Method for preparing nano spherical silver powder from mesembryanthemum crystallinum extract
The method for preparing nano-spherical silver powder using ice plant extract solves the problems of agglomeration and uneven particle size of nano-silver powder by utilizing magnetic field and catalyst technology, achieving efficient and low-cost preparation of nano-silver powder, which is suitable for medical antibacterial materials.
Patent Information
- Application Number
- CN202511839033.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-03-06
AI Technical Summary
Existing nano-silver powder preparation processes suffer from poor silver powder agglomeration, sphericity, and particle size uniformity, and require stringent preparation conditions, are costly, and cause serious environmental pollution.
Using ice plant extract as a reducing agent, combined with dispersant, catalyst and magnetic field induction technology, nano-spherical silver powder was prepared through magnetic stirring, azeotropic distillation and other steps. The magnetic field directional constraint force was used to inhibit particle agglomeration, and the catalyst accelerated the reaction to achieve rapid nucleation and uniform particle size.
The process yielded nano-spherical silver powder with high sphericity and good particle size uniformity. It is green, efficient, and low-cost, and suitable for medical antibacterial materials.
Smart Images
Figure CN121607645A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of micro-nano material preparation technology, specifically relating to a method for preparing nano-spherical silver powder using ice plant extract. Background Technology
[0002] Nano-silver powder has broad application prospects, such as in the microelectronics field where it can be used to prepare electronic chips and components, in the military and medical fields where it can be used in graphene coatings and inks to shield electromagnetic waves, and in the new energy field where it can be used for photovoltaic power generation. However, its traditional physicochemical preparation methods can cause certain harm to human health and the environment, and are also too costly and have too long reaction times, which is not in line with the current green development strategy of low carbon and environmental protection.
[0003] Currently, traditional preparation methods typically use chemical reagents as reducing agents to convert silver ions into spherical silver powder. For example, when sodium borohydride is used as a reducing agent, the reaction conditions are quite demanding. Because it reacts with water, the reaction must be carried out in an anhydrous organic solvent, and the moisture content of the reaction system is strictly controlled, making it difficult to obtain spherical silver powder with good sphericity and uniform particle size. In addition, using sodium borohydride as a reducing agent is costly. When silver powder is prepared by reduction with hydrazine hydrate, the silver powder particles are prone to agglomeration, thus affecting the dispersibility and sphericity of the silver powder. More importantly, hydrazine hydrate is toxic, corrosive, and irritating, causing environmental pollution.
[0004] Therefore, the spherical silver powder obtained by the existing preparation process has poor sphericity and particle size uniformity, the silver powder particles are prone to agglomeration, the preparation conditions are harsh, the cost is too high, and it causes environmental pollution. Summary of the Invention
[0005] To address the problems existing in the prior art, the present invention aims to provide a method for preparing nano-spherical silver powder using ice plant extract, which effectively solves the technical problems caused by traditional spherical silver powder preparation processes, such as silver powder agglomeration, poor sphericity and particle size uniformity, harsh preparation conditions, high cost, and environmental pollution.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing nano-spherical silver powder from ice plant extract includes the following steps: Add a dispersant to an aqueous solution of silver nitrate, and then adjust the pH to 3.8-4.2 to obtain mixture A; A dispersant was added to an aqueous solution of ice plant extract to obtain mixture B; Add mixture A to mixture B and mix well to obtain a reaction solution; A catalyst is added to the reaction solution to obtain a growth solution; The growth solution was subjected to magnetic field induction to generate nano-spherical silver powder. After the magnetic field induction was completed, solid-liquid separation and washing were performed to obtain the washing product. Polyol was added to the washing product, and then the product was treated by magnetic stirring. After the magnetic stirring was completed, solid-liquid separation and vacuum drying were performed to obtain nano-spherical silver powder. The preparation process of the ice plant extract includes: The dried ice plant powder was mixed with deionized water to obtain mixture A; The mixture A was subjected to ultrasonic treatment to obtain a crude extract of ice plant; The crude extract of ice plant was extracted with petroleum ether, and the lower extract A was collected after separation of layers. Extraction of the lower layer A with ethyl acetate, followed by separation of the layers, and then collection of the lower layer B. The lower extract B was extracted with n-butanol, and the lower extract C was collected after separation. The lower extract C was heated and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the ice plant extract.
