A method for preparing silver nanowires

Abstract

This invention proposes a method for preparing silver nanowires, belonging to the field of nanomaterials technology. The preparation method includes: uniformly mixing a macromolecular surfactant, a solvent, a silver salt, and a catalyst to obtain a first reaction solution; mixing a reducing agent with the solvent to obtain a second reaction solution; injecting the first and second reaction solutions into a reaction vessel at a constant rate under reaction conditions of 30-60℃ and reacting for 8-12 minutes to obtain a product solution; and centrifuging the product solution to obtain silver nanowires. In the preparation process, the growth direction of silver grains is controlled by the macromolecular surfactant, achieving low-temperature and efficient preparation of silver nanowires. The obtained silver nanowires exhibit good stability, uniformity, and high yield, solving the problems of high-temperature reduction and low efficiency associated with silver nanowire preparation.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a method for preparing silver nanowires. Background Technology

[0002] In many areas of future smart technology, such as smart foldable screens, smartphones, smart home appliances, automotive electronics, and flexible light emission, new materials are essential. Compared to similar transparent conductive materials used in flexible wearable technology and flexible phones, silver nanowires are currently the best material in terms of both process and cost. In addition to silver's excellent conductivity, silver nanowires also possess excellent light transmittance and flexibility due to the nanoscale size effect. Therefore, they are considered the most likely material to replace traditional ITO transparent electrodes, providing possibilities for flexible, bendable LED displays and touchscreens, and numerous studies have already applied them to thin-film solar cells. Furthermore, the high aspect ratio of silver nanowires also gives them significant advantages in applications such as conductive adhesives and thermally conductive adhesives.

[0003] Currently, there are many methods for preparing silver nanowires, including the polyol method, template method, electrochemical method, and hydrothermal method.

[0004] In the template method, the formulation of silver nanowires mainly includes porous alumina membranes, carbon nanotubes and block copolymers, silver nanowire ink, etc. Pre-templates are required in the preparation process. By using pre-templates, the morphology of silver nanowires can be controlled. The quality and quantity of the pores in the pre-templates determine the quality and quantity of the obtained nanomaterials. The preparation process is complex and costly.

[0005] In the electrochemical method, the formulation of the silver nanowires mainly consists of nitrates, sodium tetrahydroborate, sodium hydroxide, acetone, etc. During the preparation process, the above components cause problems such as environmental pollution and low preparation efficiency.

[0006] In the polyol method, the formulation of silver nanowires mainly consists of polyol solutions of nitrate and potassium chloride, polyol solutions of high-concentration silver nitrate, and polyvinylpyrrolidone. The silver nanowires formed based on the above components are generally short in length, less than 20 μm, and have low product content. In addition, the preparation process uses a large amount of organic solvents and requires reaction at high temperature.

[0007] In the hydrothermal method, the formulation of silver nanowires mainly includes silver nitrate, polyvinylpyrrolidone, glucose reducing agent, nucleating corrosion inhibitor, and solvent. Among them, the nucleating corrosion inhibitor is selected from alkaline earth metal silicates, alkali metal sulfates, or alkaline earth metal sulfates, alkali metal thiocyanates, etc. The preparation of silver nanowires based on the above formulation requires a long reaction time under high temperature and high pressure. For example, the reaction solution needs to be reacted in a reaction vessel at 120℃-200℃ for 2-20 hours. There are certain safety hazards in the operation method. In addition, the prepared silver nanowires also have problems such as poor stability and uniformity, low solid content and low yield. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method for preparing silver nanowires.

[0009] This invention proposes a method for preparing silver nanowires, the method comprising:

[0010] The macromolecular surfactant, solvent, silver salt and catalyst are mixed evenly to obtain the first reaction solution;

[0011] The reducing agent and solvent are mixed to obtain the second reaction solution;

[0012] The first reaction solution and the second reaction solution are injected into the reaction vessel at a constant rate under the condition of 30-60℃ and reacted for 8-12 minutes to obtain the product solution.

[0013] The product solution was centrifuged to obtain silver nanowires.

