High-purity and high-aspect-ratio silver nanowires, and preparation method and application thereof

Abstract

The application belongs to the field of nanometer materials, and discloses a kind of silver nanowires with high purity and high aspect ratio and its preparation method and application.The method comprises the following steps: template agent is dissolved in reducing agent, heated to initial temperature 80-110 DEG C under stirring dissolution, and a transparent solution is obtained; control agent solution and silver salt solution are added to the transparent solution, the reaction vessel is sealed, and the solution is fully reacted from white to red brown; the reaction solution is heated to 140-160 DEG C for the second time, and the silver nanowires with high purity and high aspect ratio are obtained after full reaction.The impurities of the obtained silver nanowires are close to 0, the aspect ratio reaches 2000, and the application of the silver nanowires as a filler of composite material in the fields of transparent conductive film, sensor, solar cell and surface enhanced raman scattering.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanomaterials, and particularly relates to a silver nanowire with high purity and high aspect ratio, and a preparation method and application thereof. BACKGROUND

[0002] As a one-dimensional nanomaterial, silver nanowires have very high carrier concentration like bulk metal silver, and also have small size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect, which are quite different from bulk metal silver. Therefore, silver nanowires have excellent properties of electrical conductivity, thermal conductivity, optical, catalysis, magnetism, antibacterial, etc., and these properties make silver nanowires as nanofillers of various composite materials, which are widely studied and applied in transparent conductive films, various sensors, solar cells, conductive adhesives, SERS technology, etc.

[0003] Nowadays, there are many synthesis methods of silver nanowires, mainly including soft and hard template method, microwave-assisted synthesis method, wet chemical method, polyol method, etc. Among them, the polyol method is the most commonly used method because it has the advantages of simple equipment and simple operation process. However, the traditional polyol method for synthesizing silver nanowires inevitably forms by-products such as silver nanoparticles and silver nanorods, which greatly reduces the performance of silver nanowires. Although some methods can be used to purify silver nanowires, the purification process is time-consuming and costly. Therefore, it is necessary to innovate and improve the synthesis of silver nanowires with high purity and strong uniformity on the basis of the polyol synthesis.

[0004] The key properties of silver nanowires are their aspect ratio and size uniformity, which have a significant impact on their performance characteristics (e.g., electrical conductivity, optical transparency, and mechanical strength) in various applications. Specifically, the high aspect ratio and size uniformity of silver nanowires result in high optical transparency, low haze, and low sheet resistance, and therefore it is necessary to synthesize silver nanowires with high aspect ratio for applications.

[0005] Chinese patent CN106623966A, a method for preparing silver nanowires based on ionic liquid and silver nanowires prepared thereby, wherein the method comprises the following steps: (1) adding water-soluble silver salt and dispersing agent into polyhydroxy liquid organic matter to obtain a mixed solution; (2) adding ionic liquid into the mixed solution obtained in step (1) to obtain a reaction mother liquor; the concentration of water-soluble silver salt in the reaction mother liquor is 0.01-1.0 mol / L, the concentration of dispersing agent is 0.01-10.0 mol / L, and the concentration of ionic liquid is 0.0001-0.005 mol / L, based on the total volume of the reaction mother liquor; (3) reacting the reaction mother liquor obtained in step (2), and after the reaction is completed, the silver nanowires are obtained. The silver nanowires prepared by the method provided by the present application have a diameter of less than 60 nm. However, the synthesis of the method will produce impurities, and purification is required, which limits the synthesis and application of silver nanowires. SUMMARY

[0006] In order to overcome the shortcomings and deficiencies existing in the prior art, the primary purpose of the present application is to provide a method for preparing silver nanowires with high purity and high aspect ratio; the method can quickly synthesize silver nanowires with high purity and high aspect ratio without other impurities (such as silver nanoparticles, silver nanorods, etc.).

[0007] Another purpose of the present application is to provide silver nanowires with high purity and high aspect ratio prepared by the above preparation method.

