Preparation method and application of novel weed source carbon dots

Abstract

The invention discloses a preparation method and application of novel weed source carbon dots, and relates to the field of carbon nanomaterials and application. The dayflower carbon dots are prepared by adopting a one-step hydrothermal method, and the carbon dots can promote absorption of Fe elements in plants and chlorophyll synthesis of plant leaves and can improve the activity of protective enzymes in the plants, so that plant growth is promoted, and the oxidation resistance of the plants is improved; the dayflower carbon dots serve as a pesticide carrier, flonicamid is carried, a carbon dot-flonicamid nano dosage form (CDs-Flo) is constructed, it is found that the insecticidal effect of flonicamid can be effectively improved through the carbon dots, and excellent biological performance is embodied.

Description

Technical Field

[0001] The present invention relates to carbon nanomaterials and application fields, and in particular to a preparation method and application of novel weed-derived carbon dots. Background Art

[0002] Pesticides are an important material basis for ensuring food production safety. They are of great significance for controlling crop diseases, insect pests and weeds and ensuring a good grain harvest. However, due to the long-term and excessive use of pesticides, the negative impact on the environment and human body is becoming increasingly prominent. Therefore, the agricultural industry urgently needs to improve and enhance the current methods of pest control. In this context, some new green nanomaterials that play a positive role in agricultural production, such as carbon nanomaterials, have gradually become a hot topic of research. Only by taking green environmental protection as the theoretical basis and guiding principle and vigorously developing green agricultural technology can we better protect the ecological environment and maintain the sustainable development of agriculture while controlling pests.

[0003] Carbon dots are a type of spherical carbon nanomaterials with fluorescent properties and a particle size of less than 10nm. In 2004, a fluorescent carbon nano impurity was accidentally discovered during the separation and purification of single-walled carbon nanotubes, and carbon dots were synthesized for the first time. Since then, many fields have begun to study them, and it has gradually been found that carbon dots have good application prospects in many fields such as photocatalysis, light-emitting devices, biosensors, and medical treatment.

[0004] The sources of carbon dots are very wide, such as sugarcane, vinca roseus, wolfberry, sludge, green persimmon, silkworm pupae, etc. Various types of carbon sources provide rich raw materials for the preparation of carbon dots. Commelina is a harmful weed with strong adaptability and difficult to control. It is very common on roadsides, ridges and grasslands. At the same time, Commelina has a high carbon content and contains rich compounds such as flavonoids, alkaloids and phenolic acids. It is more suitable for the preparation of carbon dots. The transformation and rational use of Commelina can turn waste into treasure, and it can bring certain economic benefits while preventing and controlling weeds.

[0005] The carbon dots prepared using Commelina communis carbon source have the advantages of high luminescence efficiency, good biocompatibility, easy surface modification, stable optical properties, and simple and environmentally friendly preparation methods, providing more possibilities for the application of carbon dots in agricultural production and drug delivery. Summary of the invention

[0006] The purpose of the present invention is to provide a novel preparation method and application of weed-derived carbon dots, which provides more possibilities for the application of carbon dots in agricultural production and drug delivery.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing a novel weed-derived carbon dot, comprising at least the following steps:

[0008] S1: Pick fresh stems and leaves of Commelina communis, wash them with deionized water, and then put them into a juicer to crush and stir them to obtain plant homogenate;

[0009] S2: Weigh 0.1-3.5 g of plant homogenate, add 10 mL of deionized water, place in a 20 mL polytetrafluoroethylene reactor, and heat in an oven at 160°C-280°C for 6 h-14 h;

[0010] S3: After the carbon dot solution prepared in S2 is cooled to room temperature, it is centrifuged at 8000 r / min for 10 min, the supernatant is taken, and filtered with a 0.22 μm microporous membrane;

[0011] S4: Pour the carbon dot solution prepared in S3 into a three-necked flask, use a pipette to measure 0.1 mL of 20% PEI solution, add it dropwise into the three-necked flask, and stir in an 80°C oil bath to react for 4 h;

[0012] S5: freeze-dry the PEI-modified carbon dot solution to obtain carbon dot solid, and store it in a sealed container at 4°C.

[0013] Furthermore, when the amount of plant homogenate added in S2 is 2 g, the constant temperature heating reaction time is 11 h, and the reaction temperature is 240° C., the fluorescence intensity of the carbon dots reaches a maximum value, and this condition is determined to be the optimal preparation condition for the carbon dots.

[0014] A novel weed-derived carbon dot is used to promote plant growth. The novel weed-derived carbon dots obtained by a novel weed-derived carbon dot preparation method promote plant growth.

