Monodisperse spherical hollow silicon dioxide as well as preparation method and application thereof

Abstract

The invention discloses monodisperse spherical hollow silicon dioxide as well as a preparation method and application thereof. The method comprises the following steps: obtaining a mixed solution containing a template agent, a dispersing agent and a catalyst, and enabling the template agent to self-assemble and separate out a monodisperse spherical template; adding a silicon source for hydrolysis to form silicon dioxide on the surface of the template, and collecting a solid phase to obtain a precursor; and calcining to remove the template to obtain the monodisperse spherical hollow silicon dioxide. According to the preparation method, in-situ stability and size locking of the template are achieved through the steric hindrance effect of the dispersing agent, the technical problem that size uniformity and morphology regularity are difficult to consider at the same time is solved while the preparation process is simplified, and the obtained product is excellent in monodispersity and regular in sphere shape and has wide application prospects in the fields of drug delivery, photonic crystals and the like.

Description

Technical Field

[0001] This invention belongs to the field of silica synthesis technology, specifically relating to a monodisperse spherical hollow silica, its preparation method, and its applications. Background Technology

[0002] Hollow silica, due to its low density, large specific surface area, good biocompatibility, and the loading capacity of its hollow structure, shows broad application prospects in fields such as controlled drug release, photonic crystals, and energy storage. Ideally, hollow silica should possess a uniform particle size distribution and a regular spherical morphology to ensure the designability and reproducibility of material properties. Currently, the mainstream methods for preparing hollow silica are divided into hard template methods and soft template methods. Hard template methods (such as polystyrene and iron(III) oxide) require the pre-synthesis of rigid templates with uniform dimensions, a cumbersome and lengthy process; soft template methods (such as microemulsion methods and sol-gel methods) rely on thermodynamically unstable micelle assembly, have a narrow operating window, are extremely sensitive to reaction conditions, and are difficult to achieve batch stability in large-scale production.

[0003] To overcome these limitations, scholars have recently proposed "pseudo-hard template methods" or "templateless methods," attempting to directly form hollow structures by controlling the self-assembly behavior of precursors. However, in-depth research has revealed that due to a lack of precise control over the nucleation and aggregation processes, the hollow silica prepared by these methods often exhibits unpredictable multi-chamber, worm-like, or amorphous aggregate structures, with a wide particle size distribution and poor sphericity. This randomness and irregularity in structure directly leads to fundamental difficulties in its core application areas: In the field of precision drug delivery, the predictability of drug release behavior is a fundamental prerequisite for safe and effective clinical medication. Existing technologies for preparing multi-chamber hollow structures result in significant variations in drug loading due to inconsistent cavity volumes and shell thicknesses, and the release kinetics exhibit highly uncontrollable behavior (such as random burst release or incomplete release). For drugs with narrow therapeutic windows (such as nucleic acid drugs and protein drugs), this unpredictable release behavior can easily lead to toxic side effects or insufficient efficacy, failing to meet the stringent standards for clinical use. In the field of photonic crystals and optical sensing, multi-chamber and irregular particles cannot form a periodically arranged ordered structure, resulting in numerous defects during assembly, leading to the loss of structural color or optical signal straying, completely negating their application as high-sensitivity optical sensors or photonic devices.

[0004] Therefore, existing technologies that can only form "hollow" structures are insufficient to meet the core requirements of practical applications. The uncontrollable structure and irregular morphology lead to application failures, rendering these materials useless in scenarios requiring high performance and high consistency. Therefore, there is an urgent need for a hollow silica material and its preparation method that can simultaneously guarantee uniform single-size dimensions and a regular spherical morphology to solve this technical problem. Summary of the Invention

[0005] To address the technical problem of simplifying the preparation process in commonly used techniques, making it difficult to simultaneously achieve uniform size and regular spherical morphology in hollow silica, this invention provides a method for preparing monodisperse spherical hollow silica, comprising the following steps: A mixture containing a template agent, a dispersant, and a catalyst is obtained, wherein the concentration of the dispersant in the mixture is 1.5-4.5 g / L; the template agent self-assembles and precipitates monodisperse spherical templates under the action of the catalyst and the dispersant. A silicon source is added to the mixture, and the silicon source undergoes a hydrolysis reaction to form silicon dioxide on the surface of the monodisperse spherical template. After the hydrolysis reaction is completed, the solid phase is collected to obtain the precursor. The precursor is calcined to obtain the monodisperse spherical hollow silica.

