Application of fluorine-doped carbon quantum dots in improvement of salt stress of cotton

Abstract

The invention discloses application of fluorine-doped carbon quantum dots in improvement of salt stress of cotton. The average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm. Research finds that the fluorine-doped carbon quantum dots can significantly improve the growth condition of cotton under the salt stress condition and improve the dry weight and fresh weight of cotton; in addition, the activity of SOD and CAT in the cotton body can be remarkably improved, the ROS content, the Pro content and the MDA content are remarkably reduced, and it is indicated that the fluorine-doped carbon quantum dots can remarkably improve the salt stress of the cotton.

Description

Technical Field

[0001] This invention belongs to the technical field of agriculture, specifically relating to the application of fluorine-doped carbon quantum dots in improving the salt stress response of cotton. Background Technology

[0002] Soil salinization is prone to occur in arid and semi-arid regions, leading to the accumulation of large amounts of salt in the soil. The high salt content in the soil after salinization reduces the plant's ability to absorb water, resulting in lower crop yields. It also affects the formation of nutrients in crops, thus reducing the quality of agricultural products. Therefore, improving the salt tolerance of crops during the seedling stage and maintaining their healthy vegetative growth is crucial.

[0003] Patent publication number CN116868721A discloses a method for improving the salt tolerance of cotton seeds, which involves immersing cotton seeds in a carbon quantum dot solution under light-protected conditions. This method is simple, efficient, and inexpensive, and can improve the germination and growth of cotton seeds under salt stress. However, the improvement in the salt stress effect on cotton described in the above patent is limited and cannot meet the needs of practical applications. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the primary objective of this invention is to provide the application of fluorine-doped carbon quantum dots in improving the salt stress of cotton. By applying fluorine-doped carbon quantum dots to cotton, it is possible to better remove excess reactive oxygen species in cotton, alleviate the salt stress suffered by cotton, and improve the growth and development of cotton.

[0005] A second objective of this invention is to provide the application of fluorine-doped carbon quantum dots in improving the antioxidant properties of cotton.

[0006] A third objective of this invention is to provide the application of fluorine-doped carbon quantum dots in increasing the dry or fresh weight of cotton.

[0007] The fourth objective of this invention is to provide a method for improving the salt stress resistance of cotton.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention seeks to protect the application of fluorine-doped carbon quantum dots in improving the salt stress response of cotton, wherein the average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

[0009] This invention utilizes carbon quantum dots and fluorine-doped carbon quantum dots in experiments on cotton salt stress tolerance. The study found that fluorine-doped carbon quantum dots significantly improved cotton growth under salt stress conditions. Cotton treated with fluorine-doped carbon quantum dots showed better growth, while cotton treated with carbon quantum dots exhibited yellowing and even wilting leaves. In terms of dry weight and fresh weight growth, fluorine-doped carbon quantum dots significantly outperformed both the control and carbon quantum dot groups, demonstrating significant differences. Furthermore, the inventors discovered that fluorine-doped carbon quantum dots significantly increased the activities of superoxide dismutase (SOD) and catalase (CAT) in cotton, while significantly reducing the contents of reactive oxygen species (ROS), proline (Pro), and malondialdehyde (MDA). This indicates that fluorine-doped carbon quantum dots significantly enhance the antioxidant capacity of cotton and improve its salt stress tolerance, showing a significant difference compared to carbon quantum dots. Moreover, the inventors found that when the fluorine-doped carbon quantum dots are large, they cannot be applied to subsequent cotton salt stress experiments and cannot be absorbed by the cotton.

[0010] Preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-5 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-2 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1.5-1.6 nm.

[0011] Preferably, the preparation method of the fluorine-doped carbon quantum dots includes the following steps: mixing and dissolving citric acid, a nitrogen source and a fluoride salt, carrying out a hydrothermal reaction at 170-190°C, dialysis purification, and obtaining the fluorine-doped carbon quantum dots.

[0012] Preferably, the fluoride salt is selected from one or more of sodium fluoride and ammonium fluoride.

[0013] Preferably, the hydrothermal reaction time is 10.5-11.5 hours. More preferably, the hydrothermal reaction is carried out at 175-185°C for 11 hours. More preferably, the hydrothermal reaction is carried out at 180°C for 11 hours.

[0014] Specifically, it enhances salt stress in cotton by scavenging reactive oxygen species.

[0015] Preferably, the cotton leaves are treated with a fluorine-doped carbon quantum dot solution with a concentration of 80-120 mg / L. More specifically, the concentration of the fluorine-doped carbon quantum dots is 95-105 mg / L. More specifically, the fluorine-doped carbon quantum dot solution is applied to the surface of the cotton leaves for treatment.

