Silicon oxide with two-dimensional structure

Abstract

To provide a technique for forming a monolayer of silicon oxide with sp2 hybrid orbitals.SOLUTION: The silicon oxide is synthesized by forming an emulsion of tetraalkylsilane and an aqueous component together with a surfactant, hydrolyzing the emulsion, and drying the emulsion at low temperature.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to silicon oxides having a two-dimensional structure, and more particularly to silicon oxides having a two-dimensional structure with electronic properties. [Background technology]

[0002] Most silicon oxides exist as silicon dioxide, an oxide of silicon with sp3 hybrid orbitals. It is technically common knowledge that the basic crystalline structure is a hexagonal bilayer structure, with these units stacking to form a three-dimensional structure. In recent years, it has become known that modifying the basic hexagonal bilayer structure can provide electrical properties and be useful as a microcapsule shell. Research on single-layer silicon dioxide with a non-laminated hexagonal bilayer structure has progressed, leading to the development of single-layer silicon dioxide with planar hexagonal bilayers and cyclic hexagonal bilayer silicon dioxide tubes (see, for example, Patent Documents 1, 2, and 3). Such hexagonal planar silica can be obtained by processing tetraalkoxysilane into an emulsion or liquid crystal using a surfactant, followed by baking.

[0003] On the other hand, it is known that some forms of silicon oxide have electrical conductivity (see, for example, Patent Document 4). Such silicon oxide generates heat when irradiated with microwaves, and because it is electrically conductive, it is thought to have free electrons and to be silicon oxide with sp2 hybrid orbitals. Such silicon oxide is mostly recognized as fine particle silica, and its shape is lumpy when viewed under an electron microscope, with no planar structure confirmed. No attempt has been made to make it into a planar monolayer. It has also been disclosed that such silicon oxide can be obtained by firing naturally occurring plant-derived vitreous silica in a reducing atmosphere. Regarding silicon itself, a type called silicene is known that has a planar structure similar to that of graphene, but unlike graphene, it has a "packed ring structure," and although its electronic state is unclear, it is speculated to be in a special electronic state due to its ability to encapsulate calcium ( (https: / / www.tohoku.ac.jp / japanese / newimg / pressimg / tohokuuniv-press20141222_03web.pdf) As for silicon oxide, nothing other than a hexagonal double layer structure has been clarified.

[0004] In view of the above prior art, the present inventors have hypothesized that silicon oxide similar to graphene or silicon oxide having a layered structure similar to graphite can be obtained by generating silicon oxide at a gas-liquid interface or the like and constructing a planar structure, thereby forming a single layer of silicon oxide with sp2 hybrid orbitals, and then stacking these layers as necessary, and that silicon oxide having specific, particularly specific adsorption and desorption properties can be obtained, and have therefore embarked on the development of such silicon oxide. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2019 / 40915 Brochure [Patent Document 2] Patent No. 4590544 [Patent Document 3] Patent No. 5322042 [Patent Document 4] Japanese Patent Application Publication No. 2020-87899 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention was made under these circumstances, and an object of the present invention is to provide a technique for forming a single layer of silicon oxide with sp2 hybrid orbitals.

[0007] In light of these circumstances, the present inventors have pursued a technique for forming a monolayer of sp2 hybridized silicon oxide, and as a result of extensive research and effort, have discovered that such silicon oxide can be synthesized by forming an emulsion of tetraalkylsilane and an aqueous component together with a surfactant, hydrolyzing the emulsion, and then drying the emulsion at low temperature. This has led to the completion of the present invention. Therefore, the present invention is as follows: <1> Silicon oxide is produced by mixing tetraalkoxysilane, surfactant, water, and amine and / or organic amine to form an emulsion while generating silicon oxide, and then washing and removing components other than silicon oxide, followed by drying at low temperature. <2> Characterized in that it is conductive, <1> The silicon oxide described in <3> It is characterized by having a peak only at 0Θ° in powder X-ray analysis. <1> or <2> The silicon oxide described in <4> The tetraalkoxysilane is tetraethoxysilane. <1> ~ <3> The silicon oxide according to any one of claims 1 to 10. <5> The surfactant is decaglycerol monostearate. <1> ~ <4> The silicon oxide according to any one of claims 1 to 10. <6> The amine and / or organic amine is triethanolamine and / or tetraalkylammonium salt. <1> ~ <5> The silicon oxide according to any one of the preceding claims.

