Preparation method and application of mesoporous SiO2 nanoparticles with adjustable concave-convex curvature

Abstract

The present invention relates to the field of nanomaterials, and in particular to a preparation method and application of mesoporous SiO2 nanoparticles with adjustable concavo-convex curvature. The preparation method comprises the steps of: mixing and stirring hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, ethanol, water, sodium citrate solution, ammonia water and alcohol oil phase solvent to obtain a first emulsion; adding a silicon source to the first emulsion, and standing to react to obtain mesoporous SiO2 nanoparticles; wherein mesoporous SiO2 nanoparticles with target concavo-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths; when the alcohol oil phase solvent is n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2 to 9 / 8. The preparation method is simple to operate and has high efficiency, especially by using alcohol oil phase solutions with different alkane chain lengths, the concavo-convex curvature of the mesoporous SiO2 nanoparticles can be precisely and regularly controlled.

Description

Technical Field

[0001] The invention relates to the field of nano materials, and in particular to a preparation method and application of mesoporous SiO2 nanoparticles with adjustable concave-convex curvature. Background Art

[0002] Compared with hollow spherical nanoparticles, which have a high surface area / volume ratio and low density, concave nanoparticles have a more open structure and a higher packing density. In addition, the concave nanoparticles have a unique internal cavity structure, which reduces the specific density of the material and enhances the multiple refractions of light inside the cavity, thereby effectively improving the light response of the nanoparticles, which is difficult to achieve for traditional hollow structure particles. At the same time, the hollow structure is conducive to promoting dielectric loss through interface polarization, especially the hollow structure of the inner cavity can adjust the dielectric constant and improve the impedance matching between the nanoabsorber and the air, thereby achieving precise adjustment of light or waves.

[0003] In the prior art, concave SiO2 nanoparticles are mainly prepared by hard template-assisted synthesis strategies, such as wet chemical method, sol-gel method, chemical vapor deposition method, electrochemical deposition method and solvothermal method. However, these hard template-assisted synthesis strategies require multiple synthesis steps, usually involving the synthesis of template precursors, the coverage of target objects, the removal of templates, etc., which are not only time-consuming and low in yield, but also challenging to selectively convert intermediate shapes into new materials because the intermediate shapes are unstable, so it is difficult to separate them, which also limits the ability to accurately adjust the degree of concavity of SiO2 nanoparticles. Although someone has developed a method of expansion-induced buckling to synthesize asymmetric structures with good adjustable concavity, the buckling of the soft shell is a dynamic and non-selective process. In addition, although this method can generate various bowl-shaped structures without a template, the bowl-shaped colloidal particles formed are mainly composed of dense shells, which further limits the storage and diffusion of guest molecules and reduces the absorption of light waves. Therefore, the existing method for preparing concave-convex SiO2 nanoparticles is complex, inefficient, and unable to achieve precise adjustment, and needs to be improved and developed. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a preparation method and application of mesoporous SiO2 nanoparticles with adjustable concave-convex curvature, aiming to solve the problems of complex process, low efficiency and inability to accurately adjust the concave-convex degree of SiO2 nanoparticles in the existing preparation method.

[0005] The technical solution of the present invention is as follows:

[0006] The first aspect of the present invention provides a method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature, which comprises the steps of:

[0007] Hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, ethanol, water, sodium citrate solution, ammonia water and an alcohol oil phase solvent are mixed and stirred to react to obtain a first emulsion;

[0008] Adding a silicon source to the first emulsion and allowing it to react to obtain mesoporous SiO2 nanoparticles;

[0009] Wherein, mesoporous SiO2 nanoparticles with target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths;

[0010] When the alcohol oil phase solvent is n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2 to 9 / 8;

[0011] When the mesoporous SiO2 nanoparticles are concave, the concave-convex curvature is the maximum distance from the center of the concave plane of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not concave; when the mesoporous SiO2 nanoparticles are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not convex.

[0012] Optionally, when the alcohol oil phase solvent is n-propanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2;

[0013] Or when the alcohol oil phase solvent is n-butanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 3 / 4;

[0014] Or when the alcohol oil phase solvent is n-pentanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 7 / 8;

[0015] Or when the alcohol oil phase solvent is n-hexanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1;

[0016] Or when the alcohol oil phase solvent is n-heptanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 9 / 8.