[0006] Furthermore, the concentration of the template agent in the mixture is 0.0065-0.014 mol / L, and the concentration of the catalyst in the mixture is 0.55-0.9 mol / L.

[0007] Furthermore, the catalyst includes at least one of ammonia and sodium hydroxide; the template agent includes Basic Blue 7; and the dispersant includes polyvinylpyrrolidone.

[0008] Furthermore, the silicon source is added to the mixture in the form of a silicon source solution; the concentration of the silicon source in the silicon source solution is 0.10-0.55 mol / L; the silicon source includes fluorosilicic acid.

[0009] Furthermore, in the mixture system of the silicon source and the mixture, the concentration of the silicon source is 0.02-0.11 mol / L.

[0010] Furthermore, the hydrolysis reaction is carried out at a temperature of 40-90°C and for a duration of 2-8 hours.

[0011] Furthermore, the calcination temperature is 500-800℃, and the calcination time is 1-6 hours.

[0012] Furthermore, obtaining the mixture containing the template agent, dispersant, and catalyst includes: stirring the template agent, the dispersant, and the catalyst at a temperature of 30-80°C and a speed of 100-600 rpm for 5-30 minutes to obtain the mixture.

[0013] This invention provides a monodisperse spherical silica, prepared by the preparation method described above.

[0014] This invention provides an application of the monodisperse spherical silica described above in catalytic chemistry, optical materials, or precise drug delivery.

[0015] Compared with the prior art, the present invention has at least the following advantages: This invention provides a method for preparing monodisperse spherical hollow silica. Its core innovation lies in the simultaneous introduction of a polymeric dispersant and its steric hindrance effect during the self-assembly and precipitation of the template agent to form a spherical template, thereby achieving in-situ dispersion and size locking of the template during its formation process. This design overcomes the limitations of existing technologies that rely on "forming the template first and then attempting dispersion" or "relying solely on the template agent itself to regulate morphology," achieving precise in-situ intervention in the template nucleation and growth process.

[0016] Specifically: First, unlike existing technologies that rely solely on the self-assembly tendency of template agents and whose product morphology is easily affected by reaction conditions, resulting in a passive situation of multi-chamber or irregular aggregation, this invention utilizes the steric hindrance effect of dispersants to physically confine the template during the critical stage of template precipitation. This forces the template to grow along the spherical interface with the lowest energy, thereby actively constructing a template with a complete spherical morphology and fundamentally avoiding the generation of worm-like or amorphous aggregate structures.

[0017] Secondly, to address the technical challenge of secondary agglomeration during template precipitation and subsequent growth, which leads to a widening of particle size distribution, this invention introduces a dispersant for dynamic stabilization. The dispersant is adsorbed onto the template surface, and the collision and fusion between templates are effectively prevented by steric hindrance, making the growth environment of all template particles in the system more consistent. Ultimately, monodisperse spherical templates with uniform particle size are obtained, achieving precise control of product size distribution.

[0018] Finally, in the method of this invention, the dispersant plays a role throughout the entire process of template formation and stabilization. Because the monodispersity and spherical regularity of the template are formed in the early stages of synthesis, the subsequent hydrolysis and deposition of the silicon source can proceed on a highly uniform substrate surface, thereby ensuring the uniformity of the final hollow silica shell thickness and making the entire preparation process highly repeatable.

