Cellulose-based luminescent material as well as preparation method and application thereof

Abstract

The invention relates to a cellulose-based luminescent material as well as a preparation method and application thereof. Comprising the following steps: dissolving cellulose in ionic liquid to form a cellulose solution; dissolving a phosphor and a stabilizer in a cosolvent to form a phosphor solution; the stabilizer is selected from at least one of N, N '-diisopropyl carbodiimide, N, N'-di-tert-butyl carbodiimide, N, N '-diphenyl carbodiimide and N, N'-dicyclohexylcarbodiimide; uniformly mixing the cellulose solution and the phosphorescent agent solution to form a cellulose-based phosphorescent solution; and immersing the cellulose-based phosphorescent solution into a coagulating bath to obtain the cellulose-based luminescent material. The technical problem to be solved is how to provide a cellulose-based luminescent material which has excellent water resistance, high phosphorescence efficiency and long phosphorescence life and can be applied to the fields of information encryption, underwater rescue, ion detection and the like. Meanwhile, the process is simple and convenient, green and environment-friendly, and the prepared cellulose-based luminescent material is multicolor and adjustable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of luminescent material preparation, and particularly relates to a cellulose-based luminescent material and a preparation method and application thereof. BACKGROUND

[0002] Room-Temperature Phosphorescence (RTP) materials are a class of advanced functional materials that can emit long-lived phosphorescence after being excited by light at ambient temperature, and have wide application prospects in the fields of biological imaging, optical sensing, information encryption, flexible display, etc. However, the development of traditional RTP materials faces significant bottlenecks: the phosphorescence emission of the traditional RTP materials usually depends on noble metal complexes or rigid crystal structures, which not only have high costs and are highly toxic to the environment, but also have poor processing formability, making it difficult to meet the needs of large-scale applications. More importantly, most RTP materials are sensitive to water and oxygen environments. In humid or underwater environments, water molecules or oxygen are easy to cause phosphorescence quenching through molecular vibration, solvation, etc., which severely limits their practical application in humid environments such as biomedicine and environmental monitoring.

[0003] To solve the problem that traditional phosphorescent small molecules are difficult to emit phosphorescence at room temperature, researchers have proposed a strategy of embedding phosphorescent molecules into a rigid polymer matrix. On the one hand, the physical constraint of the polymer chain can inhibit the vibration and rotation of the phosphorescent molecules, reduce energy loss, and stabilize the triplet exciton. On the other hand, the dense polymer network can block the penetration of oxygen and water, reducing the probability of exciton quenching. Although this strategy has achieved room-temperature phosphorescence emission, the existing system still has the following technical defects: 1) Most polymer matrices (such as PMMA, PVA) are derived from petroleum-based raw materials, which have environmental problems such as non-degradability and poor sustainability; 2) The method of introducing small molecules into the polymer matrix through copolymerization or chemical grafting has problems such as harsh reaction conditions, complicated steps, poor controllability, and high cost; 3) Although the polymer matrix can short-term isolate water, in long-term high humidity or water-rich environments, the material is easy to cause structure swelling due to water absorption, which in turn causes phosphorescence quenching, making it difficult to meet the weather resistance requirements in actual applications; 4) The existing system is difficult to achieve high phosphorescence efficiency and long phosphorescence lifetime at the same time, and the two are usually mutually restricted due to the difficulty in material microstructure regulation. In addition, although natural polymers represented by cellulose have advantages such as renewability and good biocompatibility, their application in water-resistant phosphorescent materials is still limited by the above problems such as complex preparation process and insufficient water resistance. SUMMARY

[0004] The cellulose-based luminescent material, the preparation method and the application thereof have the advantages that the cellulose-based luminescent material has excellent water resistance, high phosphorescence efficiency and long phosphorescence life, and can be applied to the fields of information encryption, underwater rescue and ion detection; the preparation method is simple, green and environment-friendly; the cellulose-based luminescent material prepared by the method is multicolor adjustable, and thus is more suitable for practical use.

[0005] The technical problems of the present application are solved by the following technical solutions. The present application provides a preparation method of a cellulose-based luminescent material, which comprises the following steps:

[0006] S11, dissolving cellulose in an ionic liquid to form a cellulose solution; dissolving phosphorescent agents and stabilizers in a cosolvent to form a phosphorescent agent solution; the stabilizers are selected from at least one of N,N'-diisopropyl carbodiimide, N,N'-di-tert-butyl carbodiimide, N,N'-diphenyl carbodiimide and N,N'-dicyclohexyl carbodiimide;

[0007] S12, mixing the cellulose solution and the phosphorescent agent solution uniformly to form a cellulose-based phosphorescent solution;

[0008] S13, immersing the cellulose-based phosphorescent solution in a coagulation bath to regenerate the cellulose, so as to obtain the cellulose-based luminescent material.

[0009] The technical problems of the present application are solved by the following technical solutions.