[0017] Optionally, the mass ratio of the hexadecyltrimethylammonium bromide to polyvinylpyrrolidone is 1:45 to 1:55.

[0018] Optionally, the silicon source is tetraethyl orthosilicate, and the volume ratio of tetraethyl orthosilicate to ammonia water is 3:2 to 3:2.3.

[0019] Optionally, the volume ratio of the ethanol, water, sodium citrate solution, aqueous ammonia and alcohol oil phase solvent is 10:1:1:1:100 to 15:1:1:1:120.

[0020] The second aspect of the present invention provides a mesoporous SiO2 nanoparticle prepared by the method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature described in the present invention.

[0021] The third aspect of the present invention provides a method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature and internally loaded Fe3O4 and externally loaded Au, which comprises the steps of:

[0022] Hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone, ethanol, Fe3O4 nanoparticle aqueous solution, sodium citrate solution, ammonia water and alcohol oil phase solvent are mixed and stirred to react to obtain a second emulsion;

[0023] Adding a silicon source to the second emulsion and allowing it to react to obtain mesoporous SiO2 nanoparticles loaded with Fe3O4;

[0024] The mesoporous SiO2 nanoparticles loaded with Fe3O4 and Au 3+ The reagent and the reducing agent react to obtain mesoporous SiO2 nanoparticles with internal Fe3O4 loading and external Au loading;

[0025] wherein mesoporous SiO2 nanoparticles with internally loaded Fe3O4 and externally loaded Au having a target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths;

[0026] When the alcohol oil phase solvent is n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 1 / 2 to 9 / 8;

[0027] When the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are concave, the concave-convex curvature is the maximum distance from the center of the plane of the concave part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when not concave; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when not convex.

[0028] The fourth aspect of the present invention provides a mesoporous SiO2 nanoparticle with internal Fe3O4 and external Au load, which is prepared by the method for preparing mesoporous SiO2 nanoparticle with internal Fe3O4 and external Au load and adjustable concave-convex curvature described in the present invention.

[0029] The fifth aspect of the present invention provides an application of the mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load as described in the present invention in the photothermal catalytic oxidation reaction of benzyl alcohol.

[0030] Beneficial effects: The preparation method provided by the present invention is simple to operate and highly efficient, especially by using alcohol oil phase solutions with different alkane chain lengths, the regular and precise regulation of the concave-convex curvature of the mesoporous SiO2 nanoparticles is achieved. In addition, mesoporous SiO2 nanoparticles (nanoreactors) with internal Fe3O4 load and external Au load with different concave-convex curvatures are successfully prepared by a similar preparation method, which can efficiently convert benzyl alcohol into benzaldehyde and can be recycled for multiple times, and has good application prospects and value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 / 2 prepared in Example 1.

[0032] Figure 2 The structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 3 / 4 prepared in Example 2.

[0033] Figure 3 The structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 7 / 8 prepared in Example 3.

[0034] Figure 4 This is the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 prepared in Example 4.

[0035] Figure 5 The structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 9 / 8 prepared in Example 5.

[0036] Figure 6 This is the EDS image of mesoporous SiO2 nanoparticles with internal Fe3O4 loading and external Au loading with a concave-convex curvature of 3 / 4.

[0037] Figure 7 This is a graph showing the photothermal catalytic oxidation performance of benzyl alcohol for mesoporous SiO2 nanoparticles with five different concave-convex curvatures and internally loaded Fe3O4 and externally loaded Au. DETAILED DESCRIPTION

[0038] The present invention provides a preparation method and application of mesoporous SiO2 nanoparticles with adjustable concave-convex curvature. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] According to one embodiment of the present invention, a method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature is provided, which comprises the steps of:

[0040] S1, mixing and stirring hexadecyltrimethylammonium bromide, polyvinylpyrrolidone, ethanol, water (preferably deionized water), sodium citrate solution, ammonia water and an alcohol oil phase solvent to obtain a first emulsion;

[0041] S2, adding a silicon source to the first emulsion, allowing the solution to react to obtain mesoporous SiO2 nanoparticles;

[0042] Wherein, mesoporous SiO2 nanoparticles with target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths;

[0043] When the alcohol oil phase solvent is n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2 to 9 / 8;

[0044] When the mesoporous SiO2 nanoparticles are concave, the concave-convex curvature is the maximum distance from the center of the concave plane of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not concave; when the mesoporous SiO2 nanoparticles are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not convex.

