Multilayered silicon dioxide nanoparticles, method for preparing the same, antireflection film and solar cell

Abstract

The application belongs to the field of solar cells, and discloses a kind of multilayer silicon dioxide nanoparticles and its preparation method, anti-reflection film and solar cell.The multilayer silicon dioxide nanoparticles include hollow core, silicon dioxide mesoporous intermediate layer and silicon dioxide coating shell.The preparation method of the application is simple, the reaction condition is mild and non-toxic, the efficiency is high, the template agent is removed completely, the porosity of the synthesized multilayer silicon dioxide nanoparticles is high, the light transmission effect is good, the dispersibility is good, and the mechanical strength is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solar cells, and particularly relates to a multilayer silicon dioxide nanoparticle, a preparation method thereof, an antireflection film and a solar cell. BACKGROUND

[0002] Porous silica nanoparticles are widely used in antireflection film materials due to their excellent mechanical strength and adjustable porosity. The sol-gel method for synthesizing porous silica nanoparticles is simple and low in cost. At present, the pore forming method of porous silica in the sol-gel method is mainly the template method. First, a template agent is introduced into a silicon source system, and the template agent is generally an organic polymer or an organic surfactant. In the process of hydrolysis of the silicon source into silica sol, the template is coated inside the silicon particles to form a bundle or a sphere. Then, the template agent is removed after the silicon source is hydrolyzed. The removal method of the template agent is mainly calcination or water washing. However, calcination can cause oxidation and blackening of the organic matter, leaving carbon black inside the silicon particles. In the water washing process, the template agent is difficult to be completely soaked and dissolved due to the dense structure of the silicon particles. The effects of the two methods for removing the template are not ideal, and the pores inside the silica cannot be completely released, thereby affecting the light transmission effect of the antireflection film.

[0003] CN110217802B synthesizes an amphiphilic block copolymer pDMAEMA b pGMA, and uses the same as a template, so that the amphiphilic block copolymer can self-assemble into nanostructures with controllable size and shape in an aqueous solution, thereby providing a good template molecule for controlling the growth of SiO2 nanoparticles and the construction of uniform assemblies. Then, hollow mesoporous silica functional microspheres are synthesized by a one-step method at room temperature. The prepared hollow mesoporous silica functional microspheres have a large hollow cavity volume and a controllable size.

[0004] CN117585681A uses tetraethyl orthosilicate (TEOS) as a silicon source, and polyethyleneimine (PEI) and cetyltrimethylammonium bromide (CTAB) as structure directing agents for the hollow structure and mesoporous channels of silica microspheres, respectively. Hollow silica spheres are prepared by a one-step method, and finally, the template is completely removed by calcination in air to obtain hollow mesoporous silica spheres.

[0005] The template agent used in the hollow mesoporous silica prepared by the prior art has a complex and tedious synthesis process, a long synthesis period, and toxic organic solvents such as tetrahydrofuran, which are harmful to the environment and human body. Moreover, the template agent is removed by calcination process, which easily causes particle agglomeration and cannot be redispersed, and thus cannot be applied to antireflection film materials. SUMMARY

[0006] The present application aims at the above-mentioned problems existing in the prior art, and provides a multilayered silica nanoparticle, a preparation method thereof, an antireflection film and a solar cell. The multilayered silica nanoparticle of the present application has a template removal efficiency of almost 100%, and high mechanical strength, and can be applied to an antireflection film material.

[0007] Specifically, one aspect of the present application provides a multilayered silica nanoparticle, which comprises, from inside to outside, a hollow inner core, a mesoporous silica intermediate layer and a silica coating layer, and has a total porosity of 25-50%.

[0008] In one or more embodiments, the multilayered silica nanoparticle has a particle size of 80-120 nm.

[0009] In one or more embodiments, the multilayered silica nanoparticle has a silica coating layer with a thickness of 5-8 nm.

[0010] In one or more embodiments, the multilayered silica nanoparticle has a mesoporous silica intermediate layer with a thickness of 20-35 nm.

[0011] In one or more embodiments, the multilayered silica nanoparticle has a hollow inner core with a diameter of 30-70 nm.

[0012] In one or more embodiments, the multilayered silica nanoparticle has a specific surface area of 320-400 m 2 / g before the silica coating layer is coated.

[0013] In one or more embodiments, the multilayered silica nanoparticle has a mesopore size of 10-20 nm before the silica coating layer is coated.

[0014] In one or more embodiments, the multilayered silica nanoparticle has a porosity of 30-55% before the silica coating layer is coated.

[0015] In one or more embodiments, the multilayered silica nanoparticle does not contain a mesopore-forming agent and a hollow pore-forming agent.

[0016] Another aspect of the present application provides a method for preparing the multilayered silica nanoparticle according to any one of the embodiments of the present application, which comprises: dispersing a hollow silica nanoparticle in a mixed solvent of an alcohol solvent and water, adjusting the pH value of the solution to 7-14, adding a silicon source, and performing a reaction to form a silica coating layer on the surface of the hollow silica nanoparticle, thereby obtaining the multilayered silica nanoparticle; wherein the hollow silica nanoparticle comprises a hollow inner core and a mesoporous silica shell.

[0017] In one or more embodiments, the hollow silica nanoparticle has a particle size of 70-110 nm.

[0018] In one or more embodiments, the hollow silica nanoparticle has a hollow core with a diameter of 30-70 nm.

[0019] In one or more embodiments, the hollow silica nanoparticle has a mesoporous silica shell with a thickness of 20-35 nm.

[0020] In one or more embodiments, the hollow silica nanoparticle has a specific surface area of 320-400 m 2 / g.

[0021] In one or more embodiments, the hollow silica nanoparticle has a mesoporous pore size of 10-20 nm.

[0022] In one or more embodiments, the hollow silica nanoparticle has a porosity of 30-55%.

[0023] In one or more embodiments, the alcohol solvent is selected from C1-C4 alcohols.

[0024] In one or more embodiments, the alcohol solvent is ethanol.

[0025] In one or more embodiments, the volume ratio of alcohol solvent to water in the mixed solvent is (5-10):1.

