Multifunctional cellulose-based fluorescent material and preparation method and application thereof

Abstract

The present application belongs to the technical field of high polymer materials, and relates to a multifunctional cellulose-based fluorescent material as well as a preparation method and application thereof. The cellulose-based fluorescent material has a molecular structure shown in the following formula I: wherein a molecular main chain is cellulose, R2 is H or formula II, and x is an integer of 0-2. The molecular main chain of the cellulose-based fluorescent material is cellulose, and the cellulose skeleton contains three types of substituent groups. The first type is a cellulose ester or cellulose ether with R1 structure; the second type is a cellulose carbonate, which endows the cellulose-based fluorescent material with a Fe 3+ fluorescent response performance; and the third type is H on a coumarin or a substituent group as shown in formula II, which can endow the cellulose-based fluorescent material with a response performance and other special performances. Therefore, the multifunctional cellulose-based fluorescent material can simultaneously realize detection of two different target substances, i.e., Fe 3+ and alkaline substances such as biological amines.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of multifunctional application of bio-based materials, and relates to a cellulose-based fluorescent material and a preparation method and application thereof. BACKGROUND

[0002] Fluorescent smart materials can trigger their fluorescence switch based on external stimuli and then convert the stimulus signal into changes in fluorescence signal. Due to its real-time, simple and fast characteristics, it has broad application prospects and economic value. At present, it has been widely used in the fields of optoelectronic materials, biological imaging, food chemistry, environmental monitoring and information encryption.

[0003] Compared with traditional detection methods, although they are sensitive in operation and accurate in results, they have problems such as time-consuming sample processing, complex operation, high cost and the like. In addition, they also need professional equipment and personnel. In this case, since fluorescent smart materials can convert chemical changes into fluorescence signals, especially if the signal is a significant color change, it can be read by widely popularized instruments or untrained personnel. At the same time, the development of bio-based materials to replace petroleum-based products is receiving increasing attention. Cellulose, as the most abundant biorenewable resource on earth, is low in price, has good mechanical and thermal properties, and is biodegradable and biocompatible. Therefore, it is necessary to design and prepare a green, accurate and visual bio-based fluorescent smart sensor using the natural structure of cellulose and its excellent performance to realize rapid detection in common environments.

[0004] Fluorescent smart sensors have high resolution, high sensitivity and high selectivity, and the like. Nawaz et al. (ACS Appl. Mater. Interfaces. 2018; 10(2): 2114-2121) used 4,4'-methylene diphenyl diisocyanate (MDI) as a crosslinking agent to graft 1,10-phenanthroline-5-amine (Phen) on cellulose acetate (CA). When Fe 2+ is encountered, an insoluble red Fe-(Phen-MDI-CA) complex immediately appears. Phen-MDI-CA can be used as a fluorescent sensor for high-selectivity recognition of Fe 2+; Jia et al. (Nat Commun. 2019; 10(1): 1-8) used green fluorescent isothiocyanate with amine response as an indicator group and red fluorescent protoporphyrin IX (containing carboxylic acid functional group) without amine response as an internal standard, fixed them on cellulose acetate respectively, prepared a double-emission cellulose-based fluorescent material by mixing the two fluorescent materials in different proportions. With the decrease of shrimp freshness, the fluorescent color of the intelligent label prepared from the cellulose-based fluorescent material gradually changes from red to yellow and green. According to these studies, we found that most of the current bio-based fluorescent intelligent sensors have single function and can only be used as a tool for detecting one indicator. Compared with single-target response fluorescent sensors, designing multifunctional bio-based fluorescent intelligent sensors has great advantages in reducing analysis time and cost-effectiveness. It has strong practicability and significance to construct multifunctional response fluorescent intelligent materials for real-time monitoring of two or more different analytes. SUMMARY

[0005] The present application aims to solve the problem of single function of existing bio-based fluorescent materials, and provides a multi-response, high grafting rate cellulose-based fluorescent material, a preparation method thereof and applications thereof.

[0006] One object of the present application is to provide a multifunctional cellulose-based fluorescent material, which has a molecular structure as shown in the following formula I:

[0007] wherein the molecular backbone is cellulose, R2 is H or formula II,

[0008] In formula II, x is an integer of 0-2.

[0009] The present application provides a multifunctional cellulose-based fluorescent material, which has a molecular structure as shown in the following formula A:

[0010]

[0011] wherein the molecular backbone is cellulose, and n is an integer of 1-2000.

[0012] The present application also provides a multifunctional cellulose-based fluorescent material, which is obtained by derivatization reaction of formula A and has a molecular structure as shown in the following formula B:

[0013] The molecular backbone is cellulose, n is an integer of 1-2000, and x is an integer of 0-2.

