Nano silicon dioxide solution as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of nano pesticides, and relates to a nano silicon dioxide solution as well as a preparation method and application thereof. The method comprises the steps of water-cooling low-temperature mechanical grinding and polishing treatment, ultrasonic crushing and dispersing treatment and double microfiltration and screening treatment, organic matter impurities in the solution are removed through ultraviolet irradiation treatment, and finally the nano-silica solution product with the specific particle size is obtained. The antibacterial effect and stability of the obtained nano silicon dioxide solution are verified through antibacterial experiments. According to the method provided by the invention, the energy consumption is reduced, the use of harmful chemicals is avoided, and the environmental pollution is reduced. Besides, the quality and the purity of the final product are improved through double screening and purifying steps, so that the nano silicon dioxide has a remarkable effect in the aspect of inhibiting phytopathogens, and a new possibility is provided for realizing green chemistry and sustainable development.

Description

Technical Field

[0001] The invention belongs to the technical field of nano pesticides and relates to a nano silicon dioxide solution and a preparation method and application thereof. Background Art

[0002] The application of pesticides has become the most widely used pest and disease management strategy in crop protection and animal husbandry due to its high efficiency and high benefits. In order to control plant pests and diseases, the use of pesticides is inevitable in agricultural production. However, the high per-hectare usage of these chemicals has led to many environmental and health hazards. Large-scale application of traditional synthetic pesticides to increase agricultural production is not a long-term solution because of their hidden dangers, including short field persistence, resistance of pathogens and pests, high toxicity to humans and beneficial organisms, and negative impacts on the environment (Yadav et al., 2022). These drawbacks and the continued growth in demand for pesticides have stimulated the need for persistent, non-resistant, safer and more environmentally friendly alternatives to replace traditional synthetic pesticides.

[0003] In recent years, the introduction of nanotechnology has brought revolutionary changes to agricultural production and pesticide renewal. Nanopesticides can significantly improve the utilization rate of pesticides due to their unique size effect and large specific surface area, and reduce the impact on the environment through controlled release technology, thus having significant advantages in ensuring the safety of agricultural products and environmental protection (Djiwanti & Kaushik, 2019). Its mechanism is to directly use nanostructures as toxic agents for diseases, or to reformulate existing pesticide active substances using nanocarriers to enhance their performance (Abdelrahman et al., 2021). Specifically, nanopesticides can reduce the amount of pesticides used, prolong the duration of efficacy, and reduce the toxic effects on non-target organisms by precisely controlling the release of the agent. Inorganic nanomaterials have a rigid framework and excellent delivery or transport efficacy, and play a vital role in the successful application of nanopesticides (Barik et al., 2008; Ramezani et al., 2019; Bueno and Ghoshal, 2022). In particular, silica nanoparticles as drug carriers are non-toxic and degradable, making them particularly important in the research and development of nanopesticides.

[0004] In recent years, research on the use of nano-silica as a drug carrier has gradually increased. The application of nano-silica fungicides and adsorbed insecticides has a good sustained-release effect. In addition, nano-silica pesticides have significant stability, with a reflectivity of up to 70% to 80% for ultraviolet rays, which can provide good protection for drugs that are easily decomposed by light (Abdelrahman et al., 2021; Lv et al., 2024). However, there are still many challenges in the process of converting these advanced nanomaterials into actual agricultural products. First, the production process of nano-pesticides is complex and usually involves high-energy synthesis methods, which not only increases costs but also threatens environmental sustainability. Secondly, the stability and biosafety of nano-pesticides also need to be considered to ensure that they can effectively control diseases without harming the environment and human health.

[0005] These problems not only limit the commercial scale production of nanopesticides, but also pose a challenge to environmental safety. Therefore, it is imperative to develop a clean production technology for large-scale production of nano-silica solution that is both economical and environmentally friendly. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a nano-silica solution and a preparation method and use thereof. The method can obtain applicable nano-silica materials through a relatively easy physical method, thereby significantly reducing the energy consumption and ecological environmental risks of the production process, and the obtained nano-silica solution has a significant plant antibacterial effect, which also has obvious advantages from an economic perspective.

[0007] The present invention solves the technical problem by first adopting a technical solution of providing a method for preparing a nano-silicon dioxide solution, comprising: S1: Low temperature mechanical grinding and polishing of silica substrate with the aid of a water cooling system; S2: using ultrasonic crushing and dispersion method to process the polished particle mixture into a nano-scale particle solution; S3: Screening out nanoparticle solutions within a specific particle size range through microfiltration screening method; S4: treating the solution with ultraviolet light to remove organic impurities; S5: Perform microfiltration and screening again to obtain a high-purity product.

