A method for preparing silver nanowires based on seed crystal regulation
By employing a seed-based preparation method and a fast nucleation + slow growth strategy, the problem of separating the nucleation and growth processes of silver nanowires was solved, achieving the preparation of high-purity and uniform silver nanowires and improving the aspect ratio and morphology controllability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHIJIAZHUANG TIEDAO UNIV
- Filing Date
- 2026-06-04
- Publication Date
- 2026-07-24
AI Technical Summary
In existing technologies, the nucleation and growth processes of silver nanowires are difficult to separate effectively, making it difficult to precisely control the nucleation process, resulting in a large number of silver nanoparticle byproducts, and the silver nanowires have insufficient uniformity and unsatisfactory aspect ratio.
A seed-controlled preparation method was adopted, which uses a combination of fast nucleation and slow growth to achieve continuous and uniform nucleation with the moderate reduction rate of formic acid, generating silver seed crystals with small particle size and narrow distribution. The addition of seed solution in polyol solution was controlled to reduce silver nanoparticle byproducts and improve the purity and uniformity of silver nanowires.
This method achieves high purity and uniformity of silver nanowires, shortens the seed preparation time, controls the size and number of seed crystals, and improves the aspect ratio and morphology controllability of silver nanowires.
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Figure CN122441964A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of silver nanowire preparation technology, and in particular to a method for preparing silver nanowires based on seed control. Background Technology
[0002] Silver nanowires, as one of the typical materials in the field of nanomaterials, have become a nanomaterial with great development potential in the fields of transparent films, nanochips and other electronic information due to their high aspect ratio (up to 1000), high light transmittance (transmittance >90% in the visible light range), and excellent high electrical conductivity.
[0003] Silver nanowires can be synthesized using methods such as the polyol method, photoreduction method, hard template method, and microwave-assisted synthesis. The polyol method is one of the most promising methods due to its simplicity and high yield. However, this method typically involves the simultaneous nucleation and crystal growth of silver ions in the same reaction system, making it difficult to effectively separate nucleation and growth. This leads to inaccurate control of the nucleation process and the generation of a large number of silver nanoparticles as byproducts. Furthermore, the uniformity of the silver nanowires is insufficient; silver nanowires prepared using existing techniques often exhibit a wide aspect ratio. Therefore, effectively controlling the nucleation and growth processes and improving morphology controllability are urgent technical problems that need to be solved. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing silver nanowires based on seed crystal regulation, so as to solve the problems existing in the prior art.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing silver nanowires based on seed-controlled crystals, comprising the following steps: (1) Mix silver salt solution 1 and ammonia water to carry out a complexation reaction to obtain silver ammonia solution; (2) After mixing polyvinylpyrrolidone solution 1 and silver ammonia solution, formic acid solution is added to carry out redox reaction to obtain seed crystal solution; (3) Mix the polyvinylpyrrolidone solution 2, seed solution and sodium chloride solution preheated to the reaction temperature, and then add silver salt solution 2 to carry out the reaction to obtain silver nanowires.
[0006] Optionally, the silver salt solution 1 is composed of silver salt and water; the concentration of the silver salt solution 1 is 0.05~0.5 mol / L; the silver salt solution 1 includes silver nitrate solution.
[0007] Optionally, the concentration of the ammonia solution is 0.3~0.6 mol / L; the volume ratio of the silver salt solution 1 to the ammonia solution is 1:0.5~1.
[0008] Optionally, the complexation reaction is carried out at room temperature for 1 to 5 minutes.
[0009] Optionally, the polyvinylpyrrolidone solution 1 is composed of polyvinylpyrrolidone and ethylene glycol; the concentration of the polyvinylpyrrolidone solution 1 is 1.5~25 mmol / L; the molecular weight of the polyvinylpyrrolidone is 58000~300000; and the molar ratio of the polyvinylpyrrolidone to the silver salt in the silver salt solution 1 is 3~6:1.
[0010] Optionally, the formic acid solution is composed of formic acid and ethylene glycol; the concentration of the formic acid solution is 0.3~0.6 mol / L; and the molar ratio of formic acid to silver salt in silver salt solution 1 is 1:2.
[0011] Optionally, the redox reaction is carried out at room temperature for 0.2 to 3 minutes.
[0012] Optionally, the silver salt solution 2 is composed of silver salt and ethylene glycol, wherein the silver salt includes silver nitrate; the sodium chloride solution is composed of sodium chloride and ethylene glycol; the polyvinylpyrrolidone solution 2 is composed of polyvinylpyrrolidone and ethylene glycol; and the molecular weight of the polyvinylpyrrolidone is 58,000 to 300,000.