[0026] In one or more embodiments, the silicon source is tetraethyl orthosilicate.

[0027] In one or more embodiments, the mass ratio of the silicon source to the hollow silica nanoparticle is 1:(0.3-1).

[0028] In one or more embodiments, the reaction temperature is 20-30°C.

[0029] In one or more embodiments, the reaction time is 5-8 h.

[0030] In one or more embodiments, the solution pH value is adjusted to 7-14 using ammonia water.

[0031] In one or more embodiments, the method for preparing the hollow silica nanoparticle comprises:

[0032] S1: dissolving a hollow pore-forming agent, a mesopore-forming agent, an initiator and a silicon source in a solvent, and reacting at 5-10°C to obtain a solution containing nanoparticles P0, wherein the nanoparticles P0 comprise a hollow pore-forming agent core and a silica surface layer, and the silica surface layer comprises mesopore channels and the mesopore-forming agent filled in the mesopore channels;

[0033] S2: removing the mesopore-forming agent in the mesopore channels of the nanoparticles P0 by centrifugal water washing to obtain nanoparticles P1;

[0034] S3: dispersing the nanoparticles P1 in water, adjusting the pH value of the solution to 1-1.5, then stirring at 60-70°C, and removing the hollow pore-forming agent by centrifugal water washing to obtain the hollow silica nanoparticles.

[0035] In one or more embodiments, in step S1, the hollow pore-forming agent is polyacrylic acid, and the relative molecular weight of the polyacrylic acid is preferably 3000-5000.

[0036] In one or more embodiments, in step S1, the mesopore-forming agent is hexadecyl trimethyl ammonium bromide and / or hexadecyl trimethyl ammonium chloride.

[0037] In one or more embodiments, in step S1, the initiator is ammonia.

[0038] In one or more embodiments, in step S1, the silicon source is tetraethyl orthosilicate.

[0039] In one or more embodiments, in step S1, the solvent is a mixture of an alcohol solvent and water.

[0040] In one or more embodiments, in step S1, the alcohol solvent is a C1-C4 alcohol.

[0041] In one or more embodiments, in step S1, the alcohol solvent is ethanol.

[0042] In one or more embodiments, in step S1, the particle size of the nanoparticles P0 is 70-110 nm.

[0043] In one or more embodiments, in step S1, the mass ratio of the hollow pore-forming agent, the mesopore-forming agent and the silicon source is 1:(0.5-1.5):(15-40).

[0044] In one or more embodiments, in step S1, the reaction time is 5-8 h.

[0045] In one or more embodiments, step S1 comprises the following steps:

[0046] S1-1: the hollow pore-forming agent, initiator and water are mixed uniformly, and then added to the alcohol solvent, stirred uniformly to obtain a first mixed solution;

[0047] S1-1: the mesoporous pore-forming agent is dissolved in water, and then added to the first mixed solution prepared in step S1-1 to obtain a second mixed solution;

[0048] S1-3: the silicon source is added to the second mixed solution, and the reaction is carried out at 5-10°C to obtain the solution containing the nanoparticles P0.

[0049] In one or more embodiments, in step S2, the water used for centrifugal water washing is ice water with a temperature of 0-5°C.

[0050] In one or more embodiments, in step S3, the stirring time is greater than or equal to 10h.

[0051] In one or more embodiments, in step S3, the stirring time is 10-12h.

[0052] Another aspect of the present application provides a multilayered silica nanoparticle prepared by the method of any one of the embodiments herein.

[0053] Another aspect of the present application provides an antireflection film comprising the multilayered silica nanoparticle prepared by any one of the embodiments herein.

[0054] Another aspect of the present application provides a solar cell comprising the antireflection film prepared by any one of the embodiments herein.

[0055] The present application has the following beneficial technical effects: the synthesis process of the present application is simple, the reaction conditions are mild, and the efficiency is high; the effect of completely removing the hollow-mesoporous silica nanoparticle template agent is achieved through simple centrifugal water washing; and after the template is removed, a layer of silica shell structure is coated on the surface of the hollow-mesoporous silica nanoparticle, so that the synthesized multilayered silica nanoparticle has good mechanical strength and can be used for the preparation of an antireflection film coating in a solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 The figure is a schematic diagram of the structure of the multilayered silica nanoparticle of the present application. DETAILED DESCRIPTION

[0057] In order for those skilled in the art to understand the characteristics and effects of the present application, the following is a general description and definition of the terms and phrases mentioned herein. Unless otherwise specified, all technical and scientific words used herein have their usual meanings understood by those skilled in the art of the present application, and in case of conflict, the definitions in the present specification shall prevail.

[0058] Theories and mechanisms described and disclosed herein, whether correct or not, should not be construed as limiting the scope of the present application, i.e., the present application can be practiced without regard to any particular theory or mechanism.

[0059] In the present application, the terms "comprising", "including", "containing", and the like, are inclusive, in the sense of "having at least", and should be construed as specifying the presence of stated features, integers, steps, or components, but not precluding the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0060] In the present application, all features, numerical values, amounts, contents and concentrations defined in the form of numerical value range or percentage range are merely for the sake of brevity and convenience. Therefore, the description of numerical value range or percentage range should be considered as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0061] In the present application, unless otherwise specified, the percentage refers to mass percentage, and the ratio refers to mass ratio.

[0062] In the present application, when describing embodiments or examples, it should be understood that they are not intended to limit the present application to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the described methods and materials included in the present application are covered within the scope of the present application.

[0063] In the present application, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present application.

[0064] The present application can completely remove the template of hollow-mesoporous silica nanoparticles by simple centrifugation and water washing. After removing the template, a layer of silica shell structure is coated on the surface of the hollow-mesoporous silica nanoparticles, which improves the mechanical strength of the nanoparticles. Therefore, the multi-layered silica nanoparticles in the present application can be applied to anti-reflective film materials.

