Preparation method of silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst

Abstract

The application discloses a preparation method of a silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst, which comprises the following steps: dissolving ferrous salt and manganese salt in an ethylene glycol solution, and preparing a sheet precursor through a hydrothermal reaction under the assistance of sodium acetate; and dispersing the precursor in a silver nitrate solution to perform a photo-thermal reaction, so that active oxygen generated by the photo-decomposition of the silver nitrate oxidizes the precursor into manganese ferrite, and silver atoms generated simultaneously adhere to the manganese ferrite nanosheet to form high-catalytic-activity quantum dots. In the process, the etching effect of light can control the thickness and size of the precursor sheet layer, so that the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst is obtained. The preparation process has a short reaction period, can realize photo-decomposition, photo-etching and in-situ quantum dot modification simultaneously in the photo-thermal reaction, and has the advantages of high dispersibility, excellent photocatalytic performance and convenience in carrying out a photocatalytic reaction in a solution.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis, and in particular to a method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst. Background Art

[0002] As a new inorganic catalyst, silver (Ag) quantum dots (QDs) offer numerous advantages in photocatalysis, including high efficiency, durability, pH-independent performance, safety, and environmental friendliness. The combination of Ag QDs with other materials in photocatalysts can further leverage their localized surface plasmon resonance (SPR) effect and their low Fermi level. The SPR effect increases the catalyst's photoresponse range and charge separation efficiency, enhancing catalytic performance in the visible light range. The lower Fermi level facilitates electron transfer, accelerating the reaction rate.

[0003] Manganese ferrite (MnFe2O4) magnetic nanomaterials, with their low Curie temperature, moderate saturation magnetization, and high chemical stability, are important spinel ferrite soft magnetic materials with applications in a wide range of fields, including electrochemical sensors, magnetic resonance imaging, tumor hyperthermia, microwave absorption, heavy metal sensors, and photocatalysis. Their magnetic separability makes them particularly advantageous for the catalytic degradation of pollutants in water. Numerous methods exist for preparing MnFe2O4 magnetic nanomaterials, including pyrolysis, hydrothermal, sonication, coprecipitation, and reverse micelle methods. These nanomaterials exhibit a variety of morphologies, including spheres, cubes, and octahedrons. However, as photocatalysts, MnFe2O4's intrinsic catalytic performance is not particularly good, and different morphologies can also affect its performance, primarily due to its specific surface area, catalyst particle size, and dispersibility in solution. Therefore, compounding with highly active materials is an effective approach to enhance the catalytic performance of MnFe2O4. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst, which adopts a photothermal reaction method with simple process, mild conditions and short production cycle. The prepared photocatalyst has high dispersibility, strong catalytic activity and is easy to recycle.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst comprises the following steps:

[0007] Step 1: Dissolve MnCl2 and FeSO4 in HOCH2CH2OH at a mass ratio of 1:2, then add CH3COONa to the solution in proportion, the mass ratio of CH3COONa to HOCH2CH2OH is 1:10-20, and stir thoroughly until completely dissolved;

[0008] Step 2: Take 15-25 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 24-36 hours under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in an alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for use.

[0009] Step 3, weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it into 20 mL of a 0.01-0.05 mol / L AgNO3 solution, ultrasonicate it at 60-80°C for 30 min, transfer the solution to a 50 mL photochemical reaction tube, and irradiate it with a xenon lamp light source for 30-60 min. AgNO3 decomposes into silver quantum dots under photothermal conditions, and the released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder in one step; collect the generated powder using a magnet, repeatedly wash it with anhydrous ethanol and deionized water, and dry it at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst;

[0010] After testing, the photocatalyst layer prepared in step three has a thickness of 8-20 nm and an absorption wavelength of 410-690 nm. It can be quickly dispersed in water without mechanical stirring or ultrasonic dispersion, and the degradation rate of methylene blue within 60 minutes is 75.2-92.8%.

[0011] Preferably, in step 1, the mass ratio of MnCl2 to HOCH2CH2OH is 1:100-150.

[0012] Preferably, the power of the xenon lamp in step 3 is 500-1000w.

