Molecular self-assembly triplet-triplet annihilation photon up-conversion hydrogel as well as preparation method and application thereof

Abstract

The invention provides a molecular self-assembly triplet-triplet annihilation (TTA) photon up-conversion hydrogel as well as a preparation method and application thereof, a polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) F127 triblock polymer is selected to package an up-conversion dye pair, and a nano-micelle is formed. A hydrophilic segment PEO and a hydrophobic segment PPO of a triblock polymer are self-assembled in an aqueous solution to form nanoparticles, the hydrophilic end is exposed outside to form a compact oxygen barrier shell, and the hydrophobic end and a hydrophobic luminescent material are located at the core, so that quenching by oxygen in air is avoided. And adding an aqueous solution containing the up-conversion nanoparticles into an acrylamide aqueous solution, and directly polymerizing to obtain the up-conversion hydrogel. The strategy is simple to operate, the luminescent material does not need to be subjected to complex modification, the luminescent material does not contain volatile organic solvents, and the polyacrylamide hydrogel has good biocompatibility, so that the polyacrylamide hydrogel has a relatively great application prospect in the field of biology.

Description

Technical Field

[0001] The present application relates to the technical field of organic optoelectronic materials and polymer materials, and more specifically, to a molecular self-assembled triplet-triplet annihilation photon up-conversion hydrogel and a preparation method and application thereof. Background Art

[0002] Photon upconversion based on triplet-triplet annihilation (TTA) is a technology that converts long-wavelength, low-energy photons into short-wavelength, high-energy photons. It has attracted extensive attention from researchers because of its important application value in solar cells, bioimaging, and photocatalysis. Compared with two-photon absorption upconversion and rare earth material upconversion, triplet-triplet annihilation upconversion has the following advantages: (1) It can use ultra-low-intensity, incoherent excitation light that is very close to the intensity of sunlight on the earth's surface as a light source; (2) The sensitizer has a strong absorption of visible light (the molar extinction coefficient is usually higher than 10 4 L·mol －1 cm －1 ); (3) the excitation wavelength and emission wavelength can be adjusted by selecting energy donors and acceptors (energy level matching), and light of different long wavelengths can be converted into high-energy light; (4) the upconversion quantum efficiency is high.

[0003] TTA-UC usually occurs in organic solvents. To date, the most efficient TTA-UC systems are implemented in molecularly dispersed solutions because they allow rapid diffusion of excited state molecules, which is conducive to collisions between molecules and energy transfer. However, excited triplet states are easily quenched by dissolved oxygen in organic solvents. They must be operated under strict anoxic conditions, and organic solvents are volatile, which severely limits the application of excited triplet states. Early TTA-UC studies usually used low-viscosity solutions. However, the triplet energy of TTA-UC in these organic solvents was not solved to be quenched by molecular oxygen, which would lead to a decrease in the overall TTA-UC efficiency. Therefore, research using solid-state TTA-UC materials is very necessary. Chinese patent CN202110887048.9 discloses an organic gel that realizes triplet annihilation photon upconversion in air state, using polyvinyl alcohol octanal as a carrier, and self-assembling with photosensitizer and receptor to form a spiral self-assembled structure in air state. The organic gel realizes triplet annihilation photon upconversion in air state, has high transparency, does not scatter, has a certain shape and mechanical strength at room temperature, can be used as an upconversion carrier, realizes triplet annihilation photon upconversion in air state and at room temperature, and has good repeatability and stability. However, the gel still needs to use an organic solvent, and there are disadvantages such as the solvent is volatile, which greatly limits its application.

[0004] Application Contents

[0005] The technical problem to be solved by the present application is to overcome the difficulty that the existing upconversion gel carrier still needs to use organic solvents, and provide a molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel, through molecular self-assembly, using the hydrophilic and hydrophobic effects of the triblock polymer of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) F127, at low concentrations, the hydrophilic PEO part remains in an expanded state, while the hydrophobic PPO part remains in a contracted state, and the formed hydrophobic core can accommodate lipophilic guests, thereby achieving efficient triplet annihilation upconversion emission under air conditions. Acrylamide can be used as an upconversion carrier, which is not only simple to operate, does not require complex modification of the luminescent material, and does not contain volatile organic solvents, and polyacrylamide hydrogel has good biocompatibility, so it has great application prospects in the biological field.

