Chiral nematic cellulose nanocrystal-curcumin composite film, preparation method thereof and application of chiral nematic cellulose nanocrystal-curcumin composite film as circular polarization fluorescent film

Abstract

The invention belongs to the technical field of circularly polarized optical materials, and particularly relates to a chiral nematic cellulose nanocrystal-curcumin composite film, a preparation method thereof and application of the chiral nematic cellulose nanocrystal-curcumin composite film as a circularly polarized fluorescent film. The invention provides a chiral nematic cellulose nanocrystal-curcumin composite film. The chiral nematic cellulose nanocrystal-curcumin composite film comprises a base material and an additive phase distributed in the base material, the base material is a chiral nematic cellulose nanocrystal, and the additive phase is curcumin. The chiral nematic cellulose nanocrystal-curcumin composite film provided by the invention is used as a circular polarization fluorescent film, takes curcumin as a fluorescent source, has a relatively large asymmetric factor, and is simple in preparation method and suitable for industrial production and application. Meanwhile, the circular polarization fluorescent film provided by the invention has a relatively large asymmetric factor by adding curcumin.

Description

Technical Field

[0001] The present invention belongs to the technical field of circularly polarized optical materials, and particularly relates to a chiral nematic cellulose nanocrystal-curcumin composite film, a preparation method thereof, and an application as a circularly polarized fluorescent film. Background Art

[0002] Circularly polarized luminescence (CPL) is a unique chiral optical property of chiral luminescence systems and has become one of the most useful tools for studying the excited state properties of chiral materials. Chiral optical materials with CPL activity have broad application prospects in many research fields such as three-dimensional display, enantioselective recognition of enantiomers, and non-invasive biomedical diagnosis, and have received extensive attention.

[0003] Currently, the preparation strategies of circularly polarized luminescence materials usually include the following two: (1) Intrinsic circularly polarized luminescence materials, using the intrinsic chiral molecular structure or chiral assembly of chiral small molecule luminescent units to construct circularly polarized luminescence materials; (2) Induced chiral luminescence materials, through co-assembly between chiral structures and achiral luminescent units, inducing luminescent molecules to emit circularly polarized light under the action of a chiral template.

[0004] In the circularly polarized luminescence molecular system, most materials have high luminescence efficiency, but the dissymmetry factor is low, and usually require cumbersome chemical synthesis, which causes difficulties for the practical application of circularly polarized luminescence. Summary of the Invention

[0005] The purpose of the present invention is to provide a chiral nematic cellulose nanocrystal-curcumin composite film, a preparation method thereof, and an application as a circularly polarized fluorescent film. The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention has a large dissymmetry factor as a circularly polarized fluorescent film, and the preparation method is simple and suitable for industrial production applications.

[0006] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a chiral nematic cellulose nanocrystal-curcumin composite film, including a substrate and an additive phase distributed in the substrate; the substrate is a chiral nematic cellulose nanocrystal, and the additive phase is curcumin.

[0008] Preferably, the mass ratio of the chiral nematic cellulose nanocrystal to the curcumin is (3000-15000):(0.5-5).

[0009] The present invention provides a preparation method of the chiral nematic cellulose nanocrystal-curcumin composite film as described in the above technical solution, including the following steps:

[0010] Mix the cellulose nanocrystal suspension and the curcumin solution to obtain a mixed solution;

[0011] After forming a film from the mixed solution and drying it, the chiral nematic cellulose nanocrystal-curcumin composite film is obtained.

[0012] Preferably, the mass percentage content of cellulose nanocrystals in the cellulose nanocrystal suspension is 1-5%.

[0013] Preferably, the curcumin solution is an ethanol solution of curcumin; the mass concentration of curcumin in the curcumin solution is 30-50 μg / mL.

[0014] Preferably, the mass ratio of the cellulose nanocrystal suspension to the curcumin solution is 3:(0.1-1).

[0015] Preferably, the mass ratio of the cellulose nanocrystal suspension to the curcumin solution is 3:(0.4-1).

[0016] Preferably, the preparation method of the cellulose nanocrystal suspension includes the following steps:

[0017] Mix cellulose pulp and sulfuric acid to carry out a hydrolysis reaction to obtain a hydrolysis reaction solution;

[0018] Dilute, wash with water, dialyze and concentrate the hydrolysis reaction solution in sequence to obtain the cellulose nanocrystal suspension.

[0019] Preferably, the cellulose pulp is bleached softwood pulp;

[0020] The mass percentage content of the sulfuric acid is 63-83%, and the ratio of the dry weight of the cellulose pulp to the amount of sulfuric acid used is (15-35) g:(150-350) mL;

[0021] The temperature of the hydrolysis reaction is 40-80 °C, and the time is 1-2 h.