[0007] Preferably, the dispersant is gelatin, gum arabic, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, sodium citrate, or Tween-80.
[0008] Preferably, the dispersant added to the silver nitrate aqueous solution is the same as the dispersant added to the ice plant extract aqueous solution; The total mass of the dispersant added to the silver nitrate aqueous solution and the dispersant added to the ice plant extract aqueous solution is 5 wt.%~16 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution, and the mass of the dispersant added to the silver nitrate aqueous solution is 10%~30% of the total mass of the dispersant. The remaining dispersant is added to the ice plant extract.
[0009] Preferably, the concentration of silver nitrate in the silver nitrate aqueous solution is 0.1 mol / L to 0.5 mol / L; the mass ratio of silver ions in the silver nitrate aqueous solution to the mass ratio of ice plant extract in the ice plant extract aqueous solution is 1:(1.1~9).
[0010] Preferably, mixture B and mixture A are mixed in equal volumes, and then magnetically stirred until homogeneous to obtain a reaction solution; wherein the magnetic stirring speed is 490-510 r / min, the temperature is 32-38℃, and the magnetic stirring time is 28-32 min. Preferably, the catalyst is alcohol dehydrogenase, and the mass of alcohol dehydrogenase is 0.5 wt.% to 5 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution.
[0011] Preferably, when inducing growth medium with a magnetic field, the magnetic field strength is 20 mT to 200 mT, and the induction time is 29 to 31 min.
[0012] Preferably, the mass ratio of the washing product to the polyol is 1:(1~3). When adding polyol to the washing product and treating it by magnetic stirring, the temperature is 90℃~200℃, the magnetic stirring rate is 400 r / min~700 r / min, and the magnetic stirring time is 1~3 h; wherein, the polyol is glycerol, 1,2-propylene glycol, 1,3-propylene glycol or 1,4-butanediol. The temperature for vacuum drying is 77-83℃.
[0013] Preferably, when preparing ice plant extract: The surface area of a single ice plant powder is 0.5 cm. 2 the following; Dried ice plant powder and deionized water were mixed in a mass ratio of 1:(17-19) to obtain mixture A; When ultrasonically treating mixture A, the ultrasonic power is 120 W~240 W, the ultrasonic extraction time is 30 min~60 min, and the temperature is 92-98℃. The volume ratio of the crude extract of ice plant to petroleum ether is 1:(1~3). The volume ratio of the lower extract A to ethyl acetate is 1:(1~3). The volume ratio of the lower extract B to n-butanol is 1:(1~3). The heating temperature of the lower extract C is 60~80℃, and the volume ratio of the lower extract C to the added anhydrous ethanol is 1:(0.8~2).
[0014] The present invention also provides a nanosphere silver powder, characterized in that the nanosphere silver powder is obtained by the method described above for preparing nanosphere silver powder from ice plant extract.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a method for preparing nanospherical silver powder from ice plant extract. A dispersant is added to both an aqueous solution of silver nitrate and an aqueous solution of ice plant extract. The pH of the silver nitrate solution is adjusted before being added to the ice plant extract solution to obtain a mixture. This mixture is then subjected to magnetic stirring, external magnetic field induction, the addition of a catalyst, high-speed centrifugation, azeotropic evaporation, washing, and drying to obtain nanospherical silver powder. In this invention, a magnetic field is used to generate a directional constraint force on the particles in the reaction system, counteracting van der Waals attraction between particles, inhibiting powder agglomeration, and guiding the growth direction of the powder. Combined with a catalyst, this accelerates the reaction process, achieving rapid nucleation and refining and uniformizing the particle size. Azeotropic distillation is used to obtain the nanospherical silver powder, removing hard agglomerations of water molecules formed on the particle surface due to hydrogen bonds and van der Waals forces. The nanospherical silver powder prepared by this invention exhibits high sphericity, good flowability, and high purity. The nanospherical silver powder preparation process provided by this invention is green, efficient, stable, and low-cost, providing technical guidance for the synthesis and preparation of medical antibacterial materials. Attached Figure Description
[0016] Figure 1 This is a SEM image of the spherical silver powder prepared in Example 1 of the present invention.
[0017] Figure 2 This is a SEM image of the spherical silver powder prepared in Example 2 of the present invention.