[0065] The multi-layered silica nanoparticles of the present application can be prepared by a method comprising the following steps:

[0066] S1: a solution containing nanoparticles P0 is obtained by using polyacrylic acid (PAA) as a hollow pore-forming agent, cetyltrimethylammonium bromide (CTAB) or cetyltrimethylammonium chloride (CTAC) as a mesoporous pore-forming agent, ammonia as an initiator, tetraethyl orthosilicate as a silicon source, ethanol and water as solvents, and performing a reaction at 5-10 DEG C; the nanoparticles P0 comprise a polyacrylic acid core and a silicon dioxide surface layer, and the silicon dioxide surface layer comprises mesoporous channels and the mesoporous pore-forming agent filled in the mesoporous channels;

[0067] S2: the solution containing nanoparticles P0 obtained in step S1 is treated by a centrifugal water washing method to remove the mesoporous pore-forming agent in the mesoporous channels, and then the solvent is removed to obtain nanoparticles P1;

[0068] S3: the nanoparticles P1 obtained in step S2 are dispersed in water, the pH value of the solution is adjusted to 1-1.5 by adding an acid, and then stirring is performed at 60-70 DEG C; the polyacrylic acid is removed by a centrifugal water washing method to obtain nanoparticles P2;

[0069] S4: the nanoparticles P2 obtained in step S3 are dispersed in a mixed solvent of ethanol and water, ammonia is added to adjust the pH value of the solution to 7-14, and then tetraethyl orthosilicate is added to perform a reaction to form a silicon dioxide coating layer on the surface of the nanoparticles P2 to obtain multi-layer silicon dioxide nanoparticles.

[0070] In the present application, the water is preferably deionized water.

[0071] In step S1 of the present application, the particle size of the nanoparticles P0 is preferably 70-110 nm, for example, 71 nm, 72 nm, 73 nm, 74 nm, 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm.

[0072] In step S1 of the present application, the relative molecular weight of the polyacrylic acid can be 3000-5000, for example, 3500, 4000, 4500.

[0073] In step S1 of the present application, the mass ratio of the hollow pore-forming agent to the mesoporous pore-forming agent is preferably 1:(0.5-1.5), for example, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4.

[0074] In step S1 of the present application, the mass ratio of the hollow pore-forming agent to tetraethyl orthosilicate is preferably 1:(15-40), for example 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34, 1:35, 1:36, 1:37, 1:38, 1:39.

[0075] In step S1 of the present application, the reaction temperature is preferably 5-10℃, for example 6℃, 7℃, 8℃, 9℃. The present application controls the reaction in step S1 to be carried out in a low-temperature system, which is conducive to the formation of a large-pore mesoporous structure, thereby facilitating the dissolution of the hollow pore-forming agent PAA.

[0076] In step S2 of the present application, the water used for high-speed centrifugation is preferably ice water with a temperature of 0-5℃, for example 0℃, 1℃, 2℃, 3℃, 4℃, 5℃. Since the presence of surfactants increases the surface activity of silica nanoparticles, accelerates the gelation speed between particles and thus causes agglomeration, the use of ice water with a temperature lower than 5℃ in step S2 of the present application can effectively prevent nanoparticle agglomeration.

[0077] In step S3 of the present application, the acid used is a common Lewis acid, for example hydrochloric acid. In step S3 of the present application, the pH value of the solution is adjusted to 1-1.5 by adding acid, and heating and stirring in a strong acidic system is conducive to accelerating the dissolution of the hollow pore-forming agent PAA and achieving the effect of completely removing the pore-forming agent template.

[0078] In step S3 of the present application, the stirring temperature is controlled to be 60-70℃, which is conducive to the complete removal of polyacrylic acid and achieves the effect of completely removing the hollow pore-forming agent.

[0079] In step S4 of the present application, the volume ratio of ethanol to water in the mixed solvent can be (5-10):1, for example 6:1, 7:1, 8:1, 9:1.

[0080] In step S4 of the present application, the mass ratio of tetraethyl orthosilicate to nanoparticles P2 can be 1:(0.3-1), for example 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9.

[0081] In step S4 of the present application, the reaction temperature can be 20-30℃, for example 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃.

[0082] The thickness of the silica shell layer in step S4 of the present application is preferably 5-8 nm, for example 6 nm or 7 nm. The silica shell layer on the surface of the multilayer silica nanoparticles of the present application is advantageous in improving the mechanical strength of the nanoparticles. In the present application, the shell layer is silica, which means that no pore-forming agent is added in the reaction for preparing the silica shell layer, and thus the silica shell layer has a higher degree of order than the mesoporous silica intermediate layer. The thickness of the silica shell layer is preferably controlled to be 5-8 nm in the present application, which can improve the mechanical strength of the nanoparticles and the antireflection film, and at the same time, does not cause the light transmittance of the silica nanoparticles to decrease too much.

[0083] In some embodiments, the multilayer silica nanoparticles with a silica shell layer on the surface are prepared according to the following steps:

[0084] S1: 0.025-0.5 g of PAA with a relative molecular mass of 5000, 1 mL of 25 wt% ammonia water and 5 mL of deionized water are mixed and stirred uniformly, and then added to 100 mL of anhydrous ethanol under high-speed magnetic stirring to obtain a first solution; 0.3-0.6 g of CTAB is dissolved in 5 mL of deionized water, and after being stirred and dissolved, added to the above first solution, and then mixed and stirred uniformly to obtain a second solution; finally, 5-10 mL of TEOS is added to the second solution, and the reaction temperature of the mixed solution is controlled to be 5-10°C by using a cold water bath, and the stirring is continued for 5-8 h to obtain nanoparticles P0 with a particle size of 70-110 nm and containing PAA and CTAB;

[0085] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water with a temperature lower than 5°C, and the mesoporous pore-forming agent CTAB is removed by centrifugation to obtain nanoparticles P1 containing PAA;

[0086] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, and hydrochloric acid is added to adjust the pH value of the solution to be 1-1.5, and then heated to 60-70°C in a water bath, and stirred for 10-12 h, and then centrifuged and washed with water to obtain template-free nanoparticles P2 from which PAA is removed;

[0087] S4: The nanoparticles P2 obtained in step S3 are redispersed in a mixed solution of 100 mL of anhydrous ethanol and 10 mL of deionized water, and 0.5-1 mL of ammonia water and 5-8 mL of TEOS are added, and then stirred at room temperature for 5-8 h to finally obtain multilayer silica nanoparticles with a silica shell layer on the surface, wherein the thickness of the silica shell layer is 5-8 nm, and the particle size of the multilayer silica nanoparticles is 80-120 nm.

