Preparation method and evaluation method of high-stability iron oxide / graphene nanocomposite

Abstract

The application discloses a preparation method and an evaluation method of high-stability iron oxide / graphene nanocomposite, and relates to the technical field of nanomaterials. The expanded graphite is dissolved in DMF and left overnight, a multilayer graphene solution is prepared by adding water after ultrasonic treatment of the mixture in an ice bath environment for 2.5-3 hours; FeCl3.4H2O and anhydrous sodium acetate are weighed and added into the multilayer graphene solution, and the mixture is stirred intensively to obtain a reaction precursor solution; the reaction precursor solution is kept in a water bath, cooled to room temperature, and subjected to high-speed centrifugal separation to obtain a wet sample; the wet sample is washed by using anhydrous ethanol and pure water, and dried to obtain a red-brown powder. By loading Fe2O3 particles on graphene, the two-dimensional sheet structure, high thermal conductivity and high dispersibility of the graphene can effectively prevent the agglomeration of the nanoparticles, ensure the uniform distribution of the particles, improve the stability of the nanomaterials in an aqueous solution, improve the light absorption capacity of the nanomaterials, and make the materials more stable in the photothermal conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a preparation method and an evaluation method of a high-stability iron oxide / graphene nanocomposite material. Background Art

[0002] γ-Fe2O3 is a ferromagnetic material with high magnetic permeability and magnetic saturation, which makes it widely used in magnetic materials and data storage devices. Due to its high surface activity, γ-Fe2O3 is often used as a catalyst or catalyst support. Under certain conditions, γ-Fe2O3 is more stable than α-Fe2O3 and is not easily oxidized or reduced. At the nanoscale, γ-Fe2O3 particles can exhibit superparamagnetism, which has potential applications in biomedicine (such as magnetic resonance imaging contrast agents). However, the absorbance of nanomaterials often fluctuates with concentration, particularly at high or low concentrations, where the absorption performance decreases significantly due to problems such as particle agglomeration and sedimentation. At low concentrations, the nanomaterial content in the solution is insufficient, resulting in low light absorption efficiency. At high concentrations, interparticle interactions increase, leading to the formation of aggregates, which reduces light absorption capacity or even inactivates it. Therefore, there is an urgent need to develop highly stable γ-Fe2O3-containing nanomaterials with a stable absorbance-to-concentration relationship, making them easier to select and use based on their stability. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing a highly stable iron oxide / graphene nanocomposite material and an evaluation method thereof, so as to solve the problem that the existing Fe2O3 nanomaterials have poor stability, especially the unstable absorbance with concentration change.

[0004] To solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a highly stable iron oxide / graphene nanocomposite material, characterized in that it comprises the following steps:

[0005] S1. The expanded graphite was dissolved in DMF and allowed to stand overnight, the expanded graphite relative to DMF was 2.0 to 2.5 mg / ml;

[0006] S2. After the mixture in step S1 was ultrasonically treated in an ice bath for 2.5 to 3 hours, water was added to prepare a multilayer graphene solution;

[0007] S3. FeCl3·4H2O and anhydrous sodium acetate were weighed separately and added to the multilayer graphene solution. The mixture was vigorously stirred at a speed of 500-600 r / min for 10-15 min to obtain a reaction precursor solution.

[0008] S4. After the reaction precursor solution is kept at 85-95℃ water bath for 1.5-2 hours, it is cooled to room temperature and high-speed centrifugal separation is carried out to obtain a wet sample;

[0009] S5. After the wet sample is washed with anhydrous ethanol and pure water, drying is carried out to obtain a red-brown powder.

[0010] Further, the water adding amount in step S2 is 1:4-5 in volume ratio to DMF.

[0011] Further, the mass ratio of FeCl3·4H2O, anhydrous sodium acetate and expanded graphite in step S3 is 1.25-5:2.5-10:1.

[0012] Further, the wet sample is washed for 3 times and dried at 60-80℃ for 18-24 hours in step S5.

[0013] Further, the red-brown powder is a nanocomposite of γ-Fe2O3 and graphene.

