High-temperature-resistant organic fluorescent powder and preparation method thereof

Abstract

The application discloses a high-temperature-resistant organic fluorescent powder and a preparation method thereof. The organic fluorescent powder comprises a fluorescent seed formed by a poly-methyl methacrylate (PMMA) coated Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material, and a silica aerogel layer coated on the surface of the fluorescent seed. In the preparation, the organic fluorescent seed is prepared first, then the fluorescent seed is introduced in the preparation of the silica aerogel, and finally the high-temperature-resistant organic fluorescent powder with a core-shell structure is synthesized. The high-temperature-resistant light conversion powder can not only realize up-conversion and down-conversion, but also can improve the high-temperature resistance and optical performance of the light conversion powder, reduce light loss, improve mechanical performance, and adapt to the preparation mode of downstream products such as high-temperature extrusion.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature resistant fluorescent materials and their preparation methods, and particularly relates to a high-temperature resistant organic phosphor and its preparation method. Background Technology

[0002] Light-converting materials are a class of functional materials that can convert ultraviolet or near-infrared light from sunlight into blue, green, and red light that can be used for plant photosynthesis. These materials have important applications in agriculture and solar cells.

[0003] Optical conversion materials are broadly classified into inorganic and organic materials. In practical industrialization, inorganic optical conversion materials exhibit strong temperature resistance and aging resistance, but they have poor compatibility with various systems. When combined with other systems, they can easily lead to a decline in the optical performance of the final product. More importantly, the fluorescence conversion of inorganic materials is weak and inefficient, often requiring the addition of excessive amounts of inorganic materials to achieve the desired fluorescence intensity, resulting in high costs. On the other hand, organic optical conversion materials have high luminescence intensity, require low addition amounts, and have good compatibility with various organic solvents and resins. However, organic optical conversion materials have poor high-temperature resistance and weak aging resistance. In practical applications, after high-temperature treatment, organic optical conversion materials are destroyed, and the fluorescence of the final product decays to almost nothing.

[0004] In existing technologies, the light-converting agents used mostly have a single light-converting effect, only achieving a single downconversion or upconversion. For example, the patent publication text with patent application number 2018107000301 mentions that europium complex composite fluorescent materials are prepared by using europium ions as the emitting element, triphenylphosphine oxide (TPPO) and 2-thiophenecarboxylic acid trifluoroacetone (TTA) as organic ligands, and calcium carbonate as the matrix, under specified conditions. This method can only obtain a single downconversion fluorescent material. Furthermore, the composite fluorescent material with rare earth ion organic ligands does not adhere tightly to the inorganic material. Although the inorganic material has good high-temperature resistance, the poor adhesion between the composite fluorescent material with rare earth ion organic ligands and the inorganic material causes the rare earth ion organic ligands to detach from the inorganic material during high-temperature preparation, resulting in the destruction of some rare earth ion organic ligands at high temperatures.

[0005] Furthermore, although coating with organic or inorganic materials can improve high-temperature resistance to some extent, coating with one or more layers of film structure will significantly reduce the luminescence intensity of fluorescent materials. Under such circumstances, when used in subsequent preparation processes, most fluorescent composite materials have already lost their fluorescent effect.

[0006] Therefore, we are now studying a light-converting powder that can withstand high temperatures and convert light up and down without affecting the fluorescence intensity of the light-converting powder itself. Summary of the Invention

[0007] Purpose of the invention: The technical problem to be solved by the present invention is to provide an organic phosphor with a core-shell structure. This organic phosphor can not only achieve up-and-down light conversion and is resistant to high temperature, but also effectively avoids the problem of light loss caused by the formation of a core-shell structure.

[0008] Technical solution: The present invention provides a high-temperature resistant organic phosphor, which comprises Sm, a phosphor with up-and-down light conversion function, coated with polymethyl methacrylate. 0.4 Yb 0.2 Er 0.4 Fluorescent seeds formed from (HTTA)3Phen fluorescent material, and a silica aerogel layer covering the surface of the fluorescent seeds.

