A composite photocatalytic material and its preparation method and application

Abstract

The present invention proposes a composite photocatalytic material and a preparation method and application thereof, belonging to the technical field of antibacterial materials; a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material is synthesized in situ, the material is a cluster heterojunction formed by a single-layer BiOBr (QDs) quantum dot with a 2D interface nuclear nebula structure and a single-layer spherical AgBr; wherein the single-layer quantum dot BiOBr (QDs) in the composite photocatalytic material exposes more edge positions while retaining the characteristics of the two-dimensional material, which leads to a stronger edge effect and exhibits more unique photoelectric characteristics than a single-layer nanosheet, thereby making the composite photocatalytic material prepared by the present invention have significant advantages in terms of photoelectric performance, catalytic performance, flexibility and modulatability; in addition, the preparation process of the present invention is carried out at room temperature and pressure, and has high applicability; and the raw materials used in the reaction have the advantages of low cost and environmental friendliness.

Description

Technical Field

[0001] The invention belongs to the technical field of antibacterial materials, and in particular relates to a composite photocatalytic material and a preparation method and application thereof. Background Art

[0002] Purification of organic pollutants, pathogenic microorganisms and other harmful substances in sewage has always been a thorny issue of concern. Traditional disinfection methods, including high-pressure sterilization and chlorine dioxide treatment, usually consume a lot of energy or inevitably produce harmful byproducts. Semiconductor-based photocatalytic reactions have great prospects in solving the above problems due to their effective use of solar energy and environmental friendliness, and have attracted the attention of researchers. At present, many photocatalysts react only under ultraviolet light, but ultraviolet light only accounts for a very small part of sunlight (less than 5%). In order to efficiently utilize solar energy and focus on indoor lighting in the visible-infrared range, it is urgent to develop efficient visible light-driven photocatalysts. The loading of silver halide on the semiconductor matrix has strong photoactivity. With the help of the carrier, the silver halide can maintain stability, which is conducive to the transfer of photoexcited carriers. Under light, AgX (X = Cl, Br, I) can be reduced to Ag nanoparticles, which show strong visible light absorption based on its localized surface plasmon resonance. BiOBr is an excellent visible-light-driven photocatalytic material. BiOBr (QDs) has abundant oxygen vacancies due to its small size, which improves the photocatalytic performance. However, the direct precipitation of AgX (X = Cl, Br, I) will lead to severe aggregation, poor dispersion, and hinder the interfacial charge transfer. Therefore, it is very important to develop a reasonable synthesis method. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a composite photocatalytic material and its preparation method and application. The composite photocatalytic material is a semiconductor material loaded with silver halide in a 2D / 2D heterojunction structure, which can effectively improve its photocatalytic activity. The small size of BiOBr (QDs) quantum dots is combined with the unique properties of the 2D / 2D heterojunction structure, which greatly improves the photocatalytic activity.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention:

[0006] A 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material, wherein the composite photocatalytic material is a cluster heterojunction formed by a single layer of BiOBr (QDs) with a 2D interface core nebula structure and a single layer of spherical AgBr;

[0007] The core nebula structure has a silver heterojunction as the core, and BiOBr (QDs) are distributed around it.

[0008] Beneficial effects: The 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material disclosed in the present invention is a clustered heterojunction formed by a single layer of BiOBr quantum dots with a 2D interface nuclear nebula structure and a single layer of spherical AgBr; wherein the single layer of quantum dots BiOBr (QDs) in the composite photocatalytic material exposes more edge positions while retaining the characteristics of two-dimensional materials, which leads to a stronger edge effect and exhibits more unique photoelectric properties than single-layer nanosheets, thereby making the composite photocatalytic material prepared by the present invention have significant advantages in photoelectric performance, catalytic performance, flexibility and modulatability.

[0009] Preferably, the silver heterojunction particle size is 9-12 nm, and the BiOBr (QDs) quantum dot particle size is 4-5 nm.

[0010] Preferably, the composite photocatalytic material is a single layer.

[0011] The second technical solution of the present invention:

[0012] The preparation method of the above 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material comprises the following steps:

[0013] At room temperature and pressure, silver was dispersed in a single layer of BiOBr using mannitol and polyvinyl pyrrolidone as dispersing solvents, and finally a 2D / 2D heterojunction AgBr / BiOBr(QDs)g composite photocatalytic material was prepared.

[0014] Beneficial effects: Under normal temperature and pressure conditions, the present invention uses mannitol and polyvinyl pyrrolidone as dispersing solvents to enable BiOBr to form a single-layer quantum dot structure with extremely high dispersibility, allowing AgBr to fully react with BiOBr to in situ synthesize a 2D / 2D heterojunction structure, thereby obtaining a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material.

