Hollow silicon dioxide microsphere with double-layer shell structure and preparation method of hollow silicon dioxide microsphere

Abstract

The invention discloses a hollow silicon dioxide microsphere with a double-layer shell structure and a preparation method thereof, the hollow silicon dioxide microsphere with the double-layer shell structure is a spherical body comprising an inner core layer and an outer shell layer, the inner core layer and the outer shell layer are spherical bodies, the inner core layer and the outer shell layer form the double-layer shell structure, the inner core layer is located in the outer shell layer, and the outer shell layer is located in the outer shell layer. The interior of the inner core layer is of a hollow structure, a hollow structure is formed between the inner core layer and the shell layer, and the thickness of the inner core layer is 10-100 nm; the thickness of the outer shell layer is 10-50nm; the distance between the inner core layer and the outer shell layer is 5-100nm, mesopores are uniformly distributed in the inner core layer and the outer shell layer, and the pore diameter of the mesopores is 1-10nm. The hollow silicon dioxide microsphere with the double-layer shell structure is uniform in particle size distribution, good in monodispersity, relatively high in strength and good in dispersity. The preparation method of the microspheres is simple and easy to implement and easy to industrialize, and the hollow silicon dioxide microspheres with the double-layer shell structure can be prepared through a self-template method and a simple and effective selective etching strategy.

Description

Technical Field

[0001] The invention belongs to the field of organic and inorganic silicon microspheres, and particularly relates to a double-shell structured hollow silicon dioxide microsphere and a preparation method thereof. Background Art

[0002] Multi-shell hollow materials have the characteristics of low density, large specific surface area, and interstitial spacing between shells, and have attracted considerable attention in the fields of drug delivery, nanoreactors, and catalysis. Multi-shell hollow silica microspheres have a complex structure, so their synthesis is more challenging than that of single-shell hollow silica microspheres.

[0003] The most commonly used methods for preparing double-layer hollow silica microspheres include the hard template method and the soft template method. The double-layer silica microspheres synthesized by the hard template method need to be calcined at high temperature to remove the template after the reaction is completed. The steps are cumbersome, and the gas generated by the calcination pollutes the environment, which is not in line with the concept of green environmental protection. Although the double-layer silica microspheres synthesized by the soft template method do not need to remove the template, the soft template method usually requires the participation of organic solvents, and the template is usually in a fluid form with poor stability, and the morphology of the formed microspheres is difficult to control.

[0004] Since both methods have their own defects, the self-template method, which does not require the introduction of a template, has a simple preparation procedure and low production cost, has attracted great attention. The self-template method for preparing hollow silica microspheres usually uses the silica microspheres themselves as templates. Usually, the silica particles themselves dissolve and re-grow, and then undergo selective etching to form hollow silica microspheres. The self-template preparation of multilayer hollow silica microspheres is based on the difference in the internal and external structures of the silica microspheres. At present, the self-template method for preparing double-layer hollow silica microspheres usually uses an alternating acid-base selective etching strategy or a hydrothermal etching strategy. The alternating acid-base selective etching strategy for preparing double-layer hollow silica microspheres requires the use of strong acids and strong bases to control the pH value multiple times during the reaction process, and the steps are very cumbersome.

[0005] In order to overcome the shortcomings of the alternating acid-base selective etching strategy, which repeatedly uses strong acids and strong bases and regulates the pH, a hydrothermal etching strategy is used to prepare double-layer hollow silica microspheres. However, traditional hydrothermal etching is carried out in a reactor and requires a high temperature and high pressure process, which is dangerous and time-consuming. Therefore, in order to solve the above technical problems, a novel atmospheric pressure and low temperature hydrothermal method is developed, which can prepare double-shell hollow silica microspheres without using strong acids and strong bases and without high temperature and high pressure reaction conditions, which is of great significance. Summary of the invention

[0006] One object of the present invention is to provide a double-shell structured hollow silica microsphere, comprising a spherical body of an inner core layer and an outer shell layer, wherein the inner core layer and the outer shell layer are both provided with a plurality of mesopores, which is beneficial to improve the strength of the inner core layer and the outer shell layer and maintain their low dielectric properties. Another object of the present invention is to provide a method for preparing the above-mentioned double-shell structured hollow silica microsphere, which utilizes a normal pressure and low temperature hydrothermal method to solve the shortcomings of the prior art of using strong acid and strong base, and high temperature and high pressure reaction conditions to prepare double-shell structured hollow silica microspheres.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In the first aspect, the present invention provides a double-shell structured hollow silica microsphere, wherein the double-shell structured hollow silica microsphere is a spherical body comprising an inner core layer and an outer shell layer, wherein the inner core layer and the outer shell layer are both spherical bodies, and the inner core layer and the outer shell layer form a double-shell structure, wherein the inner core layer is located inside the outer shell layer, the interior of the inner core layer is a hollow structure, and a hollow structure is formed between the inner core layer and the outer shell layer, wherein the thickness of the inner core layer is 10-100 nm; the thickness of the outer shell layer is 10-50 nm, and a plurality of mesopores are distributed on the inner core layer and the outer shell layer, and the pore size of the mesopores is 1-10 nm.

[0009] After low dielectric air is introduced into the electronic material of the double-shell hollow silica microspheres of the present invention, the specific small-sized mesopores on the inner core layer and the outer shell layer are conducive to the long-term retention of air in the electronic material, and the low dielectric properties of the electronic material can be maintained for a long time; moreover, the specific small-sized mesopores are conducive to further improving the strength of the inner core layer and the outer shell layer, thereby enhancing the structural stability of the double-shell hollow silica microspheres, which is more conducive to resisting the invasion of external forces, and ultimately being able to better maintain its low dielectric properties.

[0010] The pore size of the mesopores of the present invention is 1-10 nm. According to some embodiments of the present invention, the pore size of the mesopores is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 nm.

[0011] It is worth noting that when the pore size of the mesopore is greater than 10nm, other components in the electronic material may enter the double-shell hollow silica microsphere through the mesopore, thereby affecting the space size of the hollow structure and the hollow structure, reducing the amount of low-dielectric medium air introduced, and at the same time, the large pore size of greater than 10nm will also affect the strength of the inner core layer and the outer shell layer, reducing the structural stability of the double-shell hollow silica microsphere, and ultimately failing to better maintain the low dielectric properties of the electronic material, while reducing the processability of the low-dielectric electronic material in application. When the pore size of the mesopore is less than 1nm, it is basically a solid and compact structure, similar to the absence of a mesoporous structure, which is not conducive to hydrothermal etching and the adsorption and release of guest molecules. Preferably, the pore size of the mesopore is 2 to 5nm.