[0022] The present invention provides the application of the chiral nematic cellulose nanocrystal-curcumin composite film described in the above technical solution or the chiral nematic cellulose nanocrystal-curcumin composite film prepared by the preparation method described in the above technical solution as a circularly polarized fluorescence film.

[0023] The present invention provides a chiral nematic cellulose nanocrystal-curcumin composite film, which includes a substrate and an additive phase distributed in the substrate; the substrate is chiral nematic cellulose nanocrystals, and the additive phase is curcumin. The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention exhibits a strong positive Cotton effect, indicating that the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention has a left-handed chiral structure. In the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention, the cellulose nanocrystals are twisted counterclockwise, confirming the left-handed structure of the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention. The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention, taking curcumin as a fluorescence source, has a large asymmetry factor as a circularly polarized fluorescence film.

[0024] Further, in the present invention, the mass ratio of the chiral nematic cellulose nanocrystals to the curcumin is (3000-15000):(0.5-5). By adding different masses of curcumin to the substrate, the present invention can further improve the asymmetry factor of the composite film as a circularly polarized fluorescence film.

[0025] The present invention provides a preparation method of the chiral nematic cellulose nanocrystal-curcumin composite film according to the above technical solution, including the following steps: mixing a cellulose nanocrystal suspension and a curcumin solution to obtain a mixed solution; forming a film from the mixed solution and drying it to obtain the chiral nematic cellulose nanocrystal-curcumin composite film. The present invention combines physical doping (mixing) and evaporation (drying) induced self-assembly to enable the self-assembly of chiral nematic cellulose nanocrystals and curcumin, and prepares a chiral nematic cellulose nanocrystal-curcumin composite film. The preparation method provided by the present invention has simple steps, low cost, and is suitable for industrialized extended application. Description of the Drawings

[0026] Figure 1 It is the fluorescence spectrogram of the chiral nematic cellulose nanocrystal-curcumin composite film prepared in Examples 1, 2, and 3 of the present invention;

[0027] Figure 2 It is the circular dichroism spectrogram of the chiral nematic cellulose nanocrystal-curcumin composite film prepared in Examples 1, 2, and 3 of the present invention;

[0028] Figure 3 It is the circularly polarized fluorescence spectrogram of the chiral nematic cellulose nanocrystal-curcumin composite film prepared in Example 3 of the present invention;

[0029] Figure 4 It is the distribution diagram of the circularly polarized fluorescence asymmetry factor of the chiral nematic cellulose nanocrystal-curcumin composite film prepared in Example 3 of the present invention. Detailed implementation mode

[0030] The present invention provides a chiral nematic cellulose nanocrystal-curcumin composite film, which comprises a substrate and an additive phase distributed in the substrate; the substrate is a chiral nematic cellulose nanocrystal, and the additive phase is curcumin.

[0031] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well-known to those skilled in the art.

[0032] The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention comprises a substrate. The substrate is a chiral nematic cellulose nanocrystal. In the present invention, in the chiral nematic cellulose nanocrystal-curcumin composite film: the cellulose nanocrystal twists counterclockwise, presenting an assembled helical structure and having rich optical properties.

[0033] The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention comprises an additive phase distributed in the substrate. The additive phase is curcumin. In the present invention, the curcumin is distributed between the layers of the assembled helical structure of the cellulose nanocrystals.

[0034] In the present invention, the mass ratio of the chiral nematic cellulose nanocrystal to the curcumin is preferably (3000-15000):(0.5-5), more preferably (6000-15000):(0.5-5), and most preferably 15000:(2-5). Specifically in the examples, it is 15000:2, 15000:4 or 15000:5. By adjusting the mass content of curcumin in the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention, the chiral absorption wavelength of the film can be effectively adjusted within the visible light spectrum range.

[0035] The chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention exhibits a strong positive Cotton effect, indicating that the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention has a left-handed chiral structure. The cellulose nanocrystal in the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention twists counterclockwise, confirming the left-handed structure of the chiral nematic cellulose nanocrystal-curcumin composite film provided by the present invention.

[0036] The present invention provides a preparation method of the chiral nematic cellulose nanocrystal-curcumin composite film according to the above technical solution, comprising the following steps:

[0037] Mix a cellulose nanocrystal suspension and a curcumin solution to obtain a mixed solution;

[0038] Form the mixed solution into a film and dry it to obtain the chiral nematic cellulose nanocrystal-curcumin composite film.

[0039] The present invention mixes a cellulose nanocrystal suspension and a curcumin solution to obtain a mixed solution.