[0015] Preferably, the mass ratio of mannitol to polyvinyl pyrrolidone is 0.91:0.4.

[0016] Preferably, the preparation method comprises the following steps:

[0017] The NaBr aqueous solution is added drop by drop into the dispersion solvent in which Bi(NO3)3·5H2O is dissolved, and the mixture is stirred for reaction. Then, AgNO3 is added, and the mixture is stirred for reaction again. The mixture is then centrifuged, washed, and dried to obtain the 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material.

[0018] Furthermore, the mass ratio of NaBr to silver nitrate in the NaBr aqueous solution is (2-3):1.

[0019] Further, the stirring reaction time is 0.5h;

[0020] The stirring reaction time is 12 hours.

[0021] The third technical solution of the present invention:

[0022] Such as the application of the above-mentioned 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material in the antibacterial field.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] 1. The in-situ synthesis of 2D / 2D heterojunction structure has significant advantages in terms of photoelectric performance, catalytic performance, flexibility and modulability, and the single-layer quantum dots expose more edge positions while retaining the characteristics of two-dimensional materials, which leads to a stronger edge effect and exhibits more unique photoelectric properties than single-layer nanosheets. Under light, the silver halide surface is partially reduced to nanosilver particles, which is an effective antibacterial agent with the dual functions of inducing visible light photocatalysis and promoting photoelectron-hole separation through the surface plasmon resonance (SPR) effect. In addition, silver halide can remain stable with the help of semiconductor carriers, which is conducive to the transfer of photoexcited charge carriers and avoids the photocorrosion of silver halide. The present invention uses a single-layer quantum dot BiOBr (QDs) to in-situ synthesize a 2D / 2D heterojunction structure to load silver halide on a semiconductor material, which can effectively improve its photocatalytic activity, and the small size of the BiOBr (QDs) quantum dots combined with the unique properties of silver nanoparticles greatly improves the photocatalytic activity. Therefore, the innovative structure of in-situ synthesis of heterojunctions using a single-layer quantum dot BiOBr (QDs) is proposed for the first time in China. It can be inferred that 2D / 2D heterojunction AgBr / BiOBr (QDs) semiconductor composites have great application potential in photocatalytic antibacterial properties.

[0025] 2. The preparation method of the 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalyst of the present invention is carried out under the simplest and most applicable conditions of normal temperature and pressure. The preparation method is simple, time-saving, low-cost and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1The XRD pattern of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention;

[0028] Figure 2 (a) is the HR-TEM image of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention; (b) is the HR-TEM image of the bulk morphology BiOBr-Ag prepared in Comparative Example 2; (c) is the diameter of the single-layer quantum dot BiOBr of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention; (d) is the diameter of the Ag heterojunction of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention;

[0029] Figure 3 This is a graph showing the antibacterial plate counts of Escherichia coli using the Ag nanoparticles / BiOBr(QDs) (i.e., 2D / 2D heterojunction AgBr / BiOBr(QDs), the same below) prepared in Example 1 and the BiOBr(QDs) prepared in Comparative Example 1 as photocatalysts;

[0030] Figure 4 This is a graph showing the antibacterial plate count of Escherichia coli using the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1, the BiOBr-Ag prepared in Comparative Example 2, the BiOBr NS1-Ag prepared in Comparative Example 3, and the BiOBr NS2-Ag prepared in Comparative Example 4 as photocatalysts with a 400 nm filter added;

[0031] Figure 5 This is a graph showing the antibacterial plate count of Escherichia coli using the Ag nanoparticles / BiOBr(QDs) prepared in Example 1 and the BiOBrNS1-Ag prepared in Comparative Example 3 as photocatalysts with a 400 nm filter added. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The primary purpose of the present invention is to provide a method for preparing a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material, comprising the following steps:

[0038] Dissolve Bi(NO3)3·5H2O in a solution prepared by mannitol and polyvinyl pyrrolidone to form solution A, dissolve NaBr in pure water to form solution B, and add solution B dropwise into solution A.

[0039] In some preferred embodiments, the preparation method of solution A is: firstly prepare a mixed solution of mannitol and polyvinyl pyrrolidone at a mass ratio of 0.91:0.4 as a dispersant, and then dissolve Bi(NO3)3·5H2O in the above dispersant. In a preferred embodiment, the concentration of Bi(NO3)3·5H2O in solution A is 19.4 g / L.

[0040] In some preferred embodiments, the B solution is prepared by dissolving NaBr in pure water to form the B solution. In a preferred embodiment, the concentration of NaBr in the B solution is 4.12 g / L.

[0041] In some preferred embodiments, the volume ratio of solution A to solution B is 1:1.

