A characterization method and monitoring method for in-situ growth process of silver nanowires and its application in controllable preparation of silver nanowires

Abstract

The present invention belongs to the technical field of nanomaterials, and specifically relates to a characterization method and a monitoring method for the in-situ growth process of a silver nanowire, and an application thereof in the controllable preparation of the silver nanowire. The characterization method comprises the following steps: (1) establishing a silver nanowire reaction system; (2) monitoring the conductivity of the reaction system in real time, and collecting conductivity data; (3) repeating steps (1)-(2), summarizing the conductivity change law during the in-situ growth process of the silver nanowire, establishing a conductivity change trend model, and characterizing the in-situ growth process of the silver nanowire. The present invention characterizes the in-situ growth process of the silver nanowire by establishing a conductivity change trend model. The characterization method can monitor the conductivity of the silver nanowire reaction process in real time, and then perform real-time online characterization of the reaction process. The operation is simple and fast, the result is accurate, and the method is applicable to a conventional silver nanowire preparation system, and the method has good application value.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to a characterization method and a monitoring method for an in-situ growth process of a silver nanowire and an application of the method in the controllable preparation of the silver nanowire. Background Art

[0002] Nanomaterials are a new generation of materials at the nanoscale, composed of nanoparticles with a size between 1-100nm, showing unique physical and chemical properties such as light, electricity, magnetism, heat, mechanics, and mechanics. This has enabled nanotechnology to quickly penetrate into various research fields, attracting the attention of many physicists, chemists, and material scientists at home and abroad, and becoming the hottest scientific research hotspot in the world. Obtaining information on the growth process of nanomaterials, clarifying the thermodynamics, kinetics, and growth mechanism of the growth process of nanomaterials, summarizing the characteristics and laws of nanomaterial growth, and giving a scientific and reasonable explanation, so as to achieve the controllable growth of nanomaterials and then achieve the regulation of structure and physical properties, has always been the goal of nanomaterial preparation science.

[0003] In recent years, silver nanowires have been widely used in energy, catalysis, biology, electronics and other fields due to their unique mechanical, electrical, thermal and optical properties. Monitoring the growth process of silver nanowires is of great significance for the controllable preparation of silver nanowires.

[0004] The existing monitoring method of the growth process of silver nanowires is mainly to observe the growth process of metal nanocrystals by sampling at different times and then characterizing them through an electron microscope (SEM or TEM). This method has the following defects: on the one hand, it is impossible to achieve real-time online monitoring, that is, it belongs to offline detection, and the sampling time needs to be strictly controlled. In addition, due to the interval between sampling times, it is impossible to display the information of the entire growth process of the silver nanowires, that is, it is impossible to describe the instantaneous dynamic and fine information of the growth process of the silver nanowires; on the other hand, this method cannot monitor the physical quantities related to the growth process of the silver nanowires, and therefore cannot provide accurate thermodynamic and kinetic information. Therefore, it is crucial to provide a simple, real-time, in-situ method for characterizing and monitoring the growth process of silver nanowires. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a characterization method and a monitoring method for the in-situ growth process of silver nanowires and their application in the controllable preparation of silver nanowires, which achieves the purpose of monitoring the growth process of silver nanowires by monitoring the changes in the conductivity of the reaction system.

[0006] In a first aspect, the present invention provides a method for characterizing an in-situ growth process of silver nanowires, comprising the following steps:

[0007] (1) Establishing a silver nanowire reaction system;

[0008] (2) real-time monitoring of the conductivity of the reaction system and collection of conductivity data;

[0009] (3) Repeat steps (1)-(2) to summarize the conductivity change law during the in situ growth of silver nanowires, establish a conductivity change trend model, and characterize the in situ growth process of silver nanowires.

[0010] Furthermore, the method for characterizing the in-situ growth process of silver nanowires further comprises the following steps:

[0011] The reaction liquid at different stages of the reaction system was sampled and processed, and electron microscopy was performed to obtain electron microscopy images. Finally, the in-situ growth process of silver nanowires was analyzed based on the conductivity change trend model combined with the electron microscopy images.