[0013] The reaction equation for preparing the precursor MnFe2(OH)6 in step 2 is:

[0014]

[0015] In step 3, silver nitrate decomposes into silver quantum dots and oxygen under light. The reaction equation is as follows:

[0016]

[0017] The released highly active O2 will immediately participate in the oxidation of the MnFe2(OH)6 matrix, and the reaction equation is:

[0018]

[0019] Under light and heat radiation, the synergistic effect of equations (2) and (3) promotes the reaction to proceed according to equation (4):

[0020]

[0021] The synchronous silver quantum dot modification and crystal conversion reaction under the synergistic effect of light and heat in the present invention is beneficial to controlling the thickness and size of the MnFe2O4 layer to prevent the layer from being too thick or too large.

[0022] After the reaction is completed, the generated silver quantum dots modified ultrathin manganese ferrite nanosheet photocatalyst black powder is collected by magnetic separation.

[0023] In the present invention, manganese ferrite is first regulated to a lamellar structure, which helps to give the nanoparticles a larger specific surface area and better dispersibility. More importantly, the two-dimensional nanosheets also have a short vertical migration distance for carriers from the interior to the surface, accelerating electron transport along the plane, reducing carrier losses at material boundaries or interfaces, and providing more abundant reaction sites. Based on this, silver quantum dots are then in situ composited with ultrathin nanosheets. This combines the properties of silver quantum dots that increase the catalyst's light response range and accelerate reaction rates with the advantages of manganese ferrite, resulting in a nanocatalyst with stronger photocatalytic activity.

[0024] The advantages of the present invention are:

[0025] The alkaline environment is provided by the hydrolysis of sodium acetate. This process is slow and stable, and the morphology of the generated precursor MnFe2(OH)6 can be controlled to be uniform. The size of the layer can also be controlled according to the concentration of sodium acetate and the reaction time.

[0026] The decomposition of silver nitrate under light conditions produces highly reactive oxygen species that help oxidize the precursor at a relatively low temperature, yielding manganese ferrite crystals. Simultaneously, silver atoms are in situ deposited on the manganese ferrite nanosheets, resulting in a highly catalytically active silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst.

[0027] The silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst prepared by this invention combines the excellent ability of silver quantum dots to enhance the light response range and accelerate electron transfer. On the ultrathin manganese ferrite nanosheet, the vertical migration distance of charge carriers from the interior to the surface is short, and electron transport along the plane effectively reduces carrier loss at material boundaries or interfaces, providing more reaction sites. Furthermore, the excellent magnetic responsiveness of manganese ferrite facilitates the recycling of the photocatalyst using an external magnetic field after the catalytic reaction is completed.

[0028] The method of the invention has low raw material cost and simple synthesis process, and is convenient for batch synthesis and popularization and application of the high-performance catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the XRD pattern of the silver quantum dot modified manganese ferrite ultrathin nanosheets prepared in the present invention;

[0030] Figure 2 This is a VSM test analysis chart of the silver quantum dot-modified manganese ferrite ultrathin nanosheets prepared by the present invention;

[0031] Figure 3 This is a SEM image of the MnFe2(OH)6 precursor and silver quantum dot-modified manganese ferrite ultrathin nanosheets prepared by the present invention;

[0032] Figure 4 This is a UV-Vis DRS image of the silver quantum dot-modified manganese ferrite ultrathin nanosheet prepared by the present invention;

[0033] Figure 5 This is an AFM image of the silver quantum dot-modified manganese ferrite ultrathin nanosheets prepared by the present invention;

[0034] Figure 6 The invention provides a comparison of the performance of photocatalytic degradation of dyes by manganese ferrite nanosheets, silver nanoparticle / manganese ferrite composite nanosheets, and the silver quantum dot-modified manganese ferrite ultrathin nanosheets of the present invention. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to specific examples and verification of the products of the examples.

[0036] Example 1

[0037] A method for preparing a silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst comprises the following steps:

[0038] Step 1: Dissolve 0.098g MnCl2 and 0.196g FeSO4 in 30mL HOCH2CH2OH, then add 1.5g CH3COONa to the solution in proportion and stir thoroughly until completely dissolved;

[0039] Step 2: Take 25 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 24 h under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in an alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for use.

[0040] Step 3. Weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it in 20 mL of 0.01 mol / L AgNO3 solution, ultrasonicate it at 80°C for 30 min, transfer the solution to a 50 mL photochemical reaction tube, and irradiate it with a 1000W xenon lamp light source for 60 min. AgNO3 decomposes into silver quantum dots under photothermal conditions, and the released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder in one step; collect the generated powder using a magnet, wash it repeatedly with anhydrous ethanol and deionized water, and dry it at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst.