[0010] Preferably, in the preparation method, the cellulose is selected from at least one of dissolving pulp, refined cotton, chemical pulp, filter paper, cotton, cotton thread and microcrystalline cellulose.

[0011] Preferably, in the preparation method, the ionic liquid is selected from at least one of imidazole-based ionic liquid, choline-based ionic liquid and carboxylic acid functionalized imidazole salt; the imidazole-based ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate and 1-allyl-3-methylimidazolium chloride; the choline-based ionic liquid is selected from choline acetate.

[0012] Preferably, in the preparation method, the cellulose is dissolved at 60-100 DEG C under stirring for 10-40 min; and / or, the mass concentration of the cellulose solution is 0.5-10%.

[0013] Preferably, in the preparation method, the cosolvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0014] Preferably, in the cellulose-based phosphor solution prepared by the method, the mass of the phosphor is 0.01-10% of the mass of the cellulose, and the mass of the stabilizer is 1-100% of the mass of the cellulose; and / or the mixing of the cellulose solution and the phosphor solution is stirring at 60-100°C for 5-20 min.

[0015] The cellulose-based luminescent material is prepared according to the method.

[0016] The cellulose-based luminescent material is prepared according to the method.

[0017] The cellulose-based luminescent material is prepared according to the method.

[0018] The cellulose-based luminescent material is prepared according to the method.

[0019] The cellulose-based luminescent material, the preparation method and the application have at least the following advantages:

[0020] The cellulose-based luminescent material, and a preparation method and application thereof, have the advantages of biodegradability and environmental protection, solve the environmental sustainability problem of traditional materials, and use at least one of N,N'-diisopropyl carbodiimide, N,N'-di-tert-butyl carbodiimide, N,N'-diphenyl carbodiimide and N,N'-dicyclohexyl carbodiimide as a stabilizer, and can prepare a room-temperature phosphorescent material with good water resistance and multi-color adjustment through a simple doping method of a small-molecule phosphorescent agent containing an aromatic ring structure, for the first time, the application scene of the cellulose-based luminescent material is expanded to underwater (such as rescue and detection), the inherent defect of poor water resistance of traditional cellulose materials is overcome, a technical blank of a natural polymer-based underwater phosphorescent material is filled, and multi-color adjustable emission and underwater application of the cellulose-based room-temperature phosphorescent material in water are realized; based on the excellent water resistance, the cellulose-based luminescent material is also called a cellulose-based phosphorescent material; compared with a cumbersome copolymerization or chemical grafting process in the prior art, the cellulose-based luminescent material can be prepared through a simple doping-regeneration process, is easy to operate, has high repeatability, and is suitable for large-scale production; the doping method is simple, has high repeatability, and is widely applicable; in the prior art, phosphorescent efficiency and lifetime are often mutually restricted (high efficiency and short lifetime, long lifetime and low efficiency), the cellulose-based luminescent material realizes a balance between the two for the first time in a cellulose-based material through a synergistic design of cellulose rigidity constraint and a stabilizer hydrophobic barrier, and performance indexes are superior to similar reports; the cellulose-based luminescent material prepared in the application can realize high phosphorescent efficiency (36.56%) and long phosphorescent lifetime (723 ms) at the same time; the cellulose-based luminescent material is widely applicable, can realize multiple information encryption applications, can realize specific detection of an iron ion aqueous solution, and can realize rain night, sea or underwater rescue applications.

[0021] The above description is only a summary of the technical scheme of the application, in order to more clearly understand the technical means of the application and to implement the content of the description, the following will be described in detail with reference to the preferred preparation examples of the application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an image of the cellulose dissolution process of Preparation Example 1 of the application under a polarizing microscope;

[0023] Figure 2 is an afterglow image of the cellulose-based room-temperature phosphorescent film of Preparation Example 1 of the application after the ultraviolet excitation is turned off;

[0024] Figure 3a is a phosphorescent emission spectrum of the cellulose-based room-temperature phosphorescent film of Preparation Example 1 of the application;

[0025] Figure 3b is CIE coordinates of the cellulose-based room-temperature phosphorescent film of Preparation Example 1 of the application;

[0026] Figure 3c is the phosphorescence lifetime and quantum yield of the cellulose-based room temperature phosphorescent film of Preparation Example 1 of the present invention;

[0027] Figure 4 is the afterglow image of the cellulose-based room temperature phosphorescent film of Preparation Example 1 of the present invention taken after immersion in water for one month;

[0028] Figure 5 is the afterglow image of the cellulose-based room temperature phosphorescent film of Preparation Example 2 of the present invention taken after turning off the UV excitation;

[0029] Figure 6a is the phosphorescence emission spectrum of the cellulose-based room temperature phosphorescent film of Preparation Example 2 of the present invention;

[0030] Figure 6b is the CIE coordinates of the cellulose-based room temperature phosphorescent film of Preparation Example 2 of the present invention;

