Preparation method of zero-dimensional spherical nano-silver

Abstract

The invention relates to a preparation method of zero-dimensional spherical nano-silver. The preparation method comprises the following operation steps: (1) preparing a 0.05 mol / L NaHCO3 solution; (2) adding a 0.1 mol / L LAgNO3 solution into a beaker, and then adding PVP (Polyvinyl Pyrrolidone) to obtain a mixture A; (3) adding the mixture A into a 0.05 mol / L NaHCO3 solution, and reacting to obtain an AgCO3 white precipitate solution; (4) pouring the AgCO3 white precipitate solution into a hydrothermal reaction kettle, and then putting the hydrothermal reaction kettle into a drying oven for reaction to obtain a mixture B; and (5) the mixture B is filtered, washed and ground to obtain AgNPS, namely the spherical nano-silver. Zero-dimensional spherical nano-silver is synthesized by regulating and controlling the adding sequence of polyvinylpyrrolidone, generated particles are high in stability, and the agglomeration phenomenon of AgNPs is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of silver nanoparticles, and particularly relates to a method for preparing zero-dimensional spherical silver nanoparticles. Background Art

[0002] During the synthesis of silver nanoparticles (AgNP S ), the shape of the nanomaterials can be controlled by adjusting the preparation conditions, such as rod-shaped, spherical, flaky, etc. Among them, zero-dimensional spherical silver nanoparticles are commonly used in the antibacterial field, one-dimensional silver nanowires are commonly used as conductive additives in the composite field, and two-dimensional silver nanoparticles are commonly used as electrode materials. The preparation methods of AgNPs can be divided into biological methods, physical methods, and chemical methods.

[0003] In the biological method, microorganisms, plant extracts, proteins, polypeptides, etc. are used as reducing agents and stabilizers to reduce Ag+ to Ag 0 . The preparation process of the biological method is environmentally friendly, low-cost, and has good biocompatibility, but the reaction time is long, the yield is low, and the particle size and morphology of AgNPs are not easy to control.

[0004] The physical method is mainly mechanical ball milling. Large-diameter Ag is put into a ball mill for grinding, and the particle size of AgNPs can be controlled by controlling the ball milling time and rotation speed. The AgNPs prepared by the mechanical ball milling method have high purity and uniform particle size, but the equipment cost of the ball milling method is high and the yield of AgNPs is low.

[0005] The chemical method is mainly chemical reduction. An organic solution or an inorganic solution is used as a reducing agent to reduce Ag+ to Ag 0 , and at the same time, a surfactant is added to change the morphology of AgNPs and reduce the aggregation phenomenon. Different surfactants will form different degrees of aggregation on the AgNPs particles, resulting in different shapes and sizes of the AgNPs particles. The chemical reduction method for synthesizing AgNPs has a large output, short time, and low cost, but many reducing agents used in the synthesis process are toxic, require a large amount of surfactant protection, the generated particles have poor stability, are prone to aggregation, and the particle size distribution is uneven. Summary of the Invention

[0006] The purpose of the present invention is to design a method for preparing zero-dimensional spherical silver nanoparticles, which does not require a large amount of surfactant protection, the generated particles have better stability, and the aggregation phenomenon of AgNPs is less.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A method for preparing zero-dimensional spherical silver nanoparticles, comprising the following operating steps:

[0009] (1) Weigh a certain amount of NaHCO₃ and water, and prepare a 0.05 mol / L NaHCO₃ solution;

[0010] (2) Add 0.1 mol / L AgNO₃ solution to a beaker, then add PVP, and stir evenly to obtain mixture A;

[0011] (3) Add mixture A to 0.05 mol / L NaHCO₃ solution, and react to obtain a white precipitate solution of Ag₂CO₃;

[0012] (4) Pour the white precipitate solution of Ag₂CO₃ into a hydrothermal reaction kettle, then place it in an oven for reaction to obtain mixture B;

[0013] (5) Filter mixture B, wash the precipitate by centrifugation with water, then wash it by centrifugation with absolute ethanol. After the absolute ethanol volatilizes, grind it to obtain AgNP S , that is, spherical silver nanoparticles.