[0012] Furthermore, the characterization method of the in-situ growth process of the silver nanowires specifically comprises the following steps:

[0013] (1) dissolving a silver salt in a polyol to obtain a first reaction solution;

[0014] (2) dissolving polyvinyl pyrrolidone and a soluble halide salt in a polyol to obtain a second reaction solution;

[0015] (3) placing the second reaction solution in a flask and connecting it to an online conductivity tester;

[0016] (4) heating the second reaction liquid, maintaining a constant temperature after reaching the target temperature, starting an online conductivity tester, and collecting conductivity data;

[0017] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate to react, and observing the change in the conductivity of the system;

[0018] (6) The reaction is terminated after the reaction solution is added dropwise and the system conductivity remains constant;

[0019] (7) Repeat steps (1)-(6) to summarize the conductivity change law during the in situ growth of silver nanowires, establish a conductivity change trend model, characterize the in situ growth process of silver nanowires, and analyze the in situ growth process of silver nanowires based on the conductivity change trend model combined with the electron microscopy image.

[0020] Specifically, in step (5), the initial time is when the first reaction liquid is added to the second reaction liquid, timing is started and the change in system conductivity is measured, and the conductivity data for at least 80 consecutive minutes is used as the conductivity change data for the entire in-situ growth process of silver nanowires.

[0021] Furthermore, the characterization method of the in-situ growth process of the silver nanowires specifically comprises the following steps:

[0022] (1) dissolving a silver salt in a polyol to obtain a first reaction solution;

[0023] (2) dissolving polyvinyl pyrrolidone and a soluble halide salt in a polyol to obtain a second reaction solution;

[0024] (3) placing the second reaction solution in a flask and connecting it to an online conductivity tester;

[0025] (4) heating the second reaction liquid, maintaining a constant temperature after reaching the target temperature, starting an online conductivity tester, and collecting conductivity data;

[0026] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate to react, and observing the change in the conductivity of the system;

[0027] (6) Sampling and processing the reaction solution at different stages of the reaction system, and performing electron microscopy characterization to obtain electron microscopy images;

[0028] (7) The reaction is terminated after the reaction solution is added dropwise and the system conductivity remains constant;

[0029] (8) Repeat steps (1)-(7) to summarize the conductivity change law during the in situ growth of silver nanowires, establish a conductivity change trend model, characterize the in situ growth process of silver nanowires, and analyze the in situ growth process of silver nanowires based on the conductivity change trend model combined with the electron microscopy image.

[0030] Specifically, in step (5), the initial time is when the first reaction liquid is added to the second reaction liquid, timing is started and the change in system conductivity is measured, and the conductivity data for at least 80 consecutive minutes is used as the conductivity change data for the entire in-situ growth process of silver nanowires.

[0031] Conductivity is a digital representation of the ability of a solution to conduct electric current. It is often used to indirectly infer the total concentration of charged substances in a solution. The conductivity of a solution is directly related to the temperature, the degree of doping, and the anisotropy of the substance. The degree of doping of a solution mainly refers to the concentration of electrolytes in the solution, that is, the concentration of charged ions in the solution. When other conditions remain unchanged, the greater the ion concentration, the higher the conductivity of the solution.