[0018] Figure 3 The image shows the XRD pattern of the spherical silver powder prepared in Example 3 of this invention.
[0019] Figure 4 This is a bar graph showing the particle size distribution of the spherical silver powder prepared in Example 4 of the present invention.
[0020] Figure 5 This is a bar graph showing the particle size distribution of the spherical silver powder prepared in Example 5 of the present invention.
[0021] Figure 6 This is a SEM image of the spherical silver powder prepared in Comparative Example 1 of this invention.
[0022] Figure 7 This is a SEM image of the spherical silver powder prepared in Comparative Example 2 of this invention.
[0023] Figure 8 This is a SEM image of the spherical silver powder prepared in Comparative Example 3 of this invention.
[0024] Figure 9 This is a SEM image of the spherical silver powder prepared in Comparative Example 4 of this invention.
[0025] Figure 10 This is a flowchart of the method for preparing nano-spherical silver powder from ice plant extract according to the present invention. Detailed Implementation
[0026] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.
[0027] Unless otherwise specified, the following test methods and detection methods are all conventional methods; unless otherwise specified, the reagents and raw materials are all commercially available.
[0028] To address the shortcomings of existing spherical silver powder preparation processes mentioned in the background section of this invention, such as poor sphericity and particle size uniformity, easy agglomeration of silver powder particles, demanding preparation conditions, high costs, and environmental pollution, this invention provides a method for preparing nano-spherical silver powder using ice plant extract. Using ice plant extract as a reducing agent, silver ions are reduced. Through a green synthesis process, nano-spherical silver powder with high sphericity, excellent particle size uniformity, and good dispersibility is obtained. Furthermore, the preparation process of the nano-spherical silver powder provided by this invention is simple and low-cost.
[0029] See Figure 10 The present invention provides a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:(17-19) to obtain mixture A. Mixture A was heated to 95±3℃ and ultrasonically extracted for 30-60 min at an ultrasonic power of 120 W~240 W to obtain a crude extract of *Ipomoea aquatica*. Petroleum ether was added to the crude extract for extraction, and the lower layer A was collected after separation, with a volume ratio of crude extract to petroleum ether of 1:(1~3). Ethyl acetate was added to the lower layer A for extraction, and the lower layer B was collected after separation, with a volume ratio of lower layer A to ethyl acetate of 1:(1~3). n-Butanol was added to the lower layer B for extraction, and the lower layer C was collected after separation, with a volume ratio of lower layer B to n-butanol of 1:(1~3). The lower extract C is heated to 60-80℃ and anhydrous ethanol is added. After cooling and crystallization, the extract is filtered and dried to obtain the ice plant extract. The volume ratio of the lower extract C to the added anhydrous ethanol is 1:(0.8-2).
[0030] S2, add the dispersant to 100 mL of 0.1~0.5 mol / L silver nitrate solution, adjust the pH to 4±0.2 to obtain mixture A; add the dispersant to 100 mL of ice plant extract aqueous solution to obtain mixture B; wherein, the dispersant added to the silver nitrate aqueous solution is the same as the dispersant added to the ice plant extract aqueous solution, and the dispersant can be gelatin, gum arabic, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), sodium citrate or Tween-80; the total mass of the dispersant added to the silver nitrate aqueous solution and the dispersant added to the ice plant extract aqueous solution is 5 wt.%~16 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution, and the mass of the dispersant added to the silver nitrate aqueous solution is 10%~30% of the total mass of the dispersant, and the remaining dispersant is added to the ice plant extract. Mixture A is then added to mixture B, and the mixture is magnetically stirred at 500±10 r / min and 35±3℃ for 28-32 min to obtain a reaction solution. The mass ratio of silver ions in the silver nitrate aqueous solution to ice plant extract in the ice plant extract aqueous solution is 1:(1.1~9). A catalyst is added to the reaction solution to obtain a growth solution. The catalyst can be alcohol dehydrogenase, with a mass of 0.5 wt.%~5 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution is induced in an external magnetic field of 20 mT~200 mT for 29-31 min to obtain a mixture. During magnetic field induction, ice plant extract can be used as a reducing agent to remove Ag from the silver nitrate aqueous solution. + The mixture was reduced to generate nano-spherical silver powder. The mixture was centrifuged at 8000±10 r / min for 2-4 min to separate the solid and liquid phases. It was then washed 3-5 times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 4-6 min at 35±3℃. Polyol was added to the washing product at a mass ratio of 1:(1~3), and the mixture was then magnetically stirred for 1-3 times at 90~200℃ and 400~700 r / min until the liquid level was below half. The mixture was then centrifuged again at 8000±10 r / min for 2-4 min. Excess polyol was discarded, and the centrifuged product was dried in a vacuum drying oven at 80±3℃ for 10-12 h to obtain nano-spherical silver powder. Since hydrogen bonds in water can exacerbate powder agglomeration, non-toxic polyols with higher boiling points than water can be used. High-boiling-point non-toxic polyol azeotropes can effectively remove most water molecules. Therefore, polyols such as glycerol, 1,2-propylene glycol, 1,3-propylene glycol, or 1,4-butanediol are used.