[0015] Furthermore, the method for demonstrating the plant promotion application comprises at least the following steps:

[0016] A: According to the preparation method of a novel weed-derived carbon dot according to claim 1, carbon dot solutions with concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 500 mg / L, 1000 mg / L and 2000 mg / L are prepared in sequence, and the carbon dot solutions are added to culture dishes containing pakchoi seeds, 15 mL is added to each dish, and deionized water without carbon dots is used as a blank control. On the 9th day, the growth indexes of pakchoi treated with carbon dot solutions of each concentration are measured;

[0017] B: Treat the seeds of Chinese cabbage with 500mg / L carbon dot solution, and observe the roots, stems and leaves of the cabbage under laser confocal microscopy. Under laser confocal microscopy, the fluorescence signals of carbon dots in the roots, stems and leaves of Chinese cabbage can be obtained, and the fluorescence signal of the roots of Chinese cabbage is the strongest, while the fluorescence signals in the stems and leaves are weaker, so as to study the absorption and transportation of carbon dots in plants;

[0018] C: The roots and leaves of the pakchoi treated with carbon dots were dried and ground into powder. The sample was accurately weighed into a 50 mL beaker, and 10 mL of mixed acid (HClO:HNO3=1:9) was added to digest at 300 °C. The digestion solution was then transferred to a 10 mL volumetric flask, fixed to volume with deionized water, and the Fe content in the pakchoi was determined by inductively coupled plasma mass spectrometry.

[0019] D: The chlorophyll content in the leaves of Chinese cabbage after the control group and carbon dots treatment was measured using a chlorophyll meter;

[0020] E: Accurately weigh 0.1g of pakchoi roots and leaves, treat with liquid nitrogen, add 0.9mL of extract, grind into homogenate on ice, centrifuge at 8000r / min, 4℃ for 10min in a low-temperature centrifuge, and take the supernatant; determine the SOD, POD and CAT enzyme activities in pakchoi according to the steps and methods in the kit instructions. The results showed that carbon dot treatment significantly increased the activities of three protective enzymes SOD, POD and CAT in pakchoi.

[0021] Furthermore, based on the blank control step A, the carbon dot solution has a certain promoting effect on the growth of Chinese cabbage, and at a concentration of 500 mg / L, the promoting effect on the growth of Chinese cabbage is most significant.

[0022] Furthermore, when the Fe content in the pakchoi was measured based on step C, the Fe content in the roots, stems and leaves of the pakchoi treated with 500 mg / L carbon dot solution increased to a certain extent, and the Fe content in the stems increased most significantly.

[0023] Furthermore, based on the chlorophyll content determination in step D, the chlorophyll content in the pakchoi slices treated with 500 mg / L carbon dot solution was significantly increased on the 5th and 10th days.

[0024] A novel weed-derived carbon dot is used as a carrier to improve the effective utilization rate of pesticides. The novel weed-derived carbon dots obtained by a novel weed-derived carbon dot preparation method are used as a carrier to improve the effective utilization rate of pesticides.

[0025] Furthermore, the method for demonstrating the use of the carrier to improve the effective utilization rate of the pesticide comprises at least the following steps:

[0026] Ⅰ: Mix and stir the same volume of 500mg / L carbon dot solution and 1000-4000mg / L flonicamid solution. The two are combined by physical adsorption to obtain CDs-Flo nanoformulation. Prepare CDs-Flo nanoformulations with different mass ratios, and screen out the group with the best insecticidal effect through bioassay experiments on aphids.

[0027] II: Three types of flonicamid formulations with the same content of active ingredients were prepared, and the insecticidal effects of CDs-Flo nanoformulation, commercially available 10% flonicamid water dispersible granules and flonicamid original drug on pea aphids were tested by leaf dipping method;

[0028] III: Prepare three formulations of flonicamid with an effective concentration of 50 mg / L, fix the broad bean leaves with the front side facing up on a glass slide with transparent tape, use a microsyringe to draw up the test agent and drop it on the top of the leaves, add 1.5 μL each time, and use a measuring instrument to take a picture of the contact angle. Calculate the contact angle and adhesion work value by Young-Equation fitting analysis method.

[0029] Furthermore, the fluorescence intensity of the carbon dot solution in step I continuously decreases with the increase of the concentration of the flonicamid solution. When the mass ratio of the carbon dot solution to the flonicamid solution is 1:5, the maximum mortality rate of aphids is 55.13%.

[0030] Furthermore, the contact angle of the CDs-Flo nanoformulation on the plant leaves in step II and step III is the smallest, and the lethal concentration to pea aphids is also the smallest.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention adopts a one-step hydrothermal method to prepare Commelina communis carbon dots, which can promote the absorption of Fe elements in plants and the synthesis of chlorophyll in plant leaves, and can increase the activity of protective enzymes in plants, thereby promoting plant growth and improving its antioxidant capacity;

[0033] 2. The present invention uses Commelina communis carbon dots as a pesticide carrier, carries flonicamid, and constructs a carbon dot-fluonicamid nanoformulation (CDs-Flo). It is found that the carbon dots can effectively enhance the insecticidal effect of flonicamid, showing excellent biological performance;