[0019] In summary, this invention successfully solves the technical challenge of simultaneously achieving uniform size and regular spherical morphology of hollow silica by introducing a dispersant in situ during the template self-assembly process for spatial confinement and dynamic stabilization. This simplifies the preparation process while maintaining uniform size and regular spherical morphology in hollow silica. This method not only avoids the cumbersome steps of the hard template method and the instability of the soft template method, but also endows the product with excellent monodispersity, regular spherical morphology, and a controllable preparation process, providing a practical and feasible technical path for the large-scale application of hollow silica materials in high-precision fields. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a TEM image of the monodisperse hollow silica prepared in Example 1 of the present invention; Figure 2 This is a TEM image of the monodisperse hollow silica prepared in Example 2 of the present invention; Figure 3 This is a TEM image of the monodisperse hollow silica prepared in Example 3 of the present invention; Figure 4 This is a TEM image of the monodisperse hollow silica prepared in Example 4 of the present invention; Figure 5 This is a TEM image of the monodisperse hollow silica prepared in Example 5 of the present invention; Figure 6 This is a TEM image of the calcined sample in Comparative Example 1 of this invention; Figure 7 This is a TEM image of the calcined sample in Comparative Example 2 of this invention; Figure 8 This is a TEM image of the calcined sample in Comparative Example 3 of this invention; Figure 9 This is a TEM image of the calcined sample in Comparative Example 4 of this invention; Figure 10 This is a TEM image of the calcined sample in Comparative Example 5 of this invention; Figure 11 This is a TEM image of the calcined sample in Comparative Example 6 of this invention; Figure 12 This is a TEM image of the calcined sample in Comparative Example 7 of this invention; Figure 13This is a TEM image of the calcined sample in Comparative Example 8 of this invention; Figure 14 This is a TEM image of the calcined sample in Comparative Example 9 of this invention; Figure 15 This is a TEM image of the calcined sample in Comparative Example 10 of this invention. Figure 16 This is a TEM image of the calcined sample in Comparative Example 11 of this invention; Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0024] This invention provides a method for preparing monodisperse spherical hollow silica, comprising the following steps: S1. Obtain a mixture containing a template agent, a dispersant, and a catalyst, wherein the template agent self-assembles and precipitates monodisperse spherical templates under the action of the catalyst and the dispersant.

[0025] It should be noted that "monodisperse" in this invention refers to the spherical template and the final product having highly uniform geometric dimensions, consistent morphology, and a single-cavity state. Specifically, at the microscale, the hollow structure cavity is a single spherical cavity, with no obvious agglomeration or adhesion between particles, a narrow particle size distribution range, and a size range of approximately 200±50nm, exhibiting good single-particle dispersion characteristics and a regular spherical geometric appearance.

[0026] In some embodiments, the concentration of the template agent in the mixture is 0.0065-0.014 mol / L, the concentration of the dispersant in the mixture is 1.5-4.5 g / L, and the concentration of the catalyst in the mixture is 0.55-0.9 mol / L.

[0027] For example, the concentration of the template agent in the mixture can be 0.0065 mol / L, 0.007 mol / L, 0.008 mol / L, 0.009 mol / L, 0.010 mol / L, 0.011 mol / L, 0.012 mol / L, 0.013 mol / L, 0.014 mol / L, and any value between such a minimum and maximum, or a range of any two values.

[0028] It should be noted that the concentration of the template agent in the mixture is controlled at 0.0065-0.014 mol / L in this invention, so that the concentration of the template agent is controlled at a suitable level. Too low a concentration will result in an excess of Si and the formation of free silica nanoparticles, while too high a concentration may result in too little Si and the inability to form a stable and complete silica structure.

[0029] For example, the concentration of the dispersant in the mixture can be 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, and any value between such a minimum and maximum value, or a range of any two values.

[0030] It should be noted that when the concentration of dispersant in the mixture is less than 1 g / L, the formed silica is a hollow structure with multiple interconnected cavities; when the concentration of dispersant in the mixture is greater than 5 g / L, the formed silica does not have a uniform spherical shape, but rather exhibits an aggregated dendritic structure.

[0031] For example, the concentration of the catalyst in the mixture can be 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, and any value between such a minimum and maximum, or a range of any two values.

