A method for preparing radial porous silica microspheres with adjustable core-shell ratio

Abstract

The application discloses a method for preparing radial porous silica microspheres with adjustable core-shell ratio, which comprises the following steps: adding a mixture of ethanol, water, a surfactant and a catalyst into a reaction container, adding a silicon source into the mixture under high-speed stirring, adding an organic solvent into the mixed solution at different intervals, reacting for several hours, washing and drying the obtained microspheres, and calcining the microspheres to remove a template, so as to obtain radial porous silica microspheres with adjustable core-shell ratio and good monodispersity. The method can be used to prepare the silica porous microspheres with the core-shell structure and the adjustable core-shell ratio, and the obtained porous silica microspheres have extremely important application values in biological drug loading, adsorption separation and energy catalysis.

Description

Technical Field

[0001] This invention relates to the field of silica microsphere preparation, specifically to a method for preparing radial porous silica microspheres with an adjustable core-shell ratio. Background Technology

[0002] Mesoporous silica microspheres possess a variety of excellent properties, including high specific surface area, large pore size, stable physicochemical properties, and easy surface functionalization, making them attractive for applications in biopharmaceutical delivery, adsorption separation, and energy catalysis.

[0003] In recent years, many researchers have begun to study core-shell structured silica microspheres. Shen Dengke (Nano Letters, Biphase Stratification Approach to Three-Dimensional Dendritic Biodegradable Mesoporous Silica Nanospheres[J], 2014, 14(2): 923-32.) et al. synthesized three-dimensional dendritic silica microspheres with a core-shell structure using an oil-water two-phase layering method, and the pore size can be adjusted by changing different hydrophobic solvents. Chinese Patent Application No. 202211703874.4 discloses a method for preparing monodisperse silica core-shell microspheres using a dual-template method. This method first uses a template to prepare solid silica microspheres, and then uses a porous template to generate a shell layer on their surface. However, the current synthesis of silica microspheres with a core-shell structure involves complex steps for controlling the pore size, and the amount of organic solvent used is large or cannot be adjusted, which limits the specific applications of silica microspheres. Summary of the Invention

[0004] This invention provides a method for preparing radial porous silica microspheres with an adjustable core-shell ratio. The core-shell ratio, pore size, and specific surface area of ​​the prepared silica microspheres can be controlled by changing the time interval between adding the silicon source and the organic solvent. The specific surface area of ​​the prepared silica microspheres gradually increases with the increase of time T1, and the pore size gradually decreases with the increase of time T1.

[0005] This invention provides a method for preparing radially porous silica microspheres with an adjustable core-shell ratio, the specific steps of which are as follows:

[0006] Step 1: After the surfactant is completely dissolved by high-speed stirring in a mixed solution of water, alcohol and catalyst, the silicon source is added to the above solution to obtain mixture A;

[0007] Step 2: After a certain time T1 following the addition of the silicon source, an organic solvent is added to the resulting mixture A. After high-speed stirring for a period of time T2, the product is centrifuged, washed, freeze-dried, and calcined to obtain silica microspheres with a core-shell structure and radial porous structure. The core-shell ratio of the silica microspheres is controlled by changing the time T1, and the core-shell ratio increases with the increase of time T1.

[0008] As a preferred embodiment of the present invention, in step 1, the added surfactant is one of the quaternary ammonium salts such as hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and hexadecyltrimethylammonium chloride (CTAC), and the surfactant accounts for 0.1-0.9% of the mass percentage in mixture A. The alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol, and the alcohol accounts for 30-40% of the volume percentage in mixture A.

[0009] As a preferred embodiment of the present invention, the catalyst in step 1 is one or more of ammonia, triethanolamine, triethylamine, and diethylamine, and the volume percentage of the catalyst in mixture A is 0.1-0.9%; the added silicon source is one of tetraethyl silicate, tetrapropyl silicate, silicon tetrachloride, silicon tetrafluoride, methyltrichloride, and sodium silicate, and the volume percentage of the silicon source in mixture A is 1-9%.

[0010] As a preferred embodiment of the present invention, in the first and second steps, the high-speed stirring speed is between 200-1000 r / min.

[0011] As a preferred embodiment of the present invention, in the second step, the organic solvent is one of toluene, xylene, trimethylbenzene, cyclohexane, n-hexane, cyclopentane, petroleum ether, and heptane, and the volume of the organic solvent added is 1%-9% of the volume of mixture A.

[0012] In a preferred embodiment of the present invention, in the second step, the time T1 is 0-360 min.

[0013] As a preferred embodiment of the present invention, the time T2 is 60-480 min.

[0014] As a preferred embodiment of the present invention, in the second step, calcination is carried out by raising the temperature to 500-800℃ at a heating rate of 4±3℃ / min and holding it at that temperature for 120-480min to remove the surfactant.