[0012] Preferably, the pore volume of the mesopores is 0.5-3 cm 3 g -1 .

[0013] In the present invention, the pore volume refers to the pore (diameter) volume of the mesopores.

[0014] In the present invention, the synthetic raw material of the inner core layer contains a first silicon source, and the synthetic raw material of the outer shell layer contains a second silicon source;

[0015] The first silicon source and the second silicon source are independently selected from at least one of the compounds represented by the general formula R1Si(OR4)3, the compounds represented by the general formula R2R3Si(OR4)2 and the compounds represented by the general formula Si(OR4)4, wherein R4 is a C1-6 alkyl group; R1, R2 and R3 are independently selected from hydrogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C2-6 alkynyl, substituted or unsubstituted C6-12 aryl; the substitution refers to substitution by at least one substituent selected from amino, amino substituted with C1-6 aminoalkyl, C1-6 alkoxy substituted with C1-6 aminoalkyl, C1-6 alkoxy substituted with oxygen and C1-6 hydrocarbon acyloxy substituted with oxygen.

[0016] In one of the preferred aspects, the raw material for synthesizing the inner core layer is only the first silicon source, and the raw material for synthesizing the outer shell layer is only the second silicon source.

[0017] When the double-shell hollow silica microspheres of the present invention are used to prepare electronic materials, low-dielectric air can be introduced into the electronic materials due to their hollow structures and hollow core structures, thereby imparting good dielectric properties (i.e., reducing the dielectric properties of the electronic materials) to obtain low-dielectric materials.

[0018] The double-shell structure, as well as the inner core layer and outer shell layer of specific thickness improve the structural stability of the hollow silica microspheres in the double-shell structure, making the hollow silica microspheres in the double-shell structure stronger and better able to resist the invasion of external forces, thereby being more conducive to the introduction of low-dielectric dielectric air into electronic materials and providing good dielectric properties.

[0019] Preferably, the thickness of the inner core layer is 10 to 100 nm; the thickness of the outer shell layer is 10 to 50 nm. According to some embodiments of the present invention, the thickness of the inner core layer of the present invention is 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 nm, and the thickness of the outer shell layer of the present invention is 10, 15, 20, 25, 30, 35, 40, 45 or 50 nm.

[0020] It is worth noting that when the thickness of the inner core layer and / or the outer shell layer is less than 10nm, the double-shell structure hollow silica microspheres have poor structural stability and strength, cannot resist the invasion of external forces well, are easily broken, are not conducive to the introduction of low-dielectric dielectric air in electronic materials, and cannot better provide low-dielectric properties of electronic materials. When the thickness of the inner core layer is greater than 100nm and / or the thickness of the outer shell layer is greater than 50nm, the double-shell structure hollow silica microspheres have strong structural stability, but the space of the hollow structure and the hollow structure becomes smaller, and sufficient low-dielectric dielectric air cannot be introduced into the electronic material, which is not conducive to maintaining its low dielectric properties.

[0021] In the present invention, the distance between the inner core layer and the outer shell layer refers to the distance between the outer wall of the inner core layer and the inner wall of the outer shell layer.

[0022] Preferably, the thickness of the outer shell layer is smaller than the thickness of the inner core layer.

[0023] Preferably, at least one of the following (1)-(7) is included:

[0024] (1) The first silicon source and the second silicon source are the same or different;

[0025] (2) Both the first silicon source and the second silicon source have hydrothermal etching reactivity;

[0026] (3) The first silicon source is a compound represented by the general formula Si(OR4)4;

[0027] (4) The second silicon source is a compound represented by the general formula Si(OR4)4;

[0028] (5) The compound represented by the general formula R1Si(OR4)3 is at least one of C6H5Si(OCH3)3 (phenyltrimethoxysilane), CH3Si(OCH3)3 (methyltrimethoxysilane), methacryloxypropyltrimethoxysilane, glycidyloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropyloxy)propyltrimethoxysilane, γ-(methacryloxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, and methyltriethoxysilane (MTEOS);

[0029] (6) The compound represented by the general formula R2R3Si(OR4)2 is dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiacetoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, di-n-butyldimethoxysilane, diisobutyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, methylvinyldimethoxysilane, divinyldiethoxysilane, 3-methyl At least one of acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-mercaptopropylmethyldimethoxysilane or 3-isocyanatepropylmethyldiethoxysilane;

[0030] (7) The compound represented by the general formula Si(OR4)4 is at least one of tetramethoxysilane, tetraethoxysilane (tetraethyl orthosilicate, TEOS), tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane or tetraacetoxysilane.

[0031] Preferably, at least one of the following (1)-(5) is included:

[0032] (1) The average diameter of the inner core layer is 50-1000 nm;

[0033] (2) The average diameter of the outer shell layer is 0.1-10 μm;

[0034] (3) The distance between the inner core layer and the outer shell layer is 5-100 nm;

[0035] (4) The ratio of the average diameter of the inner core layer to the outer shell layer is 1:(1.1-10);

[0036] (5) The specific surface area of ​​the double-shell hollow silica microspheres is 500 to 2000 m 2 g -1 .

[0037] In the present invention, the specific surface area is the total specific surface area of ​​the inner core layer and the outer shell layer.

[0038] In a second aspect, the present invention provides a method for preparing the double-shell hollow silica microspheres as described above, comprising the following steps:

[0039] 1) adding a first emulsifier to an alkaline reaction solvent and performing a dispersion treatment, and then adding a first silicon source to react to obtain a reaction solution containing solid silica microspheres-1 (S-1);

[0040] 2) firstly mixing a second emulsifier into the reaction solution, and then adding a second silicon source to react to obtain solid silica microspheres-2 (S-2);

[0041] 3) hydrothermally etching the solid silica microsphere-2 (S-2) to obtain a double-shell structured hollow silica microsphere (HS-2);

[0042] Wherein, the reaction solvent includes an alcohol dispersant and water;

[0043] The first silicon source and the second silicon source are as defined above;

[0044] The first emulsifier and the second emulsifier are independently selected from at least one of C12-C22 alkyl trimethyl ammonium chloride, C12-C22 alkyl trimethyl ammonium bromide and C12-C22 alkyl trimethyl ammonium p-toluenesulfonate.

