A method for hydrophobic modification of the surface of magnetite nanoparticles

Abstract

This invention belongs to the field of surface hydrophobic technology and discloses a method for surface hydrophobic modification of magnetite (Fe3O4) magnetic nanoparticles. The method involves dispersing magnetite nanoparticles in an aqueous solution of tannic acid, stirring and filtering, and then washing with water and ethanol respectively. The tannic acid-coated magnetite nanoparticles are then dispersed in an ethanol solution of hexadecylamine, stirred and filtered, and washed with ethanol to obtain hydrophobic magnetite nanoparticles. The surface-modified hydrophobic magnetite nanoparticles of this invention can be dispersed in organic solvents such as benzene, toluene, and styrene, thus expanding their application range beyond the limitation of inability to disperse in organic solvents.

Description

Technical Field

[0001] This invention belongs to the field of nanoparticle surface hydrophobic technology, and particularly relates to a method for hydrophobic modification of the surface of magnetite magnetic nanoparticles. Background Technology

[0002] Due to their unique physicochemical properties, magnetite (Fe3O4) magnetic nanoparticles have wide applications in biomedicine, catalysis, microwave absorption, and magnetic recording. However, their small particle size, large specific surface area, and inherent magnetic properties make them prone to aggregation and oxidation by air. Furthermore, they are difficult to disperse in nonpolar solvents, significantly limiting their applications. Therefore, it is essential to modify the surface of magnetite magnetic nanoparticles to be hydrophobic. Currently, the general method for preparing hydrophobic magnetite magnetic nanoparticles involves surface modification to impart hydrophobicity. Yuan Xia et al. used oleic acid and octadecyltrimethylsilane to hydrophobize magnetite nanoparticles, resulting in higher stability in organic solvents. However, the stability of oleic acid-coated magnetite nanoparticles in organic solvents is poor, and they can only be dispersed in certain specific organic solvents. Other researchers have used fluorosilanes and tetraethyl silicate to hydrophobize the surface of magnetite magnetic nanoparticles, but the modified surface is neither hydrophilic nor oleophilic.

[0003] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0004] 1. Agglomeration problem: Due to the small particle size and large specific surface area of ​​magnetite nanoparticles, they are prone to agglomeration, which leads to poor particle dispersibility and limits their stability and effectiveness in applications.

[0005] 2. Solvent selection limitations: Current surface hydrophobication methods are only applicable to specific organic solvents. They have poor dispersibility in non-polar solvents or other organic solvents, which limits the application range of ferric oxide magnetic nanoparticles in different solvent systems.

[0006] 3. Stability issues: Some surface modifiers, such as oleic acid, have poor stability for magnetite magnetic nanoparticles in organic solvents, making them prone to aggregation and affecting the application performance of the nanoparticles.

[0007] 4. Reactivity and hydrophilicity issues: Although existing hydrophobic modification methods can make magnetite nanoparticles hydrophobic, the modified surface has neither good hydrophilicity nor oleophilicity, which limits its use in certain application areas.

[0008] Therefore, the technical problem to be solved is to develop a method that can effectively suppress agglomeration, improve the dispersibility of ferric oxide magnetic nanoparticles in various solvent systems, and provide stable and controllable surface modification so that the nanoparticles have both hydrophobicity and good hydrophilicity or oleophilicity, in order to meet their wide application needs in fields such as biomedicine, catalysis, microwave absorption and magnetic recording. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a method for hydrophobic modification of the surface of magnetite magnetic nanoparticles.

[0010] This invention is achieved by a method for hydrophobic modification of the surface of magnetite nanoparticles, specifically by sequentially modifying the surface of magnetite nanoparticles with tannic acid and hexadecylamine to obtain hydrophobic magnetite nanoparticles.

[0011] Furthermore, the method for hydrophobic modification of the surface of magnetite nanoparticles includes the following steps:

[0012] Step 1: Disperse the iron oxide nanoparticles in an aqueous tannic acid solution, stir and filter, and then wash with water and ethanol respectively.

[0013] Step 2: Disperse the tannic acid-coated iron oxide magnetic nanoparticles in an ethanol solution of hexadecylamine, stir and filter, and then wash with ethanol.

[0014] Furthermore, the mass ratio of tannic acid to iron oxide magnetic nanoparticles is 1:50-100, and the molar ratio of tannin to hexadecylamine is 1:5-10.

[0015] Furthermore, in step one, the volume of tannic acid aqueous solution corresponding to each gram of iron oxide powder is 100-200 mL, the mass concentration of tannin aqueous solution is 1-3%, and the stirring conditions are stirring at room temperature for 30-60 min.