[0032] The inventors have found that the conductivity of the system changes in a certain regular pattern during the preparation of silver nanowires: it usually includes six stages. In the first stage, at the initial stage of the reaction, as the reaction solution is mixed, silver ions combine with chloride ions to form silver chloride precipitates. At this time, the anions in the silver salt replace the chloride ions to maintain the constant ion concentration in the system, and the system conductivity remains stable; in the second stage, as the reaction proceeds, a small amount of chloride ions are combined, and the system increases due to the increase of silver ions and silver salt anions, thereby increasing the ion concentration and thus increasing the system conductivity. Since the volume of the first reaction solution is smaller than that of the second reaction solution and the first reaction solution is added dropwise into the second reaction solution, it can be considered that the overall volume of the system remains unchanged. Therefore, the ion concentration in the second stage increases linearly, resulting in a linear increase in the system conductivity; in the third stage, as the first reaction solution continues to be added dropwise, the system ion concentration continues to increase, but since the silver ions begin to be reduced to silver atoms, , at this time, the increase in the system ion concentration decreases, and the increase in the system conductivity decreases; in the fourth stage, since the reaction solution has been mixed, the number of ions no longer increases. As the reaction proceeds, the silver ions continue to be reduced to silver atoms to form silver nuclei, and the formed silver nuclei begin to grow anisotropically to form short rods under the action of the structure-directing agent PVP. The decrease in silver ion concentration leads to a decrease in the system ion concentration, and the conductivity begins to decrease; in the fifth stage, as the reaction proceeds, due to the self-catalytic effect of silver, the nucleation rate increases, and the short rods further grow into silver nanowires. At this time, the system ion concentration decreases faster and the conductivity decreases more; in the sixth stage, in the late stage of the reaction, it enters the Ostwald ripening stage, and the smaller silver nuclei and nanosilver short rods in the system dissolve and are deposited on the larger silver nanowires again. The system concentration further decreases and tends to be stable, and the system conductivity also further decreases and tends to be balanced.

[0033] The conductivity change trend model is obtained based on the conductivity change law of the system during the preparation of silver nanowires discovered by the inventors. It reflects the conductivity change trend of the above six growth stages rather than the specific conductivity value. The conductivity change trend model can be intuitively displayed through the conductivity change diagram, and can also be reflected by other methods.

[0034] With the help of electron microscope images, the state of each stage of silver nanowire growth can be more intuitively displayed, thereby assisting the establishment of a conductivity change trend model and analyzing the in-situ growth process of silver nanowires.

[0035] Further, the polyols are the same, and the volume ratio is 1:(25-40); the mass ratio of the silver salt, the polyvinyl pyrrolidone, and the soluble halide salt is (80-120):(150-250):1. Preferably, the volume ratio of the polyol is 1:30; the mass ratio of the silver salt, the polyvinyl pyrrolidone, and the soluble halide salt is 100:200:1. Specifically, the polyol is selected from ethylene glycol or glycerol; the silver salt can be selected from silver nitrate, and the soluble halide salt can be selected from one or more of sodium chloride, potassium chloride, sodium bromide, and potassium bromide.

[0036] Furthermore, the target temperature is 120-150°C; the constant dripping rate is 0.6-0.9 mL / min. Preferably, the target temperature in step (4) is 140°C; the constant dripping rate in step (5) is 0.75 mL / min.

[0037] In the present invention, the silver nanowire reaction system is an existing reaction system. When monitoring the conductivity of the system, the temperature and the dripping rate of the reaction process are controlled to remain unchanged in order to ensure the accuracy of the conductivity data analysis. However, it should be noted that the relevant parameters may vary within the conventional range between different reaction systems.

[0038] In a second aspect, the present invention further provides a method for monitoring the in-situ growth process of silver nanowires, comprising the following steps:

[0039] (1) Establishing a silver nanowire reaction system;

[0040] (2) monitoring the conductivity of the reaction system in real time, collecting conductivity data, and then comparing it with the conductivity change trend model;

[0041] (3) Based on the comparison results, determine the in-situ growth stage of the silver nanowires and determine whether the reaction system is abnormal.

[0042] Furthermore, the comparison operation in step (2) is performed in real time.

[0043] Furthermore, the basis for the comparison in step (2) is whether the conductivity change trend conforms to the conductivity change law during the in-situ growth of silver nanowires.

[0044] When the conductivity of the reaction system is abnormal or the conductivity change is significantly different from the conductivity change trend model, that is, it does not conform to the conductivity change law during the growth of silver nanowires, it indicates that the reaction system is abnormal.