[0045] The embodiment of the present invention prepares mesoporous SiO2 nanoparticles through the self-assembly strategy of the emulsion system. Steps S1 and S2 are both performed at room temperature. The preparation method is simple to operate, highly efficient, and can regularly and precisely control the concave-convex curvature of the synthesized mesoporous SiO2 nanoparticles. The key points of innovation of the embodiment of the present invention are that, first, hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) are introduced as dual surfactants, wherein CTAB is used as a "pore-forming agent" to realize the open mesopores of the SiO2 nanoparticles, so that it has a large specific surface area and good chemical stability; second, alcohol oil phase solvents with different alkane chain lengths are used in the emulsion system to regularly and precisely control the concave-convex curvature of the mesoporous SiO2 nanoparticles, rather than simply and irregularly expanding the cavity size. The inventors have discovered that when using alcohol oil phase solvents with gradually longer carbon chain lengths (n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol), the concave-convex curvature of the mesoporous SiO2 nanoparticles can be regularly and precisely controlled to 1 / 2 to 9 / 8, and the morphology of the mesoporous SiO2 nanoparticles changes from being concave inward to being convex outward.

[0046] The embodiment of the present invention adopts an oil-in-water emulsion system (the oil-in-water emulsion system can manipulate the hollow morphology inside the SiO2 nanoparticles), and the alcohol oily solvent wraps the water to form nanodroplets, then introduces a silicon source and hydrolyzes to form silicate oligomers, which are then polymerized and assembled with surfactant / silicate composite micelles in the water phase, and continuously deposited on the interface. Under the influence of the oil-water interface energy, the growth rate of the oligomer at the interface will be significantly faster than the deposition rate on the shell, which causes the shell grown later to gradually become thinner. Since the growth of the entire shell is a dynamic deposition-solidification process, the subsequent growth of the thin shell is not rigid enough and will collapse into the droplet as the oil-water interface migrates. The present application adjusts the oil-water interface energy by using alcohol oil phase solvents with different carbon chain lengths. The oil-water interface energy will decrease with the increase of the carbon chain length of the alcohol oil phase solvent, and the surface interface tends to be stable, which will affect the miscibility of water in the oil phase, and further change the relative changes in the interface growth rate and the shell deposition rate, and finally achieve the control of the concave-convex curvature of the mesoporous SiO2 nanoparticles.

[0047] The concavo-convex curvature C described in the embodiment of the present invention is calculated as follows: when the mesoporous SiO2 nanoparticle is concave, the concavo-convex curvature is the maximum distance L from the center of the plane of the concave part of the mesoporous SiO2 nanoparticle to the bottom of the mesoporous SiO2 nanoparticle / the diameter D of the spherical mesoporous SiO2 nanoparticle when not concave; when the mesoporous SiO2 nanoparticle is spherical, the concavo-convex curvature is 1; when the mesoporous SiO2 nanoparticle is convex, the concavo-convex curvature is the maximum distance L from the highest point of the convex part of the mesoporous SiO2 nanoparticle to the bottom of the mesoporous SiO2 nanoparticle / the diameter D of the spherical mesoporous SiO2 nanoparticle when not convex. For example, for the following embodiment 1, the concavo-convex curvature is 1 / 2; for the following embodiment 2, the concavo-convex curvature is 3 / 4; for the following embodiment 3, the concavo-convex curvature is 7 / 8; for the following embodiment 4, the concavo-convex curvature is 1; for the following embodiment 5, the concavo-convex curvature is 9 / 8.

[0048] In some embodiments, when the alcohol oil phase solvent is n-propanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2; or when the alcohol oil phase solvent is n-butanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 3 / 4; or when the alcohol oil phase solvent is n-pentanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 7 / 8; or when the alcohol oil phase solvent is n-hexanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 1; or when the alcohol oil phase solvent is n-heptanol, the concave-convex curvature of the mesoporous SiO2 nanoparticles is 9 / 8.