[0041] After testing, the average thickness of the prepared silver quantum dot-modified ultrathin manganese ferrite nanosheets was 9 nm, the sample absorption spectrum range was 410-690 nm, and the degradation rate of methylene blue in 60 min was 92.8%.

[0042] Example 2

[0043] A method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst comprises the following steps:

[0044] Step 1: Dissolve 0.098g MnCl2 and 0.196g FeSO4 in 40mL HOCH2CH2OH, then add 3.4g CH3COONa to the solution and stir thoroughly until completely dissolved;

[0045] Step 2: Take 15 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 36 hours under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in the alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for use.

[0046] Step 3. Weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it into 20 mL of 0.05 mol / L AgNO3 solution, ultrasonicate it at 60°C for 30 min, transfer the solution to a 50 mL photochemical reaction tube, and irradiate it with an 800W xenon lamp light source for 30-60 min. AgNO3 decomposes into silver quantum dots under photothermal conditions, and the released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder in one step; collect the generated powder using a magnet, wash it repeatedly with anhydrous ethanol and deionized water, and dry it at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst.

[0047] After testing, the average thickness of the prepared silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst was 12 nm, the sample absorption spectrum range was 430-670 nm, and the degradation rate of methylene blue in 60 min was 75.2%.

[0048] Example 3

[0049] A method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst comprises the following steps:

[0050] Step 1: Dissolve 0.098g MnCl2 and 0.196g FeSO4 in 30mL HOCH2CH2OH, then add 1.8g CH3COONa to the solution and stir thoroughly until completely dissolved;

[0051] Step 2: Take 20 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 30 hours under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in the alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for use.

[0052] Step 3. Weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it in 20 mL of 0.03 mol / L AgNO3 solution, ultrasonicate it at 70°C for 30 min, transfer the solution to a 50 mL photochemical reaction tube, and irradiate it with an 800W xenon lamp light source for 40 min. AgNO3 decomposes into silver quantum dots under photothermal conditions, and the released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder in one step; collect the generated powder using a magnet, wash it repeatedly with anhydrous ethanol and deionized water, and dry it at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst.

[0053] After testing, the average thickness of the prepared silver quantum dot-modified ultrathin manganese ferrite nanosheet tube catalyst was 13 nm, the sample absorption spectrum range was 435-650 nm, and the degradation rate of methylene blue in 60 min was 81.5%.

[0054] Example 4

[0055] A method for preparing a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst comprises the following steps:

[0056] Step 1: Dissolve 0.098g MnCl2 and 0.196g FeSO4 in 20mL HOCH2CH2OH and 1.5g CH3COONa, and stir thoroughly until completely dissolved;

[0057] Step 2: Take 22 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 28 hours under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in the alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for use.

[0058] Step 3. Weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it into 20 mL of 0.03 mol / L AgNO3 solution, ultrasonicate it at 75°C for 30 min, transfer the solution to a 50 mL photochemical reaction tube, and irradiate it with a 500W xenon lamp light source for 50 min. AgNO3 decomposes into silver quantum dots under photothermal conditions, and the released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder in one step; collect the generated powder using a magnet, wash it repeatedly with anhydrous ethanol and deionized water, and dry it at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst.

[0059] After testing, the average thickness of the prepared silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst was 15 nm, the sample absorption spectrum range was 450-630 nm, and the degradation rate of methylene blue in 60 min was 79.3%.

[0060] The silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst prepared in Example 1 was used as a sample, and the structure of the sample was analyzed and described by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), ultraviolet-visible diffuse reflectance (UV-Vis DRS), and atomic force microscopy (AFM).