[0045] When judging whether the silver nanowire reaction system is abnormal, it can be directly observed with the naked eye. First, the conductivity change trend model is displayed in the form of a conductivity change trend diagram, and then the system conductivity data is collected and drawn into a conductivity change diagram in real time. The conductivity change diagram is compared with the conductivity change trend diagram (standard diagram) to determine whether they have the same change trend, such as line type, slope, radius of curvature, etc., and then determine whether the reaction is proceeding normally; for the accuracy of the judgment, it can also be analyzed with the help of computer means. Under the condition that the conductivity change curve conforms to the conductivity change law (with six change intervals), the data collected in the early stage are fitted, and a mathematical model is established according to the conductivity change characteristics of each interval. Then, by comparing and analyzing the data collected in the early stage, a certain normal offset range is given to the mathematical model of the change curve in each interval, and it can also be manually assigned to give a normal offset range, thereby realizing automatic comparison of the computer. Analysis, when the offset exceeds the limit value, the computer sends a signal to report the abnormality. For example, under the premise of ensuring the basic conductivity change trend, it is stipulated that the conductivity value offset at the end of the first stage does not exceed 1%, the conductivity value offset at the end of the third stage does not exceed 5%, and the conductivity value offset at the end of the sixth stage does not exceed 1%, etc. When the offset value exceeds the above normal range, the computer will respond, that is, the monitoring of the in-situ growth process of silver nanowires is realized; it should be noted that the above-mentioned offset values ​​are only used as examples for reference and do not limit the conductivity change trend model of the present application; further, in actual application, due to differences in reaction conditions, intervention parameters can be added to the conductivity change trend model. When the reaction conditions such as actual reaction temperature, reactant concentration, reactant type, etc. change, the value of the intervention parameter is adjusted to adaptively adjust the conductivity change trend model, thereby improving the accuracy of computer analysis and comparison.

[0046] In a third aspect, the present invention also provides application of the above monitoring method in controllable preparation of silver nanowires.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The characterization method of the in-situ growth process of silver nanowires provided by the present invention summarizes the conductivity change law during the in-situ growth process of silver nanowires by monitoring the conductivity change of the system multiple times, thereby establishing a conductivity change trend model to characterize the in-situ growth process of silver nanowires. The characterization method can monitor the conductivity of the reaction process in real time, and then perform real-time online characterization of the reaction process. The operation is simple and fast, the results are accurate, and it is applicable to conventional silver nanowire preparation systems, and has good application value.

[0049] (2) The method for characterizing the in-situ growth process of silver nanowires provided by the present invention intuitively characterizes the state of each stage of the growth of silver nanowires by means of an electron microscope, which further assists in verifying the reliability of the method for characterizing the in-situ growth process of silver nanowires by using the conductivity change trend of the present invention.

[0050] (3) The monitoring method for the in-situ growth process of silver nanowires provided by the present invention establishes a conductivity change trend model, and uses the model as a reference to compare the conductivity changes in the actual production and preparation process of silver nanowires in real time. It can promptly and quickly report whether the silver nanowire production and preparation process is proceeding normally, thereby realizing real-time monitoring of the silver nano growth process and controllable preparation of silver nanowires.

[0051] (4) The characterization method and monitoring method for the in-situ growth process of silver nanowires provided by the present invention directly use the physical quantity of system conductivity as the monitoring indicator, which can accurately provide the thermodynamic and kinetic information of the growth process without affecting the growth of silver nanowires, and is suitable for the research and production of silver nanowires. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0053] Figure 1-7 They are respectively SEM scanning electron microscope images of the reaction solution at 0 min, 0.5 min, 5 min, 15 min, 25 min, 40 min, and 80 min after the start of the reaction in Example 1 of the present invention;

[0054] Figure 8 This is a conductivity change diagram of Example 1 of the present invention;

[0055] Figure 9-10 The conductivity variation diagram of Example 2-3 of the present invention;

[0056] Figure 11-14 The conductivity change diagram of comparative examples 1-4 of the present invention. DETAILED DESCRIPTION

[0057] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0058] Example 1

[0059] (1) dissolving 3 g of silver nitrate in 15 mL of ethylene glycol to obtain a first reaction solution;

