JP5219287B2 - Continuous production method of silver nanowires - Google Patents

Description

  The present invention relates to a continuous production method of silver nanowires, and in particular, the present invention relates to a mass production method of high-quality silver nanowires.

One-dimensional nanostructures such as nanowires, nanotubes, nanorods or nanofibers have different properties than one-dimensional macromaterials. Recently, many industries and groups have continually studied the application of one-dimensional nanostructures and have achieved some important results. This application includes ultra-thin full color LED panels, photoreplicators, field emission, power consuming nanowire LEDs, and sensors for the detection of NH ₃ or H ₂ .

  One-dimensional metal nanostructures such as gold, tin, silver or platinum have good electrical properties for application to lead wire materials. Micro-effects such as surface effects, quantum effects, and tunneling effects become apparent at the nanoscale, and one-dimensional metal nanostructures are suitable for various electrical nanodevices utilizing this micro-effect. Furthermore, one-dimensional metal nanostructures are suitable as materials for electrodes, low temperature conductor pastes, superconducting thick film circuits, and microwave and electromagnetic wave absorption. Silver is an optimal conductor, so the application of silver nanowires is considered an important issue.

  However, only nanotubes, not one-dimensional metallic nanomaterials having a high conductivity effect, have been commercialized in the business field. There are several methods for producing one-dimensional metal nanowires, but these methods have certain disadvantages for commercialization. The disadvantages of the prior art method for producing a one-dimensional metal nanowire are described below.

  In the prior art, methods for producing one-dimensional metal nanowires include an anodized aluminum (AAO) method, an electron beam rotation method, a catalyst growth method, a chemical pyrolysis method, and a core-shell growth method. Nanowires manufactured by the AAO method have a small diameter and good uniformity, but the process of the AAO method is complex and not suitable for mass production. For this reason, the AAO method is inconvenient for commercialization. Although the electron beam rotation method and the catalyst growth method can control the growth point of the metal nanowire, similarly, the processes of the electron beam rotation method and the catalyst growth method are complicated, and the cost of the necessary apparatus is high. For this reason, electron beam rotation and catalyst growth are inconvenient for commercialization. Chemical pyrolysis requires general equipment and processes and is therefore easy to commercialize, but metal nanowires produced by chemical pyrolysis have a large diameter and at the same time trace amounts of nanoparticles. Will increase. In other words, the yield of chemical pyrolysis is lower than that of other processes. In the core-shell growth method, carbon nanotubes are treated as a core, and a film on the carbon nanotubes is coated to form a multi-functional composite material. The multi-functional composite material has a large diameter and its uniformity is controlled. Is not easy and therefore the process is complicated and the cost is very high.

  As mentioned above, the chemical pyrolysis method is more suitable for mass production of silver nanowires than other methods, but the problem with this method is the growth of large particles due to the condensation effect, and the high temperature reaction is a batch production Capacity is still not sufficient.

  The scope of the present invention is to provide a mass production method of high-quality silver nanowires for solving the above problems.

According to one embodiment, the method of the present invention can be used to produce silver nanowires and the steps of this method are described below. First, the glycol solution is supplied into the reaction tank and the aging tank, and the glycol solution is preheated in the reaction tank and the aging tank. The silver-salt solution and the protective agent are then fed into the reaction tank by continuous feeding, mixed, and the mixed solution is treated with the reactants in an appropriate temperature range in the reaction tank. After the initial residence time, the solid can be separated from the mixed solution in the reaction tank, and the mixed solution can be fed into the aging tank and subjected to the aging treatment step. After staying for the second residence time in the aging tank, the mixed solution can be taken out and purified to obtain silver nanowires.

  In this embodiment, a silver-salt solution is formed by dissolving silver nitrate in a glycol solution, and a protective agent solution is formed by dissolving polyvinylpyrrolidone (PVP) in the glycol solution.

  Furthermore, the method for purifying the mixed solution for obtaining silver nanowires may further include the following steps. Acetone is mixed with the mixed solution to sufficiently remove glycol for obtaining a precipitate. The precipitate is dissolved in hot water to form a solution, which is subjected to ion exchange. This solution can be repeatedly subjected to solid-liquid separation several times under heating and stirring conditions to obtain a solution having high quality silver nanowires. Moreover, the water in the solution which has silver nanowire can be removed by spray drying, and the powder of silver nanowire can be obtained.