[0034] 3. The weed-derived carbon dots provided by the present invention significantly promote the growth of Chinese cabbage. The carbon dots enhance the absorption of Fe by Chinese cabbage, thereby promoting the synthesis of plant chlorophyll and enhancing plant photosynthesis. The carbon dots enhance the scavenging ability of Chinese cabbage for active oxygen and free radicals, and enhance the antioxidant and stress resistance of the plant. The carbon dots can effectively improve the insecticidal effect of flonicamid, and the CDs-Flo nanoformulation has a greater adhesion work value on plant leaves, and has the best lethal effect on pea aphids. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0036] Figure 1 : are fluorescence spectra of carbon dots prepared under different reaction conditions; A is the fluorescence spectra of carbon dots prepared with different amounts of Commelina communis added, B is the fluorescence spectra of carbon dots prepared with different reaction times, and C is the fluorescence spectra of carbon dots prepared with different reaction temperatures;

[0037] Figure 2 The figures are the appearance and atomic force microscope images of carbon dots; A is the appearance of carbon dots under sunlight, B is the appearance of carbon dots under 365nm ultraviolet light, and C is the atomic force microscope image of carbon dots;

[0038] Figure 3 is the XPS scan of carbon dots; A is the full XPS spectrum of carbon dots, and BD is the C 1S 、N 1S and O 1S Spectrum graph;

[0039] Figure 4 is the structural representation diagram of carbon dots; A is the infrared spectrum diagram of carbon dots, and B is the X-ray diffraction diagram of carbon dots;

[0040] Figure 5 This is a graph showing the effect of different concentrations of carbon dot solutions on the growth of pakchoi;

[0041] Figure 6 The figure shows the effect of different concentrations of carbon dots on the growth of Chinese cabbage; A shows the effect of carbon dots on the root length of Chinese cabbage, B shows the effect of carbon dots on the plant height of Chinese cabbage, and C shows the effect of carbon dots on the fresh weight of Chinese cabbage;

[0042] Figure 7 This is a confocal microscopy image of the cross-section of the root, stem and leaf of Chinese cabbage after being treated with carbon dot solution;

[0043] Figure 8 A is the graph of Fe content in pakchoi after being treated with carbon dot solution, and B is the graph of chlorophyll content in pakchoi leaves after being treated with carbon dot solution;

[0044] Fig. 9 The figure is the effect of carbon dot solution treatment on the protective enzyme activity of pakchoi; A is the effect of carbon dot solution treatment on the SOD activity in pakchoi, B is the effect of carbon dot solution treatment on the POD activity in pakchoi, and C is the effect of carbon dot solution treatment on the CAT activity in pakchoi;

[0045] Fig.10A is the fluorescence spectra of carbon dots in response to different concentrations of flonicamid solution, and B is the mortality rate of CDs-Flo nanoformulations with different mass ratios to pea aphids;

[0046] Fig.11 This is a graph showing the change in adhesion work value of different dosage forms of flonicamid solution over time. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] Embodiment 1:

[0049] A method for preparing a novel weed-derived carbon dot comprises at least the following steps:

[0050] S1: Pick fresh stems and leaves of Commelina communis, wash them with deionized water, and then put them into a juicer to crush and stir them to obtain plant homogenate;

[0051] S2: Weigh 0.1-3.5 g of plant homogenate, add 10 mL of deionized water, place in a 20 mL polytetrafluoroethylene reactor, and heat in an oven at 160°C-280°C for 6 h-14 h;

[0052] S3: After the carbon dot solution prepared in S2 is cooled to room temperature, it is centrifuged at 8000 r / min for 10 min, the supernatant is taken, and filtered with a 0.22 μm microporous membrane;

[0053] S4: Pour the carbon dot solution prepared in S3 into a three-necked flask, use a pipette to measure 0.1 mL of 20% PEI solution, add it dropwise into the three-necked flask, and stir in an 80°C oil bath to react for 4 h;

[0054] S5: freeze-dry the PEI-modified carbon dot solution to obtain carbon dot solid, and store it in a sealed container at 4°C.

[0055] In S2, the amount of plant homogenate added was 2 g, the constant temperature heating reaction time was 11 h, and when the reaction temperature was 240 °C, the fluorescence intensity of the carbon dots reached the maximum value, and this condition was determined to be the optimal preparation condition for the carbon dots.

[0056] Embodiment 2:

[0057] A novel weed-derived carbon dot is used to promote plant growth. The novel weed-derived carbon dots obtained by the preparation method of the novel weed-derived carbon dots in Example 1 promote plant growth.

