High-conjugation biomass carbon quantum dot as well as preparation method and application thereof

Abstract

The invention discloses a high-conjugation biomass carbon quantum dot and a preparation method and application thereof.The method comprises the steps that a biomass material is subjected to pre-irradiation treatment with the electron irradiation dose being 900-3600 kGy, water is adopted to prepare an aqueous solution, and then a hydrothermal reaction is conducted; and after the reaction is finished, cooling, centrifuging, removing large particles, dialyzing the supernate by using a 1000Da dialysis bag, collecting the solution in the dialysis bag, and freeze-drying to obtain the high-conjugation biomass carbon quantum dots. The high-conjugation biomass carbon quantum dot disclosed by the invention can remarkably improve the electron migration rate and the free radical scavenging capacity, so that the redox balance in a plant body is more efficiently maintained. The carbon quantum dots can improve the photosynthesis level, the membrane lipid stability and the cell antioxidant system activity of plants in a saline-alkali environment in a foliage spraying manner on the premise of not changing the plant gene background, and show excellent environmental adaptability and physiological regulation ability.

Description

Technical Field

[0001] This invention relates to a highly conjugated biomass carbon quantum dot, specifically to a highly conjugated biomass carbon quantum dot, its preparation method, and its applications. Background Technology

[0002] To address the physiological damage to crops caused by salt and alkali stress, carbon quantum dots (CDs) have been widely studied in recent years due to their excellent optical properties, electron transport capabilities, and biocompatibility. Carbon quantum dots can enhance plant stress resistance by scavenging excess reactive oxygen species, promoting photosynthetic system stability, and increasing antioxidant enzyme activity. However, traditionally prepared carbon quantum dots have limited conjugation in their structure and low energy transfer efficiency, resulting in unstable antioxidant effects in plant systems. Furthermore, existing synthesis methods often rely on high-temperature pyrolysis or chemical oxidation processes, which are energy-intensive and polluting, hindering the promotion and application of green agriculture.

[0003] Therefore, researching a safe, controllable, and scalable method for applying highly conjugated carbon quantum dots is of great significance for improving plant tolerance to salt and alkali stress.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a highly conjugated biomass carbon quantum dot, its preparation method, and its application. This invention solves the problems of limited conjugation and low energy transfer efficiency of traditionally prepared carbon quantum dots. By pre-irradiating biomass materials and combining them with hydrothermal reaction technology, this invention successfully prepares carbon quantum dots with a highly conjugated structure. The highly conjugated biomass carbon quantum dots of this invention can significantly improve the antioxidant effect of carbon quantum dots in plant systems.

[0006] To achieve the above objectives, the present invention provides a method for preparing highly conjugated biomass carbon quantum dots, the method comprising: Biomass materials were pre-irradiated with an electron irradiation dose of 900-3600 kGy, and an aqueous solution was prepared using water. The solution was then subjected to a hydrothermal reaction. After the reaction was completed, the solution was cooled, centrifuged, and large particles were removed. The supernatant was then dialyzed using a 1000 Da dialysis bag. The solution in the dialysis bag was collected, freeze-dried, and highly conjugated biomass carbon quantum dots were obtained.

[0007] Preferably, the biomass material is selected from cellulose-rich crop by-products.

[0008] More preferably, the cellulose-rich crop by-product includes at least one of straw and rice husk.

[0009] Preferably, the hydrothermal reaction temperature is 180°C; or / and the centrifugation is performed at 8000 rpm for 40-50 min.

[0010] A second objective of this invention is to provide highly conjugated biomass carbon quantum dots obtained by the preparation method described above.

[0011] A third objective of this invention is to provide the application of the aforementioned highly conjugated biomass carbon quantum dots in improving the salt and alkali stress tolerance of crops.

[0012] Preferably, the concentration of the highly conjugated biomass carbon quantum dots is 100–300 mg / L; or / and the crops include: tomatoes, cucumbers, and soybeans.

[0013] Preferably, foliar spraying is used.

[0014] Preferably, spraying begins when the crop has five true leaves.

[0015] Preferably, the spraying involves uniformly spraying the front and back of the leaves 1 to 10 times, with an interval of 1 to 3 days between sprayings.