[0006] Another object of the present application is to provide a method for preparing a molecular self-assembled triplet-triplet annihilation photon up-conversion hydrogel.

[0007] The above-mentioned purpose of this application is achieved through the following technical solutions:

[0008] A molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel, through molecular self-assembly, using the hydrophilic and hydrophobic effects of F127, at low concentrations, its hydrophilic PEO part remains in an expanded state, while the hydrophobic PPO part remains in a contracted state, and the formed hydrophobic core can accommodate lipophilic guests, thereby achieving efficient triplet annihilation upconversion emission under air conditions. Since acrylamide contains carbon-carbon double bonds and amide groups, it has the chemical properties of double bonds: it is easy to polymerize to form a hydrogel under ultraviolet irradiation or at the melting point temperature. Acrylamide is used as a monomer to prepare an organic gel capable of realizing triplet annihilation photon upconversion in air by self-assembly with a porphyrin photosensitizer and a receptor, wherein the molar ratio of the porphyrin photosensitizer, the receptor, acrylamide, the initiator, the crosslinking agent and the catalyst is 67-150:6700-15000:37600-84600:26-60:45-180:8907-20040, and the mass ratio of F127 to the upconversion micelle solution is 1:0.07-0.15.

[0009] Preferably, in step S1, the molar ratio of octaethylporphyrin platinum to 9,10-diphenylanthracene is 1 to 2:150 to 300. More preferably, in step S1, the molar ratio of octaethylporphyrin platinum to 9,10-diphenylanthracene is 1 to 150.

[0010] Preferably, the solvents for the reaction in step S1 are tetrahydrofuran (THF) and methanol.

[0011] Preferably, the reaction temperature in step S1 is 50-75°C and the reaction time is 1-2h; more preferably, the reaction temperature is 60°C and the reaction time is 1h.

[0012] Preferably, the mass ratio of the upconversion dye to F127 in step S2 is 1-2:0.1-0.2. More preferably, the mass ratio of the upconversion dye to F127 in step S2 is 1:0.1.

[0013] Preferably, the solvents for the reaction in step S2 are tetrahydrofuran (THF) and methanol.

[0014] Preferably, the reaction temperature of step S2 is 50-75°C and the reaction time is 1-2h; more preferably, the reaction temperature is 60°C and the reaction time is 1h.

[0015] Preferably, the treatment in step S2 is to remove the organic solvent by rotary evaporation under reduced pressure at a temperature of 50 to 75° C. for 0.5 to 1 h. More preferably, the treatment in step S2 is to remove the organic solvent by rotary evaporation under reduced pressure at a temperature of 60° C. for 0.5 h.

[0016] Preferably, in step S3, the distilled water needs to be preheated in advance and slowly added to the upconversion polymer film.

[0017] More preferably, in step S3, the distilled water needs to be preheated to 60°C in advance.

[0018] Preferably, the reaction temperature in step S3 is 50-75° C. and the reaction time is 0.5-1 h; more preferably, the reaction temperature is 60° C. and the reaction time is 0.5 h.

[0019] Preferably, the rotation speed in step S3 should be 50-150 r / min. More preferably, the rotation speed in step S3 should be 100 r / min.

[0020] Preferably, the reaction conditions in step S3 are as follows: after the hydration is complete and there is no solid film in the bottle, a pink clear upconversion micelle solution can be obtained by filtering using a 0.45 μm water filter.

[0021] Preferably, in step S4, the upconversion micelle solution is 0.5 ml, wherein the molar ratio of Ptoep, DPA and acrylamide is 67-150:6700-15000:37600-84600, to obtain a prepolymerized upconversion micelle solution. More preferably, in step S4, the molar ratio of Ptoep, DPA and acrylamide is 1:100:564.

[0022] Preferably, in step S5, the upconversion micelle solution is prepolymerized, wherein the molar ratio of the content of Ptoep, DPA, acrylamide to BIS, KPS, TEMED is 67-150: 6700-15000: 37600-84600: 26-60: 45-180: 8907-20040. More preferably, in step S5, the upconversion micelle solution is prepolymerized, wherein the molar ratio of the content of Ptoep, DPA, acrylamide to BIS, KPS, TEMED is 100: 10000: 56400: 39: 90: 13360.

[0023] Preferably, the treatment in step S5 to form the upconversion hydrogel should be left to stand for 0 to 60 minutes to allow it to completely solidify. More preferably, the treatment in step S5 to form the upconversion hydrogel should be left to stand for 30 minutes to allow it to completely solidify.