[0014] The principle of preparing zero-dimensional spherical silver nanoparticles in the present invention:

[0015] 2AgNO₃ + 2NaHCO₃ = 2Ag₂CO₃ + 2NaNO₃ + H₂O + CO₂

[0016] 2Ag₂CO₃ = 2Ag + 2CO₂ + O₂

[0017] Furthermore, it includes the following operation steps:

[0018] (1) Weigh 0.126 g of NaHCO₃ and 30 mL of deionized water, and prepare 30 mL of 0.05 mol / L NaHCO₃ solution;

[0019] (2) Add 10 mL of 0.1 mol / L AgNO₃ solution to a beaker, place it on a magnetic stirring table, then add 1.7 g of PVP, and stir evenly to obtain a mixture;

[0020] (3) Add the mixture to 0.05 mol / L NaHCO₃ solution, and react to obtain a white precipitate solution of Ag₂CO₃;

[0021] (4) Pour the white precipitate solution of Ag₂CO₃ into a 100 mL hydrothermal reaction kettle, then place it in an oven for reaction, where the initial temperature is room temperature, the final temperature is 180 °C, and the reaction lasts for 5 h to obtain a precipitate;

[0022] (5) Filter the precipitate, wash the precipitate by centrifugation with deionized water 3 times, then wash it by centrifugation with absolute ethanol 3 times. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, then pour it into a mortar and grind it for 3 min to obtain AgNP S, namely spherical nano - silver.

[0023] Furthermore, the deionized water is secondary distilled water.

[0024] Furthermore, the molecular weight of the PVP is 40000.

[0025] Furthermore, the PVP is a PVA with a molecular weight of 10000 and 40000 at a mass ratio of 1:1.

[0026] Furthermore, in step (2), add 10 mL of 0.1 mol / L AgNO3 solution into a beaker, place it on a magnetic stirring table, add 0.360 g of glucose into the solution, stir evenly, and then add 1.7 g of PVP and stir evenly to obtain a mixture.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) In the method of the present invention, spherical nano - silver with an average particle size of less than 40 nm is synthesized by regulating the addition sequence of polyvinylpyrrolidone (PVP); the morphology of AgNPs synthesized by adding PVP before the formation of Ag2CO3 is more spherical than that of AgNPs synthesized by adding PVP after the formation of Ag2CO3, the diameter can be reduced by at least 50%, the generated particles have high stability, greatly reducing the agglomeration phenomenon of AgNPs, and the particle size distribution is uniform.

[0029] (2) Under hydrothermal conditions, without adding any reducing agent, at a relatively high reaction concentration, silver carbonate precipitate is generated by the reaction of AgNO3 and NaHCO3, and the reaction is carried out at a constant temperature in a reaction kettle. Under the dispersion action of PVP, zero - dimensional spherical nano - silver (AgNPs) is formed by hydrothermal decomposition; no reducing agent or glucose is used as a reducing agent during the synthesis process, and no large amount of surfactant protection is required.

[0030] (3) During the synthesis of AgNPs by the hydrothermal method of the present invention, by adding PVP before the formation of Ag2CO3, high - concentration PVP can adhere to each crystal plane of the silver crystal nucleus, and the growth rate of each crystal plane is almost equal, thus obtaining AgNPs.

[0031] (4) The preparation method of the present invention has a simple process, low cost, is easy to control the process, and the reagents used are environmentally friendly. Description of the Drawings

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 SEM image with a magnification of 10KX for Embodiment 1 of the present invention;

[0034] Figure 2 SEM image with a magnification of 50KX for Embodiment 1 of the present invention;

[0035] Figure 3 EDS diagram for Embodiment 1 of the present invention;

[0036] Figure 4 XRD diagram for Embodiment 1 of the present invention;

[0037] Figure 5 SEM image with a magnification of 10KX for Embodiment 2 of the present invention;

[0038] Figure 6 SEM image with a magnification of 50KX for Embodiment 2 of the present invention;

[0039] Figure 7 EDS diagram for Embodiment 2 of the present invention;

[0040] Figure 8 XRD diagram for Embodiment 2 of the present invention;

[0041] Figure 9 SEM image with a magnification of 10KX for Comparative Example 1 of the present invention;

[0042] Figure 10 SEM image with a magnification of 50KX for Comparative Example 1 of the present invention;

[0043] Figure 11 EDS diagram for Comparative Example 1 of the present invention;

