A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode

Abstract

The present invention discloses a method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode, belonging to the field of electrochemistry technology. This method uses silver wires as raw materials and obtains high-purity silver nanoparticles through electrochemical oxidation etching, reduction, and ultrasonic treatment. In addition, the batch production of silver nanoparticles can be achieved by the parallel connection and repeated use of several silver wires. The method for preparing silver nanoparticles in the present invention has the advantages of simplicity, rapidity, low cost, and easy large-scale production. Therefore, the high-purity silver nanoparticles prepared by this electrochemical method have broad application prospects in the fields of medicine, new energy, and catalysis, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemistry, and particularly relates to a method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode. Background Art

[0002] In recent years, due to the physicochemical properties of metals and metal oxides being conducive to industrial production and application, the attention has gradually shifted to nanoparticles of metals or metal oxides. Nanoscale elemental silver particles, due to their unique physicochemical properties, have broad application prospects in many fields such as medicine, catalysis, the electronics industry, and water treatment, and have become one of the nanomaterials that have received wide attention.

[0003] The preparation methods of silver nanoparticles mainly include physical methods, chemical methods, and biological methods. Among them, the physical method has a simple operation process and few impurities in the product, but the product is prone to agglomeration, the equipment technical requirements are high, the production cost is high, and large-scale production cannot be carried out. The chemical method is widely used, but the organic solvents in the chemical method are harmful to the human body and will also pollute the environment. The preparation of silver nanoparticles by the microbial reduction method is relatively environmentally friendly, but it is necessary to continuously search for bacterial strains with strong silver ion reduction ability, and at the same time, it is necessary to solve the problem of the purity of silver nanoparticles caused by the introduction of microbial cells.

[0004] The emerging method of electrochemically synthesizing silver nanoparticles using different complexing agents has the advantages of being fast and pollution-free, but the raw materials (such as silver nitrate reagents, etc.) used in this method are very expensive, and this method has not been applied in the large-scale synthesis of nanomaterials, and the output problem still needs to be further solved. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode, which can effectively solve the technical problems of low production yield, low purity, high raw material cost, and thus inability to industrialize and mass-produce silver nanoparticles in the prior art.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions to be realized:

[0007] A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode disclosed by the present invention includes the following steps:

[0008] 1) Take two identical silver wires and label them as silver wire A and silver wire B. Use silver wire A as the A electrode and silver wire B as the B electrode to form a two-electrode system. Add an electrolyte solution, and under stirring conditions, apply an oxidation voltage to generate a black film on the surface of silver wire A as the main component of the silver-based oxide electrode; continue to apply a reduction voltage, and the silver-based oxide generated on the surface of silver wire A is reduced to prepare silver nanoparticles. At this time, silver wire B is oxidized to silver-based oxide;

[0009] 2) Remove the silver wire A processed in step 1) and place it in the electrolyte for ultrasonic treatment. After washing, filtering, and drying, pure silver nanoparticles are obtained.

[0010] 3) Clamp the silver wire A from which the pure silver nanoparticles have been removed in step 2) onto the electrode clamp, add the electrolyte, and apply an oxidation voltage under stirring conditions to form a black film on the surface of the silver wire A as the main component of the silver-based oxide electrode. At this time, the silver-based oxide on the silver wire B is reduced to obtain silver nanoparticles.

[0011] 4) Remove the silver wire B processed in step 3) and place it in the electrolyte for ultrasonic treatment. After washing, filtering, and drying, pure silver nanoparticles are obtained.

[0012] 5) Collect the prepared pure silver nanoparticles.

[0013] Preferably, repeat the operation steps 1) to 4) several times to complete the batch preparation of silver nanoparticles.

[0014] Further preferably, the number of repetitions is determined by the diameter of the silver wire.

[0015] Preferably, take several silver wires A and several silver wires B with the same quantity respectively. Several silver wires A are connected in parallel as the A electrode, and several silver wires B are connected in parallel as the B electrode.

[0016] Preferably, the electrolyte is a potassium bicarbonate solution saturated with carbon dioxide.