[0009] The Sm of the present invention 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material uses Yb 3+ Er 3+ and Sm 3+ Ions are simultaneously doped onto HTTA and phen ligands to obtain optically convertible powders capable of both up-and-down optical conversion. The preparation process and optical conversion mechanism are as follows:

[0010]

[0011] I. Down-conversion light process

[0012] 1. Absorption of excitation light: When Sm(TTA)3Phen phosphor is excited by light of a specific wavelength, such as in the ultraviolet or blue light region, the ligands HTTA (2-thiophenecarboxyltrifluoroacetone) and phen (1,10-phenanthroline) in its molecule absorb the energy of the photon.

[0013] 2. Energy transfer: The absorbed energy is transferred to the central Sm³⁺ ion. Due to the excellent antenna effect of HTTA and phen, the absorbed energy can be effectively concentrated on the Sm³⁺ ion, causing the Sm³⁺ ion to transition from the ground state to the excited state.

[0014] 3. Emission Process: Energy Level Transitions of Sm³⁺ Ions: Sm³⁺ ions possess abundant 4f-4f transition energy levels. In the excited state, Sm³⁺ ions undergo nonradiative relaxation processes, transitioning energy from higher energy levels to lower energy levels, eventually returning to the ground state. During this process, energy is released in the form of light, resulting in fluorescence emission.

[0015] 4. Characteristic emission peaks: The characteristic emission peaks of Sm³⁺ ions are mainly concentrated in the visible light region, such as 564 nm (green light), 602 nm (orange light), and 645 nm (red light). These emission peaks correspond to the transitions of Sm³⁺ ions, such as 4G5 / 2→6H5 / 2, 4G5 / 2→6H7 / 2, and 4G5 / 2→6H9 / 2.

[0016] II. Upconversion process

[0017] Yb³⁺ and Er³⁺ co-doped phosphors exhibit upconversion luminescence properties, meaning they emit higher-energy visible light when excited by lower-energy light (such as infrared light). The specific luminescence mechanism is as follows:

[0018] Upconversion green light emission changes slowly with increasing Yb³⁺ ion concentration, while upconversion red light emission increases with increasing Yb³⁺ ion concentration. The emission color of the phosphor can be modulated by changing the Yb³⁺ ion doping concentration; as the Yb³⁺ ion concentration increases, the phosphor emission gradually changes from green to red.

[0019] Luminescence Mechanism: Both upconversion green and red light emission are two-photon processes. Cross-relaxation plays a dominant role in upconversion red light emission. Green light emission at 533 nm and 557 nm, and red light emission at 688 nm, are all two-photon processes. Under 980 nm laser excitation, Yb³⁺ is excited from the ground state 2F7 / 2 to the excited state 2F5 / 2. Then, through energy transfer processes ET1 and ET2, an Er³⁺ 4F7 / 2 energy level population is formed. Following nonradiative relaxation processes NR1 and NR2, 2H₂ is formed. 11 The populations of the / 2 and 4S3 / 2 energy levels are ultimately determined through the radiative transition process 2H. 11 / 2→4I 15 / 2 and 4S3 / 2→4I 15 / 2 emitted light (green light) 4 F 9 / 2 →4I 15 / 2 (red light).

[0020] Based on the above fluorescent materials, this invention first forms a PMMA encapsulation layer, and then forms a silica aerogel layer on top of this PMMA encapsulation layer. By first forming the PMMA encapsulation layer, not only is uniform encapsulation of the fluorescent material achieved by the silica aerogel layer, but the high-temperature resistance of the prepared organic phosphor is also improved. Simultaneously, coating the outermost layer with a silica aerogel layer whose refractive index is closer to that of the atmosphere creates a more effective bilayer dielectric structure, reducing the luminescence loss of the prepared organic phosphor.

[0021] Furthermore, the Sm organic phosphor used in this invention... 0.4 Yb0.2 Er 0.4 (HTTA)3Phen fluorescent material is prepared by the following steps:

[0022] (1) The contents of Yb 3+ Er 3+ and Sm 3+ A mixture of rare earth metal salts containing ions, α-thiophenecarboxyltrifluoroacetone, and 1,10-phenanthroline are dissolved in ethanol; wherein, in the rare earth metal salt mixture, Yb 3+ Er 3+ and Sm 3+ The molar ratio of the ions is 1:2:2, α-thiophenecarboxyltrifluoroacetone and Yb 3+ Er 3+ and Sm 3+ The total molar ratio of the three is 3:1, and the molar ratio of 1,10-phenanthroline to α-thiophenecarboxylic acid trifluoroacetone is 1:3.