[0040] In the present invention, the mass percentage content of cellulose nanocrystals in the cellulose nanocrystal suspension is preferably 1-5%, more preferably 2-5%.

[0041] In the present invention, the preparation method of the cellulose nanocrystal suspension preferably includes the following steps:

[0042] Mix cellulose pulp and sulfuric acid for hydrolysis reaction to obtain a hydrolysis reaction solution;

[0043] Dilute, wash with water, dialyze and concentrate the hydrolysis reaction solution in sequence to obtain the cellulose nanocrystal suspension.

[0044] In the present invention, cellulose pulp and sulfuric acid are mixed for hydrolysis reaction to obtain a hydrolysis reaction solution. In the present invention, the cellulose pulp is specifically bleached softwood pulp. The mass percentage content of the sulfuric acid is preferably 63-83%, more preferably 65-80%. The dry weight ratio of the cellulose pulp to the amount of sulfuric acid used is preferably (15-35) g:(150-350) mL, more preferably (20-30) g:(200-300) mL. The temperature of the hydrolysis reaction is preferably 40-80°C, more preferably 50-60°C. The time of the hydrolysis reaction is preferably 1-2 h. The hydrolysis reaction is preferably carried out under the condition of mechanical stirring, and the rotation speed of the hydrolysis reaction stirring is preferably 300-500 rpm.

[0045] After obtaining the hydrolysis reaction solution, the present invention dilutes, washes with water, dialyzes and concentrates the hydrolysis reaction solution in sequence to obtain the cellulose nanocrystal suspension. In the present invention, the dilution preferably uses water to dilute the hydrolysis reaction solution to obtain a diluted hydrolysis reaction solution, and the volume ratio of the diluted hydrolysis reaction solution to the hydrolysis reaction solution is preferably 4:1. The water washing is preferably carried out by centrifugation, and the rotation speed of the centrifugation is preferably 4000-8000 rpm. The number of times of water washing is preferably 1-3 times. The present invention preferably places the hydrolyzed reaction solution after water washing in a dialysis bag and dialyzes it in deionized water. The time of dialysis is preferably 5-7 days. After dialysis, a dialysis reaction solution is obtained in the dialysis bag, and the pH value of the dialysis reaction solution is preferably 6.5-7.5. After dialysis, the present invention preferably ultrasonically treats the obtained dialysis reaction solution and then concentrates it. The time of ultrasonic treatment is preferably 30 min. The present invention has no special requirements for the specific implementation process of the concentration, and it is ensured that the mass content of cellulose nanocrystals in the concentrated cellulose nanocrystal suspension is preferably 1-5%, preferably 5%.

[0046] In the present invention, the curcumin solution is preferably an ethanol solution of curcumin. The mass concentration of curcumin in the curcumin solution is preferably 30 - 50 μg / mL, specifically 50 μg / mL in the examples.

[0047] In the present invention, the mass ratio of the cellulose nanocrystal suspension to the curcumin solution is 3:(0.1 - 1), more preferably 3:(0.4 - 1), specifically 3:0.1, 3:0.2, 3:0.4, 3:0.8 or 3:1 in the examples.

[0048] In the present invention, the mixing of the cellulose nanocrystal suspension and the curcumin solution preferably includes: adding the curcumin solution to the cellulose nanocrystal suspension by physical doping method, and then performing ultrasonic treatment; the time of the ultrasonic treatment is preferably 20 min.

[0049] After obtaining the mixed solution, the present invention forms the mixed solution into a film and then dries it to obtain the chiral nematic cellulose nanocrystal - curcumin composite film. The present invention has no special requirements for the specific implementation manner of the film formation. The drying temperature is preferably room temperature, and no additional heating and cooling are required.

[0050] The present invention provides the application of the chiral nematic cellulose nanocrystal - curcumin composite film described in the above technical solution or the chiral nematic cellulose nanocrystal - curcumin composite film prepared by the preparation method described in the above technical solution as a circularly polarized fluorescence film.

[0051] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in combination with examples, but they cannot be understood as limiting the protection scope of the present invention.

[0052] Example 1

[0053] Preparation of chiral nematic cellulose nanocrystal / curcumin composite film (CNC / Cur - 0.4)

[0054] 1) Add bleached softwood pulp to sulfuric acid (the mass concentration of sulfuric acid is 63%), wherein the dry weight of the bleached softwood pulp and the dosage of sulfuric acid are in a ratio of 20 g:200 mL. Under the condition of 40 °C, mechanically stir at a speed of 500 rpm for 2.0 h. After the stirring is completed, dilute the solution with water to four times the original volume, centrifuge (at a speed of 8000 rpm), rinse cyclically, and repeat three times, then dialyze in deionized water for 7 days until the pH reaches 6.5 - 7.5. Ultrasonic the hydrolyzed reaction solution after dialysis for 30 min, and finally concentrate to prepare a cellulose nanocrystal suspension with a mass percentage of 5%.