[0015] As a preferred embodiment of the present invention, the porous silica microspheres are radially arranged porous microspheres, and the size of the radial core can be adjusted by the time interval between the addition of the silicon source and the organic solvent. The core of the radially arranged porous silica microspheres accounts for 0%-100% of the total and is continuously adjustable. The core of the radially arranged porous silica microspheres has a small mesoporous structure, and the outer shell has a hierarchical mesoporous and macroporous structure. The particle size of the radially arranged porous silica microspheres is between 100nm and 1000nm.

[0016] This invention allows for the preparation of radially porous silica microspheres with varying core-shell ratios by adjusting the time interval between the addition of the silicon source and the organic solvent. The prepared silica microspheres have a core with a small mesoporous structure and a shell with a hierarchical mesoporous and macroporous structure. Due to their different pore sizes, the prepared silica microspheres exhibit unique advantages in drug loading and release. Attached Figure Description

[0017] Figure 1 This is a TEM image of the sample prepared in Example 1;

[0018] Figure 2 This is a TEM image of the sample prepared in Example 2;

[0019] Figure 3 This is a TEM image of the sample obtained in Example 3;

[0020] Figure 4 This is a TEM image of the sample prepared in Example 4;

[0021] Figure 5 This is a TEM image of the sample prepared in Example 5;

[0022] Figure 6 This is a TEM image of the sample prepared in Example 6. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0024] Example 1

[0025] Add 0.8 g CTAB and 0.6 mL ammonia to a mixed solution of 39.56 g ethanol and 80 g water. Stir mechanically at 700 rpm for 30 min at room temperature. Then add 3.0 mL of a mixed solution of TEOS and p-xylene (p-xylene addition time is 0 min). Continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in a muffle furnace under air atmosphere, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0026] The above steps yield radially porous silica microspheres with an adjustable core-shell ratio, whose morphology is as follows: Figure 1 As shown, the specific surface area of ​​BET is 543.18 m². 2 g -1 The average pore diameter is 5.66 nm, and the volume occupied by micropores is 21.54%.

[0027] Example 2

[0028] Add 0.8 g CTAB and 0.6 mL ammonia to a mixed solution of 39.56 g ethanol and 80 g water. Stir mechanically at 700 rpm for 30 min at room temperature, then add 3.0 mL TEOS solution. After 4 min, add 4.0 mL p-xylene solution, and continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in an air atmosphere in a muffle furnace, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0029] The above steps yield radially porous silica microspheres with an adjustable core-shell ratio, whose morphology is as follows: Figure 2 As shown, the specific surface area of ​​BET is 749.10 m². 2 g -1 The average pore diameter is 4.84 nm, and the volume occupied by micropores is 23.40%. Figure 2 The core and shell of the porous silica microspheres shown are continuous and without boundary, and each large mesopore in the shell layer is connected to the small mesopore in the core layer, and the pore wall of the large mesopore is continuous and without boundary with the pore wall of the small mesopore.

[0030] Example 3

[0031] Add 0.8 g CTAB and 0.6 mL ammonia to a mixed solution of 39.56 g ethanol and 80 g water. Stir mechanically at 700 rpm for 30 min at room temperature, then add 3.0 mL TEOS solution. After 16 min, add 4.0 mL p-xylene solution, and continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in an air atmosphere in a muffle furnace, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0032] The above steps yield radially porous silica microspheres with an adjustable core-shell ratio, whose morphology is as follows: Figure 3 As shown, the specific surface area of ​​BET is 800.34 m². 2 g -1 The average pore diameter is 3.48 nm, and the volume occupied by micropores is 46.50%. Figure 3 The core and shell of the porous silica microspheres shown are continuous and without boundary, and each large mesopore in the shell layer is connected to the small mesopore in the core layer, and the pore wall of the large mesopore is continuous and without boundary with the pore wall of the small mesopore.

[0033] Example 4

[0034] To a mixture of 39.56 g ethanol and 80 g water, add 0.8 g CTAB and 0.6 mL ammonia. Stir mechanically at 700 rpm for 30 min at room temperature, then add 3.0 mL TEOS solution. After 32 min, add 4.0 mL p-xylene solution, and continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in a muffle furnace under air atmosphere, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0035] The above steps yield radially porous silica microspheres with an adjustable core-shell ratio, whose morphology is as follows: Figure 4 As shown, the specific surface area of ​​BET is 789.51 m². 2 g -1 The average pore diameter is 3.19 nm, and the volume occupied by micropores is 51.02%. Figure 4 The core and shell of the porous silica microspheres shown are continuous and without boundary, and each large mesopore in the shell layer is connected to the small mesopore in the core layer, and the pore wall of the large mesopore is continuous and without boundary with the pore wall of the small mesopore.