[0031] Figure 6c is the phosphorescence lifetime and quantum yield of the cellulose-based room temperature phosphorescent film of Preparation Example 2 of the present invention;

[0032] Figure 7 is the afterglow image of the cellulose-based room temperature phosphorescent film of Preparation Example 2 of the present invention taken after immersion in water for one month;

[0033] Figure 8 is the afterglow image of the cellulose-based room temperature phosphorescent film of Preparation Example 3 of the present invention taken after turning off the UV excitation;

[0034] Figure 9a is the phosphorescence emission spectrum of the cellulose-based room temperature phosphorescent film of Preparation Example 3 of the present invention;

[0035] Figure 9b is the CIE coordinates of the cellulose-based room temperature phosphorescent film of Preparation Example 3 of the present invention;

[0036] Figure 9c is the phosphorescence lifetime and quantum yield of the cellulose-based room temperature phosphorescent film of Preparation Example 3 of the present invention;

[0037] Figure 10 is the afterglow image of the cellulose-based room temperature phosphorescent film of Preparation Example 3 of the present invention taken after immersion in water for one month;

[0038] Figure 11 is the CDBP-based multiple information encryption process in Example 1 of the present invention;

[0039] Figure 12 is the CDBP film detecting iron ion aqueous solution in Example 2 of the present invention;

[0040] Figure 13is the flow chart of wet spinning in Example 3 of the present application and the application of cellulose phosphorescent fiber in rain night or sea rescue;

[0041] Figure 14 is the phosphorescent emission spectrum and afterglow image of CEBP film before and after water immersion in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0042] To further clarify the technical means and effects taken by the present application to achieve the predetermined inventive purpose, the specific embodiments, structures, characteristics and effects of a cellulose-based luminescent material, a preparation method thereof and its application according to the present application are described in detail as follows in combination with the accompanying drawings and preferred preparation examples. In the following description, different "a preparation example" or "preparation examples" do not necessarily refer to the same preparation example. In addition, the specific features, structures or characteristics in one or more preparation examples can be combined in any suitable form.

[0043] The present application provides a preparation method of a cellulose-based luminescent material, which comprises the following steps:

[0044] The first step is solution preparation, including cellulose solution and phosphorescent agent solution, and the order of the two is not fixed; the cellulose solution is prepared as follows:

[0045] The cellulose is dissolved in the ionic liquid to form a cellulose solution.

[0046] The cellulose is a rigid polymer matrix, and the phosphorescent molecules can be embedded therein to achieve high-efficiency room-temperature phosphorescence; the emission mechanism is speculated as follows: the rigid environment can inhibit non-radiative transition, and the physical constraint of the polymer chain can limit the molecular motion of the phosphorescent small molecules, reduce the energy loss caused by vibration / rotation, and thus stabilize the triplet exciton; at the same time, the dense polymer structure can block the penetration of oxygen and moisture in the environment, thereby reducing the probability of exciton quenching.

[0047] The cellulose preferably has a polymer structure connected by glucose units. According to the present application, the cellulose is selected from at least one of dissolving pulp, refined cotton, chemical pulp, filter paper, cotton, cotton thread and microcrystalline cellulose.

[0048] The ionic liquid and the cellulose form hydrogen bonds, which can well destroy the hydrogen bonds within and between the cellulose molecules, so that the ionic liquid can effectively dissolve the cellulose and form a uniform solution. According to the present application, the ionic liquid is at least one selected from imidazole ionic liquid, choline ionic liquid and carboxylic acid functionalized imidazole salt (such as [EMIM][HCOO]); the imidazole ionic liquid is at least one selected from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) and 1-allyl-3-methylimidazolium chloride ([AMIM]Cl); and the choline ionic liquid is choline acetate.

[0049] In order to better dissolve the cellulose and keep the cellulose in a better specification state in the cellulose solution, the temperature and time of cellulose dissolution are preferably controlled. If the dissolution temperature is too low and / or the dissolution time is too short, the cellulose is difficult to dissolve or the dissolution efficiency is low; and if the dissolution temperature is too high and / or the dissolution time is too long, the cellulose is degraded, resulting in that the regenerated cellulose in the subsequent process is a degraded fragment and cannot be processed into a film and / or a silk material. Through a large number of experiments, it is verified that the dissolution of the cellulose in the technical scheme of the present application is preferably stirred for 10-40 min at 60-100℃.

[0050] The concentration of the above-mentioned cellulose solution can be adjusted according to the process needs. Through a large number of experiments, the applicant found that if the concentration of the cellulose solution is too low, the solution viscosity is too low and it is difficult to be processed into a film and / or a silk material; and if the concentration of the cellulose solution is too high, the solution viscosity is too high and it cannot be processed into a shape. In the technical scheme of the present application, the mass concentration of the cellulose solution is preferably 0.5-10%.

