Blue light-emitting water-soluble carbon quantum dots, a preparation method thereof and application thereof in drought resistance, yield increase and quality improvement of sweet potatoes

Abstract

The application discloses blue light emitting water-soluble carbon quantum dots and a preparation method and application thereof in drought resistance, yield increase and quality improvement of sweet potatoes, and relates to the technical field of carbon quantum dots, in particular to a preparation method of the blue light emitting water-soluble carbon quantum dots. The preparation method comprises the following steps: adding spermidine into deionized water, adding trisodium citrate after the spermidine is dissolved, stirring to completely dissolve, placing in a high-pressure reaction kettle to perform hydrothermal reaction, cooling after the reaction is completed, filtering, dialysis, and obtaining a water-soluble blue light carbon dot solution after impurities are removed. The carbon dots are prepared through a one-step hydrothermal method, the process is simple, easy to operate, low in cost and pollution-free, and is suitable for industrial production. The prepared water-soluble blue light carbon dots are small in size, have good monodispersity and water solubility, can improve the net photosynthetic rate of sweet potato leaves under PEG simulated drought stress conditions, reduce oxidation damage caused by drought stress, thereby enhancing the drought resistance of the sweet potatoes, and can increase the yield and quality of the sweet potatoes in field production, and are suitable for being widely popularized in yield and quality improvement of field crops under drought stress.

Description

Technical Field

[0001] This invention belongs to the field of nanotechnology in agriculture, specifically relating to a blue light-emitting water-soluble carbon quantum dot, its preparation method, and its application in drought resistance, yield increase, and quality improvement of sweet potatoes. Background Technology

[0002] Plants convert light energy into chemical energy through photosynthesis, a core pathway for the synthesis of organic matter within plants, providing the energy and carbon skeleton for plant growth, development, yield, and quality. In recent years, light-emitting diode (LED) supplemental lighting technology has been widely applied in facility agriculture, plant factories, and tissue culture, significantly improving crop photosynthetic efficiency and quality. However, LED supplemental lighting technology still faces challenges such as high cost, complex technology adaptability, and potential ecological risks, hindering its large-scale application in field crops like sweet potatoes, corn, and rice. Therefore, there is an urgent need to develop novel technologies capable of targeted regulation of light signals to bridge advanced materials science with practical agricultural production, lower application barriers, and construct optimized light environment solutions that combine stress resistance and yield enhancement, thereby improving the economic and ecological benefits of facility agriculture.

[0003] Drought stress is one of the main environmental factors limiting the sustainable development of the sweet potato industry. With the intensification of global climate anomalies and changes in ecological balance, frequent droughts severely restrict the yield and quality of sweet potatoes. Therefore, developing new technologies that can improve the drought resistance of sweet potatoes and synergistically optimize yield and quality is of great practical significance for promoting the establishment of an efficient drought-resistant cultivation technology system and the breeding of drought-resistant varieties.

[0004] Carbon dots (CDs), as a novel nanomaterial, are easily absorbed and utilized by plants due to their small particle size (1-10 nm), abundant surface functional groups, high biocompatibility, and low toxicity, showing significant potential in promoting plant growth and enhancing stress resistance. Carbon dots possess unique photoluminescent properties, making them a high-quality light supplement material to replace traditional LED light sources. Existing research has shown that using magnesium-nitrogen co-doped carbon dots, their blue light emission properties can significantly improve the photosynthetic activity of rice chloroplasts and the overall growth and development level after spraying. Furthermore, antioxidant blue light-emitting carbon dots synthesized from citric acid and ascorbic acid can effectively scavenge reactive oxygen species generated under stress, significantly improving the drought resistance of peas.

[0005] In conclusion, developing a water-soluble carbon quantum dot with stable blue light emission properties and applying it to sweet potato production to enhance the drought resistance of sweet potatoes while promoting yield and quality improvement is of great value and promising application for enriching the nano-agricultural technology system and achieving crop quality improvement and efficiency enhancement under adverse conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a blue light emitting water-soluble carbon quantum dot, its preparation method, and its application in drought resistance, yield increase, and quality improvement of sweet potatoes, so as to solve the problems of hindered growth and development, reduced yield, and reduced quality of sweet potatoes under drought stress, and achieve synergistic improvement in drought resistance, yield increase, and quality improvement.

