A method for regulating the particle size and pore size of dendritic channel structure mesoporous silica particles

Abstract

The application belongs to the technical field of nanometer material synthesis, and particularly relates to a method for regulating the particle size and pore size of dendritic mesoporous silica particles. The dendritic mesoporous silica is prepared by adopting a two-phase stratification method, surfactant and alkaline catalyst are added as the water phase, cyclohexane and TEOS are added as the oil phase, a self-assembly reaction occurs at the two-phase interface, the surfactant in the pore is removed by a solvent extraction method, the volume ratio of the oil phase and the water phase and the volume proportion of TEOS in the oil are regulated, and dendritic mesoporous silica with specific particle size, different pore sizes or specific pore size, different particle sizes is prepared. The prepared mesoporous silica has a particle size of 50-300 nm and a pore size of 2-15 nm. The application has simple operation, and the prepared mesoporous silica has uniform particle size, good dispersity and high stability, and provides a new idea for preparing spherical dendritic mesoporous silica with adjustable particle size and pore size.

Description

Technical Field

[0001] This invention relates to a method for controlling the particle size and pore size of dendritic mesoporous silica nanoparticles, belonging to the field of nanomaterial synthesis technology. Background Technology

[0002] In recent years, dendritic mesoporous silica has attracted widespread attention. Compared with traditional silica nanoparticles, dendritic silica nanomaterials not only possess a three-dimensional dendritic framework and a large central radial emission mesoporous structure, but also exhibit varied pore surface structures, larger specific surface area, and higher loading capacity, showing broad application prospects in catalysis, adsorption, and biomedicine. In 2010, Polshettiwar and colleagues first prepared dendritic silica fiber spheres (KCC-1) using microwave-assisted hydrothermal technology, sparking a research boom in dendritic mesoporous materials.

[0003] Currently, the main methods for preparing dendritic mesoporous silica nanoparticles include emulsion methods, sol-gel methods, and two-phase layering methods. In 2010, Du et al. synthesized dendritic macromolecular silica with radial macropores and mesopores in an ether / water emulsion system (10.1021 / la100196j). Zhang et al. used the sol-gel method, with hexadecyltrimethyl-p-toluenesulfonate ammonium salt (CTAB) as a template agent and small-molecule organic amines as catalysts, to synthesize monodisperse mesoporous silica with astral channels on a large scale (10.1002 / anie.201003451). In 2014, Zhao's group developed a heterogeneous oil-water two-phase layering reaction system (10.1021 / nl404316v) and synthesized multilayer DMSNs with a center-radial structure. TEOS is dispersed in the upper oil phase, while the surfactant (CTAC) and catalyst (TEA) are in the lower aqueous phase. The reactants self-assemble at the oil-water interface, achieving one-pot continuous interfacial growth. By changing the upper oil phase (1-octadecene, decahydronaphthalene, cyclohexane), the pore size varies from 2.8 to 13 nm, and the particle size of the nanoparticles can be controlled by adjusting the reaction time.

[0004] Precise control of the mesoscopic size of dendritic mesoporous silica (DMSNs) largely determines their physicochemical properties and application performance. In the two-phase layering method, the surfactant in the aqueous phase acts as a synthesis template, determining the size of the nanoparticles, while the organic solvent in the oil phase acts as a swelling agent, which is a key factor in the formation of mesoporous channels. Currently, a single control variable usually leads to simultaneous changes in particle size and pore size. Therefore, changing only the particle size or pore size to prepare DMSNs with specific particle sizes but different pore sizes or specific pore sizes but different particle sizes remains one of the challenges in the structural control of DMSNs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the two-phase layering method in that the specific particle size and pore size of dendritic mesoporous silica cannot be controlled, and to provide a new method for preparing dendritic mesoporous silica with specific particle size and pore size.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a method for controlling the particle size and pore size of mesoporous silica particles with a dendritic channel structure, the method comprising the following steps:

[0008] (1) An aqueous solution of hexadecyltrimethylammonium chloride (CTAC) was stabilized for a period of time by adding triethanolamine (TEA), and then stabilized for a period of time by adding cyclohexane. Finally, a mixture of cyclohexane and tetraethyl silicate (TEOS) was added to carry out a self-assembly reaction.

