Composite nano preparation based on zinc sulfide quantum dots as well as preparation method and application of composite nano preparation

Abstract

The invention discloses a composite nano preparation based on zinc sulfide quantum dots as well as a preparation method and application thereof, and relates to the technical field of nano agriculture and plant disease prevention and control. The nano preparation disclosed by the invention has high antibacterial efficiency, and the prepared ZnSQDs and the composite nano preparation of the ZnSQDs can show a remarkable inhibition effect on the Xanthomonas oryzae pv.oryzae (Xoo) under the condition of an extremely low dosage (2 to 10 mg / L), so that the ZnSQDs and the composite nano preparation of the ZnSQDs can be used for inhibiting the Xanthomonas oryzae pv.oryzae (Xoo) of the Xanthomonas oryzae pv.oryzae (Xoo); compared with the traditional chemical pesticide which can achieve the prevention and treatment effect only through the dosage of 100 milligrams per liter or even gram, the effective dosage of the compound is greatly reduced, and the compound shows ultrahigh antibacterial activity; meanwhile, due to the high specific surface area and active surface sites of the nano-material, the nano-material can be in full contact with pathogenic bacteria, and the action efficiency is improved, so that breeding and diffusion of the pathogenic bacteria can be effectively inhibited in the early stage, and diseases are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of nano-agriculture and plant disease control technology, specifically to a composite nano-formulation based on zinc sulfide quantum dots, its preparation method, and its application. Background Technology

[0002] Rice bacterial blight (Oryza sativa L.) is a serious bacterial disease caused by the Gram-negative bacterium Xanthomonas oryzae epv. oryzae (Xoo). It is one of the most damaging diseases affecting rice production worldwide. This disease is particularly prevalent in Asia, including major rice-producing countries such as China, India, and Japan. Severe outbreaks can lead to yield losses of nearly 50%, posing a significant threat to food security.

[0003] The optimal growth temperature for bacterial blight pathogens is 26-28℃, and the suitable pH range is 6.5-7.5. The pathogen typically invades rice plants through stomata or wounds, multiplying rapidly within the vascular bundles and causing blockages, making it a typical vascular bundle disease. Early symptoms often appear at the leaf tips as small, water-soaked lesions, which then develop wavy, yellowish-white edges and gradually expand to cover the entire leaf. In high humidity, pale yellow bacterial ooze may be visible on affected leaves; in severe cases, leaves turn grayish-green or whitish, the plant wilts and curls, photosynthesis is hindered, ultimately leading to poor panicle development or plant death.

[0004] This pathogen can be transmitted through various routes, including infected seeds, diseased plant debris, irrigation water, wind and rain, agricultural operations, and insects. Outbreaks are more likely to occur when air humidity exceeds 90%, temperatures range from 17 to 35°C, and rainfall is particularly heavy.

[0005] Current control measures for bacterial leaf blight include breeding resistant varieties, strengthening agricultural management, and chemical control. Chemical control is widely used due to its rapid effectiveness and ease of operation; commonly used agents include prochloraz, dithiocyanate, thiamethoxam, thiabendazole copper, kasugamycin, ningnanmycin, and kasugamycin. However, long-term, single-use of chemical agents can easily lead to increased drug resistance in pathogens. Furthermore, pesticide utilization is low, pesticides are easily degraded and lost, posing potential risks to the environment and non-target organisms.

[0006] The rise of nanotechnology has provided new ideas for plant disease control. Metal and metal oxide nanoparticles, due to their high specific surface area, controllable particle size, and good chemical stability, can significantly improve the utilization rate of active ingredients, reduce pesticide dosage, lower environmental pollution, and possess certain antibacterial activity. Zinc sulfide quantum dots (ZnSQDs) are a class of semiconductor crystal materials with three-dimensional dimensions ranging from 2 to 20 nm. They possess excellent small-size effects, chemical stability, and low biotoxicity, and can be used to construct composite nano-formulations through surface modification, finding wide applications in drug delivery and antibacterial fields. Zhongshengmycin (ZS) is a highly effective and low-toxicity biological pesticide widely used to control bacterial plant diseases. Its mechanism of action primarily involves inhibiting the formation of peptide bonds in pathogenic bacterial proteins, ultimately leading to bacterial death, or causing protoplasmic aggregation within fungal hyphae cells, thereby inhibiting the germination of pathogenic fungal spores. In addition, it can stimulate the production of phytoalexins and lignin precursors in plants, thereby improving plant disease resistance and exhibiting good environmental friendliness. However, the use of streptomycin alone still faces problems such as short duration of action, easy degradation, and the development of pathogen resistance. Therefore, utilizing nanomaterials to load or synergize streptomycin to improve its stability, duration of action, and bioactivity has become an important research direction for enhancing its application value.