[0032] It should be noted that when the catalyst concentration in the mixture is less than 0.4 mol / L, the Basic Blue 7 template will disintegrate prematurely, resulting in the formation of a large amount of solid nano-silica. When the catalyst concentration in the mixture is greater than 0.9 mol / L, the excessively high catalyst concentration will induce fluorosilicic acid to directly convert into solid nano-silica, making it impossible to completely form a hollow structure.

[0033] In some embodiments, the catalyst includes at least one of ammonia and sodium hydroxide; the template agent includes Basic Blue 7; and the dispersant includes polyvinylpyrrolidone.

[0034] It should be noted that the present invention limits the type of template agent to Basic Blue 7, so that it can form a spherical template under the catalysis of ammonia water, and then form monodisperse spherical silica. In contrast, other reagents that belong to the same cationic triphenylmethane organic compounds as Basic Blue 7, such as ethyl violet, cannot form a spherical template, and therefore cannot form monodisperse spherical silica with a uniform morphology. The present invention specifies that the dispersant is polyvinylpyrrolidone, which enables the Basic Blue 7 template to form a monodisperse structure, thereby forming a monodisperse hollow silica with a single chamber, uniform structure and completeness; in contrast, other polymeric dispersants, such as polyoxyethylene polyoxypropylene (polyether F127), cannot form spherical monodisperse hollow silica with a single chamber structure and uniform morphology.

[0035] It should be noted that, without the addition of a dispersant (see Comparative Example 1), the template agent lacks a steric barrier after self-assembly and precipitation. The precipitated spherical templates are prone to collision and fusion, forming irregular aggregates. Ultimately, after calcination, only a multi-chamber amorphous hollow structure can be obtained, and monodisperse spherical hollow silica with a regular morphology cannot be obtained. Similarly, when the dispersant concentration is too low (see Comparative Example 2, PVP concentration is only 0.5 g / L), the dispersant molecules adsorbed on the template surface are insufficient to form an effective steric hindrance layer, failing to completely prevent contact and merging between template particles. Therefore, the product still exhibits a multi-chamber structure.

[0036] This indicates that only when the concentration of the dispersant in the mixture reaches the range (1-5 g / L) defined in this invention can its steric hindrance effect be fully utilized, thereby achieving in-situ stability and size locking of the template precipitation process, overcoming the agglomeration problem in the assembly process, and thus ensuring the monodispersity and spheric regularity of the final product.

[0037] In some embodiments, obtaining the mixture comprising the template agent, the dispersant and the catalyst includes: mixing the template agent, the dispersant and the catalyst, and stirring at a speed of 100-600 rpm for 5-30 minutes at a temperature of 30-80°C to obtain the mixture.

[0038] In some more specific embodiments, the template agent, dispersant, catalyst, and deionized water can be mixed to adjust the concentration of each component in the mixture.

[0039] For example, the mixing order of the template agent, deionized water, catalyst, and dispersant can be as follows: first, mix the dispersant with deionized water, and then add the template agent and ammonia water in sequence to obtain the mixture.

[0040] It should be noted that the mixture of dispersant, template agent, catalyst and / or deionized water should be stirred at a temperature of 30-80℃ to ensure that the template can exist stably in the aqueous solution. Excessively high temperatures will cause the template to become unstable and decompose.

[0041] S2. Add the silicon source to the mixture, and the silicon source undergoes a hydrolysis reaction to form silicon dioxide on the surface of the monodisperse spherical template. After the hydrolysis reaction is completed, collect the solid phase to obtain the precursor.

[0042] In some embodiments, the silicon source includes fluorosilicic acid, wherein the concentration of the fluorosilicic acid is 0.10-0.55 mol / L.

[0043] In some embodiments, in the mixture of the silicon source and the mixture, the concentration of the silicon source is 0.02-0.11 mol / L.

[0044] For example, in the mixture system of the silicon source and the mixture, the concentration of the silicon source can be 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.10 mol / L, 0.11 mol / L, and any value between such a minimum and maximum value, or a range of any two values.

[0045] In some embodiments, the silicon source can be added to the mixture at a rate of 0.5-5 ml / min.