[0014] As preferred, in the above-mentioned formula I, formula A and formula B, R1 is one or more of formula II, formula III, formula IV, formula V, formula VI, formula VII, formula VIII, formula IX:

[0015]

[0016] In formula II, x is an integer from 0 to 16; in formula III, x is an integer from 0 to 2; in the remaining structural formulae, y is an integer from 1 to 1000, and z is an integer from 1 to 1000.

[0017] The present application also provides a preparation method of the multifunctional cellulose-based fluorescent material as described in formula I, comprising the following steps:

[0018] (a) mixing cellulose with an organic base and an organic solvent, and introducing CO2 to obtain a cellulose solution;

[0019] (b) mixing a reaction raw material with the cellulose solution under N2 environment to obtain a cellulose ester or a cellulose ether; the reaction raw material is one or more of an anhydride, an ester, a polyester, a halogenated alkane and an epoxide;

[0020] (c) mixing the cellulose ester or the cellulose ether with 7-hydroxy-4-trifluoromethyl coumarin under CO2 environment to obtain the cellulose-based fluorescent material;

[0021] or further comprising step (d):

[0022] mixing the cellulose-based fluorescent material as described in formula A obtained in step (c) with an anhydride under microwave heating to obtain the cellulose-based fluorescent material as described in formula B.

[0023] The present application also provides a preparation method of the multifunctional cellulose-based fluorescent material as described in formula A, comprising the following steps:

[0024] (a) mixing cellulose with an organic base and an organic solvent, and introducing CO2 to obtain a cellulose solution;

[0025] (b) mixing a reaction raw material with the cellulose solution under N2 environment to obtain a cellulose ester or a cellulose ether; the reaction raw material is one or more of an anhydride, an ester, a polyester, a halogenated alkane and an epoxide;

[0026] (c) mixing the cellulose ester or the cellulose ether with 7-hydroxy-4-trifluoromethyl coumarin under CO2 environment to obtain the cellulose-based fluorescent material.

[0027] The present application also provides a preparation method of the multifunctional cellulose-based fluorescent material as described in formula B, comprising the following steps:

[0028] (a) mixing cellulose with organic base, organic solvent, and passing CO2 to obtain cellulose solution;

[0029] (b) mixing reaction raw material with cellulose solution in N2 environment to obtain cellulose ester or cellulose ether; the reaction raw material is one or more of acid anhydride, lactide, polyester, halogenated alkane and epoxide;

[0030] (c) mixing cellulose ester or cellulose ether with fluorescent raw material in CO2 environment to obtain fluorescent material by reaction;

[0031] (d) mixing fluorescent material with acid anhydride to obtain cellulose-based fluorescent material under the condition of microwave heating.

[0032] The molecular main chain of the cellulose-based fluorescent material is cellulose, and the cellulose skeleton contains three types of substituent groups. The first type is cellulose ester or cellulose ether, which is prepared by reaction of cellulose with one or more of acid anhydride, lactide, polyester, halogenated alkane and epoxide, to obtain R1 structure in the molecular structure, which can endow it with processing performance and be conducive to electrospinning forming; the second type is cellulose carbonate, which is obtained by reaction of cellulose ester or cellulose ether with 7-hydroxy-4-trifluoromethyl coumarin, and the cellulose carbonate bond endows it with Fe 3+ fluorescent response performance; the third type is the substituent group H on coumarin or the molecular structure of formula II, which is obtained by reaction of 7-hydroxy-4-trifluoromethyl coumarin grafted on cellulose derivative with one or more acid anhydrides, which can endow it with response performance and other special performance.

[0033] In the preparation method of the multifunctional cellulose-based fluorescent material described in formula A or formula B, as a preferred, the cellulose in step (a) is cellulose obtained from plant straw, including one or more of microcrystalline cellulose, corn cob cellulose, cotton pulp, wood pulp, bamboo pulp, defatted cotton, and sugarcane residue.

[0034] In the preparation method of the multifunctional cellulose-based fluorescent material described in formula A or formula B, as a preferred, the organic base in step (a) includes one or more of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), tetramethylguanidine (TMG), and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN).

[0035] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, the organic solvent in step (a) includes one or more of dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), N,N-dimethyl imidazolidinone, N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide, N,N-diethyl acetamide, 2-pyrrolidone, 2-azepanone, ε-caprolactam, N,N-dimethyl acryl urea, sulfolane, pentamethylene sulfone, and piperylene sulfone.

[0036] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, the reaction temperature in step (a) is 40-60°C, the reaction time is 1.5-4h, and CO2 is introduced under a pressure of 0.0-5.0 MPa.

[0037] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, in step (a), the mass fraction of cellulose in the cellulose solution is 2-10%.