[0007] Therefore, a new solution is needed to address the above problems. Summary of the Invention

[0008] The purpose of this invention is to provide a composite nano-formulation based on zinc sulfide quantum dots, its preparation method, and its application, so as to solve the technical problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a composite nanoparticle formulation based on zinc sulfide quantum dots, comprising at least the following steps:

[0010] S1: Prepare zinc sulfide quantum dots by reacting zinc acetate and sodium sulfide. The zinc sulfide quantum dots are ZnSQDs.

[0011] S2: Perform surface functionalization modification by introducing chitosan oligosaccharide or polyvinylpyrrolidone onto the surface of ZnSQDs for surface modification. The polyvinylpyrrolidone is PVP-K30, and the chitosan oligosaccharide is COS.

[0012] S3: Drug loading is performed by using electrostatic adsorption and hydrogen bonding to efficiently load kasugamycin (ZS) onto the surface of modified ZnSQDs.

[0013] Furthermore, S1 includes at least the following steps:

[0014] First, prepare 50 ml each of a 0.1 mol / L zinc acetate aqueous alcohol solution and a sodium sulfide aqueous alcohol solution;

[0015] Place the zinc acetate aqueous alcohol solution on a magnetic stirrer and stir at low speed, while slowly adding 1% acetic acid solution to adjust the pH to 5;

[0016] Subsequently, the zinc acetate aqueous alcohol solution was added dropwise to the sodium sulfide aqueous alcohol solution at a rate of 3-4 mL / min, and the reaction was stirred at 350 rpm for more than 40 min.

[0017] After the reaction was completed, the sample was centrifuged at 8000 rpm for 5 min. The resulting precipitate was washed three times with anhydrous ethanol and dried at 60℃ to obtain ZnSQDs powder.

[0018] Furthermore, ZnS-COS is prepared by surface functionalization modification of ZnSQDs using chitosan oligosaccharides. The preparation of ZnS-COS includes at least the following steps:

[0019] Dissolve 1g of chitosan oligosaccharide in 100mL of ultrapure water and stir magnetically until the solution is clear to obtain COS solution;

[0020] 100 mg of ZnSQDs was dispersed in 50 mL of ultrapure water to form a ZnSQDs suspension;

[0021] Under stirring conditions of 350 rpm and 60℃ water bath, 20 mL of COS solution was added dropwise to the suspension at a rate of 4-5 mL / min, and the reaction was allowed to proceed for more than 2 hours.

[0022] The ZnS-COS powder was obtained by centrifugation at 10,000 rpm for 5 min, washing twice with anhydrous ethanol, and freeze-drying.

[0023] Furthermore, ZnS-PVP was prepared by surface functionalization modification of ZnSQDs using vinylpyrrolidone. The preparation of ZnS-PVP includes at least the following steps:

[0024] Dissolve 1g of PVP-K30 in 100mL of ultrapure water and sonicate for 3min to obtain a transparent solution;

[0025] Weigh 100 mg of ZnS QDs and disperse them in 50 mL of ultrapure water to obtain a suspension;

[0026] Under conditions of 350 rpm and 60℃, 20 mL of PVP solution was added dropwise to the suspension at a rate of 4-5 mL / min, and the reaction was allowed to proceed for more than 2 hours.

[0027] The ZnS-PVP powder was obtained by centrifugation at 10,000 rpm for 5 min, washing twice with anhydrous ethanol, and freeze-drying.

[0028] Furthermore, S3 includes at least the following steps:

[0029] Suspensions of 10 mg / L were prepared using ZnS-COS powder and ZnS-PVP powder respectively, and kasugamycin solutions of the same concentration from 2 mg / L to 40 mg / L were also prepared.

[0030] After being ultrasonically dispersed evenly, the mixture was mixed in the same volume ratio and stirred in a water bath at 40°C for 6 hours.