[0045] The preparation method of the above-mentioned double-shell hollow silica microspheres is a hydrothermal method. Compared with the hard template method or soft template method of the prior art, it does not require high-temperature calcination to remove the template, nor does it require the participation and control of organic solvents. The hydrothermal method of the present invention utilizes a two-step sol-gel method to synthesize silica microspheres, which belong to double-shell hollow silica microspheres prepared from the template. The solid silica microspheres grown by the two-step sol-gel method are then subjected to a one-step normal pressure hydrothermal treatment to achieve the transformation from a solid to a double-shell structure, and no corrosive etchant needs to be added during the etching process, which is more in line with green environmental protection.

[0046] More advantageously, compared to the conventional hydrothermal etching method, which is carried out in a reactor and requires harsh reaction conditions of high temperature and high pressure, which is dangerous and time-consuming, the preparation method of the double-shell hollow silica microspheres of the present invention can be applied to the etching process in a normal pressure and low temperature environment, which can solve the harsh high temperature and high pressure conditions and complicated process problems of the prior art. In some embodiments of the present invention, at least one of the following (1)-(6) is included:

[0047] (1) In step 1), the volume ratio of the alcohol dispersant to water is 0.4-1.2, specifically 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2;

[0048] (2) In step 1), the pH of the alkaline reaction solvent is 8.5-9.5, specifically 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.3, 9.4 or 9.5;

[0049] (3) the temperature at which the first silicon source is added to react in step 1) is the same as or different from the temperature at which the second silicon source is added to react in step 2);

[0050] (4) In step 1), the temperature for adding the first silicon source to react is 25-55° C.;

[0051] (5) In step 2), the temperature for adding the second silicon source to react is 25-55° C.;

[0052] (6) In step 3), in the hydrothermal etching, the solid-to-liquid ratio of solid silica microspheres-2 and water is (20-50) mg: (10-50) mL.

[0053] In the present invention, the volume ratio of the alcohol dispersant to water is also referred to as the alcohol-water ratio.

[0054] In order to control the morphology of the double-shell hollow silica microspheres, in some embodiments of the present invention, preferably, at least one of the following (1)-(6) is included:

[0055] (1) In step 1), the volume ratio of the alcohol dispersant to water is 0.4-1;

[0056] (2) In step 1), the alcohol dispersant is at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, n-butanol, tert-butanol, and isoamyl alcohol;

[0057] (3) In step 1), the pH of the alkaline reaction solvent is 9.0-9.5;

[0058] (4) In step 1), the temperature of adding the first silicon source to react is 30-50° C. and the time is 0.5-3 h;

[0059] (5) In step 2), the temperature of adding the second silicon source to react is 30-50° C. and the time is 0.5-3 h;

[0060] (6) In step 3), in the hydrothermal etching, the solid-liquid ratio of solid silica microspheres-2 and water is 50 mg: (10-50) mL. For example, based on 50 mg of solid silica microspheres-2, the amount of water is specifically 10, 15, 20, 25, 30, 35, 40, 45, 49, 50 mL.

[0061] In some embodiments of the present invention, more preferably, at least one of the following (1)-(2) is included:

[0062] (1) In step 1), the dispersion treatment temperature is 25-55°C and the time is 0.5-3h;

[0063] (2) In step 3), the temperature of the hydrothermal etching is 80-100° C. and the time is 1-24 hours.

[0064] In some embodiments of the present invention, more preferably, at least one of the following (1)-(4) is included:

[0065] (1) In step 1), the volume mass ratio of the alcohol dispersant, water, the first emulsifier, and the first silicon source is (1-200) mL: (5-100) mL: (0.1-10) mg: (0.02-10) g;

[0066] (2) In step 1), the mass ratio of the first emulsifier to the first silicon source is (0.2-2) mg:(0.01-5) g;

[0067] (3) In step 2), the mass ratio of the second emulsifier to the second silicon source is (0.1-2) mg: (0.02-10) g;

[0068] (4) The mass ratio of the first silicon source to the second silicon source is 1:(0.5-5), specifically 1:1, 1:1.5, 1:2 or 1:2.5; the unit is gram (g).

[0069] In a specific embodiment of the method of the present invention, the preparation method of the double-shell hollow silica microspheres of the present invention can be prepared by at least one of the following preparation steps: step 1) is the following step 1a), step 2) is the following step 2a), and step 3) is the following step 3a), but is not limited thereto:

[0070] 1a) adjusting the reaction solvent to be alkaline with an alkaline regulator, adding a first emulsifier to the alkaline reaction solvent and performing a dispersion treatment, and then adding a first silicon source to react to obtain a reaction solution containing solid silica microspheres-1 (S-1);

[0071] 2a) adding a second emulsifier to the reaction solution and stirring and mixing, then adding a second silicon source to react, centrifuging, washing, and drying to obtain solid silica microspheres-2 (S-2);

[0072] 3a) The solid silica microspheres-2 (S-2) are placed in water for heating reaction by hydrothermal etching.

[0073] Wherein, the alkaline reaction solvent includes an alcohol dispersant and water; and

[0074] The first emulsifier and the second emulsifier are each independently selected from at least one of C12-C22 alkyl trimethyl ammonium chloride, C12-C22 alkyl trimethyl ammonium bromide and C12-C22 alkyl trimethyl ammonium p-toluenesulfonate.

[0075] More preferably, the step 1a) is specifically as follows: the alkaline regulator is at least one of alkali metal hydroxide, urea, ammonia water and triethanolamine.

[0076] More preferably, in step 2a), the drying temperature is 80-120°C, the stirring temperature is 25-55°C, and the time is 0.1-4h; the detergent used for washing contains at least one of ethanol, methanol, ethylene glycol, propanol, isopropanol, n-butanol, tert-butanol, and isopentanol; and the detergent is preferably anhydrous alcohol.

[0077] More preferably, the alkali metal hydroxide is at least one of potassium hydroxide, sodium hydroxide and lithium hydroxide.

[0078] Preferably, in step 3a), the first emulsifier and the second emulsifier are each independently selected from at least one of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltrimethylammonium p-toluenesulfonate, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium p-toluenesulfonate, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, octadecyltrimethylammonium p-toluenesulfonate, eicosyltrimethylammonium chloride, eicosyltrimethylammonium bromide, eicosyltrimethylammonium p-toluenesulfonate, behenyltrimethylammonium chloride, behenyltrimethylammonium bromide and behenyltrimethylammonium p-toluenesulfonate.

[0079] More preferably, in step 3a), the first emulsifier and the second emulsifier are each independently selected from at least one of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide and cetyltrimethylammonium p-toluenesulfonate.

