Hemicellulose nanocrystalline material with double refractive properties and preparation method of hemicellulose nanocrystalline material

Abstract

The invention discloses a hemicellulose nanocrystalline material with double-refraction performance and a preparation method thereof, and belongs to the technical field of optical materials.The preparation method of the hemicellulose nanocrystalline material with the double-refraction performance comprises the following steps that hemicellulose is extracted from plant straw, the hemicellulose is resuspended with pure water, and the hemicellulose nanocrystal material with the double-refraction performance is obtained; the preparation method comprises the following steps: performing ultrasonic treatment on hemicellulose, standing, arranging and aggregating hemicellulose molecules to form nanocrystal particles, and placing a hemicellulose nanocrystal particle suspension in the middle of double-layer thin glass to perform solvent restrictive evaporation induced self-assembly, thereby finally preparing the hemicellulose nanocrystal material (namely, the hemicellulose nanocrystal self-assembly material). The invention also provides a plant straw hemicellulose extraction method, a hemicellulose nano-particle preparation method and a nano-particle self-assembly technology, the prepared hemicellulose nano-crystal self-assembly material shows colored double refractivity, and a foundation is laid for subsequent preparation of a novel glycosyl material.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical material preparation, and in particular relates to a hemicellulose nanocrystalline material with birefringence and a preparation method thereof. Background Art

[0002] Plant straw biomass is primarily composed of lignocellulose, a naturally abundant renewable resource primarily composed of cellulose, hemicellulose, and lignin. Recent research has shown that lignocellulose, in addition to being used for bioenergy and returning to farmland, has broad potential applications in agriculture, industry, light industry, and healthcare. These include cellulose-based products such as paper, textiles, and nanocrystals; lignin-based products such as biochar, carbon nanotubes, carbon quantum dots, and antioxidants; and hemicellulose-based products such as prebiotics, xylitol, and drug carriers.

[0003] Natural polysaccharide nanocrystals possess excellent intrinsic biodegradability, biocompatibility, customizable surface chemistry, and unique optical and mechanical properties, offering broad application prospects in composite materials, biomedicine, and other fields. Previously reported polysaccharide nanocrystal particles are primarily derived from cellulose, starch, and chitin. The nanoscale crystalline fractions, extracted by enzymatic, acidic, mechanical, and ultrasound-assisted methods, typically exhibit rod- or needle-like morphologies and range in size from a few to tens of nanometers. Unlike linear polysaccharides such as cellulose and starch, hemicellulose is a heterogeneous polysaccharide with a more complex chemical structure and diverse functionalities. Using specific solvents and treatment methods, the crystalline fraction of hemicellulose is isolated, forming nanoscale crystalline particles, known as hemicellulose nanocrystals. Hemicellulose nanocrystals typically range in size from a few to tens of nanometers and possess diverse morphologies, with rods, flakes, or spheres being common. Their size and morphology can be manipulated through the preparation conditions.

[0004] Polysaccharide nanocrystals (such as cellulose nanocrystals, chitin nanocrystals, etc.) exhibit a series of excellent optical properties due to their unique nanostructure and rich surface functional groups. Hemicellulose nanoparticles have shown many application potentials in optical properties due to their unique structure and surface characteristics. For example, some studies have solved the compatibility problem between hemicellulose and nanocellulose by chemical cross-linking, further improving the UV shielding performance of the composite film. In addition, by combining hemicellulose nanoparticles with other materials (such as carbon dots, inorganic oxides, etc.), new materials with excellent optical properties have also been developed. However, there are no research cases on the optical properties of self-assembled materials of hemicellulose nanoparticles themselves. Summary of the Invention

[0005] In response to the above technical problems, the present invention proposes a hemicellulose nanocrystalline material with birefringence and a preparation method thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions:

[0008] A method for preparing a hemicellulose nanocrystalline material with birefringence performance comprises the following steps:

[0009] Hemicellulose is extracted from plant straw, resuspended in pure water, and then ultrasonically treated and allowed to stand to allow the hemicellulose molecules to arrange and aggregate to form nanocrystalline particles. The hemicellulose nanocrystal suspension is placed between double layers of thin glass for solvent-restricted evaporation to induce self-assembly, ultimately preparing hemicellulose nanocrystal material (i.e., hemicellulose nanocrystal self-assembly material).