[0051] The phosphor solution is prepared as follows: the phosphor and the stabilizer are dissolved in the cosolvent to form a phosphor solution.

[0052] The essence of phosphorescence is the light emission when the molecule jumps from the excited triplet state (T1) to the ground state (S0), which is mainly dependent on the formation and stability of the excited triplet state and the inhibition of non-radiative transition. In the technical solution of the present application, the phosphorescent agent is selected from small molecule phosphorescent materials containing aromatic ring structure. On the one hand, the conjugated π electrons in the aromatic ring can absorb ultraviolet light, which is the premise of producing phosphorescence; on the other hand, the rigid backbone of the aromatic ring can reduce the energy dissipation caused by molecular vibration and rotation, which is conducive to the release of triplet state energy in the form of light emission. Through a large number of experiments, it is verified that the phosphorescent agent of the present application is preferably at least one of biphenyl, naphthalene, phenanthrene, anthracene, pyrene, phenylboronic acid, 4-biphenylboronic acid, 2-naphthaleneboronic acid, 6-methoxy-2-naphthaleneboronic acid, 9-anthraceneboronic acid, 2-anthraceneboronic acid, 9-phenanthreneboronic acid, 1-pyreneboronic acid, 2,2'-biphenyldicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, phenanthrene-9-formic acid, 2-naphthaleneformic acid, 1-naphthaleneformic acid, 1-pyreneformic acid, biphenyldioic anhydride, 1,8-naphthalene dicarboxylic anhydride, 1-phenanthrolic alcohol and 3-methylbiphenyl-2-alcohol; and / or, the co-solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0053] The conjugated system size of different phosphorescent agents is different, resulting in the difference of triplet state energy level, which emits green (504 nm), yellow-green (528 nm) and red (606 nm) phosphorescence in the cellulose matrix respectively, and the multi-color adjustment of phosphorescent materials can be realized by selecting different phosphorescent agents.

[0054] Although the phosphorescent agent can realize short-term isolation of water and oxygen after being combined with polymers such as cellulose, however, in a long-term high humidity or water-rich environment, the material is easy to cause structure swelling due to water absorption, and then cause phosphorescence quenching, such as the loss of luminescent performance of phosphorescent materials under water, the humidity in the process of use and preservation will further cause the phosphorescent performance to decline or even completely lose, which limits the application of phosphorescent materials in high humidity and water conditions. In the present application, a stabilizer with a specific structure is added to the phosphorescent agent solution, which can react with the solvent, such as water, in the subsequent cellulose regeneration process, and form a product with good water resistance in situ; the in-situ precipitated water-resistant product is tightly combined with cellulose and phosphorescent agent through hydrogen bond network and van der Waals non-bonding interaction, forming a hydrophobic barrier in the material, thereby giving the cellulose-based phosphorescent material good water resistance. The present application preferably selects at least one of N,N'-diisopropyl carbodiimide (abbreviated as DIC), N,N'-di-tert-butyl carbodiimide (abbreviated as DTBC), N,N'-diphenyl carbodiimide (abbreviated as DPC) and N,N'-dicyclohexyl carbodiimide (abbreviated as DCC) as the stabilizer; on the one hand, this structure can react with the solvent of the coagulation bath in situ; on the other hand, the product of the in-situ reaction has good water resistance. The in-situ reaction of the stabilizer with the solvent of the coagulation bath is as shown in the following formula:

[0055]

[0056] In the above example, the stabilizer is N,N'-dicyclohexyl carbodiimide (abbreviated as DCC), the coagulation bath solvent is water, and under the process conditions of cellulose regeneration, the carbodiimide structure (-N=C=N-) of DCC reacts with water in situ to generate N,N'-dicyclohexyl urea (DCU); the product is insoluble in water and its structure is not easily destroyed by water when in contact with water, and has a certain water resistance; that is, after cellulose regeneration, a water-insoluble product is formed on the surface of the phosphor material, thereby improving the water resistance of the cellulose-based phosphor material, so that it can be applied to rain, underwater or marine rescue and other application scenarios. Although 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC, also known as EDAC), 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide (CMC) and the like can also react with the coagulation bath solvent, the urea product generated by the reaction of EDC with water contains a polar amino group, which is easy to form a hydrogen bond with water molecules and swell, resulting in a decrease in water resistance; and the DCU product generated by the selected DCC and the like is a non-polar dicyclohexyl structure, which has strong hydrophobicity and is not easy to interact with water, thereby greatly improving the water resistance of the phosphor material.

[0057] By introducing a stabilizer with a specific structure into the system, the present application breaks through the limitation of existing polymer coating that can only resist water for a short period of time, and generates hydrophobic DCU and other products by in-situ reaction of the stabilizer (such as DCC) with water, thereby forming a dual water-resistant structure of "physical constraint + chemical barrier" in the cellulose network, and achieving long-term underwater phosphor stability (still emitting light after 1 month of immersion).

