Preparation method of polyvinyl alcohol composite fluorescent material

Abstract

The present application relates to a kind of preparation methods of polyvinyl alcohol composite fluorescent material, polyvinyl alcohol is dissolved in water as water phase with rhodamine 6G, benzyl alcohol is mixed with sec-butyl alcohol as oil phase, water phase is mixed with oil phase, and then freeze, flush, extraction and freeze drying are carried out in turn, and polyvinyl alcohol composite fluorescent material is prepared;The mass fraction of polyvinyl alcohol in water phase is 1-1.3wt%, the mass fraction of rhodamine 6G is 0.09-0.18wt%, and the oil phase can be recycled for 3-4 times.By the preparation method of a kind of polyvinyl alcohol composite fluorescent material of the present application, the fluorescent polyvinyl alcohol hydrogel with good mechanical property is obtained, and the application field of polyvinyl alcohol hydrogel is expanded.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology and relates to a method for preparing polyvinyl alcohol composite fluorescent materials. Background Technology

[0002] Hydrogels are an important branch of soft materials with enormous potential in various technological fields. Besides their unique viscoelasticity on a macroscopic scale, their ability to be applied in biomedicine, sensing, and optoelectronics is primarily due to the microscopic network structure created by cross-linked nanofibers. Among the diverse functional materials based on hydrogels, fluorescent hydrogels are a class of complexes that exhibit fluorescence by combining fluorescent substances with hydrogels. In recent years, organic dyes, fluorescent proteins, lanthanide ions, and carbon quantum dots have been successfully introduced into hydrogel substrates, enriching the functional types of hydrogels. Fluorescent hydrogels exist as highly water-containing swollen bodies, thus possessing excellent luminescence, flexibility, large porosity, and high water content, showing promising application prospects in sensors, bioimaging, and skin repair.

[0003] Polyvinyl alcohol (PVA) is a more biodegradable polymer that can be used in textile sizing and adhesives. It can also be modified into films or biodegradable mulches. Depending on the degree of hydrolysis, the solubility of PVA in water varies. PVA with a degree of hydrolysis of over 99% can only dissolve in hot water above 95°C, while PVA with a degree of hydrolysis between 87% and 89% can dissolve rapidly in both hot and cold water. Due to its excellent properties, PVA is a good material for preparing hydrogels. PVA hydrogels can be prepared by the following methods: (1) dissolution method; (2) freeze-drying method; (3) ion-exchange water method; (4) glycerol method; (5) calcium hydroxide method. The freeze-drying method is relatively common. It involves repeatedly freezing and thawing a polyvinyl alcohol solution at low temperatures. After 3 to 4 cycles, the polyvinyl alcohol forms a hydrogel under physical temperature change. If no cross-linking agent is used in the preparation of polyvinyl alcohol, the mechanical properties of the prepared hydrogel will decrease significantly when it is highly swollen due to water absorption, which limits its application in areas with stress load requirements. Furthermore, if a cross-linking agent is used to improve the mechanical properties of the hydrogel, the cross-linking agent can only be used once during the molding process and cannot be recycled.

[0004] Reference 1 (Preparation and Performance Study of High-Strength and High-Toughness Composite Hydrogels Based on PVA [D]. Hunan University of Technology, 2022.) prepared polyvinyl alcohol solutions of different masses and molecular weights. After preparing the polyvinyl alcohol solutions, hydrochloric acid and glutaraldehyde were introduced into the polyvinyl alcohol solutions. The hydrogels treated with room temperature-freeze-thaw-annealing exhibited excellent comprehensive mechanical properties, with a fracture stress of 14.48 MPa and an elongation at break of 1114.2%. The improvement in the mechanical properties of this hydrogel lies in the use of glutaraldehyde crosslinking agent, which can enhance the intermolecular forces. Although the use of crosslinking agent can significantly improve the properties, the crosslinking agent glutaraldehyde is for single use and cannot be recycled. Moreover, crosslinking agents such as glutaraldehyde have reproductive toxicity, which will affect the application of the hydrogel.

[0005] Reference 2 (Research on the construction of porous hydrogel of polyvinyl alcohol / γ-polyglutamic acid[J]. Guangdong Chemical Industry, 2023, 50(02):40-45.) prepared a composite hydrogel by incorporating γ-polyglutamic acid and glucomannan into polyvinyl alcohol and then cyclically freezing and thawing. The prepared hydrogel was translucent, elastic and had a certain mechanical strength. No crosslinking agent was used in the preparation of this composite hydrogel, and its mechanical properties were poor, with a fracture stress of 0.22 MPa.

