Cellulose-based fluorescent material with large Stokes shift as well as preparation method and application of cellulose-based fluorescent material

Abstract

The invention discloses a cellulose-based fluorescent material with large Stokes shift as well as a preparation method and application thereof, and belongs to the technical field of functional polymer materials. The preparation method comprises the following steps: drying microcrystalline cellulose, adding anhydrous N, N-dimethylacetamide in a nitrogen atmosphere for reaction, cooling the reaction liquid to room temperature, adding anhydrous lithium chloride in the nitrogen atmosphere, and fully dissolving the microcrystalline cellulose to obtain a system in which the microcrystalline cellulose is completely dissolved; the preparation method comprises the following steps: heating a system, adding pyridine in a nitrogen atmosphere, cooling, sequentially adding benzofuran-2-carboxylic acid, 4-dimethylaminopyridine and N, N '-diisopropylcarbodiimide in the nitrogen atmosphere, and stirring for reaction to obtain a reaction mixture; adding the reaction mixture into a methanol solution, stirring, standing, taking out a precipitate, washing and drying to obtain cellulose-tri (2-benzofuran formate), namely the cellulose-based fluorescent material.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer materials, and in particular relates to a cellulose-based fluorescent material with a large Stokes shift, a preparation method and an application thereof. Background Art

[0002] Cellulose derivatives have outstanding applications in the field of chiral materials, especially as chiral stationary phase materials. Among them, cellulose phenyl carbamate chiral stationary phase materials have excellent chiral recognition ability and can effectively separate more than 90% of racemates. Although great progress has been made in the field of chiral stationary phase materials, research on cellulose derivatives in other functional materials still needs to be developed. The development of new optical materials based on cellulose as a matrix material has attracted the interest of researchers in recent years. Introducing large-volume conjugated products with new fluorescent structures into the cellulose backbone to construct new luminescent materials has been proven to be a feasible means. It is of great significance to expand the functional application of cellulose derivatives.

[0003] The Stokes shift of most fluorescent materials (such as fluorescein, rhodamine, oxazine and anthocyanin) is very small (generally <30nm), which leads to serious crosstalk between the excitation spectrum and the emission spectrum. In addition, fluorescent materials with small Stokes shift have problems such as decreased sensitivity and fluorescence quenching due to the self-absorption of molecules, which greatly limits their application in fluorescence sensing, optical imaging and other fields. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a cellulose-based fluorescent material with a large Stokes shift, a preparation method and an application, thereby solving the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a cellulose-based fluorescent material with a large Stokes shift comprises the following steps:

[0007] S1, after drying the microcrystalline cellulose, adding anhydrous N,N-dimethylacetamide to react under a nitrogen atmosphere, then cooling the reaction solution to room temperature, adding anhydrous lithium chloride under a nitrogen atmosphere to allow the microcrystalline cellulose to fully dissolve, thereby obtaining a system in which the microcrystalline cellulose is completely dissolved;

[0008] S2, heating the system, then adding pyridine under a nitrogen atmosphere, then cooling the system, and sequentially adding benzofuran-2-carboxylic acid, 4-dimethylaminopyridine, and N,N'-diisopropylcarbodiimide under a nitrogen atmosphere, stirring to react, and obtaining a reaction mixture;

[0009] S3, adding the reaction mixture into a methanol solution and stirring, then letting it stand, taking out the precipitate, washing and drying it to obtain cellulose tris(2-benzofurancarboxylate), i.e., a cellulose-based fluorescent material.

[0010] Further, the synthetic route of cellulose-tri(2-benzofurancarboxylate) is:

[0011]

[0012] Furthermore, in S1, the drying of the microcrystalline cellulose is carried out in an oil bath system at 80°C.

[0013] Furthermore, in S2, the temperature of the system after heating is 80°C.

[0014] Further, in S2, the temperature of the system after cooling is 30°C

[0015] Further, in S3, the precipitate is washed by centrifugation with a methanol solution.

[0016] Furthermore, in S3, the drying process is vacuum drying for 12 hours.

[0017] The cellulose-based fluorescent material with a large Stokes shift is prepared using the above-mentioned method for preparing the cellulose-based fluorescent material with a large Stokes shift.

[0018] Application of the above-mentioned cellulose-based fluorescent material with large Stokes shift in the preparation of fluorescent probes or fluorescent sensors.

[0019] A fluorescent probe comprises the above-mentioned cellulose-based fluorescent material with large Stokes shift.