[0016] The highly conjugated biomass carbon quantum dots, their preparation method, and applications of this invention solve the problems of limited conjugation and low energy transfer efficiency of traditionally prepared carbon quantum dots, and have the following advantages: (1) The highly conjugated biomass carbon quantum dots of the present invention can significantly improve electron migration rate and free radical scavenging ability by enhancing the proportion of sp² carbon in the carbon skeleton and the π electron delocalization effect, thereby maintaining the redox balance in plants more efficiently. These carbon quantum dots can improve the photosynthetic level, membrane lipid stability and cellular antioxidant system activity of plants in saline-alkali environments by foliar spraying without changing the plant's genetic background, demonstrating excellent environmental adaptability and physiological regulation ability;

[0017] (2) The high conjugated biomass carbon quantum dots (B-CDs) of the present invention can be applied under normal temperature conditions to improve the plant's tolerance to salt and alkali stress. Through exogenous application, it can promote the activation of the antioxidant enzyme system and the removal of reactive oxygen species (ROS) in the plant, increase the activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), reduce the content of ROS and malondialdehyde (MDA), improve the antioxidant capacity of crops, thereby reducing cell membrane damage caused by salt and alkali stress, improving photosynthetic efficiency and improving physiological state. (3) The method of the present invention is simple to operate and environmentally friendly. By controlling the concentration and frequency of carbon quantum dot application, the stress resistance of plants can be controlled and enhanced, providing an efficient, universal and scalable technical approach for the production of crops in saline-alkali land. Attached Figure Description

[0018] Figure 1 The images show the FTIR spectra of the highly conjugated biomass carbon quantum dots prepared in Example 1 of this invention and the unirradiated carbon quantum dots prepared in Comparative Example 1.

[0019] Figure 2 Fluorescence spectra of highly conjugated biomass carbon quantum dots prepared in Example 1 of the present invention and carbon quantum dots prepared in Comparative Example 1 without irradiation.

[0020] Figure 3 The images show the XRD patterns of the highly conjugated biomass carbon quantum dots prepared in Example 2 of this invention and the unirradiated carbon quantum dots prepared in Comparative Example 1.

[0021] Figure 4 XPS images of highly conjugated biomass carbon quantum dots prepared in Example 2 of the present invention and carbon quantum dots prepared in Comparative Example 1 without irradiation.

[0022] Figure 5 XPS images of highly conjugated biomass carbon quantum dots prepared in Example 3 of the present invention and carbon quantum dots prepared in Comparative Example 1 without irradiation.

[0023] Figure 6 The images show the FTIR spectra of carbon quantum dots prepared in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0024] Figure 7 The effect of carbon quantum dots on the SOD activity of tomatoes after salt and alkali stress treatment is shown in Example 1 and Comparative Example 1 of this invention.

[0025] Figure 8 The effect of carbon quantum dots on the SOD activity of tomatoes after salt and alkali stress treatment is shown in Example 1 and Comparative Example 1 of this invention.

[0026] Figure 9 The effect of carbon quantum dots on the POD activity of tomatoes after salt and alkali stress treatment is shown in Example 2 and Comparative Example 1 of this invention.

[0027] Figure 10 The carbon quantum dots in Example 3 of this invention enhance the resistance of tomatoes to singlet oxygen after salt and alkali stress treatment. 1 The effects of O2.

[0028] Figure 11 The following are phenotypic diagrams of tomatoes before salt-alkali stress treatment in Example 2 of the present invention: (a) control group; (b) carbon quantum dot solution treatment group.

[0029] Figure 12 The following are phenotypic diagrams of tomatoes after salt-alkali stress treatment in Example 2 of the present invention: (a) control group; (b) carbon quantum dot solution treatment group.

[0030] Figure 13 The SOD activity of the control group and the B-CDs-treated group was measured after 10 days of treatment in Application Example 2 of this invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that: Unless otherwise specified in the examples, conditions should be followed according to standard conditions or the manufacturer's recommendations. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0033] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0034] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0035] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] This invention provides a highly conjugated biomass carbon quantum dot using biomass materials as the carbon source. During the preparation process, it was discovered that the electron irradiation dose plays a crucial role. When the electron irradiation dose is in the range of 900–3600 kGy, it indicates that a suitable amount of surface defect states (such as C=O and CN) may be induced at a moderate dose, exhibiting optimal electronic transition matching. When the electron irradiation dose is below 900 kGy, it is impossible to achieve a balance between a high C=O ratio and adequate preservation of the crystalline structure. When the electron irradiation dose is greater than 3600 kGy, the high dose of irradiation leads to structural damage and high synthesis costs.