[0014] Further, the nanocomposite stability analysis step is as follows:

[0015] (1) Different concentrations of samples are prepared according to concentration gradient and their absorbance is tested, and the function relationship y=f(x) of absorbance x and concentration y is constructed by interpolation method.

[0016] (2) The absorbance of the sample with original concentration m is tested after standing for a certain time, and the current concentration m0 at this time is calculated according to the function relationship, and the stability n of the sample at this time is m0 / m, and the larger the n value is, the higher the sample stability is.

[0017] Compared with the prior art, the beneficial effects of the present application are:

[0018] 1. The present application dissolves expanded graphite in DMF, stands for a period of time, and then ultrasonically prepares a multilayer graphene solution under ice bath, and then FeCl3·4H2O and anhydrous sodium acetate are added and stirred vigorously, the iron salt is hydrolyzed to generate Fe(OH)3 and hydrogen ions in water, and anhydrous sodium acetate is hydrolyzed to generate acetate molecules and hydroxide ions, the acetate ions adjust the pH value, maintain an alkaline environment and weaken the particle aggregation, which is conducive to the generation of γ-Fe2O3, and the rapid formation and aggregation of iron ions and high-speed stirring generate more γ-Fe2O3. The precursor solution is fully mixed by sufficient stirring, and the target product can be obtained by heating at 90℃ water bath for 2h, and the reaction is simplified.

[0019] 2. The present invention loads Fe2O3 particles on graphene. The two-dimensional layer structure, high thermal conductivity and high dispersibility of graphene can effectively prevent the agglomeration of nanoparticles, ensure the uniform distribution of particles, improve the stability of nanomaterials in aqueous solution, and improve the light absorption capacity of nanomaterials, making the performance of the material in photothermal conversion more stable and extending its service life.

[0020] 3. By rationally designing the Fe2O3 content and graphene ratio, the present invention maintains excellent light absorption across a wide concentration range, ensuring a more pronounced functional relationship between the material's absorbance at different concentrations. In particular, at higher concentrations, the material's absorbance exhibits a gradual increase, with minimal agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 These are the SEM and EDS images of graphene, Fe2O3 and γ-Fe2O3 / graphene nanocomposite materials in Example 1.

[0022] Figure 2 This is the XRD diffraction pattern of the γ-Fe2O3 / graphene nanocomposite material prepared in Example 1.

[0023] Figure 3 These are electron microscope images and EDS images of γ-Fe2O attached to graphene in the embodiment.

[0024] Figure 4 This is a graph showing the sedimentation of the sample over time.

[0025] Figure 5 This is the relationship between sample concentration and stability. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Example 1

[0028] 1) Weigh 0.5 g of expanded graphite and dissolve it in 200 ml of DMF solution and let it stand overnight.

[0029] 2) The solution was sonicated for 180 min (in an ice bath during sonication and ensuring that the liquid level was higher than the solution level), and then 50 ml of water was added to prepare a multilayer graphene solution.

[0030] 3) Weighing 0.625 g of FeCl3·4H2O and 1.25 g of anhydrous sodium acetate were respectively added to the multilayer graphene solution, and vigorously stirred at a speed of 500 r / min for 10 min to obtain a reaction precursor solution.

[0031] 4) Place the reaction precursor solution in a water bath at 90°C for 2 hours. To ensure sufficient reaction, the water bath liquid level must be higher than the solution level.

[0032] 5) The solution after the reaction was cooled to room temperature and then placed in a high-speed centrifuge for separation to obtain a wet sample, which was then washed three times with anhydrous ethanol and purified water. The washed sample was dried at 60° C. for 24 h to obtain a reddish-brown powder sample G1.

[0033] Example 2

[0034] 1) Weigh 0.5 g of expanded graphite and dissolve it in 200 ml of DMF solution and let it stand overnight.

[0035] 2) The solution was sonicated for 180 min (in an ice bath during sonication and ensuring that the liquid level was higher than the solution level), and then 50 ml of water was added to prepare a multilayer graphene solution.