[0007] To achieve the above-mentioned objective, this invention provides a method for preparing water-soluble carbon dots that emit blue light, comprising the following steps: adding spermidine to deionized water, adding trisodium citrate after dissolution, stirring to completely dissolve, placing in a high-pressure reactor for hydrothermal reaction, cooling after the reaction is completed, filtering, dialysis, removing impurities to obtain a water-soluble blue carbon dot solution.

[0008] Preferably, the hydrothermal reaction conditions are: a reaction temperature of 200°C and a reaction time of 8 h.

[0009] Preferably, the concentration of the spermidine solution is 0.01 mol / L.

[0010] Preferably, the concentration of the trisodium citrate dissolved in the spermidine solution is 0.068 mol / L.

[0011] Preferably, the filtration uses a 0.22 μm aqueous microporous membrane; the dialysis uses a dialysis bag with a molecular weight cutoff of 500 Da, and the dialysis time is 6 h.

[0012] To achieve the above-mentioned objective, the present invention also provides a water-soluble carbon dot that emits blue light, wherein the water-soluble carbon dot that emits blue light is prepared by the above-described preparation method.

[0013] To achieve the above-mentioned objectives, this invention also provides the application of the above-mentioned blue light-emitting water-soluble carbon dots in the drought resistance, yield increase and quality improvement of sweet potatoes.

[0014] Furthermore, the specific process is as follows: water-soluble blue light carbon dots are prepared into an aqueous solution and applied to sweet potato plants by foliar spraying.

[0015] Preferably, the concentration of the water-soluble blue light carbon dot aqueous solution is 0.45 mg / mL.

[0016] Furthermore, the application includes at least one of the following effects: (1) Increase the net photosynthetic rate and chlorophyll content of sweet potato leaves under drought stress; (2) Reduce the malondialdehyde content, superoxide anion generation rate and hydrogen peroxide content in sweet potato leaves under drought stress; (3) Increase the number of tubers per plant and the weight of tubers per plant under drought stress; (4) Increase the soluble sugar and starch content in sweet potato tubers under drought stress.

[0017] Compared with the prior art, the present invention has the following advantages: This invention prepares carbon dots using a one-step hydrothermal method with distilled water as the solvent. The process is simple, easy to operate, low in cost, and the reaction is completed within 12 hours without pollution, making it suitable for industrial production. The water-soluble blue-light carbon dots prepared by this invention have small particle size (average 2.21 nm), good monodispersity, high water solubility, and good biocompatibility (high survival rate in HeLa cells and low toxicity). They can emit stable blue light under 365 nm ultraviolet excitation. Under PEG-simulated drought conditions, foliar spraying of the carbon dots of this invention can significantly increase the net photosynthetic rate and chlorophyll content of sweet potato leaves, reduce malondialdehyde content, superoxide anion generation rate, and hydrogen peroxide content, alleviate oxidative damage, relieve leaf wilting, and enhance the drought tolerance of plants. Under normal irrigation and soil drought stress conditions, spraying of the carbon dots of this invention can significantly increase the number and weight of tubers per plant in Xushu 32 and Yanshu 25, and promote the accumulation of soluble sugars and starch in the tubers, thereby increasing the yield and improving the quality of sweet potatoes under drought stress. This invention provides a new approach for the application of nanomaterials in sweet potato production in arid and semi-arid regions, and is suitable for widespread application in enhancing the yield and quality of field crops under drought stress. Attached Figure Description

[0018] Figure 1 Photographs of water-soluble blue carbon dots under ultraviolet light irradiation (A), photoluminescence spectra under excitation at 360-420 nm (B), and a statistical diagram of the relative survival rate of HeLa cell lines under different concentrations of blue carbon dots (C). Figure 2 Transmission electron microscopy (TEM) image (A) and particle size distribution map (B) of water-soluble blue carbon dots; Figure 3 A schematic diagram illustrating the effect of blue light carbon dots on the phenotype of sweet potato seedlings under drought stress. Figure 4 A schematic diagram showing the effects of blue light carbon dots on the net photosynthetic rate (A) and total chlorophyll content (B) of sweet potato leaves under drought stress; Figure 5 The effects of blue light carbon dots on oxidative damage in sweet potato leaves under drought stress; (A) malondialdehyde content; (B) superoxide anion generation rate; (C) hydrogen peroxide content; Figure 6 This is a schematic diagram illustrating the effect of blue light carbon dots on the phenotype of sweet potato tubers under soil drought stress. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] Example A method for preparing water-soluble carbon dots that emit blue light includes the following steps: Weigh 0.2905 g of spermidine into 200 mL of deionized water. After dissolving, measure 70 mL of the solution and add 1.2352 g of trisodium citrate. Stir until completely dissolved and place in a high-pressure reactor. Heat at 200°C for 8 hours. After cooling, filter using an aqueous microporous membrane (0.22 μm) and a dialysis bag (500 Da) for 6 hours to remove impurities and obtain a water-soluble blue carbon dot solution. Store in a refrigerator at 4°C.