[0058] The method of demonstrating the application of plant promotion shall include at least the following steps:

[0059] A: According to the preparation method of a novel weed-derived carbon dot according to claim 1, carbon dot solutions with concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 500 mg / L, 1000 mg / L and 2000 mg / L were prepared in sequence, and the carbon dot solutions were added to culture dishes containing pakchoi seeds, 15 mL was added to each dish, and deionized water without carbon dots was used as a blank control. On the 9th day, the growth indicators of pakchoi treated with carbon dot solutions of each concentration were measured;

[0060] B: Treat the seeds of Chinese cabbage with 500mg / L carbon dot solution, and observe the roots, stems and leaves of the cabbage under laser confocal microscopy. Under laser confocal microscopy, the fluorescence signals of carbon dots in the roots, stems and leaves of Chinese cabbage can be obtained, and the fluorescence signal of the roots of Chinese cabbage is the strongest, while the fluorescence signals in the stems and leaves are weaker, so as to study the absorption and transportation of carbon dots in plants;

[0061] C: The roots and leaves of the pakchoi treated with carbon dots were dried and ground into powder. The sample was accurately weighed into a 50 mL beaker, and 10 mL of mixed acid (HClO:HNO3=1:9) was added to digest at 300 °C. The digestion solution was then transferred to a 10 mL volumetric flask, fixed to volume with deionized water, and the Fe content in the pakchoi was determined by inductively coupled plasma mass spectrometry.

[0062] D: The chlorophyll content in the leaves of Chinese cabbage after the control group and carbon dots treatment was measured using a chlorophyll meter;

[0063] E: Accurately weigh 0.1g of pakchoi roots and leaves, treat with liquid nitrogen, add 0.9mL of extract, grind into homogenate on ice, centrifuge at 8000r / min, 4℃ for 10min in a low-temperature centrifuge, and take the supernatant; determine the SOD, POD and CAT enzyme activities in pakchoi according to the steps and methods in the kit instructions. The results showed that carbon dot treatment significantly increased the activities of three protective enzymes SOD, POD and CAT in pakchoi.

[0064] Based on the blank control step A, the carbon dot solution has a certain promoting effect on the growth of Chinese cabbage, and at a concentration of 500 mg / L, the promoting effect on the growth of Chinese cabbage is most significant.

[0065] When the Fe content in pakchoi was measured based on step C, the Fe content in the roots, stems and leaves of pakchoi treated with 500 mg / L carbon dot solution increased to a certain extent, and the Fe content in the stems increased most significantly.

[0066] Based on the chlorophyll content determination in step D, the chlorophyll content in the pakchoi slices treated with 500 mg / L carbon dot solution was significantly increased on the 5th and 10th days.

[0067] Embodiment 3

[0068] A novel weed-derived carbon dot is used as a carrier to improve the effective utilization rate of pesticides. The novel weed-derived carbon dots obtained by the preparation method of the novel weed-derived carbon dots in Example 1 are used as a carrier to improve the effective utilization rate of pesticides.

[0069] The method for demonstrating the use of a carrier to improve the effective utilization rate of pesticides includes at least the following steps:

[0070] Ⅰ: Mix and stir the same volume of 500mg / L carbon dot solution and 1000-4000mg / L flonicamid solution. The two are combined by physical adsorption to obtain CDs-Flo nanoformulation. Prepare CDs-Flo nanoformulations with different mass ratios, and screen out the group with the best insecticidal effect through bioassay experiments on aphids.

[0071] II: Three types of flonicamid formulations with the same content of active ingredients were prepared, and the insecticidal effects of CDs-Flo nanoformulation, commercially available 10% flonicamid water dispersible granules and flonicamid original drug on pea aphids were tested by leaf dipping method;

[0072] III: Prepare three formulations of flonicamid with an effective concentration of 50 mg / L, fix the broad bean leaves with the front side facing up on a glass slide with transparent tape, use a microsyringe to draw up the test agent and drop it on the top of the leaves, add 1.5 μL each time, and use a measuring instrument to take a picture of the contact angle. Calculate the contact angle and adhesion work value by Young-Equation fitting analysis method.

[0073] In step I, the fluorescence intensity of the carbon dot solution decreased continuously with the increase of the concentration of the flonicamid solution. When the mass ratio of the carbon dot solution to the flonicamid solution was 1:5, the maximum mortality rate of aphids was 55.13%.

[0074] The contact angle of the CDs-Flo nanoformulation on plant leaves in steps II and III was the smallest, and the lethal concentration to pea aphids was also the smallest.

[0075] Based on the above three embodiments, the following test methods are proposed:

[0076] 1. Preparation and characterization of carbon dots

[0077] (1) Pick fresh Commelina stalks and leaves, wash them with deionized water, put them into a juicer, crush and stir them, and take them out when the plants are homogenized. Accurately weigh 0.1-3.5g Commelina stalks, add 10mL deionized water, place them in a 20mL polytetrafluoroethylene reactor, and heat them in an oven at 160℃-280℃ for 6-14h. After the reactor cools to room temperature, take it out, centrifuge it at 8000r / min for 10min, take the supernatant, and filter it with a 0.22μm microporous membrane. Prepare 20mL of 20% PEI solution for use, pour the filtered carbon dot solution into a three-necked flask, use a pipette to measure 0.1mL of 20% PEI solution, add it dropwise into the three-necked flask, stir and react in an 80℃ oil bath for 4h, cool it to room temperature, take it out, freeze-dry it to obtain carbon dot solid, and seal it in a refrigerator at 4℃.