[0061] 1. XRD analysis

[0062] Figure 1As shown, the X-ray diffraction (XRD) patterns of the MnFe2(OH)6 precursor, the pure MnFe2O4 sample obtained by direct illumination, no silver nitrate was added to the solution, and the silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst (Ag(QDs) / MnFe2O4) prepared according to the present invention are respectively. It can be seen that before the photothermal reaction, the precursor has an amorphous structure, and the spectrum is all miscellaneous peaks without crystal characteristic peaks. Similarly, when the precursor is subjected to a photothermal conversion reaction without the addition of silver nitrate, the obtained pure MnFe2O4 sample also has only a few crystal characteristic peaks. This shows that although a semiconductor manganese ferrite with a cubic spinel structure is formed, due to the lack of oxygen generated by the photodecomposition of silver nitrate, the MnFe2(OH)6 precursor is not fully oxidized to obtain the final product. In contrast, the XRD spectrum of Ag(QDs) / MnFe2O4 shows a clear spinel structure. This indicates that the formation process of the crystal involves both the photodecomposition of silver nitrate and the photothermal conversion of the precursor, proving that the release of highly reactive oxygen species under light irradiation by silver nitrate participates in the oxidation process of MnFe2(OH)6. The purity of the crystal is high, and the characteristic diffraction peaks of manganese ferrite are observed at 2θ=18.6°(111), 29.3°(202), 36.3°(222), 42.9°(400), 56.0°(333) and 61.5°(440), and there are almost no obvious impurity peaks in the crystal. The characteristic peaks of crystalline silver cannot be observed in the XRD spectrum, partly because the silver content is low, but more importantly, it indicates that the silver in the sample is not precipitated in the form of a single substance or crystal, but exists in the form of quantum dots in the manganese ferrite lattice.

[0063] 2. VSM analysis

[0064] Figure 2 This is the vibrating sample magnetometer (VSM) test curve of the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst, which shows the magnetic response characteristics of the sample. It can be seen that the magnetization curve is a typical S-shape under an external magnetic field, indicating that they are superparamagnetic materials, which is consistent with their ultrathin nanosheet structure. The silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst exhibits a clear symmetrical hysteresis loop, and its saturation magnetization value is about 49.6emu / g. When the sample is evenly dispersed in an aqueous solution and the formed uniform dispersion is placed on the side of a magnet, it is found that the material in the suspension will be oriented under the external magnetic field, and after about 1 minute, the sample will be completely adsorbed on one side of the magnet. This result shows that the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst has good magnetic response performance and can be smoothly extracted and separated under the action of an external magnetic field, which is conducive to the recovery and reuse of the catalyst through the magnetic field after the photocatalytic reaction is completed.

[0065] 3. SEM analysis

[0066] Figure 3 It is an SEM photo of the MnFe2(OH)6 precursor and the silver quantum dot modified ultra-thin manganese ferrite nanosheet photocatalyst. It can be seen that the prepared MnFe2(OH)6 precursor sample has a lamellar structure with a smooth surface and a middle part slightly thicker than the edge. When it is modified with silver quantum dots under photothermal conditions, the lamellar layer becomes significantly thinner, but the surface of the nanosheet finally prepared is still very smooth. The thinnest silver quantum dot modified ultra-thin manganese ferrite nanosheet photocatalyst prepared by the present invention is about 8 nanometers, and the ideal average thickness does not exceed 20 nanometers. Because no obvious silver particles can be seen, this shows that the silver is not quickly reduced to particles, but exists in the manganese ferrite crystals in the form of quantum dots, which is beneficial to the improvement of catalyst performance.

[0067] 4. UV-Vis DRS analysis

[0068] Figure 4 The UV-visible diffuse reflectance spectra of manganese ferrite and silver quantum dots show significant light absorption in the 400-700nm range. Within this range, the absorbance of all samples increases dramatically, indicating that the prepared samples have a good response to visible light, which is conducive to the application of this catalyst in daily production and living environments. Due to the presence of silver quantum dots, the composite nanosheets produce a local surface plasmon resonance effect. Therefore, compared with pure manganese ferrite, the introduction of silver quantum dots not only significantly extends the absorption edge of the sample, but also significantly enhances the absorption intensity, significantly improving the photocatalytic performance.

[0069] 5. AFM analysis

[0070] Figure 5 This is an atomic force microscopy image of a sample of the silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst prepared by the present invention. The test results show that the resulting silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst is approximately 10 nanometers thick, and the overall sheet thickness is relatively uniform, which may be related to the photolithography process under a photothermal environment. This ultrathin and uniform sheet structure has a larger specific surface area than spherical particles, which greatly facilitates its full dispersion in the solution and large-area contact with the organic matter to be degraded. It allows the photogenerated carriers generated under illumination conditions to be transferred to the organic matter, thereby achieving oxidative degradation of the pollutants.

[0071] 6. Performance test of photocatalytic degradation of dyes

[0072] Methylene blue (10 mg / L) was selected for the photocatalytic degradation experiment to visually test the photocatalytic degradation performance of the samples. 20 mg of three different samples were added to 50 mL of methylene blue solution. After reaching adsorption equilibrium in a dark environment, the solution was irradiated with a xenon lamp.

