Acid-regulated graphitized carbon dots as well as preparation method and salt and alkali resistance application thereof

Abstract

The invention discloses an acid-regulated graphitized carbon dot as well as a preparation method and salt and alkali resistance application thereof.The preparation method of the acid-regulated graphitized carbon dot comprises the following steps: S1, dissolving pyronin B in ethylene glycol to obtain a dissolved solution; s2, adding a hydrochloric acid solution into the dissolving solution to obtain a precursor reaction solution; s3, the precursor reaction liquid is subjected to a reaction through a one-pot solvothermal method, and a crude product is obtained; s4, carrying out suction filtration and dialysis on the crude product to obtain graphitized carbon dots; when the hydrochloric acid content in the precursor reaction liquid is different, graphitized carbon dots with different SOD enzyme activities can be obtained. According to the invention, hydrochloric acid is used as a regulation switch, and a series of carbon dots with different carbonyl contents, fluorescence colors and SOD-like activity are prepared by controlling the amount of added hydrochloric acid and influencing the carbonization degree of a carbon source and the formation of surface functional groups in a carbon dot synthesis process; and the method has the outstanding advantages of simplicity and convenience in operation, high repeatability, low cost and easiness in large-scale production.

Description

Technical Field

[0001] This invention relates to the technical field of carbon dot preparation, and more particularly to an acid-controlled graphitized carbon dot, its preparation method, and its salt and alkali resistant applications. Background Technology

[0002] Salt stress is one of the major abiotic stress factors that restrict crop growth, development and yield. Under salt stress conditions, plants accumulate excessive reactive oxygen species, such as superoxide anions and hydrogen peroxide, which lead to a series of oxidative damages such as cell membrane lipid peroxidation, enzyme inactivation and DNA damage, thereby inhibiting seed germination, hindering seedling growth and ultimately causing a significant reduction in crop yield.

[0003] Carbon dots, as a key carbon-based nanomaterial, have attracted sustained and widespread attention in the scientific research field since their discovery in 2004 due to their low cost, excellent biocompatibility, negligible ecotoxicity, tunable fluorescence properties, and outstanding photostability. In recent years, some studies have begun to focus on the application of carbon dots in agriculture, such as as nano-fertilizers or growth regulators. However, these applications are mostly focused on promoting growth or providing nutrients, and cannot solve the technical problem of salt stress in plants.

[0004] Meanwhile, existing technologies for controlling carbon dot performance often rely on replacing the precursor, doping with heteroatoms, or complex post-modification processes, which are cumbersome and make it difficult to achieve simultaneous and precise control of multiple parameters. Summary of the Invention

[0005] This invention aims to at least partially solve one of the problems in related technologies. Therefore, one objective of this invention is to provide an acid-controlled method for preparing graphitized carbon dots. This method utilizes hydrochloric acid as a "control switch," controlling the amount of hydrochloric acid added during carbon dot synthesis to influence the degree of carbonization of the carbon source and the formation of surface functional groups, thereby preparing a series of carbon dots with different carbonyl contents, fluorescence colors, and SOD-like activities. This method avoids complex processes and has significant advantages such as simple operation, high repeatability, low cost, and ease of scale-up production.

[0006] A method for preparing acid-controlled graphitized carbon dots, comprising: S1: Dissolve Pyronin B in ethylene glycol to obtain a solution; S2: Add hydrochloric acid solution to the solution to obtain the precursor reaction solution; S3: The precursor reaction solution is reacted by a one-pot solvothermal method to obtain the crude product; S4: The crude product is filtered and dialyzed to obtain graphitized carbon dots; when the hydrochloric acid content in the precursor reaction solution is different, graphitized carbon dots with different SOD enzyme activities can be obtained.

[0007] Furthermore, the temperature used in the one-pot solvothermal method is 180-220℃, and the reaction time of the one-pot solvothermal method is 8-12 hours.

[0008] Furthermore, the one-pot solvothermal process is carried out in a stainless steel autoclave with a polytetrafluoroethylene liner.

[0009] Furthermore, the concentration of the hydrochloric acid solution in step S2 is 4.0-6.0 mol / L.

[0010] Furthermore, the ratio of pyronin B to hydrochloric acid solution is 1 / 320 g·ml. -1 -1 / 480 g·ml -1 .

[0011] Further, the ratio of pyronin B to ethylene glycol in step S1 is 1 / 24 g·ml. -1 -1 / 120 g·ml -1 .