[0049] In this embodiment, when the concave-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2, 3 / 4 and 7 / 8, the mesoporous SiO2 nanoparticles exhibit a concave bowl-shaped structure; when the concave-convex curvature of the mesoporous SiO2 nanoparticles is 1, the mesoporous SiO2 nanoparticles exhibit an isotropically grown spherical structure; when the concave-convex curvature of the mesoporous SiO2 nanoparticles is 9 / 8, the mesoporous SiO2 nanoparticles exhibit a convex water drop-shaped structure.

[0050] The embodiment of the present invention can regularly and precisely control the concave-convex curvature of mesoporous SiO2 nanoparticles by using alcohol oil phase solvents (n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol) with different alkane chain lengths in the emulsion system. Specifically, when the alcohol oil phase solvent is adjusted from n-propanol to n-butanol or n-pentanol in the emulsion system, the mesoporous SiO2 nanoparticles gradually increase from a concave bowl-shaped structure with a concave-convex curvature of 1 / 2 to a concave bowl-shaped structure with a concave-convex curvature of 3 / 4 or 7 / 8; when the alcohol oil phase solvent is further adjusted to n-hexanol, the mesoporous SiO2 nanoparticles form an isotropically grown spherical structure with a concave-convex curvature of 1; when the alcohol oil phase solvent is further adjusted to n-heptanol, the mesoporous SiO2 nanoparticles form a convex water drop-shaped structure with a concave-convex curvature of 9 / 8. In this whole process, the morphology of the mesoporous SiO2 nanoparticles gradually changes from the initial concave bowl-shaped structure to a water drop-shaped structure that grows outwardly convexly.

[0051] In some embodiments, the mass ratio of cetyltrimethylammonium bromide to polyvinylpyrrolidone is 1:45 to 1:55.

[0052] In some embodiments, the silicon source is tetraethyl orthosilicate (TEOS), and the volume ratio of the tetraethyl orthosilicate to ammonia water is 3:2 to 3:2.3.

[0053] In some embodiments, the volume ratio of the ethanol, water, sodium citrate solution, aqueous ammonia and alcohol oil phase solvent is 10:1:1:1:100 to 15:1:1:1:120.

[0054] In some embodiments, step S1 specifically comprises: dissolving hexadecyltrimethylammonium bromide and polyvinylpyrrolidone in an alcohol oil phase solvent, and then adding ethanol, water (preferably deionized water), sodium citrate solution and ammonia water to mix and stir to obtain a uniform first emulsion.

[0055] In some preferred embodiments, the stirring reaction in step S1 is performed at room temperature, and the stirring reaction is performed under ultrasonic conditions.

[0056] In some embodiments, the step S2 specifically includes: adding a silicon source to the first emulsion, allowing the solution to react, and then subjecting the solution to centrifugal separation, washing, and extraction to obtain mesoporous SiO2 nanoparticles.

[0057] In some preferred embodiments, in step S2, the static reaction temperature is room temperature and the reaction time is 4 hours.

[0058] According to one embodiment of the present invention, there is provided a mesoporous SiO2 nanoparticle prepared by the method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature described in any of the aforementioned embodiments of the present invention.

[0059] According to one embodiment of the present invention, a method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature and internally loaded Fe3O4 and externally loaded Au is provided, wherein the method comprises the steps of:

[0060] S10, mixing and stirring hexadecyltrimethylammonium bromide, polyvinylpyrrolidone, ethanol, Fe3O4 nanoparticle aqueous solution, sodium citrate solution, ammonia water and alcohol oil phase solvent to obtain a second emulsion;

[0061] S11, adding a silicon source to the second emulsion, and allowing the mixture to react to obtain mesoporous SiO2 nanoparticles loaded with Fe3O4;

[0062] S12, the mesoporous SiO2 nanoparticles containing Fe3O4 and Au 3+ The reagent and the reducing agent react to obtain mesoporous SiO2 nanoparticles with internal Fe3O4 loading and external Au loading;

[0063] wherein mesoporous SiO2 nanoparticles with internally loaded Fe3O4 and externally loaded Au having a target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths;

[0064] When the alcohol oil phase solvent is n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 1 / 2 to 9 / 8;

[0065] When the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are concave, the concave-convex curvature is the maximum distance from the center of the concave plane to the bottom of the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au / the diameter of the spherical mesoporous SiO2 nanoparticles when not concave; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part to the bottom of the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au / the diameter of the spherical mesoporous SiO2 nanoparticles when not convex.