[0044] Figure 12 XRD diagram for Comparative Example 1 of the present invention;

[0045] Figure 13 SEM image with a magnification of 10KX for Comparative Example 2 of the present invention;

[0046] Figure 14 SEM image with a magnification of 50KX for Comparative Example 2 of the present invention;

[0047] Figure 15EDS diagram of Comparative Example 2 of the present invention;

[0048] Figure 16 XRD diagram of Comparative Example 2 of the present invention;

[0049] Figure 17 SEM diagram with a magnification of 10KX of Comparative Example 3 of the present invention;

[0050] Figure 18 SEM diagram with a magnification of 50KX of Comparative Example 3 of the present invention;

[0051] Figure 19 EDS diagram of Comparative Example 3 of the present invention;

[0052] Figure 20 XRD diagram of Comparative Example 3 of the present invention; Detailed implementation manners

[0053] The following describes the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0054] Before further describing the specific implementation manners of the present invention, it should be understood that the protection scope of the present invention is not limited to the specific implementation manners described below; it should also be understood that the terms used in the embodiments of the present invention are for describing specific implementation manners, rather than for limiting the protection scope of the present invention.

[0055] When the embodiments give numerical ranges, it should be understood that unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0056] The present invention does not limit the sources of raw materials. Unless otherwise specified, the raw materials used are all ordinary commercially available products.

[0057] Example 1

[0058] A preparation method of zero-dimensional spherical nano-silver, comprising the following operation steps:

[0059] (1) Weigh 0.126 g of NaHCO3 and 30 mL of secondary distilled water, and prepare a 30 mL 0.05 mol / L NaHCO3 solution;

[0060] (2) Add 10 mL of 0.1 mol / L AgNO3 solution into a beaker, place it on a magnetic stirring platform, then add 1.7 g of PVP with a molecular weight of 40000, and stir evenly to obtain a mixture;

[0061] (3) Add the mixture into 0.05 mol / L NaHCO3 solution to react and obtain a white precipitate solution of AgCO3;

[0062] (4) Pour the white precipitate solution of AgCO3 into a 100 mL hydrothermal reaction kettle, then place it in an oven for reaction. The initial temperature is room temperature, the final temperature is 180 °C, and react for 5 h to obtain a precipitate;

[0063] (5) Filter the precipitate, wash the precipitate by centrifugation with deionized water 3 times, then wash it by centrifugation with absolute ethanol 3 times. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, then pour it into a mortar and grind it for 3 min to obtain AgNP S , that is, spherical silver nanoparticles.

[0064] Example 2

[0065] A preparation method of zero-dimensional spherical silver nanoparticles, including the following operating steps:

[0066] (1) Weigh 0.126 g of NaHCO3 and 30 mL of secondary distilled water, and prepare 30 mL of 0.05 mol / L NaHCO3 solution;

[0067] (2) Add 10 mL of 0.1 mol / L AgNO3 solution into a beaker, place it on a magnetic stirring platform, add 0.360 g of glucose to the solution, stir evenly, then add 1.7 g of PVA with a molecular weight ratio of 1:1 of 10000 and 40000, and stir evenly to obtain a mixture;

[0068] (3) Add the mixture into 0.05 mol / L NaHCO3 solution to react and obtain a white precipitate solution of AgCO3;

[0069] (4) Pour the white precipitate solution of AgCO3 into a 100 mL hydrothermal reaction kettle, then place it in an oven for reaction. The initial temperature is room temperature, the final temperature is 180 °C, and react for 5 h to obtain a precipitate;

[0070] (5) Filter the precipitate, wash the precipitate by centrifugation with deionized water 3 times, then wash it by centrifugation with absolute ethanol 3 times. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, then pour it into a mortar and grind it for 3 min to obtain AgNP S , that is, spherical silver nanoparticles.