[0088] The multilayered silica nanoparticles prepared by the method of the present application can completely remove the template agent, which can be a mesopore-forming agent, a hollow pore-forming agent or a template agent with other functions.

[0089] The multilayered silica nanoparticles of the present application can have a particle size of 80-120 nm, for example 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm, 95 nm, 96 nm, 97 nm, 98 nm, 99 nm, 100 nm, 101 nm, 102 nm, 103 nm, 104 nm, 105 nm, 106 nm, 107 nm, 108 nm, 109 nm, 110 nm, 111 nm, 112 nm, 113 nm, 114 nm, 115 nm, 116 nm, 117 nm, 118 nm, 119 nm, 120 nm.

[0090] The mesoporous silica intermediate layer of the multilayered silica nanoparticles of the present application can have a thickness of 20-35 nm, for example 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm.

[0091] The hollow inner core of the multilayered silica nanoparticles of the present application can have a diameter of 30-70 nm, for example 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm.

[0092] The multilayered silica nanoparticles of the present application can have a specific surface area of 320-400 m 2 / g, for example 330 m 2 / g, 340 m 2 / g, 350 m 2 / g, 360 m 2 / g, 370 m 2 / g, 380 m 2 / g, 390 m 2 / g before being coated with a silica coating layer.

[0093] The multilayered silica nanoparticles of the present application can have a mesopore size of 10-20 nm, for example 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm before being coated with a silica coating layer.

[0094] The multilayered silica nanoparticles of the present application can have a porosity of 25-50%, for example 30%, 35%, 40%, 45%.

[0095] The porosity of the multilayered silica nanoparticles of the present application before coating with the silica coating layer can be 30-55%, for example, 35%, 40%, 45%, 50%.

[0096] The antireflection film of the present application comprises the multilayered silica nanoparticles as described in any of the embodiments herein. The antireflection film of the present application can be prepared by coating, drying a coating solution comprising the multilayered silica nanoparticles as described in any of the embodiments herein. In the present application, the coating solution comprises the multilayered silica nanoparticles of the present application, a solvent which can be a mixture of water and ethanol, and a crosslinking agent which can be small particle silica nanoparticles obtained by acid catalyzed hydrolysis of TEOS.

[0097] The present application will be described in detail below with specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present application. The methods, reagents and materials used in the examples are conventional in the art unless otherwise specified. The compounds in the examples are all commercially available.

[0098] In the present application, the particle size of the SiO2nanoparticles is obtained by a laser nanoparticle size analyzer.

[0099] In the present application, the thickness of the silica coating layer, the thickness of the mesoporous silica intermediate layer and the diameter of the hollow inner core are observed and photographed by transmission electron microscopy (TEM), and then the actual size is measured according to the photographing scale, and then calculated.

[0100] In the present application, the specific surface area, mesopore size and particle porosity of the silica nanoparticles are obtained by a specific surface area tester.

[0101] In the present application, the crosslinking agent of the antireflection coating solution is prepared as follows: 0.1 g of 36wt% concentrated hydrochloric acid is dissolved in 100 g of a mixed solution of deionized water and anhydrous ethanol (mass ratio of deionized water to anhydrous ethanol is 1:5), and after mixing uniformly, 20 mL of TEOS is added at one time, and after magnetic stirring at room temperature for 5-8 h, the crosslinking agent of the antireflection coating solution is obtained.

[0102] Example 1

[0103] This example prepares silica-coated multilayered silica nanoparticles P by the following steps:

[0104] S1: Take 0.5 g of PAA with a relative molecular weight of 5000, 1 mL of 25 wt% ammonia water and 5 mL of deionized water, mix and stir uniformly, then add to 100 mL of high-speed magnetic stirring anhydrous ethanol to obtain a first solution; weigh 0.4 g of CTAB dissolved in 5 mL of deionized water, stir and dissolve thoroughly, then add to the above first solution, mix and stir uniformly to obtain a second solution; finally, add 8 mL of TEOS to the second solution, and control the reaction temperature of the mixed solution at 5-10°C with a cold water bath, continue stirring for 6 h to obtain PAA and CTAB containing nanoparticles P0, with a particle size of 100-110 nm;

[0105] S2: Wash the nanoparticles P0 obtained in step S1 with ice deionized water with a temperature lower than 5°C, and remove the mesoporous pore-forming agent CTAB by centrifugation to obtain PAA containing nanoparticles P1;

[0106] S3: Redisperse the nanoparticles P1 obtained in step S2 in deionized water, add hydrochloric acid to adjust the solution pH to 1.5, heat to 65°C in a water bath, stir for 10 h, then centrifuge and wash with water to obtain PAA-free template-free nanoparticles P2;

[0107] S4: Redisperse the nanoparticles P2 obtained in step S3 in a mixed solution of 100 ml of anhydrous ethanol and 10 ml of deionized water, add 0.75 ml of ammonia water and 7 ml of TEOS, stir at room temperature for 6 h, and finally obtain silica-coated multilayer silica nanoparticles P, wherein the hollow inner core has a diameter of 60-70 nm, the mesoporous silica intermediate layer has a thickness of 20-25 nm, the silica shell layer has a thickness of 5-8 nm, and the multilayer silica nanoparticles P have a particle size of 110-120 nm.

[0108] Example 2

[0109] This example repeats steps S1-S4 in Example 1 to prepare silica-coated multilayer silica nanoparticles P, but the difference is that the stirring time in step S3 is 20 h.