[0080] More preferably, in step 3a), the temperature of the hydrothermal etching is 80-100° C. and the time is 1-24 h.

[0081] Compared with the prior art, the present invention has the following beneficial effects:

[0082] The present invention provides a double-shell hollow silica microsphere, which has the advantages of good sphericity, narrow particle size distribution, diverse performance and adjustable performance. Compared with the existing single-layer core-shell hollow silica microspheres, the double-shell hollow silica microspheres of the present invention have significantly improved performance. For example, when used on light diffusion plates, it can further meet the requirements of high transmittance, high haze and good diffusion of light diffusers such as thinning of lighting devices, reduced absorbance and thinning of diffusion layers; for example, when used in cosmetics, it can be used as a functional powder with high oil absorption, soft focus and other effects; for example, it can be used as a lightweight filler in plastic, resin and other substrates to prepare lightweight composite materials; for example, when used in electronic materials, it can be used as a functional powder with high purity, low dielectric properties and other effects; for example, it can also be used in thermal insulation materials, catalytic products, porous carriers, sustained-release drug carriers and other aspects.

[0083] The present invention prepares double-shell hollow silica microspheres by a self-template method and a simple and effective selective etching strategy. Compared with the existing technology for preparing multi-layer hollow microspheres, the solid silica microspheres grown by the two-step sol-gel method realize the transformation from solid to double-shell structure through a one-step normal pressure (about 100 kPa) low temperature (<100°C) hydrothermal treatment. No corrosive etchant is required during the etching process, and the participation of high-pressure and high-temperature hydrothermal reactor is omitted, so it is energy-efficient, efficient and environmentally friendly. The preparation method of the present invention can obtain a hollow structure without calcination, so it can be used to construct double-shell hollow silica microspheres with organic groups.

[0084] The double-shell structure hollow silica microspheres of the present invention have the characteristics of high purity, do not contain or only contain a small amount of impurity elements or ions, and therefore, can be applied to electronic materials. When the double-shell structure hollow silica microspheres of the present invention are used to prepare electronic materials, low dielectric medium air can be introduced into the electronic materials due to their own hollow structure and hollow structure, thereby giving good dielectric properties (i.e., reducing the dielectric properties of the electronic materials) to obtain low dielectric materials. The double-shell structure, as well as the inner core layer and outer shell layer of a specific thickness improve the structural stability of the double-shell structure hollow silica microspheres, and the specific small-sized mesopores on the inner core layer and the outer shell layer are conducive to further improving the strength of the inner core layer and the outer shell layer, thereby enhancing the structural stability of the double-shell structure hollow silica microspheres, more conducive to resisting the invasion of external forces, and ultimately being able to better maintain its low dielectric properties and processability. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 This is a diagram illustrating the preparation process of double-shell hollow silica microspheres.

[0086] Figure 2 This is a schematic structural diagram of a double-shell hollow silica microsphere in Example 1, wherein an inner core layer 1, an outer shell layer 2, a double-shell structure 3, a hollow structure 4, and a hollow structure 5.

[0087] Figure 3 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment in Example 1, Figure a is the TEM image of solid silica microsphere-1 (S-1), Figure b1 is the TEM image of solid silica microsphere-2 (S-2), and Figures b2-b3 are TEM images of double-layer shell structure hollow silica microspheres (HS-2).

[0088] Figure 4 Figure 1 is the N2 adsorption-desorption isotherm diagram of the double-shell hollow silica microspheres in Example 1 and its corresponding BJH pore size distribution diagram. Figure a is the N2 adsorption-desorption isotherm diagram of the double-shell hollow silica microspheres, and Figure b is the BJH pore size distribution diagram of the double-shell hollow silica microspheres.

[0089] Figure 5 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment of Example 2 and Comparative Example 1-2, Figures a1, b1 and c1 are TEM images of solid silica microsphere-1 (S-1) of Comparative Example 1, Example 2 and Comparative Example 2, respectively, Figures a2, b2 and c2 are TEM images of solid silica microsphere-2 (S-2) of Comparative Example 1, Example 2 and Comparative Example 2, respectively, and Figures a3, b3 and c3 are TEM images of double-shell structured hollow silica microspheres (HS-2) of Comparative Example 1, Example 2 and Comparative Example 2, respectively.

[0090] Figure 6 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment of Examples 3-4 and Comparative Examples 3-4, Figures a1, b1, c1 and d1 are TEM images of solid silica microsphere-1 (S-1) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, Figures a2, b2, c2 and d2 are TEM images of solid silica microsphere-2 (S-2) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, Figures a3, b3, c3 and d3 are TEM images of double-shell hollow silica microspheres (HS-2) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, respectively; "E / W" in the figures represents the alcohol-water ratio.

[0091] Figure 7 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment in Example 1 and Example 5, Figure a1 and b1 are TEM images of solid silica microsphere-1 (S-1) in Example 1 and Example 5, respectively, Figure a2 and b2 are TEM images of solid silica microsphere-2 (S-2) in Example 1 and Example 5, respectively, and Figure a3 and b3 are TEM images of double-shell structured hollow silica microspheres (HS-2) in Example 1 and Example 5, respectively.

[0092] Figure 8 TEM images of the double-shell hollow silica microspheres (HS-2) of Examples 1 and 6-7, Figure a is the TEM image of the double-shell hollow silica microspheres (HS-2) of Example 6, the upper right inset in Figure a is the corresponding local enlarged image, Figure b is the TEM image of the double-shell hollow silica microspheres (HS-2) of Example 7, and Figure c is the TEM image of the double-shell hollow silica microspheres (HS-2) of Example 1. DETAILED DESCRIPTION

[0093] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0094] Example 1

[0095] This embodiment provides a double-shell hollow silica microsphere, such as Figure 1 As shown, the preparation method comprises the following steps:

[0096] 1) First, 25 mL of anhydrous ethanol and 50 mL of deionized water were added in sequence as reaction solvents in a 250 mL single-mouth bottle, and then 1 mL of 0.12 mol / L ammonia water (alkaline regulator) was added dropwise to adjust the solution to pH = 9.0, 145 mg of hexadecyltrimethylammonium bromide (CTAB, the first emulsifier) ​​was added, and the solution was placed in a 35° C. constant temperature water bath, stirred at 800 rpm for 0.5 h for ultrasonic dispersion treatment, and then 1 g of tetraethyl orthosilicate (TEOS, the first silicon source) was added, and the reaction was carried out at 35° C. for 3 h to obtain solid silica microspheres-1 (S-1);