[0008] Preferably, the low-temperature mechanical grinding is carried out by controlling the temperature at 0°C to 35°C.

[0009] Preferably, the ultrasonic frequency used in the ultrasonic crushing and dispersion method is 40 kHz to 60 kHz.

[0010] Preferably, the pore size of the filter membrane used in the microfiltration screening is 0.8µm to 0.1µm.

[0011] Further preferably, the microfiltration screening is performed by sequentially using microfiltration membranes of 0.8µm, 0.45µm, 0.22µm and 0.1µm.

[0012] Preferably, the ultraviolet light irradiation treatment uses ultraviolet light with a wavelength of 254 mm, and the treatment time is 22-50 hours.

[0013] The present invention also provides a nano-silicon dioxide solution prepared by the above method, in which the particle size of the nano-silicon dioxide is 10-100 nm; the nano-silicon dioxide solution can be effectively concentrated, and its performance is not affected by dilution after concentration.

[0014] The present invention further provides the use of the nano-silicon dioxide solution obtained by the above method. The nano-silicon dioxide solution has an antibacterial effect and can be used alone as an antibacterial agent, or used as a drug carrier in combination with pesticides to prepare an antibacterial composition.

[0015] The present invention further provides an antibacterial composition, which comprises an effective dose of nano-silicon dioxide solution.

[0016] Preferably, the antibacterial composition further comprises an effective dose of a bactericide.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides an environmentally friendly and efficient method for large-scale production of drug-loaded nano-silica through a series of innovative steps. The method optimizes the preparation process of nanoparticles, ensures the uniformity and purity of the product, and verifies its antibacterial effect through physical and chemical characterization and biological experiments. The present invention not only improves the antibacterial application performance of nano-silica, but also reduces the impact of production on the environment, demonstrating the application potential of nanotechnology in the fields of agriculture and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 TEM images of the nano-silicon dioxide solution prepared in the embodiment of the present invention; wherein (a) the reference scale is 20 nm; (b) the reference scale is 200 nm; Figure 2 The figure is a comparison of the colony counts of different treatment groups at 1x colony dilution and the blank group at 200 ppm in the example of the present invention. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Preferred embodiments of the present invention are provided in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0020] Embodiment 1 The method for preparing the nano-silicon dioxide solution provided in this embodiment comprises the following steps: S1: Low temperature mechanical grinding and polishing of silica substrates with the aid of a water cooling system.

[0021] The present invention first uses a diamond grinding wheel to perform preliminary rough grinding on the silica raw material to reduce the silica particle size to a range of 30-1500 nanometers. Then it switches to a resin grinding wheel with a particle size of 240 for fine grinding to further reduce the particle size to 10-300 nanometers. Finally, a BK wheel is used for polishing, and the polishing pressure and speed are adjusted to achieve higher surface finish and particle size consistency.

[0022] The present invention adopts a water cooling system (the water cooling system can use an ordinary faucet to spray water to cool down, improve efficiency, and reduce the loss of the abrasive tool), and uses temperature-controlled water to circulate through the grinding area to quickly take away the generated heat. And the water cooling system plays a role in lubrication and reducing the wear of the wheel caused by frictional heat. The grinding tool uses a diamond grinding wheel grinder, and grinding wheels with grit sizes of 100, 120 and 140 are selected in sequence for preliminary grinding, and controlled in a low temperature environment, for example, the temperature is controlled at -10°C to 10°C. In this way, the material structure damage caused by high temperature can be significantly reduced, and the generation of microcracks caused by thermal stress can be avoided, ensuring the structural and chemical integrity of the nanoparticles.

[0023] The specific parameters for grinding and polishing are as follows: (1) Rough grinding process: Grinding machine equipped with diamond grinding wheel, integrated water cooling system to control grinding temperature Particle size 100: rotation speed 2000rpm, processing time 10 minutes, the purpose is to roughly reduce the particle size to 1500-1200nm; Particle size 120: rotation speed 2200rpm, processing time 8 minutes, further refined to 1200-500nm; Particle size 140: rotation speed 2400rpm, processing time 6 minutes, refined to 500-300nm.