[0060] (2) dissolving 6 g PVP and 0.03 g KCl in 400 mL ethylene glycol to obtain a second reaction solution;

[0061] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0062] (4) heating the second reaction liquid to 140° C. and maintaining the temperature constant, starting the online conductivity tester to collect conductivity data;

[0063] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 0.75 mL / min to carry out a reaction and observing the change in the conductivity of the system;

[0064] (6) Samples of the reaction solution at 0 min, 0.5 min, 5 min, 15 min, 25 min, 40 min, and 80 min of the reaction system were taken and characterized by scanning electron microscopy to obtain SEM images, such as Figure 1-7 As shown; (It should be noted that in this application, the initial time, i.e., 0 min, is taken as the start time of adding the first reaction liquid to the second reaction liquid, and the timing and measurement of the conductivity change of the system are started, and the conductivity data for at least 80 min is taken as the conductivity change data of the whole process of in-situ growth of silver nanowires.)

[0065] (7) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Figure 8 shown.

[0066] like Figure 1 As shown, the first reaction liquid and the second reaction liquid are not mixed, the reaction of the reaction liquids has not yet started, and there are no solid particles in the system at this time; Figure 8 The graph shows the conductivity change of the silver nanowire during the reaction process of Example 1. The curve includes 6 intervals, corresponding to the six stages of the growth of the silver nanowire. In the first interval, about 0-1min, the conductivity is relatively low and relatively stable. Figure 2 As shown, at this time, silver ions combine with chloride ions to form silver chloride precipitation, and large-sized solid particles begin to appear in the system. At this time, the anions in the silver salt replace the chloride ions to maintain the constant ion concentration in the system, and the conductivity of the system remains stable. In the second interval, about 1-10 minutes, the conductivity of the system begins to increase linearly, such as Figure 3 As shown, the number of large-sized particles in the system is relatively Figure 2This is because a small amount of chloride ions have been combined, and the addition of silver ions and silver salt anions in the system has led to a linear increase in ion concentration, which in turn leads to a linear increase in the system conductivity. In the third interval, around 10-20 minutes, the conductivity continues to increase, but the increase rate is lower than that in the third stage. Figure 4 As shown in the figure, there are more small-sized particles in the system. This is because the silver ions begin to be reduced to silver atoms as the first reaction solution continues to be added, which leads to a decrease in the increase in the system ion concentration, and then a decrease in the increase in the system conductivity. In the fourth interval, around 20-30 minutes, the system conductivity begins to decrease, as shown in the figure. Figure 5 As shown in the figure, a one-dimensional structure begins to appear in the system. This is because the reaction solution has been mixed completely at 20 minutes, and the number of ions no longer increases. As the reaction proceeds, the silver ions continue to be reduced to silver atoms to form silver nuclei and grow anisotropically to form short rods. The decrease in silver ion concentration leads to a decrease in the system ion concentration, and the conductivity begins to decrease. In the fifth interval, around 30-50 minutes, the system conductivity further decreases, and the decrease increases, as shown in the figure. Figure 6 As shown, the one-dimensional structure in the system is relative to Figure 5 The number and length of the nanorods increase. This is because as the reaction proceeds, the nucleation rate increases due to the self-catalytic effect of silver, and the speed at which the short rods further grow into silver nanowires increases, resulting in a faster decrease in the system ion concentration, which in turn leads to a greater decrease in the system conductivity. In the sixth stage, after 50 minutes, the system conductivity continues to decrease until it tends to equilibrium, such as Figure 7 As shown in the figure, the length and number of nanowires in the system further increase. This is because in the later stage of the reaction, when it enters the Ostwald ripening stage, the smaller silver cores and nanosilver rods in the system dissolve and deposit again on the larger silver nanowires, producing silver nanowires with a certain aspect ratio, which causes the system concentration to further decrease and tend to be stable, and causes the system conductivity to further decrease and tend to be balanced.