[0008] According to the present invention, a technique for forming a monolayer of silicon oxide having sp2 hybrid orbitals can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the results of powder X-ray analysis of the silicon oxide of the present invention in Example 1. [Figure 2] FIG. 1 shows the results of powder X-ray analysis of conventional hexagonal bilayer flaky silica. [Figure 3] 1 is a micrograph of the silicon oxide of the present invention in Example 1 (a photograph as a substitute for a drawing). [Figure 4]FIG. 1 is a diagram showing FTIR of the pellets of Example 1. Modes for carrying out the invention

[0010] The silicon oxide of the present invention is characterized by having a single layer structure of silicon oxide with sp2 hybrid orbitals. Here, silicon oxide with a single layer structure of sp2 hybrid orbitals can be confirmed by the following facts, and conversely, these properties can be used to define the silicon oxide with a single layer structure of silicon oxide with sp2 hybrid orbitals of the present invention. In such silicon oxide, tautomerization occurs between the silicon-oxygen double bond and the silicon-carbon single bond, resulting in an affinity interaction, and thus the silicon oxide may form a layered structure. <Things to check> 1. In powder X-ray diffraction, there is a peak only at 0Θ°, and there is no inflection point, which indicates that there is only one crystal plane and that it is in a single-layer state. 2. It is electrically conductive, which indicates that π electrons originating from sp2 hybrid orbitals exist as free electrons. 3. Even in a layered state, the particle size is 10 nm or less.

[0011] Such silicon oxide can be produced by mixing a tetraalkoxysilane, a surfactant, water, and an amine and / or an organic amine to form an emulsion while generating silicon oxide, washing and removing components other than silicon oxide, and then drying at low temperature. Preferred examples of the tetraalkoxysilane include low-carbon tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane. Preferred examples of the surfactant include nonionic surfactants that readily form lamellar structures, such as sorbitan monolaurate and decaglycerol monofatty acid esters, and cationic surfactants such as quaternary ammonium salts, such as tetramethylammonium chloride, tetramethylammonium bromide, and octadecyltrimethylammonium chloride. The content of these surfactants is preferably 0.1 to 10 times the amount of tetraethoxysilane. Cationic surfactants can also be used as organic amines (described below), and their use is particularly preferred because it allows for the reduction of the amounts of other surfactants and organic amines. Preferred examples of the organic amine include triethylamine, triethanolamine, arginine, lysine, and urea. These organic amines act as catalysts for the hydrolysis of tetraalkoxysilanes. Furthermore, since silicon oxide is formed at the emulsion interface, an organic solvent capable of dissolving tetraalkoxysilanes, rather than being mixed in any proportion, and water are required to form a reaction site. Mixed solvents of hydrocarbons such as cyclohexane and normal hexane and amyl alcohols having long-chain alkyl groups are preferred as these organic solvents, and the amount of organic solvent is preferably 1 to 100 times the amount of tetraalkoxysilane. The mixing ratio of the hydrocarbon to the alcohol having a long-chain alkyl group is preferably 1:99 to 99:1 by mass. The amount of water is preferably 0.1 to 10 times the amount of organic solvent.

[0012] The silicon oxide of the present invention can be obtained by weighing out the above components, stirring at 30-50°C, confirming that an emulsion has been formed, and then heating and stirring at a low temperature of 60-90°C for 12-48 hours to hydrolyze the mixture and form silicon oxide at the emulsion interface. After the reaction is complete, the solid silicon oxide is separated, washed with water and a solvent, and dried at 60-80°C, thereby obtaining the silicon oxide of the present invention while preventing the formation of sp3 hybrid orbitals.

[0013] The silicon oxide of the present invention has π electrons and a graphene-like structure, allowing it to encapsulate compounds within its six-membered ring. Due to its electron affinity, it has a stronger adsorption ability than conventional silica, making it suitable for release control. Therefore, low-melting-point compounds can be encapsulated and stably incorporated into high-melting-point polymers such as polyamides, and the electron affinity allows for controlled release. Furthermore, low-melting-point compounds can be encapsulated into conventional silica, which can then be coated (end-capped) with the silicon oxide of the present invention to stably incorporate into high-melting-point polymers such as polyamides. Such low-melting-point compounds can be encapsulated or adsorbed in an amount 0.5 to 5 times the amount of silicon oxide or silica. The amount of silicon oxide required for end-capping is preferably 0.5 to 5 times the amount of silicon oxide or silica used as the substrate. Preferred examples of low-melting-point compounds that can be encapsulated or adsorbed include fragrances, insect repellents, insecticides such as pyrethroids, and biopheromones.