[0078] (2) The prepared carbon dots were analyzed for morphology and structure using atomic force microscopy, fluorescence spectrophotometer, Fourier transform infrared spectrometer, X-ray diffractometer, etc.

[0079] 2. Effect of carbon dots on plant growth

[0080] (1) Prepare carbon dot solutions with concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 500 mg / L, 1000 mg / L and 2000 mg / L for use. Select pakchoy seeds with full grains, disinfect and clean them with 10% sodium hypochlorite solution, select 15 pakchoy seeds after germination and place them in a 12 cm × 12 cm culture dish covered with two layers of filter paper, add the prepared carbon dot solution to the culture dish, add 15 mL each, use deionized water without carbon dots as a blank control, and repeat each concentration 3 times. Place the culture dish in a constant temperature culture room at 25°C, shade it for the first 3 days, and culture it under a light condition of 14L:10D for the next 6 days. On the 9th day, measure the growth index of pakchoy after treatment with carbon dot solutions of various concentrations.

[0081] (2) Chinese cabbage was treated with 500 mg / L carbon dot solution and deionized water. The roots, stems and leaves of the Chinese cabbage were sliced ​​and observed under a laser confocal microscope to study the absorption and transport of carbon dots in the Chinese cabbage.

[0082] 3. Study on the growth-promoting mechanism of carbon dots on plants

[0083] (1) The pakchoi treated with carbon dot solution was cleaned with deionized water, and the roots and leaves were cut and dried at 50°C. After drying, the samples were crushed and ground. Each treatment group was repeated 3 times, and the pakchoi treated with deionized water was used as the blank control group. Accurately weigh the pakchoi sample in a 50mL beaker, add 10mL of mixed acid (HClO:HNO3=1:9), and digest at 300°C in a well-sealed digestion device in a fume hood. When the test solution is clear and transparent and no plant tissue is visible, it is considered to be completely digested. The digestion solution is transferred to a 10mL volumetric flask, fixed to volume with deionized water, and sealed for later use. The Fe content in pakchoi was determined by inductively coupled plasma mass spectrometry.

[0084] (2) Place fresh plant leaves on the measuring instrument and measure the chlorophyll content in the leaves after calibration.

[0085] (3) Pick the roots and leaves of fresh Chinese cabbage and clean them. Accurately weigh 0.1 g of the plant, treat it with liquid nitrogen, add 0.9 mL of extract, and grind it into a homogenate in a pre-cooled mortar on ice. Centrifuge it in a low-temperature centrifuge at 8000 r / min and 4°C for 10 minutes, take the supernatant, and place it on ice for testing. Determine the SOD, POD and CAT enzyme activities in Chinese cabbage according to the steps and methods in the kit instructions.

[0086] 4. Construction of CDs-Flo Nanoformulation

[0087] (1) Prepare 500 mg / L carbon dot solution and 1000-4000 mg / L flonicamid solution, mix and stir the same volume of carbon dot solution and flonicamid solution, and combine the two by physical adsorption to obtain CDs-Flo nanoformulation. The change of fluorescence value after the carbon dots and flonicamid solutions of different concentrations are measured to detect whether the two are successfully combined.

[0088] (2) CDs-Flo nanoformulations with different mass ratios were prepared, and the group with the best insecticidal effect was screened out through aphid bioassay experiments to determine that it was the optimal combination ratio of carbon dots and flubendiamide. The CDs-Flo nanoformulations required for subsequent experiments were prepared using this optimal combination ratio.

[0089] 5. Toxicity determination of different formulations of flonicamid solution to pea aphid

[0090] (1) Three formulations of flonicamid with the same content of active ingredient were prepared, and the insecticidal effects of CDs-Flo nanoformulation, commercially available 10% flonicamid water dispersible granules and flonicamid original drug on pea aphids were tested by leaf dipping method. Broad bean leaves of uniform size were selected and soaked in a series of agents with a concentration gradient of 1-20 mg / L for 30 seconds. The leaves were taken out and dried. The petioles were moisturized and placed in a 12 cm × 12 cm culture dish (2 leaves / dish). Pea aphids on broad bean leaves were lightly picked with a brush, and wingless adult aphids of uniform size were selected and transferred to the treated leaves. There were 30 aphids in one dish, and each concentration was repeated 3 times. The deionized water treatment group was used as a control. Pea aphids were placed in a constant temperature culture room at 25°C and cultured under the light condition of 14L:10D. The death of aphids was observed after 48 hours. The abdomen of aphids was lightly touched with a brush. If there was no reaction, it was considered dead.

