G-C3N4atZn / Eu-MOF composite dual-energy light conversion agent and preparation method thereof, dual-energy light conversion film and preparation method thereof

Abstract

The invention discloses a g-C3N4 (at) Zn / Eu-MOF composite dual-energy light conversion agent and a preparation method thereof, and a dual-energy light conversion film and a preparation method thereof. The preparation method comprises the following steps: firstly, preparing g-C3N4 by high-temperature calcination of melamine; secondly, preparing Zn / Eu-MOF through a hydrothermal reaction of europium nitrate, zinc nitrate, trimesic acid and DMF; and finally, dissolving g-C3N4 in ethanol, carrying out ultrasonic treatment, adding Zn / Eu-MOF, and stirring for a certain time to obtain the g-C3N4-Zn / Eu-MOF composite dual-energy light conversion agent. And adding the g-C3N4atZn / Eu-MOF composite dual-energy light conversion agent into a homogeneous aqueous solution of PVA, uniformly stirring, and drying at 40 DEG C to obtain the PVA-based dual-energy light conversion film. The g-C3N4 and Zn / Eu-MOF are combined to obtain the blue light and red light dual-energy composite light conversion material, the light absorption range is widened, and the light absorption performance is improved, so that ultraviolet light is effectively absorbed, efficient conversion of short-wave light is achieved, the light energy utilization efficiency is remarkably improved, meanwhile, the light stability is enhanced, the durability of a PVA-based dual-energy light conversion film in the agricultural environment is enhanced, and the application prospect is wide. And the development of sustainable agriculture can be promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and specifically relates to a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent and a preparation method thereof, a dual-energy light conversion film and a preparation method thereof. Background Art

[0002] The efficiency of light energy utilization is crucial to improving crop yield and quality. The photosynthesis process is the main way for plants to obtain energy. Due to the characteristics of the solar spectrum, the photosynthesis efficiency of plants at different wavelengths varies. Generally, plants have a higher absorption efficiency for visible light (especially red and blue light), while the absorption efficiency for ultraviolet light and far-red light is relatively low. Therefore, using spectrum conversion technology to convert short-wave light into long-wave light that can be used by plants is an important technical means to improve photosynthetic efficiency.

[0003] At present, common dual-energy light conversion agents are mainly divided into organic light conversion agents and inorganic light conversion agents. Although the existing dual-energy light conversion agents can effectively convert light energy to a certain extent, they still have some significant defects and shortcomings. First, the existing organic light conversion agents generally have the problems of poor thermal stability and low light stability. Under light and high temperature environment, some organic materials are easily degraded, resulting in reduced light conversion efficiency, thereby affecting their application effect in agricultural films. In addition, the synthesis process of organic materials is complicated and the cost is high, which limits their large-scale application to a certain extent. Secondly, although inorganic light conversion agents have good thermal stability and light stability, their synthesis process usually involves complex processes such as high-temperature sintering, which leads to a significant increase in production costs. Moreover, the light absorption range of some inorganic light conversion agents is narrow, and they cannot make full use of the solar spectrum, which limits their application in the agricultural field. For agricultural films prepared with light conversion agents, traditional light conversion films have relatively poor performance in terms of light transmittance and weather resistance. Most light conversion films are prone to yellowing and brittleness under long-term sunlight exposure, which not only affects the light transmittance of the film, but may also cause premature failure of the film material. For agricultural films, insufficient weather resistance means that under environmental conditions such as high temperature and ultraviolet rays, their functions will be greatly reduced, thereby affecting the growth of crops. Summary of the invention

[0004] In view of the problems existing in the above-mentioned background technology, the purpose of the present invention is to provide a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent and its preparation method, a dual-energy light conversion film and its preparation method, so as to broaden the absorption range of light, improve the light absorption performance, realize the efficient conversion of short-wave light, and enhance the photostability of the dual-energy light conversion agent.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent comprises the following steps:

[0007] S1, calcining melamine at high temperature to obtain g-C3N4;

[0008] S2, adding europium nitrate, zinc nitrate and trimesic acid to an aqueous solvent containing N,N-dimethylformamide (DMF), performing a hydrothermal reaction after ultrasonication to obtain a reaction product, and the reaction product is centrifuged, washed and vacuum dried in sequence to obtain Zn / Eu-MOF (zinc / europium metal organic framework);

[0009] S3. Dissolve the g-C3N4 in ethanol and add Zn / Eu-MOF after ultrasonic treatment, and stir for a certain period of time to obtain the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent.

[0010] The structure and properties of g-C3N4 are similar to those of graphene, and it has excellent chemical stability, optical properties, and mechanical properties; the zinc / europium metal organic framework (Zn / Eu-MOF) has a strong fluorescence emission capability and can effectively convert ultraviolet light into visible light (such as red light). By combining g-C3N4 with Zn / Eu-MOF, a dual-energy composite light conversion material of blue and red light is obtained.