[0006] Reference 3 (Preparation and performance study of PVA-carbon quantum dot composite fluorescent hydrogel[J]. Journal of Hubei University (Natural Science Edition), 2024, 46(01):77-85.) prepared fluorescent hydrogel by mixing carbon quantum dots, glycerol and polyvinyl alcohol through freeze-thaw cycles. With the addition of carbon quantum dots, the fracture stress and elongation at break of the composite hydrogel were improved to 0.75 MPa and 374%, respectively. The reason is that the silane coupling agent used in the synthesis of carbon quantum dots enhanced the interaction between polyvinyl alcohol and glycerol, which significantly enhanced the mechanical properties of the hydrogel. However, no crosslinking agent was used, so the improvement in mechanical properties was limited.

[0007] Therefore, it is of great significance to study a method for preparing polyvinyl alcohol composite fluorescent materials without the use of crosslinking agents in order to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and provide a method for preparing polyvinyl alcohol composite fluorescent materials.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a polyvinyl alcohol composite fluorescent material involves dissolving polyvinyl alcohol and rhodamine 6G in water as the aqueous phase, and mixing benzyl alcohol and sec-butanol as the oil phase. (Experiments showed that when using benzyl alcohol alone, the degree of bonding between the two phases was low after stirring the polyvinyl alcohol solution and benzyl alcohol. After the solution stabilized, the aqueous phase and oil phase appeared as two distinct phases. However, when the polyvinyl alcohol solution was mixed with a solvent composed of benzyl alcohol / sec-butanol, the boundary between the two phases disappeared, and the polyvinyl alcohol solution could exist well in the benzyl alcohol / sec-butanol mixed solution. On this basis, the addition of rhodamine 6G could aggregate the polyvinyl alcohol distributed in the oil phase, and the polyvinyl alcohol solution would encapsulate the rhodamine 6G and suspend it entirely in the oil phase, rather than being two distinct phases.) The aqueous phase and oil phase were mixed and then subjected to freezing, rinsing, extraction, and freeze-drying in sequence to obtain the polyvinyl alcohol composite fluorescent material.

[0011] The mass fraction of polyvinyl alcohol in the aqueous phase is 1–1.3 wt%, and the mass fraction of rhodamine 6G is 0.09–0.18 wt%. If the amount of polyvinyl alcohol used is too low, after dispersion, there will be droplets that cannot aggregate, thus failing to encapsulate rhodamine 6G. If the amount used is too high, it will be difficult to disperse and form in the oil phase. If the amount of rhodamine 6G used is too high, the portion transferred to the oil phase will increase, breaking through the barrier formed by polyvinyl alcohol. If the amount of rhodamine 6G used is too low, the degree of polyvinyl alcohol aggregation will be low, failing to encapsulate rhodamine 6G, and the oil phase and aqueous phase will form two distinct phases.

[0012] To obtain fluorescent polyvinyl alcohol hydrogels with good mechanical properties, it is necessary to enhance the aggregation degree of polyvinyl alcohol macromolecular chains in the solution before freezing, and to better bind with rhodamine 6G during the aggregation process. A mixed solution of benzyl alcohol and sec-butanol is considered a non-solvent for water and water-soluble polyvinyl alcohol. In this invention, this mixed solution is used as the oil phase. During the stirring and mixing of the aqueous solution containing polyvinyl alcohol and rhodamine 6G with benzyl alcohol / sec-butanol, due to the immiscibility of the aqueous phase and oil and the properties of the solvent itself, the aqueous phase can be dispersed in the oil phase solvent as droplets after stirring. However, after a period of time, because the aqueous droplets dispersed in the oil phase are unstable, the dispersed droplets tend to aggregate in order to achieve a stable state. When the droplets are dispersed, surface tension confines the substances in the aqueous phase droplets within the droplets. Benzyl alcohol and sec-butanol are good solvents for Rhodamine 6G, with higher solubility than water. Therefore, during the aggregation process to achieve a stable state, Rhodamine 6G tends to migrate from the water to the oil phase solvent. In this state, polyvinyl alcohol does not migrate to the oil phase; instead, it hinders the diffusion of Rhodamine 6G into the oil phase. Furthermore, compared to polyvinyl alcohol, Rhodamine 6G is a smaller molecule. To hinder the diffusion of Rhodamine 6G, polyvinyl alcohol needs to reduce the space between its molecular chains. Therefore, during the aggregation of aqueous droplets, polyvinyl alcohol also aggregates on the inner surface of the droplets, indirectly enhancing the intermolecular forces. This allows polyvinyl alcohol to initially form spherical aggregates, encapsulating Rhodamine 6G within them. After freezing and freeze-drying, a fluorescent hydrogel with good mechanical properties is obtained.