[0091] (2) Prepare three types of flonicamid formulations with an effective concentration of 50 mg / L, cut broad bean leaves into appropriate sizes, fix the leaves with the front side facing up on a glass slide with transparent tape, and place them on the stage of the contact angle meter. Use a microsyringe to draw the test agent and drop it on the leaves, adding 1.5 μL each time. The measuring instrument will take a picture of the contact angle between the drug drop and the leaf, and then calculate the contact angle and adhesion work value through the Young-Equation fitting analysis method.

[0092] Results Analysis

[0093] 1. Preparation and characterization of carbon dots

[0094] (1) Figure 1 As shown in (A), when the addition amount is 2g, the fluorescence intensity of the carbon dots reaches a maximum value. When the addition amount of Commelina communis is increased, the fluorescence intensity does not change significantly. From the perspective of energy consumption, 2g is selected as the optimal addition amount of the raw material. Figure 1 As shown in (B), when the hydrothermal time reaches 11h, the fluorescence intensity reaches the maximum value. If the reaction time is increased, the fluorescence intensity begins to decrease. Therefore, 11h is selected as the optimal reaction time. Figure 1 As shown in (C), when the reaction temperature reaches 240℃ and 260℃, the fluorescence intensity stabilizes near the highest point. When the temperature rises to 280℃, the fluorescence intensity begins to decrease. From an energy perspective, 240℃ is selected as the optimal reaction temperature.

[0095] (2) A stable yellow carbon dot solution was obtained under the optimal preparation conditions, such as Figure 2 As shown in (A) and (B), the Commelina communis carbon dots prepared in this experiment have strong fluorescence properties. The morphology of the carbon dots was observed by atomic force microscopy. Figure 2 As shown in (C), the carbon dots are evenly distributed and small in size, with an average particle size of 6.88 nm.

[0096] like Figure 3 As shown in (A), the carbon dots contain three elements: carbon, nitrogen and oxygen, with contents of 71.68%, 10.98% and 17.14% respectively. Figure 3 The peaks at 287.83 eV, 285.90 eV, and 284.68 eV in (B) correspond to C=O, CO, and C=C. Figure 3 The peaks at 401.73 eV and 399.33 eV in (C) correspond to the functional groups CNC and NH. Figure 3 The peak at 532.18 eV in (D) corresponds to C-OH, and the peak at 531.13 eV corresponds to C=O. XPS results show that the surface of carbon dots contains characteristic functional groups such as carbon-carbon double bonds, amino groups, hydroxyl groups and carboxyl groups.

[0097] like Figure 4 (A) 2964.59cm -1 The stretching vibration peak of the alkyl group is 1652.99 cm -1 The stretching vibration absorption peak of -C=C- is 1581.63cm -1 The stretching vibration absorption peak of -NH2 is 1384.89cm -1 The stretching vibration absorption peak of saturated carboxylic acid is 1124.50 cm -1 The peak at the right is the stretching vibration peak of the hydroxyl group, indicating that there are functional groups such as alkyl, amino, carboxyl and hydroxyl groups on the surface of the carbon dots, which is consistent with the above XPS results. Figure 4 (B) It can be seen that the carbon dots have a broad characteristic absorption peak at around 2θ=28°, which is the characteristic diffraction peak of carbon. The figure shows an amorphous carbon phase, indicating that there are highly disordered carbon atoms inside the carbon dots.

[0098] 2. Effects of carbon dots on plant growth

[0099] (1) Figure 5 As shown in (A) and (B), compared with the control group, the root length of Chinese cabbage treated with carbon dot solution increased significantly, the plant height increased significantly, and the leaves grew better. Figure 6 As shown, when the carbon dot treatment concentration was 10-500 mg / L, the root length of Chinese cabbage increased significantly; when the carbon dot treatment concentration was 200-500 mg / L, the plant height of Chinese cabbage increased significantly; when the carbon dot treatment concentration was 200-2000 mg / L, the fresh weight of Chinese cabbage increased significantly. At a concentration of 500 mg / L, the effect of promoting the growth of Chinese cabbage was the most significant. Different letters in the figure indicate significant differences, P<0.05, and the LSD test in One-way ANOVA was used, the same below. Figure 7In (C)(F)(I), the fluorescence signals of carbon dots in the roots, stems and leaves of Chinese cabbage can be clearly observed, indicating that carbon dots can be absorbed and conducted in Chinese cabbage. By comparing the intensity of the fluorescence signals in Figures (C)(F)(I), it is found that the absorption of carbon dots is from the roots to the stems and then to the leaves.