[0012] Furthermore, the filtration in step S4 uses a microporous membrane with a pore size of 0.22 μm; the dialysis uses a dialysis bag with a molecular weight cutoff of 1000 Da, with deionized water as the dialysis medium, and the dialysis time is 24-72 hours.

[0013] The second objective of this application is to provide an acid-controlled graphitized carbon dot, prepared using the method described above.

[0014] The third objective of this application is to provide an application of acid-regulated graphitized carbon dots in the field of salt and alkali resistance, as described above, an acid-regulated graphitized carbon dot used to prepare a plant stress resistance inducer, which is used to enhance the plant's resistance to salt stress.

[0015] Furthermore, the graphitized carbon dots can act as antioxidants to scavenge superoxide anion free radicals.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application utilizes hydrochloric acid as a "control switch" to control the amount of hydrochloric acid added during the carbon dot synthesis process, thereby affecting the degree of carbonization of the carbon source and the formation of surface functional groups, and preparing a series of carbon dots with different carbonyl contents, fluorescence colors and SOD-like activities. It avoids complex processes and has the outstanding advantages of simple operation, high repeatability, low cost and easy scale-up production.

[0017] This application utilizes acid-regulated graphitized carbon dots to improve the salt tolerance of crops. The graphitized carbon dots primarily function as exogenous, highly efficient nanoenzymes, directly scavenging superoxide anion radicals accumulated in plants under salt stress, thus mitigating oxidative damage at its source. The effect is directly and positively correlated with the SOD-like activity intensity of the carbon dots themselves. The stress-resistance effect of this application is predictable and significant: the more hydrochloric acid added during synthesis (the stronger the degree of carbonization, the higher the carbonyl content, and the stronger the SOD-like activity), the more significant the effect of alleviating plant salt stress and promoting growth. This predictability greatly enhances the reliability of the product's application. Furthermore, the graphitized carbon dots of this application are environmentally friendly and biosafe: the preparation process is green, the raw materials are non-toxic, and the carbon dots themselves have good biocompatibility. This not only opens up new agricultural application scenarios for carbon dot materials but also provides core technological support for the development of a new generation of nano-biological stress-resistance agents. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] In the attached image: Figure 1 To control the volume of acid, images of CDs of different colors under a UV lamp were prepared. Figure 2 Transmission electron microscopy (TEM) image of carbon dots; Figure 3 High-resolution transmission electron microscopy image of carbon dots; Figure 4 The fluorescence spectrum of the carbon dots; Figure 5 The C-spectrum of the XPS for carbon dots; Figure 6 The O spectrum of XPS for carbon dots; Figure 7 The infrared spectrum of carbon dots; Figure 8 The pyrogallol method for carbon dot-type SOD activity; Figure 9 The NBT method for carbon dot-based SOD activity; Figure 10 Images show the growth of maize, rice, and soybeans one week after treatment with CD1, CD4, and CD6 under NaCl stress; among them, Figure 10The first row is corn, the second row is rice, and the third row is soybeans; Figure 11 Images of maize after CD6 processing and growth in saline-alkali soil after one month and two months are shown. The first row shows a first-person view of maize growth after one month, the second row shows a second-person view of maize growth after one month, and the third row shows a first-person view of maize growth after two months. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the referred mechanism or element must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0022] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0023] In the following description, specific details such as particular system structures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, mechanisms, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0024] This application provides a method for preparing acid-controlled graphitized carbon dots, comprising: S1: Dissolve pyronin B in ethylene glycol to obtain a solution. The ratio of pyronin B to ethylene glycol is 1 / 24 g·ml. -1 -1 / 120 g·ml -1 .

[0025] S2: Add hydrochloric acid solution to the solution to obtain precursor reaction solution.

[0026] The concentration of the hydrochloric acid solution was 4.0-6.0 mol / L, and the ratio of pyronin B to hydrochloric acid solution was 1 / 320 g·ml. -1 -1 / 480 g·ml -1 .

[0027] S3: The precursor reaction solution is reacted by a one-pot solvothermal method to obtain the crude product.

[0028] This application describes a one-pot solvothermal process where the reaction is carried out in a stainless steel autoclave lined with polytetrafluoroethylene; the temperature used in the one-pot solvothermal process is 180-220°C, and the reaction time is 8-12 hours.