[0010] The reaction mechanism involved in the above-mentioned preparation process of the present invention is as follows: plant straw biomass is mainly composed of cellulose, hemicellulose and lignin. Sodium chlorite treatment destroys the stability of lignin-carbohydrate and removes lignin, which can improve the extraction efficiency and purity of hemicellulose. Sodium hydroxide treatment is used to extract the hemicellulose, and after adding absolute ethanol, the hemicellulose is precipitated. Hemicellulose can be obtained by this method. Water is added to resuspend the hemicellulose, and ultrasonic treatment can promote the polymerization of hemicellulose macromolecules to form stable nanocrystalline particles. The nanoparticles are dropped into the middle of double-layer glass to limit the evaporation rate of the solvent water, promoting the slow and uniform aggregation of the hemicellulose nanocrystalline particles to form a novel hemicellulose-based material. Because hemicellulose is a chiral macromolecule, under the restricted evaporation conditions of the double-layer glass preparation, it self-assembles to form a novel material with birefringence.

[0011] Optionally, the process of extracting hemicellulose from plant straw is:

[0012] (1) Treating plant straw powder with sodium chlorite solution to remove lignin;

[0013] (2) Hemicellulose was extracted by treating with sodium hydroxide solution, and then precipitated with anhydrous ethanol and centrifuged to obtain hemicellulose.

[0014] Beneficial effects: The present invention utilizes sodium chlorite and sodium hydroxide to remove lignin and further purify hemicellulose, respectively, thereby ensuring high purity and good reaction activity of the hemicellulose in subsequent steps; adding anhydrous ethanol for low-temperature precipitation and then centrifuging and collecting the precipitate effectively concentrates the target product, thereby increasing the yield and reducing impurities.

[0015] Furthermore, the plant straw is sorghum straw.

[0016] Furthermore, the plant straw powder is sieved through a 40-mesh sieve.

[0017] Furthermore, the mass concentration of the sodium chlorite solution is 8%; the concentration of the sodium hydroxide solution is 4M.

[0018] Furthermore, the centrifugal speed is 4000-6000 rpm.

[0019] Optionally, the power of the ultrasound is 10-20W; preferably 12, 15, 20W; more preferably 15W.

[0020] Beneficial effects: The present invention prepares a stable hemicellulose nanocrystal suspension through ultrasonic treatment, which is crucial for ensuring the uniformity and stability of the final product.

[0021] Optionally, the standing condition is: standing at 4° C. for 12-36 hours.

[0022] Optionally, the self-assembly process is carried out under the following conditions: standing at room temperature for 24 hours to 48 hours.

[0023] Beneficial Effects: The present invention allows for limited evaporation of the solvent through a simple dropwise addition and glass cover, promoting the self-assembly of hemicellulose nanocrystals. Finally, a colored pattern was observed using a polarized light microscope, confirming the birefringence of the material.

[0024] Technical solution 2:

[0025] A hemicellulose nanocrystalline material with birefringence is prepared by the above preparation method.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] 1. This invention successfully utilizes agricultural waste—plant straw—as raw material to develop a new, birefringent hemicellulose-based nanomaterial. This not only broadens the application scope of natural resources but also promotes their efficient utilization.

[0028] 2. The present invention provides a relatively simple and cost-effective preparation process, which is suitable for large-scale production and provides the possibility for industrial application.

[0029] 3. The hemicellulose-based nanomaterials prepared in the present invention exhibit unique birefringence optical properties, that is, color patterns can be observed under polarized light, indicating that the material has potential optical application prospects, such as in optical devices, sensors and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 This is a picture of the semi-fibrous nanocrystalline particle suspension prepared in step 6) of Example 1;

[0032] Figure 2 This is an atomic force microscope image of hemicellulose single nanocrystals in the hemicellulose nanocrystal particle suspension prepared in step 6) of Example 1;

[0033] Figure 3 This is a scanning electron micrograph of hemicellulose single nanocrystals in the hemicellulose nanocrystal particle suspension prepared in step 6) of Example 1;

[0034] Figure 4 This is a transmission electron micrograph of hemicellulose single nanocrystals in the hemicellulose nanocrystal particle suspension prepared in step 6) of Example 1;

[0035] Figure 5 The scanning electron microscope images of different parts of the nanocrystalline particle self-assembly material prepared in step 7) of Example 1;

[0036] Figure 6 4x polarized light microscope images, A is the hemicellulose self-assembly material prepared in Comparative Example 1, and B is the hemicellulose nanocrystal self-assembly material prepared in Example 1;