[0023] (2) The α-thiophenecarboxyltrifluoroacetone solution was stirred in a water bath at 60-65℃, and a mixture of rare earth metal salts and 1,10-phenanthroline solution was added to prepare a mixed reaction solution;

[0024] (3) Adjust the pH of the mixed reaction solution to 6-7 and react for 6-7 hours to obtain a precipitate. After washing and drying, obtain Sm. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material.

[0025] The method for preparing the above-mentioned high-temperature resistant organic phosphor according to the present invention includes the following steps:

[0026] (1) Preparation of fluorescent seeds: Methyl methacrylate and Sm are mixed at a mass ratio of 40:(1-2). 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material was mixed with ethylene glycol di(methacrylate) crosslinking agent (1-3% by mass of methyl methacrylate) and ultrasonically stirred for 3-5 minutes to obtain a mixture. This mixture was then added to ethanol and stirred for 2-4 hours. After centrifugation and drying, PMMA-Sm was obtained. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent seeds;

[0027] (2) Preparation of organic phosphor: Prepare fluorescent seeds, alcohol solvent and water in a mass ratio of 1:(20-35):(8-16); mix alcohol solvent and water evenly, add tetraethyl silicate to prepare sol, the mass ratio of tetraethyl silicate to fluorescent seeds is (1-4):2; add acid catalyst to sol to adjust pH to 3-4, stir at 1000-1600 rpm for 2-4 h to carry out hydrolysis reaction; reduce stirring speed to 300-500 rpm, add alkaline catalyst to adjust pH to 9-10, carry out condensation reaction to obtain wet gel, then add fluorescent seeds to wet gel, stir evenly, age at room temperature for 24-36 h, dry under normal pressure to obtain organic phosphor with silica aerogel layer on surface.

[0028] In preparing organic phosphors, this invention introduces fluorescent seeds during the preparation of silica aerogel. Under alkaline catalytic conditions, the groups on the surface of PMMA react with the hydroxyl groups of the synthesized silica aerogel, thereby improving the bonding force between PMMA and the silica aerogel layer. Simultaneously, it effectively reduces the hydroxyl groups in the silica aerogel network, reduces capillary action, prevents aerogel collapse, and improves the mechanical properties of the aerogel layer structure. This ultimately forms an organic phosphor that not only has high-temperature resistance but also excellent mechanical properties and reduces luminescence loss.

[0029] Furthermore, the preparation of the organic phosphor by the present invention also includes step (3) surface modification: sodium secondary alkyl sulfonate, BYK-190 polyurethane dispersant and BYK-358 acrylic leveling agent are mixed in a mass ratio of (5-7):(3-5):1, and then added to the alcohol solvent of the organic phosphor in a proportion of 5-8% of the organic phosphor mass, and stirred for 40-60 min to complete the surface modification of the phosphor.

[0030] Furthermore, in step (2) of the present invention for preparing the organic phosphor, the alcohol solvent is methanol, ethanol or isopropanol.

[0031] Furthermore, in step (2) of the present invention for preparing the organic phosphor, the acid catalyst is citric acid, tartaric acid or acetic acid; the base catalyst is ammonia or sodium hydroxide.

[0032] Furthermore, in step (2) of the present invention for preparing the organic phosphor, the atmospheric pressure drying is performed sequentially at 70-80℃ for 2-3 hours and at 90-120℃ for 5-7 hours.

[0033] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: The high-temperature resistant light-converting powder of the present invention can not only achieve the upper and lower light conversion effects; at the same time, after being fully coated with PMMA and silica aerogel, the high-temperature resistance and optical properties of the light-converting powder are improved, the light loss is reduced, the mechanical properties are improved, and it can adapt to the preparation methods of downstream products such as high-temperature extrusion. Attached Figure Description

[0034] Figure 1 SA@PMMA-Sm in Example 2 0.4 Yb 0.2 Er 0.4 SEM image of (HTTA)3Phen organic phosphor;

[0035] Figure 2 For SA@Sm in Comparative Example 2 0.4 Yb 0.2 Er 0.4 SEM image of (HTTA)3Phen organic phosphor. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] It should be noted that all raw materials used in this invention are commercially available. The CAS numbers of some of the raw materials used are shown in Table 1 below.