[0046] In some embodiments, the hydrolysis reaction is carried out at a temperature of 40-90°C and for a duration of 2-8 hours.

[0047] In some more specific embodiments, the hydrolysis reaction can be carried out under stirring conditions, with a stirring rate of 100-600 rpm.

[0048] For example, the temperature of the hydrolysis reaction can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and any value between such a minimum and maximum value, or a range of any two values.

[0049] For example, the duration of the hydrolysis reaction can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 7h, 8h, or any value between such a minimum and maximum value, or a range of any two values.

[0050] In some embodiments, the prepared precursor can be dried, and the drying method can be freeze drying or oven drying at a constant temperature.

[0051] S3. The precursor is calcined to obtain the monodisperse spherical hollow silica.

[0052] In some embodiments, the calcination temperature is 500-800°C, and the calcination time is 1-6 hours.

[0053] For example, the calcination temperature can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, and any value between such a minimum and maximum, or a range of any two values.

[0054] For example, the calcination time can be 1h, 2h, 3h, 4h, 5h, 6h, or any value between such a minimum and maximum value, or a range of any two values.

[0055] In step S1 of the present invention, when the template agent includes one or more cationic triphenylmethane organic compounds such as Basic Blue 7, the template agent will precipitate spherical templates with positively charged surfaces after being added to the catalyst; the dispersant includes high molecular weight organic dispersants such as PVP. The addition of the dispersant inhibits the spontaneous aggregation of the template through a steric stabilization mechanism, so that it is uniformly and stably dispersed in the system to form monodisperse spherical templates.

[0056] In step S2 of the present invention, when the silicon source is a fluorosilicic acid solution, the negatively charged fluorosilicate ions (SiF6) 2- It combines with a spherical template and hydrolyzes on the surface of the monodisperse spherical template to form silica.

[0057] In step S3 of this invention, the high-temperature calcination process removes the residual template agent precipitated inside the silica, forming a hollow structure in the silica to obtain monodisperse hollow silica.

[0058] The present invention provides a monodisperse spherical silica, which is prepared by the preparation method described above, wherein the size of the monodisperse spherical silica is 150-250 nm.

[0059] It should be noted that the size of the monodisperse spherical hollow silica described in this invention does not simply depend on the adjustment of a single parameter, but is a precise control result achieved through the synergistic effect of the template agent and the dispersant. Specifically, the concentration of the template agent directly determines the initial size of the self-assembled spherical template, while the dispersant stabilizes and locks the template in situ during the template precipitation process through steric hindrance, preventing the template particles from fusing and growing during the growth process.

[0060] Both are indispensable: without a dispersant, the template will undergo uncontrolled fusion, resulting in a multi-chamber structure and a widened size distribution in the product; without sufficient template agent, it is difficult to obtain complete hollow spheres within the target size range. It is precisely this synergistic matching of the two that allows the final product size to be stably controlled within a narrow range of 150-250 nm, while maintaining excellent monodispersity and sphericity. This mechanism of precisely locking the product size through the synergistic regulation of template agent and dispersant is one of the key innovations that distinguishes this invention from existing technologies.

[0061] Therefore, for example, the concentration of the template agent in the mixture can be 0.010 mol / L, 0.011 mol / L, 0.012 mol / L, 0.013 mol / L, 0.014 mol / L, and any value between such a minimum and maximum, or a range of any two values.

[0062] For example, the size of the monodisperse spherical silica can be 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, and any value between such a minimum and maximum value, or a range of any two values.

[0063] This invention provides an application of the monodisperse spherical silica described above in fields such as catalytic chemistry, optical materials, and precise drug delivery.

[0064] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided: Example 1 S1. Dissolve 0.5 g of PVP in 190 ml of deionized water and stir until completely dissolved; then add 1.28 g of Basic Blue 7 to the PVP solution and stir until completely dissolved; after stirring, add 10.8 ml of ammonia water to obtain a mixture; the concentration of PVP in the mixture is 2.5 g / L, the concentration of Basic Blue 7 is 0.0124 mol / L, and the concentration of ammonia water in the mixture is approximately 0.72 mol / L; stir the mixture at 50℃ and 400 rpm for 15 min.