[0013] Optionally, the concentration of the silver salt solution 2 is 0.1~0.5 mol / L; the concentration of the polyvinylpyrrolidone solution 2 is 0.1~1 mol / L; and the concentration of the sodium chloride solution is 4~60 mmol / L. The volume ratio of the polyvinylpyrrolidone solution 2, the seed crystal solution, the sodium chloride solution, and the silver salt solution 2 is 55~65:100:10~15:25~30.
[0014] Optionally, in step (3), the silver salt solution 2 is added by dropping; the dropping rate is 0.5~2 mL / min; The reaction temperature in step (3) is 140~160℃ and the reaction time is 0.5~3h.
[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a fast nucleation + slow growth method to prepare silver nanowires. During the preparation of the seed solution, formic acid exhibits a moderate reduction rate, enabling continuous and uniform nucleation, thereby obtaining silver seeds with small particle size and narrow distribution, shortening the seed preparation time, and controlling the seed size and quantity. Furthermore, adding the seed solution to a modified polyol solution reduces silver nanoparticle byproducts and improves the purity and uniformity of the silver nanowires. Attached Figure Description
[0016] Figure 1 The image shows the XRD pattern of the silver nanowires from Example 1. Figure 2 Here is a SEM image of the silver nanowires from Example 1; Figure 3 Here is a SEM image of the silver nanowires from Example 2; Figure 4 Here is a SEM image of the silver nanowires in Comparative Example 1; Figure 5 This is a SEM image of the silver nanowires in Comparative Example 2. Detailed Implementation
[0017] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0018] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0019] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.
[0020] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.
[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0022] The room temperature involved in the embodiments of the present invention is 25±2℃.
[0023] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.
[0024] This invention provides a method for preparing silver nanowires based on seed-controlled crystals, comprising the following steps: (1) Mix silver salt solution 1 and ammonia water to carry out a complexation reaction to obtain silver ammonia solution; (2) After mixing polyvinylpyrrolidone solution 1 and silver ammonia solution, formic acid solution is added to carry out redox reaction to obtain seed crystal solution; (3) Mix the polyvinylpyrrolidone solution 2, seed solution and sodium chloride solution preheated to the reaction temperature, and then add silver salt solution 2 to carry out the reaction to obtain silver nanowires.
[0025] Step (1) of the present invention is to add ammonia water dropwise to silver salt solution 1 until the solution becomes clear, thus obtaining silver ammonia solution.
[0026] In this invention, the silver salt solution 1 is composed of silver salt and water; the concentration of the silver salt solution 1 is 0.05~0.5 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L or 0.5 mol / L, etc.; the silver salt solution 1 includes silver nitrate solution.
[0027] In this invention, the concentration of the ammonia water is 0.3~0.6 mol / L, for example, it can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.6 mol / L, etc.; the volume ratio of the silver salt solution 1 to the ammonia water is 1:0.5~1, for example, it can be 1:0.5 or 1:1, etc.
[0028] In this invention, the complexation reaction is carried out at room temperature for 1 to 5 minutes.
[0029] Step (2) of this invention involves pouring polyvinylpyrrolidone solution 1 into silver ammonia solution, stirring evenly at room temperature, and then adding formic acid solution dropwise to carry out an oxidation-reduction reaction to obtain a seed crystal solution.
[0030] In some embodiments of the present invention, the formic acid solution is slowly dripped in using a pipette.
[0031] In a preferred embodiment of the present invention, the seed solution can be purified by centrifugation and redispersed in ethylene glycol solution to form a new seed solution.
[0032] In this invention, the polyvinylpyrrolidone solution 1 is composed of polyvinylpyrrolidone and ethylene glycol; the concentration of the polyvinylpyrrolidone solution 1 is 1.5~25 mmol / L, for example, it can be 1.5 mmol / L, 3.5 mmol / L, 5.5 mmol / L, 7.5 mmol / L, 10 mmol / L, 12 mmol / L, 15 mmol / L, 17 mmol / L, 20 mmol / L or 25 mmol / L, etc.; the molecular weight of the polyvinylpyrrolidone is 58,000~300,000, for example, it can be 58,000, 100,000, 150,000, 200,000 or 300,000, etc., and the molar mass is 111.14 g / mol calculated based on the repeating unit of polyvinylpyrrolidone; the molar ratio of polyvinylpyrrolidone to silver salt in silver salt solution 1 is 3~6:1, for example, it can be 3:1, 4:1, 5:1 or 6:1, etc.