[0100] (2) Figure 8 As shown in (A), after being treated with 500 mg / L carbon dot solution, the Fe content in the roots, stems and leaves of Chinese cabbage increased to a certain extent, with the most significant increase in the stems. Carbon dots can increase the Fe content in plants. Figure 8 As shown in (B), compared with the control group, the chlorophyll content in the leaves after treatment with 500 mg / L carbon dots solution increased significantly on the 5th and 10th days, indicating that carbon dots can increase the chlorophyll content in the leaves of pakchoi and promote its photosynthesis. Fig. 9 As shown, compared with the control group, the activities of SOD, POD, and CAT in the roots and leaves of Chinese cabbage were significantly improved. Plants cultured in carbon dot solution had better ROS and free radical scavenging ability. Carbon dots can enhance the antioxidant capacity and stress resistance of plants, which is conducive to better plant growth.

[0101] 3. Results of toxicity test of different formulations of flonicamid solution against pea aphid

[0102] (1) By Fig.10 (A) It can be seen that the fluorescence intensity of carbon dots decreases with the increase of the concentration of flonicamid solution, indicating that fluorescence quenching occurs after the carbon dots and flonicamid combine, confirming the successful combination of carbon dots and flonicamid. Fig.10 (B) It can be seen that when the mass ratio of carbon dots to flonicamid gradually increased, the mortality rate of pea aphids showed a trend of first increasing and then decreasing, reaching a maximum mortality rate of 55.13% at 1:5, thereby determining the optimal formula of the CDs-Flo nanoformulation.

[0103] (2) As shown in Table 1, the lethal median concentrations of CDs-Flo nanoformulation, water-dispersible granules and technical drug to pea aphids were 8.988 mg / L, 10.294 mg / L and 12.133 mg / L, respectively. The lethal median concentration of CDs-Flo nanoformulation to pea aphids was the lowest, and its insecticidal effect was better than that of water-dispersible granules and technical drug, indicating that carbon dots can improve the insecticidal effect of flubendiamide to a certain extent.

[0104] Table 1 Toxicity determination of different formulations of flonicamid solution to pea aphid

[0105]

[0106] (3) As shown in Table 2, compared with the original drug, the contact angle of CDs-Flo nanoformulation is significantly reduced; compared with the water-dispersible granules, the contact angle of CDs-Flo nanoformulation is reduced to a certain extent. A smaller contact angle means that when applying the drug, the contact area between CDs-Flo nanoformulation and plant leaves is larger, increasing the possibility of aphids feeding. Fig.11 As shown in the figure, the adhesion work of CDs-Flo nanoformulation is significantly greater than that of the original drug. Compared with the water-dispersible granules, although the difference is not big at the beginning, it gradually shows its advantage over time. This shows that CDs-Flo nanoformulation has better affinity and adhesion to leaves, can adhere to plant leaves more firmly, is not easy to slide off, can reduce the loss of liquid medicine, and improve the effective utilization rate of pesticides.

[0107] Table 2 Contact angle values ​​of different formulations of flonicamid solution

[0108]

[0109]

[0110] The weed-derived carbon dots in the present invention can promote the growth of Chinese cabbage. They are absorbed by the roots of the plant and then transported to the stems and leaves to reach all parts of the plant. The carbon dots can enhance the absorption of Fe by Chinese cabbage to promote plant chlorophyll synthesis and enhance plant photosynthesis. The carbon dots can enhance the scavenging ability of Chinese cabbage to active oxygen and free radicals, and enhance the antioxidant and stress resistance of the plant. The carbon dots can effectively improve the insecticidal effect of flonicamid, and the CDs-Flo nanoformulation has a greater adhesion work value on plant leaves, and has the best lethal effect on pea aphids.

[0111] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing a novel weed-derived carbon dot, characterized in that: At least the following steps are included: S1: Pick fresh stems and leaves of Commelina communis, wash them with deionized water, and then put them into a juicer to crush and stir them to obtain plant homogenate; S2: Weigh 0.1-3.5 g of plant homogenate, add 10 mL of deionized water, place in a 20 mL polytetrafluoroethylene reactor, and heat in an oven at 160°C-280°C for 6 h-14 h; S3: After the carbon dot solution prepared in S2 is cooled to room temperature, it is centrifuged at 8000 r / min for 10 min, the supernatant is taken, and filtered with a 0.22 μm microporous membrane; S4: Pour the carbon dot solution prepared in S3 into a three-necked flask, use a pipette to measure 0.1 mL of 20% PEI solution, add it dropwise into the three-necked flask, and stir in an 80°C oil bath to react for 4 h; S5: freeze-dry the PEI-modified carbon dot solution to obtain carbon dot solid, and store it in a sealed container at 4°C.

2. The method for preparing a novel weed-derived carbon dots according to claim 1, characterized in that: The amount of plant homogenate added in S2 is 2 g, the constant temperature heating reaction time is 11 h, and when the reaction temperature is 240° C., the fluorescence intensity of the carbon dots reaches a maximum value, and this condition is determined to be the optimal preparation condition for the carbon dots.

3. A novel application of weed-derived carbon dots to promote plant growth, characterized in that: The novel weed-derived carbon dots obtained by the method for preparing the novel weed-derived carbon dots according to any one of claims 1 to 2 promote plant growth.