[0008] Another purpose of the present application is to provide the application of the above silver nanowires with high purity and high aspect ratio.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] A method for preparing silver nanowires with high purity and high aspect ratio, comprising the following operation steps:

[0011] (1) 20-25 parts by weight of a template agent is dissolved in 750-1000 parts by weight of a reducing agent, heated to a starting temperature of 80-110 DEG C and stirred to dissolve, to obtain a transparent solution; 0.5-2 parts by weight of a control agent is dissolved in 150-250 parts by weight of a reducing agent to obtain a control agent solution, and 7-10 parts by weight of a silver salt is dissolved in 50-100 parts by weight of a reducing agent to obtain a silver salt solution;

[0012] (2) The control agent solution and the silver salt solution are added to the transparent solution, the reaction container is sealed, and the solution is fully reacted from white to red-brown;

[0013] (3) The reaction solution is heated to 140-160 DEG C again, and after full reaction, silver nanowires with high purity and high aspect ratio are obtained.

[0014] The amount of the template agent in step (1) is 22.032 parts by weight, which is dissolved in 993.56 parts by weight of the reducing agent; the amount of the control agent is 1 part by weight, which is dissolved in 63.41 parts by weight of the reducing agent; the amount of the silver salt is 9.67 parts by weight, which is dissolved in 211.396 parts by weight of the reducing agent.

[0015] The template agent in step (1) is polyvinylpyrrolidone (PVP), specifically including polyvinylpyrrolidone K30, polyvinylpyrrolidone K60, polyvinylpyrrolidone K90 or polyvinylpyrrolidone K120;

[0016] The control agent is ferric chloride, copper chloride, nickel chloride, sodium chloride or potassium bromide;

[0017] The silver salt is silver nitrate and / or silver acetate;

[0018] The reducing agent is ethylene glycol.

[0019] More preferably, the template agent in step (1) is polyvinylpyrrolidone K120; the control agent is sodium chloride; and the silver salt is silver nitrate.

[0020] The stirring and dissolving time in step (1) is 1 hour; the sufficient reaction time in step (2) is 30 minutes; and the sufficient reaction time in step (3) is 1.5 hours.

[0021] The initial temperature in step (1) is 100℃, and the temperature of the second heating in step (2) is 140℃.

[0022] The impurity of the silver nanowire obtained in step (3) is close to 0, and the aspect ratio reaches 2000.

[0023] A high-purity and high-aspect-ratio silver nanowire prepared by the above preparation method.

[0024] The high-purity and high-aspect-ratio silver nanowire described above is used as a filler of a composite material in the fields of transparent conductive thin films, sensors, solar cells and surface enhanced Raman scattering (SERS).

[0025] The mechanism of the present application is as follows:

[0026] The main chemical reaction equation involved in the synthesis of silver nanowires is as follows:

[0027]

[0028] Cl - +Ag + →AgCl(b)

[0029] 2Ag ++2CH3CHO→CH3CHOOHCCH3+2Ag+2H + (c)

[0030] Ethylene glycol will generate acetaldehyde, a strong reducing agent, at temperatures above 110°C, which can quickly reduce Ag. + Restored to Ag 0 Reactions (b) and (c) are inherently competitive. However, AgCl can also act as a seed, adsorbing silver and enabling heterogeneous nucleation. The secondary heating utilizes the initial generation of stable AgCl, followed by increasing the temperature to provide sufficient energy for heterogeneous nucleation, resulting in high-purity, highly uniform silver nanowires.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] This invention successfully synthesized silver nanowires with an aspect ratio of approximately 2000 using a two-stage heating method. Compared to existing technologies, the silver nanowires synthesized using this method exhibit higher purity and stronger uniformity. The optimal conditions for synthesizing high-purity silver nanowires are an initial temperature of 100℃, a secondary temperature of 140℃, and a weight ratio of NaCl to AgNO3 of 1:9.67. The key to the two-stage heating is that the low temperature of 100℃ provides activation energy for the formation of stable AgCl, while the temperature is then increased to 140℃ to provide sufficient energy for ethylene glycol and PVP, acting as reducing agents during the rapid growth phase. This allows for the production of high-purity, highly uniform silver nanowires through heterogeneous nucleation, enabling their wide application as nanofillers in composite materials. Furthermore, the two-stage heating method eliminates the need for nitrogen gas, saving energy. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the silver nanowires prepared in Example 1 of the present invention;

[0034] Figure 2 This is a scanning electron microscope image of the silver nanowires prepared in Example 2 of the present invention;