[0036] 3) 1.25 g of FeCl 3 · 4H 2 O and 2.5 g of anhydrous sodium acetate were weighed and added to the multilayer graphene solution, and the mixture was vigorously stirred at a speed of 500 rpm for 10 min to obtain a reaction precursor solution.

[0037] 4) Place the reaction precursor solution in a water bath at 90°C for 2 hours. To ensure sufficient reaction, the water bath liquid level must be higher than the solution level.

[0038] 5) The reaction solution was cooled to room temperature and then placed in a high-speed centrifuge for separation to obtain a wet sample, which was then washed three times with anhydrous ethanol and purified water. The washed sample was dried at 60° C. for 24 h to obtain a reddish-brown powder sample G2.

[0039] Example 3

[0040] 1) Weigh 0.5 g of expanded graphite and dissolve it in 200 ml of DMF solution and let it stand overnight.

[0041] 2) The solution was sonicated for 180 min (in an ice bath during sonication and ensuring that the liquid level was higher than the solution level), and then 50 ml of water was added to prepare a multilayer graphene solution.

[0042] 3) 1.875 g of FeCl3·4H2O and 3.75 g of anhydrous sodium acetate were weighed and added to the multilayer graphene solution, and the mixture was vigorously stirred at a speed of 500 r / min for 10 min to obtain a reaction precursor solution.

[0043] 4) The reaction precursor solution was placed in a 90°C water bath for 2 hours to ensure the reaction was complete. The water bath level should be higher than the solution level.

[0044] 5) The solution after reaction was cooled to room temperature and then placed in a high-speed centrifuge to separate the wet sample. The sample was then washed with anhydrous ethanol and purified water three times. The washed sample was dried at 60°C for 24 hours to obtain a red-brown powder sample G3.

[0045] Example 4

[0046] 1) 0.5g of expanded graphite was dissolved in 200ml of DMF solution and left overnight.

[0047] 2) After the solution was ultrasonicated for 180 minutes (with an ice bath during ultrasonication and ensuring that the liquid level was higher than the solution level), 50ml of water was added to obtain a multi-layer graphene solution.

[0048] 3) 2.5g of FeCl3-4H2O and 5g of anhydrous sodium acetate were weighed and added to the multi-layer graphene solution, and vigorous stirring was performed at a speed of 500r / min for 10 minutes to obtain a reaction precursor solution.

[0049] 4) The reaction precursor solution was placed in a 90°C water bath for 2 hours to ensure the reaction was complete. The water bath level should be higher than the solution level.

[0050] 5) The solution after reaction was cooled to room temperature and then placed in a high-speed centrifuge to separate the wet sample. The sample was then washed with anhydrous ethanol and purified water three times. The washed sample was dried at 60°C for 24 hours to obtain a red-brown powder sample G4.

[0051] Reference Figure 1 , Figure 1 (a) shows the SEM image of the multi-layer graphene prepared in Example 1. The graphene presents a sheet-like structure with a large number of specific wrinkles on the surface, and some layers are connected to each other to form a three-dimensional network framework. This sheet-like structure and wrinkle provide abundant surface active sites for the subsequent attachment of Fe2O3 particles, and also help to prevent the agglomeration of nanoparticles.

[0052] Figure 1 (b) shows the SEM image of Fe2O3 nanoparticles. The Fe2O3 particles are spherical nanoparticles with a particle size of 6nm to 10nm. However, due to the van der Waals force between the nanoparticles and their inherent magnetic effect, the Fe2O3 particles tend to agglomerate into larger clusters with a size range of 200nm to 500nm.

[0053] Figure 1(c) shows an SEM image of the γ-Fe2O3 / graphene nanocomposite. In this composite, Fe2O3 particles are uniformly attached to the multilayer graphene surface. Compared to pure Fe2O3, the composite exhibits significantly less particle agglomeration. Small particles with a diameter of approximately 10 nm are dispersed on the graphene surface. These particles are bound to the graphene through molecular forces, forming a stable structure that ensures the material's dispersibility and photothermal conversion performance.