[0037] This invention successfully constructed biomass carbon quantum dots with a highly conjugated structure through electron irradiation combined with hydrothermal reaction and dialysis. Furthermore, the inventors discovered that the highly conjugated biomass carbon quantum dots prepared in this invention exhibit significant effects in improving the salt-alkali stress tolerance of crops. Through foliar spraying, these carbon quantum dots can be rapidly absorbed by plant leaves and transported to various parts of the plant. Under salt-alkali stress conditions, utilizing the excellent electron delocalization properties and surface-active groups in the highly conjugated carbon quantum dot structure, exogenous application promotes the activation of antioxidant enzyme systems and the scavenging of reactive oxygen species (ROS) in plants. This increases the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), reduces the content of ROS and malondialdehyde (MDA), and enhances the antioxidant capacity of crops, thereby mitigating cell membrane damage caused by salt-alkali stress, improving photosynthetic efficiency, and improving physiological state.

[0038] The following examples provide a detailed description of the highly conjugated biomass carbon quantum dots, their preparation method, and applications provided by this invention.

[0039] Example 1 A highly conjugated biomass carbon quantum dot, the preparation method of which includes the following steps: (1) After crushing the straw, pre-irradiate it with an electron irradiation dose of 900 kGy. Then take 5g of the straw, add it to 100 mL of deionized water, stir evenly, and then put it into a polytetrafluoroethylene reactor.

[0040] (2) After heating the reaction in an oven at 180 °C for 5 h, remove and cool. After cooling, open the reaction vessel, pour out the solution and centrifuge at 8000 rpm for 45 min to remove large particles. After removing large particles, dialyze the remaining supernatant with a 1000 Da dialysis bag for 12 h. Finally, collect the solution in the dialysis bag and freeze-dry it to obtain highly conjugated biomass carbon quantum dots, denoted as B-CDs-1.

[0041] Example 2 A highly conjugated biomass carbon quantum dot is prepared using a method essentially the same as in Example 1, with the difference being: In step (1), the electron irradiation dose is 3600 kGy.

[0042] The highly conjugated biomass carbon quantum dots prepared in this embodiment are designated as B-CDs-2.

[0043] Example 3 A highly conjugated biomass carbon quantum dot is prepared using a method essentially the same as in Example 1, with the difference being: In step (1), the electron irradiation dose is 2700 kGy.

[0044] The highly conjugated biomass carbon quantum dots prepared in this embodiment are designated as B-CDs-3.

[0045] Example 4 A highly conjugated biomass carbon quantum dot is prepared using a method essentially the same as in Example 1, with the difference being: In step (1), the electron irradiation dose is 1800 kGy.

[0046] The highly conjugated biomass carbon quantum dots prepared in this embodiment are designated as B-CDs-4.

[0047] Comparative Example 1 The traditional hydrothermal method for synthesizing carbon quantum dots involves the following steps: (1) After thoroughly crushing the straw, take 5 g and place it in 100 mL of deionized water; (2) The above solution was placed in a 150 mL polytetrafluoroethylene-lined reactor and heated in an oven at 180 °C for 5 h. After cooling, the reactor was opened, the solution was poured out and centrifuged at 8000 rpm for 45 min to remove large particles. After removing large particles, the supernatant was dialyzed with a 1000 Da dialysis bag for 12 h. Finally, the solution in the dialysis bag was collected and freeze-dried to obtain carbon quantum dots.

[0048] Comparative Example 2 A conjugated biomass carbon quantum dot, whose preparation method is basically the same as in Example 1, with the difference being: In step (1), the electron irradiation dose is 450 kGy.

[0049] The yoke biomass carbon quantum dots prepared in this embodiment are designated as B-CDs-5.