[0016] Furthermore, this invention claims protection for the application of fluorine-doped carbon quantum dots in improving the antioxidant properties of cotton, wherein the average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

[0017] Preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-5 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-2 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1.5-1.6 nm.

[0018] Preferably, improving the antioxidant properties of cotton means scavenging at least one of hydrogen peroxide, hydroxyl radicals, and superoxide anion radicals.

[0019] Furthermore, the present invention claims protection for the application of fluorine-doped carbon quantum dots in increasing the dry or fresh weight of cotton, wherein the average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

[0020] Preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-5 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1-2 nm. More preferably, the average particle size of the fluorine-doped carbon quantum dots is 1.5-1.6 nm.

[0021] Furthermore, the present invention claims protection for a method for improving the salt stress resistance of cotton, which involves treating cotton leaves with fluorine-doped carbon quantum dots, wherein the average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

[0022] More specifically, treating cotton leaves with fluorine-doped carbon quantum dots means uniformly coating the surface of cotton leaves with fluorine-doped carbon quantum dots.

[0023] Compared with the prior art, the present invention has the following beneficial effects: This invention has found that applying fluorine-doped carbon quantum dots to cotton can significantly improve the growth of cotton under salt stress, and increase the dry weight and fresh weight of cotton. In addition, it can significantly increase the activity of SOD and CAT in cotton, and significantly reduce the content of ROS, Pro and MDA. This indicates that fluorine-doped carbon quantum dots can significantly improve cotton under salt stress, and have significant differences compared with carbon quantum dots. Attached Figure Description

[0024] Figure 1 TEM images and particle size distribution maps of CDs and F-CDs are shown; among them, Figure 1 a) and c) in the figure are the TEM image and particle size distribution map of CDs, respectively. Figure 1 b) and d) in the figure are TEM images and particle size distribution maps of F-CDs, respectively.

[0025] Figure 2 and Figure 3 The images show TEM images of fluorine-doped carbon quantum dots synthesized in Comparative Examples 2 and 3, respectively.

[0026] Figure 4The images show the ultraviolet (black line), excitation (blue line), and emission (red line) spectra of CDs and F-CDs, as well as the emission spectra of F-CDs at different excitation wavelengths; among them, Figure 4 a) in the figure is the UV, excitation, and emission spectrum of CDs. Figure 4 b) in the figure shows the ultraviolet, excitation, and emission spectra of F-CDs. Figure 4 c) in the figure represents the emission spectra of F-CDs at different excitation wavelengths.

[0027] Figure 5 XRD patterns of CDs and F-CDs, and FT-IR and XPS plots of F-CDs; among which, Figure 5 a) and b) in the figure are XRD patterns of CDs and F-CDs, respectively. Figure 5 c) and d) are the FT-IR and XPS plots of F-CDs, respectively.

[0028] Figure 6 High-resolution XPS spectra of C1s, N1s, O1s, and F1s in F-CDs; among which, Figure 6 a) to d) are high-resolution XPS spectra of C1s, N1s, O1s, and F1s, respectively.

[0029] Figure 7 Top-view images showing the phenotypic distribution of cotton plants treated with different concentrations of F-CDs and the control group after 5 days of salt stress, as well as the fresh and dry weight of the cotton; among them, Figure 7 In the figure, A and B represent the fresh weight and dry weight of cotton plants treated with different concentrations of F-CDs and the control group, respectively.

[0030] Figure 8 Top-view images showing the phenotypic characteristics of cotton plants after 5 days of salt stress, including the control group, CDs-treated plants, and F-CDs-treated plants, as well as the dry and fresh weights of cotton plants in different groups; among them, Figure 8 a) and b) in the figure are top views of the phenotypic characteristics of cotton plants treated with control group, CDs and F-CDs, respectively. Figure 8 c) and d) in the figure represent the dry and fresh weights of cotton in the control group, CDs, and F-CDs.

[0031] Figure 9 This is a schematic diagram showing the H2O2 and O2·- content in cotton plants treated with CDs and F-CDs after 5 days of salt stress; among them, Figure 9 In the figure, a) represents the H2O2 content of cotton plants in the control group, CDs treatment, and F-CDs treatment after 5 days of salt stress. Figure 9 b) represents the O2·- content of cotton plants in the control group, CDs, and F-CDs treatments after 5 days of salt stress.