[0031] The obtained suspension was centrifuged at 8000 rpm for 5 min, and the precipitate was washed three times alternately with anhydrous ethanol and ultrapure water. Finally, it was freeze-dried to obtain ZnS-COS / ZS composite powder and ZnS-PVP / ZS composite powder.

[0032] A composite nano-formulation based on zinc sulfide quantum dots was prepared by a method for preparing a composite nano-formulation based on zinc sulfide quantum dots.

[0033] An application of a composite nano-formulation based on zinc sulfide quantum dots: using a composite nano-formulation based on zinc sulfide quantum dots in a pesticide for controlling bacterial blight in rice.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. The nano-formulations of this invention possess high antibacterial efficiency. The prepared ZnSQDs and their composite nano-formulations exhibit significant inhibitory effects on Xanthomonas oryzaeepv. oryzae (Xoo) at extremely low doses (2–10 mg / L). Compared with traditional chemical pesticides, which typically require doses of hundreds of milligrams per liter or even grams to achieve control effects, this invention significantly reduces the effective dosage and demonstrates extremely high antibacterial activity. Simultaneously, the high specific surface area and active surface sites of the nanomaterials allow for more thorough contact with the pathogen, enhancing the efficiency of action and effectively inhibiting the reproduction and spread of the pathogen in the early stages, thus significantly reducing the occurrence of the disease.

[0036] 2. Excellent sustained-release performance: This invention utilizes materials such as chitosan oligosaccharide (COS) and polyvinylpyrrolidone (PVP) to modify the surface of ZnSQDs, and loads active ingredients such as streptomycin through a nanocomposite method, forming a carrier system with good sustained-release performance. In the field environment, this composite system can significantly reduce the loss of pesticides caused by leaching, volatilization and photodegradation, prolong the residence time of active ingredients on the crop surface, and achieve long-term control. Unlike traditional pesticides that require frequent spraying, this invention can effectively reduce the number of applications, save agricultural operation costs, and ensure long-lasting and stable efficacy.

[0037] 3. Dual control mechanism: Unlike existing pesticides that rely solely on bactericidal action, this invention combines direct bactericidal action with the induction of crop immunity. On the one hand, ZnSQDs can directly disrupt the bacterial cell wall structure, producing reactive oxygen species (ROS), thereby achieving both physical and chemical antibacterial effects. On the other hand, the surface-modified nano-formulation can stimulate the defense response in rice, promoting the activation of plant defense signaling pathways such as salicylic acid (SA) and jasmonic acid (JA), and improving the crop's systemic acquired resistance (SAR). This "two-pronged" control model not only improves disease resistance efficiency but also significantly reduces the risk of pathogens developing drug resistance.

[0038] 4. Environmental friendliness and sustainability: The ZnSQDs and their composite materials used in this invention can produce good control effects at low doses, thereby significantly reducing dependence on chemical pesticides, reducing the accumulation of chemical residues in the field environment, and mitigating damage to soil microbial communities and aquatic ecosystems. At the same time, the chitosan oligosaccharides and other materials used are widely available and have good biodegradability, avoiding secondary pollution problems. Overall, this invention takes into account both crop disease control effects and ecological environmental protection, which is in line with the strategic direction of modern green agriculture and sustainable development. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 The diagram shows the morphology, particle size distribution, and crystal structure of ZnS quantum dots before and after surface modification. Figure 1 a and Figure 1 d represents scanning electron microscope (SEM) and transmission electron microscope (TEM) images of unmodified ZnSQDs; Figure 1 b and Figure 1 e is an image of ZnS-PVPQDs modified with polyvinylpyrrolidone (PVP); Figure 1 c and Figure 1 f is the image of ZnS-COSQDs modified with chitosan oligosaccharide (COS). Figure 1 g–i are particle size distribution diagrams of ZnSQDs, ZnS-PVP and ZnS-COS, respectively; Figure 1 j shows the X-ray diffraction (XRD) pattern of ZnSQDs.

[0041] Figure 2 Infrared spectral characterization of ZnS quantum dots and their composite nano-formulations; Figure 2 a) Comparison of FT-IR spectra of PVP, ZnS-PVP, and ZnS quantum dots; Figure 2 b shows a comparison of the FT-IR spectra of COS, ZnS-COS, and ZnS quantum dots; Figure 2 c represents a comparison of the FT-IR spectra of ZS, ZnS-PVP-ZS, and ZnS-PVP; Figure 2 d represents a comparison of the FT-IR spectra of ZS, ZnS-COS-ZS, and ZnS-COS.