[0029] S4: The crude product is filtered and dialyzed to obtain graphitized carbon dots; when the hydrochloric acid content in the precursor reaction solution is different, graphitized carbon dots with different SOD enzyme activities can be obtained.

[0030] The filtration process uses a microporous membrane with a pore size of 0.22 μm; the dialysis process uses a dialysis bag with a molecular weight cutoff of 1000 Da, with deionized water as the dialysis medium, and the dialysis time is 24-72 hours.

[0031] This application utilizes a simple and controllable chemical method to directionally synthesize carbon dots with varying degrees of graphitization and different contents of surface carbonyl functional groups. Specifically, this invention creatively utilizes the amount of acid in the reaction system as a single core control variable, achieving "one adjustment for multiple controls." By simply adjusting the amount of acid added at the initial stage of the reaction, the degree of carbonization, carbonyl content, fluorescence color, and SOD-like activity of the carbon dots can be simultaneously and continuously controlled during a one-step synthesis process. This method avoids complex processes and has significant advantages such as ease of operation, high reproducibility, low cost, and ease of scale-up production.

[0032] Example 1 This application provides a method for preparing acid-controlled graphitized carbon dots, comprising: S1: Dissolve 0.025 g of Pyronin B in 10 ml of ethylene glycol to obtain a solution.

[0033] S2: Add 0, 600, 1200, 1600, 1800 and 3000 μL of hydrochloric acid solution to the solution in sequence to obtain the precursor reaction solution.

[0034] The concentration of the hydrochloric acid solution is 4.0-6.0 mol / L.

[0035] S3: The precursor reaction solution is reacted by a one-pot solvothermal method to obtain the crude product.

[0036] This application describes a one-pot solvothermal process where the reaction is carried out in a stainless steel autoclave lined with polytetrafluoroethylene; the temperature used in the one-pot solvothermal process is 180-220°C, and the reaction time is 8-12 hours.

[0037] S4: The crude product is subjected to vacuum filtration and dialysis. Specifically, the vacuum filtration uses a microporous membrane with a pore size of 0.22 μm; the dialysis uses a dialysis bag with a molecular weight cutoff of 1000 Da, with deionized water as the dialysis medium, and the dialysis time is 24-72 hours; six graphitized carbon dots are obtained, corresponding to CD1, CD2, CD3, CD4, CD5, and CD6; wherein, the hydrochloric acid volume corresponding to CD1 is 0 μL; the hydrochloric acid volume corresponding to CD2 is 600 μL; the hydrochloric acid volume corresponding to CD3 is 1200 μL; the hydrochloric acid volume corresponding to CD4 is 1600 μL; the hydrochloric acid volume corresponding to CD5 is 1800 μL; and the hydrochloric acid volume corresponding to CD6 is 3000 μL.

[0038] Figure 1 To prepare UV images of carbon dots of different colors by adjusting the volume of acid, we can see that as the volume of acid added increases, the carbon dots change from red to blue, achieving controllability of multicolor carbon dots. The hydrochloric acid volumes from left to right are: 0 μL, 100 μL, 200 μL, 300 μL, 400 μL, 500 μL, 600 μL, 700 μL, 800 μL, 900 μL, 1000 μL, 1200 μL, 1400 μL, 1600 μL, 1800 μL, 2000 μL, 2200 μL, 2400 μL, 2600 μL, 2800 μL, 3000 μL, 3200 μL, 3400 μL, 3600 μL, 3800 μL, and 4000 μL.

[0039] Figure 2 The image shows a transmission electron microscope (TEM) image of the carbon dots. The prepared carbon dots exhibit a uniformly dispersed spherical or quasi-spherical morphology, and the carbon dots gradually increase in size with increasing hydrochloric acid content.

[0040] Figure 3The attached figure shows a high-resolution TEM image of carbon dots, with the 0.21 nm lattice spacing corresponding to the (100) crystal plane of graphene. It can be seen that the degree of carbonization of carbon dots can be controlled by adjusting the amount of acid; the more hydrochloric acid added, the higher the degree of carbonization and the larger the carbon dot size.

[0041] Figure 4 The image shows the fluorescence emission pattern of carbon dots. The carbon dots exhibit dual emission characteristics, and the blue light peak gradually intensifies as the volume of acid added increases.