[0013] As a preferred technical solution:

[0014] The method for preparing polyvinyl alcohol composite fluorescent material as described above yields a polyvinyl alcohol composite fluorescent material with a yield of 70-75%.

[0015] The polyvinyl alcohol composite fluorescent material prepared as described above has a fracture stress of 3-5.9 MPa and a fracture elongation of 400-800%.

[0016] In the preparation method of the polyvinyl alcohol composite fluorescent material described above, the mass ratio of benzyl alcohol to sec-butanol in the oil phase is 8-9:1-2.

[0017] In the preparation method of the polyvinyl alcohol composite fluorescent material described above, the mass ratio of the aqueous phase to the oil phase is 1:1 to 1.2.

[0018] In the preparation method of the polyvinyl alcohol composite fluorescent material described above, the mixing temperature of the aqueous phase and the oil phase is 25°C, the mixing time is 1-2 min, the standing time after mixing is 2-2.5 h, and the oil phase can be recycled 3-4 times.

[0019] The preparation method of the polyvinyl alcohol composite fluorescent material as described above involves freezing with liquid nitrogen or freezing at -20°C for 5 min or 12 h, followed by thawing at 25°C for 2 h, and repeating the freezing-thawing process 3 times.

[0020] In the preparation method of the polyvinyl alcohol composite fluorescent material described above, rinsing refers to rinsing with deionized water at a temperature of 4-5℃.

[0021] The extraction temperature was 4–5℃, the extraction time was 24 h, and the extraction solvent used was deionized water.

[0022] The freeze-drying process is as follows: first, freeze at -70℃, then freeze-dry under a vacuum of 2Pa for 48–50 hours.

[0023] Beneficial effects:

[0024] (1) A method for preparing a polyvinyl alcohol composite fluorescent material according to the present invention is to dissolve polyvinyl alcohol and rhodamine 6G in water as an aqueous phase, and to mix benzyl alcohol and sec-butanol as an oil phase. Without using a crosslinking agent, a polyvinyl alcohol hydrogel with excellent mechanical properties is obtained by mixing the aqueous phase and the oil phase, i.e., a polyvinyl alcohol composite fluorescent material.

[0025] (2) The preparation method of polyvinyl alcohol composite fluorescent material of the present invention expands the application field of polyvinyl alcohol hydrogel. Attached Figure Description

[0026] Figure 1 The image shows the infrared spectrum of the polyvinyl alcohol composite fluorescent material of Example 1. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] The testing method involved in this invention is as follows:

[0029] Fracture stress and elongation at break: Referring to GB / T 528-2009, the polyvinyl alcohol composite fluorescent material was cut into standard dumbbell-shaped test strips and its mechanical properties were tested using a universal testing machine at room temperature. The specific test parameters were set as follows: initial tensile distance of 5 mm and tensile rate of 5 mm / min; 5 groups of experiments were repeated for each group, and the final result was the average value.

[0030] Example 1

[0031] A method for preparing a polyvinyl alcohol composite fluorescent material, the specific steps of which are as follows:

[0032] (1) Polyvinyl alcohol (manufacturer: Aladdin Reagent (Shanghai) Co., Ltd., CAS: 9002-89-5) was dissolved in water at 90℃ to obtain a polyvinyl alcohol aqueous solution. After cooling, Rhodamine 6G was dissolved in the polyvinyl alcohol aqueous solution at 25℃ as the aqueous phase. The mass fraction of polyvinyl alcohol in the aqueous phase was 1 wt%, and the mass fraction of Rhodamine 6G was 0.09 wt%.