[0054] Figure 1 (d) is a magnified partial image of the γ-Fe2O3 / graphene nanocomposite. The magnified image further reveals dispersed small γ-Fe2O3 particles (approximately 10 nm in diameter) uniformly covering the graphene surface, indicating that Fe2O3 particle agglomeration in the composite has been significantly reduced. Furthermore, some small aggregates ranging in size from 80 to 200 nm have also appeared on the surface, presumably formed by excess γ-Fe2O3 particles adsorbed on the graphene surface.

[0055] Figure 1 (e) is an energy dispersive spectroscopy (EDS) analysis of the γ-Fe2O3 / graphene nanocomposite material. This diagram illustrates the elemental composition of the sample, showing that the main elements in the sample are C, O, and Fe, consistent with the preparation process of the present invention.

[0056] refer to Figure 2 The structure and chemical composition of the γ-Fe2O3 / graphene nanocomposite material were further verified by analyzing the XRD diffraction pattern of the product in Example 1. The results are shown in the figure. In the figure, the diffraction peaks of the graphene curve at 26.3°, 42.2°, 44.3° and 54.5° correspond to the (002), (100), (101) and (004) crystal planes, indicating that they are the diffraction peaks of graphene (JCPD Card 41-1487). The diffraction peaks of the Fe2O3 curve at 30°, 35.4°, 43°, 56.9° and 62.5° correspond to the (220), (311), (400), (511) and (440) crystal planes, indicating that they are the diffraction peaks of magnetite (JCPD Card 19-0629).

[0057] The diffraction peaks at 26.3°, 42.2°, 44.3°, and 54.5° of the composite material curve are the diffraction peaks of graphene (JCPDCard41-1487), corresponding to its (002), (100), (101), and (004) crystal planes. The diffraction peaks at 30°, 35.4°, 43°, 56.9°, and 62.5° are the diffraction peaks of magnetite (JCPD Card 19-0629), corresponding to its (220), (311), (400), (511), and (440) crystal planes. In addition to the diffraction peaks of these two phases, no other impurity peaks were observed, indicating that the prepared composite material is γ-Fe2O3 and has a high purity.

[0058] refer to Figure 3 , Figure 3 The electron microscope images and EDS images of Fe2O3 attached to the graphene sheet in G1-G4 are respectively. It can be seen from Figure (a) that G1 has almost no large agglomerates, and the Fe2O3 particles are evenly distributed on the graphene sheet. Compared with G1, G2 (b) has a small amount of small Fe2O3 agglomerates, and the size of the agglomerates is about 100nm. The surface of G3 (c) is covered with Fe2O3, and there are also many agglomerates on the surface, and the size of the agglomerates is between 100-150nm. The surface of G4 is completely occupied by Fe2O3 particles, and the size of the agglomerates is further increased, ranging from 200-300nm, which is close to Figure 1 (b) The size of pure Fe2O3 nanoparticles. This is because as the amount of Fe2O3 increases, after the graphene sheet is fully attached, the Fe2O3 particles will attract each other due to the inherent magnetism between the magnetic particles, resulting in a large number of them agglomerating on the graphene surface. Table 2 shows the composition analysis results of EDS. As can be seen from the table, as the proportion of iron source increases, the iron and oxygen elements gradually increase, while the carbon element gradually decreases. This is confirmed by the SEM analysis results, that is, from G1 to G4, on the same mass of graphene sheet, the amount of Fe2O3 attached gradually increases, and large Fe2O3 agglomerates gradually appear, which may cause changes in the thermal properties of the sample.

[0059] Table 2

[0060]

[0061] Example 5

[0062] In order to study the stability of samples G1-G4, aqueous solutions of γ-Fe2O3 / Graphene composite nanomaterials with different mass concentrations were left at room temperature for 7 days to observe their sedimentation. The results are as follows: Figure 4As shown in the figure, the color of the composite nanomaterial becomes significantly lighter after standing for 7 days, indicating that some larger nanoparticle agglomerates have precipitated, reducing the solid content in the base liquid, which will affect the optical absorption properties of the nanofluid.

[0063] For further quantitative analysis, ultraviolet spectrophotometry and observation were used to analyze and evaluate the stability of the nanocomposite material. The specific steps are as follows:

[0064] (1) Prepare samples of different concentrations according to a concentration gradient and measure their absorbance. Use the interpolation method to construct the functional relationship y = f(x) between absorbance x and concentration y.