[0014] The present invention will be described in more detail below with reference to examples. [Example] Example 1

[0015] The silicon oxide of the present invention was prepared according to the following procedure. Specifically, 9.1 g of decaglycerol monolaurate, 3 g of triethanolamine, 2.22.5 g of orthotetraethoxysilane, and 0.1 g of tetramethylammonium were added to 100 ml of n-hexane, 2.5 ml of amyl alcohol, and 50 ml of water. The mixture was heated to 70°C with stirring to form an emulsion. The mixture was then maintained at 70°C for 24 hours, gradually hydrolyzing the orthotetraethoxysilane and forming silicon oxide at the emulsion interface. After the reaction was completed, the mixture was returned to room temperature, centrifuged, and the solid was washed three times with 50 ml of ethanol and three times with 50 ml of water. It was then air-dried at 70°C for 24 hours to obtain 10 g of silicon oxide. PXRD showed a peak at 0°, with no other peaks or inflection points (Figure 1). This silicon oxide was identified as 2D-single-layer silicon oxide. The X-ray analysis of the hexagonal double-layered silica is shown in Figure 2. Furthermore, from the micrograph (Fig. 3), the particle size was 2 to 5 nm and a planar layered structure was observed.

[0016] 10g of jasmine-like fragrance was included in 10g of the silicon dioxide. The PXRD of this product is shown in the figure. The inclusion of the fragrance is recognized as a change in the crystal system. The inclusion was performed by directly mixing the two.

[0017] The clathrate silicon oxide was end-capped using the following procedure. 9.1 g of decaglycerin monolaurate, 3 g of triethanolamine, 2.22.5 g of orthotetraethoxysilane, and 0.1 g of tetramethylammonium were added to 10 g of clathrate silicon oxide, 100 ml of n-hexane, 2.5 ml of amyl alcohol, and 50 ml of water. The mixture was heated to 70°C with stirring to form an emulsion. The temperature was maintained at 70°C for 24 hours, gradually hydrolyzing the orthotetraethoxysilane and producing silicon oxide at the emulsion interface. After the reaction was completed, the mixture was returned to room temperature, and the solid was centrifuged and washed three times with 50 ml of ethanol and three times with 50 ml of water. The mixture was then air-dried at 70°C for 24 hours to yield 17 g of silicon oxide end-capped clathrate silicon oxide.

[0018] 95g of polybutylene terephthalate was melted at 250°C, 5g of the end-capped silicon dioxide was added, and the mixture was stirred and pelletized. This was used as a masterbatch, and 395g of polybutylene terephthalate was added to 5g of the masterbatch, melted, and pellets were made. When these pellets were spun, a thread with a jasmine-like scent was produced. The FTIR spectrum of this product is shown in Figure 4, which shows that the fragrance is encapsulated. In other words, we have developed a technology that encapsulates fragrances with a boiling point of 100°C or less in polymers with a melting point of 250°C. Industrial applicability

[0019] The present invention is applicable to the production of high melting point polymers containing low melting point compounds.

Claims

1. The silicon oxide is obtained by mixing tetraalkoxysilane, a surfactant, water, and an amine and / or an organic amine to form an emulsion while generating silicon oxide, and then washing and removing components other than silicon oxide, followed by drying at low temperature.

2. 2. The silicon oxide according to claim 1, which is electrically conductive.

3. 3. The silicon oxide according to claim 1, which has a peak only at 0 Θ° in powder X-ray analysis.

4. 4. The silicon oxide according to claim 1, wherein the tetraalkoxysilane is tetraethoxysilane.

5. 5. The silicon oxide according to claim 1, wherein the surfactant is decaglycerol monostearate.

6. 6. The silicon oxide according to claim 1, wherein the amine and / or organic amine is triethanolamine and / or a tetraalkylammonium salt.

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