[0055] 2) Add 0.4 g of curcumin ethanol solution (the mass concentration of the curcumin solution is 50 μg / mL) to the chiral nematic cellulose nanocrystal suspension (3 g) prepared in step 1), mix them, and then sonicate for 20 min;

[0056] 3) Film the mixed solution obtained in step 2 and dry it at room temperature to obtain a circularly polarized fluorescence film (CNC / Cur-0.4) based on chiral nematic cellulose nanocrystals and curcumin with circularly polarized fluorescence properties. Use tweezers to collect the dried film for subsequent characterization.

[0057] Detect the fluorescence spectrum of the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin prepared in Example 1, and the obtained results are as Figure 1 shown; According to Figure 1 it can be seen that there is a maximum peak in the fluorescence spectrum at about 540 nm, indicating that the optimal emission wavelength of the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin is 540 nm.

[0058] Test the circular dichroism spectrum of the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin prepared in Example 1, and the obtained results are as Figure 2 shown; According to Figure 2 it can be seen that the circularly polarized fluorescence film of chiral nematic cellulose nanocrystals and curcumin exhibits a strong positive Cotton effect, indicating that the film has a left-handed chiral structure, and the cellulose nanocrystals twist counterclockwise, confirming the left-handed structure of the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin.

[0059] Example 2

[0060] Preparation of chiral nematic cellulose nanocrystal / curcumin composite film (CNC / Cur-0.8)

[0061] 1) Add bleached softwood pulp to sulfuric acid (the mass concentration of sulfuric acid is 63%), where the dry weight ratio of bleached softwood pulp to the amount of sulfuric acid used is 20 g:200 mL. Under the condition of 40 °C, mechanically stir at a speed of 500 rpm for 2.0 h. After stirring, dilute the solution with water to four times the original volume, centrifuge (at a speed of 8000 rpm) and rinse repeatedly for three times, and then dialyze in deionized water for 7 days until the pH reaches 6.5 - 7.5. Ultrasonic the dialyzed hydrolysis reaction solution for 30 min, and finally concentrate to prepare a cellulose nanocrystal suspension with a mass percentage of 5%;

[0062] 2) Add 0.8 g of curcumin ethanol solution (the mass concentration of the curcumin solution is 50 μg / mL) to the chiral nematic cellulose nanocrystal suspension (3 g) prepared in step 1), mix them, and then sonicate for 20 min;

[0063] 3) Film the mixed solution obtained in step 2) and dry it at room temperature to obtain a circularly polarized fluorescence film (CNC / Cur-0.8) based on chiral nematic cellulose nanocrystals and curcumin with circularly polarized fluorescence properties. Use tweezers to collect the dried film for subsequent characterization.

[0064] Detect the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin prepared in Example 2 in the manner of Example 1, and the results are as Figure 1 and Figure 2 shown. The results show that they are consistent with the results of Example 1.

[0065] Example 3

[0066] Preparation of chiral nematic cellulose nanocrystals / curcumin composite film (CNC / Cur-1.0)

[0067] 1) Add bleached softwood pulp to sulfuric acid (the mass concentration of sulfuric acid is 63%), wherein the dry weight ratio of bleached softwood pulp to the amount of sulfuric acid used is 20 g: 200 mL. Under the condition of 40 °C, mechanically stir at a speed of 500 rpm for 2.0 h. After stirring, dilute the solution with water to four times the original volume, centrifuge (at a speed of 8000 rpm), rinse cyclically, repeat three times, and then dialyze in deionized water for 7 days until the pH reaches 6.5-7.5. Ultrasonicate the dialyzed hydrolysis reaction solution for 30 min, and finally concentrate to prepare 3 g of a cellulose nanocrystal suspension with a mass percentage of 5%;

[0068] 2) Add 1.0 g of curcumin ethanol solution (the mass concentration of the curcumin solution is 50 μg / mL) to the chiral nematic cellulose nanocrystal suspension (3 g) prepared in step 1) and mix, and then ultrasonicate for 20 min;

[0069] 3) Film the mixed solution obtained in step 2) and dry it at room temperature to obtain a circularly polarized fluorescence film (CNC / Cur-1.0) based on chiral nematic cellulose nanocrystals and curcumin with circularly polarized fluorescence properties. Use tweezers to collect the dried film for subsequent characterization.