  The advantages and spirit of the invention may be understood by the following detailed description in conjunction with the accompanying drawings.

FIG. 1 is a flowchart illustrating a method for continuously producing silver nanowires according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating purification of a mixed solution for obtaining silver nanowires according to another embodiment of the present invention. FIG. 3 is a schematic diagram illustrating the distribution of yield versus reaction time according to the embodiment in Table 3. FIG. 4 is a schematic diagram illustrating the distribution of diameters of silver nanowires versus the supply concentration of silver salt according to the embodiment in Table 4. FIG. 5 is a SEM diagram illustrating the silver nanowires obtained in the first embodiment.

Refer to Figure 1. FIG. 1 is a flowchart illustrating a method for continuously producing silver nanowires according to an embodiment of the present invention. As shown in FIG. 1, the method in the embodiment includes the following steps: In step S10, the first solution is fed into the reaction tank and the aging tank, and the first solution is heated to a first temperature range; In step S12, the silver-salt solution and the protective agent solution are supplied into the reaction tank, the silver-salt solution and the protective agent solution are mixed with each other within the second temperature range, and the first residence time, residence time Forming a second solution; in step S14, the second solution is fed into the aging tank and the second solution is allowed to stay in the aging tank for a second residence time to form a third solution; In step S16, the third solution is purified to obtain silver nanowires.

  In this embodiment, the first solution may be a glycol solution, but in practice is not limited to a glycol solution. In this embodiment, the silver-salt solution can be formed by dissolving silver nitrate in a glycol solution. However, it can be formed by dissolving a water-soluble silver salt in another solvent, and is not actually limited to silver nitrate and glycol. For example, a silver-salt solution can be formed by dissolving silver acetate or silver nitrate in an organic solvent. Similarly, the protective agent solution can be formed by dissolving polyvinyl pyrrolidone in a glycol solution, but is not limited thereto.

  In step S12, the silver-salt solution and the protective agent solution can be supplied to the reaction tank according to a certain ratio, and the ratio may be equal. Note that the silver-salt solution initiates contact with the protective agent solution in the reaction tank, thus preventing initial contact and reaction at unspecified conditions that may result in the formation of silver nanoparticles or other unexpected effects. Should.

  The silver-salt solution and the protective agent solution can be supplied into the reaction tank by continuous supply. Therefore, the reaction proceeds continuously, and silver nanowires can be mass-produced. For example, the reaction tank may have two different inlets for continuously feeding the silver-salt solution and the protectant solution in equal proportions. The continuous feeding step lowers the temperature of the mixed solution, and therefore, in step S10, preheating is required to ensure that the reaction between the silver-salt solution and the protective agent solution proceeds at the reaction temperature. is there. Without preheating, the reaction proceeds at a low temperature after supply of the silver-salt solution and the protective agent solution, resulting in the production of many nanoparticles.

In the present invention, a protective agent solution is formed by dissolving polyvinylpyrrolidone in a glycol solution. Polyvinylpyrrolidone is a water-soluble polymer compound that can be dissolved in glycol. The molecules of polyvinylpyrrolidone can provide a barrier to limit the growth of silver particles and adapt them to the nanoscale when the silver nanoparticles are separated from the mixed solution of silver-salt solution and protective agent solution. On the other hand, oxygen functional groups on the long chains of polyvinyl pyrrolidone, silver nanoparticles can be grown stably is set along a one-dimensional direction within the reaction tank, Thus during the aging process of the aging tank One-dimensional silver nanowires are formed.

  In order to thoroughly mix the silver-salt solution and the protectant solution, a homogenizer, magnetic mixer or motor mixer may be placed in the reaction tank to assist in mixing. When using a motor mixer, it should be noted that the first solution for preheating (the glycol solution in this embodiment) should be fed into the reaction tank in an amount that can be agitated by the motor blades. .