[0009] (2) After the reaction is complete, remove the upper oil phase, collect the lower emulsion, centrifuge and wash to obtain the preliminary product;

[0010] (3) CTAC in the initial product was removed by solvent extraction, and mesoporous silica nanoparticles with dendritic pore structure were obtained after multiple centrifugations and washing.

[0011] Among them, by separately controlling the volume ratio of the aqueous phase and the oil phase, particles with specific pore sizes and different particle sizes can be prepared; by separately controlling the volume ratio of TEOS in the oil phase, particles with specific particle sizes and different pore sizes can be prepared.

[0012] The aqueous phase is an aqueous solution of hexadecyltrimethylammonium chloride, and the oil phase is cyclohexane and tetraethyl silicate.

[0013] In the above technical solution, the volume ratio of the aqueous phase to the oil phase is further adjusted to 1:5 to 5:1. The organic solvent, acting as a swelling agent, can assemble with the surfactant at the interface, inducing the formation of oil-water semi-emulsion micelles with interfacial curvature. The particle size can be controlled by adjusting the oil-water ratio.

[0014] In the above technical solution, further, by increasing the volume of the oil phase alone, the pore size of the silica particles remains unchanged, but the particle size increases.

[0015] In the above technical solution, the volume percentage of TEOS in the oil phase is further adjusted to 10% to 30% (v / v).

[0016] In the above technical solution, further increasing the volume percentage of TEOS in the oil phase results in unchanged particle size but reduced pore size of silica particles. As a silicon source, TEOS directly determines the mesoporous assembly of nanoparticles. The lower the TEOS content, the fewer nucleations and hydrolysis products are produced, leading to an increase in pore size.

[0017] In the above technical solution, the particle size of the mesoporous silica nanoparticles with the dendritic channel structure is controllable in the range of 50 to 300 nm, and the pore size is adjustable in the range of 2 to 15 nm.

[0018] In the above technical solution, the concentration of the aqueous solution of CTAC in step (1) is 5-10 mg / mL; the concentration of TEA in the aqueous solution of CTAC is 2-4 mg / mL. Under these conditions, the concentration of CTAC exceeds its critical micelle concentration, and a stable layered mesophase can be formed in the aqueous phase. The additional CTAC molecules can be used to reduce the surface tension between the aqueous and organic phases. TEA, as a catalyst, can provide a weakly alkaline environment for the reaction system, resulting in higher catalytic efficiency and promoting the hydrolysis-condensation reaction of the silicon source to obtain spherical silica with better morphology and a certain regular pore structure.

[0019] In the above technical solution, the self-assembly reaction in step (1) is carried out at 60-70℃ and 100-200rpm for 4-12h. The reaction temperature, rotation speed and time will affect the reaction rate. The change in reaction rate will eventually affect the morphology of the mesoporous structure. At the above reaction temperature, rotation speed and time, spherical dendritic mesoporous silica nanoparticles with ideal morphology, uniform dispersion and stable structure can be obtained.

[0020] In step (1), triethanolamine (TEA) was added for 0.5-1 h for stabilization; cyclohexane was added for 0.5-1 h for stabilization.

[0021] In the above technical solution, the solvent used for washing in step (2) is anhydrous ethanol to remove CTAC; preferably, the volume ratio of the initial reaction product to anhydrous ethanol can be 1:1.

[0022] In the above technical solution, further, the solvent used in step (3) of the extraction method is a 5-10 mg / mL ammonium nitrate ethanol solution, refluxed at 60-70℃ and 400-600 rpm for 6-8 hours, 3-4 times. Solvent extraction is more advantageous than calcination for completely removing CTAC from the mesoporous channels, as it can retain more silanol groups, and the pore framework shrinkage is not significant after template extraction.