[0011] Furthermore, in S1, the high temperature calcination conditions are: in an air atmosphere, heating from room temperature to 550°C at a heating rate of 5°C / min, keeping at 550°C for 4 hours, and then naturally cooling to room temperature.

[0012] Furthermore, in S2, the molar ratio of europium nitrate, zinc nitrate and trimesic acid is 1:0.2:1.

[0013] Furthermore, in S2, the volume ratio of N,N-dimethylformamide to water in the aqueous solvent is 1:6.

[0014] Furthermore, in S2, the hydrothermal conditions are: heating at 170-190°C for 8-12h.

[0015] Furthermore, the mass ratio of g-C3N4 to Zn / Eu-MOF is (3-4):(2-3), and the composite dual-energy light conversion agent obtained within this mass ratio range has excellent light conversion efficiency.

[0016] The present invention further provides a method for preparing a dual-energy light conversion film, wherein polyvinyl alcohol (PVA) is heated and dissolved in water to form a homogeneous solution, and then the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent is added, stirred evenly, and dried at 40°C to obtain a PVA-based dual-energy light conversion film.

[0017] The light conversion film can block and absorb ultraviolet light and convert it into an emission spectrum that matches the absorption of plants in the blue and red light regions, thereby improving plant photosynthesis, accelerating the germination of plant seeds, and thus increasing crop yields.

[0018] Furthermore, the preparation conditions of the homogeneous solution are: adding polyvinyl alcohol (PVA) into water and heating it to 100-120° C. and maintaining it for 1-2 hours.

[0019] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0020] (1) The structure and properties of g-C3N4 are similar to those of graphene, and it has excellent chemical stability, optical properties, and mechanical properties; the zinc / europium metal organic framework (Zn / Eu-MOF) has strong fluorescence emission ability and can effectively convert ultraviolet light into visible light (such as red light). By combining g-C3N4 with Zn / Eu-MOF, a blue light and red light dual-energy composite light conversion material is obtained, which broadens the light absorption range and improves the light absorption performance, thereby effectively absorbing ultraviolet light and realizing efficient conversion of short-wave light. In addition, the combination of g-C3N4 and Zn / Eu-MOF further enhances the photostability of the composite material, enabling it to maintain efficient light conversion ability under long-term illumination. The high carrier mobility of g-C3N4 combined with the luminescence characteristics of Zn / Eu-MOF promotes more efficient utilization of light energy.

[0021] (2) The PVA base film has good adhesion with the light conversion agent, ensuring the uniform distribution of the light conversion agent in the film, thereby improving the light conversion efficiency. The g-C3N4@Zn / Eu-MOF composite material is evenly loaded onto the PVA base film, which can significantly improve the efficiency of light energy utilization and enhance the durability of the film in the agricultural environment, allowing it to be used for a long time under various climatic conditions.

[0022] (3) The dual-energy light conversion film of the present invention can block and absorb ultraviolet light and convert it into an emission spectrum that matches the absorption of plants in the blue and red light regions, thereby improving plant photosynthesis, thereby accelerating the germination of plant seeds and increasing crop yields. The PVA-based g-C3N4@Zn / Eu-MOF light conversion film significantly improves the efficiency of light energy utilization while enhancing light stability, maintaining environmentally friendly properties, and helping to promote the development of sustainable agriculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the XRD pattern of the product provided in Example 1 of the present invention;

[0024] Figure 2 is the Fourier infrared spectrum of the product provided in Example 1 of the present invention;

[0025] Figure 3is the fluorescence emission spectrum of Zn / Eu-MOF provided in Example 1 of the present invention at different excitation wavelengths;

[0026] Figure 4 is the fluorescence emission spectrum of g-C3N4@Zn / Eu-MOF provided in Example 1 of the present invention at different excitation wavelengths;

[0027] Figure 5 This is the emission spectrum of the light yellow powdered light conversion agent provided in Comparative Example 1 of the present invention at different excitation wavelengths;

[0028] Figure 6 It is the emission spectrum of the milky white powder light conversion agent provided in Comparative Example 2 of the present invention at different excitation wavelengths;

[0029] Figure 7 It is the fluorescence excitation spectrum of g-C3N4@Zn / Eu-MOF provided in Example 1 of the present invention at different emission wavelengths;

[0030] Figure 8 is the ultraviolet absorption spectrum of the product provided in Example 1 of the present invention;

[0031] Fig. 9 It is the XRD spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film and the light conversion agent provided in the embodiment of the present invention;

[0032] Fig.10 It is the Fourier infrared spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film and the light conversion agent provided in the embodiment of the present invention;