[0110] Example 3

[0111] This example prepares silica-coated multilayer silica nanoparticles P by the following steps:

[0112] S1: Take 0.25g PAA with a relative molecular weight of 5000, 1mL ammonia water with a mass fraction of 25wt% and 5mL deionized water, mix and stir uniformly, then add to 100mL high-speed magnetic stirring anhydrous ethanol to obtain a first solution; weigh 0.3g CTAB and dissolve in 5mL deionized water, fully stir and dissolve, then add to the above first solution, mix and stir uniformly to obtain a second solution; finally, add 10mL TEOS to the second solution, control the reaction temperature of the mixed solution at 5-10°C with a cold water bath, and continuously stir for 6h to obtain PAA and CTAB containing nanoparticles P0 with a particle size of 90-100nm;

[0113] S2: Wash the nanoparticles P0 obtained in step S1 with ice deionized water with a temperature lower than 5°C, remove the mesoporous pore-forming agent CTAB by centrifugation to obtain PAA containing nanoparticles P1;

[0114] S3: Redisperse the nanoparticles P1 obtained in step S2 in deionized water, add hydrochloric acid to adjust the solution pH value to 1.5, heat to 65°C in a water bath, stir for 10h, then centrifuge and wash with water to obtain PAA removed template-free nanoparticles P2;

[0115] S4: Redisperse the nanoparticles P2 obtained in step S3 in a mixed solution of 100ml anhydrous ethanol and 10ml deionized water, add 0.75ml ammonia water and 6ml TEOS, stir at room temperature for 6h to finally obtain the silica coated multilayer silica nanoparticles P, wherein the hollow inner core diameter is 30-40nm, the mesoporous silica intermediate layer thickness is 30-35nm, the silica shell thickness is 5-8nm, and the particle size of the multilayer silica nanoparticles P is 100-110nm.

[0116] Example 4

[0117] This example prepares silica coated multilayer silica nanoparticles P by the following steps:

[0118] S1: Take 0.25g PAA with a relative molecular weight of 5000, 1mL ammonia water with a mass fraction of 25wt% and 5mL deionized water, mix and stir uniformly, then add to 100mL high-speed magnetic stirring anhydrous ethanol to obtain a first solution; weigh 0.3g CTAB and dissolve in 5mL deionized water, fully stir and dissolve, then add to the above first solution, mix and stir uniformly to obtain a second solution; finally, add 10mL TEOS to the second solution, control the reaction temperature of the mixed solution at 5-10°C with a cold water bath, and continuously stir for 6h to obtain PAA and CTAB containing nanoparticles P0 with a particle size of 90-100nm;

[0119] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water at a temperature lower than 5°C, the mesoporous pore-forming agent CTAB is washed away by centrifugation, and nanoparticles P1 containing PAA are obtained;

[0120] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, hydrochloric acid is added to adjust the solution pH value to 1.5, and the solution is heated to 65°C in a water bath, stirred for 10 h, and then centrifuged and washed with water to obtain template-free nanoparticles P2 from which PAA has been removed;

[0121] S4: The nanoparticles P2 obtained in step S3 are redispersed in a mixed solution of 100 ml of anhydrous ethanol and 10 ml of deionized water, 0.75 ml of ammonia water and 7 ml of TEOS are added, and stirring is performed at room temperature for 6 h, to finally obtain the silica-coated multilayer silica nanoparticles P, wherein the hollow inner core has a diameter of 60-70 nm, the mesoporous silica intermediate layer has a thickness of 20-25 nm, the silica shell layer has a thickness of 5-8 nm, and the multilayer silica nanoparticles P have a particle size of 110-120 nm.

[0122] Example 5

[0123] The silica-coated multilayer silica nanoparticles P are prepared by the following steps:

[0124] S1: 0.25 g of PAA with a relative molecular mass of 5000, 1 mL of 25 wt% ammonia water, and 5 mL of deionized water are mixed and stirred uniformly, and then added to 100 mL of anhydrous ethanol subjected to high-speed magnetic stirring to obtain a first solution; 0.3 g of CTAB is dissolved in 5 mL of deionized water, and after being fully stirred and dissolved, added to the above first solution, and after being mixed and stirred uniformly, a second solution is obtained; finally, 5 mL of TEOS is added to the second solution, and the reaction temperature of the mixed solution is controlled at 5-10°C by using a cold water bath, and stirring is continued for 6 h to obtain nanoparticles P0 containing PAA and CTAB, which have a particle size of 70-90 nm;

[0125] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water at a temperature lower than 5°C, the mesoporous pore-forming agent CTAB is washed away by centrifugation, and nanoparticles P1 containing PAA are obtained;

[0126] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, hydrochloric acid is added to adjust the solution pH value to 1.5, and the solution is heated to 65°C in a water bath, stirred for 10 h, and then centrifuged and washed with water to obtain template-free nanoparticles P2 from which PAA has been removed;

[0127] S4: The nanoparticles P2 obtained in step S3 are redispersed in a mixed solution of 100 ml of anhydrous ethanol and 10 ml of deionized water, 0.75 ml of ammonia water and 5 ml of TEOS are added, and stirring is performed at room temperature for 6 h, to finally obtain the multilayer silica nanoparticles P coated with a silica shell layer, wherein the hollow inner core has a diameter of 30-40 nm, the mesoporous silica intermediate layer has a thickness of 20-25 nm, the silica shell layer has a thickness of 5-8 nm, and the multilayer silica nanoparticles P have a particle size of 80-100 nm.

[0128] Comparative Example 1

[0129] In this example, the silica-coated multilayer silica nanoparticles P are prepared by the following steps:

[0130] S1: 0.5 g of PAA with a relative molecular mass of 5000, 1 mL of 25 wt% ammonia water and 5 mL of deionized water are mixed and stirred uniformly, and then added to 100 mL of anhydrous ethanol subjected to high-speed magnetic stirring, to obtain a first solution; 0.4 g of CTAB is dissolved in 5 mL of deionized water, and after being fully stirred and dissolved, added to the above first solution, and after being mixed and stirred uniformly, a second solution is obtained; finally, 8 mL of TEOS is added to the second solution, and the reaction temperature of the mixed solution is controlled at 25°C by using a cold water bath, and stirring is continuously performed for 6 h, to obtain the nanoparticles P0 containing PAA and CTAB;

[0131] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water with a temperature lower than 5°C, and the mesopore-forming agent CTAB is removed by centrifugation, to obtain the nanoparticles P1 containing PAA;

[0132] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, hydrochloric acid is added to adjust the pH value of the solution to 1.5, and the solution is heated to 65°C in a water bath, and after stirring for 10 h, centrifugation and water washing are performed, to obtain the template-free nanoparticles P2 from which PAA is removed;

[0133] S4: The nanoparticles P2 obtained in step S3 are redispersed in a mixed solution of 100 ml of anhydrous ethanol and 10 ml of deionized water, 0.75 ml of ammonia water and 7 ml of TEOS are added, and stirring is performed at room temperature for 6 h, to finally obtain the multilayer silica nanoparticles P coated with a silica shell layer, wherein the hollow inner core has a diameter of 60-70 nm, the mesoporous silica intermediate layer has a thickness of 20-25 nm, the silica shell layer has a thickness of 5-8 nm, and the multilayer silica nanoparticles P have a particle size of 110-120 nm.