[0038] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, when R1 is the structure according to Formula II, the reaction raw material in step (b) can be acetic anhydride, propionic anhydride, or butyric anhydride; when R1 is the structure according to Formula III, the reaction raw material in step (b) can be methyl benzoate; when R1 is the structure according to Formula IV, the reaction raw material in step (b) can be glycolide or polyglycolic acid; when R1 is the structure according to Formula V, the reaction raw material in step (b) can be lactide or polylactic acid; when R1 is the structure according to Formula VI, the reaction raw material in step (b) can be ε-caprolactone; when R1 is the structure according to Formula VII, the reaction raw material in step (b) can be σ-valerolactone; when R1 is the structure according to Formula VIII, the reaction raw material in step (b) is polybutylene adipate / terephthalate (PBAT); when R1 is the structure according to Formula IX, the reaction raw material in step (b) can be acrylonitrile; when R1 is the structure according to Formula X, the reaction raw material in step (b) can be bromoethane; and when R1 is the structure according to Formula XI, the reaction raw material in step (b) can be propylene oxide.

[0039] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, the reaction temperature in step (b) is 60-100°C, and the reaction time is 8-16h.

[0040] In the above method for preparing the multifunctional cellulose-based fluorescent material according to Formula A or B, as a preferred, in step (b), the molar ratio of the anhydride, lactide or polyester, haloalkane, and epoxide to the anhydroglucose unit (AGU) of cellulose is 1:(4-16).

[0041] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula A or Formula B, as a preference, in step (b), the degree of substitution (DS) of the cellulose ester or cellulose ether is 0.5 to 3.

[0042] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula A or Formula B, as a preference, in step (c), the reaction temperature is 20 to 40°C, the reaction time is 3 to 6 hours, and the reaction pressure is 0.5 to 1.0 MPa.

[0043] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula A or Formula B, as a preference, in step (c), the molar ratio of the anhydroglucose unit (AGU) of the cellulose to the 7-hydroxy-4-trifluoromethylcoumarin is 1:0.1 to 5.

[0044] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula A or Formula B, as a preference, in step (c), the degree of substitution (DS) of the 7-hydroxy-4-trifluoromethylcoumarin is 0.01 to 0.5.

[0045] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula B, as a preference, in step (d), the anhydride is one or more of acetic anhydride, propionic anhydride, and butyric anhydride.

[0046] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula B, as a preference, in step (d), the reaction temperature of the microwave heating is 60 to 120°C, and the reaction time is 3 to 20 minutes.

[0047] In the above method for producing the multifunctional cellulose-based fluorescent material of Formula B, as a preference, in step (c), the molar ratio of the 7-hydroxy-4-trifluoromethylcoumarin to the anhydride in step (d) is 1:(1 to 5).

[0048] The present application also provides a nanofiber membrane produced by electrospinning from the multifunctional cellulose-based fluorescent material of Formula A or Formula B.

[0049] As a preference, the method for producing the nanofiber membrane comprises the following steps:

[0050] S1, dissolving the cellulose-based fluorescent material of Formula A or Formula B in a mixed solution of N,N-dimethylacetamide and acetone to produce a spinning solution;

[0051] S2, extracting the spinning solution with a syringe and spraying the spinning solution into fine fibers by electric field force, thereby producing a nanofiber membrane on a collector.

[0052] Further preferably, in step S1, the mass ratio of N,N-dimethylacetamide and acetone is 9:1-1:9, and the mass of the cellulose-based fluorescent material is 20-60% of the mass of the mixed solution.

[0053] Further preferably, in step S2, the electrostatic spinning process is performed at a voltage of 16-20 kV, an injection speed of 1-2 mL / h, and a receiving distance of 8-12 cm.

[0054] The application also provides a cellulose-based fluorescent material as shown in Formula A or Formula B for use in fluorescence, wherein the cellulose-based fluorescent material as shown in Formula A exhibits green fluorescence under ultraviolet light;

[0055] Alternatively, the cellulose-based fluorescent material as shown in Formula A exhibits green fluorescence in an atmosphere containing Fe 3+ The fluorescence quenching in the solution disappears, and the fluorescence can be recovered after the cellulose-based fluorescent material is washed in pure water.

[0056] The cellulose-based fluorescent material as shown in Formula B exhibits no fluorescence under ultraviolet light.

[0057] Alternatively, the cellulose-based fluorescent material as shown in Formula B exhibits green fluorescence in an atmosphere containing Fe

[0058] The cellulose-based fluorescent material as shown in Formula A or Formula B exhibits different fluorescence properties, and can be widely applied in different fields according to the different fluorescence properties.

[0059] The application also provides a cellulose-based fluorescent material as shown in Formula A for use in monitoring Fe 3+ -containing solutions.

[0060] The cellulose-based fluorescent material exhibits green fluorescence under ultraviolet light, and the fluorescence quenching in the Fe 3+ -containing solution disappears, and the fluorescence can be recovered after the cellulose-based fluorescent material is washed in pure water. The detection method is to drop the Fe 3+ -containing solution on a product containing the cellulose-based fluorescent material, such as a nanofiber membrane, and selectively identify Fe 3+ according to the fluorescence color change of the nanofiber membrane.