[0066] The method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature and internally loaded Fe3O4 and externally loaded Au provided in an embodiment of the present invention is similar to the method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature described above, the main difference being that water is replaced with an aqueous solution of Fe3O4 nanoparticles in this embodiment (a solution formed by Fe3O4 nanoparticles dispersed in water), Fe3O4 is first loaded into the interior of the mesoporous SiO2 nanoparticles using the aqueous solution of Fe3O4 nanoparticles, and then the Au-containing solution is used. 3+ The reagent and the reducing agent react to load Au onto the outside of the mesoporous SiO2 nanoparticles, and finally prepare mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au. Similarly, in the preparation process, by using alcohol oil phase solvents (n-propanol, n-butanol, n-pentanol, n-hexanol or n-heptanol) with different alkane chain lengths, the concave-convex curvature of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is precisely regulated, and mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au with a concave-convex curvature of 1 / 2 to 9 / 8 are prepared. The mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au with different concave-convex curvatures prepared by the present invention can be used as nanoreactors to efficiently convert benzyl alcohol into benzaldehyde, and can be recycled for many times, which has good application prospects and value.

[0067] In a preferred embodiment, when the alcohol oil phase solvent is n-propanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 1 / 2;

[0068] Or when the alcohol oil phase solvent is n-butanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 3 / 4;

[0069] Or when the alcohol oil phase solvent is n-pentanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 7 / 8;

[0070] Or when the alcohol oil phase solvent is n-hexanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 1;

[0071] Or when the alcohol oil phase solvent is n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 9 / 8.

[0072] In some embodiments, step S10 specifically includes: dissolving hexadecyltrimethylammonium bromide and polyvinylpyrrolidone in an alcohol oil phase solvent, and then adding ethanol, Fe3O4 nanoparticle aqueous solution, sodium citrate solution and ammonia water to mix and stir to obtain a uniform second emulsion.

[0073] In some preferred embodiments, the stirring reaction in step S10 is performed at room temperature, and the stirring reaction is performed under ultrasonic conditions.

[0074] In some embodiments, the step S11 specifically includes: adding a silicon source to the second emulsion, allowing the reaction to proceed, and then subjecting the mixture to centrifugal separation, washing, and extraction to obtain mesoporous SiO2 nanoparticles loaded with Fe3O4.

[0075] In some preferred embodiments, in step S11, the static reaction temperature is room temperature and the reaction time is 4 hours.

[0076] In some embodiments, the step S12 specifically comprises: dispersing the mesoporous SiO2 nanoparticles loaded with Fe3O4 in an ethanol solution, adding Au 3+ The reagent and the reducing agent react, and after the solution changes from colorless to purple, centrifugal separation is performed to obtain mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load.

[0077] In some preferred embodiments, the Au-containing 3+ The reagent is an aqueous solution of HAuCl4·4H2O, preferably at a concentration of 50 mM.

[0078] In some preferred embodiments, the reducing agent is an aqueous solution of sodium borohydride, preferably with a concentration of 0.01 M.

[0079] According to one embodiment of the present invention, there is provided a mesoporous SiO2 nanoparticle with internal Fe3O4 load and external Au load, which is prepared by the method for preparing mesoporous SiO2 nanoparticle with internal Fe3O4 load and external Au load and adjustable concave-convex curvature as described in any of the aforementioned embodiments of the present invention.

[0080] The mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load provided in the embodiment of the present invention can be used as a nanoreactor, can efficiently convert benzyl alcohol into benzaldehyde, and can be recycled for many times, and have good application prospects and value.

[0081] According to one embodiment of the present invention, there is provided an application of the mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load of the present invention in the photothermal catalytic oxidation reaction of benzyl alcohol.

[0082] The present invention will be further described below by means of specific examples.