[0050] Experimental Example 1: Characterization of Carbon Quantum Dot Structure The carbon quantum dots prepared in Examples 1-4 and Comparative Examples 1-2 of this invention were structurally characterized, and the results are shown in [reference needed]. Figures 1-5 .

[0051] like Figure 1 The image shows the FTIR spectra of highly conjugated biomass carbon quantum dots prepared by 900 kGy electron irradiation in Example 1 of this invention and carbon quantum dots prepared without irradiation in Comparative Example 1. It can be seen that compared with carbon quantum dots synthesized by conventional hydrothermal methods at 0 kGy, the FTIR spectra of highly conjugated biomass carbon quantum dots prepared by 900 kGy electron irradiation in Example 1 are significantly higher. −1 The narrow band represents the stretching vibrations of C=O shifting to lower wavenumbers, and a 1730 cm⁻¹ band appears in the FTIR plot under 900 kGy irradiation. −1 (CO) and 1375 cm −1 The (C=O) new peak indicates that the hydrophilic groups and conjugation of irradiated carbon quantum dots have increased, giving them excellent biocompatibility.

[0052] like Figure 2 The image shows the fluorescence spectra of highly conjugated biomass carbon quantum dots prepared by 900 kGy electron irradiation in Example 1 of this invention and carbon quantum dots prepared by unirradiated method in Comparative Example 1. It can be seen that the fluorescence intensity of the carbon quantum dots synthesized by both methods reaches its peak when the excitation wavelength is near 400 nm, and the carbon quantum dots obtained by 900 kGy pre-irradiation exhibit significantly stronger fluorescence characteristics than those of carbon quantum dot materials synthesized by conventional hydrothermal methods.

[0053] like Figure 3 The figure shows the XRD patterns of highly conjugated biomass carbon quantum dots prepared by 3600 kGy electron irradiation in Example 2 of this invention and carbon quantum dots prepared without irradiation in Comparative Example 1. It can be seen that, compared with carbon quantum dots synthesized by conventional hydrothermal methods at 0 kGy, the carbon quantum dots pretreated with 3600 kGy electron beam irradiation show a weaker peak intensity at 20.1° due to the lack of long-range ordered lattice arrangement. This indicates that the 3600 kGy electron beam irradiation rapidly carbonizes the straw powder, resulting in the carbon cores of the carbon quantum dots being predominantly sp³-C hybridized, and an increase in defect structures.

[0054] like Figure 4 The figure shows the XPS images of highly conjugated biomass carbon quantum dots prepared by 3600 kGy electron irradiation in Example 2 of this invention and carbon quantum dots prepared by unirradiated control in Comparative Example 1. It can be seen that the CC and CO contents of the carbon quantum dots synthesized by irradiation treatment increase, and the absorption peaks at 284.9 eV and 286.6 eV shift significantly towards higher binding energies, indicating that the formed oxygen-containing functional groups can enhance the interfacial reactivity of the material.

[0055] like Figure 5The figure shows XPS images of highly conjugated biomass carbon quantum dots prepared by 2700 kGy electron irradiation in Example 3 of this invention and carbon quantum dots prepared by unirradiated method in Comparative Example 1. It can be seen that, compared with the traditional hydrothermal method, the C=O content of the irradiated carbon quantum dots gradually increases, and the binding energy also increases, indicating that the formed oxygen-containing functional groups enhance the reactivity of the material.

[0056] like Figure 6 The figures shown are the FTIR spectra of carbon quantum dots prepared in Examples 1-4 and Comparative Examples 1-2 of this invention. It can be seen that the infrared absorption spectra of the carbon quantum dots changed significantly with increasing irradiation dose, indicating that their surface chemical structure was induced and regulated by the irradiation dose. Under low-dose irradiation conditions, the overall morphological changes in the sample spectra were small, with only a slight enhancement of O–H stretching vibration absorption (approximately 3200-3600 cm⁻¹) appearing in the high wavenumber region. -1 This indicates that a small number of oxygen-containing functional groups are mainly introduced in the initial stage of irradiation. As the irradiation dose further increases, the carbonyl C=O absorption peak (approximately 1650-1750 cm⁻¹) is observed. -1 The vibrational peaks were significantly enhanced, while the C–O / C–O–C vibrational peaks (approximately 1000-1300 cm⁻¹) were also significantly enhanced. -1 The increasing intensity of the peaks indicates that the irradiation process promoted the oxidation reaction on the surface of carbon quantum dots, generating oxygen-containing functional groups such as ketones, carboxylic acids, or esters. Simultaneously, the C–H stretching vibration peaks of hydrocarbon groups (approximately 2850-2960 cm⁻¹) gradually increased. -1 The relative weakening indicates that some C–H bonds break and are replaced by oxygen-containing groups under irradiation. These results demonstrate that increasing the irradiation dose effectively modulates the functional group composition of carbon quantum dots, gradually transforming them from a relatively hydrophobic carbon framework to a structure rich in oxygen functional groups. This change is beneficial for improving the surface activity of carbon quantum dots and their subsequent optical and interfacial properties.