[0031] In the above scheme, the value before "±" is the set value (or nominal value) of the corresponding parameter, and the value before "±" is the deviation value of the corresponding parameter. In the following embodiments, only the set value (or nominal value) of the corresponding parameter is given. It can be understood that the relevant parameters in the following embodiments are within the range of the above set value (or nominal value) ± deviation value, and the technical solution is feasible. In the above scheme of the present invention, the change in solution volume can be ignored when adding dispersant and catalyst to silver nitrate aqueous solution.
[0032] Example 1 This embodiment describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at a power of 120W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:3. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:3. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 60°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.5.
[0033] S2, 0.03 g of gelatin was added to 100 mL of 0.1 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.12 g of gelatin was added to 100 mL of an aqueous solution containing 1.3 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 1 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 200 mT for 30 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 90°C and 400 r / min for 1 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 3 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 12 h to obtain nano-spherical silver powder.
[0034] The SEM image of the nanosphere silver powder obtained in this embodiment, taken using a GeminiSEM500 scanning electron microscope, is shown below. Figure 1 As shown, the spherical silver powder particles obtained in this embodiment are distinct. According to the test, the agglomeration coefficient of the spherical silver powder obtained in this embodiment is 1.5, the sphericity is 79%, and the Span value is 1.0. Therefore, the spherical silver powder obtained in this embodiment has high sphericity and small particle size.
[0035] Example 2 This embodiment describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:17 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted at 120 W for 40 min to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:2.5. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:2.5. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:1. The lower layer, C, was heated to 70°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.2.
[0036] S2, 0.06 g of PVP was added to 100 mL of 0.2 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.24 g of PVP was added to 100 mL of an aqueous solution containing 5 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 2 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 250 mT for 29 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:1.5. The mixture was then magnetically stirred at 100°C and 500 r / min for 1.5 h until the liquid level was below half. The mixture was then centrifuged again at 8000 r / min for 3 min. Excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 12 h to obtain nano-spherical silver powder.
[0037] The SEM image of the nanosphere silver powder obtained in this embodiment, taken using a GeminiSEM500 scanning electron microscope, is shown below. Figure 2 As shown, the spherical silver powder particles obtained in this embodiment are distinct. According to the test, the agglomeration coefficient of the spherical silver powder obtained in this embodiment is 1.5, the sphericity is 72%, and the Span value is 0.86. Therefore, the spherical silver powder obtained in this embodiment has high sphericity and small particle size.
[0038] Example 3 This embodiment describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 50 min at 150 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:1. Ethyl acetate was added to the lower layer, A, and B were collected, with a volume ratio of lower layer A to ethyl acetate of 1:1. n-Butanol was added to the lower layer, B, and C were collected, with a volume ratio of lower layer B to n-butanol of 1:2. The lower layer, C, was heated to 75°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower layer, C, and anhydrous ethanol of 1:1.5.
[0039] S2, 0.12 g of PVA was added to 100 mL of 0.3 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.28 g of PVA was added to 100 mL of an aqueous solution containing 16 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 3 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 300 mT for 31 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 2 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 120°C and 500 r / min for 2 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 2 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 10 h to obtain nano-spherical silver powder.
[0040] The XRD pattern of the nano-spherical silver powder obtained in this embodiment is as follows: Figure 3 As shown, the silver purity was 99.96% when detected using a Bruker D8 X-ray diffractometer, proving that the product of Example 3 is silver and has a very high purity.
[0041] Example 4 This embodiment describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 180 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:1.5. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:1.5. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 65°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.