[0033] Fig.11 It is the fluorescence emission spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film provided by the embodiment of the present invention at different excitation wavelengths;

[0034] Fig.12 It is the fluorescence excitation spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film provided by the embodiment of the present invention at different emission wavelengths;

[0035] Fig.13 It is the ultraviolet absorption spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film and the light conversion agent provided in the embodiment of the present invention;

[0036] Fig.14 It is the transmission spectrum of the PVA-based g-C3N4@Zn / Eu-MOF film provided in the embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Example 1

[0039] A method for preparing a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent comprises the following steps:

[0040] S1. Put 5g of melamine into a crucible, put the crucible into a high-temperature muffle furnace, and heat the muffle furnace from room temperature to 550℃ at a heating rate of 5℃ / min in an air atmosphere, keep it at 550℃ for 4h, and then cool it naturally to room temperature. Grind the sintered sample into powder, wash it three times with deionized water to remove residual impurities, and dry it at 60℃ for 12h to obtain powder g-C3N4;

[0041] S2. Add 44.6 mg europium nitrate, 5.9 mg zinc nitrate and 21.6 mg trimesic acid to water containing 10 mL DMF, with a volume ratio of DMF to water of 1:6, and then dissolve it by ultrasonication for 5 min. Then place it in the inner lining of a 50 ml high temperature reactor and heat it in an oven at 180 ° C for 10 h to form a milky white liquid. Centrifuge the milky white liquid at 10000 r for 30 min, discard the supernatant, and then wash the precipitate with ethanol and ultrapure water alternately for multiple times to remove the unreacted Zn 2+ / Eu 3+ and trimesic acid, and the precipitate was dried under vacuum for 10 h to obtain white powder Zn / Eu-MOF;

[0042] S3. Dissolve 0.2 g g-C3N4 in 30 ml ethanol and perform ultrasonic treatment for 30 min to fully disperse it. Then add 0.15 g Zn / Eu-MOF and stir for 2 h. Then, remove ethanol from the mixture at 70 °C to obtain the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent.

[0043] Comparative Example 1

[0044] A method for preparing a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent comprises the following steps:

[0045] S1. Using melamine to prepare powdered g-C3N4, the preparation method is the same as that in Example 1;

[0046] S2, dissolve 0.2 g g-C3N4 in 30 ml ethanol, ultrasonically treat for 30 min, centrifuge and discard the supernatant to obtain the ultrasonically stripped g-C3N4 precipitate;

[0047] S3, 44.6 mg of europium nitrate, 5.9 mg of zinc nitrate and 21.6 mg of trimesic acid were added to water containing 10 mL of DMF, with a volume ratio of DMF to water of 1:6, and then ultrasonicated for 5 min to dissolve it; then the ultrasonically stripped g-C3N4 was added, and the mixture was placed in a 50 ml high temperature reactor lining, heated at 180 ° C in an oven for 10 h, and naturally cooled to room temperature to form a light yellow suspension, and the light yellow suspension was centrifuged at 10000r for 30 min, the supernatant was poured off, and the precipitate was washed by alternating centrifugation with ethanol and ultrapure water for multiple times to remove unreacted Zn 2+ / Eu 3+ and trimesic acid, the precipitated part was vacuum dried for 10 hours to obtain a light yellow powdery light conversion agent.

[0048] Comparative Example 2

[0049] S1. Using melamine to prepare powdered g-C3N4, the preparation method is the same as that in Example 1;

[0050] S2, dissolving 0.2 g g-C3N4 in 30 ml ethanol, ultrasonically treating for 30 min, centrifuging and collecting the supernatant to obtain a g-C3N4 nanosheet suspension;

[0051] S3, 44.6 mg of europium nitrate, 5.9 mg of zinc nitrate and 21.6 mg of trimesic acid were added to a suspension of g-C3N4 nanosheets containing 10 mL of DMF, with the volume ratio of DMF to g-C3N4 nanosheet suspension being 1:6, and then sonicated for 5 min to dissolve it; then the mixture was placed in a 50 ml high temperature reactor lining, heated at 180 ° C in an oven for 10 h, and naturally cooled to room temperature to form a milky white suspension, the milky white suspension was centrifuged at 10000 r for 30 min, the supernatant was discarded, and then the precipitate was washed by alternating centrifugation with ethanol and ultrapure water for multiple times to remove unreacted Zn 2+ / Eu 3+ and trimesic acid, the precipitated part was vacuum dried for 10 hours to obtain a milky white powder light conversion agent.

[0052] The products prepared in Example 1 and Comparative Examples 1 and 2 were tested for relevant properties. The results are as follows Figure 1-8 shown.