[0024] (2) Fine grinding process: Replace with a resin grinding wheel with a particle size of 240. The rotation speed is 2600 rpm, the processing time is 5 minutes, and the final target particle size is 100-10nm.

[0025] (3) Polishing process: Use BK wheel, grit 60 and 80 Particle size 60: rotation speed 3000rpm, polishing time 4 minutes, particle size reduced to 150-50nm; Particle size 80: rotation speed 3200rpm, polishing time 3 minutes, the particle size is further reduced to 50-10nm.

[0026] A water cooling system is used throughout the process to keep the material cool, reduce heat generated by friction, and remove tiny debris during the polishing process.

[0027] The water cooling system optimizes the polishing effect through meticulous temperature control and water flow regulation, reduces the roughness of the particles and improves the uniformity and purity of the product. In addition, the water cooling system also helps to reduce the spread of dust in the air, thereby reducing the risk of respiratory exposure, and has a positive impact on the health of operators and the cleanliness of the workshop. The present invention applies this system to the preparation of nano-silicon dioxide, which not only improves the process efficiency, but also ensures the cleanliness of the environment and the quality of the product.

[0028] S2: Ultrasonic crushing and dispersion: During the operation, the silica substrate obtained by water-cooled low-temperature mechanical grinding is placed in an ultrasonic field with a specific frequency of 40kHz-60kHz. By controlling the time for 30 minutes at the frequencies of 40kHz, 50kHz, and 60kHz in sequence, the degree of particle crushing can be effectively controlled to achieve an ideal nano-size distribution. After the ultrasonic crushing and dispersion, the particles are not only smaller in size (the average particle size reaches 36.4 nanometers), but also have better surface properties. This process reflects the innovation of the present invention in achieving sustainable development and high-efficiency production, that is, applying common physical treatment technology to the process of preparing environmentally friendly materials.

[0029] Ultrasonic crushing and dispersion is a critical step in the preparation of nano-silicon dioxide in the present invention, aiming to obtain smaller and more evenly distributed nano-particles. This step uses high-frequency ultrasonic energy to penetrate the medium, and the tiny bubbles generated by the cavitation effect grow and collapse rapidly in the material, and the strong shock wave and high temperature generated can effectively disperse and refine the particles.

[0030] S3: Microfiltration and sieving: One of the key steps in the preparation of nano-silicon dioxide solution in the present invention is microfiltration and sieving. After the ultrasonic crushing in the previous process, the solution contains nanoparticles of different sizes. The purpose of microfiltration and sieving is to remove particles that exceed the target size range to ensure a uniform particle size distribution of the final product.

[0031] The mixed solution treated in step S2 is passed through filter membranes of 0.8µm, 0.45µm, 0.22µm and 0.1µm in sequence. The target nano-silica particles are recovered to the maximum extent through the suction filtration system. In addition, the design of the microfiltration process also fully considers the needs of industrial production, ensuring that this step can be operated quickly and efficiently in large-scale production.

[0032] S4: UV photolysis: The purpose of the present invention is to use ultraviolet light photolysis to directly act on the organic matter in the solution with high-energy photons of ultraviolet light to decompose it, and to help enhance the hydrophilicity of the surface of the nano-silica particles and improve their dispersion stability in aqueous solution. First, ensure that the nano-silica solution is evenly dispersed and the light source is stable before ultraviolet light irradiation to avoid excessive local concentration affecting the purification effect. According to the absorption characteristics of the target organic matter, the most effective ultraviolet light wavelength and irradiation time are selected to achieve the best purification effect, avoiding secondary pollution that may be caused by excessive irradiation. In the present invention, irradiation is performed for 24 hours under ultraviolet light with a wavelength of 254mm to achieve the best purification effect, providing a clean and safe reagent for subsequent antibacterial experiments.

[0033] S5: Microfiltration screening: The purified solution in the present invention is once again passed through microfiltration membranes of 0.8µm, 0.45µm, 0.22µm and 0.1µm, which can ensure that only nanoparticles that meet specific particle size requirements (less than 0.1µm) can pass through the filter membrane, while larger particles or aggregates are effectively removed. The present invention ensures that the nano-silica solution has a consistent particle size and relative stability during the repeated screening process, meeting the requirements for nano-level antibacterial agents.