[0042] S2, 0.075 g of PEG was added to 100 mL of 0.4 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.425 g of PEG was added to 100 mL of an aqueous solution containing 30 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35 ℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 4 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 350 mT for 30 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 4 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:2. The product was then magnetically stirred at 150°C and 600 r / min for 2.5 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 4 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 10 h to obtain nano-spherical silver powder.
[0043] The particle size distribution diagram of the nano-spherical silver powder obtained in this embodiment is as follows: Figure 4 As shown, the average particle size was 75.70 nm, as measured using Nano Measurer 1.2 software.
[0044] Example 5 This embodiment describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 240 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:2. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:2. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:2. The lower layer, C, was heated to 80°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:2.
[0045] S2, 0.15 g of gelatin was added to 100 mL of 0.5 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.45 g of gelatin was added to 100 mL of an aqueous solution containing 48 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; after adding alcohol dehydrogenase catalyst to the reaction solution, a growth solution was obtained, wherein the mass of alcohol dehydrogenase was 5 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 400 mT for 30 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 180°C and 700 r / min for 2 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 3 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 11 h to obtain nano-spherical silver powder.
[0046] The particle size distribution diagram of the nano-spherical silver powder obtained in this embodiment is as follows: Figure 4 As shown, the average particle size was 84.39 nm, as determined by Nano Measurer 1.2 software.
[0047] To further illustrate the effects of the present invention, comparative examples are also provided, as follows: Comparative Example 1 The difference compared to Example 1 is that the proportion of dispersant added is different.
[0048] This comparative example describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 120 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:3. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:3. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 60°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.5.
[0049] S2, 0.0075 g of gelatin was added to 100 mL of 0.1 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.1425 g of gelatin was added to 100 mL of an aqueous solution containing 1.3 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 1 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 200 mT for 30 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35°C. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 90°C and 400 r / min for 1 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 3 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80°C for 12 h to obtain nano-spherical silver powder.
[0050] The SEM image of the nanosphere silver powder obtained in this comparative example, taken using a GeminiSEM500 scanning electron microscope, is shown below. Figure 6 As shown, the sphericity of the spherical silver powder obtained in this comparative example is 43% and the average particle size is 2.6 μm. Therefore, the sphericity of the spherical silver powder obtained in this comparative example is poor and the particle size is too large.
[0051] Comparative Example 2 The difference compared to Example 1 is that no catalyst is added.
[0052] This comparative example describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 120 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:3. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:3. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 60°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.5.
[0053] S2, add 0.03 g of gelatin to 100 mL of 0.1 mol / L silver nitrate solution, adjust the pH of the silver nitrate solution to 4, and obtain mixture A; add 0.12 g of gelatin to 100 mL of an aqueous solution of ice plant extract containing 1.3 g of ice plant extract, and obtain mixture B; then add mixture A to mixture B, and stir magnetically at 500 r / min and 35℃ for 30 min, and then induce in an external magnetic field of 200 mT for 30 min to obtain the mixture. The mixture was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35 ℃. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 90 ℃ and 400 r / min for 1 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 3 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80 ℃ for 12 h to obtain nano-spherical silver powder.
[0054] The SEM image of the nanosphere silver powder obtained in this comparative example, taken using a GeminiSEM500 scanning electron microscope, is shown below. Figure 7 As shown, the spherical silver powder obtained in this comparative example exhibits severe agglomeration. Upon testing, the spherical silver powder obtained in this comparative example has a sphericity of 37%, an agglomeration coefficient of 2.6, and an average particle size of 1.3 μm. Therefore, the spherical silver powder obtained in this comparative example has poor sphericity and excessively large particle size.
[0055] Comparative Example 3 The difference compared to Example 1 is that the azeotropic distillation step is not performed.
[0056] This comparative example describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:19 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 120 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:3. Ethyl acetate was added to the lower layer A for extraction, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:3. n-Butanol was added to the lower layer B for extraction, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 60°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.5.