[0032] Figure 10The effects of salt stress on the activities of the control group, CDs, and F-CDs after 5 days of treatment on SOD, POD, and CAT; among them, Figure 10 In the figure, A represents the effect of the control group, CDs, and F-CDs on SOD activity after 5 days of salt stress. Figure 10 In the figure, B represents the effect of the control group, CDs, and F-CDs on POD activity after 5 days of salt stress. Figure 10 In the figure, C represents the effect of the control group, CDs, and F-CDs on CAT activity after 5 days of salt stress.

[0033] Figure 11 The effects of salt stress on Pro and MDA levels were compared between the control group, CDs, and F-CDs after 5 days of treatment. Figure 11 In the figure, A represents the effect of the control group, CDs, and F-CDs on Pro content after 5 days of salt stress. Figure 11 In the figure, B represents the effect of the control group, CDs, and F-CDs on MDA content after 5 days of salt stress. Detailed Implementation

[0034] The present invention will be further described below with reference to the specification and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0035] The specific testing method used in this invention is shown below.

[0036] (1) The size and morphology of CDs and F-CDs were observed using a transmission electron microscope (TEM); the UV-Vis absorption spectra and fluorescence spectra of CDs and FCDs were obtained using a UV-2450 ultraviolet-visible (UV-Vis) spectrophotometer and an RF-6000 fluorescence spectrophotometer, respectively; the structure and functional groups of F-CDs were analyzed using a Fourier transform infrared spectroscopy (FT-IR) instrument; the crystal structure of CDs and F-CDs was detected using an X-ray diffraction (XRD) instrument; the elemental composition and proportion of F-CDs were analyzed using an X-ray photoelectron spectroscopy (XPS) instrument; and the particle size distribution of carbon quantum dots was analyzed using a Nano Measurer.

[0037] (2) The method for determining the dry weight and fresh weight of cotton plants is as follows: After 5 days of salt stress treatment, the hydroponic nutrient solution at the roots of the cotton plants is wiped dry, and the mass is measured using an analytical balance and recorded as fresh weight (FW). The plant samples are dried in an 80 ℃ oven until constant weight, and after cooling to room temperature, their dry weight (DW) is measured.

[0038] (3) Determination of ROS content in cotton plants—Reagent kit method. The specific operation is as follows: The reagent kit used for the determination of hydrogen peroxide (H2O2) content is the "Hydrogen Peroxide Test Kit" (A064-1-1, Nanjing Jiancheng). The experimental method is performed according to the steps in the instruction manual. Specifically, 0.05 g of fresh cotton true leaf sample was weighed into a grinding tube, and a steel ball and 1 mL of extraction solution were added. The sample was ground for 180 sec (65 Hz) using a grinder. After grinding, the sample was centrifuged at 12000 r / min and 4 ℃ for 20 min using a refrigerated centrifuge. The supernatant was collected and kept on ice for later use. The sample and reagents were added according to the procedure and reagent dosage in the instruction manual. After mixing, the absorbance value at a wavelength of 405 nm was measured using an ELISA reader. The H2O2 content in cotton true leaves was calculated according to the formula in the kit instruction manual. Each treatment was performed in triplicate.

[0039] The kit used for superoxide anion (O2·-) content determination was the "Superoxide Anion Content Detection Kit" (BC1295, Solarbio). The experimental method was performed according to the instructions. Sample pretreatment was the same as for H2O2 content determination; the supernatant of the sample extract after grinding and freezing centrifugation was placed on ice for later use. Samples and reagents were added according to the instructions and reagent dosages, and a standard curve was prepared. After mixing, the absorbance was measured at 530 nm using a microplate reader. A standard curve was plotted, and the measured absorbance values ​​were substituted into the standard curve and the formula described in the instructions to calculate the O2·- content in cotton true leaves. Each treatment was performed in triplicate.

[0040] (4) Determination of antioxidant enzyme activity in cotton plants The pretreatment method for fresh cotton true leaf samples is as follows: Weigh 0.05 g of sample into a grinding tube and add 1 mL of 100 mmol / L sodium phosphate buffer (PBS) at pH = 7.8. Grind for 180 sec (65 Hz) using a grinder, then centrifuge at 4000 r / min and 4 ℃ for 10 min using a refrigerated centrifuge. Collect the supernatant and store it on ice for later use; the supernatant is the enzyme extraction solution. Each treatment group was performed in triplicate for sample pretreatment.