[0057] Application Example 1 The carbon quantum dots prepared in Examples 1-4 and Comparative Examples 1-2 of this invention were applied to improve the salt and alkali stress tolerance of tomatoes. The specific experimental process is as follows: The carbon quantum dots prepared in Examples 1-4 and Comparative Examples 1-2 of this invention were dissolved in deionized water to prepare corresponding 200 mg / L solutions, which were then used for foliar spraying of tomatoes. The specific treatment was as follows: (1) The carbon quantum dot solutions of Example 1 and Comparative Example 1 were sprayed on crops at the five true leaf stage, once a day for 10 consecutive times. After that, salt and alkali resistance treatment was carried out. A mixed salt and alkali solution of 300 mmol / L pH 8.90 was used. The mixed salt and alkali solution contained NaCl, Na2SO4, NaHCO3 and Na2CO3, and the mass ratio of NaCl, Na2SO4, NaHCO3 and Na2CO3 was 1:9:9:1. (2) The carbon quantum dot solutions prepared in Examples 2, 3 and Comparative Example 1 were sprayed on crops at the five true leaf stage, once every 2 days, for 4 consecutive times. Then, salt and alkali stress treatment was carried out using a 300 mmol / L mixed salt and alkali solution with a pH of 8.90. The mixed salt and alkali solution contained NaCl, Na2SO4, NaHCO3 and Na2CO3, and the mass ratio of NaCl, Na2SO4, NaHCO3 and Na2CO3 was 1:9:9:1.

[0058] To further investigate the effects of carbon quantum dot solutions of different concentrations, the highly conjugated biomass carbon quantum dots from Example 3 were prepared at concentrations of 200 mg / L and 300 mg / L, and the above experimental procedures were carried out.

[0059] Determining SOD and POD activity, and eliminating 1 O2 radical ability (using electron paramagnetic resonance), results are shown in [link to results]. Figures 7-10 .

[0060] like Figure 7 As shown, the carbon quantum dots of Example 1 and Comparative Example 1 of this invention have an effect on the SOD activity of tomatoes after salt-alkali stress treatment. Spraying with highly conjugated biomass carbon quantum dots (the carbon quantum dots of Example 1 of this invention) significantly increased the SOD activity of tomato leaves and enhanced their antioxidant capacity. The SOD activity using highly conjugated biomass carbon quantum dots (2784.97 U / g FW, 900 kGy) was 8.24% higher than the SOD activity using 0 kGy (2573.07 U / g FW).

[0061] like Figure 8 The figure shows the effect of carbon quantum dots (CQDs) from Examples 2-4 and Comparative Examples 1-2 of this invention on the SOD activity of tomatoes after salt-alkali stress treatment. As can be seen from the figure, the superoxide dismutase (SOD) activity of the B-CDs obtained after pre-irradiation is significantly increased. Furthermore, with increasing irradiation dose, the SOD activity of the B-CDs first increases and then decreases, reaching its optimal value at 2700 kGy.

[0062] like Figure 9 As shown, the carbon quantum dots of Example 2 and Comparative Example 1 of the present invention have an effect on the POD activity of tomatoes after salt and alkali stress treatment. After spraying with highly conjugated biomass carbon quantum dots, the POD activity of tomato leaves was significantly increased and the antioxidant capacity was enhanced.