[0058] In order to better dissolve the phosphor and the stabilizer, and considering the good compatibility of the phosphor solution with the cellulose solution in the subsequent process, it is ensured that the cellulose still maintains good solubility when the phosphor solution is mixed with the cellulose solution, and the cellulose is prevented from being regenerated from the solution, the present application preferably uses at least one of N,N-dimethylformamide DMF, N,N-dimethylacetamide DMAc and dimethyl sulfoxide DMSO as a cosolvent.

[0059] The second step is to mix the prepared cellulose solution and the phosphor solution uniformly to form a cellulose-based phosphor solution.

[0060] To ensure the cellulose solution and phosphor solution mixed evenly, the present application preferably under the condition of 60-100 ℃ stirring 5-20 min to make it mixed evenly. If the mixing temperature is too low, it will make the solution viscosity too large, it is difficult to mix it evenly; while the mixing temperature is too high, it will lead to cellulose degradation, and then lead to the material can not be processed into shape. Too short stirring time, can not make it mixed evenly; while the stirring time is too long, it also causes unnecessary cellulose degradation, and then affect its processability and material performance.

[0061] In the cellulose-based water-resistant phosphor solution, the content of phosphor and stabilizer has a great influence on the performance of the phosphor material obtained after solution regeneration.

[0062] To ensure that the phosphor material can produce phosphorescence emission visible to the naked eye, so that it can meet the needs of practical application (such as information encryption, rescue identification), the mass content of phosphor in the cellulose-based phosphor solution of the present application should not be less than 0.01% of cellulose; however, when the concentration of phosphor is too high, the intermolecular distance is shortened, and the concentration quenching effect is easy to occur, which leads to a significant decrease in phosphorescence lifetime and intensity; at the same time, phosphor is usually a small molecule organic matter, excessive addition will destroy the continuity of cellulose matrix, leading to the decrease of material mechanical strength; and high concentration of phosphor may occur in cellulose solution, affecting its uniform dispersion, and reducing the phosphorescence efficiency; through a large number of test verification, the mass content of phosphor in the cellulose-based phosphor solution of the present application should not be higher than 10% of cellulose. In order to better balance the optical performance of phosphor material and concentration quenching effect, the mass content of phosphor is preferably controlled in the range of 0.01-10% of cellulose mass.

[0063] The carbodiimide structure (-N=C=N-) of the stabilizer (such as DCC) in the technical scheme of the present application can activate the hydroxyl of cellulose and the carboxyl of phosphor to form ester bond covalent combination, promote the covalent bond or hydrogen bond combination between phosphor and cellulose, and at the same time, its reaction with water generates DCU, thereby improving the stability and water resistance of phosphor. If the content of stabilizer is too low, it may be difficult to activate the functional groups (such as hydroxyl, carboxyl) on the surface of cellulose or phosphor due to the small amount of stabilizer, which leads to insufficient combination, so that the phosphor is easy to fall off in water; the stabilizer improves the water resistance of the material by crosslinking or surface modification, but excessive addition will lead to the increase of material rigidity and the decrease of flexibility. In addition, there is a synergistic relationship between the concentration of stabilizer and the reaction temperature and time, in the present application, the cellulose solution and the phosphor solution are mixed at 60-100 ℃, and the concentration of 1-100% of stabilizer in this temperature range can ensure that the reaction is completed within a reasonable time (5-20 minutes).

[0064] The present application realizes chemical combination through stabilizer, significantly improves water resistance, and controls the loading amount of phosphor in a reasonable range to avoid quenching.

[0065] Finally, cellulose regeneration is performed, the cellulose-based phosphor solution is immersed in a coagulation bath to regenerate the cellulose, and a cellulose-based luminescent material is obtained.

[0066] In some embodiments of the present application, the cellulose-based water-resistant phosphor solution is coated into a film by a method such as flow casting, blade coating or spin coating, and the wet film is placed in a coagulation bath, such as a water bath, to regenerate the cellulose, and a cellulose luminescent film is obtained.

[0067] In some embodiments of the present application, the cellulose-based water-resistant phosphor solution is obtained by a wet spinning method to obtain a cellulose luminescent fiber.

[0068] Compared with the complicated copolymerization or chemical grafting process in the prior art, the present application can be prepared by a simple doping-regeneration process, is simple to operate, has high repeatability, and is suitable for large-scale production.

[0069] The present application also provides a cellulose-based luminescent material prepared according to the preparation method described above; the cellulose-based luminescent material is a film or a fiber.

[0070] In the phosphor material of the present application, the rigid network of the cellulose matrix fixes the phosphor molecules through hydrogen bonds, limits the rotation / vibration of the phosphor molecules (reduces non-radiative transition), and at the same time, the hydrophobic products such as DCU generated by the reaction of the stabilizer fill the gaps between the cellulose network, block the penetration of water molecules from the inside, and the two cooperate to stabilize the triplet exciton, so that long-life phosphor under water is realized.