[0016] Furthermore, in step two, the volume of hexadecylamine ethanol solution corresponding to each gram of iron oxide powder is 100-200 mL, the volume concentration of hexadecylamine ethanol solution is 1-3%, and the stirring conditions are 40-70℃ for 60-90 min.

[0017] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0018] First, this invention utilizes tannic acid, a natural product, to coat iron(III) oxide. Then, tannic acid reacts with hexadecylamine to form a Schiff base, thereby coating the surface of the iron(III) oxide nanoparticles with long alkyl chains, ultimately yielding hydrophobic iron(III) oxide magnetic nanoparticles that can be stably dispersed in organic solvents for a long time. This invention solves the defects of existing iron(III) oxide magnetic nanoparticles, such as easy aggregation and poor dispersion in nonpolar solvents. The method is simple, easy to operate, and the reaction conditions are mild, thus expanding the application range of iron(III) oxide magnetic nanoparticles.

[0019] The surface-modified hydrophobic magnetite nanoparticles of this invention can be dispersed in organic solvents such as benzene, toluene and styrene, thus expanding their application scope and eliminating the limitation caused by their inability to disperse in organic solvents.

[0020] Second, the specific technological advancements in each step are as follows:

[0021] Technological advancements in Step One:

[0022] 1. Surface modification using tannic acid: Tannic acid, as a natural organic compound, has a polyphenol structure and abundant hydroxyl functional groups. It can chemically react or adsorb with the surface of magnetite nanoparticles to achieve surface modification and improve the hydrophobicity of the nanoparticles.

[0023] 2. Use of tannic acid aqueous solution: Traditional methods often use organic solvents for surface modification, while this method uses tannic acid aqueous solution, which is not only environmentally friendly, but also convenient to operate and handle, reducing the use of organic solvents and environmental pollution.

[0024] 3. Optimization of stirring, filtration, and washing: By using appropriate stirring time and speed, sufficient contact and adsorption between tannic acid and nanoparticles can be achieved, resulting in better modification effects. Repeated washing steps can effectively remove residual tannic acid and impurities, improving the purity and stability of nanoparticles.

[0025] Technological advancements in step two:

[0026] 1. Use of hexadecylamine: Hexadecylamine is used for surface modification. It has a long carbon chain structure and can form a hydrophobic layer with the surface of tannic acid-coated iron oxide magnetic nanoparticles, further enhancing the hydrophobicity and stability of the nanoparticles.

[0027] 2. Dispersibility in ethanol solutions: Using ethanol as a solvent can effectively disperse nanoparticles and hexadecylamine, promoting their reaction and adsorption, thereby achieving surface modification. Ethanol is a widely used solvent that is easy to handle and process.

[0028] 3. Optimization of stirring, filtration, and washing: Appropriate stirring time and speed can promote the reaction and adsorption of hexadecylamine with nanoparticles, enhancing the modification effect. Repeated washing steps can remove residual hexadecylamine and impurities, improving the purity and stability of the nanoparticles.

[0029] Through the above technological advancements, this method achieves effective hydrophobic modification of magnetite magnetic nanoparticles, improving their dispersibility and stability, and providing broader possibilities for their application in fields such as biomedicine, catalysis, microwave absorption, and magnetic recording. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of the method for hydrophobic modification of the surface of magnetite magnetic nanoparticles provided in the embodiments of the present invention;

[0032] Figure 2 This is the XRD pattern of the magnetite nanoparticles provided in the embodiments of the present invention;

[0033] Figure 3 The present invention provides (a) the contact angle of unmodified iron oxide with water; and (b) the contact angle of surface-hydrophobically modified iron oxide with water.

[0034] Figure 4 These are (a) a dispersion diagram of surface-hydrophobic modified magnetite powder in water, and (b) a dispersion diagram of unmodified magnetite powder in water, provided by embodiments of the present invention.

[0035] Figure 5 These are (a) a dispersion diagram of surface-modified magnetite powder in styrene, an organic solvent, and (b) a dispersion diagram of unmodified magnetite powder in styrene, provided in the embodiments of the present invention.

[0036] Figure 6 It is a dispersion diagram of magnetite powder in styrene organic solvent under an applied magnetic field. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] To address the problems existing in the prior art, this invention provides a method for hydrophobic modification of the surface of magnetite magnetic nanoparticles. The invention will be described in detail below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, the method for hydrophobic modification of the surface of magnetite nanoparticles provided in this embodiment of the invention includes the following steps:

[0040] S101: Iron oxide nanoparticles are dispersed in an aqueous tannic acid solution, stirred and filtered, and then washed with water and ethanol respectively.

[0041] S102: Magnetite nanoparticles coated with tannic acid are dispersed in an ethanol solution of hexadecylamine, stirred and filtered, and then washed with ethanol.