[0042] Figure 5 The image shows the XPS C-chromatogram of the carbon dots. The data indicates that as the amount of acid added increases, the carbon-carbon double bond content of the synthesized carbon dots increases, indicating that the degree of carbonization of the carbon dots gradually increases with the addition of hydrochloric acid.

[0043] Figure 6 The XPS O spectrum of the carbon dots shows that the carbonyl content of the synthesized carbon dots increases with the addition of more acid; among them, the carbonyl group plays an important role in exerting SOD-like activity.

[0044] Figure 7 The image shows the infrared spectrum of carbon dots. It can be seen that carbon dots with different acid contents all exhibit OH peak, NH peak, C=O peak, and CO peak. Furthermore, as the amount of acid added increases, the C=O peak gradually strengthens, indicating that the degree of carbonization of the carbon dots gradually increases.

[0045] Example 2 This embodiment is used to test the ability of CD1, CD4, and CD6 prepared in Example 1 to scavenge superoxide anion free radicals.

[0046] In this embodiment, the scavenging ability of CD1, CD4, and CD6 diluted 100 times for O2·− was tested by NBT reduction and pyrogallol oxidation methods.

[0047] like Figure 8 The method described above refers to the pyrogallol method for detecting the activity of carbon point-based SOD. The pyrogallol method revealed that the highest absorption peak at 319 nm was observed in the control group (without CDs). This 319 nm absorption peak corresponds to the intermediate product generated by the auto-oxidation of pyrogallol. The absorbance values ​​at 319 nm gradually decreased for pyrogallol+CD1, pyrogallol+CD4, and pyrogallol+CD6 in the experimental group, indicating that the O2·− generated by the auto-oxidation of pyrogallol was effectively removed by CDs, resulting in a reduction in the amount of colored intermediates.

[0048] like Figure 9The formazan generated by the oxidation of NBT showed significantly higher absorption at 560 nm than that of the experimental groups NBT+CD1, NBT+CD4, and NBT+CD6. Furthermore, the absorption values ​​of NBT+CD1, NBT+CD4, and NBT+CD6 at 560 nm gradually decreased, indicating that CD6 has higher SOD-like activity than CD1 and CD4 and can better remove O2·−.

[0049] Therefore, the above results indicate that CD1, CD4, and CD6 possess SOD-like activity, especially CD6, which exhibits excellent SOD-like activity. Figure 6 It is known that the increasing carbonyl content of CDs in this application gradually enhances their SOD-like activity, thereby allowing the SOD-like activity of carbon dots to be controlled by adjusting the amount of acid.

[0050] This application systematically correlates the degree of graphitization of carbon dots with their fluorescence color and SOD-like activity, establishing a clear "structure-activity" relationship. Specifically, this application is the first to systematically reveal and empirically demonstrate a clear and quantifiable positive correlation: "hydrochloric acid volume synthesis conditions → high surface carbonyl (C=O) content → strong SOD-like enzyme activity." This is not only an important scientific discovery, but also provides universal design principles and theoretical models for the rational design of carbon-based nanozymes with specific biocatalytic functions in the future, realizing a leap from "experience-based trial and error" to "directed design."

[0051] Therefore, the acid-controlled graphitized carbon dots prepared in this application can be used to prepare antioxidants for scavenging superoxide anion free radicals.

[0052] Example 3 This embodiment is used to test the effects of CD1, CD4, and CD6 prepared in Example 1 on plant salt tolerance, including: Seed disinfection treatment: Corn, soybean, and rice seeds were disinfected with 5% H2O2 for 30 min, and then washed 4-5 times with deionized water. Subsequently, the corn, soybean, and rice seeds were placed on absorbent paper and air-dried at room temperature.

[0053] Seed initiation: Select uniformly sized corn, soybean, and rice seeds and place them in centrifuge tubes at a seed mass (g) to solution volume (mL) ratio of 1:4. Shake at 100 rpm for 12 hours in the dark at 25°C. After 12 hours, remove the seeds, wash them three times with deionized water, and then air dry them at room temperature.