[0065] S2. 50 ml of a fluorosilicic acid solution with a molar concentration of approximately 0.32 mol / L was added dropwise to the mixture at a rate of 1 ml / min. The concentration of fluorosilicic acid in the mixture was 0.064 mol / L. After the addition was complete, the mixture was stirred at 80°C and 400 rpm for 6 hours. The fluorosilicic acid underwent a hydrolysis reaction to form silica on the surface of the monodisperse spherical template. After the hydrolysis reaction was complete, the solid phase was collected to obtain the precursor.

[0066] S3. The precursor was dried at 80℃ for 12 hours. The dried precursor was then calcined in a muffle furnace at 650℃ for 4 hours at a heating rate of 10℃ / h to obtain monodisperse hollow silica.

[0067] Figure 1 This is a TEM image of the calcined sample from Example 1. From... Figure 1 It can be seen that the obtained silica has a regular monodisperse hollow spherical structure; the particle size is uniform, and the particle size distribution is concentrated in a narrow range of 200±50nm.

[0068] Example 2 Compared to Example 1, all other conditions remain unchanged in this example, except for the amount of Basic Blue 7 added: the amount of Basic Blue 7 added becomes 0.96 g, that is, the concentration of Basic Blue 7 in the mixture is about 0.0093 mol / L.

[0069] Figure 2 This is a TEM image of the calcined sample from Example 2. From... Figure 2 It can be seen that the obtained silica has a monodisperse hollow structure with regular spherical morphology. Compared with Comparative Example 7 (with a large number of nanoparticles) and Comparative Example 8 (with nanoparticle byproducts still present), the nanoparticle byproducts in this example have been significantly reduced, and the product purity has been significantly improved. However, compared with Example 1, the particle size of the hollow silica obtained in this example is significantly smaller, specifically 50-150 nm. This is because the concentration of Basic Blue 7 is lower, and the size of the template formed can be relatively smaller, resulting in a relatively smaller particle size of silica. This indicates that the concentration of the template agent has a decisive influence on the size of the self-assembled template.

[0070] Example 3 Compared to Example 1, all other conditions remain unchanged in this example, except that the stirring temperature in step S1 is adjusted to 60 ℃.

[0071] Figure 3 These are TEM images of the calcined sample from Example 3. Figure 3 It can be observed that the obtained silica has a monodisperse hollow structure.

[0072] Example 4 Compared to Example 1, all other conditions remain unchanged in this example, except that the stirring temperature in step S1 is adjusted to 70 ℃.

[0073] Figure 4 This is a TEM image of the calcined sample from Example 4. Figure 4 It can be observed that the obtained silica has a monodisperse hollow structure.

[0074] Example 5 Compared to Example 1, all other conditions remain unchanged in this example, except that the stirring temperature in step S1 is adjusted to 80 ℃.

[0075] Figure 5 This is a TEM image of the calcined sample from Example 5. Figure 5 It can be observed that the obtained silica has a monodisperse hollow structure.

[0076] Comparative Example 1 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of PVP added: the amount of PVP added became 0 g, that is, no PVP was added.

[0077] Figure 6 This is a TEM image of the calcined sample from Comparative Example 1. Figure 6 It can be observed that the obtained silica has a multi-chamber hollow structure, indicating that monodisperse hollow silica cannot be formed without PVP as a dispersant.

[0078] Comparative Example 2 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of PVP added: the amount of PVP added became 0.1 g, that is, the PVP concentration in the mixture was 0.5 g / L.

[0079] Figure 7 This is a TEM image of the calcined sample from Comparative Example 2. Figure 7 It can be observed that the obtained silica has a multi-chamber hollow structure, indicating that when the concentration of PVP dispersant is too low, monodisperse hollow silica cannot be formed.

[0080] Comparative Example 3 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of PVP added: the amount of PVP added became 0.25 g, that is, the PVP concentration in the mixture was 1.25 g / L.