[0097] 2) Then, a silica layer is further grown on the solid silica microsphere-1 (S-1). The general operation steps are as follows: 145 mg of hexadecyltrimethylammonium bromide (second emulsifier) ​​is added to the reaction solution containing the solid silica microsphere-1 (S-1), and after stirring at 35° C. for 0.5 h, 2 g of tetraethyl orthosilicate (second silicon source) is added, and the reaction is continued at 35° C. for 3 h to obtain a reaction solution containing solid silica microsphere-2 (S-2), and the reaction solution is centrifuged (8000 rpm, 5 min), and the obtained precipitate is washed three times by centrifugation with anhydrous ethanol, and dried in a 50° C. forced air drying oven to constant weight to obtain solid silica microsphere-2 (S-2);

[0098] 3) 50 mg of solid silica microspheres-2 (S-2) were redispersed in 50 mL of water and placed in a 90°C constant temperature water bath for stirring and reaction for 3 h for hydrothermal etching. After cooling to room temperature, the product was collected by centrifugation to obtain double-shell hollow silica microspheres (HS-2), the structural schematic of which is shown in FIG. Figure 2 shown; specifically:

[0099] The double-shell structure hollow silica microspheres are spherical bodies comprising an inner core layer (1) and an outer shell layer (2), wherein the inner core layer (1) and the outer shell layer (2) are both spherical bodies, and the inner core layer (1) and the outer shell layer (2) form a double-shell structure (3), wherein the inner core layer (1) is located inside the outer shell layer (2), the interior of the inner core layer (1) is a hollow structure (4), and between the inner core layer (1) and the outer shell layer (2) is a hollow structure (5), wherein the synthetic raw material of the inner core layer (1) contains a first silicon source, and the synthetic raw material of the outer shell layer (2) contains a second silicon source.

[0100] Examples 2-7 and Comparative Examples 1-4

[0101] Examples 2-7 and Comparative Examples 1-4 provide different double-shell hollow silica microspheres and preparation methods thereof. The differences in the experimental conditions between Examples 2-7 and Comparative Examples 1-4 and Example 1 are specifically described in Table 1, and the rest are consistent with Example 1:

[0102] Table 1 Experimental conditions of Examples 1-7 and Comparative Examples 1-4

[0103]

[0104]

[0105] In the above table, "alcohol-water ratio" refers to the volume ratio of anhydrous ethanol and deionized water in step 1); "pH value" refers to the pH value of the solution in step 1) after adjusting with 0.12 mol / L ammonia water; "synthesis two-step reaction temperature" refers to the temperature of the reaction of adding the first silicon source in step 1) and the temperature of the reaction of adding the second silicon source in step 2), and the two are the same; "hydrothermal etching water volume" refers to the amount of water used in step 3).

[0106] Sample characterization

[0107] Figure 2 Schematic diagram of the structure of the double-shell hollow silica microspheres in Example 1. Figure 2 It can be seen that the double-shell structure hollow silica microspheres prepared by the present invention are spherical bodies including an inner core layer (1) and an outer shell layer (2), wherein the inner core layer (1) and the outer shell layer (2) are both spherical bodies, and the inner core layer (1) and the outer shell layer (2) form a double-shell structure (3), wherein the inner core layer (1) is located inside the outer shell layer (2), the inner core layer (1) is a hollow structure (4), and the inner core layer (1) and the outer shell layer (2) are a hollow structure (5), wherein the synthetic raw material of the inner core layer (1) contains a first silicon source, and the synthetic raw material of the outer shell layer (2) contains a second silicon source. Moreover, the hollow structure (4) and the hollow structure (5) are both formed by a hydrothermal etching reaction.

[0108] Figure 3 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment in Example 1, Figure a is a TEM image of solid silica microsphere-1 (S-1), Figure b1 is a TEM image of solid silica microsphere-2 (S-2), and Figures b2-b3 are TEM images of double-shell hollow silica microspheres (HS-2). Figure 3 It can be seen from a that the solid silica microspheres-1 (S-1) prepared in step 1) using the first emulsifier and the first silicon source have a uniform spherical shape and a regular morphology. It can be seen from the measurement that the average diameter of S-1 is 300nm. Figure 3 b1 shows that in step 2), the second emulsifier and the second silicon source are used to grow the solid silica microsphere-1 (S-1) with an average diameter of 300 nm into the solid silica microsphere-2 (S-2) with an average diameter of 380 nm. Figure 3b2-3b3 It can be seen that after hydrothermal etching treatment, solid silica microsphere-2 (S-2) obtained a product with a good double-layer hollow structure, a double-layer shell structure hollow silica microsphere (HS-2). After measurement, the average diameter and average thickness of the outer shell layer of HS-2 obtained after hydrothermal treatment were 380nm and 15nm, respectively, and the particle size was consistent with that of solid silica microsphere-2 (S-2); the average diameter and average thickness of the inner core layer were 300nm and 25nm, respectively, which was the same as the average diameter of solid silica-1 (S-1) prepared by the first emulsifier and the first silicon source in step 1). The above results show that the solid silica microsphere-2 (S-2) formed by adding TEOS and CTAB twice forms a hollow shell with a certain diameter after hydrothermal treatment, and the distance between the inner core layer and the outer shell layer is 25nm.

[0109] In addition, in the double-shell hollow silica microspheres (HS-2) prepared in Example 1, the distance between the inner core layer and the outer shell layer is 65 nm, and the ratio of the average diameters of the inner core layer to the outer shell layer is 1:1.27.

[0110] Figure 4 The N2 adsorption-desorption isotherms of the double-shell hollow silica microspheres in Example 1 and their corresponding BJH pore size distribution diagrams are shown in Figure a. Figure a is the N2 adsorption-desorption isotherms of the double-shell hollow silica microspheres, and Figure b is the BJH pore size distribution diagram of the double-shell hollow silica microspheres. Figure 4 It can be seen from a that the N2 adsorption-desorption isotherm belongs to type IV and has a typical H3 type hysteresis loop. The existence of the hysteresis loop indicates that there are multiple mesopores distributed on the inner core layer and the outer shell layer of the double-shell hollow silica microspheres. The calculated BET specific surface area of ​​the double-shell hollow silica microspheres is as high as 723.4 m 2 / g. From Figure 4 b shows that the pore size of the mesopores is mainly concentrated in the range of 2-5 nm, and the pore volume is 0.97 cm 3 / g. The existence of these mesoporous structures is conducive to the adsorption and release of guest molecules.