In this embodiment, the concentration of silver salt in the silver-salt solution may exceed 0.5% by weight. Further, the molecular weight of the polyvinylpyrrolidone in the protective agent solution may be 5000 to 360,000. When supplying the silver-salt solution and the protective agent solution into the reaction tank, the weight ratio of polyvinylpyrrolidone to silver nitrate may be 0.5-6. Furthermore, the second temperature range maintained in the reaction tank may be 140 ° C to 180 ° C, and the first temperature range for preheating may be 170 ° C to 180 ° C. Good. It should be noted that the temperature range of the reaction and aging tanks and the preheating can be supplied by microwave heating, but is not limited thereto.

Since the reaction temperature affects the separation rate of silver nanowires from the mixed solution, the residence time in which the second solution stays in the reaction tank may be in the range of 10 to 30 minutes, but is not limited thereto. . The second residence time during which the second solution stays in the aging tank may be 30 minutes, but is not limited thereto. In fact, under temperature and concentration conditions suitable for the reaction, the first residence time can be reasonably set as a range of 10 minutes to 45 minutes. Also, after supplying the silver-salt solution and the protective agent solution for 30 minutes, a stable state is reached, and for continuous supply, the yield of silver ions to be converted into silver nanoparticles is approximately a stable value in the reaction tank, In practice, the stable value is approximately 90%. After feeding the mixed solution into the aging tank for 30 minutes, the yield can rise to about 100%. Therefore, the residence time in the aging tank can be set reasonably as 30 minutes.

  Refer to Figure 2. FIG. 2 is a flowchart illustrating purification of a mixed solution for obtaining silver nanowires according to another embodiment of the present invention. As shown in FIG. 2, in this embodiment, step S16 in the previous embodiment further includes the following steps: In step S160, excess acetone is supplied to the third solution and the third solution is glycol. In step S162, the transparent liquid part is removed and the precipitated part is dissolved in hot water to form a fourth solution; in step S164, the fourth part is formed. In step S166, the fifth solution is repeatedly heated, stirred, and solid-liquid separated to form a sixth solution; step S166 is used to form a sixth solution; In S168, the sixth solution is spray-dried to remove the water of the sixth solution to obtain silver nanowire powder.

  Polyvinyl pyrrolidone can be mixed with glycol instead of acetone, so in this embodiment, the acetone supplied in step S160 is thoroughly mixed with the glycol of the third solution to produce silver nanowires. And then precipitating polyvinylpyrrolidone packed with silver nanowires, and then the third solution forms a clear liquid part and a precipitate part, where the clear liquid part is formed by dissolving the glycol in acetone. The After settling for a while, a transparent liquid part is removed in step S162. Hot water can dissolve the polyvinylpolypyrrolidone in the precipitated portion, and the hot water can assist in evaporating the remaining acetone in the precipitated portion.

  In this embodiment, the fourth solution is treated by an ion exchange process (as described in step S164) to remove cations and anions to produce a neutral fifth solution. it can. It should be noted that the fifth solution may be cooled before the ion exchange process in step S164. The fifth solution obtained in step S164 is thoroughly mixed, and the high-quality silver nanowires are coated with polyvinylpyrrolidone.

  Indeed, the polyvinylpyridone covering the silver nanowires can be removed so that the silver nanowires can be used directly. The fifth solution may be repeatedly heated and stirred to increase the solubility of polyvinylpyridone in water, and the fifth solution may be solid-liquid separated several times as described in step S166. The polyvinyl pyrrolidone coated with the silver nanowires in the fifth nanowire is removed in the above step to form a sixth solution. Accordingly, the sixth solution has uncoated silver nanowires. Finally, high-quality silver nanowire powder can be obtained by removing the water in the sixth solution in step S168.

  Further, in the continuous method for producing silver nanowires of the present invention, the molecular weight of the polymer compound in the protective agent solution, the weight ratio of the polymer compound to silver nitrate, the reaction temperature, and the supply concentration of the silver-salt solution and the protective agent solution Affects the yield and quality of the resulting silver nanowires.