[0017] Further preferably, the concentration of the potassium bicarbonate solution is 0.1 mol / L.

[0018] Preferably, in step 1), the applied oxidation voltage is 9V, and the treatment time is 3 - 13 minutes; the applied reduction voltage is -9V, and the treatment time is 3 - 13 minutes.

[0019] Preferably, in step 3), the applied oxidation voltage is 9V, and the treatment time is 3 - 13 minutes; the applied reduction voltage is -9V, and the treatment time is 3 - 13 minutes.

[0020] Preferably, the washing in step 2) and step 4) is carried out by washing with pure water and ethanol in sequence.

[0021] Further preferably, the prepared silver nanoparticles have a closely arranged porous rod-like structure.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The preparation method of silver nanoparticles based on the alternating transformation of electrochemical anode and cathode disclosed by the present invention uses silver wires as raw materials. Through electrochemical oxidation and reduction, silver nanoparticles attached to the silver wires and dispersed in the electrolyte are obtained. After ultrasonic treatment and washing, pure silver nanoparticles are obtained. The prepared silver nanoparticles have a polyhedral rod-like structure with close arrangement, and the preparation method is rapid and simple. Based on the above advantages, the preparation method of the silver nanoparticles has good industrial application prospects.

[0024] Furthermore, after washing, the same silver wire can be reused, and the prepared silver nanoparticles have the same polyhedral rod-like structure.

[0025] Furthermore, the parallel batch preparation of silver nanoparticles can be realized through the parallel connection and repeated use of several silver wires. Description of the Drawings

[0026] Figure 1 It is the preparation flow chart provided by Embodiment 1 of the present invention.

[0027] Figure 2 It is the X-ray diffraction (XRD) spectrum of silver nanoparticles, silver-based oxide (silver carbonate), and silver wire (raw material) provided by Embodiment 1 of the present invention. The abscissa is the diffraction angle 2θ, with the unit of degree; the ordinate is the diffraction intensity, with the unit of relative intensity.

[0028] Figure 3 It is the scanning electron microscope (SEM) image of the raw material silver wire A and the silver-based oxide electrode B provided by Embodiment 1 of the present invention; among them, a is the raw material silver wire; b is the cathode oxide electrode B.

[0029] Figure 4 It is the photo and scanning electron microscope (SEM) image of the silver nanoparticles prepared after reduction in Embodiment 1 of the present invention; among them, a is the photo of the silver nanoparticles; b is the SEM image of the silver nanoparticles.

[0030] Figure 5 It is the graph of current changing with time provided by Embodiment 1 of the present invention.

[0031] Figure 6 It is the industrial application model diagram for the batch preparation of silver nanoparticles provided by the present invention. Detailed Embodiments

[0032] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0034] The present invention will be further described in detail below with reference to the drawings:

[0035] The present invention provides silver nanoparticles prepared by a two-electrode electrochemical oxidation-reduction method, which are fast, low-cost and simple and suitable for large-scale preparation. The silver nanoparticles use silver wires as raw materials and are prepared by a two-step method. After ultrasonic treatment and washing, high-purity silver nanoparticles are obtained.

[0036] The specific preparation steps and applications are as follows:

[0037] A two-electrode electrolytic cell is used, with a KHCO 3 solution as the electrolyte, and two identical silver wires are used as the A electrode and the B electrode respectively. The magnetic stirrer is turned on, and an oxidation voltage is applied. At this time, the following reactions occur on the surface of the A electrode:

[0038] (1) The specific preparation steps are as follows:

[0039] Ag–e - = Ag +

[0040] 2Ag + + CO 3 2- = Ag 2 CO 3

[0041] Ag + + HCO 3 - = AgHCO 3

[0042] 2AgHCO 3 = Ag 2 CO 3 + H 2 O + CO 2

[0043] After a period of time, it can be observed that a black film is formed on the surface of the silver wire A, which is the main component of the above-mentioned silver-based oxide electrode A. In the embodiment of the present invention, the prepared silver-based oxide is particles with a smooth surface, short microporous polyhedral rod-like structure, and the composition is silver carbonate (Ag 2 CO 3 ).