[0024] The molecular self-assembled triplet annihilation photon up-conversion hydrogel prepared by the above-mentioned method is also within the protection scope of the present application.

[0025] At the same time, the preparation process of the compound described in the present application is simple, convenient, and can be prepared in large quantities, which is conducive to factory-based production and preparation, and is conducive to the promotion of its application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The invention relates to a method for preparing the molecular self-assembled triplet annihilation photon up-conversion hydrogel prepared in Example 1.

[0027] Figure 2 This is a photograph of upconversion blue light emission of the molecular self-assembled triplet annihilation photon upconversion micelle aqueous solution prepared in Example 1 after being excited by green light in an air environment.

[0028] Figure 3 (a) is an absorption diagram of the receptor DPA and the photosensitizer octaethylporphyrin platinum in the molecular self-assembled triplet annihilation photon upconversion micelles prepared in Example 1 in F127 micelle aqueous solution and deoxygenated THF; (b) is an emission diagram of the receptor 9,10-diphenylanthracene (DPA) and the photosensitizer octaethylporphyrin platinum (PtOEP) in the molecular self-assembled triplet annihilation photon upconversion micelles prepared in F127 micelle aqueous solution and deoxygenated tetrahydrofuran (THF). The excitation light wavelength is 532nm.

[0029] Figure 4 Absorption and emission spectra of F127 upconversion micelles loaded with (a) DPA and (b) PtOEP embedded in polyacrylamide (PAAM) hydrogel.

[0030] Figure 5(a) Photoluminescence spectra of PAAM upconversion hydrogel under 532 nm light excitation of different powers under air conditions; (b) Dependence of upconversion emission integral on incident power density, with the corresponding straight line slopes being 2.03 and 0.92, respectively; (c) Quantum yield of upconversion hydrogel at room temperature.

[0031] Figure 6 Upconversion emission spectrum of PAAM upconversion hydrogel under air conditions with continuous excitation using a 532nm laser.

[0032] Figure 7 (a), (b), and (c) are cross-sectional scanning electron micrographs of PAAM hydrogels, and (d), (e), and (f) are cross-sectional scanning electron micrographs of PAAM-UCNPs hydrogels.

[0033] Figure 8 (a) The mechanism of upconversion in biological applications. The upconversion emission light is introduced into the target area through optical fiber, thereby reducing the loss of light out of the skin and the loss to the skin. (b) Upconversion fiber total reflection diagram. (c) Green light is introduced into the body through the pork skin layer using upconversion fiber and converted into blue light.

[0034] Fig. 9 Schematic diagram of the PAAM upconversion hydrogel mechanism. DETAILED DESCRIPTION

[0035] The present application is further described in detail below in conjunction with specific examples, which are only used to explain the present application and are not used to limit the scope of the present application. The test methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0036] The applicant has found in research that water-soluble polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO) triblock copolymers are an important class of amphiphilic molecules. The trade name is Pluronics, also known as poloxamer. It is a class of non-ionic surfactant triblock copolymers with different molecular weights. This triblock copolymer often spontaneously forms multi-molecular aggregated micelles in aqueous solution. Its core is mainly composed of hydrophobic PPO blocks, doped with several PEO blocks, and the remaining PEO blocks surround the outer shell. This micelle structure can be well dispersed in aqueous solution. The core with PPO as the main component provides a local hydrophobic microenvironment for the aqueous phase, so it can solubilize oil-soluble compounds. In an aqueous environment, F127 can uniquely self-assemble to form micelles of about 30nm. At low concentrations, its hydrophilic PEO part remains in an expanded state, while the hydrophobic PPO part remains in a contracted state. The hydrophobic core formed can accommodate lipophilic guests. At a concentration of 20% or higher, it can show ideal reversible gel properties as the temperature changes. However, F127 gel is formed by the accumulation and entanglement of micelles when a certain temperature and concentration are reached, so the gel is very sensitive to temperature, has poor mechanical properties, and cannot be processed. Acrylamide contains carbon-carbon double bonds and amide groups, and has the chemical properties of double bonds: under ultraviolet irradiation or at the melting point, it is easy to polymerize to form a hydrogel with good biocompatibility and processability.

