TWI842351B - Method for producing silver nanoparticles - Google Patents

Abstract

The present invention relates to a method for producing silver nanoparticles. Silver nuclei are produced by an electrochemical reaction in an electrolyte with a high concentration of a size-controlling agent in the method for producing the silver nanoparticles. Then, a portion of the size-controlling agent is removed from the electrolyte, such that the silver nuclei grow in a crystal growth solution with a low concentration of the size-controlling agent. As a crystallizing time is increased, an initial particle size of the silver nuclei is increased, so as to form the silver nanoparticles. At a specific crystallizing time, a portion taken from the crystal growth solution can obtain the silver nanoparticles with a specific average particle size, thereby simplifying the process and saving time.

Description

Method for producing silver nanoparticles

The present invention relates to a method for producing silver nanoparticles, and in particular to a method for producing silver nanoparticles with different average particle sizes from the same crystal growth solution.

In the known method of manufacturing silver nanoparticles, the process includes applying a current to a single electrolyte to generate a plurality of silver nuclei through an electrochemical reaction. Then, after stopping the application of the current, after a fixed growth time, these silver nuclei grow into silver nanoparticles with a specific average particle size.

As mentioned above, the conventional process of making silver nanoparticles can only produce silver nanoparticles with a specific average particle size from a single electrolyte. If you want to obtain silver nanoparticles with multiple average particle sizes, you need to perform multiple processes. Furthermore, the conventional process of making silver nanoparticles still requires the use of different reagents and different process conditions to obtain silver nanoparticles with corresponding average particle sizes, which greatly increases the manufacturing cost and wastes time. In view of this, it is urgent to develop a new method for making silver nanoparticles to improve the above shortcomings.

In view of the above problems, one aspect of the present invention is to provide a method for manufacturing silver nanoparticles. In this manufacturing method, a portion of the same crystal growth solution is taken out at a specific crystal growth time to obtain silver nanoparticles with a specific average particle size, thereby simplifying the process and saving time.

According to one aspect of the present invention, a method for manufacturing silver nanoparticles is provided. In the method for manufacturing silver nanoparticles, an electrochemical reaction system is first provided, wherein the electrochemical reaction system includes a silver electrode as a positive electrode, an opposite electrode as a negative electrode, an electrolyte, and a power supply element. The electrolyte contacts one end of the silver electrode and one end of the opposite electrode, and the electrolyte includes a particle size control reagent, and the concentration of the particle size control reagent is 0.08M to 0.12M. The power supply element is electrically connected to the other end of the silver electrode and the other end of the opposite electrode, respectively. Then, an electrochemical reaction is performed on the electrochemical reaction system, wherein a constant current is applied to the silver electrode and the counter electrode to electrolyze the silver electrode into a plurality of silver ions, and these silver ions generate a plurality of silver nuclei after receiving electrons from the counter electrode. Subsequently, the application of the constant current is stopped, and a portion of the particle size control reagent in the electrolyte is removed until the concentration is reduced to ^3x10-8 M to ^5x10-8 M, so as to obtain a crystal growth solution. Afterwards, a crystal growth step is performed on these silver nuclei to obtain these silver nanoparticles, wherein the initial particle size of these silver nuclei increases with the crystal growth time, and a portion of the electrolyte is taken out at different crystal growth times to obtain these silver nanoparticles with a specific average particle size, and the distribution range of the average particle size is 25 nanometers to 150 nanometers.

According to one embodiment of the present invention, the electrolyte further comprises acetone.

According to another embodiment of the present invention, the particle size control reagent comprises sodium dodecyl sulfate.

According to another embodiment of the present invention, the set current is 90 mA to 110 mA.

According to another embodiment of the present invention, the reaction time of the electrochemical reaction is 20 seconds to 1 minute.

According to another embodiment of the present invention, the reaction temperature of the electrochemical reaction is 28°C to 32°C.

According to another embodiment of the present invention, the electrolyte is disturbed during the electrochemical reaction.

According to another embodiment of the present invention, in an electrochemical reaction, these silver nuclei are generated inside a plurality of micelles formed by a particle size control reagent.