[0054] Salt stress was simulated using a 200 mM NaCl solution. Induced maize seeds were divided into five treatment groups: control (H2O), salt stress (NaCl), and salt stress + CDs (NaCl + CD1, NaCl + CD4, NaCl + CD6). Two germination papers were placed in 10 cm × 10 cm × 2 cm germination boxes. The control group received 10 mL of ultrapure water, while the salt stress treatments received 10 mL of 200 mM NaCl solution. Dried maize seeds were sown into the germination boxes, 10 seeds per box, with three replicates. The germination boxes were then transferred to an incubator and cultured at 25 ℃ for 7 days. Germination was considered complete when the radicle was of equal length to the seed. This was used to test the mitigating effects of CD1, CD4, and CD6 on maize seed growth under salt stress. The test results are as follows: Figure 10 As shown in the first row, Figure 10 In the diagram, CK refers to the control group, NaCl refers to the salt stress treatment group with 10 mL of 200 mM NaCl solution, CD1 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD1, CD4 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD4, and CD6 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD6. It can be seen that the growth of maize seeds in experimental groups CD1, CD4, and CD6 was significantly better than that in the salt stress treatment group.

[0055] Salt stress was simulated in soil containing 200 mM NaCl solution. Soybean seeds were placed in the soil and divided into five treatment groups: control (H2O), salt stress (NaCl), and salt stress + CDs (NaCl + CD1, NaCl + CD4, NaCl + CD6). All seeds were grown in a plant culture chamber for 30 days. Each group contained 6 plants, with three replicates. The effects of CD1, CD4, and CD6 on alleviating salt stress in soybean seeds were tested. The test results are as follows: Figure 10 As shown in the third row, among which, Figure 10In the diagram, CK refers to the control group, NaCl refers to the salt stress treatment group with 10 mL of 200 mM NaCl solution, CD1 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD1, CD4 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD4, and CD6 refers to the experimental group with a mixture of 10 mL of 200 mM NaCl and a 10-fold dilution of CD6. It can be seen that the growth of soybean seeds in experimental groups CD1, CD4, and CD6 was significantly better than that in the salt stress treatment group.

[0056] The effects of CDs on rice seedlings under salt stress were observed using hydroponics. First, plump, brightly colored rice seeds of uniform size with no surface defects such as deformation or cracks were selected and placed in seedling trays, covered with aluminum foil. The seedling trays were then transferred to a 25℃ incubator for germination in the dark for 7 days. Rice seedlings that had reached the two-leaf stage were then transferred to ultrapure water of the same concentration, 200 mM NaCl solution, 200 mM NaCl solution containing CD1 diluted 10 times, 200 mM NaCl solution containing CD4 diluted 10 times, and 200 mM NaCl solution containing CD6 diluted 10 times, respectively, and cultured for 3 days before the indices were measured. The test results are as follows: Figure 10 As shown in the second row, where, Figure 10 In the diagram, CK refers to the control group, NaCl refers to the salt stress treatment group with 200 mM NaCl solution, CD1 refers to the experimental group corresponding to the addition of 200 mM NaCl solution diluted 10 times, CD4 refers to the experimental group corresponding to the addition of 200 mM NaCl solution diluted 10 times, and CD6 refers to the experimental group corresponding to the addition of 200 mM NaCl solution diluted 10 times. It can be seen that the growth of rice seedlings in experimental groups CD1, CD4, and CD6 is significantly better than that in the salt stress treatment group.

[0057] To further verify the application of graphitized carbon dots in the field of plant salt and alkali resistance, this embodiment uses pure water, CD6 solution diluted 1500 times, CD6 solution diluted 3000 times, and CD6 solution diluted 6000 times to soak corn seeds for 12 hours, and then dries the corn seeds and plants them in saline-alkali land.

[0058] like Figure 11 As shown, Figure 11The first and second rows show diagrams of corn planted in saline-alkali land one month after planting, and the third row shows diagrams of corn planted in saline-alkali land two months after planting. Group CK refers to corn seeds soaked in purified water, Group C1 refers to corn seeds soaked in CD6 diluted 1500 times, Group C2 refers to corn seeds soaked in CD6 diluted 3000 times, and Group C3 refers to corn seeds soaked in CD6 diluted 6000 times. It can be seen that corn treated with graphitized carbon dots exhibits better salt and alkali resistance.