[0044] (2) Using the KHCO 3 solution as the electrolyte, turn on the magnetic stirrer and apply a reduction voltage. The electrode A is reduced to obtain silver nanoparticles. At this time, a black film is formed on the surface of the silver wire of electrode B as the main component of the silver-based oxide;

[0045] (3) Take down the A electrode after step 2 and place it in the electrolyte for ultrasonic treatment. Wash, filter with pure water and ethanol respectively, and dry to obtain pure silver nanoparticles.

[0046] (4) Using the silver wire A after ultrasonic treatment in step 3 as electrode A, adopt a two-electrode electrolytic cell, use the KHCO 3 solution as the electrolyte, turn on the magnetic stirrer and apply an oxidation voltage. The silver-based oxide of electrode B is reduced to obtain silver nanoparticles. At this time, a black film is formed on the surface of the silver wire of electrode A as the main component of the silver-based oxide;

[0047] (5) Take down the B electrode after step 4 and place it in the electrolyte for ultrasonic treatment. Wash, filter with pure water and ethanol respectively, and dry to obtain pure silver nanoparticles.

[0048] (6) Repeat steps 1 to 5 to mass-produce silver nanoparticles.

[0049] In the embodiment of the present invention, the prepared silver nanoparticles exhibit a dense and interlaced microporous network structure on the surface of the original silver-based oxide electrode.

[0050] Figure 1 is the preparation flow chart provided by the present invention, and the preparation of silver nanoparticles is completed through simple steps such as oxidation, reduction and ultrasonic treatment and a small amount of chemical reagents.

[0051] Figure 6 is the industrial application model diagram for batch preparation of silver nanoparticles provided by the present invention. As can be seen from the figure, multiple groups of silver wires can be connected in parallel simultaneously for high-yield batch production during large-scale application.

[0052] Example 1

[0053] (1) Cut the silver wire cleaned with ethanol into two pieces of the same length as electrode A and electrode B, and add 0.1M KHCO saturated with carbon dioxide 3The solution is an electrolyte. An anion exchange membrane is used to form a two - electrode system. The magnetic stirrer is turned on, and a certain positive voltage (9V) is applied to this two - electrode system for 13 minutes. After completion, a black film is formed on the surface of the silver wire of electrode A, which is the main component of the silver - based oxide electrode described in the present invention.

[0054] (2) In step 1, all devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 13 minutes. After completion, the silver - based oxide prepared on the surface of electrode silver wire A in step 1 is reduced to silver nanoparticles, which are the silver nanoparticles described in the present invention. Their microscopic morphology is as Figure 4 shown. A black film is formed on the surface of the silver wire of electrode B, which is the main component of the silver - based oxide described in the present invention.

[0055] (3) The electrode silver wire A after step 2 is taken down and ultrasonicated in the electrolyte after oxidation - reduction of electrode A, washed and filtered with pure water and ethanol respectively, and dried to obtain pure silver nanoparticles.

[0056] Figure 2 is the X - ray diffraction (XRD) pattern of the silver nanoparticles, silver - based oxide, and silver wire provided by the present invention. As can be seen from the figure, some silver compounds are formed on the silver wire through the first - step electrochemical reaction. In the second - step electrochemical reaction, these silver compounds are completely reduced to metallic silver, which are the nanoparticles described in the present invention.

[0057] Figure 3 is the scanning electron microscope (SEM) image of the raw material silver wire A and the silver - based oxide electrode B provided by the present invention. As can be seen from the figure, the silver - based oxide electrode is a particle with a smooth - surface, short - microporous polyhedral rod - like structure.

[0058] Figure 4 is the scanning electron microscope (SEM) image of the prepared silver nanoparticles A after reduction provided by the present invention. As can be seen from the figure, the silver nanoparticles present a dense and interlaced microporous network morphology composed of polyhedral rod - like structures on the surface of the original silver - based oxide electrode.

[0059] See Figure 5 , which is the current - time change diagram provided by the present invention. As can be seen from the figure, the curves do not reach stability at 3 minutes and 8 minutes of reduction. As the time progresses to 13 minutes, the curve tends to be flat, indicating that the reduction reaches a stable state. The yield of silver nanoparticles reaches an ideal value at this time.