[0041] The method for determining superoxide dismutase (SOD) activity is as follows: Add 750 μL of 100 mmol / L PBS, 150 μL of 130 mmol / L methionine solution, 150 μL of 750 μmol / L ammonia-tetrazole solution, 150 μL of 20 μmol / L riboflavin solution, and 150 μL of 100 μmol / L EDTA-Na2 solution to a 2 mL centrifuge tube (one control tube and one blank tube are required). Then add 25 μL of enzyme extraction buffer (the same volume of PBS is added to both the control and blank tubes as a substitute). Finally, add 125 μL of UP water to make the total solution volume 1.5 mL. After mixing, place the blank tube in the dark, and place all other tubes under 4000 Lx light for 20 min. Measure the absorbance at 560 nm using a microplate reader. The formula for calculating SOD activity is shown below: SOD activity (U·g) -1 = (A pairs - A samples) * VT / [0.5 * (A pairs - A empty) * W * Vs] In the formula, A_pair is the absorbance value of the control tube, A_sample is the absorbance value of the sample tube, VT is the total volume of the added extract (μL), Vs is the volume of the enzyme extract added to the sample tube (μL), and W is the mass of the fresh leaf sample (g).

[0042] The method for determining peroxidase (POD) activity is as follows. Add 580 μL of 100 mmol / L PBS, 20 μL of enzyme extraction buffer (the control tube should be boiled for 5 min after adding the enzyme extraction buffer), 200 μL of 100 mmol / L H2O2, and 200 μL of guaiacol to a 2 mL centrifuge tube (one control tube is required). After all the solutions have been added, mix well and incubate in a water bath at 37 ℃ for 15 min. After the time is up, immediately transfer to an ice bath and add 0.5 mL of 20% trichloroacetic acid to terminate the reaction. Centrifuge at 5000 r / min for 10 min, collect the supernatant, and measure the absorbance at 470 nm using a microplate reader. The formula for calculating POD activity is shown below.

[0043] POD activity (U·g) -1 ·min -1 = (A sample - A pair) * VT / (W * Vs * 0.01 * 15) In the formula, A_pair is the absorbance value of the control tube, A_sample is the absorbance value of the sample tube, VT is the total volume of the added extract (μL), Vs is the volume of the enzyme extract added to the sample tube (μL), and W is the mass of the fresh leaf sample (g).

[0044] The method for determining catalase (CAT) activity is as follows. Prepare the reaction solution in advance by adding 2.1 mL of 100 mmol / L PBS and 0.9 mL of 100 mmol / L H₂O₂ to a 5 mL centrifuge tube and mixing well. Take 100 μL of the above reaction solution and add 10 μL of enzyme extraction buffer. Measure the absorbance of this mixture at 240 nm using a UV-Vis spectrophotometer. Measure for 90 seconds, reading every 30 seconds. The formula for calculating CAT activity is shown below.

[0045] CAT activity (U·g) -1 ·min -1 )=ΔA240* VT / (W * Vs *0.1*t) In the formula, ΔA240 is the change in absorbance at 240 nm during the reaction time, VT is the total volume of the added extract (μL), Vs is the volume of the enzyme extract added to the sample tube (μL), W is the mass of the fresh leaf sample (g), and t is the reaction time (min).

[0046] (5) Determination of proline content in cotton plants The method for determining proline (Pro) content is as follows: Weigh 0.05 g of fresh cotton true leaf sample into a centrifuge tube, add 1 mL of 3% sulfosalicylic acid solution, extract in a boiling water bath for 10 min, take 200 μL of supernatant, add 200 μL of glacial acetic acid and 200 μL of acidic ninhydrin, and boil in a water bath again for 30 min. At this point, the solution turns red. After cooling to room temperature, add 400 μL of toluene, shake, and let stand. After the solution separates into layers, take the supernatant and measure the absorbance at 520 nm using a microplate reader. Each treatment was performed in triplicate.

[0047] The method for plotting the Pro standard curve is as follows: Dissolve 25 mg of proline in 250 mL of UP water to obtain a 100 μg / mL Pro stock solution, then dilute it to Pro standard solutions with concentrations of 1, 2, 3, 4, and 5 μg / mL. The subsequent steps are the same as described above. The formula for calculating Pro is shown below.

[0048] Pro content (%) in sample = 100% * x * VT / (W * Vs * 10) 6 ) In the formula, x is the concentration of Pro in the sample obtained through the standard curve, VT is the total volume of the added extract (μL), Vs is the volume of the added extract in the sample tube (μL), and W is the mass of the fresh leaf sample (g).