[0067] Example 2

[0068] (1) dissolving 2.4 g of silver nitrate in 15 mL of glycerol to obtain a first reaction solution;

[0069] (2) dissolving 4.5 g PVP and 0.03 g KCl in 400 mL glycerol to obtain a second reaction solution;

[0070] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0071] (4) heating the second reaction liquid to 120° C. and maintaining the temperature constant, starting the online conductivity tester, and collecting conductivity data;

[0072] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 0.75 mL / min to carry out a reaction and observing the change in the conductivity of the system;

[0073] (7) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig. 9 shown.

[0074] like Fig. 9 As shown, although the conductivity value of Example 2 is different from that of Example 1, the conductivity change diagram of Example 2 also has 6 intervals, and the conductivity change trend of the interval is the same as that in Example 1. The conductivity of the second and third intervals is similar to a linear change, and the slope of the conductivity curve of the third interval is slightly smaller than that of the conductivity of the second interval, that is, the conductivity change diagram in Example 2 can intuitively reflect the in-situ growth process of the silver nanowires of Example 2.

[0075] Example 3

[0076] (1) dissolving 3.6 g of silver nitrate in 15 mL of glycerol to obtain a first reaction solution;

[0077] (2) dissolving 7.5 g PVP and 0.03 g KCl in 400 mL glycerol to obtain a second reaction solution;

[0078] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0079] (4) heating the second reaction liquid to 150° C. and maintaining the temperature constant, starting the online conductivity tester to collect conductivity data;

[0080] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 0.75 mL / min to carry out a reaction and observing the change in the conductivity of the system;

[0081] (7) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig.10 shown.

[0082] like Fig.10 As shown, although the conductivity value of Example 3 is different from that of Examples 1-2, the conductivity change diagram of Example 3 also has 6 intervals, and the conductivity change trend of the interval is the same as that of Examples 1-2. The conductivity of the second and third intervals is similar to a linear change, and the slope of the conductivity curve of the third interval is slightly smaller than that of the conductivity of the second interval, that is, the conductivity change diagram in Example 3 can intuitively reflect the in-situ growth process of the silver nanowires of Example 3.

[0083] In Examples 1-3, when the reaction conditions are different, the conductivity change trends are the same, indicating that the present invention is an implementable and universal solution for characterizing the in-situ growth process of silver nanowires by summarizing the conductivity change law and establishing a conductivity change trend model. It should be noted that the inventors conducted a large number of experiments to establish a conductivity change trend model (specifically referring to the conductivity change diagram in the examples of this application). Due to space limitations, only Examples 1-3 are provided in this application to illustrate the universality of the conductivity change trend model.

[0084] Comparative Example 1

[0085] This comparative example includes most of the steps of Example 1, except that the amount of silver nitrate used is different. The specific preparation method is as follows:

[0086] (1) dissolving 5 g of silver nitrate in 15 mL of ethylene glycol to obtain a first reaction solution;

[0087] (2) dissolving 6 g PVP and 0.03 g KCl in 400 mL ethylene glycol to obtain a second reaction solution;

[0088] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0089] (4) heating the second reaction liquid to 140° C. and maintaining the temperature constant, starting the online conductivity tester to collect conductivity data;

[0090] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 0.75 mL / min to carry out a reaction and observing the change in the conductivity of the system;

[0091] (6) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig.11 shown.

[0092] like Fig.11 As shown in the conductivity change diagram of Comparative Example 1, compared with Examples 1-3, the 1-3 stages in the initial reaction are merged, and the conductivity increases faster in the early stage. Fig.11 From the above, the slope of the linear part in the early stage is large, and the straight line tends to be vertical, which is consistent with the fact that the amount of silver nitrate used in the reaction process is large and the concentration is high, resulting in a faster reaction. Fig.11 The conductivity change diagram can be used to monitor the in-situ growth process of the silver nanowires in Comparative Example 1 through the slope change of the initial conductivity stable increase stage.