[0111] Example 2 and Comparative Examples 1-2 study the effect of the pH of the reaction system on the morphology of hollow silica microspheres with double-shell structures. Although the hydrolysis reaction of TEOS can be carried out under acidic or alkaline conditions, the hydrolysis and polycondensation rates of TEOS molecules are significantly different under different pH conditions. Therefore, changing the pH of the reaction system is likely to cause differences in the structure of the silica microspheres, as follows:

[0112] Figure 5TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment of Example 2 and Comparative Example 1-2, Figures a1, b1 and c1 are TEM images of solid silica microsphere-1 (S-1) of Comparative Example 1, Example 2 and Comparative Example 2, Figures a2, b2 and c2 are TEM images of solid silica microsphere-2 (S-2) of Comparative Example 1, Example 2 and Comparative Example 2, Figures a3, b3 and c3 are TEM images of double-shell hollow silica microspheres (HS-2) of Comparative Example 1, Example 2 and Comparative Example 2, respectively. Figure 5 It can be seen that when the solution in step 1) is adjusted with ammonia water to increase the pH value of the reaction system from 8.0 to 10.0, the average diameter of the solid silica microsphere-1 (S-1) increases from 310 nm to 400 nm and then remains unchanged.

[0113] In addition, from Figure 5 It can be clearly observed that with the increase of pH value, the solid silica microspheres-1 (S-1) are increasingly aggregated. Figure 5 It can be seen from Comparative Example 1 of a3 that when the pH value of the reaction system is 8.0, after the solid silica microsphere-2 (S-2) is subjected to hydrothermal etching, no double-shell hollow silica microspheres are obtained. It is only clearly observed that the surface of the silica microspheres after the hydrothermal treatment becomes rough. Figure 5 b3 and Figure 5 c3 shows that when the pH of the reaction system is 9.3 and 10.0, after hydrothermal etching treatment, double-shell hollow silica microspheres with hollow structure and hollow structure are obtained; but under the condition that the pH of the reaction system is 10.0, due to the serious agglomeration of microspheres before hydrothermal etching treatment, HS-2 did not obtain a regular spherical morphology after hydrothermal etching treatment.

[0114] The above results can be easily explained by the differences in the hydrolysis, polycondensation and depolymerization rates of TEOS under different pH conditions. Specifically:

[0115] When the reaction system is under weak alkaline conditions (pH = 8.0), the hydrolysis rate of TEOS is slow, while the condensation reaches its maximum value. At this time, the oligomers of TEOS hydrolysis rapidly condense in a short time. Therefore, there is basically no difference in the condensation degree between the inside and the outer shell of the obtained microspheres. Hot water etching treatment can only make the surface of the microspheres rough, but cannot change the solid situation inside the microspheres.

[0116] When the pH value of the reaction system increases to 9.3, the TEOS condensation rate decreases. Although the TEOS condensation rate is still greater than the TEOS hydrolysis rate, the TEOS depolymerization rate is higher than the condensation and hydrolysis rates. Therefore, the condensation degree of the internal core formed in a short time is lower than the condensation degree of the external shell under a longer reaction time. There is a certain structural difference between the two, which leads to the fact that in Example 2, hollow silica microspheres with a double-shell structure and a hollow structure are obtained after hydrothermal etching treatment.

[0117] When the pH value of the reaction system continues to increase to 10.0, the TEOS condensation rate is greatly reduced, the TEOS hydrolysis rate is greater than the TEOS condensation rate, and the condensation degree of the inner core is lower than that of the outer shell. Therefore, hollow structures and hollow structures can be obtained by hydrothermal etching. However, at this time, due to the rapid hydrolysis rate of TEOS, the content of silanol on the surface of the microspheres increases, and serious agglomeration occurs, which makes HS-2 unable to obtain a regular spherical morphology.

[0118] Based on the above experimental results and the relevant data of Example 1, it can be seen that if one wants to obtain double-shell hollow silica microspheres with good morphology, the optimal pH value of the reaction system should be controlled at 9.0-9.5.

[0119] The preliminary experimental results of the present invention show that when silica microspheres are prepared by the sol-gel method, the ethanol content in the reaction system has a great relationship with the reaction rate of TEOS. Therefore, Examples 3-4 and Comparative Examples 3-4 study the effect of the volume ratio of alcohol dispersant and water (alcohol-water ratio) on the morphology of hollow silica microspheres with a double-shell structure.

[0120] Figure 6 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment of Examples 3-4 and Comparative Examples 3-4; Figures a1, b1, c1 and d1 are TEM images of solid silica microsphere-1 (S-1) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, respectively; Figures a2, b2, c2 and d2 are TEM images of solid silica microsphere-2 (S-2) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, respectively; Figures a3, b3, c3 and d3 are TEM images of double-shell hollow silica microspheres (HS-2) of Comparative Example 3, Example 3, Example 4 and Comparative Example 4, respectively; "E / W" in the figure represents the alcohol-water ratio. Figure 6It can be seen from a1, 6b1, 6c1, and 6d1 that with the decrease of ethanol content, that is, the decrease of alcohol-water ratio, the average diameter of solid silica microsphere-1 (S-1) gradually decreases, from 570nm to 150nm. This is because when the alcohol-water ratio in the reaction system is large, the ethanol content is high, which has a great inhibitory effect on the hydrolysis reaction of TEOS. Therefore, after TEOS is added, the number of nuclei is small. As the reaction time increases, it slowly becomes a silica microsphere with a larger average diameter. When the alcohol-water ratio in the system is small, the ethanol content is low. After TEOS is added, it is rapidly hydrolyzed and a large number of nuclei are formed. At this time, since the amount of TEOS remains unchanged, the average diameter of the formed microspheres is smaller. Since solid silica microsphere-2 (S-2) is further grown with solid silica microsphere-1 (S-1) as a seed, the particle size change trends of the two are consistent. Therefore, from Figure 6 It can be seen from a2, 6b2, 6c2, and 6d2 that the average particle size of solid silica microspheres-2 (S-2) decreased from 860 nm to 189 nm.