[0035] Figure 3 This is a scanning electron microscope image of the silver nanowires prepared in Example 3 of the present invention;

[0036] Figure 4 This is a scanning electron microscope image of the silver nanowires prepared in Example 4 of the present invention;

[0037] Figure 5 This is a scanning electron microscope image of the silver nanowires prepared in Example 5 of the present invention;

[0038] Figure 6 This is a scanning electron microscope image of the silver nanowires prepared in Example 6 of the present invention;

[0039] Figure 7 A scanning electron microscope image of silver nanowires prepared in Example 7 of the present application;

[0040] Figure 8 A diameter and length distribution graph of silver nanowires prepared in Example 2 of the present application;

[0041] Figure 9 A scanning electron microscope image of silver nanowires prepared in Example 8 of the present application;

[0042] Figure 10 A scanning electron microscope image of silver nanowires prepared in Example 9 of the present application. DETAILED DESCRIPTION

[0043] The present application will be described in further detail by the following examples and drawings, but the embodiments of the present application are not limited thereto.

[0044] Unless otherwise specified, the examples were carried out under conventional conditions or under conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used were conventional products that can be commercially available.

[0045] Example 1

[0046] Example 1 of the present application provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0047] (1) 22.032 parts by weight of PVP was dissolved in 993.56 parts by weight of ethylene glycol (EG) and stirred at 80°C (initial temperature) for 1 hour to obtain a transparent solution;

[0048] (2) NaCl solution (1 part by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight dissolved in 211.396 parts by weight of EG) were added to the transparent solution, respectively, the flask was sealed and reacted for 30 minutes, and the solution changed from white to red-brown.

[0049] (3) The reaction solution was heated to 140°C for 1.5 hours to obtain a silver nanowire solution.

[0050] The silver nanowires prepared in Example 1 were analyzed by scanning electron microscopy, and the scanning electron microscope image is shown in Figure 1 As can be seen from Figure 1 , the average diameter of the silver nanowires prepared in this example is about 50 nm, the length is 100 um, and the aspect ratio is 2000, but there are very few impurities.

[0051] Example 2

[0052] The embodiment 2 provides a method for preparing silver nanowires based on a secondary heating method, which comprises the following steps:

[0053] (1) 22.032 parts by weight of PVP is dissolved in 993.56 parts by weight of ethylene glycol (EG) at 100 DEG C (initial temperature) to obtain a transparent solution;

[0054] (2) NaCl solution (1 part by weight of NaCl is dissolved in 63.41 parts by weight of EG to form a solution) and AgNO3 solution (9.67 parts by weight of AgNO3 is dissolved in 211.396 parts by weight of EG to form a solution) are respectively added into the transparent solution, the flask is sealed, and reaction is carried out for 30 minutes, and the solution changes from white to red brown.

[0055] (3) The reaction solution is secondarily heated to 140 DEG C, and reaction is carried out for 1.5 hours, and the silver nanowire solution is obtained.

[0056] The silver nanowires prepared in the embodiment 2 are subjected to scanning electron microscope analysis, and the scanning electron microscope graph is as shown in Figure 2 , and as shown in Figure 2 , the average diameter of the silver nanowires prepared in the embodiment is about 50 nm, the length is 100 um, the length-diameter ratio is 2000, the diameter and length distribution graph is Figure 8 , and there is no impurity.

[0057] Embodiment 3

[0058] The embodiment 3 provides a method for preparing silver nanowires based on a secondary heating method, which comprises the following steps:

[0059] (1) 22.032 parts by weight of PVP is dissolved in 993.56 parts by weight of ethylene glycol (EG) at 100 DEG C (initial temperature) to obtain a transparent solution;

[0060] (2) NaCl solution (1 part by weight of NaCl is dissolved in 63.41 parts by weight of EG to form a solution) and AgNO3 solution (9.67 parts by weight of AgNO3 is dissolved in 211.396 parts by weight of EG to form a solution) are respectively added into the transparent solution, the flask is sealed, and reaction is carried out for 30 minutes, and the solution changes from white to red brown.

[0061] (3) The reaction solution is secondarily heated to 140 DEG C, and reaction is carried out for 1.5 hours, and the silver nanowire solution is obtained.