[0014] Optionally, the concentration range of the macromolecular surfactant is 0.15–0.75 M;

[0015] The concentration range of the silver salt is 0.1–0.5 M;

[0016] The concentration range of the reducing agent is 0.4–2 M;

[0017] The concentration range of the catalyst is 0.2–1.2 mM;

[0018] The solvent is deionized water.

[0019] Optionally, the macromolecular surfactant is a histamine-acrylamide polymer.

[0020] Optionally, the histamine acrylamide polymer has a relative molecular weight of 5,000-20,000 and a molecular weight distribution of 1.05-1.5.

[0021] Optionally, the histamine-acrylamide polymer is formed using the following method:

[0022] Histamine dihydrochloride, sodium hydroxide, and deionized water were added to a reaction vessel and mixed thoroughly. Then, a mixed solution of acryloyl chloride and carbon dichloride was added dropwise to the reaction vessel. After that, the reaction solution was extracted, freeze-dried, thermally dissolved, filtered, and dried to obtain histamine acrylamide monomer.

[0023] The histamine acrylamide monomer, chain transfer agent, thermal initiator, and deionized water are mixed evenly and subjected to free radical polymerization at a temperature of 70–90°C to obtain histamine acrylamide polymer.

[0024] Furthermore, the chain transfer agent includes at least one of dodecyl mercaptan and octadecyl mercaptan.

[0025] Furthermore, the thermal initiator includes at least one of azobisisobutyronitrile (AIBN) and benzoyl peroxide.

[0026] Optionally, the silver salt includes at least one of silver nitrate, silver fluoride, silver chlorate, silver perchlorate, silver ammonia complex, silver sulfate, and silver acetate.

[0027] Optionally, the reducing agent includes at least one of ascorbic acid, sodium ascorbate, oxalic acid, formaldehyde, acetaldehyde, glyoxal, sodium borohydride, and hydrazine hydrate.

[0028] Optionally, the catalyst includes at least one of sodium chloride, sodium bromide, copper chloride, copper chloride dihydrate, ferric chloride, ferric bromide, and copper bromide.

[0029] Optionally, the constant rate is 0.1-5 L / min.

[0030] Optionally, the centrifugal separation speed is 1000-8000 r / min.

[0031] The silver nanowires prepared by this invention can be applied to any one of solar cells, conductive adhesives, thermally conductive adhesives, and conductive pastes.

[0032] This invention proposes a method for preparing silver nanowires. In the preparation process, the growth direction of silver grains is controlled by a macromolecular surfactant, which enables the low-temperature and high-efficiency preparation of silver nanowires. The obtained silver nanowires have good stability and uniformity, and a high yield, thus solving the problems of high-temperature reduction and low efficiency in silver nanowire preparation. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the method for preparing silver nanowires according to an embodiment of the present invention.

[0034] Figure 2 This is a microscopic morphology diagram of the silver nanowires prepared in Example 1 of the present invention;

[0035] Figure 3 This is a microscopic morphology diagram of the silver nanowires prepared in Example 2 of the present invention;

[0036] Figure 4 This is a microscopic morphology diagram of the silver nanowires prepared in Example 3 of the present invention;

[0037] Figure 5 This is a microscopic morphology diagram of the silver nanowires prepared in Example 3 of the present invention;

[0038] Figure 6 This is a microscopic morphology diagram of the silver particles prepared in Comparative Example 1 of this invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. 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 described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0040] like Figure 1 As shown, one aspect of the present invention provides a method S100 for preparing silver nanowires, comprising steps S110 to S140:

[0041] S110. Mix the macromolecular surfactant, solvent, silver salt and catalyst evenly to obtain the first reaction solution.

[0042] Specifically, in step S110, the silver salt includes at least one of water-soluble silver salts such as silver nitrate, silver fluoride, silver chlorate, silver perchlorate, silver ammonia complex, silver sulfate, and silver acetate. Of course, in some embodiments, the silver salt may also include other types of silver salts besides the water-soluble silver salts listed above. The concentration of the silver salt is preferably 0.1 to 0.5 M. The above-mentioned preferred silver salts and their preferred concentrations can promote the formation of silver wires.