[0053] Figure 1 and 2 This shows that Example 1 successfully prepared g-C3N4@Zn / Eu-MOF; Figure 3 It is shown that the Zn / Eu-MOF prepared in Example 1 emits red fluorescence under 250-320nm ultraviolet light; Figure 4 It can be seen that the g-C3N4@Zn / Eu-MOF light conversion agent prepared in Example 1 can emit red and blue light under ultraviolet excitation. Figure 5 It shows that the light yellow powdered light conversion agent prepared in Comparative Example 1 has weak red light under ultraviolet region excitation and cannot simultaneously excite strong red and blue light. Figure 6 It shows that the milky white powder light conversion agent prepared in Comparative Example 2 has weak blue fluorescence under ultraviolet excitation. It can be concluded that the light conversion agents prepared in Comparative Examples 1 and 2 cannot emit stable and strong red and blue light at the same time, and fail to achieve the effect of dual-energy light conversion agents. Figure 7 This shows that the emission peak of the dual-energy light conversion agent prepared in Example 1 can be excited in the ultraviolet region. Figure 8 This indicates that the products in the examples all have strong absorption in the ultraviolet region.

[0054] Example 2

[0055] A method for preparing a dual-energy light conversion film comprises dissolving 0.4 g of PVA in 20 mL of water, heating to 100° C. and maintaining for 1 hour to form a homogeneous solution, adding 0.3 g of the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent prepared in Example 1, stirring for 3 hours, pouring the mixed solution into a polystyrene culture dish, and drying at 40° C. to obtain a PVA-based dual-energy light conversion film.

[0056] The PVA-based dual-energy light conversion film prepared in Example 2 was tested for related properties. The results are as follows: Figure 9-14 shown.

[0057] Fig. 9 and Fig.10 This indicates that the g-C3N4@Zn / Eu-MOF light conversion agent was successfully loaded on the polyvinyl alcohol film; Fig.11 This indicates that the PVA-based dual-energy light-conversion film can emit the intrinsic red and blue light of the light-conversion agent under the excitation of the ultraviolet region; Fig.12 This indicates that the emission peak of the dual-energy light conversion agent prepared in Example 1 can still be excited in the ultraviolet region after being loaded onto polyvinyl alcohol. Fig.13 This shows that after the g-C3N4@Zn / Eu-MOF light conversion agent prepared in Example 1 is loaded onto the polyvinyl alcohol film, it has higher absorption in the ultraviolet region than the g-C3N4@Zn / Eu-MOF light conversion agent itself. Fig.14 This indicates that the PVA-based dual-energy light conversion film has a lower transmittance in the 250-420nm ultraviolet region than the pure polyethanol film, but has enhanced transmittance in the visible light region.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent, characterized in that: The steps include: S1, calcining melamine at high temperature to obtain g-C3N4; S2, adding europium nitrate, zinc nitrate and trimesic acid into an aqueous solvent containing N,N-dimethylformamide, performing a hydrothermal reaction after ultrasonication to obtain a reaction product, and the reaction product is centrifuged, washed and vacuum dried in sequence to obtain Zn / Eu-MOF; S3. Dissolve the g-C3N4 in ethanol and add Zn / Eu-MOF after ultrasonic treatment, and stir for a certain period of time to obtain the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent.

2. The preparation method according to claim 1, characterized in that In S1, the high temperature calcination conditions are: in an air atmosphere, heating from room temperature to 550°C at a heating rate of 5°C / min, keeping at 550°C for 4 hours, and then naturally cooling to room temperature.

3. The preparation method according to claim 1, characterized in that: In S2, the molar ratio of europium nitrate, zinc nitrate and trimesic acid is 1:0.2:

1.

4. The preparation method according to claim 1, characterized in that: In S2, the volume ratio of N,N-dimethylformamide to water in the aqueous solvent is 1:

6.

5. The preparation method according to claim 1, characterized in that: In S2, the hydrothermal conditions are: heating at 170-190°C for 8-12h.

6. The preparation method according to claim 1, characterized in that: In S3, the mass ratio of g-C3N4 to Zn / Eu-MOF is (3-4):(2-3).

7. A g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a dual-energy light conversion film, characterized in that: Heat and dissolve polyvinyl alcohol in water to form a homogeneous solution, then add the g-C3N4@Zn / Eu-MOF composite dual-energy light conversion agent prepared by the preparation method of any one of claims 1 to 6, stir evenly, and dry at 40° C. to obtain a PVA-based dual-energy light conversion film.

9. The preparation method according to claim 8, characterized in that: The preparation conditions of the homogeneous solution are as follows: polyvinyl alcohol is added into water and heated to 100-120° C. and maintained for 1-2 hours.

10. A PVA-based dual-energy light conversion film prepared by the preparation method according to claim 8 or 9.

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