[0020] Beneficial effects of the present invention:

[0021] The present invention expands the application of cellulose derivatives in the field of luminescent materials. A new cellulose-based fluorescent material is synthesized by Steglich esterification reaction using microcrystalline cellulose and benzothiophene-2-carboxylic acid. This type of cellulose-based fluorescent material exhibits a large Stokes shift and has great application prospects in optical fields such as fluorescent probes, fluorescent sensors, and fluorescent imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1It is a synthetic route for cellulose-tris(2-benzofurancarboxylate);

[0024] Figure 2 is the FT-IR spectrum of cellulose-tri(2-benzofurancarboxylate);

[0025] Figure 3 Cellulose tris(2-benzofurancarboxylate) 1 HNMR spectrum;

[0026] Figure 4 is the UV absorption spectrum of cellulose tris(2-benzofuranate);

[0027] Figure 5 These are the fluorescence excitation and emission spectra of cellulose tris(2-benzofuranate). DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The sources of raw materials used in the examples are as follows:

[0030] Microcrystalline cellulose: cas: 9004-34-6, brand: Anaiji; manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0031] Anhydrous N,N-dimethylacetamide: cas: 127-19-5, brand: Anaiji, manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0032] Anhydrous lithium chloride: cas: 7447-41-8, brand: 3AMaterials, manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0033] Pyridine: cas: 110-86-1, brand: Anaiji, manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0034] Benzofuran-2-carboxylic acid: cas: 496-41-3, brand: Aladdin, manufacturer: Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0035] 4-Dimethylaminopyridine: cas: 1122-58-3, brand: Anaiji, manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0036] N,N'-diisopropylcarbodiimide: cas: 693-13-0, brand: Anaiji, manufacturer: Anhui Zesheng Technology Co., Ltd.;

[0037] Methanol: cas: 67-56-1, brand: Anaiji, manufacturer: Anhui Zesheng Technology Co., Ltd.

[0038] Example 1

[0039] like Figure 1 As shown, the preparation method of the cellulose-based fluorescent material with a large Stokes shift comprises the following steps:

[0040] S1, take 0.2g of microcrystalline cellulose, place it in a two-necked bottle and vacuum dry it for more than 4h, and the drying process is carried out in an oil bath system at 80°C; after the microcrystalline cellulose is fully dried, 8mL of anhydrous N,N-dimethylacetamide is added under the protection of a nitrogen atmosphere to react for 12h; then the reaction solution is cooled to room temperature, and 0.4g of anhydrous lithium chloride is added under a nitrogen atmosphere. After reacting for 2h, the microcrystalline cellulose is fully dissolved until the system becomes clear and transparent;

[0041] S2, in the system where the microcrystalline cellulose is completely dissolved, the system is heated to 80°C, and then 14 mL of pyridine is added to the system under the protection of a nitrogen atmosphere. After 4 hours, the system is cooled to 30°C, and then 1.2 g of benzothiophene-2-carboxylic acid, 1.81 g of 4-dimethylaminopyridine and 1.9 mL of N,N'-diisopropylcarbodiimide are added to the system in sequence under the protection of a nitrogen atmosphere. The reaction is stirred for 48 hours and then stopped.

[0042] S3, the reaction mixture was added dropwise into 250 mL of methanol solution and the stirring was continued for 30 min. After the stirring was completed, the mixture was allowed to stand for more than 12 h until all the precipitates were settled at the bottom of the beaker. The supernatant was then removed, and the remaining precipitates were washed by centrifugation with pure methanol solution for more than 7 times. Finally, the washed product was vacuum dried for more than 12 h to obtain pure cellulose tris(2-benzofurancarboxylate) with a yield of 63.5%.

[0043] Example 2

[0044] In this example, the cellulose tris(2-benzofurancarboxylate) prepared in Example 1 was tested and verified;

[0045] 1) FT-IR spectrum of cellulose tris(2-benzofuranate)

[0046] First, take an appropriate amount of solid KBr, grind it into powder, and use a tablet press to press the KBr into small flakes (note that the pressure of the tablet press should not exceed 15Mpa) as the test background, then mix cellulose-tri(2-benzofurancarboxylate) and treated potassium bromide at a mass ratio of 1:100, grind them evenly, and use a tablet press to press them into flakes as Fourier transform infrared (FT-IR) spectrum test samples;

[0047] The test results are as follows Figure 2 As shown in the figure, it can be seen that the cellulose derivative has a wavelength of 1750 cm -1 Around 1561 cm, a strong characteristic absorption peak appears, which is the characteristic stretching vibration peak of -C=O in the structure of benzofuran ester; -1 At 1230 cm -1 and 1080cm -1 There is a strong characteristic absorption peak on the left and right, which is the -CO stretching vibration peak; in the fingerprint region 745cm -1 The out-of-plane bending vibration of -CH on the benzene ring appears. From the figure, it can be preliminarily determined that the synthesized derivatives meet the expected target.

