form two stable, independent and different-sized micelles, and then the hydrolysis products of two different types and sizes of micelles and silica precursors are co-assembled. This method requires the cooperation of solvent volatilization, so the cost is relatively high, and the obtained 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 general method for preparing double mesoporous silica nanospheres at present. It utilizes the pore-expanding effect of the upper oil phase, and the type of the upper oil phase is replaced at a certain stage of the reaction to realize the change of the pore size in the subsequent reaction. Therefore, it is the simplest method to operate at present, but the replacement of its upper oil phase greatly increases the cost. Therefore, it is of great significance to develop a simple synthesis method to prepare silica nanospheres with a double mesoporous structure. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of double mesoporous silica nanospheres, which has strong controllability in the preparation process, is simple, convenient to operate, has low cost, and has good application prospects.

[0006] The present invention provides a preparation method of double mesoporous silica nanospheres, comprising the following steps:

[0007] (1) Dissolve the template agent in water to form a uniform solution, then add an alkanolamine catalyst and stir well to obtain a mixed solution; dissolve the silicon source in an organic solvent and drop it onto the above mixed solution to form an upper oil phase;

[0008] (2) React the two-phase layered system obtained in step (1) at 40 - 80 °C for 6 - 12 h to obtain mesoporous silica nanospheres;

[0009] (3) Inject a second catalyst into the lower aqueous phase and continue the reaction for 12 - 18 hours. After the reaction is completed, perform centrifugal separation;

[0010] (4) Disperse the product obtained in step (3) into an ethanol - aqueous solution, reflux to extract the template agent, and perform centrifugal separation after the reaction is completed to obtain double - mesoporous silica nanospheres.

[0011] Preferably, the template agent in step (1) is a quaternary ammonium salt cationic surfactant, and its concentration in the homogeneous solution is 5 - 15 wt%.

[0012] Preferably, the alkanolamine catalyst in step (1) is ethanolamine; the mass ratio of the alkanolamine catalyst to the silicon source is 0.01 - 0.12:1.

[0013] Preferably, the silicon source in step (1) is selected from one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

[0014] Preferably, the organic solvent in step (1) is selected from one or more of cyclohexane, n - hexane, decalin, and olefins.

[0015] Preferably, the second catalyst in step (3) is ethylenediamine; the mass ratio of the second catalyst to the alkanolamine catalyst is 0.05 - 0.25:1.

[0016] Preferably, the water content in the ethanol - aqueous solution in step (4) is 10 - 20%.

[0017] Beneficial effects

[0018] (1) In the present invention, ethylenediamine with extremely strong alkalinity is used as the catalyst in the second stage. Since ethylenediamine is more likely to etch the silica structure than alkanolamine, the silica components grown in the second stage can be selectively etched during hydrothermal treatment to obtain a double - mesoporous structure.

[0019] (2) In the present invention, an ethanol - water reflux system is adopted to achieve a double - mesoporous structure.

[0020] (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 forms of the silica synthesized twice are different: the silica synthesized in the first step contains alkanolamine inside, and the silica synthesized in the second step contains ethylenediamine and alkanolamine inside. Therefore, during the high-temperature reflux treatment, ethylenediamine can easily etch part of the silica component to obtain a monodisperse double-mesoporous silica nanosphere material. Description of the Drawings

[0021] Figure 1 It is the characteristic transmission electron microscope (TEM) image of the double-mesoporous silica nanospheres in Example 1.

[0022] Figure 2 It is the pore size distribution diagram of the double-mesoporous silica nanospheres in Example 1.

[0023] Figure 3 It is the characteristic transmission electron microscope (TEM) image of the double-mesoporous silica nanospheres in Example 2.

[0024] Figure 4 It is the pore size distribution diagram of the double-mesoporous silica nanospheres in Example 2.

[0025] Figure 5 It is the characteristic transmission electron microscope (TEM) images of the mesoporous silica nanospheres obtained in Comparative Example 1 (adding excessive ethylenediamine) before (a) and after (b) the reflux extraction.

[0026] Figure 6 It is the characteristic transmission electron microscope (TEM) image of the mesoporous silica nanospheres obtained in Comparative Example 2 (without adding ethylenediamine). Detailed Description of the Invention

[0027] 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 not 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 also fall within the scope defined by the appended claims of this application.

[0028] Example 1

[0029] (1) Dissolve 3.0 g of cetyltrimethylammonium bromide and 0.10 g of monoethanolamine in 60 mL of deionized water, control the oil bath temperature at 40 °C, and carry out gentle stirring to form a colorless and transparent solution. Carefully add 20 mL of a cyclohexane solution of 30% TEOS dropwise to the above solution. The stirring speed should be such that the lower aqueous phase is stirred while the oil phase is basically stationary, and react for 12 hours under this stable condition.