[0033] In this invention, the formic acid solution is composed of formic acid and ethylene glycol; the concentration of the formic acid solution is 0.3~0.6 mol / L, for example, it can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L or 0.6 mol / L, etc.; the molar ratio of formic acid and silver salt in silver salt solution 1 is 1:2.
[0034] In this invention, the redox reaction is carried out at room temperature for 0.2 to 3 minutes, for example, 0.2 minutes, 1 minute, 2 minutes or 3 minutes.
[0035] In this invention, the stirring speed is 200~400 rpm, for example, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm.
[0036] Step (3) of this invention involves preheating polyvinylpyrrolidone solution 2 to the reaction temperature, then adding sodium chloride solution and seed crystal solution to it, and finally adding silver salt solution 2 dropwise, mixing and stirring evenly to obtain silver nanowires.
[0037] In this invention, the silver salt solution 2 is composed of silver salt and ethylene glycol, wherein the silver salt includes silver nitrate; the sodium chloride solution is composed of sodium chloride and ethylene glycol; the polyvinylpyrrolidone solution 2 is composed of polyvinylpyrrolidone and ethylene glycol; the molecular weight of the polyvinylpyrrolidone is 58,000 to 300,000, for example, it can be 58,000, 100,000, 150,000, 200,000 or 300,000, etc., and the molar mass is 111.14 g / mol calculated based on the repeating unit of polyvinylpyrrolidone.
[0038] In this invention, the concentration of the silver salt solution 2 is 0.1~0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L, etc.; the concentration of the polyvinylpyrrolidone solution 2 is 0.1~1 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, or 1 mol / L, etc.; the concentration of the sodium chloride solution is 4~60 mmol / L, for example, it can be 4 mmol / L, 15 mmol / L, 25 mmol / L, 35 mmol / L, 45 mmol / L, or 60 mmol / L, etc. The volume ratio of the polyvinylpyrrolidone solution 2, the seed crystal solution, the sodium chloride solution, and the silver salt solution 2 is 55~65:100:10~15:25~30.
[0039] In this invention, the silver salt solution 2 in step (3) is added by dripping; the dripping rate is 0.5~2mL / min, for example, it can be 0.5mL / min, 1mL / min, 1.5mL / min or 2mL / min, etc. The reaction temperature in step (3) is 140~160℃, for example, it can be 140℃, 150℃ or 160℃, and the time is 0.5~3h, for example, it can be 0.5h, 1h, 1.5h, 2h or 3h.
[0040] In this invention, after the silver nanowires are prepared, they need to be centrifuged and purified. The centrifugation purification method is as follows: cool the crude silver nanowires obtained in step (3) to room temperature, add acetone, centrifuge and remove the supernatant; add deionized water and ethanol to the precipitate obtained by centrifugation, stir and centrifuge again, repeat the above washing steps 2 to 3 times to obtain purified silver nanowires.
[0041] In this invention, the total volume ratio of acetone, deionized water and ethanol to the crude silver nanowire product is 2 to 5:1, for example, it can be 2:1, 3:1, 4:1 or 5:1.
[0042] In this invention, the centrifugation speed is 3000~5000 r / min, for example, 3000 r / min, 4000 r / min or 5000 r / min, and the centrifugation time is 5~10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.
[0043] This invention uses a mixture of ammonia and silver nitrate solution to obtain a silver ammonia solution. Polyvinylpyrrolidone (PVP) is then added dropwise followed by formic acid solution. The solutions are mixed at room temperature. Formic acid reacts with the silver ammonia complex ions in a redox reaction, exhibiting a moderate reduction rate that allows for continuous and uniform nucleation. The PVP coating reduces agglomeration, shortens seed crystal preparation time, generates more uniform small-sized seed crystals, controls the initial size distribution, and narrows the line diameter range. A stable seed crystal dispersion with low impurity ion content can be obtained through centrifugal purification and ethylene glycol redispersion.
[0044] This invention involves adding a seed crystal solution and sodium chloride solution to a preheated fresh PVP solution, followed by the dropwise addition of silver nitrate solution while stirring to ensure uniform dispersion. Under heating conditions, silver ions in the silver nitrate solution are reduced by ethylene glycol and crystallize around the silver nanoparticles contained in the seed crystals, forming nanoparticles that adsorb onto the long chains of PVP. - It also has an adsorption effect on the (100) crystal plane of silver nanowires, which can promote the formation of one-dimensional silver nanowires. By constructing a stepwise synthesis system of "seed preparation - separation and purification - redispersion - controlled growth", the nucleation and growth process of silver nanowires was realized.
