Method for preparing ferroferric oxide magnetic nanocluster under normal pressure

Abstract

The invention discloses a synthesis method for preparing a Fe3O4 magnetic nanocluster with the particle size of 82-174 nm under the conditions of normal pressure and air atmosphere. The method comprises the following steps: step 1, by taking ethylene glycol as an inert solvent, sequentially adding and dissolving an iron source, alkali metal acetate, a dispersing agent, alkali metal hydroxide and trace water into a glass container to obtain a mixed pre-polymerization liquid system; and step 2, putting the glass container filled with the pre-polymerization liquid into a drying oven, standing at a high temperature, and reacting to synthesize the Fe3O4 magnetic nanocluster. According to the method, an alkali-rich water-deficient strategy is adopted, the size and crystallinity of the nanoparticles are accurately controlled by regulating and controlling the addition amount of water, a high-pressure reaction kettle is not needed, and equipment potential safety hazards caused by pollution of a Teflon lining and high pressure are effectively avoided. The prepared magnetic nanocluster has excellent monodispersity, superparamagnetism and adjustable photonic band gap characteristics, and is suitable for the fields of construction of magnetic response photonic crystals, visual detection of irregular magnetic fields and the like.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a method for preparing magnetic nanoclusters of iron oxide under normal pressure conditions. Background Technology

[0002] Submicron-sized magnetic nanoclusters are strongly magnetic materials capable of directional movement under an applied magnetic field (300–300 Gs), showing great promise for applications in sensing, catalysis, and biology. Currently, traditional one-step preparation methods for magnetic nanoclusters largely rely on high-pressure reactors, which suffer from high equipment costs, operational hazards, potential Teflon material contamination, and poor reusability. Furthermore, existing processes typically require an inert atmosphere, making them complex and limiting large-scale production and application. Therefore, constructing magnetic nanoclusters under mild conditions is an important direction in the synthesis of magnetic nanomaterials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for efficiently preparing magnetic nanoclusters under ambient pressure without the need for high-pressure reaction equipment. This invention utilizes a "rich alkali, poor water" strategy to achieve one-pot synthesis of magnetic nanoclusters in a common glass container, effectively avoiding Teflon liner contamination and safety hazards associated with high pressure equipment. This method is simple, low-cost, and environmentally friendly, and allows for precise control of nanoparticle size and crystallinity by adjusting the amount of water added.

[0004] This invention is achieved through the following specific technical solutions:

[0005] Step 1: Prepare the reaction mixture solution:

[0006] In a glass container, an iron source, alkali metal acetate, dispersant, reducing agent, and a certain amount of water are dissolved in an inert solvent and stirred until homogeneous. Subsequently, an alkali metal hydroxide is added to form a mixed solution.

[0007] Step 2: Under normal pressure and air atmosphere, the mixed solution is heated and allowed to stand in an oven for reaction;

[0008] Step 3: After cooling, washing and drying, Fe3O4 magnetic nanoclusters are obtained.

[0009] In step 1, the iron source is anhydrous ferric chloride, the alkali metal acetate is sodium acetate, the dispersant is sodium poly(4-styrenesulfonic acid-co-maleic acid), the reducing agent is L(+)-ascorbic acid, and the inert solvent is ethylene glycol, with a dosage ratio of 0.65g:3.0g:1.05g:12mg:40mL; the amount of water added is 0-200μL, used to control the size of the magnetic nanoclusters within the range of 70-200nm. In step 2, the alkali metal hydroxide is NaOH, and the dosage is 0.6g.

[0010] In step 2, the reaction temperature is 170–200°C, and the reaction time is 5–9 hours. The reaction is carried out under normal pressure and air atmosphere, without the need for inert gas protection.

[0011] In step 3, the reaction temperature is 170–200°C and the reaction time is 5–9 hours; the reaction is carried out under normal pressure and air atmosphere, without the need for inert gas protection.