[0049] (6) Determination of malondialdehyde content in cotton plants The method for determining malondialdehyde (MDA) content is as follows: Weigh 0.05 g of fresh cotton true leaf sample into a grinding tube, add 1.5 mL of 5% trichloroacetic acid, grind using a grinder for 180 sec (65 Hz), and then centrifuge at 12000 r / min and 4 ℃ for 20 min. Take 1 mL of the supernatant, add 1 mL of 0.67% thiobarbituric acid solution, mix well, boil in a water bath for 30 min, cool, and centrifuge. Transfer the supernatant to an ELISA plate and measure the absorbance values ​​at 450 nm, 532 nm, and 600 nm. Each treatment was performed in triplicate. The formula for calculating MDA is shown below.

[0050] MDA content (μmol / g) = [6.45 * (A532 - A600) - 0.56 * A450] * VT * VR / (W * VS) In the formula, A532 is the absorbance value of the solution at 532 nm, A600 is the absorbance value of the solution at 600 nm, A450 is the absorbance value of the solution at 450 nm, VT is the total volume of the added extract (mL), VR is the total volume of the reaction solution (mL), VS is the volume of the added extract (mL), and W is the mass of the fresh leaf sample (g).

[0051] (7) Determination of the ability of carbon quantum dots to scavenge reactive oxygen species in vitro The ability of CDs and F-CDs to scavenge ROS in vitro was determined using a kit method.

[0052] (1) Determination of the ability of carbon quantum dots to scavenge H2O2 in vitro The reagent kit used for this determination was a "hydrogen peroxide test kit" (A064-1-1, Nanjing Jiancheng). The experimental method was performed in accordance with the instructions, with a slight modification: the extract added to the test tube was replaced with a carbon quantum dot solution of the optimal concentration.

[0053] (2) Determination of the ability of carbon quantum dots to scavenge O2·- in vitro The kit used for this assay was the "Superoxide Anion Scavenging Capacity Assay Kit" (BC1415, Solarbio). The experimental method was performed in accordance with the instructions.

[0054] (3) Determination of the ability of carbon quantum dots to scavenge hydroxyl radicals (·OH) in vitro The kit used for this assay was the "Hydroxy Radical Scavenging Ability Test Kit" (BC1325, Solarbio). The experimental method was performed in accordance with the instructions.

[0055] Example 1 0.2000 g citric acid monohydrate, 0.5000 g urea, and 0.1000 g sodium fluoride were ultrasonically dissolved in 20.0 mL of ultrapure water and transferred to a 50 mL reaction vessel lined with para-polyphenol. The mixture was reacted at 180 °C for 11 h and then cooled overnight in an oven. The resulting liquid was neutralized to pH 7 with 0.5 mol / L hydrochloric acid solution and then transferred to a dialysis bag (MWCO = 3500 Da) for dialysis purification for 72 h. The product obtained in the dialysis bag was fluorine-doped carbon quantum dots (F-CDs) and stored in a refrigerator at 4 °C protected from light.

[0056] Comparative Example 1 The difference between this comparative example and Example 1 is that 0.8900 g of citric acid monohydrate and 0.2400 g of urea were ultrasonically dissolved in 20.0 mL of ultrapure water to finally prepare carbon quantum dots (CDs).

[0057] Comparative Example 2 The difference between this comparative example and Example 1 is that the reaction was carried out at 180°C for 10 hours in the reactor.

[0058] Comparative Example 3 The difference between this comparative example and Example 1 is that the reaction was carried out at 180°C for 12 hours in the reactor.

[0059] Test Example 1: Synthesis and Characterization of Fluorine-Doped Carbon Quantum Dots Figure 1 TEM images and particle size distribution maps of CDs and F-CDs are shown. Figure 1 As shown, both CDs and F-CDs are quasi-spherical particles of similar size, with excellent dispersibility and no obvious aggregation. Figure 1 It can be seen that the average particle size of CDs is 1.71 nm, and the average particle size of F-CDs is 1.58 nm.

[0060] Figure 2 and Figure 3 The images show TEM images of the fluorine-doped carbon quantum dots synthesized in Comparative Examples 2 and 3, respectively. Figure 2 and Figure 3 It can be seen that when the reaction time is short, nanoparticles cannot be formed, which affects the formation of the structure; when the reaction time is long, the reaction is excessive, and the synthesized fluorine-doped carbon quantum dots agglomerate with an average particle size >25nm. The particles are too large to be applied to the subsequent cotton salt stress experiment.