[0038] Table 1 CAS Numbers of Some Raw Materials

[0039] Serial Number raw material CAS number 1 α-Thiophenecarboxyltrifluoroacetone 326-91-0 2 1,10-Phenanthroline 66-71-7 3 Methyl methacrylate 80-62-6 4 Ethylene glycol di(methacrylate) 97-90-5 5 Tetraethyl silicate 78-10-4

[0040] Example 1

[0041] The high-temperature resistant organic phosphor of Example 1 was prepared by the following steps:

[0042] (1) Preparation of Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material:

[0043] ① Mix 1 mol of YbCl3·6H2O, 2 mol of SmCl3·6H2O, and 2 mol of ErCl3·6H2O (Yb 3+ Er 3+ and Sm 3+ A mixture with a molar ratio of 1:2:2, 15 mol of α-thiophenecarboxylic acid trifluoroacetone (HTTA) and 5 mol of 1,10-phenanthroline (phen) were dissolved in ethanol.

[0044] ② Add the ethanol solution of HTTA to a three-necked flask and stir and reflux in a water bath at 60°C; add the mixed solution of YbCl3·6H2O, SmCl3·6H2O and ErCl3·6H2O and the ethanol solution of phen to the three-necked flask in sequence to prepare a mixed reaction solution.

[0045] ③ The pH of the reaction mixture was adjusted to 6 by adding 1 mol / L sodium hydroxide ethanol solution dropwise; then the mixture was reacted at 60 °C in a water bath for 6 h; after the reaction was complete, the mixture was centrifuged at 10000 r / min to obtain a precipitate; the precipitate was centrifuged, washed with water and ethanol, and this process was repeated three times, and then dried in a vacuum oven at 60 °C for 12 h to obtain Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder.

[0046] (2) Preparation of fluorescent seeds:

[0047] Methyl methacrylate (MMA) and Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder was mixed at a mass ratio of 40:1, and ethylene glycol di(methacrylate) (EGDMA), a crosslinking agent accounting for 1% of the mass of methyl methacrylate, was added. The mixture was ultrasonically stirred for 5 min. Then, the mixture was added dropwise to a three-necked flask containing ethanol at a rate of 5 ml / min. The mixture was then reacted at a water bath temperature of 60°C and a stirring speed of 800 rpm for 2 h. After the addition was completed, the mixture was centrifuged at 10,000 rpm and dried in a vacuum oven at 60°C for 4 h to obtain PMMA-Sm. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent seeds.

[0048] (3) Preparation of organic phosphors:

[0049] ① Prepare fluorescent seeds, ethanol and water in a mass ratio of 1:20:8; after mixing ethanol and water evenly, add tetraethyl silicate to prepare a sol. The mass ratio of tetraethyl silicate to fluorescent seeds is 3:2. Add citric acid to the sol to adjust the pH to 3, and carry out the hydrolysis reaction for 2 hours under stirring at 1000 rpm.

[0050] ② Reduce the rotation speed to 300 rpm, add ammonia to adjust the pH to 9, and carry out a condensation reaction to obtain a wet gel;

[0051] ③ Add fluorescent seeds to the wet gel, stir evenly, age at room temperature for 30 hours, then dry the wet gel at 70°C for 3 hours, and then continue to dry at 100°C for 7 hours to finally obtain an organic phosphor with a silica aerogel layer on the surface.

[0052] Comparative Example 1

[0053] The difference between Comparative Example 1 and Example 1 lies in the use of silica for encapsulation, specifically including the following steps:

[0054] (1) Preparation of PMMA-Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent seeds: Same as in Example 1;

[0055] (2) Preparation of organic phosphor: The fluorescent seeds were added to a mixed solvent of ethanol and water (volume ratio 2:1) and stirred until homogeneous as component A; water, ethanol and ammonia were mixed at a volume ratio of 20:60:10 for 30 min to obtain component B; tetraethyl orthosilicate and ethanol were mixed at a mass ratio of 10:90 for 30 min to obtain component C. Then component B was poured into a three-necked flask reactor and stirred at a speed of 800 rpm / min, with a water bath temperature of 60-65℃; at this time, component A was quickly added to component B while maintaining a constant stirring speed. After 1 min, component C was added dropwise to the three-necked flask at a speed of 30-60 ml / min, while the stirring speed was slowly reduced to 500 rpm / min, and the reaction was maintained for 2 h. Finally, SiO2@PMMA-Sm was separated by centrifugation at 8000 rpm / min. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen microspheres were washed three times with ethanol.