[0037] The present application provides a molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel, characterized in that it comprises acrylamide monomer, porphyrin photosensitizer, receptor, crosslinker, initiator and catalyst, wherein the molar ratio of the porphyrin photosensitizer, receptor, acrylamide monomer, crosslinker, initiator and catalyst is (50-200):(5000-20000):(28200-112800):(20-80):(60-135):(6680-26720).

[0038] The hydrogel uses molecular self-assembly and the hydrophilic-hydrophobic interaction of F127. At low concentrations, the hydrophilic PEO part remains in an expanded state, while the hydrophobic PPO part remains in a contracted state. The hydrophobic core formed can accommodate lipophilic guests, thereby achieving efficient triplet annihilation upconversion emission under air conditions. Acrylamide can be used as an upconversion carrier, which is not only simple to operate, but also does not require complex modification of the luminescent material and does not contain volatile organic solvents. Polyacrylamide hydrogel has good biocompatibility, so it has great application prospects in the biological field.

[0039] In some embodiments, the molar ratio of the porphyrin photosensitizer, receptor, acrylamide, crosslinker, initiator, and catalyst is (67-150):(6700-15000):(37600-84600):(26-60):(45-180):(8907-20040).

[0040] In some preferred embodiments, the porphyrin photosensitizer is one or more of octaethylporphyrin platinum, tetraphenylporphyrin platinum, and f-tri(2-phenylpyridyl-N,C2')iridium(III).

[0041] In some preferred embodiments, the acceptor is one or more of 9,10-diphenylanthracene, perylene, and pyrene.

[0042] The present application also provides a method for preparing the above-mentioned molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel, which is characterized by comprising the following steps:

[0043] S1. mixing octaethylporphyrin platinum, 9,10-diphenylanthracene, tetrahydrofuran and methanol to prepare an upconversion dye;

[0044] S2. The upconversion dye prepared in S1 is mixed with F127 to obtain an upconversion polymer;

[0045] S3. The upconversion polymer prepared in S2 is mixed with water to react to obtain an upconversion micelle solution;

[0046] S4. The upconversion micelle solution prepared in S3 is mixed with acrylamide to prepare an upconversion solution;

[0047] S5. Add a crosslinking agent N,N-methylenebisacrylamide, an initiator potassium persulfate, and a catalyst N,N,N',N'-tetramethylethylenediamine to the upconversion solution prepared in S4, and react to obtain a hydrogel to obtain the target product.

[0048] In some preferred embodiments, the molar ratio of octaethylporphyrin platinum and 9,10-diphenylanthracene in step S1 is (1-2):(150-300); the reaction temperature is 50-75° C.; and the reaction time is 1-2 h.

[0049] In some preferred embodiments, the reaction temperature in step S2 is 50-75° C.; the reaction time is 1-2 h; and the mass ratio of the upconversion dye to F127 is (1-2):(0.1-0.2).

[0050] In some preferred embodiments, the reaction temperature in step S3 is 50-75° C. and the reaction time is 0.5-1 h.

[0051] In some preferred embodiments, in step S4, 0.5 ml of the upconversion micelle solution is prepared, wherein the molar ratio of octaethylporphyrin platinum, 9,10-diphenylanthracene and acrylamide is (67-150):(6700-15000):(37600-84600), to obtain a pre-polymerized upconversion micelle solution.

[0052] In some preferred embodiments, in step S5, the upconversion micelle solution is pre-polymerized, wherein the molar ratio of octaethylporphyrin platinum, 9,10-diphenylanthracene, and acrylamide to N,N-methylenebisacrylamide, potassium persulfate, and N,N,N',N'-tetramethylethylenediamine is (67-150):(6700-15000):(37600-84600):(26-60):(45-180):(8907-20040), and the reaction time is 0-1h to obtain a pink transparent polyacrylamide upconversion hydrogel.

[0053] The present application also provides the use of the above-mentioned molecular self-assembled triplet-triplet annihilation photon up-conversion hydrogel in a photoluminescent device.

[0054] Next, the preparation method of the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel in the present application will be introduced in detail.