[0042] The method for surface hydrophobic modification of magnetite nanoparticles provided in this invention uses tannic acid and hexadecylamine to modify the surface of the nanoparticles, thereby making them hydrophobic.

[0043] Step 1:

[0044] 1. Disperse the magnetite nanoparticles in an aqueous tannic acid solution. This can be achieved by dissolving an appropriate amount of tannic acid in water, adding the magnetite nanoparticles, and stirring to achieve uniform dispersion.

[0045] 2. Stir to promote full contact and adsorption between tannic acid and nanoparticles. The stirring time and speed can be adjusted according to the actual situation.

[0046] 3. Filter the mixture to separate the solid nanoparticles. Filter paper or other suitable filter materials can be used for filtration.

[0047] 4. Wash the filtered solid nanoparticles with solvents such as water and ethanol to remove residual tannins and impurities. Washing can be repeated multiple times until no significant color change is observed in the washing solution.

[0048] Step Two:

[0049] 1. Disperse tannic acid-coated iron(III) oxide magnetic nanoparticles in an ethanol solution of hexadecylamine. An appropriate amount of hexadecylamine can be added to ethanol, and the tannic acid-coated nanoparticles can be added to the mixture. Stirring is then performed to achieve uniform dispersion.

[0050] 2. Stirring is performed to promote the reaction and adsorption of hexadecylamine with nanoparticles. The stirring time and speed can be adjusted according to the actual situation.

[0051] 3. Filter the mixture to separate the solid nanoparticles. Filter paper or other suitable filter materials can be used for filtration.

[0052] 4. Wash the filtered solid nanoparticles with solvents such as ethanol to remove residual hexadecylamine and impurities. Washing can be repeated multiple times until no obvious color change occurs in the washing solution.

[0053] The above steps achieve hydrophobic modification of the surface of magnetite nanoparticles by sequentially using tannic acid and hexadecylamine, thus imbuing them with hydrophobic properties. The operating conditions and experimental parameters in the specific implementation plan can be adjusted and optimized according to specific circumstances.

[0054] Furthermore, the mass ratio of tannic acid to iron oxide magnetic nanoparticles is 1:50-100, and the molar ratio of tannin to hexadecylamine is 1:5-10.

[0055] Furthermore, in S101, the volume of tannic acid aqueous solution corresponding to each gram of iron oxide powder is 100-200 mL, the mass concentration of tannin aqueous solution is 1-3%, and the stirring conditions are stirring at room temperature for 30-60 min.

[0056] Furthermore, in S102, the volume of hexadecylamine ethanol solution corresponding to each gram of iron oxide powder is 100-200 mL, the volume concentration of hexadecylamine ethanol solution is 1-3%, and the stirring conditions are 40-70℃ for 60-90 min.

[0057] The present invention is implemented by coating the surface of magnetite nanoparticles with naturally sourced tannic acid, and then further treating the tannic acid-coated magnetite nanoparticles with hexadecylamine. The amino group in hexadecylamine forms a Schiff base with the previously coated tannic acid and is stably coated on the surface of magnetite nanoparticles. Due to the presence of long alkyl chains in hexadecylamine, hydrophobic magnetite nanoparticles that are easy to disperse in nonpolar solvents can be obtained.

[0058] The present invention will be further described below with reference to specific embodiments:

[0059] Example 1: A hydrophobic magnetic nanoparticle of iron oxide

[0060] The preparation method is as follows: 0.5g of magnetite nanoparticles are dispersed in 100ml of 1% tannic acid aqueous solution, ultrasonically dispersed for 40min, filtered, and washed with deionized water and anhydrous ethanol. Then, the magnetite nanoparticles coated with tannic acid are dispersed in 100ml of 1% hexadecylamine ethanol solution, ultrasonically dispersed at 40℃ for 60min, filtered, washed with ethanol and dried to obtain hydrophobic magnetite nanoparticles.

[0061] like Figure 2 The image shown is the XRD pattern of the magnetite nanoparticles provided in the embodiment of the present invention. Figure 3 The present invention provides (a) the contact angle of unmodified iron oxide with water; and (b) the contact angle of surface-hydrophobically modified iron oxide with water. Figure 4 These are (a) a dispersion diagram of surface-hydrophobic modified magnetite powder in water, and (b) a dispersion diagram of unmodified magnetite powder in water, provided by embodiments of the present invention. Figure 5 These are (a) a dispersion diagram of surface-modified magnetite powder in styrene, an organic solvent, and (b) a dispersion diagram of unmodified magnetite powder in styrene, provided in the embodiments of the present invention. Figure 6 It is a dispersion diagram of magnetite powder in styrene organic solvent under an applied magnetic field.