[0056] Example 2

[0057] The high-temperature resistant organic phosphor of Example 2 was prepared by the following steps:

[0058] (1) Preparation of Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material:

[0059] ① Mix 1 mol of YbCl3·6H2O, 2 mol of SmCl3·6H2O, and 2 mol of ErCl3·6H2O (Yb 3+ Er 3+ and Sm 3+A mixture with a molar ratio of 1:2:2, 15 mol of α-thiophenecarboxylic acid trifluoroacetone (HTTA) and 5 mol of 1,10-phenanthroline (phen) were dissolved in ethanol.

[0060] ② Add the ethanol solution of HTTA to a three-necked flask and stir and reflux in a water bath at 60°C; add the mixed solution of YbCl3·6H2O, SmCl3·6H2O and ErCl3·6H2O and the ethanol solution of phen to the three-necked flask in sequence to prepare a mixed reaction solution.

[0061] ③ The pH of the reaction mixture was adjusted to 7 by adding 1 mol / L sodium hydroxide ethanol solution dropwise; then the mixture was reacted in a water bath at 60 °C for 6 h; after the reaction was complete, the mixture was centrifuged at 10000 r / min to obtain a precipitate; the precipitate was centrifuged, washed with water and ethanol, and this process was repeated three times, and then dried in a vacuum oven at 60 °C for 12 h to obtain Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder.

[0062] (2) Preparation of fluorescent seeds:

[0063] Methyl methacrylate (MMA) and Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder was mixed at a mass ratio of 20:1, and ethylene glycol di(methacrylate) (EGDMA), a crosslinking agent accounting for 1% of the mass of methyl methacrylate, was added. The mixture was ultrasonically stirred for 5 min. Then, the mixture was added dropwise to a three-necked flask containing ethanol at a rate of 5 ml / min. The mixture was then reacted at a water bath temperature of 60°C and a stirring speed of 800 rpm for 2 h. After the addition was completed, the mixture was centrifuged at 10,000 rpm and dried in a vacuum oven at 60°C for 4 h to obtain PMMA-Sm. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent seeds.

[0064] (3) Preparation of organic phosphors:

[0065] ① Prepare fluorescent seeds, ethanol and water in a mass ratio of 1:35:16; after mixing ethanol and water evenly, add tetraethyl silicate to prepare a sol. The mass ratio of tetraethyl silicate to fluorescent seeds is 1:2. Add citric acid to the sol to adjust the pH to 4, and carry out the hydrolysis reaction for 4 hours while stirring at 1000 rpm.

[0066] ② Reduce the rotation speed to 300 rpm, add ammonia to adjust the pH to 10, and carry out a condensation reaction to obtain a wet gel;

[0067] ③ Add fluorescent seeds to the wet gel, stir evenly, age at room temperature for 36 hours, then dry the wet gel at 80°C for 2 hours, and then continue to dry at 120°C for 5 hours to finally obtain an organic phosphor with a silica aerogel layer on the surface.

[0068] Comparative Example 2

[0069] The difference between Comparative Example 2 and Example 2 is that it does not encapsulate with PMMA, but instead directly encapsulates with silica aerogel, specifically including the following steps:

[0070] (1) Preparation of Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material:

[0071] ① Mix 1 mol of YbCl3·6H2O, 2 mol of SmCl3·6H2O, and 2 mol of ErCl3·6H2O (Yb 3+ Er 3+ and Sm 3+ A mixture with a molar ratio of 1:2:2, 15 mol of α-thiophenecarboxylic acid trifluoroacetone (HTTA) and 5 mol of 1,10-phenanthroline (phen) were dissolved in ethanol.

[0072] ② Add the ethanol solution of HTTA to a three-necked flask and stir and reflux in a water bath at 60°C; add the mixed solution of YbCl3·6H2O, SmCl3·6H2O and ErCl3·6H2O and the ethanol solution of phen to the three-necked flask in sequence to prepare a mixed reaction solution.

[0073] ③ The pH of the reaction mixture was adjusted to 7 by adding 1 mol / L sodium hydroxide ethanol solution dropwise; then the mixture was reacted in a water bath at 60 °C for 6 h; after the reaction was complete, the mixture was centrifuged at 10000 r / min to obtain a precipitate; the precipitate was centrifuged, washed with water and ethanol, and this process was repeated three times, and then dried in a vacuum oven at 60 °C for 12 h to obtain Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder.