[0043] Further, in step S110, the catalyst includes at least one of halide-containing compounds such as sodium chloride, sodium bromide, copper chloride, copper chloride dihydrate, ferric chloride, ferric bromide, and copper bromide. Of course, in some embodiments, the catalyst may also include other types of halide-containing compounds not listed above. The concentration of the catalyst is preferably 0.2–1.2 mM. The above-mentioned preferred catalyst and its preferred concentration are beneficial for forming uniform silver nanowires.

[0044] Furthermore, in step S110, deionized water is used as the solvent so that the reaction can be carried out at a lower temperature and for a shorter time, and no organic solvent is required, which is environmentally friendly and safer. In addition, this embodiment has a high silver wire preparation efficiency and produces silver wires with better quality and more uniform morphology.

[0045] Furthermore, in step S110, the concentration of the macromolecular surfactant is preferably 0.15–0.75 M, and the macromolecular surfactant is preferably a histamine-acrylamide polymer. Optionally, the histamine-acrylamide polymer has a relative molecular weight of 5000–20000 and a molecular weight distribution of 1.05–1.5. This macromolecular surfactant and its preferred concentration can control the growth direction of silver grains to form uniform silver nanowires, allowing the preparation process of silver nanowires to be carried out under conditions of lower temperature and shorter time, without the need for a high-temperature environment.

[0046] The histamine-acrylamide polymer is formed using the following method:

[0047] 1) Add 1 part by mass of histamine dihydrochloride, 3 parts by mass of sodium hydroxide, and 54 parts by mass of deionized water to the reaction vessel and mix well.

[0048] 2) Next, a mixed solution of 1.2 parts by mass of acryloyl chloride and 6.5 parts by mass of carbon dichloride was slowly added dropwise to the reaction vessel. After the addition was complete, the reaction was carried out at room temperature for 2 hours. Then, the mixture was extracted three times with 3 parts by mass of carbon dichloride, and the upper aqueous phase was retained and freeze-dried. After that, it was dissolved by heat with 18.5 parts by mass of isopropanol, filtered, and the filtrate was removed by rotary evaporation under reduced pressure. The filtrate was then dried under vacuum at room temperature for 48 hours to obtain histamine acrylamide monomer.

[0049] 3) Mix 15-70 parts by weight of histamine acrylamide monomer, 0.5-5 parts by weight of chain transfer agent, 0.5-3 parts by weight of thermal initiator, and 30-85 parts by weight of deionized water evenly, and carry out free radical polymerization reaction by slowly adding the mixture in steps at a temperature of 70-90°C to obtain the macromolecular surfactant histamine acrylamide polymer.

[0050] It should be noted that in the above-mentioned histamine acrylamide polymer formation process, the chain transfer agent includes at least one of dodecyl mercaptan and octadecyl mercaptan. The thermal initiator includes at least one of azobisisobutyronitrile and benzoyl peroxide.

[0051] In this embodiment, the prepared macromolecular surfactant histamine acrylamide polymer is an ionic organic coating that can control the growth direction of silver grains and promote the formation of silver nanowires during the preparation of silver nanowires.

[0052] Furthermore, based on the above-mentioned preferred components and concentrations, in some embodiments, step S110 specifically includes: preparing two identical solvents, adding one solvent to mixing vessel I, then adding 0.15-0.75M of a macromolecular surfactant, mechanically stirring and fully dissolving it, then adding 0.1-0.5M of a silver salt, mechanically stirring and fully dissolving it, then adding 0.2-1.2mM of a catalyst, and stirring until homogeneous to obtain the first reaction solution A. In the above mixing process, by mixing the macromolecular surfactant, silver salt, and catalyst stepwise, the components can be fully contacted, improving the interaction effect.