[0062] Example 2: Surface hydrophobic modification of iron oxide magnetic nanoparticles

[0063] Step 1:

[0064] 1. Disperse magnetite nanoparticles (approximately 10 nm in diameter) in a deionized aqueous solution containing 5 mg / mL tannic acid.

[0065] 2. Use a magnetic stirrer to stir the mixture at 200 rpm at room temperature for 20 minutes to promote the contact and adsorption of tannic acid with nanoparticles.

[0066] 3. Filter the mixture using filter paper or other suitable filter material to separate solid nanoparticles.

[0067] 4. Wash with deionized water, repeating the process 2-3 times until there is no obvious color change in the washing solution.

[0068] 5. The filtered solid nanoparticles are dried in a vacuum to obtain magnetic nanoparticles of iron oxide coated with tannic acid.

[0069] Step Two:

[0070] 1. Disperse tannic acid-coated iron oxide magnetic nanoparticles in an ethanol solution containing 0.2 wt% hexadecylamine.

[0071] 2. Use a magnetic stirrer to stir the mixture at 300 rpm at room temperature for 30 minutes to promote the reaction and adsorption of hexadecylamine with nanoparticles.

[0072] 3. Filter the mixture using filter paper or other suitable filter material to separate solid nanoparticles.

[0073] 4. Wash with ethanol, repeating the operation 2-3 times until there is no obvious color change in the washing solution.

[0074] 5. The filtered solid nanoparticles are dried in a vacuum to obtain hydrophobic magnetite nanoparticles.

[0075] Example 3: Hydrophobic modification of iron oxide magnetic nanoparticles in a bilayer

[0076] Step 1:

[0077] 1. Magnetic nanoparticles of iron oxide (approximately 20 nm in diameter) were dispersed in an ethanol solution containing 10 mg / mL of nitrocellulose (NC).

[0078] 2. Use an ultrasonic processor to sonicate the mixture to help the nanoparticles mix and disperse fully with nitrocellulose.

[0079] 3. Centrifuge to separate the dispersed nanoparticles from the solvent.

[0080] 4. The obtained nanoparticles are dried in a vacuum to obtain magnetic nanoparticles of iron oxide with nitrocellulose coated on the surface.

[0081] Step Two:

[0082] 1. Disperse cellulose nitrate-coated iron oxide magnetic nanoparticles in an ethanol solution containing 1 mg / mL hexadecyltrimethylammonium chloride (CTAB).

[0083] 2. The mixture was ultrasonically treated using an ultrasonic processor to promote the reaction and adsorption of hexadecyltrimethylammonium chloride with nanoparticles.

[0084] 3. Centrifuge to separate the dispersed nanoparticles from the solvent.

[0085] 4. The obtained nanoparticles are dried in a vacuum to obtain magnetic nanoparticles of iron oxide with a double layer of hydrophobicity.

[0086] The above implementation scheme successfully achieved surface hydrophobic modification of magnetite nanoparticles.

[0087] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for surface hydrophobic modification of magnetite magnetic nanoparticles, characterized by, The method for modifying the surface of the ferroferric oxide magnetic nanoparticles to be hydrophobic comprises the following steps:

2. The method of surface hydrophobic modification of magnetite magnetic nanoparticles according to claim 1, characterized in that, The method for modifying the surface of the ferroferric oxide magnetic nanoparticles to be hydrophobic comprises the following steps: Step one, dispersing the ferroferric oxide nanoparticles in a tannic acid aqueous solution, stirring, filtering, and then washing with water and ethanol respectively; Step two, dispersing the ferroferric oxide magnetic nanoparticles coated with tannic acid in a hexadecylamine ethanol solution, stirring, filtering, and then washing with ethanol.

3. The method for hydrophobic modification of the surface of magnetite nanoparticles as described in claim 2, characterized in that, The mass ratio of tannic acid to ferroferric oxide magnetic nanoparticles is 1:50-100, and the molar ratio of tannic acid to hexadecylamine is 1:5-10.

4. The method of surface hydrophobic modification of magnetite magnetic nanoparticles according to claim 2, wherein the surface hydrophobic modification of magnetite magnetic nanoparticles is carried out by the reaction of magnetite magnetic nanoparticles with a compound of formula (I) in the presence of a solvent. In step one, the volume of the tannic acid aqueous solution corresponding to each gram of ferroferric oxide powder is 100-200 mL, the mass concentration of the tannic acid aqueous solution is 1-3%, and the stirring condition is stirring at room temperature for 30-60 min.

5. The method for hydrophobic modification of the surface of magnetite nanoparticles as described in claim 2, characterized in that, In step two, the volume of the hexadecylamine ethanol solution corresponding to each gram of ferroferric oxide powder is 100-200 mL, the volume concentration of the hexadecylamine ethanol solution is 1-3%, and the stirring condition is stirring at 40-70℃ for 60-90 min.

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