[0034] S6: Physical and chemical characterization: The present invention characterizes the obtained nano-silica solution by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques. TEM provides high-resolution images to determine the morphology and size distribution of nanoparticles, such as Figure 1 As shown. The TEM image shows uniformly distributed nanoparticles, which are mainly spherical and partially aggregated. The presence of bright spots corresponds to areas with higher atomic numbers of elements. Although the particle sizes vary, they are all in the nanometer scale, with a reference scale of 20 nanometers. This distribution and morphology indicate that nanoparticles with potentially uniform reaction surfaces have been successfully prepared, which may be advantageous in applications such as drug delivery system carriers. DLS test results show that the sample is highly monodisperse with an average diameter of approximately 36.4 nanometers. The cumulative size distribution data also confirmed that the vast majority of particles are concentrated in a strict size range, highlighting the precision of the synthesis process.

[0035] Example 2 Effect and optimization of processing parameters of each step on nano-silicon dioxide particle size in the method of the present invention (1) Effect of different grinding and polishing parameters on nano-silica particle size Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the particle size and morphology of the treated samples. The results are shown in Table 1.

[0036] Table 1 Silica particle size distribution under different grinding and polishing parameters Polishing stage Grinding wheel type granularity Processing parameters Average particle size range (nm) coarse grinding Diamond grinding wheel 100 2000rpm,10min 1500-1200 coarse grinding Diamond grinding wheel 120 2200rpm,8min 1200-500 coarse grinding Diamond grinding wheel 140 2400rpm,6min 500-300 fine grinding Resin wheel 240 2600rpm,5min 300-100 polishing BK Wheel 60 3000rpm,4min 150-50 polishing BK Wheel 80 3200rpm,3min 50-10 .

[0037] From the data in Table 1, it can be seen that in the rough grinding stage, the best effect of reducing the particle size to a smaller range (500-300nm) is achieved when the particle size is 140 and 2400rpm and the processing time is 6 minutes, while less wear and more material is retained; in the fine grinding stage, the resin wheel with a particle size of 240 can refine the particle size to less than 100nm at 2600rpm and a processing time of 5 minutes, which has high efficiency and less damage to the material; in the polishing stage, the BK wheel with a particle size of 80 and a polishing time of 3200rpm and 3 minutes is the best choice, which can further reduce the particle size to 10-50nm, providing sufficient energy to achieve a high degree of surface smoothness and uniformity while avoiding over-processing.

[0038] (2) Optimization of parameters for ultrasonic dispersion, UV photolysis and microfiltration This example aims to optimize the ultrasonic dispersion, UV photolysis and microfiltration steps of nano-silica to ensure that the prepared nano-silica has an ideal size distribution and surface properties, so as to improve its efficacy and stability in antibacterial applications.

[0039] 1. The silica substrate that has been treated by water-cooled low-temperature mechanical polishing is placed in an ultrasonic field of a specific frequency for treatment: 40kHz, 50kHz, and 60kHz for 30 minutes each.

[0040] 2. Use high-energy photons of 254nm ultraviolet light to decompose organic matter in the solution and enhance the hydrophilicity and dispersion stability of nano-silica. The irradiation time is 12h, 24h and 48h respectively.

[0041] 3. The solutions after ultrasonic dispersion and UV photolysis were subjected to microfiltration screening to remove particles beyond the target size range. The pore sizes of the microfiltration membranes were 0.8µm, 0.45µm, 0.22µm, and 0.1µm, respectively.

[0042] The results are shown in Table 2, Table 3 and Table 4 respectively.

[0043] Table 2 Particle size distribution of nano-silicon dioxide at different ultrasonic frequencies Frequency (kHz) Control time (min) Average particle size (nm) Remark 40 30 98.6 Poor dispersion consistency 50 30 53.8 Well dispersed, medium size 60 30 36.4 Optimal dispersion and smallest size .

[0044] Table 3 Decomposition of organic impurities in solution under different illumination times UV wavelength (nm) Irradiation time (hours) Effect Remark 254 12 generally General purification effect 254 24 good Good purification effect 254 48 excellent Best purification effect .

[0045] Table 4 Filtration under different pore size filter membranes Microfiltration membrane pore size (µm) Pass rate (%) Preserve particle consistency 0.8 90 Large particles are not completely removed 0.45 85 Most of the target particles pass through 0.22 75 Ideal particle size 0.1 70 The ideal minimum particle size .

[0046] As can be seen from Table 2, in the ultrasonic crushing and dispersion treatment, a frequency of 60 kHz and a treatment time of 30 minutes provide the best particle size reduction effect and particle dispersibility, and the average particle size reaches 36.4 nm. Figure 1 shown.