[0074] (2) Preparation of organic phosphors:

[0075] ① Mix Sm at a mass ratio of 1:35:16 0.4 Yb0.2 Er 0.4 Prepare (HTTA)3Phen powder, ethanol, and water; mix ethanol and water evenly, then add tetraethyl silicate to prepare a sol. The mass ratio of tetraethyl silicate to fluorescent seeds is 1:2. Add citric acid to the sol to adjust the pH to 4, and carry out the hydrolysis reaction for 4 hours with stirring at 1000 rpm.

[0076] ② Reduce the rotation speed to 300 rpm, add ammonia to adjust the pH to 10, and carry out a condensation reaction to obtain a wet gel.

[0077] ③ Add fluorescent seeds to the wet gel, stir evenly, age at room temperature for 36 hours, then dry the wet gel at 80°C for 2 hours, and then continue to dry at 120°C for 5 hours to finally obtain an organic phosphor with a silica aerogel layer on the surface.

[0078] Performance Test 1: Optical Intensity Test

[0079] The high-temperature resistant organic phosphors prepared in Example 1 and Comparative Example 1 of this invention were tested for their up-and-down conversion performance. The results are shown in Tables 2 and 3 below. Tables 2 and 3 show that, under a UV 300-400 nm light source, the high-temperature resistant organic phosphors prepared in Example 1 and Comparative Example 1 exhibit characteristic emission peaks of 520, 600, and 640 nm, showing an overall down-conversion characteristic; under 980 nm laser excitation, the phosphors exhibit characteristic emission peaks of 520, 540, and 654 nm, showing an overall up-conversion characteristic. This verifies the effectiveness of the Sm phosphors prepared in this invention. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen powder has up-and-down optical conversion properties.

[0080] However, compared to Example 1, the high-temperature resistant organic phosphor of Comparative Example 1 is superior to Sm 0.4 Yb 0.2 Er 0.4 The optical intensity of the (HTTA)3Phen fluorescent material was reduced by about 30%, while the high-temperature resistant organic phosphor prepared in Example 1 of this invention showed a significant improvement over Sm. 0.4 Yb 0.2 Er 0.4The optical intensity of the (HTTA)3Phen fluorescent material is reduced by only about 10%. This means that under ultraviolet excitation, the aerogel fluorescent powder exhibits higher luminescence intensity, while the silica-encapsulated powder shows slightly weaker intensity. This is because the air pores within the aerogel result in less obstruction of light propagation, a lower refractive index (closer to that of air), and thus higher transmittance and luminescence intensity. Furthermore, the fluorescent particles emit light through a transition layer between PMMA and fumed silica, gradually bringing the refractive index closer to that of air, reducing interfacial losses during luminescence and resulting in higher fluorescence intensity. In contrast, the pure silica in Comparative Example 1 has a significantly different refractive index from air, leading to greater interfacial reflection losses.

[0081] Compared to Example 1, the high-temperature resistant organic phosphor in Comparative Example 2 is superior to Sm 0.4 Yb 0.2 Er 0.4 The optical intensity of the (HTTA)3Phen fluorescent material is reduced by about 50%. That is, under ultraviolet light excitation, the luminescence intensity of the phosphor without PMMA coating is lower than that of the phosphor coated with silica. The reasons for this are twofold: firstly, the lack of PMMA coating results in inhomogeneity during the formation of the silica aerogel; secondly, the aerogel silica collapses during the forming process, further leading to inhomogeneity in the coating, resulting in a significant increase in coating thickness and increased interfacial loss during the luminescence process, thus resulting in lower fluorescence intensity.