[0055] Example 1

[0056] Weigh 0.0033g of 9,10-diphenylanthracene (DPA) and 100μL of octaethylporphyrin platinum (PtOEP) upconversion dye in toluene solvent in an eggplant-shaped bottle, add appropriate amount of tetrahydrofuran (THF) and methanol, and heat in an oil bath at 60℃ for 1h to dissolve. Add 1g of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) F127 triblock polymer to the eggplant-shaped bottle while hot, and heat in an oil bath at 60℃ for 1h to dissolve. Then, vacuum rotary evaporation at 60℃ for 30min to remove the organic solvents tetrahydrofuran and methanol, and then obtain an upconversion polymer film. Add an appropriate amount of distilled water preheated at 60°C to the obtained upconversion polymer film, stir in an oil bath at 60°C for more than 30 minutes at a speed of 100 r / min, wait until hydration is complete and there is no solid film in the bottle, and filter using a 0.45 μm water filter to obtain a pink clear upconversion micelle solution.

[0057] Take 100mg N,N-methylenebisacrylamide (BIS) and 250mg potassium persulfate (KPS) in a small glass bottle, add 5.0mL deionized water to each for use (BIS solution concentration 0.013mol / L, KPS solution concentration 0.018mol / L). Take 0.2g acrylamide monomer in a small glass bottle, add 1.0mL deionized water, and stir evenly. Add 15μL BIS solution, 25μL KPS solution, 0.5m of the above-prepared nanomicelle aqueous solution, and then add 10μL N,N,N',N'-tetramethylethylenediamine (TEMED), stir quickly to mix the solution evenly. Inject the liquid into a polytetrafluoroethylene mold and an optical cuvette, and after standing for 30 minutes, a pink transparent polyacrylamide upconversion hydrogel is obtained.

[0058] Characterization and performance testing

[0059] The molecular self-assembly gel prepared in Example 1 was used as the test object to test its photophysical properties and performance. The test results are as follows: Figures 2 to 8 shown.

[0060] Figure 1 The flow chart of the preparation of molecular self-assembled triplet annihilation photon upconversion hydrogel. Take N,N-methylenebisacrylamide (BIS) and potassium persulfate (KPS) in small glass bottles respectively, add deionized water to each for use. Take acrylamide monomer in a small glass bottle, add deionized water, and stir evenly. Add BIS solution, KPS solution, and the nanomicelle aqueous solution prepared above, and then add N,N,N',N'-tetramethylethylenediamine (TEMED), stir quickly to mix the solution evenly. Inject the liquid into a polytetrafluoroethylene mold and an optical cuvette, let it stand, and obtain a pink transparent polyacrylamide upconversion hydrogel.

[0061] Figure 2 This is a photo of the upconversion blue light emission of the molecular self-assembled triplet annihilation photon upconversion micelle aqueous solution after being excited by green light in an air environment. When excited by 532nm excitation light, it is visible to the naked eye that the upconversion dye micelle aqueous solution can produce the upconversion emission measured in the deoxygenated solvent THF without deoxygenation.

[0062] Figure 3(a) is the absorption spectrum of the molecular self-assembled triplet annihilation photon up-conversion micelles measured by Shimadzu UV-2700 UV-visible spectrophotometer. The absorption spectrum of the up-conversion micelle aqueous solution loaded with PtOEP and DPA was tested and compared with the absorption spectrum of PtOEP / DPA in the deoxygenated organic solvent THF. When the same solubility of dye is used in the micelle solution, the absorbance of the up-conversion dye pair decreases compared with the absorbance in the organic solvent THF, and the characteristic structure of the absorption peak of the acceptor DPA disappears. This is because the concentration of aggregated receptors in the micelles is high, forming larger aggregates that do not absorb light. (b) is the emission spectrum of the molecular self-assembled triplet annihilation photon up-conversion micelles obtained by testing the Ocean Optics multifunctional spectrometer at an excitation wavelength of 532nm. When excited with 532nm excitation light, the upconversion dye micelle aqueous solution can produce the upconversion emission measured in the deoxygenated solvent THF without deoxygenation. These results indicate that the nanomicelles formed by F127 self-assembly can be used as a matrix for effective TTA upconversion in air environment.