[0083] Example 1

[0084] At room temperature, 10 mL of n-propanol was added to the reaction vessel, followed by 20 mg of CTAB and 1 g of PVP. After PVP and CTAB were completely dissolved, 1 mL of ethanol, 100 μL of deionized water, 100 μL of sodium citrate aqueous solution (concentration of 0.18 M) and 100 μL of NH3·H2O (28wt%) were added to the reaction vessel and then continuously ultrasonicated to form a uniform emulsion. Subsequently, the emulsion was ultrasonicated for 10 min, and then 150 μL of TEOS was added. The reaction was allowed to stand at room temperature for 4 h to obtain a crude product. The product was then washed three times by centrifugation with ethanol and collected, and then extracted with 0.1 M hydrochloric acid in ethanol at 60 ° C for 12 h. After two consecutive extractions, the residual surfactant was removed, and mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 / 2 were obtained, showing a concave bowl-shaped structure (half bowl-shaped structure) with a concave-convex curvature of 1 / 2.

[0085] Figure 1 These are the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 / 2 prepared in Example 1, where a is a schematic diagram of the structural model (which shows the calculation method of the concave-convex curvature C), b is a scanning electron microscope (SEM) image, and c is a transmission electron microscope (TEM) image.

[0086] Example 2

[0087] The preparation method is the same as that in Example 1, except that n-propanol is replaced with n-butanol when preparing the emulsion, so that mesoporous SiO2 nanoparticles with a concave-convex curvature of 3 / 4 can be prepared, showing a concave bowl-shaped structure with a concave-convex curvature of 3 / 4.

[0088] Figure 2 These are the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 3 / 4 prepared in Example 2, where a is a schematic diagram of the structural model (which shows the calculation method of the concave-convex curvature C), b is a SEM diagram, and c is a TEM diagram.

[0089] Example 3

[0090] The preparation method is the same as that in Example 1, except that n-propanol is replaced with n-pentanol when preparing the emulsion, so that mesoporous SiO2 nanoparticles with a concave-convex curvature of 7 / 8 can be prepared, showing a concave bowl-shaped structure with a concave-convex curvature of 7 / 8.

[0091] Figure 3These are the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 7 / 8 prepared in Example 3, where a is a schematic diagram of the structural model (which shows the calculation method of the concave-convex curvature C), b is a SEM diagram, and c is a TEM diagram.

[0092] Example 4

[0093] The preparation method is the same as that in Example 1, except that n-propanol is replaced with n-hexanol when preparing the emulsion, so that mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 can be prepared, which exhibits an isotropically grown spherical structure with a concave-convex curvature of 1.

[0094] Figure 4 These are the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 prepared in Example 4, where a is a schematic diagram of the structural model (which shows the calculation method of the concave-convex curvature C), b is a SEM diagram, and c is a TEM diagram.

[0095] Example 5

[0096] The preparation method is the same as that in Example 1, except that n-propanol is replaced with n-heptanol when preparing the emulsion, thereby preparing mesoporous SiO2 nanoparticles with a concave-convex curvature of 9 / 8, which exhibit a convex water droplet-shaped structure.

[0097] Figure 5 These are the structural model diagram and morphology diagram of the mesoporous SiO2 nanoparticles with a concave-convex curvature of 9 / 8 prepared in Example 5, where a is a schematic diagram of the structural model (which shows the calculation method of the concave-convex curvature C), b is a SEM diagram, and c is a TEM diagram.

[0098] Example 6

[0099] By replacing 100 μL of deionized water in the preparation method of mesoporous SiO2 nanoparticles with five kinds of concave-convex curvatures provided in Examples 1-5 with an equal amount of Fe3O4 nanoparticle aqueous solution, mesoporous SiO2 nanoparticles with internal loading of Fe3O4 can be obtained. Subsequently, the obtained sample is dispersed in an ethanol solution, and 20 μL of HAuCl4·4H2O aqueous solution (50 mM) is added to the mesoporous SiO2 nanoparticles with internal loading of Fe3O4 and stirred evenly. At the same time, 20 μL of freshly prepared sodium borohydride aqueous solution (0.01M) is quickly added to the above mixture, and it is observed that the solution quickly changes from colorless and transparent to dark purple. After stirring for 20 min, the mixture is centrifuged, washed and collected, and finally, mesoporous SiO2 nanoparticles (nanoreactors) with internal loading of Fe3O4 and external loading of Au with concave-convex curvatures of 1 / 2, 3 / 4, 7 / 8, 1 and 9 / 8 respectively are obtained.