[0082] Table 2. Downconversion fluorescence intensity of organic phosphors in Example 1, Comparative Example 1, and Comparative Example 2

[0083] (Ultraviolet 300-400 nm light source)

[0084] Example Implementation Example Intensity (cps) Characteristic Wavelength 560nm 600nm 640nm <![CDATA[Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material]]> <![CDATA[0.3×10 5 ]]> <![CDATA[6×10 5 ]]> <![CDATA[1.65×10 6 ]]> Example 1 - Organic Phosphor <![CDATA[0.27×10 5 ]]> <![CDATA[5.5×10 5 ]]> <![CDATA[1.5×10 6 ]]> Comparative Example 1 - Organic Phosphor <![CDATA[0.19×10 5 ]]> <![CDATA[3.8×10 5 ]]> <![CDATA[1.1×10 6 ]]> Comparative Example 2 - Organic Phosphor <![CDATA[0.14×10 5 ]]> <![CDATA[3×10 5 ]]> <![CDATA[0.85×10 6 ]]>

[0085] Table 3. Downconversion fluorescence intensity of organic phosphors in Example 1, Comparative Example 1, and Comparative Example 2

[0086] (980 nm laser)

[0087] Example Implementation Example Intensity (cps) Characteristic Wavelength 520nm 540nm 654nm <![CDATA[Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material]]> <![CDATA[3×10 3 ]]> <![CDATA[7×10 3 ]]> <![CDATA[5×10 3 ]]> Example 1 - Organic Phosphor <![CDATA[2.8×10 3 ]]> <![CDATA[6×10 3 ]]> <![CDATA[4.5×10 3 ]]> Comparative Example 1 - Organic Phosphor <![CDATA[2.1×10 3 ]]> <![CDATA[5×10 3 ]]> <![CDATA[3.5×10 3 ]]> Comparative Example 2 - Organic Phosphor <![CDATA[1.42×10 3 ]]> <![CDATA[3.1×10 3 ]]> <![CDATA[2.5×10 3 ]]>

[0088] Performance Testing 2: Structural Characterization

[0089] The organic phosphors prepared in Example 2 and Comparative Example 2 of the present invention were characterized structurally, and the results are as follows: Figure 1 and Figure 2 As shown. Combined with Figure 1 and Figure 2 It can be seen that, through the analysis of Sm 0.4 Yb 0.2 Er 0.4When (HTTA)3Phen fluorescent materials are encapsulated with silica aerogel to improve their high-temperature resistance, the use of PMMA versus the absence of PMMA pre-encapsulation directly affects whether the silica aerogel layer can uniformly encapsulate the fluorescent material. Figure 1 A uniform coating was formed. Figure 2 This leads to the formation of particle agglomerations.

[0090] The application of organic phosphors is mostly in the processing into products. In order to improve the dispersibility of organic phosphors in subsequent processing, the surface of the above organic phosphors is modified by the following method: Sodium secondary alkyl sulfonate, BYK-190 polyurethane dispersant and BYK-358 acrylic leveling agent are mixed in a mass ratio of (5-7):(3-5):1. Then, they are added to the alcohol solvent of organic phosphors at a ratio of 5-8% of the mass of organic phosphors and stirred for 40-60 minutes to complete the surface modification of the phosphor.

[0091] Performance Test 3: PE Film Haze Test

[0092] The organic phosphors prepared in Example 2 and Comparative Example 2 were used to prepare PE films. The specific preparation methods are as follows:

[0093] (1) Surface modification: Organic phosphor is added to ethanol solution and dispersed evenly to obtain organic phosphor dispersion. Then, sodium secondary alkyl sulfonate, BYK-190 polyurethane dispersant and BYK-358 acrylic leveling agent are mixed evenly in a mass ratio of 5:3:1 to obtain modified solvent. Modified solvent is added to organic phosphor dispersion, and the mass of modified solvent is 8% of organic phosphor. After stirring for 40 min, modified organic phosphor is obtained.

[0094] (2) Film preparation: The modified organic light-converting powder and PE particles are uniformly mixed to obtain a mixture; then the mixture is processed in an extruder at a pressure of 5 MPa, a speed of 150 rpm and a temperature of 180°C to obtain an 80 μm thick agricultural composite PE film.

[0095] The haze of the composite PE films prepared with the organic phosphors of Example 2 and Comparative Example 2 was measured, and the results are shown in Table 4 below.

[0096] Table 4 Optical performance testing of PE films in Example 2 and Comparative Example 2

[0097] Example Haze Example 2 0.8 Comparative Example 2 1.4

[0098] As shown in Table 4, through the analysis of Sm 0.4 Yb 0.2 Er 0.4The (HTTA)3Phen fluorescent material is first encapsulated with PMMA, which can effectively improve the uniformity of the prepared organic phosphor powder, thereby effectively reducing the haze of the prepared PE film and improving the optical performance of the prepared PE film.