Refer to Table 1. Table 1 shows the appearance of silver nanowires affected by polyvinylpyrrolidone having various molecular weights in the following embodiments. Embodiment 1 in Table 1 shows that a silver-salt solution (silver concentration is 1.66 wt%) formed by dissolving 20 g of silver nitrate in 1200 g of glycol solution and 80 g of polyvinylpyrrolidone in 1200 g of glycol solution. It should be noted that the protective agent solution formed by dissolving is supplied. The reaction tank and the aging tank are each supplied with 100 g of glycol solution. The glycol solution is preheated to 170 ° C, and the reaction tank and aging tank are maintained at 150 ° C during the reaction. The mixed solution stays in the reaction tank for 30 minutes and stays in the aging tank for 30 minutes. Finally, the mixed solution is taken out from the aging tank and then purified to obtain silver nanowires. Embodiments 2 and 3 in Table 1 are the same as those in Embodiment 1 in Table 1 except for the amount of polyvinylpyrrolidone separated.

Table 1 shows the appearance of silver nanowires affected by pyrrolidone having various molecular weights.

  As shown in Table 1, higher molecular weight polyvinylpyrrolidone results in longer and thicker silver nanowires.

  Refer to Table 2. Table 2 shows the appearance of silver nanowires affected by various weight ratios of polyvinylpyrrolidone to silver nitrate in the following embodiments. The conditions of Embodiment 1 in Table 2 are the same as the conditions of Embodiment 1 in Table 1. The conditions of Embodiments 4, 5 and 6 are the same as those of Embodiment 1 in Table 2, except for the various weights of polyvinylpyrrolidone used to dissolve in 1200 g of glycol solution to form a protectant solution. The same.

Table 2 is the appearance of silver nanowires affected by various weight ratios of polyvinylpyrrolidone to silver nitrate.

  As shown in Table 2, the high weight ratio of polyvinylpyrrolidone to silver nitrate results in the formation of silver nanoparticles, which are detrimental to silver nanowires. Conversely, a lower weight ratio results in longer and thicker silver nanoparticles.

  Refer to Table 3. Table 3 shows the appearance of silver nanowires affected by various reaction temperatures in the following embodiments. The conditions of Embodiment 1 in Table 3 are the same as the conditions of Embodiment 1 in Table 1. Embodiments 7, 8 and 9 are the same as those of embodiment 1 in Table 3 except for the various reaction temperatures.

Table 3 shows the appearance of silver nanowires affected by various reaction temperatures.

  As shown in Table 3, under reaction temperature conditions lower than 150 ° C., silver nanoparticles are generated, and nanowires are not generated. Conversely, high reaction temperatures result in longer and thicker silver nanowires.

  Refer to Figure 3. FIG. 3 is a schematic diagram illustrating the distribution of yield X versus reaction time T according to the embodiment in Table 3. As shown in FIG. 3, curves 20, 22, 24, and 26 represent the distribution of yield versus reaction time according to embodiments 1, 7, 8, and 9, respectively. When reaction temperature is lower than 150 degreeC, reaction rate is very low, only a silver nanoparticle precipitates and silver nanowire does not precipitate. On the contrary, when the reaction temperature is higher than 150 ° C., a large amount of silver nanowires are deposited in 30 minutes. Therefore, the residence time in which the mixed solution stays in the reaction tank can be set reasonably as 30 minutes.

  Refer to Table 4. Table 4 shows the appearance of silver nanowires that are affected by various supply concentrations in the following embodiments. The conditions of Embodiment 1 in Table 4 are the same as the conditions of Embodiment 1 in Table 1. Embodiments 10, 11, 12, 13 and 14 are the same as those of embodiment 1 in Table 4 except for the various weights of silver nitrate and polyvinylpyrrolidone.

Table 4 is the appearance of silver nanowires affected by various supply concentrations.

  As shown in Table 4, the feed concentration has a non-linear direct proportional relationship with the diameter of the silver nanowires, in other words, a higher feed concentration results in a larger diameter. The length of the silver nanowire does not change clearly. It should be noted that in embodiment 10, only insufficient silver ions are obtained, and no silver nanowires are obtained, because insufficient concentrations of silver ions reduce the likelihood of collision.

  Please refer to FIG. FIG. 4 is a schematic diagram illustrating the distribution of the diameter D of silver nanowires relative to the supply concentration C of silver salt according to the embodiment in Table 4. As shown in FIG. 4, the supply concentration C (% by weight) of the silver salt has a non-linear proportional relationship with the diameter D (nm) of the silver nanowires.