[0057] S2, 0.03 g of gelatin was added to 100 mL of 0.1 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.12 g of gelatin was added to 100 mL of an aqueous solution containing 1.3 g of ice plant extract to obtain mixture B; mixture A was then added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; alcohol dehydrogenase catalyst was added to the reaction solution to obtain a growth solution, wherein the mass of alcohol dehydrogenase was 1 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was induced in an external magnetic field of 200 mT for 30 min to obtain a mixture. The mixture was centrifuged at 8000 r / min for 3 min, and after solid-liquid separation, it was washed three times with deionized water to obtain a washing product, wherein the washing product was ultrasonically cleaned for 5 min at 35℃ between each washing. The centrifuged product was dried in a vacuum drying oven at 80℃ for 12 h to obtain nano-spherical silver powder.
[0058] The SEM image of the nanosphere silver powder obtained in this comparative example, taken using a GeminiSEM500 scanning electron microscope, is shown below. Figure 8 As shown, the spherical silver powder obtained in this comparative example exhibits severe agglomeration. Upon testing, the agglomeration coefficient of the spherical silver powder obtained in this comparative example is 2.4, the sphericity is 48%, and the average particle size is 0.8 μm. Therefore, the spherical silver powder obtained in this comparative example has poor sphericity and excessively large particle size.
[0059] Comparative Example 4 The difference compared to Example 1 is that the magnetic field induction step is not performed.
[0060] This comparative example describes a method for preparing nano-spherical silver powder using ice plant extract, comprising the following steps: S1, the ice plant is washed with deionized water, dried, and then pulverized into 0.5 cm pieces. 2 The following fragments were collected. The fragments were placed in a beaker, and deionized water was added at a mass ratio of 1:18 to obtain mixture A. Mixture A was heated to 95°C and ultrasonically extracted for 30 min at 120 W to obtain a crude extract of *Ilex chinensis*. Petroleum ether was added to the crude extract for extraction, and the layers were separated. The lower layer, A, was collected, with a volume ratio of crude extract to petroleum ether of 1:3. Ethyl acetate was added to the lower layer, and the layers were separated. The lower layer, B, was collected, with a volume ratio of lower extract A to ethyl acetate of 1:3. n-Butanol was added to the lower layer, and the layers were separated. The lower layer, C, was collected, with a volume ratio of lower extract B to n-butanol of 1:3. The lower layer, C, was heated to 60°C and anhydrous ethanol was added. The mixture was cooled to crystallize, filtered, and dried to obtain the *Ilex chinensis* extract, with a volume ratio of lower extract C to anhydrous ethanol of 1:1.5.
[0061] S2, 0.03 g of gelatin was added to 100 mL of 0.1 mol / L silver nitrate solution, and the pH of the silver nitrate solution was adjusted to 4 to obtain mixture A; 0.12 g of gelatin was added to 100 mL of an aqueous solution of ice plant extract containing 1.3 g of ice plant extract to obtain mixture B; then mixture A was added to mixture B, and the mixture was magnetically stirred at 500 r / min and 35℃ for 30 min to obtain a reaction solution; after adding alcohol dehydrogenase catalyst to the reaction solution, a growth solution was obtained, wherein the mass of alcohol dehydrogenase was 1 wt.% of the mass of silver nitrate in the silver nitrate aqueous solution. The reaction solution was centrifuged at 8000 r / min for 3 min to separate the solid and liquid. It was then washed three times with deionized water to obtain the washing product. During each wash, the product was ultrasonically cleaned for 5 min at 35℃. Glycerol was added to the washing product at a mass ratio of 1:1. The product was then magnetically stirred at 90℃ and 400 r / min for 1 h until the liquid level was below half. The product was then centrifuged again at 8000 r / min for 3 min. The excess glycerol was discarded. The centrifuged product was then dried in a vacuum drying oven at 80℃ for 12 h to obtain nano-spherical silver powder.
[0062] The SEM image of the nanosphere silver powder obtained in this comparative example, taken using a Gemini SEM500 scanning electron microscope, is shown below. Figure 9 As shown, the spherical silver powder obtained in this comparative example exhibits severe agglomeration. Testing revealed that the agglomeration coefficient of the spherical silver powder obtained in this comparative example is 2.5, with an average particle size of 0.8 μm. Therefore, the spherical silver powder obtained in this comparative example has a large particle size.
[0063] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.