[0042] Figure 3 This is a graph showing the wettability and dynamic behavior of ZnS-based nanoparticles on the surface of rice leaves. Figure 3 a represents the contact angle variation curves of ZnS-PVP containing different concentrations of alkyl glycosides; Figure 3 b is the contact angle variation curve of ZnS-COS containing different concentrations of alkyl glycosides; Figure 3 c represents the dynamic behavior record of materials in droplets on the surface of rice leaves.

[0043] Figure 4 To assess the antibacterial effects of ZnS-based nanomaterials and their composite formulations, Figure 4 a represents the antibacterial rate of ZnS-COS-ZS under different mass ratios; Figure 4 b represents the antibacterial rate of ZnS-PVP-ZS under different mass ratios; Figure 4 c represents a comparison of the antibacterial effects of nano-formulations and mesophilic mycotoxins at equivalent concentrations.

[0044] Figure 5 The combined effects of nanomaterials on rice growth and zinc absorption. Figure 5 Photographs of rice seedlings treated with different nanomaterials (concentration 100 mg / L); Figure 5 b shows a comparison of rice seedling growth under different concentrations (10 mg / L and 100 mg / L) of nanomaterials; Note: Figure 5 In b, "+" indicates the medium-temperature herbicides control group, and "-" indicates the pure water control group; Figure 5 c represents the effect of different nano-preparations on rice root length; Figure 5 d represents the effect on rice plant height; Figure 5 e represents the effect on the fresh weight of rice seedlings; Figure 5 f represents the Zn content in rice tissues after treatment with different ZnS-based formulations. 2+ content.

[0045] Figure 6 The effects of different concentrations of nano-prepared agents on chlorophyll, nitrogen content, and hormone levels in rice leaves were investigated. Figure 6 ab represents the chlorophyll and nitrogen content of rice leaves treated with a nano-formulation concentration of 10 mg / L. Figure 6c and d represent the chlorophyll and nitrogen content of rice leaves treated with a nano-preparation concentration of 100 mg / L. Figure 6 e,h represent the hormone content in the aboveground tissues of rice after treatment with different nano-preparations, including Figure 6 e stands for jasmonic acid (JA) Figure 6 f stands for brassinolide (TRA) Figure 6 g represents salicylic acid (SA). Figure 6 h stands for tryptophan (TRP).

[0046] Figure 7 The effects of different nano-preparations on the defense enzyme systems of rice roots and leaves. Figure 7 a, e represent superoxide dismutase (SOD) activity; Figure 7 b and f represent the activities of polyphenol oxidase (PPO); Figure 7 c,g represents the peroxidase (POD) activity; Figure 7 (d,h) represents the activity of phenylalanine aminolysin (PAL).

[0047] Figure 8 To investigate the effects of different nano-preparations on the root and leaf defense enzyme systems of rice after foliar application. Figure 8 a, e represent superoxide dismutase (SOD) activity; Figure 8 b and f represent the activities of polyphenol oxidase (PPO); Figure 8 (c,g) represents the peroxidase (POD) activity; Figure 8 d,h represents the activity of phenylalanine aminolysin (PAL). Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0049] The formulation of this invention uses monodisperse ZnS quantum dots synthesized by a hydrothermal method as the core, and its surface is modified with polyvinylpyrrolidone (PVP) or chitosan oligosaccharide (COS) to improve its water dispersibility and stability. It is then assembled with kasugamycin (ZS), an agricultural antibiotic, to form stable ZnS-PVP-ZS or ZnS-COS-ZS nanocomposites. This nanomaterial possesses multiple functions, including direct antibacterial activity, sustained-release effect, and induction of crop immunity, thus providing a highly efficient, safe, and green new technical solution for the control of rice bacterial blight.

[0050] Example 1:

[0051] A method for preparing a composite nanoparticle formulation based on zinc sulfide quantum dots includes at least the following steps:

[0052] S1: Preparation of zinc sulfide quantum dots, which are prepared by reacting zinc acetate and sodium sulfide. Zinc sulfide quantum dots are also known as ZnSQDs.