[0063] Figure 4 The absorption spectrum of molecular self-assembled triplet annihilation photon upconversion micelles measured by Shimadzu UV-2700 UV-visible spectrophotometer. The aqueous solution of F127 nano-micelles was tested separately. Only DPA was loaded and immobilized into hydrogel. Its absorption spectrum showed four obvious (339nm, 356nm, 375nm, 385nm) and one weak (323nm) peaks. The emission spectrum showed a wide emission range of 394nm-532nm, which was consistent with the absorption and emission spectra of DPA in THF ( Figure 4 (a)) and only loaded with PtOEP in PAAM hydrogel, showing two sharp absorption peaks located at 381 nm (Soret absorption band) and 535 nm (Q band), and a sharp phosphorescence emission peak centered at 645 nm ( Figure 4 (b) Spectral characteristics of the solution containing PtOEP are the same as those of THF. The emission behavior of DPA in THF is the same. In summary, the immobilization of the hydrogel has little effect on the absorption and emission of the upconversion dye therein.

[0064] Figure 5 The emission spectrum of the molecular self-assembled triplet annihilation photon upconversion hydrogel obtained by testing the multifunctional spectrometer of Ocean Optics at an excitation wavelength of 532nm. Its emission spectrum clearly shows the upconversion emission of DPA at 434nm. The excitation threshold is an important parameter to measure the TTA-UC process. The PAAM upconversion hydrogel receives 532nm excitation light. By adjusting the intensity of the incident light, the upconversion power dependence of the system is tested, from 3.0mW·cm -2 Low power excitation up to 300mW·cm -2 High power excitation ( Figure 5 (a)), the excitation threshold is 15.2 mW·cm -2 ( Figure 5 (b)). As the incident light power increases, the upconversion emission intensity increases. When it reaches 100mW·cm -2 When , the quantum yield reaches the maximum, which is 10.8%. Figure 5 (c) as shown.

[0065] Figure 6 The air stability of upconversion hydrogel was tested by continuous high-intensity excitation light of 500 mW cm -2 The PAAM upconversion hydrogel was excited for a long time to test its stability under air conditions, and was continuously irradiated for 80 minutes. Although dissolved oxygen molecules can quench some triplet excitons on the surface of the micelles, causing the UC emission intensity to decrease compared to the initial emission intensity, the emission intensity remained above 85% after 80 minutes of high-intensity excitation light irradiation. Since the packaging polymer chains tightly wrap the core of the micelles, oxygen cannot easily diffuse into the micelles. In addition, the PAAM hydrogel supports and protects the micelles, and its intricate network pore structure can also play a certain role in blocking the addition of oxygen. Therefore, it is shown that the micelle and hydrogel structure have a good oxygen-blocking and protective effect on the dye pairs inside, thereby maintaining the stability and air tolerance of the upconversion effect.

[0066] Figure 7 This is a scanning electron microscope image of a hydrogel cross section. The pure upconversion hydrogel without nanomicelles and the upconversion hydrogel with nanomicelles were freeze-dried to maintain their original morphology. They were then frozen and fractured with liquid nitrogen, and their cross-sectional structures were directly photographed using an electron scanning microscope. Figure 7 In (a, b, c), it can be seen that the cross-section of the hydrogel without upconversion nanomicelles is a smooth porous network structure, while the surface of the internal cavity of the hydrogel containing nanomicelles is loaded with many particles, such as Figure 7 (d, e, f), therefore, it is these complex structures that can provide a certain space for the existence of nanomicelles and play the role of isolating oxygen.

[0067] Figure 8 This is the application of the gel in the biological field. Taking advantage of the high transparency and non-toxicity of PAAM upconversion hydrogel, it is made into fiber size, inserted into the skin, and reaches the diseased tissue. (a) The mechanism diagram of upconversion in the biological field, the upconversion emission light is introduced into the target area through the optical fiber, thereby reducing the loss of light out of the skin and the loss to the skin. (b) Upconversion fiber total reflection diagram. (c) Green light is introduced into the body through the pork skin layer using upconversion fiber and converted into blue light.

[0068] Fig. 9 Schematic diagram of the PAAM upconversion hydrogel mechanism. Fig. 9 It can be seen that the upconversion dye pair is encapsulated by the triblock polymer of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) F127 to form nano-micelles. The hydrophilic segment PEO and the hydrophobic segment PPO of the triblock polymer are self-assembled in an aqueous solution to form nanoparticles, with the hydrophilic end exposed to the outside to form a dense oxygen-blocking shell, and the hydrophobic end and the hydrophobic luminescent material at the core to avoid quenching by oxygen in the air. Then, the aqueous solution containing the upconversion nanoparticles is added to the acrylamide aqueous solution for direct polymerization to obtain an upconversion hydrogel.