[0045] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0046] Example 1 (1) Dissolve 0.25 mmol of silver nitrate in 2 ml of water, and add 1 ml of 0.5 M ammonia solution to the silver nitrate solution (you can add a few more drops depending on the actual situation) until the solution is clear, and record it as solution A; (2) Take 1.26 mmol of PVP with a molecular weight of 58000 and dissolve it in 96.75 ml of ethylene glycol. Pour the well-stirred PVP-ethylene glycol solution into solution A and mix it well. This solution is called solution B. (3) Dissolve formic acid in ethylene glycol to prepare a 0.5 M formic acid-ethylene glycol solution. Take 0.25 ml of the formic acid-ethylene glycol solution and slowly add it dropwise into solution B with a pipette. Stir the reaction for 3 min to obtain a seed crystal solution.
[0047] (4) Prepare a new PVP-ethylene glycol solution: Dissolve 47.5 mmol of PVP with a molecular weight of 58000 in 60 ml of ethylene glycol, heat to 160°C, and then add sodium chloride-ethylene glycol solution (0.3 mmol of sodium chloride dissolved in 10 ml of ethylene glycol) to the preheated PVP-ethylene glycol solution. After mixing evenly, add 100 mL of seed crystal solution to obtain solution C. (5) Dissolve 9.5 mmol of silver nitrate in 30 ml of ethylene glycol to prepare a new silver nitrate-ethylene glycol solution, which is denoted as solution D; (6) Add solution D dropwise to solution C at a rate of 1 ml / min, mix and stir, and heat for 1 h. After the reaction is complete, centrifuge and purify to obtain silver nanowire solution.
[0048] Figure 1 This is the XRD pattern of the silver nanowires from Example 1, by... Figure 1 It can be seen that high-purity, high-crystallinity silver nanowires were prepared in Example 1.
[0049] Figure 2 The image shows a scanning electron microscope image of the silver nanowires from Example 1. The average diameter of the obtained silver nanowires is 30 nm, and the aspect ratio is 50~300.
[0050] Example 2 (1) Dissolve 0.1 mmol of silver nitrate in 1 ml of water, and add 1 ml of 0.5 M ammonia solution to the silver nitrate solution (a few more drops can be added depending on the actual situation) until the solution is clear, and record it as solution A; (2) Take 0.5 mmol of PVP with a molecular weight of 58000 and dissolve it in 97.75 ml of ethylene glycol. Pour the well-stirred PVP-ethylene glycol solution into solution A and mix it well. This solution is called solution B. (3) Dissolve formic acid in ethylene glycol to prepare a 0.5 M formic acid-ethylene glycol solution. Take 0.1 ml of the formic acid-ethylene glycol solution and slowly add it dropwise into solution B with a pipette. Stir the reaction for 3 min to obtain a seed solution.
[0051] (4) Prepare a new PVP-ethylene glycol solution: Dissolve 47.5 mmol of PVP with a molecular weight of 58000 in 60 ml of ethylene glycol, heat to 160°C, and then add sodium chloride-ethylene glycol solution (0.3 mmol of sodium chloride dissolved in 10 ml of ethylene glycol) to the preheated PVP-ethylene glycol solution. After mixing evenly, add 100 mL of seed crystal solution to obtain solution C. (5) Dissolve 9.5 mmol of silver nitrate in 30 ml of ethylene glycol to prepare a new silver nitrate-ethylene glycol solution, which is denoted as solution D; (6) Add solution D dropwise to solution C at a rate of 1.5 ml / min, mix and stir, and heat for 1.5 h. After the reaction is complete, centrifuge and purify to obtain silver nanowire solution.
[0052] Figure 3 The image shows a scanning electron microscope image of the silver nanowires from Example 2. The average diameter of the obtained silver nanowires is 110 nm, and the aspect ratio is 20-300.
[0053] Comparative Example 1 The only difference from Example 1 is that the stirring time in step (3) is changed to 10 min to obtain the seed solution; the heating and holding time in step (6) is adjusted to 1.5 h, and the other parameters and steps are the same as in Example 1.
[0054] Figure 4 The image shows a scanning electron microscope image of silver nanowires in Comparative Example 1. The average diameter of the silver nanowires is 40 nm, and the aspect ratio is 30~250.