[0061] Figure 4 The images show the UV (black line), excitation (blue line), and emission (red line) spectra of CDs and F-CDs, as well as the emission spectra of FCQDs at different excitation wavelengths. Figure 4As shown in a), CDs have an absorption peak in the ultraviolet region, with a characteristic absorption peak at 336 nm, mainly attributed to the n→π* transition of their surface states. The optimal excitation wavelength for CDs is 345 nm, and the optimal emission wavelength is 419 nm. Figure 4 The illustration in (a) shows that the aqueous solution of CDs is transparent and colorless under visible light, and exhibits bright blue fluorescence under ultraviolet light. Figure 4 As shown in b), F-CDs exhibit a strong absorption peak in the ultraviolet region, with a characteristic absorption peak at 331 nm, primarily attributed to the π→π* orbital transition of C=C. Furthermore, the optimal excitation wavelength for F-CDs is 337 nm, and the optimal emission wavelength is 440 nm. Figure 4 The illustration in b) shows that the aqueous solution of F-CDs appears pale yellow under visible light and exhibits bright blue fluorescence under ultraviolet light. The emission wavelength of carbon quantum dots typically changes with the excitation wavelength, such as... Figure 4 As shown in c), the maximum emission wavelength of F-CDs varies under different excitation wavelengths, indicating that F-CDs are wavelength-dependent.

[0062] Depend on Figure 5 It can be seen that the chemical structure of the carbon quantum dots can be obtained by FT-IR analysis of F-CDs. Figure 5 It can be known that 3400 cm -1 and 3188 cm -1 For the tensile vibrations of OH and NH, 2976 cm -1 This can be considered as a tensile vibration of CH, 1560 cm -1 For C=C conjugate tensile vibration, 1395 cm -1 Tensile vibrations attributed to CN, and 1190 cm -1 Originating from the tensile vibration of the CF bond, 991 cm -1 Stretching vibration originating from CO, 771 cm -1 and 602 cm -1 The planar bending vibrations from CH, as revealed by infrared analysis, indicate the presence of CF bonds in the carbon dot, suggesting successful doping with fluorine atoms. Furthermore, the presence of OH, NH, and other groups significantly enhances the hydrophilicity of the FCDs.

[0063] XPS analysis was used to analyze the chemical elements, chemical bonds, and bond energies of F-CDs. F-CDs mainly contain three elements: C, N, O, and F. Figure 5As shown in the figure, the four absorption peaks are C1s, N1s, O1s, and F1s, with bond energies of 284.53 eV, 399.81 eV, 531.59 eV, and 689.73 eV, respectively. The contents of these four elements are 56.1%, 84.1%, 34.7%, and 0.79%, respectively.

[0064] Figure 6 High-resolution XPS spectra of C1s, N1s, O1s, and F1s in F-CDs. (Source: [Insert source here]) Figure 6 It can be seen that peak separation processing is performed on the XPS spectrum. Figure 6 Figure a) shows the C1s peak profile, which can be divided into 7 peaks. The most obvious peak is the CC peak, which is about 284.8 eV, while the CF peak can be seen at 290.5 eV. The C=O, OC=O, C=C, NC=O, and CO peaks are detected at 287.0 eV, 288.5 eV, 284.4 eV, 288.1 eV, and 286.3 eV, respectively. Figure 6 b) in the figure is the N1s peak profile, which contains C=N, fluorinated pyrrole N and CNC peaks, located at 398.2 eV, 399.5 eV and 400.7 eV, respectively. Figure 6 c) in the figure is the O1s peak profile, which contains CO, C=O, and C-OH / COC peaks, which can be detected at 532.0 eV, 531.1 eV, and 533 eV, respectively. Figure 6 In diagram d), the peak profile of F1s is shown, containing fluoride and CF peaks, which appear at 689.7 eV and 693.9 eV. These results are consistent with the FT-IR results, indicating that F-CDs contain oxygen-containing and nitrogen-containing groups, have good water solubility, and also contain F bonds, indicating that F was successfully doped.

[0065] Test Example 2: Screening for the optimal concentration of fluorine-doped carbon quantum dots to improve the salt tolerance of cotton. F-CDs prepared in Example 1 at concentrations of 0 (control), 25, 50, 100, and 200 mg / L were used to treat cotton seedlings with fully expanded true leaves. The seedlings were then subjected to salt stress for 5 days with a 200 mmol / L NaCl solution, and the cotton phenotype was observed. Specifically, when two true leaves had emerged, F-CDs were applied to the true leaves of the cotton seedlings. The control group was treated with pure water. After 3 hours of dark treatment, the true leaves were placed in Hoagland's nutrient solution, and 200 mmol / L NaCl was added to simulate salt stress. The seedlings were then cultured under light, and the growth of the cotton seedlings was observed after 5 days.