[0053] S2: Surface functionalization modification is carried out by introducing chitosan oligosaccharide or polyvinylpyrrolidone onto the surface of ZnSQDs for surface modification. Polyvinylpyrrolidone is PVP-K30, and chitosan oligosaccharide is COS.

[0054] S3: Drug loading is performed by using electrostatic adsorption and hydrogen bonding to efficiently load kasugamycin (ZS) onto the surface of modified ZnSQDs.

[0055] S1 includes at least the following steps:

[0056] First, prepare 50 ml each of a 0.1 mol / L zinc acetate aqueous alcohol solution and a sodium sulfide aqueous alcohol solution;

[0057] Place the zinc acetate aqueous alcohol solution on a magnetic stirrer and stir at low speed, while slowly adding 1% acetic acid solution to adjust the pH to 5;

[0058] Subsequently, the zinc acetate aqueous alcohol solution was added dropwise to the sodium sulfide aqueous alcohol solution at a rate of 3-4 mL / min, and the reaction was stirred at 350 rpm for more than 40 min.

[0059] After the reaction was completed, the sample was centrifuged at 8000 rpm for 5 min. The resulting precipitate was washed three times with anhydrous ethanol and dried at 60℃ to obtain ZnSQDs powder.

[0060] ZnS-COS was prepared by surface functionalization modification of ZnSQDs using chitosan oligosaccharides. The preparation of ZnS-COS includes at least the following steps:

[0061] Dissolve 1g of chitosan oligosaccharide in 100mL of ultrapure water and stir magnetically until the solution is clear to obtain COS solution;

[0062] 100 mg of ZnSQDs was dispersed in 50 mL of ultrapure water to form a ZnSQDs suspension;

[0063] Under stirring conditions of 350 rpm and 60℃ water bath, 20 mL of COS solution was added dropwise to the suspension at a rate of 4-5 mL / min, and the reaction was allowed to proceed for more than 2 hours.

[0064] The ZnS-COS powder was obtained by centrifugation at 10,000 rpm for 5 min, washing twice with anhydrous ethanol, and freeze-drying.

[0065] ZnS-PVP was prepared by surface functionalization modification of ZnSQDs with vinylpyrrolidone. The preparation of ZnS-PVP includes at least the following steps:

[0066] Dissolve 1g of PVP-K30 in 100mL of ultrapure water and sonicate for 3min to obtain a transparent solution;

[0067] Weigh 100 mg of ZnS QDs and disperse them in 50 mL of ultrapure water to obtain a suspension;

[0068] Under conditions of 350 rpm and 60℃, 20 mL of PVP solution was added dropwise to the suspension at a rate of 4-5 mL / min, and the reaction was allowed to proceed for more than 2 hours.

[0069] The ZnS-PVP powder was obtained by centrifugation at 10,000 rpm for 5 min, washing twice with anhydrous ethanol, and freeze-drying.

[0070] S3 includes at least the following steps:

[0071] Suspensions of 10 mg / L were prepared using ZnS-COS powder and ZnS-PVP powder respectively, and kasugamycin solutions of the same concentration from 2 mg / L to 40 mg / L were also prepared.

[0072] After being ultrasonically dispersed evenly, the mixture was mixed in the same volume ratio and stirred in a water bath at 40°C for 6 hours.

[0073] The obtained suspension was centrifuged at 8000 rpm for 5 min, and the precipitate was washed three times alternately with anhydrous ethanol and ultrapure water. Finally, it was freeze-dried to obtain ZnS-COS / ZS composite powder and ZnS-PVP / ZS composite powder.

[0074] Example 2:

[0075] A composite nano-formulation based on zinc sulfide quantum dots was prepared by the method described in Example 1 above.

[0076] Example 3:

[0077] An application of a composite nano-formulation based on zinc sulfide quantum dots: The composite nano-formulation based on zinc sulfide quantum dots described in Example 2 above is used in a pesticide for controlling bacterial blight in rice.