[0134] Comparative Example 2

[0135] In this example, the silica-coated multilayer silica nanoparticles P are prepared by the following steps:

[0136] S1: Take 0.5g PAA with a relative molecular weight of 5000, 1mL ammonia water with a mass fraction of 25wt% and 5mL deionized water, mix and stir uniformly, then add to 100mL high-speed magnetic stirring anhydrous ethanol to obtain a first solution; weigh 0.4g CTAB and dissolve in 5mL deionized water, fully stir and dissolve, then add to the above first solution, mix and stir uniformly to obtain a second solution; finally, add 8mL TEOS to the second solution, control the reaction temperature of the mixed solution at 5-10℃ with a cold water bath, and continue stirring for 6h to obtain nanoparticles P0 containing PAA and CTAB;

[0137] S2: Wash the nanoparticles P0 obtained in step S1 with ice deionized water with a temperature lower than 5℃, centrifuge and wash off the mesoporous pore-forming agent CTAB to obtain nanoparticles P1 containing PAA;

[0138] S3: Redisperse the nanoparticles P1 obtained in step S2 in deionized water, add hydrochloric acid to adjust the solution pH value to 7, heat in a water bath to 65℃, stir for 10h, then centrifuge and wash with water to obtain template-free nanoparticles P2 without PAA;

[0139] S4: Redisperse the nanoparticles P2 obtained in step S3 in a mixed solution of 100ml anhydrous ethanol and 10ml deionized water, add 0.75ml ammonia water and 7ml TEOS, stir at room temperature for 6h to finally obtain multi-layer silica nanoparticles P coated with a silica shell layer, wherein the hollow inner core diameter is 60-70nm, the mesoporous silica intermediate layer thickness is 20-25nm, the silica shell layer thickness is 5-8nm, and the multi-layer silica nanoparticle P particle size is 110-120nm.

[0140] Comparative Example 3

[0141] The silica-coated multi-layer silica nanoparticles P are prepared by the following steps:

[0142] S1: Take 0.5g PAA with a relative molecular weight of 5000, 1mL ammonia water with a mass fraction of 25wt% and 5mL deionized water, mix and stir uniformly, then add to 100mL high-speed magnetic stirring anhydrous ethanol to obtain a first solution; weigh 0.4g CTAB and dissolve in 5mL deionized water, fully stir and dissolve, then add to the above first solution, mix and stir uniformly to obtain a second solution; finally, add 8mL TEOS to the second solution, control the reaction temperature of the mixed solution at 5-10℃ with a cold water bath, and continue stirring for 6h to obtain nanoparticles P0 containing PAA and CTAB;

[0143] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water at a temperature lower than 5℃, and the mesoporous pore-forming agent CTAB is removed by centrifugation to obtain nanoparticles P1 containing PAA;

[0144] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, hydrochloric acid is added to adjust the solution pH value to 1.5, and after stirring at 25℃ for 10h, centrifugal washing is performed to obtain template-free nanoparticles P2 from which PAA is removed;

[0145] S4: The nanoparticles P2 obtained in step S3 are redispersed in a mixed solution of 100ml anhydrous ethanol and 10ml deionized water, 0.75ml ammonia water and 7ml TEOS are added, and stirring is performed at room temperature for 6h to finally obtain multi-layer silica nanoparticles P coated with a silica shell layer, wherein the hollow inner core has a diameter of 60-70nm, the mesoporous silica intermediate layer has a thickness of 20-25nm, the silica shell layer has a thickness of 5-8nm, and the multi-layer silica nanoparticles P have a particle size of 110-120nm.

[0146] Comparative Example 4

[0147] In this example, silica nanoparticles P2 are prepared by the following steps:

[0148] S1: 0.5g PAA with a relative molecular mass of 5000, 1mL ammonia water with a mass fraction of 25wt%, and 5mL deionized water are mixed and stirred uniformly, and then added to 100mL anhydrous ethanol subjected to high-speed magnetic stirring to obtain a first solution; 0.4g CTAB is dissolved in 5mL deionized water, and after being fully stirred and dissolved, it is added to the above first solution, which is mixed and stirred uniformly to obtain a second solution; finally, 8mL TEOS is added to the second solution, and a cold water bath is used to control the reaction temperature of the mixed solution at 25℃, and stirring is continued for 6h to obtain nanoparticles P0 containing PAA and CTAB;

[0149] S2: The nanoparticles P0 obtained in step S1 are washed with ice deionized water at a temperature lower than 5℃, and the mesoporous pore-forming agent CTAB is removed by centrifugation to obtain nanoparticles P1 containing PAA;

[0150] S3: The nanoparticles P1 obtained in step S2 are redispersed in deionized water, hydrochloric acid is added to adjust the solution pH value to 1.5, and after stirring at 25℃ for 10h, centrifugal washing is performed to obtain template-free nanoparticles P2 from which PAA is removed;

[0151] Application Examples 1-5

[0152] The multilayered silica nanoparticles P of Example 1-2, Comparative Example 1-3 and the nanoparticles P2 of Comparative Example 4 were centrifuged and then added into a mixed solvent of anhydrous ethanol and deionized water with a mass ratio of 9 / 1 to obtain a solution, the mass ratio of the nanoparticles and the solvent in the solution being 1 / 20; the solution was mixed with a crosslinking agent at a mass ratio of 1 / 2, the pH value of the mixture was adjusted to 2.5 by dropwise adding a 1 mol / L hydrochloric acid solution and a 1 mol / L ammonia water solution to obtain a plating solution.