[0059] Abiotic stresses in plants, such as salinization, typically lead to excessive accumulation of reactive oxygen species (ROS), disrupting their antioxidant systems and causing oxidative stress, resulting in DNA damage, lipid peroxidation, and mitochondrial degradation. The excessive ROS production caused by salinization exceeds the capacity of the crop's endogenous superoxide dismutase (SOD), necessitating exogenous nanozymes to restore redox homeostasis. The carbon dot mechanism in this application is directly linked to the carbonyl (C=O) functional groups enriched on its surface and their strong SOD-like activity: the material, through its specific surface chemical structure, mimics the function of the active site of the natural SOD enzyme. Under salinity stress, this material can actively and continuously catalyze the decomposition of excess superoxide anion radicals (O2·−) generated within crop cells, directly and effectively reducing ROS concentration. This process clearly alleviates oxidative damage caused by ROS overload, thereby helping crops maintain cellular homeostasis and exhibiting significant stress resistance. This study revealed the complete chain of action of the material, from its structural characteristics (high carbonyl content) to its enzymatic function (SOD-like activity), physiological effects (ROS scavenging), and final phenotype (salt damage mitigation).

[0060] This application provides a nanomaterial with significant effects, a clear mechanism, and environmental friendliness for effectively alleviating salt stress damage in plants. Unlike many agricultural nanomaterials that only report phenotypic improvements with unclear mechanisms, this invention has a clear mechanism and predictable effects at the application level. The mechanism of action is direct and clear: the carbon dots mainly act as exogenous, highly efficient nanoenzymes, directly scavenging superoxide anion free radicals accumulated in plants under salt stress, reducing oxidative damage at its source. The effect is directly and positively correlated with the SOD-like activity intensity of the carbon dots themselves. The stress resistance effect of this application is predictable and significant: the more hydrochloric acid added during synthesis (the stronger the degree of carbonization, the higher the carbonyl content, and the stronger the SOD-like activity), the more significant the effect of alleviating plant salt stress and promoting growth. This predictability of effect greatly improves the reliability of the product's application. The graphitized carbon dots of this application are environmentally friendly and biosafe: the preparation process is green, the raw materials are non-toxic, and the carbon dots themselves have good biocompatibility, laying the foundation for their safe application in agricultural production.

[0061] Therefore, the acid-regulated graphitized carbon dots prepared in this application can be used to prepare plant stress resistance inducers, which are used to enhance the plant's resistance to salt stress.

[0062] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for preparing acid-controlled graphitized carbon dots, characterized in that, include: S1: Dissolve Pyronin B in ethylene glycol to obtain a solution; S2: Add hydrochloric acid solution to the solution to obtain the precursor reaction solution; S3: The precursor reaction solution is reacted by a one-pot solvothermal method to obtain the crude product; S4: The crude product is filtered and dialyzed to obtain graphitized carbon dots; when the hydrochloric acid content in the precursor reaction solution is different, graphitized carbon dots with different SOD enzyme activities can be obtained.

2. The method for preparing acid-controlled graphitized carbon dots according to claim 1, characterized in that, The temperature used in the one-pot solvothermal method is 180-220℃, and the reaction time is 8-12 hours.

3. The method for preparing acid-controlled graphitized carbon dots according to claim 1, characterized in that, The one-pot solvothermal method is carried out in a stainless steel autoclave lined with polytetrafluoroethylene.

4. The method for preparing acid-controlled graphitized carbon dots according to claim 1, characterized in that, In step S2, the concentration of the hydrochloric acid solution is 4.0-6.0 mol / L.

5. The method for preparing acid-controlled graphitized carbon dots according to claim 4, characterized in that, The ratio of pyronin B to hydrochloric acid solution was 1 / 320 g·ml. -1 -1 / 480 g·ml -1 .

6. The method for preparing acid-controlled graphitized carbon dots according to claim 1, characterized in that, The ratio of pyronin B to ethylene glycol in step S1 is 1 / 24 g·ml -1 -1 / 120 g·ml -1 .

7. The method for preparing acid-controlled graphitized carbon dots according to claim 1, characterized in that, In step S4, the filtration is performed using a microporous membrane with a pore size of 0.22 μm; the dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000 Da, with deionized water as the dialysis medium, and the dialysis time is 24-72 hours.

8. An acid-regulated graphitized carbon dot, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of acid-regulated graphitized carbon dots in the field of salt and alkali resistance, characterized in that, The acid-regulated graphitized carbon dots of claim 8 are used to prepare plant stress resistance inducers, which are used to enhance the plant's resistance to salt stress.

10. The application of acid-controlled graphitized carbon dots according to claim 9 in the field of salt and alkali resistance, characterized in that, The graphitized carbon dots can act as antioxidants to scavenge superoxide anion free radicals.

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