[0071] Comparative Example 1

[0072] A preparation method of zero-dimensional spherical silver nanoparticles, comprising the following operating steps:

[0073] (1) Weigh 0.126 g of NaHCO3 and 30 mL of secondary distilled water, and prepare a 30 mL 0.05 mol / L NaHCO3 solution;

[0074] (2) Place the beaker containing the NaHCO3 solution on a magnetic stirring table, add 10 mL of 0.1 mol / L AgNO3 solution, and react to obtain a white precipitate solution of AgCO3;

[0075] (3) Weigh and add 1.7 g of PVP with a molecular weight of 10,000 to the solution, stir evenly to obtain a mixture;

[0076] (3) Add the mixture to 0.05 mol / L NaHCO3 solution, and react to obtain a white precipitate solution of AgCO3;

[0077] (4) Pour the white precipitate solution of AgCO3 into a 100 mL hydrothermal reactor, then place it in an oven for reaction, where the initial temperature is room temperature, the final temperature is 180 °C, and react for 5 h to obtain a precipitate;

[0078] (5) Filter the precipitate, wash the precipitate 3 times by centrifugation with deionized water, and then wash 3 times by centrifugation with absolute ethanol. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, then pour it into a mortar and grind for 3 min to obtain AgNP S , that is, spherical silver nanoparticles.

[0079] Comparative Example 2

[0080] A preparation method of zero-dimensional spherical silver nanoparticles, comprising the following operating steps:

[0081] (1) Weigh 0.126 g of NaHCO3 and 30 mL of secondary distilled water, and prepare a 30 mL 0.05 mol / L NaHCO3 solution;

[0082] (2) Place the beaker containing the NaHCO3 solution on a magnetic stirring table, add 10 mL of 0.1 mol / L AgNO3 solution, and react to obtain a white precipitate solution of AgCO3;

[0083] (3) Weigh and add 1.7 g of PVP with a molecular weight of 40,000 to the solution, stir evenly to obtain a mixture;

[0084] (3) Add the mixture to 0.05 mol / L NaHCO3 solution, and react to obtain a white precipitate solution of AgCO3;

[0085] (4) Pour the AgCO3 white precipitate solution into a 100 mL hydrothermal reaction kettle, and then place it in an oven for reaction. The initial temperature is room temperature, the final temperature is 180 °C, and the reaction lasts for 5 h to obtain a precipitate.

[0086] (5) Filter the precipitate, centrifuge and wash the precipitate 3 times with deionized water, and then centrifuge and wash it 3 times with absolute ethanol. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, pour it into a mortar and grind it for 3 min to obtain AgNP S , namely spherical silver nanoparticles.

[0087] Comparative Example 3

[0088] A preparation method of zero-dimensional spherical silver nanoparticles includes the following operating steps:

[0089] (1) Weigh 0.126 g of NaHCO3 and 30 mL of secondary distilled water, prepare a 30 mL 0.05 mol / L NaHCO3 solution, and add 1.7 g of PVP with a molecular weight of 40000 to the 0.05 mol / L NaHCO3 solution to obtain mixture A;

[0090] (2) Add 10 mL of 0.1 mol / L AgNO3 solution to a beaker, place it on a magnetic stirring table, and then add 1.7 g of PVP with a molecular weight of 40000, and stir evenly to obtain mixture B;

[0091] (3) Add mixture B to mixture A and react to obtain an AgCO3 white precipitate solution;

[0092] (4) Pour the AgCO3 white precipitate solution into a 100 mL hydrothermal reaction kettle, and then place it in an oven for reaction. The initial temperature is room temperature, the final temperature is 180 °C, and the reaction lasts for 5 h to obtain a precipitate;

[0093] (5) Filter the precipitate, centrifuge and wash the precipitate 3 times with deionized water, and then centrifuge and wash it 3 times with absolute ethanol. After the absolute ethanol volatilizes, pour the precipitate onto a glass petri dish to dry. After all the liquid has volatilized, scrape off the powder, pour it into a mortar and grind it for 3 min to obtain AgNP S , namely spherical silver nanoparticles.

[0094] Detect the AgNP obtained in the above Examples 1-2 and Comparative Examples 1-3 S The detection results are shown in Figures 1 - 20 .

[0095] From Figures 1 - 2 , Figures 5 - 6 and Figures 13 - 14 andFigures 17 - 18 Among them, by adjusting the addition sequence of PVP, it was found that the addition sequence affects the diameter and morphology of AgNPs.

[0096] From Figures 1 - 2 it can be seen that the average particle size of the silver nanoparticles synthesized in Example 1 is 35.56 nm, and the particle size is uniform. Most of the shapes are spherical or quasi-spherical, and partial agglomeration occurs. Since the surface of the silver nanoparticles generated in Example 1 is covered by a large number of PVP molecules, due to the steric hindrance effect, both the reaction rate is controlled and the aggregation of silver nanoparticles into larger particles due to collision is inhibited, thus preventing most silver nanoparticles from agglomerating.