[0042] In some preferred embodiments, the method for preparing the antibacterial 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material specifically comprises the following steps:

[0043] S1. Add solution B dropwise into solution A, react for 30 min at room temperature with stirring, then add silver nitrate;

[0044] S2. The reaction was carried out at room temperature under stirring conditions for 12 hours, and the precipitate was centrifuged, washed and dried to obtain a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material.

[0045] The present invention also discloses a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material prepared by the above preparation method, a cluster heterojunction formed by a single layer of BiOBr (QDs) quantum dots in a 2D interface core nebula structure and a single layer of spherical AgBr. That is, the core nebula structure with the silver heterojunction as the core and BiOBr (QDs) quantum dots distributed around it, the microscopic morphology of the powder particles is a single layer, the size of the silver particles is 9-12nm, and the size of the BiOBr quantum dots is 4-5nm.

[0046] All raw materials used in the examples of the present invention are commercially available.

[0047] The "normal temperature" mentioned in the present invention is 25±2°C.

[0048] The technical solution of the present invention is further illustrated by the following embodiments.

[0049] Example 1

[0050] 1. Dissolve 0.97 g Bi(NO3)3·5H2O in 50 mL of a solution of mannitol and polyvinyl pyrrolidone in a mass ratio of 0.91:0.4 to form solution A; the molecular weight of polyvinyl pyrrolidone is 10000;

[0051] 2. Dissolve 0.206 g NaBr in 50 mL pure water to form solution B, and add solution B dropwise into solution A;

[0052] 3. After reacting at room temperature for 30 minutes with stirring, 0.0849 g of silver nitrate was added, and the reaction was stirred at room temperature for 12 hours; the precipitate was separated by centrifugation, and washed with ethanol and water for 3 times respectively, and then dried to obtain a 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material.

[0053] Comparative Example 1

[0054] The difference from Example 1 is that no silver nitrate is added in step 3, and BiOBr(QDs) is finally prepared. Other conditions are the same as in Example 1.

[0055] Comparative Example 2

[0056] The difference from Example 1 is that mannitol and polyvinyl pyrrolidone are not added in step 1, and BiOBr-Ag is finally prepared. Other conditions are the same as in Example 1.

[0057] Comparative Example 3

[0058] The difference from Example 1 is that no polyvinyl pyrrolidone is added in step 1, and BiOBrNS1-Ag is finally prepared. Other conditions are the same as in Example 1.

[0059] Comparative Example 4

[0060] The difference from Example 1 is that no mannitol is added in step 1, and finally BiOBr NS2-Ag is prepared. Other conditions are the same as in Example 1.

[0061] Figure 1 The XRD pattern of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention; Figure 1 The characteristic peaks of BiOBr were found to be basically consistent with those of BiOBr. The diffraction peaks were broad, indicating that the crystallinity of the sample was low, confirming the formation of small-sized BiOBr. There were also corresponding characteristic peaks of AgBr.

[0062] Figure 2 (a) is a HR-TEM image of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention; Figure 2 (b) is the HR-TEM image of the bulk morphology BiOBr-Ag prepared in Comparative Example 2; Figure 2 (c) is the diameter of the single-layer quantum dots BiOBr (QDs) of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention; Figure 2 (d) The diameter of the Ag heterojunction of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1 of the present invention. Figure 2 From the TEM images (a) and (b), it can be clearly seen that the morphology of BiOBr without polyvinyl pyrrolidone and mannitol is blocky and highly crystalline, while the morphology of Ag nanoparticles / BiOBr (QDs) is a single layer of quantum dots, and the catalyst at the edge is more dispersed and has a very low crystallinity. Figure 2 From (c) and (d), we can see that the particle size of the silver heterojunction is 9-12nm, and the particle size of the BiOBr (QDs) quantum dots is 4-5nm.

[0063] Effect verification

[0064] Effect Example 1

[0065] 0.05 g of the Ag nanoparticles / BiOBr(QDs) prepared in Example 1 and the BiOBr(QDs) prepared in Comparative Example 1 were mixed with 50 mL of 1×10 8 coli solution, and under stirring, turn on the xenon lamp, take 0.1 mL of the reaction solution every 10 min, dilute it 1000 times, and then inoculate it on a sterile culture dish, and place it in a 37°C constant temperature bacterial incubator for 1 hour.

[0066] Figure 3 The plate counts when using Ag nanoparticles / BiOBr(QDs) and BiOBr(QDs) as photocatalysts are shown. Figure 3 It can be seen that under the action of 2D / 2D heterojunction AgBr / BiOBr (QDs) composite materials, the relative bacterial survival rate of E. coli solution decreases with the increase of irradiation time. Compared with BiOBr (QDs) (the lowest relative bacterial survival rate of 71.26% at 30min), it has stronger photocatalytic activity. This shows that the photocatalytic antibacterial ability of 2D / 2D heterojunction AgBr / BiOBr (QDs) composite semiconductor materials is stronger than that of pure BiOBr (QDs) quantum dots.