[0055] In comparison, after the reaction time of the seed crystals in Comparative Example 1 was extended, the seed crystals formed became larger and some of them were transformed into spherical particles, resulting in more particles in the final silver nanowires than in Example 1.
[0056] Comparative Example 2 (1) Preparation of PVP-ethylene glycol solution: Take 27.5 mmol of PVP with a molecular weight of 58000 and dissolve it in 160 ml of ethylene glycol. Heat it to 160°C. Then add sodium chloride-ethylene glycol solution formed by dissolving 0.18 mmol of sodium chloride in 10 ml of ethylene glycol to the preheated PVP-ethylene glycol solution. Mix well to obtain solution A. (2) Dissolve 5.5 mmol of silver nitrate in 30 ml of ethylene glycol to prepare a new silver nitrate-ethylene glycol solution, which is denoted as solution B; (3) Add solution B dropwise to solution A at a rate of 1 ml / min, mix and stir, and heat for 1 h. After the reaction is complete, centrifuge and purify to obtain silver nanowire solution.
[0057] Figure 5 This is a scanning electron microscope image of the silver nanowires in Comparative Example 2. The average diameter of the obtained silver nanowires is 130 nm, and the aspect ratio is 50~380.
[0058] In comparison, without the addition of the initial seed solution in Comparative Example 2, the resulting silver nanowires had larger particle sizes and some were transformed into spherical particles, resulting in more particles in the final silver nanowires compared to Example 1.
[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing silver nanowires based on seed crystal regulation, characterized in that, Includes the following steps: (1) Mix silver salt solution 1 and ammonia water to carry out a complexation reaction to obtain silver ammonia solution; (2) After mixing polyvinylpyrrolidone solution 1 and silver ammonia solution, formic acid solution is added to carry out redox reaction to obtain seed crystal solution; (3) Mix the polyvinylpyrrolidone solution 2, seed solution and sodium chloride solution preheated to the reaction temperature, and then add silver salt solution 2 to carry out the reaction to obtain silver nanowires.
2. The preparation method according to claim 1, characterized in that, The silver salt solution 1 is composed of silver salt and water; the concentration of the silver salt solution 1 is 0.05~0.5 mol / L; the silver salt solution 1 includes silver nitrate solution.
3. The preparation method according to claim 2, characterized in that, The concentration of the ammonia solution is 0.3~0.6 mol / L; the volume ratio of the silver salt solution 1 to the ammonia solution is 1:0.5~1.
4. The preparation method according to claim 1, characterized in that, The complexation reaction was carried out at room temperature for 1 to 5 minutes.
5. The preparation method according to claim 1, characterized in that, The polyvinylpyrrolidone solution 1 is composed of polyvinylpyrrolidone and ethylene glycol; the concentration of the polyvinylpyrrolidone solution 1 is 1.5~25 mmol / L; the molecular weight of the polyvinylpyrrolidone is 58000~300000; and the molar ratio of the polyvinylpyrrolidone to the silver salt in the silver salt solution 1 is 3~6:
1.
6. The preparation method according to claim 1, characterized in that, The formic acid solution is composed of formic acid and ethylene glycol; the concentration of the formic acid solution is 0.3~0.6 mol / L; the molar ratio of formic acid to silver salt in silver salt solution 1 is 1:
2.
7. The preparation method according to claim 1, characterized in that, The redox reaction was carried out at room temperature for 0.2 to 3 minutes.
8. The preparation method according to claim 1, characterized in that, The silver salt solution 2 is composed of silver salt and ethylene glycol, and the silver salt includes silver nitrate; the sodium chloride solution is composed of sodium chloride and ethylene glycol; the polyvinylpyrrolidone solution 2 is composed of polyvinylpyrrolidone and ethylene glycol; the molecular weight of the polyvinylpyrrolidone is 58,000 to 300,000.
9. The preparation method according to claim 8, characterized in that, The concentration of the silver salt solution 2 is 0.1~0.5 mol / L; the concentration of the polyvinylpyrrolidone solution 2 is 0.1~1 mol / L; and the concentration of the sodium chloride solution is 4~60 mmol / L. The volume ratio of the polyvinylpyrrolidone solution 2, the seed crystal solution, the sodium chloride solution, and the silver salt solution 2 is 55~65:100:10~15:25~30.
10. The preparation method according to claim 1, characterized in that, In step (3), the silver salt solution 2 is added by dropping; the dropping rate is 0.5~2 mL / min; The reaction temperature in step (3) is 140~160℃ and the reaction time is 0.5~3h.