[0073] The control sample 1 is a manganese ferrite nanosheet, which is prepared by the method that the precursor is irradiated without adding silver nitrate and other conditions are completely same as the preparation method of the application (MnFe2O4); the sample 2 is a silver nanoparticle modified manganese ferrite nanosheet Ag (NPs) / MnFe2O4, which is prepared by the method that the manganese ferrite nanosheet is prepared first, and then is dispersed in a silver nitrate solution to be irradiated and reduced, so that the silver nanoparticles with a larger particle size are deposited on the manganese ferrite nanosheet; the sample 3 is a silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst Ag (QDs) / MnFe2O4 prepared by the application, and the silver quantum dots are obtained by the silver nitrate photodecomposition, and the active oxygen generated is used for the oxidation of the precursor and the formation process of the manganese ferrite ultrathin nanosheet crystal at the same time.

[0074] The experimental results are shown in Table 1. Figure 6 As shown in Table 1, the content of methylene blue of the samples all decreases to different degrees after the xenon lamp irradiation for 10 min. It can be seen that the photocatalytic performance of the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst sample is the most obvious, because under the synergistic effect of the silver quantum dots and the manganese ferrite, the high oxidation active radicals ·O 2- and ·OH - can be generated in the catalyst, and these high oxidation active radicals accelerate the degradation of methylene blue. Although the manganese ferrite nanosheet has a relatively narrow energy gap and can effectively utilize visible light, the pure manganese ferrite as a photocatalyst has the weakest performance, because it is not conducive to the rapid separation of photo-generated carriers and the synergistic effect between the materials. Therefore, compared with the pure manganese ferrite, the manganese ferrite nanosheet after being compounded with the silver nanoparticles will produce SPR effect due to the silver nanoparticles, so that the photocatalytic performance can be improved to a certain extent. After the light irradiation for 60 min, the degradation rates of methylene blue of the pure manganese ferrite, the manganese ferrite compounded with the silver nanoparticles and the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst sample are 34.6%, 75.1% and 92.8% respectively. It can be seen that the catalytic performance of the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst prepared by the application is the highest. On the one hand, it is related to the high dispersibility of the ultrathin sheet structure in the solution, and more importantly, the ultrathin sheet layer is conducive to promoting the efficient transmission of photo-generated carriers under the synergistic effect of the silver quantum dots, so that stronger photocatalytic activity is generated.

Claims

1. A method for preparing silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst, characterized by: The following steps are involved: Step 1: Dissolve MnCl2 and FeSO4 in HOCH2CH2OH at a mass ratio of 1:2, and the mass ratio of MnCl2 to HOCH2CH2OH is 1:100-150; then add CH3COONa to the solution in proportion, the mass ratio of CH3COONa to HOCH2CH2OH is 1:10-20, and stir thoroughly until completely dissolved; Step 2: Take 15-25 mL of the solution prepared in step 1 and add it to a 50 mL reactor. React at 200 ° C for 24-36 hours under nitrogen protection to obtain a lamellar precursor MnFe2 (OH) 6 in the alkaline environment generated by the hydrolysis of CH3COONa. Wash the prepared precursor MnFe2 (OH) 6 with distilled water and ethanol several times, and then vacuum dry it at 25 ° C for later use. Step 3, weigh 10 mg of the precursor MnFe2(OH)6 powder prepared in step 2, disperse it into 20 mL of a 0.01-0.05 mol / L AgNO3 solution, ultrasonicate it at 60-80°C for 30 min, and then transfer the solution to a 50 mL photochemical reaction tube. Irradiate it with a xenon lamp light source for 30-60 min. AgNO3 decomposes into silver quantum dots under photothermal conditions. The released highly active O2 participates in the oxidation of the precursor MnFe2(OH)6 matrix, and a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst black powder is obtained in one step. The generated powder is collected by a magnet, repeatedly washed with anhydrous ethanol and deionized water, and dried at 60°C for 24 h to obtain a silver quantum dot-modified ultrathin manganese ferrite nanosheet photocatalyst. After testing, the photocatalyst layer prepared in step three has a thickness of 8-20 nm and an absorption wavelength of 410-690 nm. It can be quickly dispersed in water without mechanical stirring or ultrasonic dispersion, and the degradation rate of methylene blue within 60 minutes is 75.2-92.8%.

2. The method for preparing the silver quantum dot modified ultrathin manganese ferrite nanosheet photocatalyst according to claim 1, characterized in that: The power of the xenon lamp in step 3 is 500-1000W.

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