Silicon dioxide nanosheet and preparation method thereof

Abstract

The invention relates to the technical field of nano materials, in particular to a silicon dioxide nanosheet and a preparation method thereof. According to the preparation method, organic alkali and a surfactant G400 are taken as a composite template agent, tetraethyl orthosilicate is induced to be subjected to hydrolytic condensation in a solvent, generated precipitates are washed, dried and calcined, and the silicon dioxide nanosheets can be obtained; the method is simple to operate, low in cost and high in efficiency, and the obtained silicon dioxide nanosheet is ultrathin, high in crystallinity and large in specific surface area.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, in particular to a kind of silicon dioxide nanosheet and preparation method thereof. BACKGROUND

[0002] Silicon dioxide nanosheet due to its unique two-dimensional structure, high specific surface area, excellent chemical stability and biocompatibility, in catalysis, adsorption, biomedical, electronic materials and other fields show broad application prospects. However, the existing silicon dioxide nanosheet preparation method still has some limitations. For example, traditional sol-gel method and template method often need complex equipment and harsh reaction conditions, and the prepared nanosheet is thicker, it is difficult to obtain higher specific surface area and active site.

[0003] In recent years, related research reports a variety of improved silicon dioxide nanosheet preparation methods. For example, by introducing specific ions and polyols, the thickness of silicon dioxide nanosheet can be significantly thinned, but this method needs to add silicon source several times and complex hydrothermal treatment process. Another study uses silicide as precursor, and prepares silicon dioxide nanosheet by adjusting the heat treatment pressure, but these methods usually involve high temperature treatment, and the control requirements of vacuum degree and temperature are more stringent. There are also studies on the combination process of high pressure and low pressure heat treatment to prepare silicon dioxide nanosheet, but the accurate control of vacuum degree is crucial, otherwise it will affect the quality of the product. In addition, some fast continuous processes aimed at improving production efficiency still need to rely on complex shearing bubble making and demulsification steps.

[0004] Therefore, the existing technology still has the problems of complex operation, harsh reaction conditions and product performance to be further improved in the preparation of silicon dioxide nanosheet. SUMMARY

[0005] Therefore, the present application provides a kind of silicon dioxide nanosheet and preparation method thereof, at least solve one problem in the prior art.

[0006] In the first aspect, the present application provides a preparation method of silicon dioxide nanosheet, which comprises the following steps: Mixing organic base, surfactant G400 and solvent, adding tetraethyl orthosilicate under stirring to generate precipitate; Washing and drying the precipitate, and calcining at 700-900 ℃ to obtain silicon dioxide nanosheet.

[0007] In the second aspect, the present application provides silicon dioxide nanosheet obtained by the preparation method of silicon dioxide nanosheet.

[0008] With the above technical scheme, the embodiments of the present application have at least the following beneficial effects: organic base and surfactant G400 are used as a composite template agent to induce hydrolysis and condensation of tetraethyl orthosilicate in a solvent, and the generated precipitate is washed, dried and calcined to obtain silica nanosheets; the method is simple in operation, low in cost and high in efficiency, and the obtained silica nanosheets are ultra-thin in thickness, high in crystallinity, large in specific surface area and rich in edge active sites. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 SEM image of the silica nanosheets in Example 1 of the present application.

[0010] Figure 2 Isothermal adsorption-desorption curve of the silica nanosheets in Example 1 of the present application.

[0011] Figure 3 Pore size distribution graph of the silica nanosheets in Example 1 of the present application.

[0012] Figure 4 XRD pattern of the silica nanosheets in Example 1 of the present application.

[0013] Figure 5 SEM image of the silica nanosheets in Example 2 of the present application.

[0014] Figure 6 SEM image of the silica nanosheets in Example 3 of the present application. DETAILED DESCRIPTION

[0015] The concept and technical effects of the present application will be described clearly and completely below to fully explain the purpose, scheme and effects of the present application.

[0016] In a first aspect, the present application provides a preparation method of silica nanosheets, which comprises the following steps: S1, mixing an organic base, a surfactant G400 and a solvent, and adding tetraethyl orthosilicate under stirring to generate a precipitate; S2, calcining the precipitate at 700-900 ℃ to obtain silica nanosheets.