[0093] Comparative Example 2

[0094] This comparative example includes most of the operating steps of Example 1, except that the temperature is lowered after the reaction for 70 minutes. The specific preparation method is as follows:

[0095] (1) dissolving 3 g of silver nitrate in 15 mL of ethylene glycol to obtain a first reaction solution;

[0096] (2) dissolving 6 g PVP and 0.03 g KCl in 400 mL ethylene glycol to obtain a second reaction solution;

[0097] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0098] (4) heating the second reaction liquid, maintaining the reaction temperature at 140° C., starting the online conductivity tester, and collecting conductivity data;

[0099] (5) adding the first reaction solution to the second reaction solution at a constant drop rate of 0.75 mL / min to carry out a reaction, observing the change in the conductivity of the system, and starting to cool down after 70 min of the reaction;

[0100] (6) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig.12 shown.

[0101] like Fig.12 As shown, the conductivity change graph of Comparative Example 2 is basically consistent with the conductivity change trend of Examples 1-3. The difference is that after 70 minutes of reaction, the curve smoothness deteriorates, the noise is large, and the conductivity further decreases. This is mainly because the reaction temperature decreases after 70 minutes of reaction, resulting in a non-constant temperature reaction process. The system temperature affects the conductivity, indicating that Fig.12 The conductivity change diagram can be used to monitor the in-situ growth process of the silver nanowires in Comparative Example 2 through the smoothness of the conductivity curve.

[0102] Comparative Example 3

[0103] This comparative example includes most of the operating steps of Example 1, except that the temperature is suddenly reduced to 100°C and kept constant at the 4th minute of the reaction. The specific preparation method is as follows:

[0104] (1) dissolving 3 g of silver nitrate in 15 mL of ethylene glycol to obtain a first reaction solution;

[0105] (2) dissolving 6 g PVP and 0.03 g KCl in 400 mL ethylene glycol to obtain a second reaction solution;

[0106] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0107] (4) heating the second reaction liquid to 140° C. and maintaining the temperature constant, starting the online conductivity tester to collect conductivity data;

[0108] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 1.5 mL / min to carry out the reaction, observing the change in the conductivity of the system. At the 4th minute of the reaction, the temperature suddenly dropped to 100 °C and remained constant;

[0109] (6) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig.13 shown.

[0110] like Fig.13 As shown, the conductivity change diagram of Comparative Example 3 includes 6 intervals, but in the early stage of the reaction, about 0-20 minutes, the conductivity increase decreases after 4 minutes, the slope of the straight line becomes significantly smaller, and the rate of change is much larger than the set correction value. This is mainly because the system temperature decreases after 4 minutes of reaction, and the system temperature affects the conductivity, causing the overall system conductivity to decrease. However, due to the continuous increase in the number of ions in the system, the overall conductivity continues to increase, but the conductivity increase rate decreases significantly, indicating that Fig.13 The conductivity change diagram can be used to monitor the in-situ growth process of the silver nanowires in Comparative Example 3 through the change in conductivity increase.

[0111] Comparative Example 4

[0112] This comparative example includes most of the steps of Example 1, except that the reaction process is initially kept at a low temperature of 80°C, and the temperature is raised to 140°C after 10 minutes and kept constant. The specific preparation method is as follows:

[0113] (1) dissolving 3 g of silver nitrate in 15 mL of ethylene glycol to obtain a first reaction solution;

[0114] (2) dissolving 6 g PVP and 0.03 g KCl in 400 mL ethylene glycol to obtain a second reaction solution;

[0115] (3) The second reaction solution was placed in a 500 mL flask and connected to an online conductivity tester;

[0116] (4) heating the second reaction liquid to 80° C. and maintaining the temperature constant, starting the online conductivity tester to collect conductivity data;

[0117] (5) adding the first reaction solution to the second reaction solution at a constant dropping rate of 1.5 mL / min to carry out the reaction, observing the change in the conductivity of the system, and starting to increase the temperature to 140° C. and maintaining it constant after 10 minutes of reaction;

[0118] (6) After the reaction solution is added dropwise and the system conductivity remains constant, the reaction is terminated and the conductivity change diagram is derived, such as Fig.14 shown.