[0071] The present application also provides a use of the cellulose-based luminescent material described above in multi-information encryption.

[0072] The present application also provides a use of the cellulose-based luminescent material described above in rain night, underwater or sea rescue.

[0073] The present application also provides a use of the cellulose-based luminescent material described above in specific detection of iron ion aqueous solution.

[0074] The present application will be further described below in combination with specific preparation examples, but it should not be understood as a limitation on the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art to the present application according to the content of the present application described above still belong to the protection scope of the present application.

[0075] Unless otherwise specified, the materials and reagents involved below are commercially available goods well known to those skilled in the art; unless otherwise specified, the methods described are well-known methods in the art. Unless otherwise defined, the technical terms or scientific terms used should be the usual meanings understood by those skilled in the art in the field to which the present application belongs.

[0076] Preparation Example 1

[0077] This preparation example demonstrates the preparation of a green afterglow cellulose-based room temperature phosphorescent thin film. The specific steps are as follows:

[0078] 1) Add 0.1g of dissolving slurry to 20g of AmimCl, heat and stir at 85℃ for 30min to obtain a homogeneous cellulose solution; Figure 1 Images shown under a polarizing microscope depicting the cellulose dissolution process, by Figure 1 As shown, the cellulose fibers that have turned into black areas indicate that the cellulose has completely dissolved.

[0079] 2) Add 0.001g BPA (biphenyl-4,4'-dicarboxylic acid) and 0.01g DCC to 10g DMF to obtain a phosphorescent solution.

[0080] 3) Add the phosphorescent agent solution to the cellulose solution and stir at 85°C for 20 minutes to obtain a cellulose-based phosphorescent solution.

[0081] 4) Pour the cellulose-based phosphorescent solution into a glass petri dish, and then immerse the glass petri dish and the cellulose-based phosphorescent solution together in water for regeneration.

[0082] 5) Wash repeatedly with deionized water and dry to obtain a green afterglow cellulose-based room temperature phosphorescent film (CDBP).

[0083] Appendix Figure 2 The image shows the afterglow of the phosphorescent film prepared in this example after the ultraviolet excitation was turned off. As can be seen from the figure, the phosphorescent film can be observed to have a green afterglow of about 2 seconds after the ultraviolet lamp was turned off.

[0084] Appendix Figure 3a The phosphorescence emission spectrum of the phosphorescent thin film prepared in this example is attached. Figure 3b The CIE coordinates of the phosphorescent thin film prepared in this example are attached. Figure 3c The phosphorescence lifetime and quantum yield of the phosphorescent thin film prepared in this example are determined by... Figure 3a It can be seen that the maximum phosphorescence emission peak of the phosphorescent thin film is located at 504 nm; Figure 3b As can be seen, the CIE coordinates of the phosphorescent film are located at (0.218, 0.458), which verifies that the phosphorescent film can emit a green afterglow; Figure 3c It can be seen that the phosphorescence lifetime (τ) and phosphorescence quantum yield (ФPh) of the phosphorescent film are 303 ms and 4.19%, respectively.

[0085] Appendix Figure 4The afterglow image of the phosphorescent film of the present preparation example after soaking in water for one month is shown in the figure. It can be seen from the figure that the phosphorescent film can still emit green afterglow after soaking in water for one month, indicating that it has good water resistance and can be applied in underwater environment.

[0086] Preparation Example 2

[0087] A yellow-green afterglow cellulose-based room temperature phosphorescent film was prepared in the present preparation example, and the specific steps are as follows:

[0088] 1) 0.2 g of refined cotton was added to 20 g of BmimCl, and heated and stirred at 90°C for 30 min to obtain a uniform cellulose solution.

[0089] 2) 0.004 g of PHA (phenanthrene-9-carboxylic acid) and 0.05 g of DCC were added to 10 g of DMSO to obtain a phosphorescent agent solution.

[0090] 3) The phosphorescent agent solution was added to the cellulose solution, and stirred at 90°C for 15 min to obtain a cellulose-based phosphorescent solution.

[0091] 4) The cellulose-based phosphorescent solution was poured into a glass culture dish, and then the glass culture dish was soaked in water together with the cellulose-based phosphorescent solution for regeneration.

[0092] 5) Washed with deionized water for several times, dried to obtain a yellow-green afterglow cellulose-based phosphorescent film (CDPH).

[0093] Figure 1 Figure 5 The afterglow image of the phosphorescent film of the present preparation example after the ultraviolet excitation was turned off is shown in the figure. It can be seen from the figure that about 3s of yellow-green afterglow can be observed after the ultraviolet lamp was turned off.