[0061] Preferably, the Fe 3+ -containing solution includes, but is not limited to, a prepared Fe 3+ solution, a water sample containing Fe 3+ , etc.

[0062] Further preferably, the concentration of Fe 3+ in the Fe 3+ -containing solution is greater than or equal to the minimum detection limit of 2.39×10 -6 M.

[0063] The application of a cellulose-based fluorescent material as shown in formula B in detecting alkaline substances, wherein the cellulose-based fluorescent material has no fluorescence under ultraviolet light, and the cellulose-based fluorescent material presents green fluorescence in an alkaline substance atmosphere.

[0064] Preferably, the alkaline substance includes one or more of biological amines, specifically dimethylamine, diethylamine, trimethylamine, triethylamine, histamine, tyramine, beta-phenylethylamine, and ammonia.

[0065] The application also provides the application of a cellulose-based fluorescent material as shown in formula B in detecting alkaline substances, detecting the freshness of aquatic products, detecting water pollution, and information secret transmission.

[0066] The application of a cellulose-based fluorescent material as shown in formula B in detecting the freshness of aquatic products and detecting water pollution.

[0067] The aquatic products include, but are not limited to, shrimp, crab, fish, shellfish, and the like. The detection method is to seal the cellulose-based fluorescent material-containing product, such as a nanofiber membrane, with the aquatic products, and detect the freshness of the aquatic products according to the fluorescence color change of the nanofiber membrane. After the aquatic products rot, biological amines and other alkaline substances are generated, which can destroy the acyl bond in the cellulose-based fluorescent material after contacting with the cellulose-based fluorescent material as shown in formula B, and then make the acyl group fall off. This process is irreversible.

[0068] The application of a cellulose-based fluorescent material as shown in formula B in information secret transmission. Preferably, the cellulose-based fluorescent material as shown in formula B is used to record information and perform decryption protection, and the decryption is performed in an alkaline substance atmosphere. The decryption process is irreversible, the number of decryption times is one and only one, and the decrypted information can be hidden again by Fe 3+ and pure water multiple times. First, based on the fluorescence response of the cellulose-based fluorescent material in an alkaline environment, the information can be decrypted and the decryption process is irreversible, so it can be used as a one-time information transmission tool, and it can also detect whether the information has been decrypted. Second, the information can be hidden again by using the fluorescence response characteristics of the cellulose-based fluorescent material and Fe 3+ . Through the above two ways, complete encrypted information transmission can be realized. The cellulose-based fluorescent material of the application can realize encrypted information transmission through the above two ways, and the decryption can also verify whether the secret information has been decrypted. Furthermore, the information can be hidden and displayed multiple times again as needed.

[0069] Preferably, the alkaline substance includes one or more of biological amines, specifically dimethylamine, diethylamine, trimethylamine, triethylamine, histamine, tyramine, beta-phenylethylamine, and ammonia.

[0070] Compared with the prior art, the present application has the following effects:

[0071] 1. The cellulose-based fluorescent material provided by the present application has a cellulose molecular main chain, and contains three types of substituent groups on the cellulose skeleton, the first type is a cellulose ester or cellulose ether with a R1 structure; the second type is a cellulose carbonate, which endows the cellulose-based fluorescent material with a fluorescence response performance; and the third type is H on a coumarin or a substituent group as shown in formula II, which can endow the cellulose-based fluorescent material with a response performance and other special performances, so that the detection of two different target substances, Fe 3+ and basic substances such as biological amines, can be simultaneously realized. 3+

[0072] 2. The cellulose-based fluorescent material provided by the present application has a wide range of applications, and the nanofiber membrane can be used as a multifunctional fluorescent sensor to realize the dual detection of Fe 3+ and basic substances such as biological amines, and the operation is simpler and the color change is more intuitive.

[0073] 3. The cellulose-based fluorescent material provided by the present application can be used for the detection of the freshness of aquatic products and water pollution, and the detection result is more accurate due to the obvious fluorescence color change, and the detection can be quickly, accurately and normatively realized without the need of instruments and professional personnel, so that the cellulose-based fluorescent material is a new detection method which can be applied in the field of biochemistry.