[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing nanospherical silver powder with an extract of bryophyllum pinnatum, characterized by, The process comprises the following steps: adding a dispersing agent into an aqueous silver nitrate solution, and then adjusting the pH to 3.8-4.2 to obtain a mixed solution A; adding a dispersing agent into an aqueous solution of ice vegetable extract to obtain a mixed solution B; adding the mixed solution B into the mixed solution A and mixing uniformly to obtain a reaction solution; adding a catalyst into the reaction solution to obtain a growth solution; inducing the growth solution by a magnetic field to generate nanometer spherical silver powder, and then performing solid-liquid separation and washing to obtain a washed product; adding a polyol into the washed product, and then treating by magnetic stirring, and then performing solid-liquid separation and vacuum drying to obtain the nanometer spherical silver powder. The preparation process of the ice vegetable extract comprises the following steps: mixing dry ice vegetable powder with deionized water to obtain a mixture A; performing ultrasonic treatment on the mixture A to obtain a crude ice vegetable extract; extracting the crude ice vegetable extract with petroleum ether, and then taking the lower layer extract A after layer separation; extracting the lower layer extract A with ethyl acetate, and then taking the lower layer extract B after layer separation; extracting the lower layer extract B with n-butanol, and then taking the lower layer extract C after layer separation; heating the lower layer extract C, adding anhydrous ethanol, cooling and crystallizing, filtering and drying to obtain the ice vegetable extract.
2. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. The dispersing agent is gelatin, gum arabic, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, sodium citrate or Tween-80.
3. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. The dispersing agent added into the aqueous silver nitrate solution is the same as the dispersing agent added into the aqueous solution of ice vegetable extract. The total mass of the dispersing agent added into the aqueous silver nitrate solution and the dispersing agent added into the aqueous solution of ice vegetable extract is 5 wt.%-16 wt.% of the mass of silver nitrate in the aqueous silver nitrate solution, the mass of the dispersing agent added into the aqueous silver nitrate solution is 10 %-30 % of the total mass of the dispersing agent, and the remaining dispersing agent is added into the ice vegetable extract.
4. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. In the aqueous silver nitrate solution, the concentration of silver nitrate is 0.1 mol / L-0.5 mol / L; the mass ratio of silver ions in the aqueous silver nitrate solution to the ice vegetable extract in the aqueous solution of ice vegetable extract is 1: (1.1-9).
5. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. The mixed solution B and the mixed solution A are mixed in equal volume, and then magnetic stirring is performed after mixing to obtain a reaction solution; wherein the rotating speed of the magnetic stirring is 490-510 r / min, the temperature is 32-38℃, and the magnetic stirring time is 28-32 min.
6. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. The catalyst is ethanol dehydrogenase, and the mass of the ethanol dehydrogenase is 0.5 wt.%-5 wt.% of the mass of silver nitrate in the aqueous silver nitrate solution.
7. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. When the growth solution is induced by a magnetic field, the strength of the magnetic field is 20 mT-200 mT, and the time of the magnetic field induction is 29-31 min.
8. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. The mass ratio of the washed product to the polyol is 1: (1-3); After the polyol is added into the washed product, the temperature is 90℃-200℃, the magnetic stirring speed is 400 r / min-700 r / min, and the magnetic stirring time is 1-3 h when the treatment is performed by magnetic stirring; wherein the polyol is glycerol, 1,2 propanediol, 1,3 propanediol or 1,4 butanediol; The temperature of the vacuum drying is 77-83℃.
9. The method of claim 1, wherein the silver nano-spherical powder is prepared from the extract of the ice plant. In the preparation of the extract of the A. indica: The area of a single ice leaf powder is 0.5 cm 2 The following; The dried A. indica powder is mixed with deionized water at a mass ratio of 1:(17-19) to obtain a mixture A; In the ultrasonic treatment of the mixture A, the ultrasonic power is 120 W-240 W, the ultrasonic extraction time is 30 min-60 min, and the temperature is 92-98℃; The volume ratio of the A. indica crude extract to petroleum ether is 1:(1-3); The volume ratio of the lower layer extract A to ethyl acetate is 1:(1-3); The volume ratio of the lower layer extract B to n-butanol is 1:(1-3); The heating temperature of the lower layer extract C is 60-80℃, and the volume ratio of the lower layer extract C to the added anhydrous ethanol is 1:(0.8-2).
10. A nanospherical silver powder, characterized by, The nanospherical silver powder is obtained by the method for preparing the nanospherical silver powder from the extract of the A. indica according to any one of claims 1-9.