[0094] Figure 2 Figure 6a The phosphorescent emission spectrum of the phosphorescent film of the present preparation example is shown in the figure. Figure 6b The CIE coordinates of the phosphorescent film of the present preparation example are shown in the figure. Figure 6c The phosphorescent lifetime and quantum yield of the phosphorescent film of the present preparation example are shown in the figure. Figure 6a It can be seen that the maximum phosphorescent emission peak of the phosphorescent film is located at 528 nm. Figure 6b It can be seen that the CIE coordinates of the phosphorescent film are located at (0.310, 0.530), which verifies that the phosphorescent film can emit yellow-green afterglow. Figure 6c It can be seen that the phosphorescent lifetime (τ) and phosphorescent quantum yield (ФPh) of the phosphorescent film are 723 ms and 36.56%, respectively, indicating that it maintains a balance between high phosphorescent efficiency and long lifetime.

[0095] Figure 3 Figure 7The afterglow image of the phosphorescent film of the present preparation example after soaking in water for one month is shown in the figure. As can be seen from the figure, the phosphorescent film can still emit yellow-green afterglow after soaking in water for one month, indicating that it has good water resistance and can be applied in underwater environment.

[0096] Preparation Example 3

[0097] A red afterglow cellulose-based room temperature phosphorescent film was prepared in the present preparation example, and the specific steps are as follows:

[0098] 1) 0.2 g of chemical pulp was added to 20 g of AmimCl, and heated and stirred at 80°C for 30 min to obtain a uniform cellulose solution.

[0099] 2) 0.002 g of PYA (1-pyrene carboxylic acid) and 0.02 g of DCC were added to 10 g of DMSO to obtain a phosphorescent agent solution.

[0100] 3) The phosphorescent agent solution was added to the cellulose solution, and stirred at 80°C for 20 min to obtain a cellulose-based phosphorescent solution.

[0101] 4) The cellulose-based phosphorescent solution was poured into a glass culture dish, and then the glass culture dish was soaked in water together with the cellulose-based phosphorescent solution for regeneration.

[0102] 5) Washed with deionized water for several times, dried to obtain a red afterglow cellulose-based phosphorescent film (CDPY).

[0103] Figure 1 Figure 8 The afterglow image of the phosphorescent film of the present preparation example after the ultraviolet excitation was turned off is shown in the figure. As can be seen from the figure, the phosphorescent film can emit red afterglow for about 333 ms after the ultraviolet lamp was turned off.

[0104] Figure 2 Figure 9a The phosphorescent emission spectrum of the phosphorescent film of the present preparation example is shown in the figure. Figure 9b The CIE coordinates of the phosphorescent film of the present preparation example are shown in the figure. Figure 9c The phosphorescent lifetime and quantum yield of the phosphorescent film of the present preparation example are shown in the figure. Figure 9a As can be seen, the maximum phosphorescent emission peak of the phosphorescent film is located at 606 nm. Figure 9b As can be seen, the CIE coordinates of the phosphorescent film are located at (0.485, 0.432), which verifies that the phosphorescent film can emit red afterglow. Figure 9c As can be seen, the phosphorescent lifetime (τ) and phosphorescent quantum yield (ФPh) of the phosphorescent film are 307 ms and 2.85%, respectively.

[0105] Figure 3 Figure 10The afterglow image of the phosphorescent film of the present preparation example after soaking in water for one month is shown in the figure. It can be seen from the figure that the phosphorescent film still emits red afterglow after soaking in water for one month, indicating that it has good water resistance and can be applied in underwater environment.

[0106] Preparation Example 4

[0107] 0.1 g of microcrystalline cellulose was dissolved in 20 g of [EMIM]OAc, stirred at 85°C for 30 min; 0.00001 g of 4-biphenylboronic acid and 0.001 g of DCC were dissolved in 10 g of DMF; after mixing, stirred at 85°C for 20 min, and a film was regenerated. The phosphorescent lifetime of the film was 280 ms, the quantum yield was 3.5%, and it still emitted light after soaking in water for 1 month.

[0108] Preparation Example 5

[0109] 0.1 g of refined cotton was added to 20 g of [BMIM]Cl, and a cellulose solution was obtained by stirring at 90°C for 30 min; 0.01 g of 1-pyreneboronic acid and 0.1 g of DCC were dissolved in 10 g of DMSO to obtain a phosphorescent agent solution; after mixing, the mixture was stirred at 90°C for 15 min, and a film was regenerated. The phosphorescent lifetime of the film was 280 ms, the quantum yield was 2.9%, and the phosphorescent intensity retention rate was 75% after soaking in water for 1 month.

[0110] Example 1

[0111] Using the water resistance of the CDBP film in Preparation Example 1 and the non-light-emitting property of fiber paper, and the underwater quenching property of the CEBP film in Comparative Example 1, a programmable information encryption array was constructed, and dynamic multiple information encryption was realized by using the water-controllable phosphorescent property, as shown in the following Figure 11 .