[0097] From Figures 5 - 6 it can be seen that most of the synthesized silver nanoparticles are spherical, with an average particle size of 23 nm, showing soft agglomeration. Since glucose is added as a reducing agent, its particle size and morphology are better than those of the silver nanoparticles synthesized under the single-polymer PVP system in Example 1; and by adjusting the molecular weight and addition sequence of PVP, the size of the nanomaterials is too small, and the adsorption effect is greater than the repulsion effect. It can be dispersed by applying an external force without affecting subsequent applications in the composite industry.

[0098] In Example 1 and Example 2, spherical silver nanoparticles with an average particle size of less than 40 nm were synthesized by adjusting the addition sequence of PVP. The morphology of the AgNPs synthesized by adding PVP before the formation of Ag2CO3 is more spherical than that of the AgNPs synthesized by adding PVP after the formation of Ag2CO3, and the diameter can be reduced by at least 50%; in Example 1 and Example 2, the particles generated by adjusting the molecular weight of PVP have high stability, greatly reducing the agglomeration phenomenon of AgNPs, and the particle size distribution is uniform.

[0099] From Figures 13 - 14 it can be seen that the average particle size of the silver nanoparticles synthesized in Comparative Example 2 is 75.64 nm, most of the shapes are polygonal, and some are ellipsoidal or quasi-spherical, showing an agglomeration phenomenon. This is because for the AgNPs synthesized by adding PVP after the formation of Ag2CO3, the microscopic distribution of PVP is uneven, and some crystal planes of the silver crystal nuclei are not completely coated by PVP during the hydrothermal reaction process, resulting in the agglomeration and irregular morphology of the silver nanoparticles.

[0100] From Figures 17 - 18It can be seen that the average particle size of the silver nanoparticles synthesized in Comparative Example 3 is 45.46 nm. The silver nanoparticles with smaller particle sizes are mostly spherical or quasi-spherical in shape, while those with larger particle sizes are mostly polygonal in shape, showing an agglomeration phenomenon. The appearance of polygonal silver nanoparticles is due to the uneven distribution of PVP at the microscopic level. During the hydrothermal reaction process, some crystal planes of the silver crystal nuclei are not completely coated by PVP, resulting in the fact that when the silver crystal nuclei grow into silver nanoparticles, some crystal planes with faster growth rates are not inhibited, and finally the phenomena of agglomeration and irregular morphology occur.

[0101] From Figures 9 - 10 and Figures 13 - 14 it can be seen that there is a positive correlation between the molecular weight of PVP and its degree of polymerization. From Figures 9 - 10 it can be seen that the silver nanoparticles synthesized in Comparative Example 1 are highly agglomerated, but spherical or quasi-spherical silver nanoparticles with dispersibility cannot be generated. This is because the molecular weight of PVP is 10,000, and the molecular chain of PVP is too short to completely coat the surface of the silver crystal nuclei. The exposed silver crystal planes have higher energy and will attract the seeds to agglomerate. After the concentration of silver particles is relatively high at a certain position in the solution, the reaction rate is accelerated, resulting in heterogeneous nucleation in the reaction system and obtaining a large number of silver nuclei. From Figures 13 - 14 it can be seen that the silver nanoparticles synthesized in Comparative Example 2 are uniformly spherical or quasi-spherical in shape. This is because the molecular weight of PVP is 40,000, and the high-concentration long molecular chain of PVP coats the surface of the silver crystal nuclei, making the growth rate of each crystal plane nearly equal, and finally obtaining quasi-spherical silver nanoparticles.