  See also Figure 5. FIG. 5 is a SEM diagram showing the silver nanowire obtained in the first embodiment. As shown in FIG. 5, the diameter of the silver nanowire obtained in Embodiment 1 is about 80 nm to 100 nm.

Compared with the prior art, the continuous method for producing silver nanowires of the present invention provides a water-soluble silver-salt solution for obtaining silver nanoparticles at an appropriate temperature, and at the same time limits the growth of silver nanoparticles. Mix the protective agent solution to supply the barrier. On the other hand, the functional group in the protective agent solution can stably maintain the one-dimensional growth of silver nanoparticles and can form silver nanowires during the aging process. The method of the present invention utilizes a continuous supply for mass production of silver nanowires.

  The features and spirit of the present invention have been fully described, if possible, using the examples and description. Those skilled in the art will readily observe that many modifications and variations of the device can be made while retaining the teachings of the present invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.

Claims (15)

The following process:
Supplying the first solution into the reaction tank and the aging tank, and heating the first solution to the first temperature range in the reaction tank and the aging tank;
A silver-salt solution and a protective agent solution are continuously fed into the reaction tank according to a certain ratio, and the silver-salt solution and the protective agent solution are mixed with each other in a second temperature range, and a first residence time Dwelling in the reaction tank to form a second solution;
Supplying the second solution into the aging tank, and retaining the second solution in the aging tank for a second residence time to form a third solution; and the third solution; A method for continuously producing silver nanowires, comprising the step of purifying the above to obtain at least one silver nanowire;
The silver-salt solution is produced by dissolving a water-soluble silver salt in a first solvent;
The water-soluble silver salt is silver nitrate;
The protective agent solution is produced by dissolving polyvinylpyrrolidone in a second solvent;
The first solvent and the second solvent are glycol;
During the aging process in the aging tank, the molecules of polyvinyl pyrrolidone can limit the growth of silver particles to nanoscale as the silver nanoparticles are separated from the silver-salt solution and the protective solution. Provide a barrier to adapt, the oxygen functional group on the long chain of polyvinylpyrrolidone aggregates silver nanoparticles along the one-dimensional direction in the reaction tank and grows stably, forming a one-dimensional silver nanowire A method characterized in that.   The method of claim 1, wherein the first solution is a glycol solution.   The process according to claim 1, wherein the concentration of water-soluble silver salt in the silver-salt solution is higher than 0.5% by weight. The method of claim 1, wherein the step of purifying the third solution comprises the following steps.
Supplying excess acetone to the third solution and mixing the third solution with the glycol to form a clear liquid portion and a precipitated portion;
Removing the transparent liquid portion and dissolving the precipitate portion in hot water to form a fourth solution;
Treating the fourth solution by an ion exchange treatment to form a fifth solution;
The fifth solution is repeatedly heated, stirred and solid-liquid separated to obtain a sixth solution; and the sixth solution is spray-dried to remove the water of the sixth solution; Obtaining at least one nanowire powder; The method of claim 4 , wherein the volume ratio of the acetone to the third solution is in the range of 2-6.   The method according to claim 1, wherein when the silver-salt solution and the protective agent solution are supplied into the reaction tank, a weight ratio of the polyvinylpyrrolidone to the silver nitrate is in a range of 0.5-6.   The method according to claim 1, wherein the protective agent solution has a molecular weight of polyvinylpyrrolidone in the range of 5000 to 360,000.   The method according to claim 1, wherein the silver-salt solution and the protective agent solution are fed into the reaction tank by continuous feeding.   The method of claim 1, wherein the first temperature range is within a range of 170 ° C. to 180 ° C.   The method of claim 1, wherein the second temperature range is within a range of 140C to 180C.   The method of claim 10, wherein the second temperature range is in the range of 150 ° C. to 170 ° C.   The method of claim 1, wherein the first residence time is in the range of 10 minutes to 30 minutes.   The method of claim 1, wherein the second residence time is 30 minutes.   The method of claim 1, wherein the first temperature range is provided by microwave heating.   The method of claim 1, wherein the second temperature range is provided by microwave heating.

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