[0033] (2) At 25°C, benzyl alcohol and sec-butanol were mixed in a mass ratio of 9:2 and used as the oil phase;

[0034] (3) Mix the water phase and oil phase at a mass ratio of 1:1 at 25℃ for 2 min and let stand for 2 h. Then use a dropper to remove the oil phase outside the polyvinyl alcohol. The oil phase can be recycled 4 times.

[0035] (4) The product of step (3) was frozen at -20℃ for 12 hours and thawed at 25℃ for 2 hours, and the cycle was repeated 3 times.

[0036] (5) The product from step (4) was washed and extracted sequentially with deionized water at a temperature of 4°C for 24 hours.

[0037] (6) The product of step (5) is first frozen at -70°C and then freeze-dried for 48 hours under a vacuum of 2Pa to obtain polyvinyl alcohol composite fluorescent material.

[0038] The yield of the final polyvinyl alcohol composite fluorescent material was 70%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 3 MPa, and the elongation at break was 400%.

[0039] like Figure 1 As shown, in the range of 1000–2000 cm -1 The presence of infrared characteristic peaks for polyvinyl alcohol and rhodamine 6G indicates that polyvinyl alcohol and rhodamine 6G have successfully bound together.

[0040] Comparative Example 1

[0041] A method for preparing a polyvinyl alcohol composite fluorescent material is basically the same as in Example 1, except that the mass fraction of Rhodamine 6G in step (1) is 0.06 wt%.

[0042] The final polyvinyl alcohol composite fluorescent material had a fracture stress of 0.85 MPa and an elongation at break of 220%.

[0043] When Rhodamine 6G is added in small amounts, the resulting polyvinyl alcohol composite fluorescent material has poor dimensional stability, is prone to deformation after standing for 12 hours, and cannot be coated with Rhodamine 6G after mixing the aqueous and oil phases.

[0044] Comparing Comparative Example 1 and Example 1, it can be found that the mechanical properties of Comparative Example 1 are reduced. This is because the amount of Rhodamine 6G added is too small. During the transfer to the oil phase, the polyvinyl alcohol molecular chains do not need to form a tight structural state to confine Rhodamine 6G inside. Therefore, no pre-aggregates are formed, and thus it is impossible to form a hydrogel with improved mechanical properties during the subsequent freeze-thaw process.

[0045] Comparative Example 2

[0046] A method for preparing a polyvinyl alcohol composite fluorescent material is basically the same as in Example 1, except that benzyl alcohol is replaced with an equal mass of sec-butanol in step (2), that is, only sec-butanol is used as the oil phase.

[0047] The final polyvinyl alcohol composite fluorescent material had a fracture stress of 0.62 MPa and an elongation at break of 270%.

[0048] Comparing Comparative Example 2 with Example 1, it can be found that the mechanical properties of Comparative Example 2 are reduced. This is because benzyl alcohol is not used, while sec-butanol has a certain solubility in water. That is, Rhodamine 6G has good solubility in water / sec-butanol solution and will not transfer significantly into the oil phase. As a result, polyvinyl alcohol cannot form pre-aggregates and cannot form hydrogels with improved mechanical properties in the subsequent freeze-thaw process.

[0049] Comparative Example 3

[0050] A method for preparing a polyvinyl alcohol composite fluorescent material is basically the same as in Example 1, except that in step (2), sec-butanol is replaced with an equal mass of benzyl alcohol, that is, only benzyl alcohol is used as the oil phase.

[0051] The final polyvinyl alcohol composite fluorescent material had a fracture stress of 0.94 MPa and an elongation at break of 240%.

[0052] Comparing Comparative Example 3 with Example 1, it can be found that the mechanical properties of Comparative Example 3 are reduced. This is because without the use of sec-butanol, the dispersed droplets formed by stirring during the mixing process of the aqueous and oil phases will quickly aggregate together to form two distinct phases. Rhodamine 6G will transfer to the oil phase at a faster rate, and polyvinyl alcohol will not yet form a pre-aggregate with relatively tight molecular chains. Therefore, the improvement in mechanical properties during the subsequent freeze-thaw process is limited.

[0053] Example 2

[0054] A method for preparing a polyvinyl alcohol composite fluorescent material is basically the same as in Example 1, except that step (2) is omitted and the oil phase is replaced with the oil phase separated from the outside of the polyvinyl alcohol in step (3) of Example 1.