[0023] The present invention also provides the application of the aforementioned method or mesoporous silica particles obtained by the aforementioned method in the preparation of catalyst materials, adsorbent materials or drug delivery carrier materials.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention employs a two-phase layering method to prepare dendritic mesoporous silica. A surfactant and alkaline catalyst are added as the aqueous phase, while cyclohexane and TEOS are added as the organic phase. A self-assembly reaction occurs at the interface between the two phases. The effects of reaction temperature, reaction speed, and reaction time on the mesoporous silica framework are analyzed. By selecting appropriate reaction conditions and rationally controlling the oil-to-water ratio and the volume ratio of TEOS in the oil phase, the pore structure and particle size of the mesoporous silica can be synergistically controlled, resulting in monodisperse dendritic mesoporous silica nanoparticles with specific particle and pore sizes. This allows for the individual modification of either the particle size or the pore size.

[0026] The method provided by this invention has simple control means, high reaction yield, and high stability, and provides ideas for formulating mesoporous silica with specific particle size, different pore size, or specific pore size and different particle size. Attached Figure Description

[0027] Figure 1 TEM images and pore size distributions of dendritic mesoporous silica with the same pore size but different particle sizes: a. TEM image of 50 nm particle size and 6 nm pore size; b. TEM image of 100 nm particle size and 6 nm pore size; c. TEM image of 150 nm particle size and 6 nm pore size; d. Pore size distributions of Examples 1-3.

[0028] Figure 2 TEM images and pore size distributions of dendritic mesoporous silica with the same particle size but different pore sizes: a. TEM image of 100 nm particle size and 9 nm pore size; b. TEM image of 100 nm particle size and 11 nm pore size; c. Pore size distributions of Examples 2, 4, and 5.

[0029] Figure 3 Nitrogen adsorption-desorption curves of DMSNs with the same pore size but different particle sizes in Examples 1-3.

[0030] Figure 4 Examples 2, 4, and 5: nitrogen adsorption-desorption curves with the same particle size but different pore sizes.

[0031] Figure 5 Example 2: Stability of DMSNs in water and PBS buffer. Specific implementation methods

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Example 1

[0034] 6 g of CTAC was placed in a flask, and 60 mL of deionized water was added to dissolve it. Then, 180 mg of TEA was added, and the mixture was stabilized at 70 °C and 400 rpm for 1 h. Next, 6 mL of preheated cyclohexane was added, and the mixture was stabilized for 30 min. Then, a preheated mixture of 2.4 mL of cyclohexane and 3.6 mL of TEOS was added dropwise along the flask wall, and the reaction was carried out at 70 °C and 200 rpm for 12 h. After the reaction was complete, the upper oil phase was carefully removed. The lower emulsion was centrifuged and washed several times with anhydrous ethanol to initially remove surfactants from the mesoporous channels. The preliminary product was placed in 80 mL of ammonium nitrate ethanol solution (5 mg / mL) and refluxed at 60 °C for 18 h to remove residual CTAC from the channels as completely as possible. The final product was obtained after multiple centrifugations and washing with water and ethanol to obtain dendritic mesoporous silica.

[0035] This embodiment yields dendritic mesoporous silica with a particle size of 50 nm and a pore size of 6 nm. Figure 1 a).

[0036] Example 2

[0037] 6 g of CTAC was placed in a flask, and 60 mL of deionized water was added to dissolve it. Then, 180 mg of TEA was added, and the mixture was stabilized at 70 °C and 400 rpm for 1 h. Next, 10 mL of preheated cyclohexane was added, and the mixture was stabilized for 30 min. Then, a preheated mixture of 4 mL of cyclohexane and 6 mL of TEOS was added dropwise along the flask wall, and the reaction was carried out at 70 °C and 200 rpm for 12 h. After the reaction was complete, the upper oil phase was carefully removed. The lower emulsion was centrifuged and washed several times with anhydrous ethanol to initially remove surfactants from the mesoporous channels. The preliminary product was placed in 80 mL of ammonium nitrate ethanol solution (5 mg / mL) and refluxed at 60 °C for 18 h to remove residual CTAC from the channels as completely as possible. The final product was obtained after multiple centrifugations and washing with water and ethanol to obtain dendritic mesoporous silica.