[0099] In addition to the above embodiments, the technical effects claimed by the present invention can be achieved by using the preparation process steps and limited process parameters of the present invention, so there is no need to conduct individual tests to verify them.

Claims

1. A high-temperature resistant organic phosphor, characterized in that, The organic phosphor includes Sm, which has up- and down-conversion light-converting functions, coated with polymethyl methacrylate. 0.4 Yb 0.2 Er 0.4 Fluorescent seeds formed from (HTTA)3Phen fluorescent material, and a silica aerogel layer covering the surface of the fluorescent seeds.

2. The high-temperature resistant organic phosphor according to claim 1, characterized in that, The Sm 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material is prepared by the following steps: (1) The contents of Yb 3+ Er 3+ and Sm 3+ A mixture of rare earth metal salts containing ions, α-thiophenecarboxyltrifluoroacetone, and 1,10-phenanthroline are dissolved in ethanol; wherein, in the rare earth metal salt mixture, Yb 3+ Er 3+ and Sm 3+ The molar ratio of the ions is 1:2:2, α-thiophenecarboxyltrifluoroacetone and Yb 3+ Er 3+ and Sm 3+ The total molar ratio of the three is 3:1, and the molar ratio of 1,10-phenanthroline to α-thiophenecarboxylic acid trifluoroacetone is 1:

3. (2) The α-thiophenecarboxyltrifluoroacetone solution was stirred in a water bath at 60-65℃, and a mixture of rare earth metal salts and 1,10-phenanthroline solution was added to prepare a mixed reaction solution; (3) Adjust the pH of the mixed reaction solution to 6-7 and react for 6-7 hours to obtain a precipitate. After washing and drying, obtain Sm. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material.

3. A method for preparing the high-temperature resistant organic phosphor of claim 1, characterized in that, Includes the following steps: (1) Preparation of fluorescent seeds: Methyl methacrylate and Sm are mixed at a mass ratio of 40:(1-2). 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent material was mixed with ethylene glycol di(methacrylate) crosslinking agent (1-3% by mass of methyl methacrylate) and ultrasonically stirred for 3-5 minutes to obtain a mixture. This mixture was then dissolved in ethanol, stirred for 2-4 hours, and centrifuged and dried to obtain PMMA-Sm. 0.4 Yb 0.2 Er 0.4 (HTTA)3Phen fluorescent seeds; (2) Preparation of organic phosphor: Prepare fluorescent seeds, alcohol solvent and water in a mass ratio of 1:(20-35):(8-16); mix alcohol solvent and water evenly, add tetraethyl silicate to prepare sol, the mass ratio of tetraethyl silicate to fluorescent seeds is (1-4):2; add acid catalyst to sol to adjust pH to 3-4, stir at 1000-1600 rpm for 2-4 h to carry out hydrolysis reaction; reduce stirring speed to 300-500 rpm, add alkaline catalyst to adjust pH to 9-10, carry out condensation reaction to obtain wet gel, then add fluorescent seeds to wet gel, stir evenly, age at room temperature for 24-36 h, dry under normal pressure to obtain organic phosphor with silica aerogel layer on surface.

4. The method for preparing high-temperature resistant organic phosphor according to claim 3, characterized in that, The method also includes the following steps: (3) Surface modification: Sodium secondary alkyl sulfonate, BYK-190 polyurethane dispersant and BYK-358 acrylic leveling agent are mixed in a mass ratio of (5-7):(3-5):

1. Then, they are added to the alcohol solvent of the organic phosphor at a ratio of 5-8% of the organic phosphor mass. The surface modification of the phosphor is completed by stirring for 40-60 minutes.

5. The method for preparing high-temperature resistant organic phosphor according to claim 3, characterized in that, In step (2), the alcohol solvent is methanol, ethanol or isopropanol.

6. The method for preparing high-temperature resistant organic phosphor according to claim 3, characterized in that, In step (2), the acid catalyst is citric acid, tartaric acid or acetic acid; the base catalyst is ammonia or sodium hydroxide.

7. The method for preparing high-temperature resistant organic phosphor according to claim 3, characterized in that, In step (2), the atmospheric pressure drying is performed by drying at 70-80℃ for 2-3 hours and at 90-120℃ for 5-7 hours.

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