[0037] Figure 7 This is a 10x polarized light microscope image of the hemicellulose nanocrystal self-assembly material prepared in Example 1. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] The present invention extracts hemicellulose from plant straw, treats it with ultrasound, and then allows it to stand, allowing the hemicellulose molecules to align and aggregate to form nanocrystalline particles. The hemicellulose nanocrystalline particle suspension is then placed between two layers of thin glass for solvent-restricted evaporation to induce self-assembly. The resulting hemicellulose nanocrystalline self-assembled material exhibits colorful birefringence. Specifically:

[0044] The present invention provides a method for preparing a hemicellulose-based nanomaterial having birefringence, comprising the following steps:

[0045] 1) Hemicellulose derived from plant straw biomass;

[0046] 2) preparing hemicellulose nanocrystal particles by ultrasonic treatment of hemicellulose;

[0047] 3) Nanocrystalline particles self-assemble in the middle of the double-layer glass to obtain hemicellulose nanocrystalline material, which appears colorful under a polarized light microscope.

[0048] In some optional embodiments, the preparation method specifically includes the following steps:

[0049] 1) crushing the plant straw with a grinder, sieving, and further grinding into powder with a ball mill;

[0050] 2) Treat with sodium chlorite at room temperature to remove lignin, turning the powder white, and then wash with water 4-6 times;

[0051] 3) Treat with sodium hydroxide at room temperature for 2-4 hours, recover the supernatant by centrifugation, and adjust the pH to neutral with HCl;

[0052] 4) Add a certain volume of anhydrous ethanol and precipitate at low temperature overnight;

[0053] 5) collecting the precipitate by centrifugation to obtain hemicellulose;

[0054] 6) Treat with ultrasonic waves at 12-20W and allow to stand at low temperature for more than 12 hours to obtain a stable hemicellulose nanocrystal suspension;

[0055] 7) Centrifuge and drip the supernatant onto a corner of a thin glass slide (no special instructions for the size of the glass slide), cover it with another thin glass slide parallel to the top, and let it stand at room temperature to allow the solvent to evaporate, thereby completing the self-assembly;

[0056] 8) Using a polarized light microscope, a colorful pattern of self-assembled nanocrystalline particles (hemicellulose nanocrystalline material) was observed through glass.

[0057] In some optional embodiments, the plant straw is sorghum straw. Sorghum straw has a high cellulose content and is abundant in raw materials. The cost of obtaining cellulose from sorghum straw is low, and the cellulose separation efficiency is high.

[0058] In some optional embodiments, in step 1), the plant straw is crushed to 40 mesh. The outer layer of the sorghum straw stem is composed of a tightly arranged composite structure of cellulose, hemicellulose and lignin. The crushing can destroy its natural barrier, making the internal cellulose easier to extract later. The surface area of ​​the crushed straw particles is significantly increased, which is conducive to the full contact between chemical reagents and cellulose.

[0059] In some optional embodiments, the mass concentration of the sodium chlorite solution is 8%; the concentration of the sodium hydroxide solution is 4M.

[0060] In some optional embodiments, the centrifugal speed in step 3) is 4000-6000 rpm.

[0061] In some optional embodiments, the self-assembly process is performed under the following conditions: standing at room temperature for 24 hours to 48 hours.

[0062] Unless otherwise specified, the "room temperature" in the present invention refers to 20-30°C.

[0063] The raw materials used in the present invention are all purchased from the market.

[0064] The technical solution of the present invention is further illustrated by the following examples.

[0065] Example 1

[0066] A method for preparing a hemicellulose-based nanomaterial with birefringence properties comprises the following steps:

[0067] 1) Cut sorghum stalks into segments of approximately 5 cm in length, crush them using a grinder, pass them through a 40-mesh sieve, and further grind them into powder using a ball mill;

[0068] 2) Treat 1 g of sorghum straw powder with 20 ml of 8% sodium chlorite at room temperature for 24 hours. The treatment was carried out at room temperature and a shaking speed of 120 rpm / min. The powder turned white and was washed with water six times.