[0038] This embodiment yields dendritic mesoporous silica with a particle size of 100 nm and a pore size of 6 nm. Figure 1 b).

[0039] Stability analysis: 10 mg of DMSNs sample was added to two glass bottles, and 2 mL of deionized water and PBS buffer were added to each. After sonication for 5 min, the samples were allowed to stand at room temperature for 2 h. The dispersion of DMSNs in different dispersion solutions was compared by taking pictures. After 2 h, no obvious aggregation was observed in either suspension, indicating that the DMSNs synthesized in this example have good dispersion stability in both water and PBS buffer. Figure 5 ).

[0040] Example 3

[0041] 6 g of CTAC was placed in a flask, and 60 mL of deionized water was added to dissolve it. Then, 180 mg of TEA was added, and the mixture was stabilized at 70 °C and 400 rpm for 1 h. Next, 30 mL of preheated cyclohexane was added, and the mixture was stabilized for 30 min. Then, a preheated mixture of 12 mL of cyclohexane and 18 mL of TEOS was added dropwise along the flask wall, and the reaction was continued at 70 °C and 200 rpm for 12 h. After the reaction was complete, the upper oil phase was carefully removed. The lower emulsion was centrifuged and washed several times with anhydrous ethanol to initially remove surfactants from the mesoporous channels. The preliminary product was placed in 80 mL of ammonium nitrate ethanol solution (5 mg / mL) and refluxed at 60 °C for 18 h to remove residual CTAC from the channels as completely as possible. The final product was obtained after multiple centrifugations and washing with water and ethanol to obtain dendritic mesoporous silica.

[0042] This embodiment yields dendritic mesoporous silica with a particle size of 150 nm and a pore size of 6 nm. Figure 1 c).

[0043] As can be seen from Examples 1, 2, and 3, by simply changing the ratio of the oil phase to the water phase without changing the proportion of TEOS in the oil phase, it is possible to change the particle size without changing the pore size. In Example 1, the volume ratio of the oil phase (cyclohexane, TEOS) to the water phase (CTAC aqueous solution) was changed from 1:5 to 1:3 in Example 2 or 1:1 in Example 3, respectively. The pore size of 6nm remained unchanged, while the particle size increased from 50nm to 100nm and 150nm, respectively. Figure 1 d).

[0044] Example 4

[0045] 6 g of CTAC was placed in a flask, and 60 mL of deionized water was added to dissolve it. Then, 180 mg of TEA was added, and the mixture was stabilized at 70 °C and 400 rpm for 1 h. Next, 10 mL of preheated cyclohexane was added, and the mixture was stabilized for 30 min. Then, a preheated mixture of 6 mL of cyclohexane and 4 mL of TEOS was added dropwise along the flask wall, and the reaction was continued at 70 °C and 200 rpm for 12 h. After the reaction was complete, the upper oil phase was carefully removed. The lower emulsion was centrifuged and washed several times with anhydrous ethanol to initially remove surfactants from the mesoporous channels. The preliminary product was placed in 80 mL of ammonium nitrate ethanol solution (5 mg / mL) and refluxed at 60 °C for 18 h to remove residual CTAC from the channels as completely as possible. The final product was obtained after multiple centrifugations and washing with water and ethanol to obtain dendritic mesoporous silica.

[0046] This embodiment yields dendritic mesoporous silica with a particle size of 100 nm and a pore size of 9 nm. Figure 2 a).

[0047] Example 5

[0048] 6 g of CTAC was placed in a flask, and 60 mL of deionized water was added to dissolve it. Then, 180 mg of TEA was added, and the mixture was stabilized at 70 °C and 400 rpm for 1 h. Next, 10 mL of preheated cyclohexane was added, and the mixture was stabilized for 30 min. Then, a preheated mixture of 8 mL of cyclohexane and 2 mL of TEOS was added dropwise along the flask wall, and the reaction was carried out at 70 °C and 200 rpm for 12 h. After the reaction was complete, the upper oil phase was carefully removed. The lower emulsion was centrifuged and washed several times with anhydrous ethanol to initially remove surfactants from the mesoporous channels. The preliminary product was placed in 80 mL of ammonium nitrate ethanol solution (5 mg / mL) and refluxed at 60 °C for 18 h to remove residual CTAC from the channels as completely as possible. The final product was obtained after multiple centrifugations and washing with water and ethanol to obtain dendritic mesoporous silica.