[0060] Comparative Example 1

[0061] (1) The silver wire cleaned with ethanol is cut into two pieces of the same length as electrode A and electrode B, and 0.1M KHCO saturated with carbon dioxide is used 3The solution is an electrolyte. An anion exchange membrane is used to form a two - electrode system. The magnetic stirrer is turned on, and a certain positive voltage (9V) is applied to this two - electrode system for 3 minutes. After the end, a black film is formed on the surface of the silver wire of electrode A, which is the main component of the silver - based oxide electrode described in the present invention.

[0062] (2) In step 1, all the devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 3 minutes. After the end, a black film is formed on the surface of the silver wire of electrode B, which is the main component of the silver - based oxide described in the present invention. The silver - based oxide formed on the surface of the silver wire of electrode A is reduced, which is the silver nanoparticles described in the present invention.

[0063] (3) The silver wire A of the electrode after step 2 is taken down and ultrasonicated in the electrolyte after the oxidation - reduction of electrode A, washed and filtered with pure water and ethanol respectively, and dried to obtain pure silver nanoparticles.

[0064] Comparative Example 2

[0065] (1) The silver wire cleaned with ethanol is cut into two pieces of the same length as electrode A and electrode B, and 0.1M KHCO saturated with carbon dioxide 3 The solution is an electrolyte. An anion exchange membrane is used to form a two - electrode system. The magnetic stirrer is turned on, and a certain positive voltage (9V) is applied to this two - electrode system for 8 minutes. After the end, a black film is formed on the surface of the silver wire of electrode A. This is the main component of the silver - based oxide electrode described in the present invention.

[0066] (2) In step 1, all the devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 8 minutes. After the end, a black film is formed on the surface of the silver wire of electrode B, which is the main component of the silver - based oxide described in the present invention. The silver - based oxide formed on the surface of the silver wire of electrode A is reduced, which is the silver nanoparticles described in the present invention.

[0067] (3) The silver wire A of the electrode after step 2 is taken down and ultrasonicated in the electrolyte after the oxidation - reduction of electrode A, washed and filtered with pure water and ethanol respectively, and dried to obtain pure silver nanoparticles.

[0068] Compared with the 13 - minute electrochemical treatment in Example 1, the silver nanoparticles prepared in Comparative Example 1 and Comparative Example 2 with relatively short electrochemical treatment are significantly reduced, indicating that sufficient electrochemical treatment time is required to increase the yield of silver nanoparticles.

[0069] Example 2

[0070] (1) The silver wire cleaned with ethanol is cut into two pieces of the same length as electrode A and electrode B, and 0.1M KHCO saturated with carbon dioxide 3The solution is an electrolyte. An anion exchange membrane is used to form a two - electrode system. The magnetic stirrer is turned on, and a certain positive voltage (9V) is applied to this two - electrode system for 13 minutes. After the end, a black film is formed on the surface of the silver wire of electrode A, which is the main component of the silver - based oxide electrode described in the present invention.

[0071] (2) In step (1), all the devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 13 minutes. After the end, the silver - based oxide prepared on the surface of electrode silver wire A in step (1) is reduced to silver nanoparticles, which are the silver nanoparticles described in the present invention. Their microscopic morphology is as Figure 4 shown. A black film is formed on the surface of the silver wire of electrode B, which is the main component of the silver - based oxide described in the present invention.

[0072] (3) The electrode silver wire A after the end of step (2) is taken down and ultrasonicated in the electrolyte after the oxidation - reduction of electrode A, washed and filtered with pure water and ethanol respectively, and dried to obtain pure silver nanoparticles.

[0073] (4) The silver wire A ultrasonically cleaned in step (3) is fixed on the electrode clamp, the electrolyte is added, the magnetic stirrer is turned on, and an oxidation (9V) voltage is applied. A black film is formed on the surface of silver wire A as the main component of the silver - based oxide electrode; the silver - based oxide on electrode B is reduced to obtain silver nanoparticles.