[0062] The silver nanowires prepared in the embodiment 3 are subjected to scanning electron microscope analysis, and the scanning electron microscope graph is as shown in Figure 3 , and as shown in Figure 3It can be seen that the silver nanowires prepared in this embodiment have an average diameter of about 70 nm, a length of 100 μm, an aspect ratio of 1429, and too many impurities.

[0063] Example 4

[0064] This embodiment 4 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0065] (1) Take 22.032 parts by weight of PVP and dissolve it in 993.56 parts by weight of ethylene glycol (EG). Stir and dissolve at 140℃ (initial temperature) for 1 hour to obtain a transparent solution;

[0066] (2) Add NaCl solution (1 part by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) to the transparent solution respectively, seal the flask, and react for 30 minutes. The solution changes from white to reddish-brown.

[0067] (3) The reaction solution is heated to 140°C for 1.5 hours to obtain silver nanowire solution.

[0068] The silver nanowires prepared in Example 4 were analyzed by scanning electron microscopy, and their scanning electron microscopy images are shown below. Figure 4 As shown, by Figure 4 It can be seen that the silver nanowires prepared in this embodiment have an average diameter of about 80 nm, a length of 50 μm, an aspect ratio of 625, and contain many impurities.

[0069] Example 5

[0070] This embodiment 5 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0071] (1) Take 22.032 parts by weight of PVP and dissolve it in 993.56 parts by weight of ethylene glycol (EG). Stir and dissolve at 100℃ (initial temperature) for 1 hour to obtain a transparent solution.

[0072] (2) Add NaCl solution (1 part by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) to the transparent solution respectively, seal the flask, and react for 30 minutes. The solution changes from white to reddish-brown.

[0073] (3) The reaction solution is heated to 100°C for 1.5 hours to obtain silver nanowire solution.

[0074] The silver nanowires prepared in Example 5 were analyzed by scanning electron microscopy, and the scanning electron microscopy image is shown below. Figure 5 As shown, by Figure 5 It can be seen that silver nanowires cannot be obtained in this embodiment.

[0075] Example 6

[0076] This embodiment 6 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0077] (1) Take 22.032 parts by weight of PVP and dissolve it in 993.56 parts by weight of ethylene glycol (EG). Stir and dissolve at 100℃ (initial temperature) for 1 hour to obtain a transparent solution.

[0078] (2) Add NaCl solution (1 part by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) to the transparent solution respectively, seal the flask, and react for 30 minutes. The solution changes from white to reddish-brown.

[0079] (3) The reaction solution is heated to 120°C for a second time and reacted for 1.5 hours to obtain a silver nanowire solution.

[0080] The silver nanowires prepared in Example 6 were analyzed by scanning electron microscopy, and the scanning electron microscopy image is shown below. Figure 6 As shown, by Figure 6 As can be seen, only a small amount of silver nanowires can be obtained in this embodiment.

[0081] Example 7

[0082] This embodiment 7 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0083] (1) Take 22.032 parts by weight of PVP and dissolve it in 993.56 parts by weight of ethylene glycol (EG). Stir and dissolve at 100℃ (initial temperature) for 1 hour to obtain a transparent solution.

[0084] (2) Add NaCl solution (1 part by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) to the transparent solution respectively, seal the flask, and react for 30 minutes. The solution changes from white to reddish-brown.

[0085] (3) The reaction solution is heated to 160°C for a second time and reacted for 1.5 hours to obtain a silver nanowire solution.

[0086] The silver nanowires prepared in this Example 7 were analyzed by scanning electron microscopy, and the scanning electron microscopy image is shown in Figure 7 As can be seen from the image, the average diameter of the silver nanowires prepared in this Example is about 140 nm, the length is 100 um, the aspect ratio is 714, and there are very few impurities. Figure 7

[0087] Example 8

[0088] This Example 8 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0089] (1) 22.032 parts by weight of PVP were dissolved in 993.56 parts by weight of ethylene glycol (EG) at 100°C (initial temperature) and stirred for 1 hour to obtain a transparent solution;

[0090] (2) NaCl solution (0.5 parts by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) were added to the transparent solution, respectively, the flask was sealed, and the solution was fully reacted for 30 minutes, and the solution changed from white to red-brown.