[0049] This embodiment yields dendritic mesoporous silica with a particle size of 100 nm and a pore size of 11 nm. Figure 2 b).

[0050] As can be seen from Examples 2, 4, and 5, by changing only the proportion of TEOS in the oil phase without changing the ratio of oil to water, it is possible to change the pore size without changing the particle size. In Example 2, the volume ratio of the oil phase (cyclohexane, TEOS) to the water phase (CTAC aqueous solution) remained unchanged. The proportion of TEOS in the oil phase decreased from 30% in Example 2 to 20% in Example 4 and 10% in Example 5, respectively. The particle size of 100 nm remained unchanged, but the pore size increased from 6 nm to 9 nm and 11 nm, respectively. Figure 2 c).

[0051] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for controlling the particle size and pore size of dendritic mesoporous silica particles, characterized in that, The method includes the following steps: (1) An aqueous solution of hexadecyltrimethylammonium chloride (CTAC) was stabilized for a period of time by adding triethanolamine (TEA), then stabilized for a period of time by adding cyclohexane, and then a mixture of cyclohexane and tetraethyl silicate (TEOS) was added to carry out a self-assembly reaction. (2) After the reaction is complete, the upper oil phase is removed, and the lower emulsion is collected, centrifuged, and washed to obtain the preliminary product; (3) CTAC in the initial product was removed by solvent extraction, and mesoporous silica nanoparticles with dendritic pore structure were obtained after multiple centrifugations and washing. Among them, by adjusting the volume ratio of the aqueous phase and the oil phase alone, only the ratio of the oil phase and the aqueous phase is changed without changing the proportion of TEOS in the oil phase, particles with specific pore sizes and different particle sizes can be prepared; by adjusting the volume proportion of TEOS in the oil phase alone, only the proportion of TEOS in the oil phase is changed without changing the ratio of the oil phase and the aqueous phase, particles with specific particle sizes and different pore sizes can be prepared. The aqueous phase is an aqueous solution of hexadecyltrimethylammonium chloride, and the oil phase is cyclohexane and tetraethyl silicate.

2. The method according to claim 1, characterized in that: The volume ratio of the aqueous phase to the oil phase is adjusted to 1:5 to 5:

1.

3. The method according to claim 1, characterized in that: Increasing the volume of the oil phase alone does not change the pore size of the silica particles, but increases their particle size.

4. The method according to claim 1, characterized in that: The volume fraction of TEOS in the oil phase was adjusted to 10% to 30% (v / v).

5. The method according to claim 1, characterized in that: Increasing the volume percentage of TEOS in the oil phase alone results in unchanged particle size but reduced pore size of silica particles.

6. The method according to claim 1, characterized in that: The mesoporous silica nanoparticles with the dendritic channel structure have a controllable particle size in the range of 50~300nm and an adjustable pore size in the range of 2~15nm.

7. The method according to claim 1, characterized in that: The concentration of CTAC in the aqueous solution in step (1) is 5~10 mg / mL; the concentration of TEA in the CTAC aqueous solution is 2~4 mg / mL.

8. The method according to claim 1, characterized in that: The self-assembly reaction in step (1) is carried out at 60-70℃ and 100-200rpm for 4-12 hours; In step (1), triethanolamine (TEA) was added for 0.5-1 h for stabilization; cyclohexane was added for 0.5-1 h for stabilization.

9. The method according to claim 1, characterized in that: The solvent used for washing in step (2) is anhydrous ethanol; The solvent used in step (3) of the extraction method is 5~10mg / mL ammonium nitrate ethanol solution, refluxed at 60~70℃ and 400-600rpm for 6-8h, 3-4 times.

10. The use of the method according to any one of claims 1 to 9 or the mesoporous silica particles obtained by the method according to any one of claims 1 to 9 in catalytic materials, adsorbent materials or drug delivery carrier materials.

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