[0078] See Figure 1 - Figure 8 Based on the above embodiments, the following experimental descriptions are proposed:

[0079] Determination of dynamic contact angle of rice leaves using rice preparations

[0080] When the rice plants reached the 5-7 leaf stage, healthy rice leaves of the same growth stage were harvested and fixed onto glass slides using double-sided tape. A suspension of the ZnS-PVP and ZnS-COS nanomaterials prepared above at a concentration of 100 mg / L was prepared, and different mass concentrations of the surfactant alkyl glycoside were added. 2 μL droplets were injected into the surface of the rice leaves, and the dynamic contact angle was measured and calculated using a high-speed optical measuring instrument. The contact angle value was measured using the sessile droplet method, the droplet profile was analyzed, and the contact angle was calculated using the circle fitting method. The dynamic change of the contact angle within 2 minutes of droplet droplet fall was recorded. The dynamic behavior of the droplet impacting the rice leaf surface was captured and photographed using a high-speed camera. The camera frequency was set to 8000 frames per second, and the resolution was 1280x616. A KD Scientific pump was used to push a syringe (0.33 mm) to generate droplets, which were then released from a height of 0.3 meters. The droplets fell freely, impacting the rice leaves at an impact velocity of 2.42 m / s.

[0081] Antibacterial activity test

[0082] The rice bacterial blight pathogen (Xanthomonas oryzae pv. oryzae, Xoo) was cultured in NB liquid medium, and the bacterial concentration was adjusted to OD. 600 =0.1. The culture medium was inoculated into NB medium containing different concentrations of nano-formulations and cultured at 37℃ with shaking at 180 rpm for 16 h. The OD of the bacterial culture was recorded after culture. 600 The value is used to calculate the antibacterial rate.

[0083] Rice seedling growth index detection

[0084] Rice seedlings were raised to the two-leaf-one-heart stage, and then treated with ZnS-COS, ZnS-PVP, ZnS-COS-ZS, and ZnS-PVP-ZS suspensions at concentrations of 10 mg / L and 100 mg / L, respectively. The control groups were streptomycin (ZS, 10 mg / L), metsulfuron-methyl (+), and pure water (–). On days 3 and 7 after treatment, the chlorophyll content (SPAD value) of the top three leaves was measured using a SPAD-502Plus chlorophyll meter, and the nitrogen content was determined using the Kjeldahl method.

[0085] Physiological and biochemical tests

[0086] At the three-leaf stage of rice, suspensions of ZnS-PVP, ZnS-COS, ZnS-COS-ZS, ZnS-PVP-ZS, and ZS were prepared at 100 mg / L and applied via root irrigation (20 mL / plant) and foliar spraying (5 mL / plant, double-sided spraying), respectively. Deionized water served as a blank control. Rice leaves were collected on days 3 and 7 after treatment, and the activities of disease-resistance-related enzymes were measured: POD (peroxidase) activity, PAL (phenylalanine ammonia-lyase) activity, CAT (catalase) activity, and SOD (superoxide dismutase) activity.

[0087] The levels of defensive hormones such as salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA) were detected by liquid chromatography-mass spectrometry (LC-MS / MS).

[0088] Based on the above embodiments, the following technical verification is proposed:

[0089] (1) Successful preparation of nano-formulations based on ZnS QDs

[0090] A hydrothermal synthesis method was adopted, using zinc acetate and sodium sulfide as reactants, and adjusting the pH conditions of the reaction with 1% glacial acetic acid. By controlling the reaction time and rate, ZnS QDs with an average particle size of about 10 nm were successfully prepared. The surface of the nanomaterials was modified with polyvinylpyrrolidone (PVP) and chitosan oligosaccharide (COS) to prepare ZnS-PVP nanomaterials with a uniform particle size of about 25 nm and ZnS-COS nanomaterials with a particle size of about 33 nm. The nanomaterials were then self-assembled with streptomycin. The successful preparation of the nano-formulation was verified by a series of characterization data.

[0091] (2) Nanoformulations based on ZnS QDs have good stability and adhesion.

[0092] Dynamic contact angle and droplet impact experiments were conducted on hydrophobic rice leaves. The surface-modified zinc sulfide quantum dots showed a smaller contact angle and greater droplet retention on the leaves compared to unmodified nanomaterials. This indicates that ZnS-PVP and ZnS-COS nanomaterials can improve the adhesion of the nanomaterials to rice leaves and enhance the stability of droplets on the leaf surface.

[0093] (3) ZnS-COS-ZS and ZnS-PVP-ZS can enhance the inhibitory effect on rice bacterial blight pathogens.