[0053] In some other embodiments, the solvent, macromolecular surfactant, silver salt, and catalyst in step S110 may not be added in the above order. For example, the solvent, macromolecular surfactant, silver salt, and catalyst can be added together to the mixing tank I and stirred until homogeneous to obtain the first reaction solution A. Those skilled in the art can adjust the order according to process requirements.

[0054] S120. The reducing agent and solvent are mixed to obtain the second reaction solution.

[0055] Specifically, in step S120, the reducing agent can be selected from at least one of ascorbic acid, sodium ascorbate, oxalic acid, formaldehyde, acetaldehyde, glyoxal, sodium borohydride, and hydrazine hydrate. Furthermore, the concentration of the reducing agent is preferably 0.4–2 M. The above-mentioned preferred reducing agent and its preferred concentration are beneficial to the reduction growth of silver, forming uniform silver nanowires.

[0056] Furthermore, based on the above preferred components and preferred concentrations, in some embodiments, step S120 specifically includes: adding another portion of solvent (the solvent in step S120 is the same as the solvent in step S110) to the mixing vessel II, then adding a reducing agent, mechanically stirring and fully dissolving to obtain the second reaction solution B.

[0057] It should be noted that in some embodiments, steps S110 and S120 can be performed in the order described above. In other embodiments, steps S110 and S120 can be performed simultaneously. In still other embodiments, step S120 can be performed first, followed by step S110. Those skilled in the art can adjust the sequence according to process requirements.

[0058] S130. The first reaction solution and the second reaction solution are injected into the reactor at a constant rate under the condition of 30-60℃ and reacted for 8-12 minutes to obtain the product solution.

[0059] Specifically, the first reaction solution A obtained in step S110 and the second reaction solution B obtained in step S120 are injected into a constant temperature reactor at a rate of 0.1-5 L / min using a peristaltic pump. The reaction temperature is 30-60℃, and the reaction is stirred for 8-12 min to obtain a product solution. In some embodiments, the product solution is a silver-gray solution.

[0060] S140. Centrifuge the product solution to obtain silver nanowires.

[0061] Specifically, take one part of the product solution obtained in step S130 and add one part of anhydrous ethanol. Centrifuge at a centrifugation rate of 1000-8000 r / min for 15 min. Then, drain the solution, add another part of anhydrous ethanol, and sonicate for 30 s. Then, continue to centrifuge at a centrifugation rate of 1000-8000 r / min for 15 min. Finally, drain the solution to obtain pure silver nanowires.

[0062] It should be understood that, in order to suppress the aggregation of the obtained silver nanowires, the obtained pure silver nanowires can be dispersed in an ethanol solution or an isopropanol solution.

[0063] In the preparation method of the present invention, the macromolecular surfactant can control the growth direction of silver crystals, effectively promote the formation of silver nanowires, and reduce the reaction temperature, so that the preparation process can be carried out at a low reaction temperature (e.g., 30-60°C), and the reaction time is shortened to only 8-12 minutes, thus improving the reaction efficiency. Secondly, in the preparation method provided by the present invention, deionized water is used as the solvent, and no organic reagents are used. The preparation process is safe, reliable, and environmentally friendly, and the prepared silver nanowires have a high yield.

[0064] The silver nanowires obtained based on this invention can be used in solar cells, conductive adhesives, thermal adhesives, conductive pastes, etc., and can also be used to replace traditional ITO transparent electrode materials.

[0065] The preparation method of silver nanowires will be further illustrated below with reference to several specific embodiments:

[0066] Example 1

[0067] The preparation method of the silver nanowires in this embodiment includes the following specific steps:

[0068] S1. Add 2L of deionized water to the mixing vessel I, then add 0.35M histamine acrylamide polymer with a molecular weight of 18200 and a molecular weight distribution of 1.1. After mechanical stirring and complete dissolution, add 0.23M silver nitrate, mechanically stir and complete dissolution, then add 0.4mM copper chloride. After stirring evenly, the first reaction solution A is obtained.

[0069] S2. Add 2L of deionized water to solution preparation vessel II, then add 1.15M ascorbic acid, stir mechanically and dissolve completely to obtain the second reaction solution B.