According to another embodiment of the present invention, in the crystal growth step, the initial grain size increases according to the following equation (1).

d = a + b × t (1)

In equation (1), a represents a constant, d represents the initial particle size (nanometers), t represents the crystal growth time (hours), and when the crystal growth time is shorter than 8.3 hours, a is 27 to 28 and b is 10 to 10.5 (nanometers/hour), or when the crystal growth time is between 8.3 hours and 98.5 hours, a is 106 to 107 and b is 0.4 to 0.45 (nanometers/hour).

According to another embodiment of the present invention, after the crystal growth step, the method for manufacturing silver nanoparticles further includes a termination step, by increasing the concentration of the particle size control reagent in these solutions to greater than 0.15M to stop the crystal growth step.

The manufacturing method of silver nanoparticles of the present invention is applied, wherein silver nuclei are generated by electrochemical reaction in an electrolyte containing a high concentration of a particle size control reagent. Then, a portion of the particle size control reagent is removed from the electrolyte so that the silver nuclei grow into silver nanoparticles in a crystal growth solution containing a low concentration of a particle size control reagent. Silver nanoparticles with a specific average particle size can be obtained by taking out a portion from the same crystal growth solution at a specific crystal growth time, thereby simplifying the process and saving time.

100:Methods

110,120,130,140: Operation

In order to have a more complete understanding of the embodiments of the present invention and its advantages, please refer to the following description and the corresponding drawings. It must be emphasized that the various features are not drawn to scale and are only for illustration purposes. The contents of the relevant drawings are described as follows: Figure 1 is a flow chart of a method for manufacturing silver nanoparticles according to an embodiment of the present invention.

Figure 2 shows how the initial grain size of the silver nuclei of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention increases with the increase of crystal growth time.

The manufacture and use of embodiments of the present invention are discussed in detail below. However, it is understood that the embodiments provide many applicable inventive concepts that can be implemented in a variety of specific contexts. The specific embodiments discussed are for illustration only and are not intended to limit the scope of the present invention.

Please refer to FIG. 1 . In the method 100 for manufacturing silver nanoparticles, an electrochemical reaction system is provided, as shown in operation 110. The electrochemical reaction system includes a silver electrode, a counter electrode, an electrolyte, and a power supply element. The aforementioned silver electrode and the counter electrode serve as a positive electrode and a negative electrode, respectively. The counter electrode may be a conductive material, and its specific examples may include but are not limited to platinum, graphite, or other metal materials.

The electrolyte contacts one end of the silver electrode and one end of the opposite electrode, and the power supply element is electrically connected to the other end of the silver electrode and the other end of the opposite electrode, respectively. In detail, the electrolyte contains a particle size control reagent, such as sodium dodecyl sulfate. In some specific examples, the concentration of the particle size control reagent is 0.08M to 0.12M, and preferably 0.09M to 0.11M. If the concentration of the particle size control reagent is lower than 0.08M, the particle size control reagent is difficult to form micelles, so the silver nuclei generated in the electrochemical reaction described later are easy to aggregate, and the average particle size of the obtained silver nanoparticles cannot be controlled. On the contrary, if the concentration of the particle size control reagent is higher than 0.12M, most of the micelles formed by the particle size control reagent will not contain the silver ions generated by the electrolytic silver electrode described later, so silver nuclei cannot be generated, or the particle size control reagent in the subsequent removal step of the electrolyte needs to be removed multiple times, which may remove the silver atoms and/or silver nuclei in the electrolyte and affect the subsequent crystal growth step, so that the average particle size of the obtained silver nanoparticles is not within the expected range.

In some embodiments, the electrolyte may optionally contain acetone, which can help disperse the micelles more evenly in the electrolyte to facilitate the generation of silver nuclei.

After operation 110, the electrochemical reaction system is subjected to an electrochemical reaction, as shown in operation 120. Specifically, a constant current is applied to the silver electrode and the opposite electrode to electrolyze the silver electrode into a plurality of silver ions, and these silver ions receive electrons from the opposite electrode to generate a plurality of silver nuclei. These silver nuclei can be formed inside a plurality of microcells formed by the particle size control reagent, so that these silver nuclei are uniformly dispersed in the electrolyte, thereby facilitating the subsequent production of silver nanoparticles with different average particle sizes by crystal growth time. It should be noted that, as can be understood by those with ordinary knowledge in the technical field to which the present invention belongs, these silver ions can generate a plurality of silver nuclei or a plurality of silver atoms after receiving electrons from the opposite electrode.