[0100] Figure 6This is an energy dispersive spectroscopy (EDS) diagram of mesoporous SiO2 nanoparticles with an internal loading of Fe3O4 and an external loading of Au and a concave-convex curvature of 3 / 4. From this diagram, it can be seen that Fe3O4 is loaded inside the mesoporous SiO2 nanoparticles and Au is loaded outside the mesoporous SiO2 nanoparticles.

[0101] Example 7

[0102] This example explores the catalytic effect of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au as catalysts prepared in Example 6 in the photothermal catalytic oxidation reaction of benzyl alcohol, specifically:

[0103] 50 mg of each of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loads prepared in Example 6 and with concave-convex curvatures of 1 / 2, 3 / 4, 7 / 8, 1 and 9 / 8, respectively, were placed in different three-necked flasks, and 10 mL of acetonitrile and 70 μL of benzyl alcohol were added, stirred with a mechanical stirrer (400 rpm), oxygen was introduced with a gas flowmeter (20 mL / min), and a xenon lamp was turned on for photothermal catalytic reaction. During the reaction, a certain amount of samples were taken at fixed points and tested by gas chromatography-mass spectrometry to evaluate the oxidation performance of five mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loads with different concave-convex curvatures for benzyl alcohol.

[0104] Figure 7Figure 3 is the photothermal catalytic oxidation performance diagram of mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with five different concave-convex curvatures for benzyl alcohol, where a is the relationship between time and conversion rate of mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with five different concave-convex curvatures in the photothermal catalytic oxidation reaction of benzyl alcohol (reactor-1 in the figure represents mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with a concave-convex curvature of 1 / 2, reactor-2 represents mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with a concave-convex curvature of 3 / 4, reactor-3 represents mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with a concave-convex curvature of 7 / 8, reactor-4 represents mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with a concave-convex curvature of 1, and reactor-5 represents mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au loaded with a concave-convex curvature of 9 / 8). 2 nanoparticles), b is a comparison of the selectivity of benzyl alcohol to benzaldehyde catalyzed by five mesoporous SiO2 nanoparticles with different concave-convex curvatures, internally loaded with Fe3O4 and externally loaded with Au (the abscissa in the figure represents mesoporous SiO2 nanoparticles with a concave-convex curvature of 1 / 2, 2 represents mesoporous SiO2 nanoparticles with a concave-convex curvature of 3 / 4, 3 represents mesoporous SiO2 nanoparticles with a concave-convex curvature of 7 / 8, internally loaded with Fe3O4 and externally loaded with Au, 4 represents mesoporous SiO2 nanoparticles with a concave-convex curvature of 1, and 5 represents mesoporous SiO2 nanoparticles with a concave-convex curvature of 9 / 8), and c is a comparison of the number of cycles, selectivity and conversion rate of the catalytic oxidation of benzyl alcohol by mesoporous SiO2 nanoparticles with a concave-convex curvature of 7 / 8. The results show that the conversion rate of benzyl alcohol catalytically oxidized by mesoporous SiO2 nanoparticles with five different concave-convex curvatures, which are internally loaded with Fe3O4 and externally loaded with Au, can reach 100%, and the selectivity of producing benzaldehyde is more than 90%. Among them, the mesoporous SiO2 nanoparticles with internally loaded Fe3O4 and externally loaded with Au, which have a concave-convex curvature of 7 / 8, have the best selectivity. At the same time, their selectivity and conversion rate remain relatively stable after being recycled for 6 times.

[0105] In summary, the preparation method provided by the present invention is simple to operate and highly efficient, especially by using alcohol oil phase solutions with different alkane chain lengths in the emulsion system, the regular and precise control of the concave-convex curvature of the mesoporous SiO2 nanoparticles is achieved. In addition, mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load with different concave-convex curvatures are successfully prepared by a similar preparation method, which can efficiently convert benzyl alcohol into benzaldehyde and can be recycled for multiple times, and has good application prospects and value.