[0070] Detect the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin prepared in Example 3 in the manner of Example 1, and the results are as Figure 1 and Figure 2 shown. The results show that they are consistent with the results of Example 1.

[0071] In addition, from Example 1, Example 2 and Example 3, as the content of the curcumin solution increases, Figure 2The peak wavelength of the circular dichroism (CD) redshifts from 319 nm to 428 nm, indicating that the chiral absorption wavelength of the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin provided by the present invention can be effectively adjusted within the visible spectral range.

[0072] Since the fluorescence intensity of the CNC / Cur-1.0 composite film prepared in Example 3 is the highest, the circular polarization spectrum and the dissymmetry factor g of the CNC / Cur-1.0 composite film prepared in Example 3 lum were detected, and the obtained results are as Figure 3 shown in Figure 4 ; from Figure 4 the results, it can be seen that the circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin prepared in Example 3 has a negative dissymmetry factor, and the dissymmetry factor g at 540 nm lum is higher than that at 680 nm, corresponding to the spectrum of the circularly polarized fluorescence spectrum.

[0073] From the above examples, the present invention provides a method for preparing a circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin, comprising the following steps: mixing cellulose and sulfuric acid for hydrolysis reaction to obtain a cellulose nanocrystal suspension; sequentially diluting, washing with water, dialyzing, and concentrating the cellulose nanocrystal suspension to obtain a chiral nematic cellulose nanocrystal suspension; mixing the chiral nematic cellulose nanocrystal suspension and a curcumin solution to form a film, thereby obtaining a circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin. The method provided by the present invention combines the physical doping method and the evaporation-induced self-assembly technology to enable the self-assembly of chiral nematic cellulose nanocrystals and curcumin, and prepares a circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin. This method uses the green and easily available chiral nematic cellulose nanocrystals as the matrix and curcumin as the fluorescence source, and the steps are simple.

[0074] The present invention also provides a circularly polarized fluorescence film based on chiral nematic cellulose nanocrystals and curcumin. The results of the examples show that the circularly polarized fluorescence film provided by the present invention has a large dissymmetry factor.

[0075] Although the above examples have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can also be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A chiral nematic cellulose nanocrystal-curcumin composite film, comprising a substrate and an added phase distributed in the substrate; the substrate is a chiral nematic cellulose nanocrystal, and the added phase is curcumin.

2. The chiral nematic cellulose nanocrystal-curcumin composite film according to claim 1, characterized in that: The mass ratio of the chiral nematic cellulose nanocrystals to the curcumin is (3000-15000): (0.5-5).

3. The method for preparing the chiral nematic cellulose nanocrystal-curcumin composite film according to claim 1 or 2, comprising the following steps: mixing the cellulose nanocrystal suspension and the curcumin solution to obtain a mixed solution; The mixed solution is formed into a film and then dried to obtain the chiral nematic cellulose nanocrystal-curcumin composite film.

4. The preparation method according to claim 3, characterized in that: The mass percentage of the cellulose nanocrystals in the cellulose nanocrystal suspension is 1-5%.

5. The preparation method according to claim 3, characterized in that: The curcumin solution is an ethanol solution of curcumin; the mass concentration of curcumin in the curcumin solution is 30-50 μg / mL.

6. The preparation method according to any one of claims 3 to 5, characterized in that: The mass ratio of the cellulose nanocrystal suspension to the curcumin solution is 3:(0.1-1).

7. The preparation method according to claim 6, characterized in that: The mass ratio of the cellulose nanocrystal suspension to the curcumin solution is 3:(0.4-1).

8. The preparation method according to claim 3 or 4, characterized in that: The preparation method of the cellulose nanocrystal suspension comprises the following steps: mixing cellulose pulp and sulfuric acid to perform a hydrolysis reaction to obtain a hydrolysis reaction liquid; The hydrolysis reaction liquid is diluted, washed, dialyzed and concentrated in sequence to obtain the cellulose nanocrystal suspension.

9. The preparation method according to claim 8, characterized in that: The cellulose pulp is bleached conifer pulp; The mass percentage of the sulfuric acid is 63-83%, and the usage ratio of the dry weight of the cellulose pulp to the sulfuric acid is (15-35) g: (150-350) mL; The temperature of the hydrolysis reaction is 40-80° C. and the time is 1-2 hours.

10. Use of the chiral nematic cellulose nanocrystal-curcumin composite film according to claim 1 or 2 or the chiral nematic cellulose nanocrystal-curcumin composite film prepared by the preparation method according to any one of claims 3 to 9 as a circularly polarized fluorescent film.

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