In some embodiments, a constant current of 90 mA to 110 mA can be applied. A constant current within this range can be more conducive to controlling the number of silver nuclei generated. When the number of silver nuclei is controlled, the growth rate of the subsequent crystal growth step can be more stable, thereby making it easier to control the average particle size of the produced silver nanoparticles.

In some specific examples, the reaction time of the electrochemical reaction is 20 seconds to 1 minute, and preferably 25 seconds to 40 seconds, so as to facilitate the generation of silver nuclei, and thus to facilitate the control of the average particle size of the produced silver nanoparticles. In addition, preferably, in the electrochemical reaction, the reaction temperature can be controlled at 28°C to 32°C. The temperature within this range can make the micelles more evenly distributed and more stably present in the electrolyte, which is conducive to the nuclear control reagent coating the silver nuclei and making their size more uniform, thereby making it easier to control the average particle size of the produced silver nanoparticles.

In a preferred embodiment, during the electrochemical reaction, the electrolyte can be selectively disturbed to evenly disperse the silver nuclei in the micelles. The aforementioned method of disturbing the electrolyte may include but is not limited to blade stirring or ultrasonic vibration, among which ultrasonic vibration is preferred. For example, ultrasonic vibration can produce a large number of cavitation explosions in the electrolyte, so that the silver ions and micelles are quickly and evenly distributed in the electrolyte, thereby helping the generation of silver nuclei.

After operation 120, the application of the constant current is stopped, and a portion of the particle size control reagent in the electrolyte is removed until the concentration of the particle size control reagent is reduced to ^3x10-8 M to ^5x10-8 M to obtain a crystal growth solution, as shown in operation 130. In detail, after the silver nuclei are generated, the application of the constant current is stopped to prevent the silver nuclei from over-growing into unwanted large silver particles (such as an average particle size greater than 10nm). Then, a portion of the particle size control reagent in the electrolyte is removed by a method such as centrifugation. Specifically, the rotation speed of the centrifugation can be 16000rpm to 20000rpm, and the centrifugation time can be 20 minutes.

In the aforementioned removal operation 130, the concentration of the particle size control reagent is reduced to ^3x10-8 M to ^5x10-8 M. If the concentration is lower than ^3x10-8 M or higher than ^5x10-8 M, it is difficult to obtain silver nanoparticles of a specific average particle size from the same crystal growth solution by taking out a portion at a specific crystal growth time, wherein the aforementioned average particle size distribution ranges from 25 nm to 150 nm.

After operation 130, a crystal growth step is performed on these silver nuclei to obtain these silver nanoparticles, as shown in operation 140. In the crystal growth step, the initial particle size of these silver nuclei increases as the crystal growth time increases. For example, crystal growth can be achieved by the following aspects: (1) multiple silver nuclei aggregate, (2) multiple silver atoms attach to one silver nucleus, (3) multiple silver atoms attach to one silver nucleus and this silver nucleus aggregates with other silver nuclei. For simplicity, the above aspects are generally described as "silver nucleus crystal growth". By taking out a portion of the crystal growth solution at a specific crystal growth time from the same crystal growth solution, silver nanoparticles with a specific average particle size can be obtained, and the distribution range of the above-mentioned average particle size is 25 nanometers to 150 nanometers. Therefore, the method 100 for manufacturing silver nanoparticles can produce silver nanoparticles with a variety of average particle sizes in the same crystal growth solution by different crystal growth times. In other words, compared with the known method for manufacturing silver nanoparticles, the method 100 for manufacturing silver nanoparticles of the present invention can use the same manufacturing system (i.e., electrochemical reaction system) and the same reagent (such as particle size control reagent) to generate silver nuclei, and then take out the electrolyte at different crystal growth times to obtain silver nanoparticles with a variety of average particle sizes, thereby simplifying the process and saving time.

For example, the initial particle size of these silver nuclei can be enlarged according to the following equation (1) to form silver nanoparticles.

d = a + b × t (1)

In equation (1), d represents the initial particle size of the silver nuclei (nanometers), and t represents the crystal growth time (hours).

In some embodiments, when the crystal growth time is shorter than 8.3 hours, the constant represented by a is 27 to 28, and b is 10 to 10.5 (nm/hour). In other embodiments, when the crystal growth time is between 8.3 hours and 98.5 hours, the constant represented by a is 106 to 107, and b is 0.4 to 0.45 (nm/hour). Therefore, according to the above equation (1), silver nanoparticles with a variety of average particle sizes can be obtained by adjusting the crystal growth time. Preferably, the average particle size distribution ranges from 28 nm to 144 nm.