[0081] Figure 8 These are TEM images of the calcined sample from Comparative Example 3. Figure 8 It can be observed that although some of the obtained silica particles are hollow, they are still mixed with multi-chamber and irregularly shaped products, the particle size distribution is relatively wide, and the spherical regularity is insufficient.

[0082] Comparative Example 4 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of PVP added: the amount of PVP added became 1 g, that is, the PVP concentration in the mixture was 5 g / L.

[0083] Figure 9 This is a SEM image of the calcined sample from Comparative Example 4. From... Figure 9 It can be observed that the obtained silica particles are dendritic aggregates and do not form a uniform spherical structure. This indicates that when the concentration of PVP dispersant exceeds the preferred range of this invention, its steric hindrance effect will cause template deformation and inhibit the bonding between the template and silica, failing to ensure the monodispersity and spherical regularity of the product.

[0084] The results of Examples 1, 1, 2, 3, and 4 confirm that PVP plays a crucial role as a dispersant in the synthesis of monodisperse spherical hollow silica. When PVP is not added or is insufficient, the template undergoes uncontrollable fusion and aggregation during precipitation due to the lack of an effective steric barrier, resulting in a multi-chamber structure, broad particle size distribution, and irregular spherical morphology in the final product. Only when the PVP concentration reaches the range defined in this invention can its steric effect fully achieve in-situ stability and size locking of the template, thereby simultaneously obtaining ideal monodispersity and regular spherical morphology. This indicates that the introduction of the dispersant and precise control of its concentration are key to solving the technical challenge of "simultaneously achieving size uniformity and regular morphology while simplifying the preparation process."

[0085] Comparative Example 5 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of ammonia added: the amount of ammonia added became 7.2 ml, that is, the concentration of ammonia in the mixture was about 0.52 mol / L.

[0086] Figure 10 These are TEM images of the calcined sample from Comparative Example 5. From... Figure 10It can be observed that although the obtained silica exhibits a monodisperse hollow structure, a large number of free nano-silica particles exist in the system. The presence of these byproducts compromises the purity and morphological uniformity of the product. This indicates that when the ammonia concentration is too low, the silicon source hydrolysis is insufficient, and some silicon-containing ions fail to effectively deposit on the template surface, resulting in incomplete formation of the hollow structure.

[0087] Comparative Example 6 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of ammonia added: the amount of ammonia added became 14.4 ml, that is, the concentration of ammonia in the mixture was about 1.04 mol / L.

[0088] Figure 11 These are TEM images of the calcined sample from Comparative Example 6. From... Figure 11 It can be observed that the obtained silica matrix is ​​a monodisperse hollow structure, but solid silica particles are mixed in the sample. This indicates that excessively high ammonia concentration accelerates the homogeneous nucleation of the silicon source in the liquid phase, competitively inhibiting its heterogeneous deposition on the template surface, thereby destroying the integrity of the hollow structure of the product.

[0089] Comparative Example 7 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of ammonia added: the amount of ammonia added became 18.1 ml, that is, the concentration of ammonia in the mixture was about 1.3 mol / L.

[0090] Figure 12 This is a TEM image of the calcined sample from Comparative Example 7. Although the resulting silica matrix is ​​a monodisperse hollow structure, the proportion of solid silica particles in the sample further increases, and the thickness of some hollow spherical shells is uneven, resulting in a decrease in spherical regularity. This indicates that when the ammonia concentration is too high, the homogeneous nucleation rate of the silicon source in the liquid phase is significantly accelerated, creating intense competition with the heterogeneous deposition on the template surface, leading to an increase in solid byproducts. At the same time, the excessively rapid hydrolysis rate also affects the uniform deposition of silica on the template surface.

[0091] Comparative Example 8 Compared to Example 1, all other conditions remained unchanged in this comparative example, except for the amount of Basic Blue 7 added: the amount of Basic Blue 7 added became 0.32 g, that is, the concentration of Basic Blue 7 in the mixture was about 0.0031 mol / L.