[0106] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature, characterized in that: Includes steps: Hexadecyltrimethylammonium bromide, polyvinylpyrrolidone, ethanol, water, sodium citrate solution, ammonia water and an alcohol oil phase solvent are mixed and stirred to react to obtain a first emulsion; the volume ratio of the ethanol, water, sodium citrate solution, ammonia water and the alcohol oil phase solvent is 10:1:1:1:100 to 15:1:1:1:120; Adding a silicon source to the first emulsion and allowing it to react to obtain mesoporous SiO2 nanoparticles; Wherein, mesoporous SiO2 nanoparticles with target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths; When the alcohol oil phase solvent is n-propanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2; Or when the alcohol oil phase solvent is n-butanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 3 / 4; Or when the alcohol oil phase solvent is n-pentanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 7 / 8; Or when the alcohol oil phase solvent is n-hexanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1; Or when the alcohol oil phase solvent is n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 9 / 8; When the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1 / 2, 3 / 4 and 7 / 8, the mesoporous SiO2 nanoparticles show a concave bowl-shaped structure; when the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 1, the mesoporous SiO2 nanoparticles show a spherical structure; when the concavo-convex curvature of the mesoporous SiO2 nanoparticles is 9 / 8, the mesoporous SiO2 nanoparticles show a convex water drop-shaped structure; When the mesoporous SiO2 nanoparticles are concave, the concave-convex curvature is the maximum distance from the center of the concave plane of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not concave; when the mesoporous SiO2 nanoparticles are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when they are not convex.

2. The method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature according to claim 1, characterized in that: The mass ratio of the hexadecyltrimethylammonium bromide to polyvinyl pyrrolidone is 1:45 to 1:

55.

3. The method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature according to claim 1, characterized in that: The silicon source is tetraethyl orthosilicate, and the volume ratio of the tetraethyl orthosilicate to ammonia water is 3:2 to 3:2.

3.

4. Mesoporous SiO2 nanoparticles prepared by the preparation method as described in any one of claims 1 to 3.

5. A method for preparing mesoporous SiO2 nanoparticles with adjustable concave-convex curvature, internally loaded with Fe3O4 and externally loaded with Au, characterized in that: Includes steps: Hexadecyltrimethylammonium bromide, polyvinylpyrrolidone, ethanol, Fe3O4 nanoparticle aqueous solution, sodium citrate solution, ammonia water and alcohol oil phase solvent are mixed and stirred to obtain a second emulsion; the volume ratio of ethanol, Fe3O4 nanoparticle aqueous solution, sodium citrate solution, ammonia water and alcohol oil phase solvent is 10:1:1:1:100; Adding a silicon source to the second emulsion and allowing it to react to obtain mesoporous SiO2 nanoparticles loaded with Fe3O4; The mesoporous SiO2 nanoparticles loaded with Fe3O4 and Au 3+ The reagent and the reducing agent react to obtain mesoporous SiO2 nanoparticles with internal Fe3O4 loading and external Au loading; wherein mesoporous SiO2 nanoparticles with internally loaded Fe3O4 and externally loaded Au having a target concave-convex curvature are prepared by using alcohol oil phase solvents with different alkane chain lengths; When the alcohol oil phase solvent is n-propanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 inside and Au outside is 1 / 2; Or when the alcohol oil phase solvent is n-butanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 3 / 4; Or when the alcohol oil phase solvent is n-pentanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 7 / 8; Or when the alcohol oil phase solvent is n-hexanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 1; Or when the alcohol oil phase solvent is n-heptanol, the concavo-convex curvature of the mesoporous SiO2 nanoparticles loaded with Fe3O4 internally and Au externally is 9 / 8; When the concavo-convex curvature of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is 1 / 2, 3 / 4 and 7 / 8, the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is a concave bowl-shaped structure; when the concavo-convex curvature of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is 1, the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is a spherical structure; when the concavo-convex curvature of the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is 9 / 8, the mesoporous SiO2 nanoparticles with internal Fe3O4 and external Au is a convex water drop-shaped structure; When the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are concave, the concave-convex curvature is the maximum distance from the center of the plane of the concave part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when not concave; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are spherical, the concave-convex curvature is 1; when the mesoporous SiO2 nanoparticles with internal load of Fe3O4 and external load of Au are convex, the concave-convex curvature is the maximum distance from the highest point of the convex part of the mesoporous SiO2 nanoparticles to the bottom / the diameter of the spherical mesoporous SiO2 nanoparticles when not convex.

6. Mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load prepared by the preparation method as claimed in claim 5.

7. Use of the mesoporous SiO2 nanoparticles with internal Fe3O4 load and external Au load as claimed in claim 6 in the photothermal catalytic oxidation reaction of benzyl alcohol.

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