After operation 140, the method 100 for manufacturing silver nanoparticles may optionally include a termination step, by increasing the concentration of the particle size control reagent in these solutions to greater than 0.15M to stop the crystal growth step of the silver nuclei. Specifically, when the concentration of the particle size control reagent is higher than 0.15M, the surface of the silver nuclei (hereinafter referred to as silver particles) grown in the aforementioned crystal growth step is tightly surrounded by the particle size control reagent, so the particle size control reagent separates the adjacent silver particles and prevents them from continuing to grow and increase, so as to facilitate the control of the average particle size of the obtained silver nanoparticles.

The following examples are used to illustrate the application of the present invention, but they are not used to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention.

Production of silver nanoparticles

Example 1

First, an electrochemical reaction system is provided, which includes a silver electrode, a counter electrode, an electrolyte and a power supply element. The electrolyte includes water, acetone and sodium dodecyl sulfate, wherein the concentration of sodium dodecyl sulfate is 0.1M. Then, ultrasonic vibration (power of 120W and frequency of 37kHz) is applied to the electrolyte, and the electrochemical reaction system is subjected to an electrochemical reaction at a constant current of 100 mA at 30°C for a reaction time of 30 seconds. Subsequently, the application of the constant current is stopped. Thereafter, the particle size control reagent is removed from the electrolyte to reduce its concentration to ^3.9x10-8M . Next, multiple solutions were taken out from the electrolyte according to the crystal growth time listed in Table 1 below, and sodium dodecyl sulfate was added to increase its concentration to 0.2M, thereby stopping the silver nuclei from continuing to grow. Afterwards, the silver nuclei after crystal growth were separated from the electrolyte by centrifugation to obtain silver nanoparticles with different average particle sizes.

Comparison Examples 1 and 2

The silver nanoparticles of Comparative Examples 1 and 2 were prepared in the same manner as Example 1. The difference was that in the removal operation, the concentration of sodium dodecyl sulfate was reduced to 1.6x10 ^-6 M and 9.8x10 ^-10 M in Comparative Examples 1 and 2, respectively. The specific conditions and evaluation results of the aforementioned Example 1 and Comparative Examples 1 to 2 are shown in Table 1 and FIG. 2 below.

Please refer to Table 1 and Figure 2. Figure 2 shows that the initial grain size of the silver nuclei in Example 1 and Comparative Examples 1 to 2 increases with the increase of the crystal growth time. In Example 1, linear regression analysis was performed on the crystal growth time from 0 hours to 8.3 hours and from 8.3 hours to 96 hours and the corresponding initial grain size to obtain the equations of the regression lines in the above two time periods, which are shown in the following equations (1-1) and (1-2) respectively.

d=27.43+10.25×t (1-1)

d=106.87+0.42×t (1-2)

In the above equations (1-1) and (1-2), d represents the average particle size of silver nuclei (nanometers), and t represents the crystal growth time (hours).

In the removal step, Example 1 reduces the concentration of sodium dodecyl sulfate to 3.9x10 ^-8 M (i.e., an appropriate concentration), so the average particle size distribution range of the silver nanoparticles produced in the same crystal growth solution can be from 28 nm to 147 nm. In addition, referring to the above equations (1-1) and (1-2), in the next process, the crystal growth solution can be taken out at the crystal growth time corresponding to the desired average particle size, thereby obtaining silver nanoparticles with the desired average particle size.

However, referring to FIG. 2 , in the removal step, the sodium dodecyl sulfate concentration is reduced to 1.6x10 ^-6 M in Comparative Example 1, so only silver nanoparticles with a narrower average particle size distribution range can be produced in the same crystal growth solution. In addition, the sodium dodecyl sulfate concentration is reduced to 9.8x10 ^-10 M (i.e., too low a concentration) in Comparative Example 2, and due to the multiple removals of sodium dodecyl sulfate, part of the silver nuclei and/or silver atoms in the electrolyte are removed during the process, so that sufficient silver nuclei and/or silver atoms cannot be provided in the entire crystal growth process, so only silver nanoparticles with a narrower average particle size distribution range can be produced in the same crystal growth solution. In addition, because the concentration of sodium dodecyl sulfate was too low, there were not enough micelles for stable crystal growth. Some silver nuclei were not surrounded by sodium dodecyl sulfate and aggregated into oversized particles and precipitated directly and quickly. Therefore, when measuring the average particle size, the precipitated large particles were not measured.