[0055] The yield of the final polyvinyl alcohol composite fluorescent material was 70%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 2.9 MPa, and the elongation at break was 390%.

[0056] Example 3

[0057] A method for preparing a polyvinyl alcohol composite fluorescent material, the specific steps of which are as follows:

[0058] (1) Polyvinyl alcohol (manufacturer: Aladdin Reagent (Shanghai) Co., Ltd., CAS: 9002-89-5) was dissolved in water at 90℃ to obtain a polyvinyl alcohol aqueous solution. After cooling, Rhodamine 6G was dissolved in the polyvinyl alcohol aqueous solution at 25℃ as the aqueous phase. The mass fraction of polyvinyl alcohol in the aqueous phase was 1.3wt%, and the mass fraction of Rhodamine 6G was 0.18wt%.

[0059] (2) At 25°C, benzyl alcohol and sec-butanol were mixed in a mass ratio of 8:1 and used as the oil phase;

[0060] (3) Mix the aqueous phase and oil phase at a mass ratio of 1:1.2 at 25℃ for 2 min and let stand for 2 h. The oil phase can be recycled 3 times.

[0061] (4) The product of step (3) was frozen in liquid nitrogen for 5 min and thawed at 25°C for 2 h, and the cycle was repeated 3 times.

[0062] (5) The product from step (4) was washed and extracted sequentially with deionized water at a temperature of 5°C for 24 hours.

[0063] (6) The product of step (5) is first frozen at -70°C and then freeze-dried for 48 hours under a vacuum of 2Pa to obtain polyvinyl alcohol composite fluorescent material.

[0064] The yield of the final polyvinyl alcohol composite fluorescent material was 75%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 5.9 MPa, and the elongation at break was 800%.

[0065] Example 4

[0066] A method for preparing a polyvinyl alcohol composite fluorescent material, the specific steps of which are as follows:

[0067] (1) Polyvinyl alcohol (manufacturer: Aladdin Reagent (Shanghai) Co., Ltd., CAS: 9002-89-5) was dissolved in water at 90℃ to obtain a polyvinyl alcohol aqueous solution. After cooling, Rhodamine 6G was dissolved in the polyvinyl alcohol aqueous solution at 25℃ as the aqueous phase. The mass fraction of polyvinyl alcohol in the aqueous phase was 1.2wt%, and the mass fraction of Rhodamine 6G was 0.14wt%.

[0068] (2) Benzyl alcohol and sec-butanol were mixed at a mass ratio of 8.5:1.5 at 25°C and used as the oil phase;

[0069] (3) Mix the aqueous phase and oil phase at a mass ratio of 1:1.15 at 25℃ for 1.5 min and let stand for 2.25 h. The oil phase can be recycled 3 times.

[0070] (4) The product of step (3) was frozen at -20℃ for 12 hours and thawed at 25℃ for 2 hours, and the cycle was repeated 3 times.

[0071] (5) The product from step (4) was washed and extracted sequentially with deionized water at a temperature of 4°C for 24 hours.

[0072] (6) The product of step (5) is first frozen at -70°C and then freeze-dried for 49 hours under a vacuum of 2Pa to obtain polyvinyl alcohol composite fluorescent material.

[0073] The yield of the final polyvinyl alcohol composite fluorescent material was 73%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 4.8 MPa, and the elongation at break was 600%.

[0074] Example 5

[0075] A method for preparing a polyvinyl alcohol composite fluorescent material, the specific steps of which are as follows:

[0076] (1) Polyvinyl alcohol (manufacturer: Aladdin Reagent (Shanghai) Co., Ltd., CAS: 9002-89-5) was dissolved in water at 90℃ to obtain a polyvinyl alcohol aqueous solution. After cooling, Rhodamine 6G was dissolved in the polyvinyl alcohol aqueous solution at 25℃ as the aqueous phase. The mass fraction of polyvinyl alcohol in the aqueous phase was 1 wt%, and the mass fraction of Rhodamine 6G was 0.09 wt%.

[0077] (2) At 25°C, benzyl alcohol and sec-butanol were mixed in a mass ratio of 8:1 and used as the oil phase;

[0078] (3) Mix the water phase and oil phase at a mass ratio of 1:1 at 25℃ for 1 min and let stand for 2.5 h. The oil phase can be recycled 4 times.