4. The application of the novel weed-derived carbon dots to promote plant growth according to claim 3, characterized in that: The method of demonstrating the application of plant promotion shall include at least the following steps: A: According to the preparation method of a novel weed-derived carbon dot according to claim 1, carbon dot solutions with concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 200 mg / L, 500 mg / L, 1000 mg / L and 2000 mg / L are prepared in sequence, and the carbon dot solutions are added to culture dishes containing pakchoi seeds, 15 mL is added to each dish, and deionized water without carbon dots is used as a blank control. On the 9th day, the growth indexes of pakchoi treated with carbon dot solutions of each concentration are measured; B: Treat the seeds of Chinese cabbage with 500mg / L carbon dot solution, and observe the roots, stems and leaves of the cabbage under laser confocal microscopy. Under laser confocal microscopy, the fluorescence signals of carbon dots in the roots, stems and leaves of Chinese cabbage can be obtained, and the fluorescence signal of the roots of Chinese cabbage is the strongest, while the fluorescence signals in the stems and leaves are weaker, so as to study the absorption and transportation of carbon dots in plants; C: The roots and leaves of the pakchoi treated with carbon dots were dried and ground into powder. The sample was accurately weighed into a 50 mL beaker, and 10 mL of mixed acid (HClO:HNO3=1:9) was added to digest at 300 °C. The digestion solution was then transferred to a 10 mL volumetric flask, fixed to volume with deionized water, and the Fe content in the pakchoi was determined by inductively coupled plasma mass spectrometry. D: The chlorophyll content in the leaves of Chinese cabbage after the control group and carbon dots treatment was measured using a chlorophyll meter; E: Accurately weigh 0.1g of pakchoi roots and leaves, treat with liquid nitrogen, add 0.9mL of extract, grind into homogenate on ice, centrifuge at 8000r / min, 4℃ for 10min in a low-temperature centrifuge, and take the supernatant; determine the SOD, POD and CAT enzyme activities in pakchoi according to the steps and methods in the kit instructions. The results showed that carbon dot treatment significantly increased the activities of three protective enzymes SOD, POD and CAT in pakchoi.

5. The application of the novel weed-derived carbon dots to promote plant growth according to claim 4, characterized in that: Based on the blank control step A, the carbon dot solution has a certain promoting effect on the growth of Chinese cabbage, and at a concentration of 500 mg / L, the promoting effect on the growth of Chinese cabbage is most significant.

6. The application of the novel weed-derived carbon dots to promote plant growth according to claim 4, characterized in that: When the Fe content in pakchoi was measured based on step C, the Fe content in the roots, stems and leaves of pakchoi treated with 500 mg / L carbon dot solution increased to a certain extent, and the Fe content in the stems increased most significantly.

7. The application of the novel weed-derived carbon dots to promote plant growth according to claim 4, characterized in that: Based on the chlorophyll content determination in step D, the chlorophyll content in the pakchoi slices treated with 500 mg / L carbon dot solution was significantly increased on the 5th and 10th days.

8. Application of a novel weed-derived carbon dot as a carrier to improve the effective utilization rate of pesticides, characterized in that: The novel weed-derived carbon dots obtained by the method for preparing the novel weed-derived carbon dots according to any one of claims 1 to 2 are used as carriers to improve the effective utilization rate of pesticides.

9. The use of a novel weed-derived carbon dot as a carrier to improve the effective utilization rate of pesticides according to claim 8, characterized in that: The method for demonstrating the use of a carrier to improve the effective utilization rate of pesticides includes at least the following steps: Ⅰ: Mix and stir the same volume of 500mg / L carbon dot solution and 1000-4000mg / L flonicamid solution. The two are combined by physical adsorption to obtain CDs-Flo nanoformulation. Prepare CDs-Flo nanoformulations with different mass ratios, and screen out the group with the best insecticidal effect through bioassay experiments on aphids. II: Three types of flonicamid formulations with the same content of active ingredients were prepared, and the insecticidal effects of CDs-Flo nanoformulation, commercially available 10% flonicamid water dispersible granules and flonicamid original drug on pea aphids were tested by leaf dipping method; III: Prepare three formulations of flonicamid with an effective concentration of 50 mg / L, fix the broad bean leaves with the front side facing up on a glass slide with transparent tape, use a microsyringe to draw up the test agent and drop it on the top of the leaves, add 1.5 μL each time, and use a measuring instrument to take a picture of the contact angle. Calculate the contact angle and adhesion work value by Young-Equation fitting analysis method.

10. The preparation method and application of a novel weed-derived carbon dots according to claim 9, characterized in that: The fluorescence intensity of the carbon dot solution in step I decreases continuously with the increase of the concentration of the flonicamid solution. When the mass ratio of the carbon dot solution to the flonicamid solution is 1:5, the maximum mortality rate of aphids is 55.13%.

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