[0074] 4. The cellulose-based fluorescent material as shown in formula B provided by the present application can detect basic substances such as biological amines, and the detection is based on the fact that the acyl bond on 7-hydroxy-4-trifluoromethyl coumarin can be broken after contacting with basic substances such as biological amines, and this process is irreversible, which further ensures the reliability of the test result, avoids the modification of the test result by improper means, realizes the real-time, visual and more accurate detection of the target substance, and therefore the cellulose-based fluorescent material can be used for information security transmission according to the requirement. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 It is a nuclear magnetic hydrogen spectrum of the cellulose-based fluorescent material as shown in formula A in Example 1;

[0076] Figure 2 It is a nuclear magnetic hydrogen spectrum of the cellulose-based fluorescent material as shown in formula B in Example 8;

[0077] Figure 3 It is a scanning electron microscope image of the nanofiber membrane in Example 10;

[0078] Figure 4 It is a fluorescence response diagram of the nanofiber membrane prepared from the cellulose-based fluorescent material as shown in formula A in Example 12 to different metal ions;

[0079] Figure 5 ​A schematic diagram of the application of the nanofiber membrane prepared from the cellulose-based fluorescent material as shown in Formula B in Example 13 to the freshness detection of aquatic products;

[0080] Figure 6 A process for the information security transmission, decryption, erasing and revealing of the cellulose-based fluorescent material in Example 14. DETAILED DESCRIPTION

[0081] The technical solutions of the present application are further described and illustrated below by specific examples and drawings. It should be understood that the specific examples described herein are only used to help understand the present application and are not used to limit the present application. The drawings used herein are only used to better illustrate the disclosed content of the present application and do not limit the scope of protection. If not otherwise specified, the raw materials used in the examples of the present application are all commonly used raw materials in the art, and the methods used in the examples are all conventional methods in the art.

[0082] Example 1

[0083] The cellulose-based fluorescent material as shown in Formula A is prepared by the following method:

[0084] (a) Microcrystalline cellulose (0.47 g) is mixed with DBU (1.5 g) and DMSO (10 g), CO2 (0.1 MPa) is introduced, and the reaction is carried out at 50°C for 2 h to obtain a uniform transparent cellulose solution;

[0085] (b) Lactide (6.68 g) is mixed with the dissolved cellulose solution, and the reaction is carried out at 80°C for 12 h under N2 environment to obtain a cellulose ester with a degree of substitution of 1.81;

[0086] (c) 7-Hydroxy-4-trifluoromethyl coumarin (1.33 g) is mixed with the obtained cellulose ester, and the reaction is carried out at 30°C for 4 h under CO2 environment, the reaction pressure is 0.8 MPa, and after the reaction is completed, separation and purification are carried out to obtain the cellulose-based fluorescent material as shown in Formula A, wherein the degree of substitution of 7-hydroxy-4-trifluoromethyl coumarin is 0.22.

[0087] Figure 1 A nuclear magnetic resonance hydrogen spectrum of the cellulose-based fluorescent material as shown in Formula A in Example 1. The chemical shift (δ) 3.0-5.5 ppm (O2H, O3H, O6H, H 3.5.6 4 and H2), 5.11 ppm (A'), 4.20 ppm (A), 1.29 ppm (B'), and 1.44 ppm (B). The δ = 6.0-10.5 ppm is the proton in the aromatic ring of 7-hydroxy-4-trifluoromethyl coumarin. The degree of substitution of lactide is 1.81, and the degree of substitution of 7-hydroxy-4-trifluoromethyl coumarin is 0.22.

[0088] Example 2

[0089] The cellulose-based fluorescent material as described in Formula A was prepared by the following method:

[0090] (a) corn cob cellulose (0.47 g) was mixed with DBU (1.5 g) and DMSO (10 g), CO2 was introduced (0.5 MPa), and the mixture was reacted at 50°C for 3 h to obtain a uniform transparent cellulose solution;

[0091] (b) polylactic acid (6.68 g) was mixed with the dissolved cellulose solution, and the mixture was reacted at 100°C for 10 h under N2 to obtain a cellulose ester with a degree of substitution of 1.12;

[0092] (c) 7-hydroxy-4-trifluoromethyl coumarin (1.33 g) was mixed with the obtained cellulose ester, and the mixture was reacted at 40°C for 2 h under CO2 with a reaction pressure of 0.5 MPa. After the reaction, the product was separated and purified to obtain the cellulose-based fluorescent material as described in Formula A, wherein the degree of substitution of 7-hydroxy-4-trifluoromethyl coumarin was 0.14.

[0093] Example 3

[0094] The cellulose-based fluorescent material as described in Formula A was prepared by the following method:

[0095] (a) bamboo pulp (0.35 g) was mixed with TMG (1.5 g) and NMP (10 g), CO2 was introduced (1.0 MPa), and the mixture was reacted at 50°C for 3 h to obtain a uniform transparent cellulose solution;

[0096] (b) methyl benzoate (4.71 g) was mixed with the dissolved cellulose solution, and the mixture was reacted at 90°C for 8 h under N2 to obtain a cellulose ester with a degree of substitution of 1.05.