[0017] In the method, an organic base and a surfactant G400 are used as a template agent to induce the formation of silica nanosheets through their interaction with tetraethyl orthosilicate (TEOS). The surfactant G400 is a non-ionic surfactant complex system, and the specific components (calculated by mass fraction) are as follows: 10-15% fatty alcohol polyoxyethylene ether-7, 15-25% glycerol, 25-35% nonylphenol polyoxyethylene (10) ether, and 30-50% deionized water. The long-chain structure of the organic base and the cross-linking characteristics of the surfactant G400 provide an ordered template for the growth of silica, thereby realizing the uniform growth of nanosheets. TEOS hydrolyzes and condenses under the induction of the template agent to form a silica network. There is a hydrogen bond force between the amino group of the organic base and the silicon-oxygen bond (Si-O), which guides the growth of silica in a specific direction, and finally forms a two-dimensional nanosheet structure. The template agent is removed by high-temperature calcination, and at the same time, the silica nanosheets are further crystallized to improve their structural stability and mechanical strength.

[0018] In some optional embodiments, the organic base is at least one of triethylenediamine, tetramethyl ethylenediamine, and hexadecylamine.

[0019] In some optional embodiments, the mass ratio of the organic base to the surfactant G400 is 0.3-0.8:0.5-1.5.

[0020] In some optional embodiments, the solvent is a mixed solvent of ethanol and water or a mixed solvent of methanol and water. Preferably, in the mixed solvent of ethanol and water, the volume ratio of ethanol to water is 30-60:10-30. In the mixed solvent of methanol and water, the volume ratio of methanol to water is 30-60:10-30.

[0021] In some optional embodiments, step S1 specifically comprises: adding the organic base and the surfactant G400 into the solvent, stirring at a speed of 100-400 r / min to mix the organic base, the surfactant G400, and the solvent; then adding tetraethyl orthosilicate under stirring at a speed of 500-1000 r / min, and obtaining a precipitate by centrifugation or standing. By stirring at a low speed first and then at a high speed, it is ensured that the reactants are fully mixed, while avoiding excessive shear that causes defects in the nanosheet structure.

[0022] In some optional embodiments, step S2 specifically comprises: washing the precipitate with water, vacuum drying at 55-65 ℃, and calcining at 700-900 ℃ to obtain the silica nanosheets. A temperature of 700-900 ℃ can effectively remove the organic template agent while maintaining the integrity and crystallinity of the nanosheets.

[0023] In a second aspect, the present application provides the silica nanosheets prepared by the method.

[0024] Some typical embodiments are described below.

[0025] In the following examples, the surfactant G400 is purchased from Jiangxi Liankai Technology Co., Ltd., and its specific components (calculated by mass fraction) are: 10% fatty alcohol polyoxyethylene ether-7, 20% glycerol, 30% nonylphenol polyoxyethylene (10) ether and 40% deionized water.

[0026] Example 1: The silica nanosheets are prepared according to the following steps: (1) Dissolve 0.5 g of hexadecylamine and 0.8 g of surfactant G400 in 20 mL of deionized water under the condition of a 25 ℃ water bath, and continuously stir at a low speed (400 r / min) for 0.5 h to uniformly disperse; (2) Add 70 mL of a 1:1 mixture of deionized water and methanol; (3) Add 2 g of TEOS to the solution of step (2), and stir vigorously (1000 r / min) until uniform, stand for aging for 24 h, to obtain a milky white suspension; (4) Centrifuge the milky white suspension at a speed of 6000 r / min for 2 min in a high-speed centrifuge to obtain a solid, and then place it in a vacuum drying oven at 60 ℃ for 12 h to obtain a dried white powder; (5) Place the dried white powder in a muffle furnace, and calcine it at 600 ℃ for 6 h to finally obtain the silica nanosheets.

[0027] Figure 1 The SEM image of the silica nanosheets prepared in Example 1 is shown. It can be seen that the obtained product is a nanosheet-shaped, wrinkled-surface silica.

[0028] Figure 2 and Figure 3 The isothermal adsorption-desorption curve and the pore size distribution graph of the silica nanosheets prepared in Example 1 are shown. It can be seen that the obtained product is a mesoporous nanosheet structure, with a large specific surface area (524.3848 m 2 / g) and a pore size distribution concentrated at 2.4 nm.

[0029] Figure 4 The XRD pattern of the silica nanosheets prepared in Example 1 is shown. It can be seen that the obtained product is amorphous silica.