In summary, the method for manufacturing silver nanoparticles of the present invention utilizes electrochemical reaction to generate silver nuclei in an electrolyte solution with a high concentration of particle size control reagent. A portion of the particle size control reagent is then removed from the electrolyte solution, so that the silver nuclei grow into silver nanoparticles in an electrolyte solution with a low concentration of particle size control reagent. A portion of the solution taken out from the same crystal growth solution at a specific crystal growth time can obtain silver nanoparticles with a specific average particle size, and the average particle size distribution range of the silver nanoparticles is 25 nanometers to 150 nanometers, thereby simplifying the process and saving time.

Although the present invention has been disclosed in the form of implementation as above, it is not intended to limit the present invention. Anyone with common knowledge in the technical field to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of the patent application attached hereto.

100:Methods

110,120,130,140: Operation

Claims (10)

A method for manufacturing silver nanoparticles comprises: providing an electrochemical reaction system, comprising: a silver electrode, serving as a positive electrode; an opposite electrode, serving as a negative electrode; an electrolyte, contacting one end of the silver electrode and one end of the opposite electrode, wherein the electrolyte comprises a particle size control reagent, and a concentration of the particle size control reagent is 0.08M to 0.12M; and a power supply element, electrically connected to the silver electrode and the opposite electrode, respectively. The electrochemical reaction system is provided with a silver electrode and a counter electrode; an electrochemical reaction is performed on the silver electrode and the counter electrode, wherein a certain current is applied to the silver electrode and the counter electrode to electrolyze the silver electrode into a plurality of silver ions, and the silver ions generate a plurality of silver nuclei after receiving electrons from the counter electrode; the application of the certain current is stopped, and a portion of the particle size control reagent in the electrolyte is removed until the concentration is reduced to 3x10 ^-8 M to 5x10 ^-8 M to obtain a crystal growth solution; and performing a crystal growth step on the silver nuclei to obtain the silver nanoparticles, wherein an initial particle size of the silver nuclei increases with an increase in a crystal growth time to form the silver nanoparticles, and from the same crystal growth solution, a portion of the crystal growth solution is taken out at the specific crystal growth time to obtain the silver nanoparticles having a specific average particle size, and a distribution range of the average particle size is 25 nanometers to 150 nanometers. The method for manufacturing silver nanoparticles as described in claim 1, wherein the electrolyte further comprises acetone. A method for producing silver nanoparticles as described in claim 1, wherein the particle size control reagent contains sodium dodecyl sulfate. The method for manufacturing silver nanoparticles as described in claim 1, wherein the constant current is 90 mA to 110 mA. The method for manufacturing silver nanoparticles as described in claim 1, wherein a reaction time of the electrochemical reaction is 20 seconds to 1 minute. The method for manufacturing silver nanoparticles as described in claim 1, wherein a reaction temperature of the electrochemical reaction is 28°C to 32°C. A method for manufacturing silver nanoparticles as described in claim 1, wherein the electrolyte is disturbed during the electrochemical reaction. The method for producing silver nanoparticles as described in claim 1, wherein in the electrochemical reaction, the silver nuclei are generated inside a plurality of micelles formed by the particle size control reagent. A method for manufacturing silver nanoparticles as described in claim 1, wherein in the crystal growth step, the initial particle size increases according to equation (1): d = a + b × t (1), in which a represents a constant, d represents the initial particle size (nanometers), t represents the crystal growth time (hours), and when the crystal growth time is shorter than 8.3 hours, a is 27 to 28, and b is 10 to 10.5 (nanometers/hour), or when the crystal growth time is between 8.3 hours and 98.5 hours, a is 106 to 107, and b is 0.4 to 0.45 (nanometers/hour). The method for producing silver nanoparticles as described in claim 1, wherein after the crystal growth step, the method for producing silver nanoparticles further comprises a termination step, by increasing the concentration of the particle size control reagent in the solutions to greater than 0.15M to stop the crystal growth step.

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