[0097] (c) 7-hydroxy-4-trifluoromethyl coumarin (0.99 g) was mixed with the obtained cellulose ester, and the mixture was reacted at 45°C for 4 h under CO2 with a reaction pressure of 0.3 MPa. After the reaction, the product was separated and purified to obtain the cellulose-based fluorescent material as described in Formula A, wherein the degree of substitution of 7-hydroxy-4-trifluoromethyl coumarin was 0.07.

[0098] Example 4

[0099] The difference from Example 1 is that in step (c), 7-hydroxy-4-trifluoromethylcoumarin (0.33 g) (AGU / 7-hydroxy-4-trifluoromethylcoumarin = 1 / 0.5) is mixed with the obtained cellulose ester, and reacted in a CO2environment at 30°C for 4 h, the reaction pressure is 0.8 MPa, after the reaction is completed, separation and purification are performed, and the cellulose-based fluorescent material described in Formula A is obtained, the substitution degree of 7-hydroxy-4-trifluoromethylcoumarin is 0.05.

[0100] Example 5

[0101] The difference from Example 1 is that in step (c), 7-hydroxy-4-trifluoromethylcoumarin (0.67 g) (AGU / 7-hydroxy-4-trifluoromethylcoumarin = 1 / 1) is mixed with the obtained cellulose ester, and reacted in a CO2environment at 30°C for 4 h, the reaction pressure is 0.8 MPa, after the reaction is completed, separation and purification are performed, and the cellulose-based fluorescent material described in Formula A is obtained, the substitution degree of 7-hydroxy-4-trifluoromethylcoumarin is 0.13.

[0102] Example 6

[0103] The difference from Example 1 is that in step (c), 7-hydroxy-4-trifluoromethylcoumarin (0.67 g) (AGU / 7-hydroxy-4-trifluoromethylcoumarin = 1 / 3) is mixed with the obtained cellulose ester, and reacted in a CO2environment at 30°C for 4 h, the reaction pressure is 0.8 MPa, after the reaction is completed, separation and purification are performed, and the cellulose-based fluorescent material described in Formula A is obtained, the substitution degree of 7-hydroxy-4-trifluoromethylcoumarin is 0.21.

[0104] Example 7

[0105] The cellulose-based fluorescent material described in Formula A is prepared by the following method:

[0106] The difference from Example 1 is that in step (c), 7-hydroxy-4-trifluoromethylcoumarin (0.67 g) (AGU / 7-hydroxy-4-trifluoromethylcoumarin = 1 / 4) is mixed with the obtained cellulose ester, and reacted in a CO2environment at 30°C for 4 h, the reaction pressure is 0.8 MPa, after the reaction is completed, separation and purification are performed, and the cellulose-based fluorescent material described in Formula A is obtained, the substitution degree of 7-hydroxy-4-trifluoromethylcoumarin is 0.17.

[0107] Example 8

[0108] The cellulose-based fluorescent material described in Formula B is prepared by the following method:

[0109] The difference from Example 1 is that the cellulose-based fluorescent material as described in Formula A (3.9 g) obtained in Example 1 is reacted with acetic anhydride (1.0 g) under the action of microwave-assisted heating at 80°C for 5 min, and after the reaction is completed, the cellulose-based fluorescent material as described in Formula B is obtained by separation and purification, the cellulose ester degree of substitution is 1.81, the 7-hydroxy-4-trifluoromethyl coumarin degree of substitution is 0.22, and the acyl degree of substitution on the 7-hydroxy-4-trifluoromethyl coumarin is 0.09.

[0110] Figure 2 The nuclear magnetic resonance spectrum of hydrogen of the cellulose-based fluorescent material as described in Formula B in Example 8 is shown. The chemical shift (δ) is 3.0-5.5 ppm (O2H, O3H, O6H, H3.5.6, H4 and H2), 5.11 ppm (A'), 4.20 ppm (A), 1.29 ppm (B') and 1.44 ppm (B). The δ = 6.0-10.0 ppm is the proton in the aromatic ring after the 7-hydroxy-4-trifluoromethyl coumarin is acetylated. The δ = 2.4 ppm is the proton in the acetyl group.

[0111] Example 9

[0112] The cellulose-based fluorescent material as described in Formula B is prepared by the following method:

[0113] The difference from Example 1 is that the cellulose-based fluorescent material as described in Formula A (5.9 g) obtained in Example 1 is reacted with acetic anhydride (1.5 g) under the action of microwave-assisted heating at 100°C for 3 min, and after the reaction is completed, the cellulose-based fluorescent material 2 is obtained by separation and purification, the cellulose ester degree of substitution is 1.22, the 7-hydroxy-4-trifluoromethyl coumarin degree of substitution is 0.18, and the acyl degree of substitution on the 7-hydroxy-4-trifluoromethyl coumarin is 0.06.