[0092] Figure 13 These are TEM images of the calcined sample from Comparative Example 8. From... Figure 13It can be observed that the obtained product is mainly silica nanoparticles, with very few hollow structures. This indicates that when the template agent concentration is too low, the number of available self-assembled templates in the system is insufficient, and most of the silicon source cannot form hollow structures through template surface deposition. Instead, homogeneous nucleation occurs in the liquid phase, generating a large number of amorphous nanoparticle byproducts, which severely damages the structural integrity and morphological uniformity of the product.

[0093] Comparative Example 9 Compared to Example 1, all other conditions in this comparative example remained unchanged, except for the amount of Basic Blue 7 added: the amount of Basic Blue 7 added became 0.64 g, that is, the concentration of Basic Blue 7 in the mixture was approximately 0.0062 mol / L.

[0094] Figure 14 These are TEM images of the calcined sample from Comparative Example 9. From... Figure 13 It can be observed that the obtained product is mainly hollow, but a certain amount of silica nanoparticles are still present as byproducts in the sample. This indicates that the concentration of Basic Blue 7 template agent needs to reach a certain level to completely induce the conversion of fluorosilicic acid into a hollow structure.

[0095] Comparative Example 10 Compared to Example 1, the other conditions in this comparative example remain unchanged, except for the type of dispersant: PVP in step S1 is replaced with polyether F127, which is also a polymeric dispersant.

[0096] Figure 15 These are TEM images of the calcined sample from Comparative Example 10. Figure 14 It can be observed that the obtained product is mainly hollow, but the sample is a multi-chambered hollow silica with an uneven morphology. This indicates that polyether F123, as a polymeric dispersant, cannot exert a dispersing effect similar to that of PVP.

[0097] Comparative Example 11 Compared to Example 1, the other conditions in this comparative example remain unchanged, except for the type of template agent: the template agent in step S1 is replaced with ethyl violet, which is also a cationic triphenylmethane organic compound.

[0098] Figure 16 This is a SEM image of the calcined sample from Comparative Example 11. From... Figure 15 It can be observed that the obtained product is aggregated silica. This indicates that ethyl violet, which is also a cationic triphenylmethane-based organic compound, cannot function as a template like Basic Blue 7.

[0099] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing monodisperse spherical hollow silica, characterized in that, Including the following steps: A mixture containing a template agent, a dispersant, and a catalyst is obtained, wherein the concentration of the dispersant in the mixture is 1.5-4.5 g / L; the template agent self-assembles and precipitates monodisperse spherical templates under the action of the catalyst and the dispersant. A silicon source is added to the mixture, and the silicon source undergoes a hydrolysis reaction to form silicon dioxide on the surface of the monodisperse spherical template. After the hydrolysis reaction is completed, the solid phase is collected to obtain the precursor. The precursor is calcined to obtain the monodisperse spherical hollow silica.

2. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The concentration of the template agent in the mixture is 0.0065-0.014 mol / L, and the concentration of the catalyst in the mixture is 0.55-0.9 mol / L.

3. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The catalyst includes at least one of ammonia and sodium hydroxide; the template agent includes Basic Blue 7; and the dispersant includes polyvinylpyrrolidone.

4. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The silicon source is added to the mixture in the form of a silicon source solution; the concentration of the silicon source in the silicon source solution is 0.10-0.55 mol / L; the silicon source includes fluorosilicic acid.

5. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, In the mixture system of the silicon source and the mixture, the concentration of the silicon source is 0.02-0.11 mol / L.

6. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The hydrolysis reaction is carried out at a temperature of 40-90℃ and for a duration of 2-8 hours.

7. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The calcination temperature is 500-800℃, and the calcination time is 1-6h.

8. The method for preparing monodisperse spherical hollow silica according to claim 1, characterized in that, The process of obtaining the mixture containing the template agent, dispersant, and catalyst includes: stirring the template agent, the dispersant, and the catalyst at a temperature of 30-80°C and a speed of 100-600 rpm for 5-30 minutes to obtain the mixture.

9. A monodisperse spherical silica, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the monodisperse spherical silica as described in claim 9 in catalytic chemistry, optical materials, or precise drug delivery.

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