[0012] In step 4, the amount of detergent used per wash is 30 mL, the phase separation method is magnetic separation, and the final dispersion (water) volume is 30 mL. The prepared magnetite nanoclusters exhibit tunable size, good monodispersity, and superparamagnetism.

[0013] The magnetic nanoclusters constructed in this invention are used to construct magnetically responsive photonic crystals. A 10 mg / mL aqueous solution of the magnetic nanoclusters is thoroughly sonicated and shaken to mix. 200 μL of the dispersion is dropped onto a glass slide, and a spacer approximately 150 μm thick is placed inside the slide. After covering with a coverslip, the reflectance spectral peaks are recorded using a fiber optic spectrometer, and the structural colors are recorded using a camera. A vertical external magnetic field is applied directly below the glass slide, with the magnetic field strength adjusted to 81.5–502 Gs. The changes in the reflectance spectral peaks and structural colors are observed and recorded. The beneficial effects of this invention are:

[0014] (1) Simple process, mild conditions and low cost: The magnetic nanocluster preparation method provided by the present invention is carried out under normal pressure and air atmosphere, without the need for high pressure reactor, inert gas protection or complex equipment, which significantly reduces equipment investment and operating costs, and is suitable for laboratory and industrial large-scale preparation.

[0015] (2) Avoid Teflon contamination and have good reproducibility: The use of glass containers instead of traditional Teflon-lined autoclaves effectively avoids the contamination problems that Teflon materials may cause under high temperature and high pressure, and improves the purity of the product and the consistency between batches.

[0016] (3) Size and performance can be precisely controlled: By using the "rich alkali and poor water" strategy, the size of magnetic nanoclusters (82-174nm) can be precisely controlled simply by adjusting the amount of water added. The operation is simple, highly repeatable, and has good process flexibility. Attached Figure Description

[0017] Figure 1 : Transmission electron microscopy (TEM) and high-magnification transmission electron microscopy (HRTEM) images of the magnetic nanoclusters prepared in Example 1;

[0018] Figure 2 X-ray diffraction images and hysteresis curves of the magnetic nanoclusters prepared in Example 1;

[0019] Figure 3 TEM images of magnetic nanoclusters of different sizes prepared in Example 2;

[0020] Figure 4 Images and reflection spectra of the aqueous solution of magnetic nanoclusters under parallel magnetic fields of 81.5–502 Gs. Detailed Implementation

[0021] Example 1: Preparation of ferric oxide magnetic nanoclusters

[0022] In a 250 mL Erlenmeyer flask, add 40 mL of ethylene glycol, 0.65 g of anhydrous ferric chloride (FeCl3), 3.0 g of anhydrous sodium acetate (NaAc), 1.05 g of poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSMA), 12 mg of L(+)-ascorbic acid, and 50 μL of water. Stir magnetically until completely dissolved. Add 0.6 g of NaOH to form a dark, transparent solution. After removing the stir bar, place the solution in a 190 °C oven and react for 9 hours. After cooling, wash three times each with an ethanol / water (1:1) mixture and deionized water, and finally disperse in 30 mL of water for later use.

[0023] Example 2: Effect of water addition on the size of magnetic nanoclusters

[0024] Magnetic nanoclusters were prepared by adding 0, 25, and 120 μL of water, respectively, according to the method in Example 1. TEM results showed that the average sizes of the magnetic nanoclusters were 174, 166, 138, and 82 nm, respectively, confirming a negative correlation between water content and particle size.

[0025] Example 3: Application of magnetic nanoclusters in the preparation of magnetically responsive photonic crystals

[0026] A 10 mg / mL aqueous solution of iron(III) oxide nanoclusters was thoroughly sonicated and vibrated to mix. 200 μL of the dispersion was dropped onto a glass slide, and a 150 μm thick separator was placed inside the slide. After covering with a coverslip, the reflectance spectral peaks and structural colors were recorded. Subsequently, a vertical external magnetic field was applied directly below the glass slide, with the magnetic field strength adjusted to 81.5–502 Gs, and the changes in the reflectance spectral peaks and structural colors were recorded. Figure 4 As shown, a photonic crystal solution with controllable structural color, ranging from purple to orange-red, can be successfully constructed.