[0079] (4) The product of step (3) was frozen in liquid nitrogen for 5 min and thawed at 25°C for 2 h, and the cycle was repeated 3 times.

[0080] (5) The product from step (4) was washed and extracted sequentially with deionized water at a temperature of 5°C for 24 hours.

[0081] (6) The product of step (5) is first frozen at -70°C and then freeze-dried for 49 hours under a vacuum of 2Pa to obtain polyvinyl alcohol composite fluorescent material.

[0082] The yield of the final polyvinyl alcohol composite fluorescent material was 70%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 4.6 MPa, and the elongation at break was 570%.

[0083] Example 6

[0084] A method for preparing a polyvinyl alcohol composite fluorescent material, the specific steps of which are as follows:

[0085] (1) Polyvinyl alcohol (manufacturer: Aladdin Reagent (Shanghai) Co., Ltd., CAS: 9002-89-5) was dissolved in water at 90℃ to obtain a polyvinyl alcohol aqueous solution. Then, rhodamine 6G was dissolved in the polyvinyl alcohol aqueous solution at 25℃ to form the aqueous phase. The mass fraction of polyvinyl alcohol in the aqueous phase was 1.3wt%, and the mass fraction of rhodamine 6G was 0.18wt%.

[0086] (2) At 25°C, benzyl alcohol and sec-butanol were mixed in a mass ratio of 9:2 and used as the oil phase;

[0087] (3) Mix the water phase and oil phase at a mass ratio of 1:1 at 25℃ for 1 min and let stand for 2.5 h. The oil phase can be recycled 3 times.

[0088] (4) The product of step (3) was frozen at -20℃ for 12 hours and thawed at 25℃ for 2 hours, and the cycle was repeated 3 times.

[0089] (5) The product from step (4) was washed and extracted sequentially with deionized water at a temperature of 4°C for 24 hours.

[0090] (6) The product of step (5) is first frozen at -70°C and then freeze-dried for 50 hours under a vacuum of 2Pa to obtain polyvinyl alcohol composite fluorescent material.

[0091] The yield of the final polyvinyl alcohol composite fluorescent material was 75%; the fracture stress of the polyvinyl alcohol composite fluorescent material was 5.4 MPa, and the elongation at break was 720%.

Claims

1. A method for preparing a polyvinyl alcohol composite fluorescent material, characterized in that: Polyvinyl alcohol and rhodamine 6G were dissolved in water to form the aqueous phase, and benzyl alcohol and sec-butanol were mixed to form the oil phase. The aqueous phase and oil phase were then subjected to freezing, rinsing, extraction and freeze-drying in sequence to obtain polyvinyl alcohol composite fluorescent material. The mass fraction of polyvinyl alcohol in the aqueous phase was 1–1.3 wt%, and the mass fraction of rhodamine 6G was 0.09–0.18 wt%. The mass ratio of benzyl alcohol to sec-butanol in the oil phase is 8~9:1~2; The mass ratio of the aqueous phase to the oil phase is 1:1 to 1.2; The fracture stress of polyvinyl alcohol composite fluorescent materials is 3~5.9 MPa, and the elongation at break is 400~800%.

2. The method for preparing a polyvinyl alcohol composite fluorescent material according to claim 1, characterized in that, The yield of polyvinyl alcohol composite fluorescent materials is 70-75%.

3. The method for preparing a polyvinyl alcohol composite fluorescent material according to claim 1, characterized in that, The mixing temperature of the aqueous phase and the oil phase is 25 ℃, the mixing time is 1~2 min, the standing time after mixing is 2~2.5 h, and the oil phase can be recycled 3~4 times.

4. The method for preparing a polyvinyl alcohol composite fluorescent material according to claim 1, characterized in that, The freezing method is liquid nitrogen freezing or freezing at -20 ℃ for 5 min or 12 h, followed by thawing at 25 ℃ for 2 h, and the cycle is repeated 3 times.

5. The method for preparing a polyvinyl alcohol composite fluorescent material according to claim 1, characterized in that, Rinsing refers to rinsing with deionized water at a temperature of 4~5℃; The extraction temperature was 4~5 ℃, the extraction time was 24 h, and the extraction solvent used was deionized water; The freeze-drying process is as follows: first, freeze at -70℃, then freeze-dry under a vacuum of 2 Pa for 48~50 h.

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