[0047] As can be seen from Table 3, in the UV photolysis treatment, irradiation with UV light of 254 nm wavelength for 48 hours can most effectively purify the nano-silica solution, while improving the surface properties of the nanoparticles, enhancing their hydrophilicity and dispersion stability in aqueous solution.

[0048] As can be seen from Table 4, in the microfiltration screening process, the pore size of the filter membrane is the most suitable, which can ensure the minimum particle size while maintaining a high pass rate and particle consistency.

[0049] Example 3 Evaluation of the antibacterial effect of the nano-silicon dioxide solution prepared by the method of the present invention on Botrytis cinerea In order to evaluate the inhibitory ability of the nano-silicon dioxide prepared by the present invention on common plant pathogens, and whether it can be combined with pesticides to achieve an efficient drug-carrying effect, reduce the amount of pesticides used and enhance stability. The present invention uses a common plant pathogen Botrytis cinerea to conduct a series of dilution culture experiments to compare the effects of different concentrations of nano-silicon dioxide and pesticides on the growth of Botrytis cinerea.

[0050] Experimental design: 1. Cultivate Botrytis cinerea: Cultivate Botrytis cinerea on standard PDA medium until it is fully grown.

[0051] 2. Preparation of nano-silica solution and conventional pesticide solution: Prepare 50ppm, 100ppm and 200ppm solutions respectively.

[0052] 3. Dilution culture: Cultivate Botrytis cinerea to OD600=0.112 to ensure that the colony is in the active growth phase. Dilute the colony to different concentrations according to 1x, 10x, 100x, and ensure that the concentration is consistent during inoculation. Add different concentrations of nano-silica solution and pesticide solution to each concentration of bacterial solution. The control group only adds an equal volume of sterile water.

[0053] 4. Experimental grouping: Divided into four groups, namely the control group (no substance added), the pesticide group (methyl thiophanate), the nano-silica group (adding the nano-silica prepared above), and the pesticide and nano-silica combination group (the solvent water of the pesticide was replaced with nano-silica solution). Each group of experiments was repeated three times to ensure the reliability of the results.

[0054] 5. Determination of antibacterial effect: The culture medium was cultured at 22-25°C, and the growth of the colonies was detected periodically. The antibacterial effect of each treatment group was evaluated by measuring the diameter and number of colonies.

[0055] 6. Data recording and analysis: Record the growth data of Botrytis cinerea after different groups of treatments, and compare the antibacterial effects of different treatments through statistical analysis.

[0056] Table 5 Comparison of the inhibitory effects of the nano-silicon dioxide prepared by the present invention and traditional pesticides on Botrytis cinerea at different dilution concentrations Dilution Treatment Group Concentration (ppm) Antibacterial rate on the 7th day (%) Antibacterial rate on the 14th day (%) 1x Nano-silicon dioxide + pesticide 50 65% 50% 1x Nano-silicon dioxide + pesticide 100 75% 60% 1x Nano-silicon dioxide + pesticide 200 85% 70% 10x Nano-silicon dioxide + pesticide 200 80% 65% 100x Nano-silicon dioxide + pesticide 200 75% 60% 1x Nano Silica 50 30% 15% 1x Nano Silica 100 40% 25% 1x Nano Silica 200 50% 35% 10x Nano Silica 200 45% 30% 100x Nano Silica 200 40% 25% 1x Pesticides only 50 45% 30% 1x Pesticides only 100 55% 40% 1x Pesticides only 200 65% 50% 10x Pesticides only 200 60% 45% 100x Pesticides only 200 55% 40% 1x Sterile water control 0 0% 0% ; Note: Colony diameter refers to the diameter measurement of the colonies on the plate after a specific period of time, in millimeters; the inhibition rate is calculated based on the change in colony diameter; the pesticide is methyl-thiophanate.

[0057] From the data in Table 5, it can be seen that the nano-silicon dioxide solution prepared by the present invention shows a trend of increasing antibacterial effect with increasing concentration. When the nano-silicon dioxide solution is combined with the pesticide, it shows the best antibacterial effect among all treatments, especially at a higher concentration of 200ppm, the antibacterial rate is as high as 85% on the 7th day and 70% on the 14th day. The antibacterial effect is slightly reduced at different dilutions, but still maintains a high effect, such as Figure 2 shown.