[0121] from Figure 6 It can be observed in a3 that when the alcohol-water volume ratio is 2, only a single-shell hollow structure can be obtained after hydrothermal etching of solid silica microsphere-2 (S-2), and no double-shell hollow structure is obtained. This is because when the alcohol-water ratio in the reaction system is large, the ethanol content is high, the TEOS hydrolysis rate is very slow, and the silica microspheres grow slowly. Therefore, the difference in the internal and external condensation degrees of the generated solid silica microsphere-1 (S-1) is small, and a hollow structure is obtained after hydrothermal etching, but the inner core layer is thicker, which is 140nm. By continuing to add CTAB and TEOS to continue to grow the shell layer on the basis of solid silica microsphere-1 (S-1), since the reaction medium is the same, the formation of the second layer of silica is the same as that of the solid silica microsphere-1 (S-1), that is, the gradient difference between the internal and surface condensation degrees is very small (see Figure 6 a3), and the solid silica microsphere-1 (S-1) obtained in the first step of the reaction continued to react when growing the second layer of silica layer, and the internal condensation degree became higher. Therefore, the solid silica microsphere-2 (S-2) did not obtain a hollow structure after hydrothermal etching, but it can be clearly observed that the surface layer became loose, and the interior was still a solid structure. The particle size of the internal solid structure was measured to be consistent with the particle size of the solid silica microsphere-1 (S-1), indicating that during the growth of the second layer of silica shell, the parent solid silica microsphere-1 (S-1) continued to react, and the structure became denser and the condensation degree was higher. Therefore, after hydrothermal etching, only the newly generated second layer of silica structure became loose.

[0122] from Figure 6It can be observed in b2 and 6b3 that when the alcohol-water volume ratio is reduced to 1, single-shell and double-shell hollow structures can be observed, which indicates that a gradient difference begins to appear between the inner and outer condensation degrees of the microspheres, the inner condensation degree is smaller, and the hydrothermal etching is preferentially carried out from the inside.

[0123] from Figure 6 It can be observed in c2 and 6c3 that when the alcohol-water volume ratio drops to 0.4, the agglomeration phenomenon is alleviated and the hollow structure of the microspheres becomes clearer.

[0124] from Figure 6 It can be observed in d2 and 6d3 that when the alcohol-water volume ratio finally drops to 0.3, it can be seen that only a single-shell hollow structure is obtained at this time. Because the hydrolysis rate is too fast at this time, the added TEOS quickly self-nucleates to generate nanoparticles instead of growing on the already formed solid silica microsphere-1 (S-1).

[0125] Based on the above experimental results, it can be seen that the ethanol content in the system has a great influence on the morphology of the double-shell structured hollow silica microspheres. When the volume ratio of the alcohol dispersant and water (alcohol-water ratio) is 0.4-1, the obtained double-shell structured hollow silica microspheres have a better morphology.

[0126] Examples 1 and 5 study the effects of the reaction temperature of adding the first silicon source in step 1) and the reaction temperature of adding the second silicon source in step 2) (synthesis two-step reaction temperature) on the morphology of double-shell hollow silica microspheres.

[0127] Figure 7 TEM images of single-layer and double-layer silica microspheres before and after hydrothermal treatment in Example 1 and Example 5, Figures a1 and b1 are TEM images of solid silica microsphere-1 (S-1) in Example 1 and Example 5, Figures a2 and b2 are TEM images of solid silica microsphere-2 (S-2) in Example 1 and Example 5, and Figures a3 and b3 are TEM images of double-shell hollow silica microspheres (HS-2) in Example 1 and Example 5, respectively. Figure 7It can be seen that when the reaction temperature increases from 35°C to 50°C, the average diameters of solid silica microspheres-1 (S-1) and solid silica microspheres-2 (S-2) both increase, with the average diameter of solid silica microspheres-1 (S-1) increasing from 294nm to 330nm, and the average diameter of solid silica microspheres-2 (S-2) increasing from 462nm to 566nm. Under 50°C, the contrast difference of the hollow structure obtained after hydrothermal etching of solid silica microspheres-2 (S-2) is more obvious than that obtained under 35°C, indicating that as the temperature increases, the TEOS reaction speed accelerates, so the difference in the condensation degree between the inner and outer layers of the solid microspheres is greater, so the hydrothermal etching reaction is more complete and the hollow structure is more obvious. The solid silica microspheres-2 (S-2) obtained at 35°C and 50°C can obtain double-shell hollow silica microspheres (HS-2) after hydrothermal etching treatment, but the average diameter of the double-shell hollow silica microspheres (HS-2) obtained at 50°C is larger, which is 560nm.

[0128] In summary, the particle size of double-shell hollow silica microspheres (HS-2) can be adjusted by adjusting the preparation temperature of solid microspheres.

[0129] Examples 1 and 6-7 study the effect of the solid-to-liquid ratio of solid silica microspheres-2 and water (amount of water for hydrothermal etching) on ​​the morphology of hollow silica microspheres with double-shell structures.

[0130] Figure 8 TEM images of double-shell hollow silica microspheres (HS-2) of Examples 1 and 6-7, Figure a is a TEM image of double-shell hollow silica microspheres (HS-2) of Example 6, the upper right illustration in Figure a is a corresponding partial enlarged image, Figure b is a TEM image of double-shell hollow silica microspheres (HS-2) of Example 7, and Figure c is a TEM image of double-shell hollow silica microspheres (HS-2) of Example 1. Regarding the solid-liquid ratio of solid silica microspheres-2 and water, when the solid silica microspheres-2 (S-2) in step 3) are fixed to 50 mg, from Figure 8 It can be seen that as the amount of water for hydrothermal etching increases from 10 mL to 30 mL and then to 50 mL, that is, the solid-liquid ratio of S-2 and water decreases from 50:10 to 50:30 and then to 50:50, the inner core layer of the double-shell structure hollow silica microspheres (HS-2) gradually becomes thinner; when the amount of water for hydrothermal etching is 50 mL, that is, the solid-liquid ratio of S-2 and water is 50:50, the thickness of the inner core layer is very thin, only about a dozen nanometers, and even some of the inner core layers of the microspheres have been completely etched, leaving only a single-layer structure.

[0131] In summary, the thickness of the inner core layer of the double-shell hollow silica microspheres (HS-2) can be controlled by adjusting the amount of hydrothermal etching water relative to the sample.

[0132] The elemental composition of the double-shell hollow silica microspheres in Example 1 was analyzed by ICP, and the test results are shown in the following table:

[0133] Table 2 ICP test results of double-shell hollow silica microspheres in Example 1

[0134]

[0135]

[0136] Note: “ND” in the table means the tested element was not detected.