[0021] The water-soluble blue light carbon dots prepared in this embodiment were characterized as follows: Under 365 nm UV excitation, the carbon dot solution emitted a bright blue fluorescence. Figure 1 A). Fluorescence spectroscopy analysis showed that the carbon dots exhibited excitation-dependent fluorescence emission characteristics, with a strong fluorescence peak observed at an excitation wavelength of 380 nm and an emission peak at 455 nm. Figure 1 B). Cytotoxicity assays showed that HeLa cells treated with different concentrations of blue light carbon dots maintained a high relative cell viability, indicating that the carbon dots possess good biocompatibility and low toxicity. Figure 1 C).

[0022] Transmission electron microscopy (TEM) observations showed that the carbon dots were uniformly spherical and exhibited good monodispersity. Figure 2 A). High-resolution TEM images show that the lattice spacing of the carbon dots is 0.21 nm. Statistical analysis of the particle size distribution indicates that the average particle size of the carbon dots is 2.21 nm. Figure 2 B).

[0023] Application Example 1: Effects of water-soluble blue carbon dots on sweet potato seedling growth under PEG-simulated drought stress The water-soluble blue carbon dots prepared in the above embodiments were applied to sweet potatoes. Taking PEG-simulated drought stress as an example, their effect on the growth of sweet potato seedlings was investigated. The specific application process is as follows: The drought-sensitive sweet potato variety "Xushu 32" was selected as the experimental material. Seedlings of uniform growth, reaching the five-leaf stage, were chosen. The vines were pruned to a length of 20 cm below the stem tip, retaining five fully expanded leaves. These seedlings were cultured in hydroponic boxes containing 1 / 4 of a modified Hoagland nutrient solution, with 24 seedlings per box and continuous aeration for 24 hours. Treatment began when the root system reached approximately 6 cm in length. Polyethylene glycol 6000 (PEG-6000) was used to simulate drought stress. The treatment group received foliar spraying with 0.45 mg / mL blue light carbon point solution every other day for a total of three pretreatments; the control group received an equal volume of deionized water as foliar spray. Spraying was defined as ensuring all leaves, both upper and lower surfaces, were moistened, with the solution covering the leaves without dripping. After pretreatment, PEG-6000 was added to the nutrient solution to final concentrations of 0% (control) and 10% (w / v, simulating drought) to establish a normal control and a drought treatment, respectively. Eight seedlings were used for each treatment. Net photosynthetic rate of leaves was measured after 5 days of drought treatment.

[0024] At the end of the drought treatment, between 09:00 and 10:00, take 2-3 leaves of uniform growth from the fourth leaf, quickly wash them with distilled water and dry the surface moisture, wrap them in aluminum foil and place them in liquid nitrogen, and store them in an ultra-low temperature (-80℃) freezer for chlorophyll and oxidative damage determination.

[0025] The effects of PEG simulation of drought stress on sweet potato phenotypes, such as Figure 3 As shown, under PEG-simulated drought stress, the leaves of sweet potatoes in the control group without carbon dots showed significant wilting, and plant growth was inhibited; while the wilting of leaves in the treatment group sprayed with blue light carbon dots was significantly reduced, and the plants showed better growth. This indicates that blue light carbon dots treatment can alleviate drought-induced leaf wilting and promote plant growth. Figure 4 As shown, under PEG drought stress, spraying with blue light carbon dots significantly increased the net photosynthetic rate of sweet potato leaves. Figure 4 A) and chlorophyll content ( Figure 4 B). The results show that the blue light carbon dots prepared in this invention can effectively improve the photosynthetic capacity of sweet potato plants and enhance their drought tolerance.