[0069] 3) The powder obtained in step 2) was treated with 20 ml of 4 M sodium hydroxide at room temperature for 2 h, centrifuged at 5000 rpm, and the supernatant was recovered and the pH was adjusted to neutral with 1 M HCl;

[0070] 4) Add 2.5 volumes of anhydrous ethanol and allow to precipitate overnight at 4°C;

[0071] 5) Centrifuge at 5000 rpm to collect the precipitate to obtain hemicellulose;

[0072] 6) Resuspend the hemicellulose in 5 ml of pure water, treat with ultrasound at 15W for 40 min, and let stand at 4°C for more than 24 h to obtain a stable hemicellulose nanocrystal suspension;

[0073] 7) Centrifuge at 5000 rpm, drop 10 μl of the upper hemicellulose nanocrystal suspension onto a corner of a thin glass slide (no special instructions for the size of the glass slide), cover it with another thin glass slide, and let it stand at room temperature for more than 24 hours to allow the solvent water to evaporate slowly;

[0074] 8) Using a polarized light microscope to observe through glass, you can observe a colorful pattern of self-assembled nanocrystalline particles.

[0075] Example 2

[0076] A method for preparing a hemicellulose-based nanomaterial with birefringence properties comprises the following steps:

[0077] 1) Cut sorghum stalks into segments of approximately 5 cm in length, crush them using a grinder, pass them through a 40-mesh sieve, and further grind them into powder using a ball mill;

[0078] 2) Treat 1 g of sorghum straw powder with 20 ml of 8% sodium chlorite at room temperature for 24 h. The treatment was carried out at room temperature and a shaking speed of 120 rpm / min. The powder turned white and was washed with water six times.

[0079] 3) Treat with 20 ml of 4 M sodium hydroxide at room temperature for 2 h, centrifuge at 5000 rpm to recover the supernatant, and adjust the pH to neutral with 1 M HCl;

[0080] 4) Add 2.5 volumes of anhydrous ethanol and allow to precipitate overnight at 4°C;

[0081] 5) Centrifuge at 5000 rpm to collect the precipitate to obtain hemicellulose;

[0082] 6) Resuspend the hemicellulose in 5 ml of pure water, treat with ultrasound at 12W for 40 min, and let stand at 4°C for more than 24 h to obtain a stable hemicellulose nanocrystal suspension;

[0083] 7) Centrifuge at 5000 rpm, drop 10 μl of the upper hemicellulose nanocrystal suspension onto a corner of a thin glass slide (no special instructions for the size of the glass slide), cover it with another thin glass slide, and let it stand at room temperature for more than 24 hours to allow the solvent water to evaporate slowly;

[0084] 8) Using a polarized light microscope to observe through glass, you can observe a colorful pattern of self-assembled nanocrystalline particles.

[0085] Example 3

[0086] A method for preparing a hemicellulose-based nanomaterial with birefringence properties comprises the following steps:

[0087] 1) Cut sorghum stalks into segments of approximately 5 cm in length, crush them using a grinder, pass them through a 40-mesh sieve, and further grind them into powder using a ball mill;

[0088] 2) Treat 1 g of sorghum straw powder with 20 ml of 8% sodium chlorite at room temperature for 24 h. The treatment was carried out at room temperature and a shaking speed of 120 rpm / min. The powder turned white and was washed with water six times.

[0089] 3) Treat with 20 ml of 4 M sodium hydroxide at room temperature for 2 h, centrifuge at 5000 rpm to recover the supernatant, and adjust the pH to neutral with 1 M HCl;

[0090] 4) Add 2.5 volumes of anhydrous ethanol and allow to precipitate overnight at 4°C;

[0091] 5) Centrifuge at 5000 rpm to collect the precipitate to obtain hemicellulose;

[0092] 6) Resuspend the hemicellulose in 5 ml of pure water, treat with ultrasound at 20W for 40 min, and let stand at 4°C for more than 24 h to obtain a stable hemicellulose nanocrystal suspension;

[0093] 7) Centrifuge at 5000 rpm, drop 10 μl of the upper hemicellulose nanocrystal suspension onto a corner of a thin glass slide (no special instructions for the size of the glass slide), cover it with another thin glass slide, and let it stand at room temperature for more than 24 hours to allow the solvent water to evaporate slowly;

[0094] 8) Using a polarized light microscope to observe through glass, you can observe a colorful pattern of self-assembled nanocrystalline particles.

[0095] Comparative Example 1

[0096] 1) Cut sorghum stalks into segments of approximately 5 cm in length, crush them using a grinder, pass them through a 40-mesh sieve, and further grind them into powder using a ball mill;

[0097] 2) Treat 1 g of sorghum straw powder with 20 ml of 8% sodium chlorite at room temperature for 24 h. The treatment was carried out at room temperature and a shaking speed of 120 rpm / min. The powder turned white and was washed with water six times.