[0091] (3) The reaction solution was heated to 140°C for 1.5 hours to obtain a silver nanowire solution.

[0092] The silver nanowires prepared in this Example 8 were analyzed by scanning electron microscopy, and the scanning electron microscopy image is shown in Figure 9 As can be seen from the image, the average diameter of the silver nanowires prepared in this Example is about 90 nm, the length is 50 um, the aspect ratio is 555, and there are no impurities. Figure 9 Example 9

[0093] This Example 9 provides a method for preparing silver nanowires based on a secondary heating method, which includes the following steps:

[0094] (1) 22.032 parts by weight of PVP were dissolved in 993.56 parts by weight of ethylene glycol (EG) at 100°C (initial temperature) and stirred for 1 hour to obtain a transparent solution;

[0095] (2) NaCl solution (2 parts by weight of NaCl dissolved in 63.41 parts by weight of EG) and AgNO3 solution (9.67 parts by weight of AgNO3 dissolved in 211.396 parts by weight of EG) were added to the transparent solution, respectively, the flask was sealed, and the solution was fully reacted for 30 minutes, and the solution changed from white to red-brown.

[0096]

[0097] ​​(3) The reaction solution is heated to 140°C for 1.5 hours to obtain silver nanowire solution.

[0098] The silver nanowires prepared in Example 9 were analyzed by scanning electron microscopy, and the scanning electron microscopy image is shown below. Figure 10 As shown, by Figure 10 It can be seen that the silver nanowires prepared in this embodiment have an average diameter of about 45 nm, a length of 100 μm, an aspect ratio of 2222, and only a small amount of impurities.

[0099] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity silver nanowires with a high aspect ratio, characterized in that... The following steps are included: (1) Take 20-25 parts by weight of template agent and dissolve it in 750-1000 parts by weight of reducing agent, heat it to the initial temperature of 80℃-110℃ and stir to dissolve it to obtain a transparent solution; take 0.5-2 parts by weight of control agent and dissolve it in 150-250 parts by weight of reducing agent to obtain control agent solution; take 7-10 parts by weight of silver salt and dissolve it in 50-100 parts by weight of reducing agent to obtain silver salt solution; The template agent includes polyvinylpyrrolidone K30, polyvinylpyrrolidone K60, polyvinylpyrrolidone K90, or polyvinylpyrrolidone K120; the control agent is ferric chloride, copper chloride, nickel chloride, sodium chloride, or potassium bromide; the silver salt is silver nitrate and / or silver acetate; the reducing agent is ethylene glycol; (2) Add the control agent solution and silver salt solution to the transparent solution, seal the reaction vessel, and allow it to react fully. The solution will change from white to reddish-brown. (3) The reaction solution is heated to 140℃-160℃ for a second time. After the reaction is complete, high-purity silver nanowires with a high aspect ratio are obtained. The impurities of the obtained silver nanowires are close to 0, and their aspect ratio reaches 2000.

2. The preparation method according to claim 1, characterized in that: In step (1), the amount of template agent is 22.032 parts by weight, which is dissolved in 993.56 parts by weight of reducing agent; the amount of control agent is 1 part by weight, which is dissolved in 63.41 parts by weight of reducing agent; and the amount of silver salt is 9.67 parts by weight, which is dissolved in 211.396 parts by weight of reducing agent.

3. The preparation method according to claim 1, characterized in that: The template agent in step (1) is polyvinylpyrrolidone K120; the control agent is sodium chloride; and the silver salt is silver nitrate.

4. The preparation method according to claim 1, characterized in that: The stirring and dissolving time in step (1) is 1 hour; the reaction time in step (2) is 30 minutes; and the reaction time in step (3) is 1.5 hours.

5. The preparation method according to claim 1, characterized in that: The initial temperature in step (1) is 100℃, and the temperature for the secondary heating in step (2) is 140℃.

6. A high-purity silver nanowire with a high aspect ratio prepared by the preparation method according to any one of claims 1-5.

7. The application of the high-purity and high aspect ratio silver nanowires as described in claim 6 as fillers in composite materials in the fields of transparent conductive films, sensors, solar cells and surface-enhanced Raman scattering.

Images