[0063] like Figure 10 As shown in Example 3 of this invention, carbon quantum dots enhance the resistance of tomatoes to singlet oxygen after salt and alkali stress treatment. 1The effect of O2 (TEMP in the figure represents the oxygen free radical scavenger 2,2,6,6-tetramethylpiperidine) shows that adding different concentrations of carbon quantum dot solution results in a significant decrease in signal intensity, indicating that... 1 O2 is eliminated by B-CDs, and by a 200 mg / L carbon quantum dot solution. 1 O2 has the strongest effect.

[0064] Application Example 2 To verify the potential of carbon quantum dots prepared by pre-irradiation at 2700 kGy, which has the highest SOD activity, in improving the salt and alkali stress tolerance of tomatoes, the following experiments were conducted: Tomato plants were subjected to salt-alkali stress treatment by watering them every two days with 50 mL of a 300 mmol / L mixed saline-alkali solution (NaCl, Na₂SO₄, NaHCO₃, and Na₂CO₃ in a mass ratio of 1:9:9:1). The leaves of the treatment group were sprayed daily with 2700 kGy of carbon quantum dot solution, while the control group (CK) was sprayed with water. After 10 days of treatment, the phenotypic results are as follows: Figure 11 and Figure 12 As shown, SOD activity was measured.

[0065] like Figure 11 and Figure 12 The figures show the phenotypic diagrams of tomatoes before and after salt-alkali stress treatment. The growth of the control group and the carbon quantum dot solution treatment group was similar at day 0. After 10 days of salt-alkali treatment, the control group showed obvious wilting, while the carbon quantum dot solution treatment group showed good growth.

[0066] like Figure 13 The figure shows the SOD activity of the control group and the B-CDs-treated group after 10 days of treatment. Salt-alkali stress can cause an increase in reactive oxygen species levels in plants, leading to cell membrane lipid peroxidation, protein denaturation, or DNA damage, thereby inhibiting plant growth. This result indicates that under salt-alkali stress, the leaves of tomato seedlings in the B-CDs-treated group showed increased SOD levels compared to the control group. Spraying with B-CDs has a maintaining effect on the antioxidant enzyme activity of tomato leaves, which is beneficial to plant growth.

[0067] In summary, the carbon quantum dots prepared by this invention using different electron irradiation doses exhibit unique advantages in structural characterization, including increased hydrophilic groups, enhanced conjugation, and improved fluorescence properties. The highly conjugated biomass carbon quantum dots of this invention have a significant effect on improving the salt and alkali stress tolerance of crops and have broad application prospects in agriculture, especially in the production of crops in saline-alkali land.

[0068] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing highly conjugated biomass carbon quantum dots, characterized in that, The method includes: Biomass materials were pre-irradiated with an electron irradiation dose of 900~3600 kGy, and an aqueous solution was prepared using water, followed by a hydrothermal reaction. After the reaction is complete, the mixture is cooled, centrifuged to remove large particles, and then the supernatant is dialyzed using a 1000 Da dialysis bag. The solution in the dialysis bag is collected, freeze-dried, and highly conjugated biomass carbon quantum dots are obtained.

2. The preparation method according to claim 1, characterized in that, The biomass material is selected from cellulose-rich crop by-products.

3. The preparation method according to claim 2, characterized in that, The cellulose-rich crop by-products include at least one of straw and rice husks.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The temperature of the hydrothermal reaction is 180°C; Or / and, the centrifugation is performed at 8000 rpm for 40-50 min.

5. Highly conjugated biomass carbon quantum dots obtained by the preparation method according to any one of claims 1 to 4.

6. The application of highly conjugated biomass carbon quantum dots as described in claim 5 in improving crop tolerance to salt and alkali stress.

7. The application according to claim 6, characterized in that, The concentration of the highly conjugated biomass carbon quantum dots is 100–300 mg / L; Or / and, the crops include: tomatoes, cucumbers and soybeans.

8. The application according to claim 6, characterized in that, Foliar spraying is used.

9. The application according to claim 6, characterized in that, Spraying should begin when the crop has five true leaves.

10. The application according to claim 8 or 9, characterized in that, The spraying involves spraying the front and back of the leaves evenly 1 to 10 times, with an interval of 1 to 3 days between sprayings.

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