[0094] Antibacterial experiments were conducted using antibacterial culture media. At a concentration of 10 mg / L, ZnS-COS and ZnS-PVP showed the highest antibacterial rates of 43.0% and 40.3%, respectively, significantly higher than ZnS QDs. The nanomaterials and streptomycin were self-assembled at different mass ratios to prepare a 10 mg / L self-assembled system. At a 1:4 binding ratio, ZnS-COS-ZS and ZnS-PVP-ZS achieved the highest antibacterial rates of 55.3% and 52.8%, respectively, significantly higher than the streptomycin technical grade (10% purity) (P<0.01). This indicates that the prepared nano-formulations have a synergistic effect in controlling rice bacterial blight.

[0095] (4) The nano-formulations based on ZnS QDs all showed significant growth-promoting effects on rice and did not show any adverse effects.

[0096] The effects of ZnS-COS, ZnS-PVP, ZnS-COS-ZS, and ZnS-PVP-ZS suspensions at concentrations of 10 mg / L and 100 mg / L on the growth of rice seedlings were investigated. Root length, plant height, and fresh weight were measured. The results showed that each material and formulation significantly improved root length, plant height, and fresh weight in rice, indicating that they are safe for rice growth and have a positive promoting effect. The determination of chlorophyll and nitrogen content further evaluated the effect of the nano-formulations on rice growth. At 100 mg / L, the increase in chlorophyll and nitrogen content was greater, indicating that nanomaterials can enter the plant and be absorbed and utilized by the plant. They play a positive promoting role in rice growth and nutrient accumulation, have high biocompatibility, and showed no toxicity or adverse effects.

[0097] (5) ZnS-COS-ZS and ZnS-PVP-ZS have good inducing effects on the activity of rice defense enzymes and resistance-related hormones.

[0098] Two application methods, root exposure and foliar spraying, were used, with deionized water as a control group. The enzyme activities of SOD, PPO, POD, and PAL in roots and leaves were measured using a kit. Hormone content of JA, SA, TRA, and TRP in the aboveground parts was determined using liquid chromatography-tandem mass spectrometry. Enzyme activity assays showed that all nanomaterials and formulations promoted enzyme expression to varying degrees, with the nano-formulations ZnS-COS-ZS and ZnS-PVP-ZS showing better effects. Hormone assays indicated that both nanomaterials and nano-formulations significantly activated the SA signaling pathway. Simultaneously, L-tryptophan and tryptophan levels in rice also increased significantly, with the nano-formulations ZnS-COS-ZS and ZnS-PVP-ZS again showing superior effects. These results demonstrate that ZnS QDs-based nano-formulations can significantly promote the expression of antioxidant and disease-resistant enzyme systems in rice and upregulate hormones related to the antioxidant system and abiotic stress.

[0099] In summary:

[0100] ZnSQDs with uniform particle size and good dispersibility were successfully prepared via hydrothermal synthesis. Polyvinylpyrrolidone (PVP) and chitosan oligosaccharide (COS) were then modified onto their surfaces, followed by assembly with streptomycin to form stable composite nano-formulations ZnS-PVP-ZS and ZnS-COS-ZS. Material characterization results verified the structure and composition of the formulations. Droplet adhesion experiments showed that they exhibited higher adhesion and retention on rice leaves. In vitro antibacterial experiments showed that both composite nano-formulations at a concentration of 10 mg / L exhibited significant antibacterial activity against PXO99, the pathogen of rice bacterial blight, with inhibition rates of 55.3% and 52.8%, respectively, significantly superior to streptomycin alone, demonstrating a good synergistic effect. Seedling growth experiments showed that these nano-formulations were non-toxic to rice seedlings and had a growth-promoting effect, significantly increasing root length, plant height, fresh weight, and chlorophyll and nitrogen accumulation levels, demonstrating good biocompatibility. Further analysis of defensive enzyme activity and hormone levels revealed that ZnS-PVP-ZS and ZnS-COS-ZS significantly activated the antioxidant enzyme system in rice, increased the activity of enzymes such as SOD, POD, and PAL, and induced upregulation of the expression levels of TRA and TRP in the salicylic acid (SA) and tryptophan metabolic pathways, thereby enhancing the disease resistance and stress resistance of rice.