[0102] The function of the EDS diagram is to preliminarily judge the elemental silver nanoparticles and the Ag nanoparticles in the synthesized substance, while the function of the XRD diagram is to determine each crystal phase by analyzing the diffraction peaks of the synthesized substance and analyze that the obtained substance is Ag. From Figures 3 - 4 、 Figures 7 - 8 、 Figures 11 - 12 、 Figures 15 - 16 and Figures 19 - 20 it is known that the present invention can decompose Ag2CO3 by hydrothermal method to generate elemental silver. The XRD diagram can also evaluate the crystallinity of the material by analyzing the intensity and width of the diffraction peaks, and analyze and judge the crystal quality and purity. From Figure 4 、 Figure 8 、 Figure 12 and Figure 16 and Figure 20 it can be seen that the positions of the 5 characteristic peaks of silver nanoparticles in the X-ray diffraction diagram of silver nanoparticles are consistent with the data of the standard PDF card 04-0783, corresponding to the (111), (200), (220), (311), and (222) crystal planes of cubic silver respectively. Once again, it is confirmed that the sample of the present invention is elemental silver of cubic crystal system, and the diffraction peaks of this curve are quite sharp, indicating that the sample has good crystallization performance.

[0103] In the present invention, by regulating the molecular weight of PVP and the addition sequence, it is found that both have a significant impact on the morphology of AgNPs. High-molecular-weight PVP as a surface additive can synthesize spherical silver nanoparticles and solve the serious agglomeration problem of silver nanoparticles synthesized using low-molecular-weight PVP as a surface additive; the AgNPs synthesized by adding PVP before the formation of Ag2CO3 are more spherical than those synthesized by adding PVP after the formation of Ag2CO3, and the diameter can be reduced by at least 50%, greatly reducing the agglomeration phenomenon of AgNPs. In addition, by exploring the addition of glucose as a reducing agent, the particle size and morphology are better than those of silver nanoparticles synthesized in a single high-molecular PVP system.

[0104] The above are only the preferred embodiments of the present invention and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing zero-dimensional spherical nanosilver, characterized in that: The steps are as follows: (1) Weigh a certain amount of NaHCO3 and water to prepare a 0.05 mol / L NaHCO3 solution; (2) Add 0.1 mol / L AgNO3 solution into a beaker and then add PVP, stir evenly to obtain mixture A; (3) Adding mixture A into 0.05 mol / L NaHCO3 solution, the reaction yields a white AgCO3 precipitate solution; (4) pouring the AgCO3 white precipitate solution into a hydrothermal reactor, and then placing it in an oven for reaction to obtain a mixture B; (5) Filter the mixture B, wash the precipitate with water by centrifugation, and then wash it with anhydrous ethanol by centrifugation. After the anhydrous ethanol evaporates, grind it to obtain AgNPs S , that is, spherical nanosilver.

2. The method for preparing zero-dimensional spherical nanosilver according to claim 1, characterized in that: The steps are as follows: (1) Weigh 0.126 g NaHCO3 and 30 mL deionized water to prepare 30 mL of 0.05 mol / L NaHCO3 solution; (2) Add 10 mL of 0.1 mol / L AgNO3 solution into a beaker and place it on a magnetic stirring table, then add 1.7 g of PVP and stir evenly to obtain a mixture; (3) adding the mixture into 0.05 mol / L NaHCO3 solution to obtain a white precipitate solution of AgCO3; (4) Pour the AgCO3 white precipitate solution into a 100 mL hydrothermal reactor, and then place it in an oven for reaction, wherein the initial temperature is room temperature, the final temperature is 180°C, and the reaction is performed for 5 h to obtain a precipitate; (5) The precipitate was filtered, washed three times with deionized water, and then washed three times with anhydrous ethanol. After the anhydrous ethanol evaporated, the precipitate was poured onto a glass petri dish to dry. After the liquid evaporated completely, the powder was scraped off and then poured into a mortar and ground for 3 min to obtain AgNPs. S , that is, spherical nanosilver.

3. The method for preparing zero-dimensional spherical nanosilver according to claim 2, characterized in that: The deionized water is double distilled water.

4. The method for preparing zero-dimensional spherical nanosilver according to claim 1, characterized in that: The molecular weight of the PVP is 40,000.

5. The method for preparing zero-dimensional spherical nanosilver according to claim 1, characterized in that: The PVP is a PVA with a molecular weight of 10,000 and a molecular weight of 40,000 in a mass ratio of 1:

1.

6. The method for preparing zero-dimensional spherical nanosilver according to claim 2, characterized in that: In the step (2), 10 mL of 0.1 mol / L AgNO3 solution was added into a beaker and placed on a magnetic stirring table, 0.360 g of glucose was added into the solution and stirred evenly, and then 1.7 g of PVP was added and stirred evenly to obtain a mixture.

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