[0114] Application Example

[0115] Application Example 10: Nanofiber Membrane

[0116] The cellulose-based fluorescent material as shown in Formula A (5.0 g) prepared in Example 1 is mixed with N,N-dimethylacetamide (DMAc) (5 g) and acetone (5 g) to obtain a spinning solution, and a nanofiber membrane is prepared by electrospinning under the conditions of a voltage of 20 kV, an injection speed of 2 mL / h, and a receiving distance of 10 cm.

[0117] Figure 3 The scanning electron microscope image of Example 10 is shown. As can be seen from the figure, the nanofibers therein are uniform in size and exhibit a filamentous structure.

[0118] Application Example 11: Nanofiber Membrane

[0119] The cellulose-based fluorescent material (5.0 g) prepared in Example 8 as shown in Formula B was mixed with N,N-dimethylacetamide (DMAc) (5 g) and acetone (5 g) to obtain a spinning solution. Nanofiber membranes were prepared by electrospinning under the conditions of voltage of 20 kV, injection speed of 2 mL / h and receiving distance of 10 cm.

[0120] Application Example 12: Cellulose-based fluorescent material Fe 3+ response

[0121] The cellulose-based fluorescent material as shown in Formula A obtained in Example 1 was used to prepare a nanofiber membrane; Fe was used to prepare a nanofiber membrane. 3+ A solution of K and other metal ion solutions were dropped onto the nanofiber membrane. These other metal ion solutions included, but were not limited to, K+. + Na + Cd 2+ Ag + Mg 2+ Ca 2+ Hg 2+ Fe 2+ Zn 2+ Al 3+ The fluorescence response of this cellulose-based fluorescent material to different metal ions is as follows: Figure 4 As shown.

[0122] from Figure 4 As can be seen from this, under visible light, only Fe is added. 3+ Subsequently, the nanofiber membrane darkened in color, and only when Fe was dropped in under a 365nm UV lamp did it change color. 3+ The nanofiber membrane exhibited quenching, resulting in black spots. The addition of other ions did not significantly alter the nanofiber membrane's fluorescence intensity under visible light or ultraviolet light.

[0123] Application Example 13: Application in the detection of freshness of aquatic products

[0124] The cellulose-based fluorescent material prepared in Example 8 was made into a nanofiber film, cut into a square of 1x2 cm, and sealed and packaged with 3 parts of prawns, crabs, and abalones, respectively. The film was not fluorescent, indicating freshness, and green, indicating deterioration. As the freshness decreased, the green fluorescence became stronger and stronger. At three different temperatures of 15℃, 5℃, and -18℃, the nanofiber film was placed for 0 days, 1 day, 3 days, 5 days, and 7 days, and the changes in the morphology of the nanofiber film and the changes in the fluorescence color under visible light and ultraviolet light were recorded over time. Meanwhile, the degree of deterioration was characterized according to GB5009.228-2016 "Determination of Volatile Nitrogen in Food" by the semi-micro nitrogen determination method in GB2733-2015 "National Food Safety Standard Fresh and Frozen Animal Aquatic Products". The TVBN deterioration content limit of prawns was 30 mg / 100 g, the TVBN deterioration content limit of crabs was 25 mg / 100 g, and the TVBN deterioration content limit of abalones was 30 mg / 100 g. The test results are shown in Tables 1-3. Figure 5 and Tables 1-3.

[0125] Table 1: Change in TVBN of prawns (unit: mg / 100 g)

[0126]

[0127] Table 2: Change in TVBN of crabs (unit: mg / 100 g)

[0128]

[0129] Table 3: Change in TVBN of abalones (unit: mg / 100 g)

[0130]

[0131] As can be seen from Tables 1-3, the TVBN values of prawns, crabs, and abalones changed. When the TVBN values exceeded the range specified in the "National Food Safety Standard Fresh and Frozen Animal Aquatic Products", the aquatic products were in a state of deterioration. Corresponding to the TVBN measurement values, as the time of placing the aquatic products at different temperatures increased, the fluorescence color of the nanofiber film under the ultraviolet lamp also irreversibly changed from no fluorescence to green. The freshness of the aquatic products can be judged by the color change of the nanofiber film.