[0030] Example 2: The silica nanosheets are prepared according to the following steps: (1) 0.5 g of hexadecylamine and 0.5 g of surfactant G400 were dissolved in 20 mL of deionized water under the condition of a 25 °C water bath, and uniform dispersion was achieved by continuous low-speed (400 r / min) stirring for 0.5 h; (2) 70 mL of a mixed solvent of deionized water and methanol at a ratio of 2:3 was added; (3) 2 g of TEOS was added to the solution of step (2), and uniformity was achieved by vigorous stirring (1000 r / min), and the white suspension was obtained after standing for 24 h; (4) The white suspension was centrifuged at a speed of 6000 r / min for 2 min in a high-speed centrifuge to obtain a solid, which was then dried in a vacuum drying box at 60 °C for 12 h to obtain a white powder after drying; (5) The white powder after drying was calcined in a muffle furnace at 600 °C for 6 h, and finally the silica nanosheets were obtained.

[0031] Figure 5 SEM image of the silica nanosheets prepared in Example 2. It can be seen that the obtained product is nanosheet-shaped silica, and each sheet has uniform size and good dispersibility.

[0032] Example 3: Silica nanosheets were prepared according to the following steps: (1) 0.5 g of hexadecylamine and 1.0 g of surfactant G400 were dissolved in 20 mL of deionized water under the condition of a 25 °C water bath, and uniform dispersion was achieved by continuous low-speed (400 r / min) stirring for 0.5 h; (2) 70 mL of a mixed solvent of deionized water and methanol at a ratio of 3:4 was added; (3) 2 g of TEOS was added to the solution of step (2), and uniformity was achieved by vigorous stirring (1000 r / min), and the white suspension was obtained after standing for 24 h; (4) The white suspension was centrifuged at a speed of 6000 r / min for 2 min in a high-speed centrifuge to obtain a solid, which was then dried in a vacuum drying box at 60 °C for 12 h to obtain a white powder after drying; (5) The white powder after drying was calcined in a muffle furnace at 600 °C for 6 h, and finally the silica nanosheets were obtained.

[0033] Figure 6 SEM image of the silica nanosheets prepared in Example 3. It can be seen that the obtained product is nanosheet-shaped silica, and each sheet has uniform size and good dispersibility.

[0034] The above merely describes preferred embodiments of the present application, and the present application is not limited to the above-described embodiments, and as long as the same or equivalent means achieve the technical effects of the present application, they shall belong to the protection scope of the present application. Within the protection scope of the present application, the technical solutions and / or embodiments can have various modifications and changes.

Claims

1. A method for preparing a silica nanoplate, characterized by, The method comprises the following steps: S1, mixing an organic base, a surfactant G400 and a solvent, and adding tetraethyl orthosilicate under stirring to generate a precipitate; S2, calcining the precipitate at 700-900 DEG C to obtain a silica nanosheet.

2. The method of claim 1, wherein, The organic base is at least one of triethylenediamine, tetramethyl ethylenediamine and hexadecylamine.

3. The method of claim 1, wherein, The surfactant G400 comprises 10-15% by mass of fatty alcohol polyoxyethylene ether-7, 15-25% of glycerol, 25-35% of nonylphenol polyoxyethylene (10) ether and 30-50% of deionized water.

4. The method of claim 1, wherein, The mass ratio of the organic base to the surfactant G400 is 0.3-0.8:0.5-1.

5.

5. The method of claim 1, wherein, The solvent is a mixed solvent of ethanol and water or a mixed solvent of methanol and water.

6. The method of claim 5, wherein, In the mixed solvent of ethanol and water, the volume ratio of ethanol to water is 30-60:10-30.

7. The method of claim 5, wherein, In the mixed solvent of methanol and water, the volume ratio of methanol to water is 30-60:10-30.

8. The method of claim 1, wherein, Step S1 specifically comprises: adding the organic base and the surfactant G400 into the solvent, stirring at a rotating speed of 100-400 r / min to mix the organic base, the surfactant G400 and the solvent; then adding the tetraethyl orthosilicate under stirring at a rotating speed of 500-1000 r / min to obtain the precipitate by centrifugation or standing.

9. The method of claim 1, wherein, Step S2 specifically comprises: washing the precipitate with water, vacuum drying at 55-65 DEG C and calcining at 700-900 DEG C to obtain the silica nanosheet.

10. The silica nanosheet obtained by the method according to any one of claims 1-9.

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