[0048] 2) Test of cellulose tris(2-benzofuranate) 1 HNMR spectrum;

[0049] Take 10 mg of cellulose tris (2-benzofuranate) and dissolve it in 600 μL deuterated dimethyl sulfoxide for H NMR spectrum ( 1 H NMR) test samples;

[0050] The test results are as follows Figure 3 As shown in the figure, it can be seen that from low field to high field, the attribution of each proton resonance peak is as follows (500Hz, ppm, DMSO, 80℃): 8.04~6.48ppm is benzofuran-H (15H), 5.82~3.52ppm is glucose unit-H (7H). Among them, δ=3.21 and 3.04ppm are methanol solvent peaks, δ=3.92ppm is H2O solvent peak, and δ=2.50ppm is the solvent peak of deuterated reagent DMSO. The above results show that the structure of the synthesized derivative is regular and meets the expected synthetic structure target.

[0051] 3) Testing the UV absorption spectrum of cellulose tris(2-benzofurancarboxylate);

[0052] Take an appropriate amount of cellulose tris(2-benzofuranate) and dissolve it in N,N-dimethylacetamide to prepare a concentration of 1.0×10 -4 M was then measured using wavelength scanning mode at room temperature.

[0053] The test results are as follows Figure 4 As shown in the figure, it can be seen that the maximum absorption wavelength of the derivative is 293nm. The molar absorption coefficient ε of cellulose tri(2-benzofuranate) at the maximum absorption wavelength is calculated by Lambert-Beer law to be 3.75×10 4 L·mol -1 cm -1 , indicating that the cellulose derivative has very high optical sensitivity and can be used as an optical sensing material.

[0054] 4) Fluorescence excitation and emission spectra of cellulose tris(2-benzofuranate)

[0055] Take an appropriate amount of cellulose tris(2-benzofuran carboxylate) and dissolve it in N,N-dimethylacetamide at a concentration of 1.0×10 -4 mol / L, and the fluorescence emission spectrum and excitation spectrum were tested using a fluorescence spectrophotometer.

[0056] The test results are as follows Figure 5 As shown in the figure, it can be seen that the excitation wavelength of the derivative is 302nm, the emission wavelength is 371nm, and the Stokes shift is 69nm, indicating that the derivative has a large Stokes shift.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0058] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a cellulose-based fluorescent material with a large Stokes shift, characterized in that: The following steps are involved: S1, after drying the microcrystalline cellulose, adding anhydrous N,N-dimethylacetamide to react under a nitrogen atmosphere, then cooling the reaction solution to room temperature, adding anhydrous lithium chloride under a nitrogen atmosphere to allow the microcrystalline cellulose to fully dissolve, thereby obtaining a system in which the microcrystalline cellulose is completely dissolved; S2, heating the system, then adding pyridine under a nitrogen atmosphere, then cooling the system, and sequentially adding benzofuran-2-carboxylic acid, 4-dimethylaminopyridine, and N,N'-diisopropylcarbodiimide under a nitrogen atmosphere, stirring to react, and obtaining a reaction mixture; S3, adding the reaction mixture into a methanol solution and stirring, then letting it stand, taking out the precipitate, washing and drying it to obtain cellulose tris(2-benzofurancarboxylate), i.e., a cellulose-based fluorescent material.

2. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: The synthetic route of cellulose-tri(2-benzofurancarboxylate) is:

3. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: In S1, the microcrystalline cellulose was dried in an oil bath system at 80°C.

4. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: In S2, the temperature of the system after heating is 80°C.

5. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: In S2, the temperature of the system after cooling is 30°C 6. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: In S3, the precipitate is washed by centrifugation with a methanol solution.

7. The method for preparing a cellulose-based fluorescent material with a large Stokes shift according to claim 1, characterized in that: In S3, the drying process is vacuum drying for 12 hours.

8. A cellulose-based fluorescent material with a large Stokes shift, characterized in that: The fluorescent material is prepared by the method for preparing a cellulose-based fluorescent material with a large Stokes shift as described in any one of claims 1 to 7.

9. Use of the cellulose-based fluorescent material with a large Stokes shift according to claim 8 in preparing a fluorescent probe or a fluorescent sensor.

10. A fluorescent probe, characterized in that The invention comprises the cellulose-based fluorescent material with large Stokes shift as claimed in claim 8.

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