[0137] As can be seen from Table 2, the double-shell hollow silica microspheres of the present invention have the characteristics of high purity, and contain no or only a small amount of impurity elements or ions. Therefore, the double-shell hollow silica microspheres of the present invention can be applied to electronic materials.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A double-shell hollow silica microsphere, characterized in that: The double-shell structure hollow silica microspheres are spherical bodies including an inner core layer and an outer shell layer, the inner core layer and the outer shell layer are both spherical bodies, the inner core layer and the outer shell layer form a double-shell structure, the inner core layer is located inside the outer shell layer, the inner core layer is a hollow structure, and the inner core layer and the outer shell layer are a hollow structure, the thickness of the inner core layer is 10-100nm; the thickness of the outer shell layer is 10-50nm, and a plurality of mesopores are distributed on the inner core layer and the outer shell layer, and the pore size of the mesopores is 1-10nm.

2. The double-shell hollow silica microsphere according to claim 1, characterized in that: The synthetic raw material of the inner core layer contains a first silicon source, and the synthetic raw material of the outer shell layer contains a second silicon source; The first silicon source and the second silicon source are independently selected from at least one of the compounds represented by the general formula R1Si(OR4)3, the compounds represented by the general formula R2R3Si(OR4)2 and the compounds represented by the general formula Si(OR4)4, wherein R4 is a C1-6 alkyl group; R1, R2 and R3 are independently selected from hydrogen, substituted or unsubstituted C1-6 alkyl, substituted or unsubstituted C2-6 alkenyl, substituted or unsubstituted C2-6 alkynyl, substituted or unsubstituted C6-12 aryl; the substitution refers to substitution by at least one substituent selected from amino, amino substituted with C1-6 aminoalkyl, C1-6 alkoxy substituted with C1-6 aminoalkyl, C1-6 alkoxy substituted with oxygen and C1-6 hydrocarbon acyloxy substituted with oxygen.

3. The double-shell hollow silica microsphere according to claim 2, characterized in that: Including at least one of the following (1)-(7): (1) The first silicon source and the second silicon source are the same or different; (2) Both the first silicon source and the second silicon source have hydrothermal etching reactivity; (3) The first silicon source is a compound represented by the general formula Si(OR4)4; (4) The second silicon source is a compound represented by the general formula Si(OR4)4; (5) The compound represented by the general formula R1Si(OR4)3 is at least one of C6H5Si(OCH3)3, CH3Si(OCH3)3, methacryloxypropyltrimethoxysilane, glycidyloxypropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropyloxy)propyltrimethoxysilane, γ-(methacryloxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, and methyltriethoxysilane; (6) The compound represented by the general formula R2R3Si(OR4)2 is dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiacetoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, di-n-butyldimethoxysilane, diisobutyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, methylvinyldimethoxysilane, divinyldiethoxysilane, 3-methyl At least one of acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-mercaptopropylmethyldimethoxysilane or 3-isocyanatepropylmethyldiethoxysilane; (7) The compound represented by the general formula Si(OR4)4 is at least one of tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane or tetraacetoxysilane.

4. The double-shell hollow silica microsphere according to claim 1, characterized in that: Including at least one of the following (1)-(5): (1) The average diameter of the inner core layer is 50-1000 nm; (2) The average diameter of the outer shell layer is 0.1-10 μm; (3) The distance between the inner core layer and the outer shell layer is 5-100 nm; (4) The ratio of the average diameter of the inner core layer to the outer shell layer is 1:(1.1-10); (5) The specific surface area of ​​the double-shell hollow silica microspheres is 500 to 2000 m 2 g -1 .

5. The method for preparing the double-shell hollow silica microspheres according to any one of claims 1 to 4, characterized in that: The steps include: 1) adding a first emulsifier to an alkaline reaction solvent and performing a dispersion treatment, and then adding a first silicon source to react to obtain a reaction solution containing solid silica microspheres-1; 2) firstly mixing the second emulsifier into the reaction solution, and then adding the second silicon source to react to obtain solid silica microspheres-2; 3) hydrothermally etching the solid silica microsphere-2 to obtain a double-shell hollow silica microsphere; Wherein, the reaction solvent includes an alcohol dispersant and water; The first emulsifier and the second emulsifier are independently selected from at least one of C12-C22 alkyl trimethyl ammonium chloride, C12-C22 alkyl trimethyl ammonium bromide and C12-C22 alkyl trimethyl ammonium p-toluenesulfonate.

6. The preparation method according to claim 5, characterized in that: Including at least one of the following (1)-(6): (1) In step 1), the volume ratio of the alcohol dispersant to water is 0.4-1.2; (2) In step 1), the pH of the alkaline reaction solvent is 8.5-9.5; (3) the temperature at which the first silicon source is added to react in step 1) is the same as or different from the temperature at which the second silicon source is added to react in step 2); (4) In step 1), the temperature for adding the first silicon source to react is 25-55° C.; (5) In step 2), the temperature for adding the second silicon source to react is 25-55° C.; (6) In step 3), in the hydrothermal etching, the solid-to-liquid ratio of solid silica microspheres-2 and water is (20-50) mg: (10-50) mL.

7. The preparation method according to claim 6, characterized in that: Including at least one of the following (1)-(6): (1) In step 1), the volume ratio of the alcohol dispersant to water is 0.4-1; (2) In step 1), the alcohol dispersant is at least one of methanol, ethanol, ethylene glycol, propanol, isopropanol, n-butanol, tert-butanol, and isoamyl alcohol; (3) In step 1), the pH of the alkaline reaction solvent is 9.0-9.5; (4) In step 1), the temperature of adding the first silicon source to react is 30-50° C. and the time is 0.5-3 h; (5) In step 2), the temperature of adding the second silicon source to react is 30-50° C. and the time is 0.5-3 h; (6) In step 3), in the hydrothermal etching, the solid-to-liquid ratio of solid silica microspheres-2 and water is 50 mg:(10-50) mL.

8. The preparation method according to claim 5, characterized in that: Include at least one of the following (1)-(2): (1) In step 1), the dispersion treatment temperature is 25-55°C and the time is 0.5-3h; (2) In step 3), the temperature of the hydrothermal etching is 80-100° C. and the time is 1-24 hours.

9. The preparation method according to claim 5, characterized in that: Including at least one of the following (1)-(4): (1) In step 1), the volume mass ratio of the alcohol dispersant, water, the first emulsifier, and the first silicon source is (1-200) mL: (5-100) mL: (0.1-10) mg: (0.02-10) g; (2) In step 1), the mass ratio of the first emulsifier to the first silicon source is (0.2-2) mg:(0.01-5) g; (3) In step 2), the mass ratio of the second emulsifier to the second silicon source is (0.1-2) mg: (0.02-10) g; (4) The mass ratio of the first silicon source to the second silicon source is 1:(0.5-5).

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