[0026] like Figure 5 As shown, PEG-simulated drought stress leads to increased accumulation of reactive oxygen species (ROS), which interfere with metabolic pathways through lipid peroxidation, causing severe damage to membrane systems and organelles. Compared with the drought control, blue light carbon dot treatment significantly reduced the content of malondialdehyde (MDA) in leaves. Figure 5 A) Superoxide anion generation rate ( Figure 5 B) and hydrogen peroxide content ( Figure 5 C). It can be seen that the blue light carbon dots prepared in this invention can enhance the drought resistance of sweet potatoes by reducing oxidative damage.

[0027] Application Example 2: Effects of water-soluble blue light carbon dots on sweet potato yield and quality under drought stress in field soil Two varieties, “Xushu 32” and “Yanshu 25”, were selected for field trials. The experimental plots were arranged using a randomized block design, with two replicates for each treatment. Approximately 25 sweet potato seedlings were planted in each treatment plot, with a row spacing of approximately 100 cm and a plant spacing of 25 cm. Two levels of soil moisture treatment were set: (1) Normal irrigation: Normal irrigation throughout the entire growth period, maintaining a relative soil moisture content of (75+5)%; (2) Drought treatment: Normal irrigation for two weeks after the seedlings recovered 15 days after transplanting, followed by drought simulation with the moisture content controlled at (45+5)% for 15 days, after which normal irrigation was resumed.

[0028] After the drought treatment began, the treatment group was foliar sprayed with 0.45 mg / mL Blue Light Carbon Point once a week for a total of 7 times. The control group was treated with foliar spraying of the same amount of deionized water. The entire growth period was 145 days. After the growth period, the tuber biomass was weighed and the soluble sugar and starch content of the tubers was determined. The results are shown in Table 1 below: Table 1. Results of four sets of measurements for Xushu 32 and Yanshu 25 respectively. Depend on Figure 6 As shown in Table 1, under normal irrigation and soil drought stress conditions, spraying with blue light carbon dots significantly increased the number and weight of tubers per plant in Xushu 32 and Yanshu 25, and promoted the accumulation of soluble sugars and starches (Table 1). This demonstrates that the blue light carbon dots prepared in this invention can improve the yield and quality of sweet potatoes under drought stress.

Claims

1. A method for preparing water-soluble carbon dots that emit blue light, characterized in that, Includes the following steps: Spermine was added to deionized water and dissolved. Then, trisodium citrate was added and stirred until completely dissolved. The mixture was placed in a high-pressure reactor for hydrothermal reaction. After the reaction was completed, the mixture was cooled, filtered, and dialyzed to remove impurities and obtain a water-soluble blue carbon dot solution.

2. The method for preparing water-soluble carbon dots that emit blue light according to claim 1, characterized in that, The hydrothermal reaction conditions are: reaction temperature of 200°C and reaction time of 8 hours.

3. A method for preparing water-soluble carbon dots that emit blue light according to claim 1 or 2, characterized in that, The concentration of the spermidine solution is 0.01 mol / L.

4. A method for preparing water-soluble carbon dots that emit blue light according to claim 1 or 2, characterized in that, The concentration of trisodium citrate dissolved in spermidine solution is 0.068 mol / L.

5. A method for preparing water-soluble carbon dots that emit blue light according to claim 1 or 2, characterized in that, The filtration uses a 0.22 μm aqueous microporous membrane; the dialysis uses a dialysis bag with a molecular weight cutoff of 500 Da, and the dialysis time is 6 hours.

6. A water-soluble carbon dot that emits blue light, wherein the water-soluble carbon dot that emits blue light is prepared by the preparation method according to any one of claims 1-5.

7. The application of the blue light-emitting water-soluble carbon dots according to claim 6 in drought resistance, yield increase and quality improvement of sweet potatoes.

8. The application according to claim 7, characterized in that, The specific process is as follows: water-soluble blue light carbon dots are prepared into an aqueous solution and applied to sweet potato plants by foliar spraying.

9. The application according to claim 8, characterized in that, The concentration of the water-soluble blue carbon dot aqueous solution is 0.45 mg / mL.

10. The application according to claim 7, characterized in that, The application includes at least one of the following effects: (1) Increase the net photosynthetic rate and chlorophyll content of sweet potato leaves under drought stress; (2) Reduce the malondialdehyde content, superoxide anion generation rate and hydrogen peroxide content in sweet potato leaves under drought stress; (3) Increase the number of tubers per plant and the weight of tubers per plant under drought stress; (4) Increase the soluble sugar and starch content in sweet potato tubers under drought stress.

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