[0101] It will be apparent to those skilled in the art that the present 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 its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a composite nanoformulation based on zinc sulfide quantum dots, characterized by: At least comprising the following steps: S1: preparing zinc sulfide quantum dots, i.e. ZnSQDs, by reacting zinc acetate and sodium sulfide; S2: performing surface functionalization modification, introducing chitosan oligosaccharide or polyvinylpyrrolidone, i.e. PVP-K30, to the surface of ZnSQDs for surface modification, and the chitosan oligosaccharide is COS; S3: performing drug loading, and high-efficiency loading of ZS on the surface of modified ZnSQDs by electrostatic adsorption and hydrogen bonding.

2. The method according to claim 1, wherein the preparation method of the composite nano-preparation based on zinc sulfide quantum dots is characterized in that: The S1 at least comprises the following steps: First, prepare 50 ml of 0.1 mol / L zinc acetate aqueous-alcoholic solution and 50 ml of sodium sulfide aqueous-alcoholic solution; Put the zinc acetate aqueous-alcoholic solution on a magnetic stirrer for low-speed stirring, and slowly add 1% acetic acid solution to adjust the pH value to 5; Then, add the zinc acetate aqueous-alcoholic solution to the sodium sulfide aqueous-alcoholic solution at a speed of 3-4 mL / min, and stir the reaction under the condition of 350 rpm for 40 min or more; After the reaction is completed, centrifuge at 8000 rpm for 5 min, wash the obtained precipitate with anhydrous ethanol for 3 times, and dry at 60°C to obtain ZnSQDs powder.

3. The method according to claim 1, wherein the preparation method of the composite nano-preparation based on zinc sulfide quantum dots is characterized in that: The ZnS-COS is prepared by using chitosan oligosaccharide to perform surface functionalization modification on ZnSQDs, and the preparation of the ZnS-COS at least comprises the following steps: Dissolve 1 g of chitosan oligosaccharide in 100 mL of ultrapure water, and magnetically stir until the solution is clear to obtain a COS solution; Take 100 mg of ZnSQDs and disperse them in 50 mL of ultrapure water to form a ZnSQDs suspension; Under the condition of 350 rpm and 60°C water bath stirring, add 20 mL of the COS solution to the suspension at a speed of 4-5 mL / min, and react for 2 h or more; Centrifuge at 10000 rpm for 5 min, wash with anhydrous ethanol for 2 times, and freeze-dry to obtain ZnS-COS powder.

4. The method according to claim 1, wherein the preparation method of the composite nano-preparation based on zinc sulfide quantum dots is characterized in that: The ZnS-PVP is prepared by using ethylene pyrrolidone to perform surface functionalization modification on ZnSQDs, and the preparation of the ZnS-PVP at least comprises the following steps: Dissolve 1 g of PVP-K30 in 100 mL of ultrapure water, and ultrasonically treat for 3 min to obtain a transparent solution; Take 100 mg of ZnS QDs and disperse them in 50 mL of ultrapure water to obtain a suspension; Under the condition of 350 rpm and 60°C, add 20 mL of the PVP solution to the suspension at a speed of 4-5 mL / min, and react for 2 h or more; Centrifuge at 10000 rpm for 5 min, wash with anhydrous ethanol for 2 times, and freeze-dry to obtain ZnS-PVP powder.

5. The method according to claim 1, wherein the preparation method of the composite nano-preparation based on zinc sulfide quantum dots is characterized in that: The S3 at least comprises the following steps: Prepare 10 mg / L suspensions of ZnS-COS powder and ZnS-PVP powder respectively, and prepare 2 mg / L-40 mg / L same-concentration ZS solutions; After ultrasonic dispersion, mix them in the same volume ratio, and stir under the condition of 40°C water bath for 6 h; The obtained suspension was centrifuged at 8000 rpm for 5 min, the precipitate was washed with anhydrous ethanol and ultrapure water alternately for 3 times, and finally freeze-dried to obtain ZnS-COS / ZS composite powder and ZnS-PVP / ZS composite powder.

6. A composite nanoformulation based on zinc sulfide quantum dots, characterized in that: The preparation method of the composite nano-preparation based on zinc sulfide quantum dots is prepared by the method in any one of claims 1-5.

7. Use of a composite nanoformulation based on zinc sulfide quantum dots, characterized in that: The composite nano-preparation based on zinc sulfide quantum dots in claim 6 is used in pesticides for preventing and controlling rice bacterial leaf blight.

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