[0070] S3. Using a peristaltic pump, the first reaction solution A and the second reaction solution B are simultaneously injected into the constant temperature reactor at a rate of 0.5 L / min. The reaction temperature is 45℃, and the mixture is stirred for 10 min to obtain a silver-gray solution, which is the product solution.

[0071] S4. Add 4L of anhydrous ethanol to the silvery-gray solution obtained in step S3 above, centrifuge at 2500r / min for 15min, then discard the supernatant. Add another 2L of anhydrous ethanol and sonicate for 30s. Then centrifuge at 3000r / min for another 15min. Discard the supernatant to obtain pure silver nanowires. The microstructure of the silver nanowires is as follows: Figure 2 As shown.

[0072] Example 2

[0073] The preparation method of the silver nanowires in this embodiment includes the following specific steps:

[0074] S1. Add 1L of deionized water to the mixing vessel I, then add 0.2M histamine acrylamide polymer with a molecular weight of 15600 and a molecular weight distribution of 1.2. After mechanical stirring and complete dissolution, add 0.13M silver nitrate, mechanically stir and complete dissolution, then add 0.25mM copper chloride. After stirring evenly, the first reaction solution A is obtained.

[0075] S2. Add 2L of deionized water to solution preparation vessel II, then add 0.78M ascorbic acid, stir mechanically and dissolve completely to obtain the second reaction solution B.

[0076] S3. Using a peristaltic pump, the first reaction solution A and the second reaction solution B are simultaneously injected into the constant temperature reactor at a rate of 0.3 L / min. The reaction temperature is 30℃. The mixture is stirred for 10 min to obtain a silver-gray solution, which is the product solution.

[0077] S4. Add 2L of anhydrous ethanol to the silvery-gray solution obtained in step S3 above, centrifuge at 2500r / min for 15min, then discard the supernatant, add another 2L of anhydrous ethanol, sonicate for 30s, and then centrifuge at 3000r / min for another 15min. Discard the supernatant to obtain pure silver nanowires. The microstructure of the silver nanowires is as follows: Figure 3 As shown.

[0078] Example 3

[0079] The preparation method of the silver nanowires in this embodiment includes the following specific steps:

[0080] S1. Add 2L of deionized water to the mixing vessel I, then add 0.65M histamine acrylamide polymer with a molecular weight of 8500 and a molecular weight distribution of 1.4. After mechanical stirring and complete dissolution, add 0.5M silver nitrate, mechanically stir and complete dissolution, then add 1.2mM copper chloride. After stirring evenly, the first reaction solution A is obtained.

[0081] S2. Add 2L of deionized water to solution preparation vessel II, then add 2M ascorbic acid, stir mechanically and dissolve completely to obtain the second reaction solution B.

[0082] S3. Using a peristaltic pump, the first reaction solution A and the second reaction solution B are simultaneously injected into the constant temperature reactor at a rate of 0.5 L / min. The reaction temperature is 60℃, and the mixture is stirred for 10 min to obtain a silver-gray solution, which is the product solution.

[0083] S4. Add 4L of anhydrous ethanol to the silvery-gray solution obtained in step S3 above, centrifuge at 2500r / min for 15min, then discard the supernatant. Add another 2L of anhydrous ethanol and sonicate for 30s. Then centrifuge at 3000r / min for another 15min. Discard the supernatant to obtain pure silver nanowires. The microstructure of the silver nanowires is as follows: Figure 4 and Figure 5 As shown.

[0084] Comparative Example 1

[0085] The preparation method of the comparative example silver nanowires includes the following specific steps:

[0086] S1. Add 2L of deionized water to the mixing vessel I, then add 0.35M vinylpyrrolidone polymer (molecular weight 58000), stir mechanically until fully dissolved, then add 0.23M silver nitrate, stir mechanically until fully dissolved, then add 0.4mM copper chloride, stir evenly to obtain the first reaction solution A.

[0087] S2. Add 2L of deionized water to solution preparation vessel II, then add 1.15M ascorbic acid, stir mechanically and dissolve completely to obtain the second reaction solution B.