[0153] The plating solution was coated on the surface of the float glass by a rolling process, and after drying, a reflection-reducing film with a thickness of 110-113 nm was formed.

[0154] Test Example 1

[0155] The structure of the nanoparticles was observed by transmission electron microscopy, and the particle size of the hollow core and the thickness of the coating layer were calculated. The particle size of the nanoparticles P2 before coating and the nanoparticles P after coating was tested by a laser nanoparticle size analyzer. The mesoporous layer pore size, particle porosity and specific surface area of the nanoparticles P2 before coating and the porosity of the nanoparticles P after coating were measured by a specific surface area tester. The preparation conditions of the nanoparticles are shown in Table 1, and the test results are shown in Table 2.

[0156] Table 1: Preparation conditions of the nanoparticles P2 of Examples 1-5 and Comparative Examples 1-4 and the nanoparticles P

[0157]

[0158] Table 2: Characterization test results of the nanoparticles P2 of Examples 1-5 and Comparative Examples 1-4 and the nanoparticles P

[0159]

[0160] As shown in Table 2, compared with Example 1, the time for removing the template agent (hollow pore-forming agent) in step S3 of Example 2 is doubled, and the porosity of the prepared multilayered silica nanoparticles P is unchanged, both being about 52%, indicating that the template agent can be completely removed by the preparation method in Example 1. The difference between Example 1 and Comparative Example 1 lies in the reaction temperature of the synthesized nanoparticles P0 in step S1. The mesopore size of the nanoparticles of Comparative Example 1 obtained by reaction at room temperature is obviously smaller than that of the nanoparticles of Example 1 obtained by reaction at low temperature. This is because the low-temperature environment of Example 1 slows down the micellization rate of CTAB, but the micelles formed have improved order and are larger, resulting in larger mesopore size of the synthesized nanoparticles. The large pore size is beneficial to the dissolution of CTAB and PAA in the water washing process, while the small mesopore size of the nanoparticles synthesized in Comparative Example 1 is not conducive to the dissolution of CTAB and PAA, and the pore-forming agent cannot be completely removed, resulting in small porosity of the nanoparticles. Comparing Example 1 and Example 3, the reduced amount of PAA and the increased amount of TEOS in Example 3 make the hollow core smaller and the mesoporous layer thicker. At the same time, the reduced amount of CTAB makes the mesopore size of the synthesized nanoparticles smaller and the porosity of the nanoparticles smaller. Comparing Example 1 and Example 4, the increased amount of CTAB makes the mesopore size of the synthesized nanoparticles larger. Comparing Example 3 and Example 5, the reduced amount of TEOS makes the mesoporous layer of the synthesized nanoparticles thinner, the particle size of the nanoparticles smaller, and the porosity of the nanoparticles higher.

[0161] The difference between Example 1 and Comparative Example 2 lies in the pH value in step S3. In Example 1, the pH value is adjusted to 1.5 during the removal of PAA, and the strong acid system can accelerate the dissolution of PAA. This is because, during the synthesis of the particles, after the addition of ammonia water to the system, PAA is ammoniated to be positively charged in the system, and the silica sol hydrolyzed from TEOS is negatively charged. The attraction between the positive and negative charges makes it difficult for PAA to separate from the silica shell. When strong acid is added to the solution, the neutralization of acid and base makes PAA re-carboxylated to be negatively charged, and the dissolution rate of PAA is accelerated, so that the porosity of the nanoparticles can be easily completely released.

[0162] The difference between Example and Comparative Example 3 lies in the temperature in step S3. According to the experimental results, during the removal of PAA, increasing the temperature of the solution system can accelerate the carboxylation process and dissolution rate of PAA, so that PAA can be quickly dissolved.

[0163] Test Example 2

[0164] The optical properties and mechanical strength of the anti-reflective films of Application Examples 1-5 were measured by the following methods, as follows:

[0165] The transmittance of the coated glass was tested by a spectrophotometer PE950;

[0166] The thickness and refractive index of the anti-reflective film were tested by an ellipsometer;

[0167] The pencil hardness of the anti-reflective film was tested according to the GB / T 6739-2006 standard;

[0168] The abrasion resistance of the anti-reflective film was tested according to the JC / T 2170-2013 standard.

[0169] Table 2: Optical properties and mechanical strength of the anti-reflective films of application examples 1-5

[0170]

[0171] Compared with the anti-reflective films prepared from the nanoparticles of examples 1 and comparative examples 1-3, the anti-reflective film prepared from the nanoparticles of example 1 has the highest light transmittance, and the mechanical strength is also basically consistent with that of the anti-reflective films of comparative examples 1-3. This is because the nanoparticle porosity in comparative examples 1-3 is low, resulting in a high refractive index of the anti-reflective film, which is greatly different from the refractive index index of the optimal film system (the refractive index 1.23 is optimal). Since the surface of the nanoparticles is coated, the anti-reflective film prepared from the nanoparticles of example 1 still has relatively high mechanical strength.

[0172] Compared with the anti-reflective films prepared from the nanoparticles of examples 1 and comparative example 4, the optical properties are basically consistent. Although the porosity of the multilayer silica nanoparticles in example 1 is reduced after coating, the particle size is correspondingly increased, and the stacking gap between the particles is correspondingly increased, which compensates for part of the porosity of the anti-reflective coating, so that the overall optical properties of the anti-reflective film remain basically the same as those of comparative example 4. However, the mechanical strength of the anti-reflective film in example 1 is significantly higher than that of comparative example 4. This is because the silica shell layer coated on the hollow-mesoporous silica nanoparticles in example 1 improves the mechanical strength of the nanoparticles, and the particles are not easy to collapse and break during the process of external force collision and friction, while the hollow-mesoporous silica nanoparticles in comparative example 4 are not surface-coated, and the porous structure causes the particles to have poor stability, which is easy to break under external force, thereby causing the mechanical strength of the anti-reflective film to decrease.