[0066] Figure 7Top-view images showing the phenotypic characteristics of cotton plants treated with different concentrations of F-CDs and the control group after 5 days of salt stress, along with the fresh and dry weights of the cotton. Through concentration screening, it was determined that cotton seedlings treated with 100 mg / L F-CDs exhibited the strongest salt tolerance. Figure 7 As shown, cotton seedlings treated with 100 mg / L F-CDs had more vibrant green and fuller leaves, while the leaves of cotton seedlings in other concentration groups were almost withered. It can also be seen that the cotton plants in the 100 mg / L group were larger. Subsequently, the fresh weight and dry weight of cotton seedlings in each concentration group were measured, as shown below. Figure 7 As shown, only the 100 mg / L group had significantly higher fresh weight and dry weight than the control group, with fresh weight increasing by 40.7% and dry weight by 32.3%. Furthermore, from Figure 7 The fresh and dry weight data show that 100 mg / L F-CDs are significantly different from other concentrations of F-CDs and the control group. P <0.05.

[0067] Test Example 3: Comparison of the effects of two types of carbon quantum dots on improving the salt tolerance of cotton under salt stress Cotton seedlings with fully expanded true leaves were treated with CDs and F-CDs at a concentration of 0 (control) and 100 mg / L respectively. They were then subjected to salt stress with 200 mmol / L NaCl for 5 days. The specific operation was the same as in Test Example 2. The phenotype of the cotton was observed.

[0068] Figure 8 Top-view images of cotton plants after 5 days of salt stress, including the control group, CDs-treated plants, and F-CDs-treated plants, as well as the dry and fresh weights of the cotton plants in different groups. Figure 8 As shown in the top views of a) and b), the cotton seedlings in the F-CDs group have brighter, fuller green leaves, while the cotton seedlings in the CDs group have more withered and yellow leaves, and the cotton seedlings in the control group have almost withered leaves. Furthermore, it can be seen that the cotton plants in the F-CDs group are more intact, while the cotton plants in the CDs group not only have slightly withered true leaves, but also nearly withered cotyledons. Further, from... Figure 8 The cotton plant dry and fresh weight data in (c) and (d) also show that, compared with the CDs group, the F-CDs group had significantly increased fresh and dry weight of cotton seedlings, with fresh weight increasing by 40.1% and dry weight increasing by 17.8%. The figure also shows a significant difference between the F-CDs group and the CDs group. P <0.05.

[0069] Test Example 4: Effects of two types of carbon quantum dots on reactive oxygen species content in cotton leaves under salt stress For specific experimental procedures related to salt stress, please refer to Test Example 3.

[0070] like Figure 9As shown, compared with the control group and the CDs group, the F-CDs group significantly reduced the H2O2 content in cotton leaves, by 94.3% and 91.9%, respectively. The O2·- content in the F-CDs group was significantly lower than that in the control group and the CDs group by 47.6% and 33.2%, respectively. Figure 9 It can be seen that, compared with the control group and the CDs group, the reactive oxygen species content in the cotton treated with F-CDs group was significantly different. P <0.05. This indicates that cotton seedlings treated with F-CDs showed a significant reduction in ROS content under salt stress, thereby enhancing their resistance to salt stress.

[0071] Test Example 5: Effects of two types of carbon quantum dots on the activity of antioxidant enzymes in cotton leaves under salt stress For specific experimental procedures related to salt stress, please refer to Test Example 3.

[0072] Antioxidant enzymes mainly include SOD, POD, and CAT. When plants are subjected to salt stress, their internal defense mechanisms produce antioxidant enzymes to reduce the damage caused by salt stress.

[0073] By measuring the activities of SOD, POD, and CAT, such as Figure 10 As shown, compared to the control group, the CDs group showed no significant changes in SOD and POD, but a significant decrease in CAT. Conversely, compared to both the control and CDs groups, the F-CDs group showed a significant increase in SOD and CAT activities, demonstrating a statistically significant difference. P <0.05, representing increases of 9.0% and 31.6%, respectively. Although POD did not show a significant increase, F-CDs had no negative impact on POD activity.

[0074] The results showed that under salt stress, the antioxidant enzyme activity of cotton seedlings treated with F-CDs was enhanced, and the ROS scavenging capacity of cotton seedlings was increased, while the antioxidant enzyme activity of cotton seedlings treated with CDs remained unchanged or even decreased. This demonstrates that F-CDs have a greater ability than CDs to assist in regulating ROS balance in cotton.