[0058] The antibacterial effect of pesticide treatment alone is stronger than that of nano-silicon dioxide alone, but compared with the untreated control group, the nano-silicon dioxide solution of the present invention itself also has a certain antibacterial ability.

[0059] Example 4 Large-scale production of the method of the present invention and its quality assurance In order to verify the feasibility of large-scale production and quality control of the nano-silicon dioxide solution preparation method provided by the present invention, the present invention carries out a detailed production and testing process, aiming to show how to expand the production scale while maintaining high product quality.

[0060] (1) Raw material preparation: ensure that all raw materials meet the specified purity and quality standards; (2) Water-cooled low-temperature mechanical grinding and polishing: using complete water cooling technology to minimize thermal effects; (3) Ultrasonic dispersion: Ensure uniform dispersion of nanoparticles by adjusting the intensity and time of ultrasound. (4) Continuous microfiltration and screening: Use screening equipment to continuously separate nanoparticles that meet the specifications; (5) UV light purification: remove any potential organic residual impurities; (6) Tail gas treatment and wastewater recycling: ensure that all emissions meet environmental standards and that wastewater is recycled and reused after treatment; (7) Monitoring system: real-time monitoring of key parameters in the production process, such as temperature, pressure and pH value; (8) Sampling testing: samples are taken from the production line for analysis, including particle size distribution, chemical purity and structural integrity; (9) Laboratory simulation test: simulate field conditions in a controlled environment to test the stability and effect of nano-silica solution. The results are shown in Table 6.

[0061] Table 6 Quality control parameters for nano-silicon dioxide production Parameter Category Test items Standard requirements Measured value Physical properties Particle size distribution 90-200nm Meet the standards Chemical properties purity ≥99.5% Meet the standards Environmental safety Waste treatment efficiency Comply with environmental standards Meet the requirements Production efficiency Production cycle Each batch ≤ 48 hours Meet production time requirements .

[0062] It can be seen from Table 6 that the preparation method of the nano-silicon dioxide solution provided by the present invention can be used for large-scale production, and the nano-silicon dioxide solution product obtained by the method meets the relevant standards and has stable quality.

Claims

1. A method for preparing a nano-silicon dioxide solution, characterized in that: The following steps are involved: S1: Low temperature mechanical grinding and polishing of silica substrate with the aid of a water cooling system; S2: using ultrasonic crushing and dispersion method to process the polished particle mixture into a nano-scale particle solution; S3: Screening out nanoparticle solutions within a specific particle size range through microfiltration screening method; S4: treating the solution with ultraviolet light to remove organic impurities; S5: Perform microfiltration again to obtain a high-purity product.

2. The method for preparing a nano silicon dioxide solution according to claim 1, wherein: The low temperature mechanical grinding is carried out under the condition of controlling the temperature between 0°C and 35°C.

3. The method for preparing a nano silicon dioxide solution according to claim 1, wherein: The ultrasonic frequency used in the ultrasonic crushing and dispersing method is 40kHz to 60kHz.

4. The method for preparing a nano silicon dioxide solution according to claim 1, characterized in that: The pore size of the filter membrane used in the microfiltration screening is 0.8µm to 0.1µm.

5. The method for preparing a nano silicon dioxide solution according to claim 1, characterized in that: The microfiltration screening is performed by sequentially using microfiltration membranes of 0.8µm, 0.45µm, 0.22µm and 0.1µm.

6. The method for preparing a nano-silicon dioxide solution according to claim 1, characterized in that: The ultraviolet light irradiation treatment uses ultraviolet light with a wavelength of 254 mm, and the treatment time is 22-50 hours.

7. A nano silicon dioxide solution prepared by the method according to any one of claims 1 to 6, characterized in that: In the solution, the particle size of nano silicon dioxide is 10-100 nm; the nano silicon dioxide solution can be effectively concentrated, and its performance is not affected by dilution after concentration.

8. The use of the nano-silicon dioxide solution according to claim 7, characterized in that: The nano silicon dioxide solution has an antibacterial effect and can be used alone as an antibacterial agent, or used as a drug-carrying substance in combination with pesticides to prepare an antibacterial composition.

9. An antibacterial composition, characterized in that: The antibacterial composition comprises an effective dose of the nano-silicon dioxide solution according to claim 7.

10. The antibacterial composition according to claim 9, characterized in that: The antibacterial composition also contains an effective dose of a bactericide.

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