[0112] Example 2

[0113] The CDBP film was soaked in a metal ion solution, and the room temperature phosphorescence of the CDBP film was quenched by iron ions, realizing selective detection of iron ions, as shown in the following Figure 12 .

[0114] Example 3

[0115] The cellulose-based phosphorescent solution obtained in steps 1) to 3) of Preparation Example 2 was subjected to wet spinning to obtain cellulose phosphorescent fibers; and the phosphorescent fibers were patterned to obtain a phosphorescent fabric. The phosphorescent lifetime of the phosphorescent fabric was 500-600 ms, the quantum yield was 30-35%, and the phosphorescent intensity was maintained at more than 80% after soaking in water for 1 month, and the phosphorescent fabric could emit bright phosphorescence in water and on rainy nights, thereby realizing rescue in rainy nights and underwater, as shown in the following Figure 13 The flowchart of wet spinning and the application of cellulose phosphorescent fibers to rescue in rainy nights or at sea are shown in the following.

[0116] Comparative Example 1

[0117] The same as Preparation 1, except that DCC was not added. The phosphorescent film CEBP prepared in this preparation emits green phosphorescence as well, but the phosphorescence is quenched under water.

[0118] Comparative Example 2

[0119] Preparation of green afterglow water-quenched cellulose-based room-temperature phosphorescent film: 0.1 g of dissolving pulp was added to 20 g of AmimCl and heated and stirred at 85°C for 30 min to obtain a uniform cellulose solution; then 0.001 g of BPA was added to 10 g of DMF to obtain a phosphorescent small molecule solution, which was then added to the above cellulose solution, and the mixture was continuously stirred at 85°C for 20 min to obtain a cellulose-based phosphorescent solution. Then the solution was poured into a glass culture dish, and then soaked in water for regeneration, washed with deionized water several times and dried to obtain a water-quenched green cellulose-based phosphorescent film (CEBP).

[0120] Figure 14 It was found that the green phosphorescence of the phosphorescent film was observed after the ultraviolet lamp was turned off; its emission spectrum was consistent with that of CDBP. However, the green phosphorescence of CEBP disappeared after soaking in water, and the intensity of its phosphorescent emission spectrum dropped sharply.

[0121] The technical features in the claims and / or the specification of the present application can be combined, and the combination manner is not limited to the combination obtained by reference in the claims. The technical solutions obtained by combining the technical features in the claims and / or the specification are also within the protection scope of the present application.

[0122] The above is only a preferred preparation example of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made to the above preparation example according to the technical essence of the present application are still within the scope of the technical solutions of the present application.

Claims

1. A method for preparing a cellulose-based luminescent material, characterized in that, It includes the following steps: S11 dissolves cellulose in an ionic liquid to form a cellulose solution; dissolves a phosphorescent agent and a stabilizer in a co-solvent to form a phosphorescent agent solution; the stabilizer is selected from at least one of N,N'-diisopropylcarbodiimide, N,N'-di-tert-butylcarbodiimide, N,N'-diphenylcarbodiimide and N,N'-dicyclohexylcarbodiimide; S12 mixes the cellulose solution and the phosphorescent agent solution evenly to form a cellulose-based phosphorescent solution; S13 involves immersing a cellulose-based phosphorescent solution in a coagulation bath to regenerate the cellulose, thereby obtaining a cellulose-based luminescent material.

2. The preparation method according to claim 1, characterized in that, The cellulose is selected from at least one of dissolving pulp, refined cotton, chemical pulp, filter paper, cotton, cotton thread, and microcrystalline cellulose.

3. The preparation method according to claim 1, characterized in that, The ionic liquid is selected from at least one of imidazole ionic liquids, choline ionic liquids, and carboxylic acid-functionalized imidazole salts; the imidazole ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium acetate, and 1-allyl-3-methylimidazolium chloride; the choline ionic liquid is selected from choline acetate.

4. The preparation method according to claim 1, characterized in that, The cellulose is dissolved by stirring at 60–100°C for 10–40 min; and / or the mass concentration of the cellulose solution is 0.5–10%.

5. The preparation method according to claim 1, characterized in that, The co-solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

6. The preparation method according to claim 1, characterized in that, In the cellulose-based phosphorescent solution, the phosphorescent agent is 0.01-10% of the cellulose mass, and the stabilizer is 1-100% of the cellulose mass; and / or, the cellulose solution and the phosphorescent agent solution are mixed by stirring at 60-100°C for 5-20 minutes.

7. A cellulose-based luminescent material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6; the cellulose-based luminescent material is a thin film or fiber.

8. The application of the cellulose-based luminescent material according to claim 7 in multi-layered information encryption.

9. The application of the cellulose-based luminescent material according to claim 7 in rainy nights, underwater or maritime rescue.

10. The application of the cellulose-based luminescent material according to claim 7 in the specific detection of iron ions in aqueous solution.

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