[0065] For the G1 sample, 50 ppm was used as the starting point and 50 ppm as the concentration gradient. The absorbance of 9 samples with concentrations ranging from 50 to 500 ppm was tested, and the functional relationship between absorbance x and concentration y was obtained by fitting based on the interpolation method.

[0066] G2, G3, and G4 are tested in the same way as above, and the functional relationships are as follows:

[0067] G1: y = 8x 2 +145x+13

[0068] G2: y = 60x 2 +30x+60

[0069] G3: y = 21x 2 +120x+8

[0070] G4: y = -3x 2 +175x+17

[0071] (2) After the sample with an original concentration of m is left to stand for a certain period of time, its absorbance is tested and the current concentration m0 is calculated based on the functional relationship. At this time, the stability of the sample is n = m0 / m. The larger the n value, the higher the sample stability.

[0072] Depend on Figure 5 As shown, with increasing Fe₂O₃ loading, the stability of the nanocomposites of each sample first increases and then decreases. Sample G1 exhibits the worst stability at lower concentrations, with concentrations of the 100ppm and 200ppm samples dropping below 30% after 7 days, peaking at 43.87% at 300ppm. Sample G2 exhibits the best stability compared to the other samples, reaching a maximum of 75.88% at 100ppm. Furthermore, the stability of the nanocomposites decreases with increasing mass concentration, reaching a minimum of 35.84% at 400ppm. G3's stability is least affected by concentration, with a stability variance of approximately 8.772 after 7 days.

[0073] While the application has been described with reference to the exemplary embodiments thereof, it is to be understood that the application is not limited to the embodiments discussed herein, but is applicable to a variety of other modifications and embodiments within the scope of the application. More particularly, modifications and variations are possible in the constituent materials, among other things, of the application based on the description as provided herein and the attached accompanying drawings. In addition to variations to the constituent materials, other uses will be apparent to those of skill in the art from consideration of the specification and practice of the application disclosed herein.

Claims

1. A method for preparing a highly stable iron oxide / graphene nanocomposite material, characterized in that: The steps include: S1. The expanded graphite was dissolved in DMF and allowed to stand overnight, the expanded graphite relative to DMF was 2.0 to 2.5 mg / ml; S2. After the mixture in step S1 was ultrasonically treated in an ice bath for 2.5 to 3 hours, water was added to prepare a multilayer graphene solution; S3. FeCl3·4H2O and anhydrous sodium acetate were weighed separately and added to the multilayer graphene solution. The mixture was vigorously stirred at a speed of 500-600 r / min for 10-15 min to obtain a reaction precursor solution. S4. The reaction precursor solution was incubated in a water bath at 85-95°C for 1.5-2 hours, cooled to room temperature, and centrifuged at high speed to obtain a wet sample; S5. The wet sample was washed with anhydrous ethanol and purified water, and then dried to obtain a reddish-brown powder.

2. The method according to claim 1, wherein: The volume ratio of water added to DMF in step S2 is 1:4-5.

3. The method according to claim 1, wherein: In step S3, the mass ratio of FeCl3·4H2O, anhydrous sodium acetate and expanded graphite is 1.25-5:2.5-10:

1.

4. The method according to claim 1, wherein: In the step S5, the product is washed three times and then dried at 60-80° C. for 18-24 hours.

5. The method according to claim 1, wherein: The reddish-brown powder is a nanocomposite material of gamma-Fe2O3 and graphene.

6. The method according to claim 1, wherein: The steps for analyzing the stability of the nanocomposite material are as follows: (1) Prepare samples of different concentrations according to a concentration gradient and measure their absorbance. Use the interpolation method to construct the functional relationship y = f(x) between absorbance x and concentration y. (2) After the sample with an original concentration of m is left to stand for a certain period of time, its absorbance is tested and the current concentration m0 is calculated based on the functional relationship. At this time, the stability of the sample is n = m0 / m. The larger the n value, the higher the sample stability.

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