[0075] Test Example 6: Effects of two types of carbon quantum dots on proline and malondialdehyde content in cotton leaves under salt stress The experimental procedure for salt stress is the same as in Test Example 3.

[0076] Proline (pro), as an osmotic regulator in cotton, can maintain intracellular turgor pressure, thereby reducing the effects of salt stress on the plant. Under normal stress conditions, the pro content in cotton is low, but under salt stress, the pro content increases significantly.

[0077] like Figure 11As shown, the Pro content in the control group was very high, while after F-CDs treatment, the Pro content in cotton leaves was significantly lower than that in the control group and the CDs group, showing a significant difference. P <0.05, representing reductions of 94.7% and 94.3%, respectively. This indicates that cotton leaves treated with F-CDs can significantly reduce Pro release under salt stress conditions, and F-CDs can protect cotton from damage caused by salt stress, while CDs of the same concentration cannot achieve the same effect.

[0078] Malondialdehyde (MDA) is a harmful substance with certain cytotoxic properties. It cross-links and polymerizes with biomolecules such as proteins and nucleic acids, causing changes in their structure or function. MDA is one of the products of cell membrane lipid peroxidation, and its content can reflect the degree of cell damage caused by oxidative stress in plants under stress.

[0079] like Figure 11 As shown, after 5 days of salt stress, the MDA content in the true leaves of cotton in the F-CDs treatment group was significantly lower than that in the control group and the CDs group, showing a statistically significant difference. P <0.05, a reduction of 73.0% and 46.3%. The magnitude of the reduction indicates that the F-CDs treatment group had a more significant impact on the MDA content of cotton true leaves than the CDs treatment group. Therefore, F-CDs better protected the integrity of cotton true leaf cell membranes than CDs, thereby improving the salt tolerance of cotton.

[0080] Test Example 7: Determination of the in vitro reactive oxygen species scavenging capacity of two types of carbon quantum dots under salt stress This study investigates the in vitro ROS scavenging capabilities of CDs and F-CDs, specifically the extent to which CDs and F-CDs directly react with ROS, to infer the reason why F-CDs enhance the salt tolerance of cotton. Table 1 shows the in vitro ROS scavenging efficiency of CDs and F-CDs.

[0081] Table 1

[0082] As shown in Table 1, both CDs and F-CDs exhibited certain in vitro scavenging capabilities for H2O2 (CDs: 16.61%; F-CDs: 20.25%), O2·- (CDs: 22.83%; F-CDs: 30.85%), and ·OH (CDs: 1.51%; F-CDs: 7.31%). Among these, compared to CDs, F-CDs showed a significantly higher in vitro scavenging efficiency for O2·- (1.35 times) and a more significant increase in the in vitro scavenging efficiency for ·OH (4.84 times), demonstrating statistically significant differences. P<0.05. The in vitro scavenging efficiency of H2O2 showed no significant change. This indicates that, compared to CDs, F-CDs can react directly with ROS in plants more effectively, thereby achieving ROS scavenging.

[0083] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. The application of fluorine-doped carbon quantum dots in improving the salt stress response of cotton, characterized in that, The average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

2. The application according to claim 1, characterized in that, The average particle size of the fluorine-doped carbon quantum dots is 1-5 nm.

3. The application according to claim 1, characterized in that, The preparation method of the fluorine-doped carbon quantum dots includes the following steps: mixing and dissolving citric acid, nitrogen source and fluoride salt, carrying out hydrothermal reaction at 170-190℃, dialysis purification, and obtaining the fluorine-doped carbon quantum dots.

4. The application according to claim 3, characterized in that, The fluoride salt is selected from one or more of sodium fluoride and ammonium fluoride.

5. The application according to claim 3, characterized in that, The hydrothermal reaction time is 10.5-11.5 hours.

6. The application according to claim 1, characterized in that, It enhances salt stress in cotton by scavenging reactive oxygen species.

7. The application according to claim 1, characterized in that, Cotton leaves were treated with a fluorine-doped carbon quantum dot solution with a concentration of 80-120 mg / L.

8. The application of fluorine-doped carbon quantum dots in improving the antioxidant properties of cotton, characterized in that, The average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

9. The application according to claim 8, characterized in that, Improving the antioxidant properties of cotton means scavenging at least one of hydrogen peroxide, hydroxyl radicals, and superoxide anion radicals.

10. The application of fluorine-doped carbon quantum dots in increasing the dry or fresh weight of cotton, characterized in that, The average particle size of the fluorine-doped carbon quantum dots is 0.5-10 nm.

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