[0027] Example 4: Application of magnetic nanoclusters in the preparation of magnetically responsive photonic crystals

[0028] A 30 mg / mL aqueous solution of iron(III) oxide nanoclusters was thoroughly sonicated and shaken to mix. 200 μL of the dispersion was dropped onto a glass slide, and a 150 μm thick diaphragm was placed inside the slide. After covering with a coverslip, the reflectance spectral peak and structural color were recorded. Subsequently, an external magnetic field was applied vertically below the glass slide, with the magnetic field strength adjusted to 81.5–502 Gs, and the changes in the reflectance spectral peak and structural color were recorded.

[0029] The above description is merely a preferred embodiment of the present invention, demonstrating the basic principles, core processes, and advantages of preparing magnetic nanoclusters under ambient pressure conditions. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above. In addition to the above embodiments, several adjustments and modifications can be made to the present invention without departing from its design principles and scope, and other feasible preparation paths and conditions can also be adopted. All equivalent substitutions or technical transfers based on the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention. The scope of protection claimed by the present invention is jointly determined by the appended claims and their equivalent technical solutions. Some of the technical means involved can be implemented using existing technologies, and will not be elaborated here.

Claims

1. A method for preparing Fe3O4 magnetic nanoclusters, characterized in that, Includes the following steps: Step 1: In a glass container, dissolve the iron source, alkali metal acetate, dispersant, reducing agent and a certain amount of water in an inert solvent in sequence, and stir until homogeneous; Step 2: Add alkali metal hydroxide to form a mixed solution; Step 3: Under normal pressure and air atmosphere, the mixed solution is heated and reacted in an oven for a period of time. Step 4: After cooling, wash three times each with ethanol and water, and finally disperse in water to obtain an aqueous solution of Fe3O4 magnetic nanoclusters.

2. The method according to claim 1, characterized in that, In step 1, the iron source is anhydrous ferric chloride, the alkali metal acetate is sodium acetate, the dispersant is sodium poly(4-styrenesulfonic acid-co-maleic acid), the reducing agent is L(+)-ascorbic acid, and the inert solvent is ethylene glycol. The ratio of their amounts is 0.65g:3.0g:1.05g:12mg:40mL.

3. The method according to claim 1, characterized in that, In step 1, the amount of water added is 0 to 200 μL, which is used to control the size of the magnetic nanoclusters in the range of 82 to 174 nm.

4. The method according to claim 1, characterized in that, In step 2, the alkali metal hydroxide is NaOH, and the amount used is 0.6g.

5. The method according to claim 1, characterized in that, In step 3, the reaction temperature is 170–200°C and the reaction time is 5–9 hours; the reaction is carried out under normal pressure and air atmosphere, without the need for inert gas protection.

6. The method according to claim 1, characterized in that, In step 4, the amount of detergent used per wash is 30 mL, the phase separation method is magnetic separation, and the amount of final dispersion (water) is 30 mL.

7. A magnetic nanocluster prepared by any one of claims 1-6, characterized in that, It has adjustable size, good monodispersity and superparamagnetism.

8. The use of the magnetic nanoclusters constructed by the construction method according to claims 1-6 for constructing magnetically responsive photonic crystals, characterized in that, The construction steps are as follows: (1) The aqueous solution of magnetic nanoclusters with a mass fraction of 10 mg / mL was thoroughly sonicated and shaken to mix. 200 μL of the dispersion was dropped onto a glass slide and a spacer of about 150 μm was placed inside the glass slide. After covering with a glass cover glass, its reflection spectrum peak was recorded with a fiber optic spectrometer and its structural color was recorded with a camera. (2) Apply an external magnetic field in the vertical direction directly below the glass slide, adjust the magnetic field strength to 81.5-502 Gs, and observe and record the changes in the reflection spectrum peak and structural color.

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