Claims

1. A multilayer silica nanoparticle, characterized in that, The multilayer silica nanoparticles consist of a hollow core, a mesoporous silica intermediate layer, and a silica coating layer from the inside out, and the overall porosity of the multilayer silica nanoparticles is 25-50%. The preparation method of the multilayer silica nanoparticles includes: dispersing hollow silica nanoparticles in a mixed solvent of alcohol and water, adjusting the pH of the solution to 7-14, adding a silicon source, and reacting to form a silica coating layer on the surface of the hollow silica nanoparticles, thereby obtaining the multilayer silica nanoparticles; wherein, the hollow silica nanoparticles comprise a hollow core and a mesoporous silica shell. The method for preparing the hollow silica nanoparticles includes: S1: Dissolve the hollow pore-forming agent, the mesoporous pore-forming agent, the initiator and the silicon source in a solvent and react at 5-10℃ to obtain a solution containing nanoparticles P0. The nanoparticles P0 contain a hollow pore-forming agent core and a silica surface layer. The silica surface layer contains mesoporous channels and a mesoporous pore-forming agent filling the mesoporous channels. S2: The mesoporous pore-forming agent in the mesoporous channels of the nanoparticles P0 is removed by centrifugal washing to obtain nanoparticles P1. S3: Disperse the nanoparticles P1 in water, adjust the pH of the solution to 1-1.5, stir at 60-70℃, and remove the hollow pore-forming agent by centrifugation and water washing to obtain the hollow silica nanoparticles.

2. The multilayer silica nanoparticles as described in claim 1, characterized in that, The multilayer silica nanoparticles have one or more of the following characteristics: The particle size of the multilayer silica nanoparticles is 80-120 nm; The thickness of the silica coating layer of the multilayer silica nanoparticles is 5-8 nm; The thickness of the mesoporous silica intermediate layer of the multilayer silica nanoparticles is 20-35 nm. The hollow core of the multilayer silica nanoparticles has a diameter of 30-70 nm; The specific surface area of ​​the multilayer silica nanoparticles before being coated with a silica coating layer is 320-400 m². 2 / g; The mesopore size of the multilayer silica nanoparticles before being coated with a silica coating layer is 10-20 nm. The porosity of the multilayer silica nanoparticles before being coated with a silica coating layer is 30-55%; The multilayer silica nanoparticles do not contain mesoporous or hollow pore-forming agents.

3. The method for preparing multilayer silica nanoparticles according to claim 1 or 2, characterized in that, The method for preparing the hollow silica nanoparticles includes: S1: Dissolve the hollow pore-forming agent, the mesoporous pore-forming agent, the initiator and the silicon source in a solvent and react at 5-10℃ to obtain a solution containing nanoparticles P0. The nanoparticles P0 contain a hollow pore-forming agent core and a silica surface layer. The silica surface layer contains mesoporous channels and a mesoporous pore-forming agent filling the mesoporous channels. S2: The mesoporous pore-forming agent in the mesoporous channels of the nanoparticles P0 is removed by centrifugal washing to obtain nanoparticles P1. S3: Disperse the nanoparticles P1 in water, adjust the pH of the solution to 1-1.5, stir at 60-70℃, and remove the hollow pore-forming agent by centrifugation and water washing to obtain the hollow silica nanoparticles.

4. The preparation method according to claim 3, characterized in that, The preparation method has one or more of the following characteristics: The hollow silica nanoparticles have a particle size of 70nm-110nm; The hollow core of the hollow silica nanoparticles has a diameter of 30-70 nm; The thickness of the mesoporous silica shell of the hollow silica nanoparticles is 20-35 nm. The specific surface area of ​​the hollow silica nanoparticles is 320-400 m². 2 / g; The hollow silica nanoparticles have a mesopore size of 10-20 nm; The porosity of the hollow silica nanoparticles is 30-55%; The alcohol solvent is selected from C1-C4 alcohols; The volume ratio of alcohol solvent to water in the mixed solvent is (5-10):1; The silicon source is tetraethyl orthosilicate; The mass ratio of the silicon source to the hollow silica nanoparticles is 1:(0.3-1); The reaction temperature is 20-30℃; The reaction time is 5-8 hours; Use ammonia to adjust the pH of the solution to 7-14.

5. The preparation method according to claim 3, characterized in that, The alcohol solvent is ethanol.

6. The preparation method according to claim 3, characterized in that, The preparation method has one or more of the following characteristics: In step S1, the hollow pore-forming agent is polyacrylic acid, and the relative molecular weight of polyacrylic acid is 3000-5000. In step S1, the mesoporous pore-forming agent is hexadecyltrimethylammonium bromide and / or hexadecyltrimethylammonium chloride; In step S1, the initiator is ammonia. In step S1, the silicon source is tetraethyl orthosilicate; In step S1, the solvent is a mixture of an alcohol solvent and water; In step S1, the particle size of the nanoparticles PO is 70-110 nm; In step S1, the mass ratio of hollow pore-forming agent, mesoporous pore-forming agent and silicon source is 1:(0.5-1.5):(15-40); In step S1, the reaction time is 5-8 hours; Step S1 includes the following steps: S1-1: Mix the hollow pore-forming agent, initiator and water evenly, then add it to the alcohol solvent and stir evenly to obtain the first mixture; S1-1: Dissolve the mesoporous pore-forming agent in water and then add it to the first mixture obtained in step S1-1 to obtain the second mixture; S1-3: Add the silicon source to the second mixture and react at 5-10℃ to obtain the solution containing nanoparticles PO.

7. The preparation method according to claim 6, characterized in that, In step S1, the alcohol solvent is a C1-C4 alcohol.

8. The preparation method according to claim 6, characterized in that, In step S1, the alcohol solvent is ethanol.

9. The preparation method according to claim 3, characterized in that, In step S2, the water used for centrifugal washing is ice water with a temperature of 0-5℃; and / or In step S3, the stirring time is greater than or equal to 10 hours.

10. The preparation method according to claim 3, characterized in that, In step S3, the stirring time is 10-12 hours.

11. Multilayer silica nanoparticles prepared by any one of claims 3-10.

12. An antireflective film comprising the multilayer silica nanoparticles as described in claim 1, 2 or 11.

13. A solar cell comprising the antireflective coating of claim 12.

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