[0036] Example 5

[0037] To a mixture of 39.56 g ethanol and 80 g water, add 0.8 g CTAB and 0.6 mL ammonia. Stir mechanically at 700 rpm for 30 min at room temperature, then add 3.0 mL TEOS solution. After 60 min, add 4.0 mL p-xylene solution, and continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in a muffle furnace under air atmosphere, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0038] The above steps yield radially porous silica microspheres with an adjustable core-shell ratio, whose morphology is as follows: Figure 5 As shown, the specific surface area of ​​BET is 790.57 m². 2 g -1 The average pore diameter is 2.63 nm, and the volume occupied by micropores is 60.47%.

[0039] Example 6

[0040] Add 0.8 g CTAB and 0.6 mL ammonia to a mixed solution of 39.56 g ethanol and 80 g water. Stir mechanically at 700 rpm for 30 min at room temperature, then add 3.0 mL TEOS solution and continue stirring mechanically at room temperature for 2 h. Centrifuge, wash, and freeze-dry the reacted solution. Then calcine the dried sample in an air atmosphere in a muffle furnace, heating to 600 °C at 1.5 °C / min and holding for 4 h, then cooling to room temperature.

[0041] The above steps did not yield core-shell structured silica microspheres; their morphology is as follows. Figure 6 As shown, the specific surface area of ​​BET is 912.09 m². 2 g -1 The average pore diameter is 2.28 nm, and the volume occupied by micropores is 71.37%.

[0042] In summary, the porous silica microspheres obtained by this invention are radially arranged porous microspheres, and the size of the radial core can be adjusted by the time interval between the addition of the silicon source and the organic solvent. The core of the radially arranged porous silica microspheres accounts for 0%-100% of the total and is continuously adjustable. The core of the radially arranged porous silica microspheres has a small mesoporous structure, and the outer shell has a hierarchical mesoporous and macroporous structure. The particle size of the radially arranged porous silica microspheres is between 100nm and 1000nm.

[0043] The above embodiments are used to explain and illustrate the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims

1. A method for the tunable control of the core-shell ratio of radially porous silica microspheres, characterized in that, Includes the following steps: Step 1: After the surfactant is completely dissolved by high-speed stirring in a mixed solution of water, alcohol, and catalyst, the silicon source is added to the solution to obtain mixture A. The surfactant is one of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and hexadecyltrimethylammonium chloride (CTAC), and the mass percentage of the surfactant in mixture A is 0.1-0.9%. The alcohol is one of methanol, ethanol, ethylene glycol, and isopropanol, and the volume percentage of the alcohol in mixture A is 30-40%. The catalyst is one or more of ammonia, triethanolamine, triethylamine, and diethylamine, and the volume percentage of the catalyst in mixture A is 0.1-0.9%. The silicon source is one of tetraethyl silicate, tetrapropyl silicate, silicon tetrachloride, silicon tetrafluoride, methyltrichlorosilane, and sodium silicate, and the volume percentage of the silicon source in mixture A is 1-9%. Step 2: After a certain time T1 following the addition of the silicon source, an organic solvent is added to the resulting mixture A. After high-speed stirring for a period of time T2, the product is centrifuged, washed, freeze-dried, and calcined to obtain radially porous silica microspheres with a core-shell structure. The core-shell ratio of the silica microspheres is controlled by changing the time T1, and the core-shell ratio increases with the increase of time T1. The time T1 is 0-360 min, and the time T2 is 60-480 min. With the increase of time T1, the core-shell ratio of the prepared silica microspheres gradually increases, and the average pore size of the porous silica microspheres gradually decreases with the increase of time T1. The porous silica microspheres are radially arranged, and the size of the radial core is adjusted by the time interval between adding the silicon source and the organic solvent. The core of the radially arranged porous silica microspheres accounts for 0%-100% of the total and is continuously adjustable. The core of the radially arranged porous silica microspheres has a small mesoporous structure, and the outer shell has a hierarchical mesoporous and macroporous structure. The particle size of the radially arranged porous silica microspheres is between 100 nm and 1000 nm. The core and shell of the porous silica microspheres are continuous and without boundary, and each large mesopore in the shell layer is connected to the small mesopore in the core layer, and the pore wall of the large mesopore is continuous and without boundary with the pore wall of the small mesopore.

2. The method of claim 1, wherein, The high-speed stirring speed in the first and second steps is between 200-1000 r / min.

3. The method of claim 1, wherein, In the second step, the organic solvent is one of toluene, xylene, trimethylbenzene, cyclohexane, n-hexane, cyclopentane, petroleum ether, and heptane, and the volume of the organic solvent added is 1%-9% of the volume of mixture A.

4. The method of claim 1, wherein, In the second step, calcination is carried out by raising the temperature to 500-800 °C at a rate of 4±3 °C / min and holding it for 120-480 min to remove the surfactant.

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