[0030] (2) Inject 0.01 g of ethylenediamine into the lower aqueous phase with a syringe, continue the reaction for 12 hours. After the reaction is completed, centrifuge at high speed (12000 rpm, 5 min) for centrifugal separation.

[0031] (3) The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 48 mL of ethanol and 12 mL of water, and the oil bath temperature is 100 °C for reflux extraction of the surfactant. After the reaction is completed, centrifuge for separation to obtain the double mesoporous silica nanosphere material, and its TEM image is as Figure 1 shown.

[0032] The prepared mesoporous silica nanospheres significantly exhibit different particle size distributions, as Figure 2 shown. The pore diameter of the inner spheres is relatively small, about 5.8 nm, and its particle size is about 160 nm. The mesoporous channels of the outer layer are significantly larger, about 11.3 nm, with a thickness of about 25 nm, and the overall particle size is about 210 nm.

[0033] Example 2

[0034] (1) Dissolve 9.0 g of cetyltrimethylammonium chloride and 0.3 g of triethanolamine in 60 mL of deionized water, control the oil bath temperature at 75 °C, and carry out gentle stirring to form a colorless and transparent solution. Carefully add 20 mL of a decalin solution of 15% TEOS dropwise to the above solution. The stirring speed should be such that the lower aqueous phase is stirred while the oil phase is basically stationary, and react for 6 hours under this stable condition.

[0035] (2) Inject 0.06 g of ethylenediamine into the lower aqueous phase with a syringe, continue the reaction for 12 hours. After the reaction is completed, centrifuge at high speed (12000 rpm, 5 min) for centrifugal separation.

[0036] (3) The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 54 mL of ethanol and 6 mL of water, and the oil bath temperature is 60 °C for reflux extraction of the surfactant. After the reaction is completed, centrifuge for separation to obtain the double mesoporous silica nanosphere material, and its TEM image is as Figure 3 shown.

[0037] The prepared mesoporous silica nanospheres significantly exhibit two different particle size distributions as Figure 4As shown, the inner sphere has a smaller pore diameter, about 6.7 nm, and its particle size is about 160 nm. The outer mesoporous channels are significantly larger, about 13.7 nm, with a thickness of about 20 nm, and the overall particle size is about 200 nm.

[0038] Comparative Example 1

[0039] (1) Dissolve 3.0 g of cetyltrimethylammonium bromide and 0.10 g of ethanolamine in 60 mL of deionized water, control the oil bath temperature at 40°C, and perform gentle stirring to form a colorless transparent solution. Carefully add 20 mL of a cyclohexane solution of 30% TEOS to the above solution, and the stirring speed should be such that the lower aqueous phase is stirred while the oil phase remains basically stationary, and react under this stable condition for 12 hours.

[0040] (2) Inject 0.10 g of ethylenediamine into the lower aqueous phase with a syringe, continue the reaction for 12 hours, and after the reaction, perform high-speed centrifugation (12000 rpm, 5 min) for centrifugal separation.

[0041] (3) The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 48 mL of ethanol and 12 mL of water, and the oil bath temperature is 100°C for reflux extraction of the surfactant. After the reaction, perform centrifugal separation to obtain the mesoporous silica nanosphere material.

[0042] The mesoporous silica nanospheres prepared above, as Figure 5 shown, had a particle size of about 210 nm before reflux extraction, with a relatively smooth surface, a relatively small pore diameter, and clearly presented a set of mesoporous structures. After reflux extraction, the pore diameter of the spheres decreased to about 170 nm, and at the same time, the surface was significantly very disordered, indicating that during the reflux extraction stage, excessive ethylenediamine would completely etch the outer mesopores.

[0043] Comparative Example 2

[0044] (1) Dissolve 3.0 g of cetyltrimethylammonium bromide and 0.10 g of monoethanolamine in 60 mL of deionized water, control the oil bath temperature at 40°C, and perform gentle stirring to form a colorless transparent solution. Carefully add 20 mL of a cyclohexane solution of 30% TEOS to the above solution, and the stirring speed should be such that the lower aqueous phase is stirred while the oil phase remains basically stationary, and react under this stable condition for 12 hours.

[0045] (2) Continue the reaction for 12 hours, and after the reaction, perform high-speed centrifugation (12000 rpm, 5 min) for centrifugal separation.

[0046] (3)The silica sphere material produced in step (2) is ultrasonically dispersed in a mixed solution of 48 mL of ethanol and 12 mL of water, and the surfactant is refluxed and extracted at an oil bath temperature of 100 °C. After the reaction, centrifugal separation is carried out to obtain a mesoporous silica nanosphere material.

[0047] The mesoporous silica nanospheres prepared above obviously exhibit a set of mesoporous structures, such as Figure 6 shown. The pore diameter of the sphere is about 170 nm, indicating that without the addition of ethylenediamine, with the increase of the reaction time, neither its particle size nor its pore diameter changes significantly, 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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