[0098] 3) Treat with 20 ml of 4 M sodium hydroxide at room temperature for 2 h, centrifuge at 5000 rpm to recover the supernatant, and adjust the pH to neutral with 1 M HCl;

[0099] 4) Add 2.5 volumes of anhydrous ethanol and allow to precipitate overnight at 4°C;

[0100] 5) Centrifuge at 5000 rpm to collect the precipitate to obtain hemicellulose;

[0101] 6) Resuspend the hemicellulose in 5 ml of pure water to obtain a hemicellulose suspension;

[0102] 7) Drop the hemicellulose suspension onto a corner of a thin glass slide (no special instructions for the size of the glass slide), cover it with another thin glass slide, and let it stand at room temperature for more than 24 hours to allow the solvent water to slowly evaporate, thereby obtaining a hemicellulose self-assembled material;

[0103] 8) No color pattern was observed through the glass using a polarized light microscope.

[0104] Figure 1 This is a picture of the semi-fibrous nanocrystalline particle suspension prepared in step 6) of Example 1;

[0105] Figure 2-4 This is a micrograph of a single hemicellulose nanocrystal particle in the hemicellulose nanocrystal particle suspension prepared in step 6) of Example 1; wherein, Figure 2 This is an atomic force microscope image. Figure 3 Scanning electron microscope images, Figure 4 It is a transmission electron microscope image; it can be seen from the image that the hemicellulose nanocrystal particles have a small size (about 50-200nm) and are well dispersed; the hemicellulose nanocrystal particles are elliptical or irregular in shape, with a certain degree of roughness and undulation on the surface; in addition, the hemicellulose nanocrystal particles have high crystallinity and order, and the internal lattice stripes are clear.

[0106] Figure 5 This is a scanning electron microscope image of the self-assembled nanocrystalline material prepared in step 7) of Example 1. As can be seen from the image, the nanocrystalline particles self-assemble into a stripe pattern structure with irregular branches under the double-layer glass confinement induced by solvent evaporation.

[0107] Figure 6 The following are polarized light microscopy images taken at 4x magnification: A shows the hemicellulose self-assembled material prepared in Comparative Example 1, and B shows the hemicellulose nanocrystal self-assembled material prepared in Example 1. As can be seen from the figure, the hemicellulose self-assembled material prepared in Comparative Example 1 is not colored, while the hemicellulose nanocrystal self-assembled material prepared in Example 1 exhibits colored strips, indicating birefringence.

[0108] Figure 7 This is a 10x polarized light microscope image of the hemicellulose nanocrystal self-assembly material prepared in Example 1. Under high magnification, birefringence of the hemicellulose nanocrystal self-assembly material was observed, proving that the self-assembly material prepared in the present invention has optical properties.

[0109] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing hemicellulose nanocrystalline material with birefringence, characterized in that: The following steps are involved: Hemicellulose is extracted from plant straw, and the hemicellulose is resuspended in pure water, subjected to ultrasonic treatment, and then allowed to stand to obtain a hemicellulose nanocrystal particle suspension. The hemicellulose nanocrystal particle suspension is placed in the middle of a double layer of glass to carry out solvent-restricted evaporation-induced self-assembly, and finally the hemicellulose nanocrystal material is prepared.

2. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 1, characterized in that: The process of extracting hemicellulose from plant straw is as follows: (1) treating plant straw powder with sodium chlorite solution; (2) Hemicellulose was extracted by treating with sodium hydroxide solution, and then precipitated with anhydrous ethanol and centrifuged to obtain hemicellulose.

3. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 2, characterized in that: The plant straw is sorghum straw.

4. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 3, characterized in that: The plant straw powder is passed through a 40-mesh sieve.

5. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 2, characterized in that: The mass concentration of the sodium chlorite solution is 8%; the concentration of the sodium hydroxide solution is 4M.

6. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 2, characterized in that: The centrifugal speed is 4000-6000 rpm.

7. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 1, characterized in that: The power of the ultrasonic wave is 10-20W.

8. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 1, characterized in that: The standing condition is: standing at 4° C. for 12-36 hours.

9. The method for preparing a hemicellulose nanocrystalline material with birefringence according to claim 1, characterized in that: The self-assembly process is carried out under the following conditions: standing at room temperature for 24 hours to 48 hours.

10. A hemicellulose nanocrystalline material with birefringence, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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