[0132] Application Example 14:

[0133] The cellulose-based fluorescent material prepared in Example 8 was printed on the surface of a substrate. Due to the fluorescence quenching effect of the cellulose-based fluorescent material represented by Formula B, the pattern would hide under 365 nm ultraviolet light. The surface of the substrate was washed with water, and the pattern appeared, indicating that the information had been leaked. The Fe 3+The information can be erased and appeared repeatedly by the two reversible processes. The pattern is not appeared when the substrate surface is washed with water, which indicates that the information is not decrypted during the transmission process and the corresponding secret information is not leaked. At this time, the hidden secret information is decrypted and appeared when the substrate surface is washed with alkaline substances such as triethylamine. Then, the information can be erased and hidden again by washing with water. The information secret transmission, decryption, erasing and appearing processes are shown in Fig. 2. 3+ The information can be erased and appeared repeatedly by the two reversible processes. The pattern is not appeared when the substrate surface is washed with water, which indicates that the information is not decrypted during the transmission process and the corresponding secret information is not leaked. At this time, the hidden secret information is decrypted and appeared when the substrate surface is washed with alkaline substances such as triethylamine. Then, the information can be erased and hidden again by washing with water. The information secret transmission, decryption, erasing and appearing processes are shown in Fig. 2. Figure 6

[0134] Aspects, embodiments, features, and advantages of the present application are only illustrative and do not limit the present application, and the scope of the present application is only defined by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed application.

[0135] In the preparation method of the present application, the order of each step is not limited to the listed order, and for those skilled in the art, the order of each step can be changed without creative labor, which is within the protection scope of the present application. In addition, two or more steps or actions can be performed simultaneously.

[0136] Finally, it should be noted that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the embodiments of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, and it is not necessary or possible to fully describe all embodiments. Any obvious changes or variations derived from the essential spirit of the present application are still within the protection scope of the present application, and any additional limitation is contrary to the spirit of the present application.​

Claims

1. A multifunctional cellulose-based fluorescent material, characterized in that, The cellulose-based fluorescent material is obtained from formula A via a derivatization reaction and has the molecular structure shown in formula B below: Formula B, where the molecular backbone is cellulose, n is an integer from 1 to 2000; x is an integer from 0 to 2; Wherein, formula A has the following molecular structure: Formula A, the main molecular chain is cellulose, and n is an integer from 1 to 2000.

2. The multifunctional cellulose-based fluorescent material according to claim 1, characterized in that, R1 is one or more of the formulas shown in Formula II, Formula III, Formula IV, Formula V, Formula VI, Formula VII, Formula IX, Formula X, and Formula XI: In Equation II, x is an integer from 0 to 16; in Equation III, x is an integer from 0 to 2; and in the other structural formulas, y is an integer from 1 to 1000.

3. The method for preparing the multifunctional cellulose-based fluorescent material according to claim 1, characterized in that, Includes the following steps: (a) A cellulose solution is obtained by mixing cellulose with an organic base and an organic solvent and then passing CO2 through the mixture. (b) The reactants are mixed with a cellulose solution and subjected to N2 environment to obtain cellulose ester or cellulose ether; the reactants are one or more of acid anhydrides, lactones, ε-caprolactone, σ-valerolactone, haloalkanes and epoxides; (c) A cellulose ester or cellulose ether is mixed with 7-hydroxy-4-trifluoromethylcoumarin and subjected to CO2 environment to obtain the cellulose-based fluorescent material shown in Formula A; (d) The cellulose-based fluorescent material shown in Formula A is mixed with an acid anhydride and heated under microwave conditions to obtain the cellulose-based fluorescent material shown in Formula B.

4. The method for preparing the multifunctional cellulose-based fluorescent material according to claim 3, characterized in that, In step (b), the molar ratio of the dehydrated glucose unit of cellulose to acid anhydride, lactone, ε-caprolactone, σ-valerolactone, haloalkanes or epoxides is 1:4 to 16. And / or, in step (c), the molar ratio of dehydrated glucose units of cellulose to 7-hydroxy-4-trifluoromethylcoumarin is 1:0.1 to 5; And / or, in step (c), the degree of substitution of 7-hydroxy-4-trifluoromethylcoumarin is 0.01 to 0.5; And / or, in step (d), the microwave heating reaction temperature is 60–120°C and the reaction time is 3–20 min; And / or, the molar ratio of 7-hydroxy-4-trifluoromethylcoumarin in step (c) to the acid anhydride in step (d) is 1:(1-5).

5. A nanofiber membrane, characterized in that, The multifunctional cellulose-based fluorescent material described in claim 1 is prepared by electrospinning.

6. The application of the cellulose-based fluorescent material according to claim 1 in detecting alkaline substances, detecting the freshness of aquatic products, detecting water pollution, or in the secure transmission of information.

7. The application according to claim 6, characterized in that, In the application of detecting alkaline substances, the cellulose-based fluorescent material shown in Formula B exhibits fluorescence quenching under ultraviolet light and no fluorescence phenomenon; the cellulose-based fluorescent material shown in Formula B exhibits green fluorescence in an alkaline atmosphere.

8. The application according to claim 7, characterized in that, Information is recorded and decrypted using the cellulose-based fluorescent material shown in Formula B. Decryption occurs in an alkaline atmosphere; the decryption process is irreversible, and the decryption can only be performed once. The decrypted information is then transmitted via Fe... 3+ The solution was repeatedly wiped clean, and / or the display was repeatedly shown with pure water.

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