[0088] S3. Using a peristaltic pump, the first reaction solution A and the second reaction solution B are simultaneously injected into the constant temperature reactor at a rate of 0.5 L / min. The reaction temperature is 45℃. The mixture is stirred for 10 min to obtain a light yellow solution, which is the product solution.

[0089] S4. Add 4L of anhydrous ethanol to the yellowish-brown solution obtained in step S3 above, centrifuge at 2500r / min for 15min, then discard the supernatant. Add another 2L of anhydrous ethanol and sonicate for 30s. Then centrifuge at 3000r / min for another 15min. Discard the supernatant to obtain pure, irregular silver particles. The microstructure of these silver particles is as follows: Figure 6 As shown.

[0090] In summary, based on the results of Comparative Example 1 and Example 1, it can be seen that in Comparative Example 1, when the macromolecular surfactant histamine acrylamide polymer was replaced with vinylpyrrolidone polymer, and all other components and concentrations and reaction conditions were the same, the product obtained was irregular silver grains, and the silver nanowires as shown in Example 1 were not obtained. This indicates that under low temperature conditions, macromolecular surfactants can control the growth direction of silver grains and promote the formation of silver nanowires.

[0091] This invention proposes a method for preparing silver nanowires, which has the following advantages: by using a self-made ionic organic coating, silver nanowires can be prepared under conditions of lower temperature and shorter time. This preparation method is simple, safe, and has a high yield, and the obtained silver nanowires have better quality and more uniform morphology.

[0092] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a nanosilver wire, characterized by, The preparation method comprises the following steps: Mixing a macromolecular surfactant, a solvent, a silver salt and a catalyst to obtain a first reaction solution; the macromolecular surfactant is histamine acrylamide polymer; Mixing a reducing agent and a solvent to obtain a second reaction solution; Injecting the first reaction solution and the second reaction solution into a reaction kettle at a constant rate at a temperature of 30-60℃ for 8-12 min to obtain a product solution; Centrifuging the product solution to obtain nanosilver wires.

2. The production method according to claim 1, characterized by, The molar concentration of the macromolecular surfactant ranges from 0.15 to 0.75 M; The molar concentration of the silver salt ranges from 0.1 to 0.5 M; The molar concentration of the reducing agent ranges from 0.4 to 2 M; The molar concentration of the catalyst ranges from 0.2 to 1.2 mM; The solvent is deionized water.

3. The method of claim 1, wherein, The relative molecular weight of the histamine acrylamide polymer ranges from 5000 to 20000, and the molecular weight distribution ranges from 1.05 to 1.

5.

4. The method of claim 1, wherein, The histamine acrylamide polymer is formed by the following method: Mixing histamine dihydrochloride, sodium hydroxide and deionized water in a reaction kettle; then, continuously adding a mixed solution of acryloyl chloride and carbon tetrachloride into the reaction kettle for reaction, and then extracting, freeze-drying, hot dissolving, filtering and drying the reaction solution to obtain histamine acrylamide monomer; Mixing the histamine acrylamide monomer, a chain transfer agent, a thermal initiator and deionized water uniformly, and performing free radical polymerization at a temperature of 70-90℃ to obtain histamine acrylamide polymer.

5. The preparation method according to claim 1, characterized in that, The silver salt comprises at least one of silver nitrate, silver fluoride, silver chlorate, silver perchlorate, silver ammine complex, silver sulfate and silver acetate.

6. The method of claim 1, wherein, The reducing agent comprises at least one of ascorbic acid, sodium ascorbate, oxalic acid, formaldehyde, acetaldehyde, glyoxal, sodium borohydride and hydrazine hydrate.

7. The preparation method according to claim 1, characterized in that, The catalyst comprises at least one of sodium chloride, sodium bromide, copper chloride, copper chloride dihydrate, iron chloride, iron bromide and copper bromide.

8. The method of claim 1, wherein, The constant rate is 0.1-5 L / min.

9. The method of claim 1, wherein, The centrifugation speed ranges from 1000 to 8000 r / min.

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