[0074] (5) The electrode silver wire B after the end of step (4) is taken down and ultrasonicated in the electrolyte used for the oxidation - reduction of electrode B, washed and filtered with pure water and ethanol respectively, and dried to obtain pure silver nanoparticles.

[0075] (6) Steps (1) - (5) are continued to be repeated twice to obtain the data shown in Table 1 below:

[0076] Table 1

[0077] Initial mass / g Yield 1 / g Yield 1 Yield 2 / g Yield 2 Yield 3 / g Yield 3 Total yield Electrode A 0.1100 0.0144 13.00％ 0.0207 18.80％ 0.0133 12.00％ 43.80％ Electrode B 0.1121 0.0109 9.70％ 0.0202 18.00％ 0.0164 14.60％ 42.30％

[0078] It can be seen that the total yield of silver nanoparticles increases in multiples according to the number of experimental repetitions. It is expected that the yield will continue to increase to more than 80% if the preparation continues. This shows that the present invention can mass - produce silver nanoparticles. (Yield = output / starting mass * 100%)

[0079] Example 3

[0080] (1) The silver wire cleaned with ethanol is cut into two pieces of the same length as electrode A and electrode B, and 0.1M KHCO saturated with carbon dioxide is used 3The solution is an electrolyte. An anion exchange membrane is used to form a two - electrode system. Without using a magnetic stirrer, a certain positive voltage (9V) is applied to this two - electrode system for 13 minutes. After the end, a yellow - green film is formed on the surface of the silver wire of electrode A. At the same time, a small amount of particles that are not attached to the silver wire are deposited at the bottom of the electrolytic cell.

[0081] (2) In step 1, all devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 13 minutes. After the end, the silver - based oxide prepared on the surface of electrode silver wire A in step 1 is reduced to nano - silver. A yellow - green film is formed on the surface of the silver wire of electrode B.

[0082] (3) The electrode silver wire A after step 2 is taken down and ultrasonicated in the electrolyte after the oxidation - reduction of electrode A, washed and filtered with pure water and ethanol respectively. The dried silver nanoparticles are tested by XRD. The results show that silver carbonate impurities are contained, indicating that it is difficult to reduce all the silver carbonate that has fallen into the electrolyte without stirring.

[0083] (4) To verify the properties of the yellow - green oxide film, XRD is used to test the substance formed on the surface of the silver wire of electrode B. The obtained spectrogram is consistent with that of silver carbonate in Example 1. It is speculated that the color of silver carbonate depends on its microstructure and light sensitivity.

[0084] Example 4

[0085] (1) The silver wire cleaned with ethanol is cut into two pieces of the same length to serve as electrode A and electrode B. Using 0.3M KHCO saturated with carbon dioxide 3 as the electrolyte, an anion exchange membrane is used to form a two - electrode system. The magnetic stirrer is turned on, and a certain positive voltage (9V) is applied to this two - electrode system for 13 minutes. After the end, a black film is formed on the surface of the silver wire of electrode A. This is the main component of the silver - based oxide electrode described in the present invention.

[0086] (2) In step 1, all devices and materials remain unchanged. Only a certain negative voltage (-9V) is applied to this two - electrode system for 13 minutes. After the end, a black film is formed on the surface of the silver wire of electrode B, and the silver - based oxide prepared on the surface of electrode silver wire A in step 1 is reduced to nano - silver.

[0087] (3) Comparing with electrode A after oxidation - reduction using 0.1M KHCO 3 as the electrolyte in Example 1, the silver nanoparticles attached to electrode A after reduction in this example are significantly reduced, indicating that the electrolyte concentration is an important factor determining the yield of silver nanoparticles.

[0088] Example 5

[0089] (1) Cut the silver wire cleaned with ethanol into two pieces of the same length as the A electrode and the B electrode, and apply 0.1MK 2 SO 4 solution as the electrolyte, use an anion exchange membrane to form a two-electrode system, turn on the magnetic stirrer, apply a certain positive voltage (9V) to the two-electrode system for 13 minutes. After the end, a black film is formed on the surface of the silver wire of the A electrode. This is the main component of the silver-based oxide electrode described in the present invention.