[0119] like Fig.14As shown, the conductivity change diagram of Comparative Example 4 includes 6 intervals, but the conductivity change trend is different from that of Examples 1-3. In the early stage of the reaction, 0-10min, the system conductivity increases, but the increase in conductivity is smaller than that of Examples 1-3, the slope of the straight line is significantly smaller, and the rate of change is much greater than the set correction value (which can be determined by the conductivity value at 10min. The conductivity at 0min in Examples 1-3 and Comparative Examples 1-5 is between 0-50μScm -1 The conductivity of Examples 1-3 and Comparative Examples 1-4 at 10 min was greater than 200 μScm -1 , while the conductivity of comparative example 5 was less than 200 μScm at 10 min. -1 ), indicating that the reaction system is abnormal, which is due to the low temperature in the initial stage of the reaction. Due to the temperature factor, the overall conductivity of the system is reduced; after 10 minutes, the system temperature is raised to 140°C and kept constant, the temperature abnormality factor is eliminated, the system returns to normal, and the conductivity change trend gradually tends to be consistent with that of Examples 1-3, indicating that by monitoring the conductivity change of the silver nanowire in-situ growth system and comparing it with the system conductivity change trend model, the problem of abnormal temperature of the system can be fed back; and after intervention, the conductivity change trend also returns to normal after the temperature is adjusted to the normal value, indicating that the conductivity change trend of the system can further indicate whether the reaction has returned to normal, that is, the controllable preparation of silver nanowires can be achieved by monitoring the conductivity change of the silver nanowire in-situ growth system.

[0120] In summary, the change in system conductivity can be used to characterize the in-situ growth process of silver nanowires in real time, and by establishing a conductivity change trend model of the silver nanowire reaction system, the reaction process of silver nanowires can be further monitored and anomalies can be reported, thereby achieving controllable preparation of silver nanowires.

[0121] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for monitoring the in-situ growth process of silver nanowires, characterized in that: The specific steps include: (1) dissolving a silver salt in a polyol to obtain a first reaction solution; (2) dissolving polyvinyl pyrrolidone and a soluble halide salt in a polyol to obtain a second reaction solution; (3) placing the second reaction solution in a flask and connecting it to an online conductivity tester; (4) heating the second reaction liquid, maintaining a constant temperature after reaching the target temperature, starting an online conductivity tester, and collecting conductivity data; (5) adding the first reaction solution to the second reaction solution at a constant dropping rate to react, and observing the change in the conductivity of the system; (6) Sampling and processing the reaction solution at different stages of the reaction system, and performing electron microscopy characterization to obtain electron microscopy images; (7) The reaction is terminated after the reaction solution is added dropwise and the system conductivity remains constant; (8) repeating steps (1)-(7), summarizing the conductivity change law during the in-situ growth of silver nanowires, establishing a conductivity change trend model, characterizing the in-situ growth process of silver nanowires, and analyzing the in-situ growth process of silver nanowires based on the conductivity change trend model combined with the electron microscopy image; (9) Establishing a silver nanowire reaction system; (10) monitoring the conductivity of the reaction system in real time, collecting conductivity data, and then comparing it with the conductivity change trend model described in step (8); (11) judging the in-situ growth stage of the silver nanowires and determining whether the reaction system is abnormal based on the comparison results; The polyols in step (1) and step (2) are the same, and the volume ratio is 1:(25-30); the mass ratio of the silver salt, the polyvinyl pyrrolidone, and the soluble halide salt is (80-120):(150-250):1; The target temperature in step (4) is 120-150°C; The constant dripping rate in step (5) is 0.6-0.9 mL / min.

2. The method for monitoring the in-situ growth process of silver nanowires according to claim 1, characterized in that: The comparison operation in step (10) is performed in real time.

3. The method for monitoring the in-situ growth process of silver nanowires according to claim 2, characterized in that: The basis for comparison in step (10) is whether the conductivity change trend conforms to the conductivity change law during the in-situ growth of silver nanowires.

4. Application of the monitoring method according to any one of claims 1 to 3 in the controllable preparation of silver nanowires.

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