[0069] The present application provides a molecular self-assembled triplet-triplet annihilation (TTA) photon upconversion hydrogel and its preparation method and application. The triblock polymer of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) F127 is used to encapsulate the upconversion dye pair to form nanomicelles. The hydrophilic segment PEO and the hydrophobic segment PPO of the triblock polymer are self-assembled in an aqueous solution to form nanoparticles. The hydrophilic end is exposed to the outside to form a dense oxygen-blocking shell, and the hydrophobic end and the hydrophobic luminescent material are at the core to avoid quenching by oxygen in the air. The aqueous solution containing the upconversion nanoparticles is then added to the acrylamide aqueous solution and directly polymerized to obtain the upconversion hydrogel. This strategy is not only simple to operate, but also does not require complex modification of the luminescent material and does not contain volatile organic solvents. The polyacrylamide hydrogel has good biocompatibility, so it has great application prospects in the biological field.

[0070] Obviously, the above embodiments of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation methods of the present application. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel, characterized in that: The invention comprises acrylamide monomer, porphyrin photosensitizer, receptor, crosslinking agent, initiator and catalyst, wherein the molar ratio of the porphyrin photosensitizer, receptor, acrylamide monomer, crosslinking agent, initiator and catalyst is (50-200):(5000-20000):(28200-112800):(20-80):(60-135):(6680-26720).

2. The molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 1, characterized in that: The molar ratio of the porphyrin photosensitizer, receptor, acrylamide, crosslinking agent, initiator and catalyst is (67-150):(6700-15000):(37600-84600):(26-60):(45-180):(8907-20040).

3. The molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 1 or 2, characterized in that: The porphyrin photosensitizer is one or more of octaethylporphyrin platinum, tetraphenylporphyrin platinum, and fac-tri(2-phenylpyridyl-N, C2')iridium(III).

4. The molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 1 or 2, characterized in that: The receptor is one or more of 9,10-diphenylanthracene, perylene and pyrene.

5. The method for preparing the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to any one of claims 1 to 4, characterized in that: The steps include: S1. mixing octaethylporphyrin platinum, 9,10-diphenylanthracene, tetrahydrofuran and methanol to prepare an upconversion dye; S2. The upconversion dye prepared in S1 is mixed with F127 to obtain an upconversion polymer; S3. The upconversion polymer prepared in S2 is mixed with water to react to obtain an upconversion micelle solution; S4. The upconversion micelle solution prepared in S3 is mixed with acrylamide to prepare an upconversion solution; S5. Add a crosslinking agent N,N-methylenebisacrylamide, an initiator potassium persulfate, and a catalyst N,N,N',N'-tetramethylethylenediamine to the upconversion solution prepared in S4, and react to obtain a hydrogel to obtain the target product.

6. The method for preparing the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 5, characterized in that: In step S1, the molar ratio of octaethylporphyrin platinum and 9,10-diphenylanthracene is (1-2):(150-300); the reaction temperature is 50-75° C.; and the reaction time is 1-2 h.

7. The method for preparing the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 5, characterized in that: The reaction temperature in step S2 is 50-75° C.; the reaction time is 1-2 hours; and the mass ratio of the up-conversion dye to F127 is (1-2):(0.1-0.2).

8. The method for preparing the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 5, characterized in that: The reaction temperature in step S3 is 50-75° C. and the reaction time is 0.5-1 h.

9. The method for preparing the molecular self-assembled triplet-triplet annihilation photon upconversion hydrogel according to claim 5, characterized in that: In step S4, 0.5 ml of the upconversion micelle solution is prepared, wherein the molar ratio of octaethylporphyrin platinum, 9,10-diphenylanthracene and acrylamide is (67-150):(6700-15000):(37600-84600), to obtain a prepolymerized upconversion micelle solution; and / or In step S5, the upconversion micelle solution is pre-polymerized, wherein the molar ratio of octaethylporphyrin platinum, 9,10-diphenylanthracene, and acrylamide to N,N-methylenebisacrylamide, potassium persulfate, and N,N,N',N'-tetramethylethylenediamine is (67-150):(6700-15000):(37600-84600):(26-60):(45-180):(8907-20040), and the reaction time is 0-1h to obtain a pink transparent polyacrylamide upconversion hydrogel.

10. Use of the molecular self-assembled triplet-triplet annihilation photon up-conversion hydrogel according to any one of claims 1 to 4 in a photoluminescent device.

Images