[0090] (2) Without changing all the devices and materials in step 1, only apply a certain negative voltage (-9V) to the two-electrode system for 13 minutes. After the end, a black film is formed on the surface of the silver wire of the B electrode, and the silver-based oxide prepared on the surface of the electrode silver wire A in step 1 is reduced to nano-silver.

[0091] (3) In Comparative Example 1, 0.1M KHCO 3 was used as the electrolyte for the oxidized and reduced electrode A. After the reduction of the electrode A in this example, the attached silver nanoparticles were significantly reduced, indicating that the type of electrolyte is an important factor determining the yield of silver nanoparticles.

[0092] The above examples and comparative examples show that sufficient electrochemical treatment time, repeated use of silver wire, use of a magnetic stirrer, and selection of appropriate electrolyte type and concentration are necessary conditions to ensure high yield of silver nanoparticles.

[0093] In summary, high-purity silver nanoparticles are obtained through electrochemical oxidation etching, reduction, and ultrasonic treatment. The preparation method of the silver nanoparticles is fast, simple, and low-cost. In addition, the preparation process of the silver nanoparticles can achieve low-cost large-scale preparation of high-purity silver nanoparticles through parallel connection of several silver wires and repeated use of silver wires. Based on the above advantages, the preparation method of the silver nanoparticles has good industrial application prospects and is suitable for large-scale applications in the fields of medicine, new energy, catalysis, etc.

[0094] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode, characterized in that, it includes the following steps: 1) Take two identical silver wires marked as silver wire A and silver wire B. Use silver wire A as electrode A and silver wire B as electrode B. Or, take the same number of silver wires A and silver wires B respectively. A number of silver wires A are connected in parallel as electrode A, and a number of silver wires B are connected in parallel as electrode B; Separate electrode A and electrode B with an anion exchange membrane to form a two-electrode system. Add the electrolyte. Under stirring conditions, apply an oxidation voltage to generate a black film on the surface of silver wire A as the main component of the silver-based oxide electrode. Continue to apply a reduction voltage, and the silver-based oxide generated on the surface of silver wire A is reduced to obtain silver nanoparticles. At this time, silver wire B is oxidized to silver-based oxide; 2) Remove silver wire A processed in step 1) and place it in the electrolyte for ultrasonic treatment. After washing, filtering, and drying, pure silver nanoparticles are obtained; 3) Clamp silver wire A from which the pure silver nanoparticles are removed in step 2) on the electrode clamp. Add the electrolyte. Under stirring conditions, apply an oxidation voltage to generate a black film on the surface of silver wire A as the main component of the silver-based oxide electrode. At this time, the silver-based oxide on silver wire B is reduced to obtain silver nanoparticles; 4) Remove silver wire B processed in step 3) and place it in the electrolyte for ultrasonic treatment. After washing, filtering, and drying, pure silver nanoparticles are obtained; 5) Repeat operation steps 1) to 4) several times to complete the batch preparation of silver nanoparticles, and collect the obtained pure silver nanoparticles; The electrolyte is a potassium bicarbonate solution saturated with carbon dioxide.

2. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to claim 1, characterized in that, the number of repetitions is determined by the diameter of the silver wire.

3. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to claim 1, characterized in that, the concentration of the potassium bicarbonate solution is 0.1 mol / L.

4. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to claim 1, characterized in that, in step 1), the applied oxidation voltage is 9 V, and the treatment time is 3 to 13 minutes; the applied reduction voltage is -9 V, and the treatment time is 3 to 13 minutes.

5. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to claim 1, characterized in that, in step 3), the applied oxidation voltage is 9 V, and the treatment time is 3 to 13 minutes; the applied reduction voltage is -9 V, and the treatment time is 3 to 13 minutes.

6. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to claim 1, characterized in that, the washing in steps 2) and 4) is carried out by washing with pure water and ethanol in sequence.

7. A method for preparing silver nanoparticles based on the alternating transformation of the cathode and anode according to any one of claims 1 to 6, characterized in that, the prepared silver nanoparticles have a closely arranged porous rod-like structure.

Images