[0067] Effect Example 2

[0068] (i) In order to verify the photocatalytic ability in the visible light region, a xenon lamp was equipped with a 400 nm filter. 0.05 g of the 2D / 2D heterojunction AgBr / BiOBr (QDs) prepared in Example 1, the BiOBr-Ag prepared in Comparative Example 2, the BiOBr NS1-Ag prepared in Comparative Example 3, and the BiOBr NS2-Ag prepared in Comparative Example 4 were mixed with 50 mL of 1×10 8 coli solution, and under stirring, turn on the xenon lamp, take 0.1 mL of the reaction solution every 10 min, dilute it 1000 times, and then inoculate it on a sterile culture dish, and place it in a 37°C constant temperature bacterial incubator for 1 hour.

[0069] Figure 4The antibacterial tests were performed on 2D / 2D heterojunction AgBr / BiOBr(QDs), BiOBr-Ag, BiOBr NS1-Ag and BiOBr NS2-Ag photocatalysts. In this experiment, the bactericidal properties of photocatalyst materials with different morphologies formed by different synthesis routes were evaluated while further modifying the spectral range. According to the analysis of the experimental data, it was found that the antibacterial properties of 2D / 2D heterojunction AgBr / BiOBr(QDs) and BiOBr NS1-Ag were significantly better than those of the other two. This shows that the reduction of the catalyst particle diameter has an important influence on the improvement of the photocatalytic efficiency.

[0070] (ii) After adding photocatalyst in advance and irradiating with full spectrum for 1 hour, the antibacterial experiment was carried out on 2D / 2D heterojunction AgBr / BiOBr (QDs) and BiOBr NS1-Ag using 400nm filter again. Figure 5 It can be seen that the antibacterial performance is significantly reduced compared with the direct antibacterial experiment, which indicates that under light irradiation, Ag is reduced and together with the catalyst enhances the photocatalytic efficiency.

[0071] In summary, there is no related research on the in-situ synthesis of heterojunctions using single-layer quantum dots BiOBr. The present invention conducts comparative experiments through BiOBr with different morphologies, and concludes that the 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material has better bactericidal performance. That is, the above experiment proves that the 2D / 2D heterojunction AgBr / BiOBr (QDs) composite photocatalytic material can significantly improve the photocatalytic performance of BiOBr (QDs) by forming a heterojunction structure, and successfully prepares a highly active visible light AgBr / BiOBr (QDs) composite photocatalytic material. The photocatalytic activity of AgBr / BiOBr (QDs) is highly dependent on the abundant oxygen vacancies in its single-layer structure and the in-situ synthesized 2D / 2D heterojunction.

[0072] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material, characterized in that: The composite photocatalytic material is a clustered heterojunction formed by a single layer of BiOBr quantum dots and a single layer of spherical AgBr in a 2D interface core nebula structure; The core nebula structure is based on a silver heterojunction with BiOBr quantum dots distributed around it; The preparation method of the 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material comprises the following steps: At room temperature and pressure, mannitol and polyvinyl pyrrolidone were used as dispersing solvents to disperse silver ions in a single layer of BiOBr, and finally a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material was prepared.

2. The 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 1, characterized in that: The particle size of the silver heterojunction is 9-12 nm, and the particle size of the BiOBr quantum dots is 4-5 nm.

3. The 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 1, characterized in that: The composite photocatalytic material is a single layer.

4. A method for preparing a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material, characterized in that: The following steps are involved: At room temperature and pressure, mannitol and polyvinyl pyrrolidone are used as dispersing solvents to disperse silver ions in a single-layer BiOBr quantum dot solution, and the solution is stirred for reaction to obtain the 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to any one of claims 1 to 3.

5. The method for preparing a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 4, characterized in that: The mass ratio of mannitol to polyvinyl pyrrolidone is 0.91:0.

4.

6. The method for preparing a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 4 or 5, characterized in that: The preparation method comprises the following steps: The NaBr aqueous solution is added drop by drop into the dispersion solvent in which Bi(NO3)3·5H2O is dissolved, and the mixture is reacted while stirring. Then, AgNO3 is added, and the mixture is stirred and reacted again. The mixture is centrifuged, washed, and dried to obtain the 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material.

7. The method for preparing a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 6, characterized in that: The mass ratio of NaBr to silver nitrate in the NaBr aqueous solution is (2-3):

1.

8. The method for preparing a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material according to claim 6, characterized in that: The stirring reaction time is 0.5h; The stirring reaction time is 12 hours.

9. Application of a 2D / 2D heterojunction AgBr / BiOBr quantum dot composite photocatalytic material as claimed in any one of claims 1 to 3 in the field of antibacterial materials.

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