TW202041454A - Morphology control in synthesis of metal nanostructures - Google Patents

Abstract

A method of controlling morphology in a synthesis of metal nanostructures. The method includes providing a first-stage reaction mixture, wherein the first-stage reaction mixture including a polyol solvent, a capping agent and a halide salt. The method includes heating the first-stage reaction mixture to a reaction temperature. The method includes adding a second-stage reaction mixture to the heated first-stage reaction mixture to provide a combined mixture, wherein the second-stage reaction mixture including a metal salt dissolved in a polyol solvent. The method includes allowing reaction within the combined mixture for a total reaction time. The second-stage reaction mixture is added to the first-stage reaction mixture within a time span that is less than 10% of the total reaction time.

Description

Morphology control in the synthesis of metal nanostructures

The present invention relates to the synthesis of metal nanostructures and the transparent conductivity prepared from the metal nanostructures.

Transparent conductive includes optically transparent and conductive films. One of the important applications of silver nanowires (AgNW) is to form transparent conductive (TC) layers of electronic devices, such as touch panels, photovoltaic cells, flat liquid crystal displays (LCD), and organic light emitting diodes. Body (OLED) and so on. Various technologies have prepared transparent conduction based on one or more conductive media such as conductive nanostructures. Generally speaking, conductive nanostructures form a percolating network with long-range interconnectivity.

As the number of applications that use transparent conduction continues to increase, improved preparation methods are needed to meet the needs of conductive nanostructures. The electrical and optical properties of the TC layer strongly depend on the physical size of the conductive nanowires forming the permeable network. Traditional preparation methods cannot provide sufficient control over the properties of conductive nanowires (such as length, diameter, and aspect ratio).

According to one aspect, the present invention provides a method for controlling morphology in the synthesis of metal nanostructures. The method includes providing a first-stage reaction mixture, wherein the first-stage reaction mixture includes a polyol solvent, a capping agent, and a halide salt. The method includes heating the first stage reaction mixture to reaction temperature. The method includes adding a second-stage reaction mixture to the heated first-stage reaction mixture to provide a combined mixture, wherein the second-stage reaction mixture includes a metal salt dissolved in a polyol solvent. The method involves subjecting the reactions in the combined mixture to a total reaction time. The second stage reaction mixture is added to the first stage reaction mixture within a time interval less than 10% of the total reaction time.

The above overview presents a brief summary to provide a basic understanding of some of the systems and/or methods described herein. This overview is not an extensive description of the systems and/or methods described in this article. It is not intended to point out key/important components or outline the scope of this system and/or method. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description presented below.

Hereinafter, the subject matter of the present invention will be described more fully with reference to the accompanying drawings, which constitute a part of the specification and illustratively show specific exemplary embodiments. This description is not intended as an extensive or detailed discussion of known concepts. Details that are generally known to persons with ordinary knowledge in the relevant field may be omitted or handled in a summary manner.

The specific terms in this article are used only for convenience, and should not be regarded as a limitation of the disclosed subject matter. Related words used in this text are best understood with reference to the drawings, and similar component symbols are used to indicate similar or similar items. In addition, in the drawings, certain features may be shown in a somewhat rough form.

The following subscripts can be implemented in various different forms, such as methods, devices, elements, and/or systems. Therefore, this subject is not intended to be constructed as being limited to any illustrative implementations listed herein as examples. Rather, the implementation aspects provided herein are only illustrative. These implementation aspects may be in the form of hardware, software, firmware, or any combination thereof, for example.

This article provides a method for controlling morphology in the synthesis of metal nanostructures. The method includes providing a first-stage reaction mixture, wherein the first-stage reaction mixture includes a polyol solvent, a coating agent, and a halogen salt. The method includes heating the first stage reaction mixture to reaction temperature. The method includes adding a second-stage reaction mixture to the heated first-stage reaction mixture to provide a combined mixture, wherein the second-stage reaction mixture includes a metal salt dissolved in a polyol solvent. The method involves subjecting the reactions in the combined mixture to a total reaction time. The second stage reaction mixture is added to the first stage reaction mixture within a time interval less than 10% of the total reaction time.

Such nanostructures can be conductive and used to form a permeable conductive network of nanostructures in devices. As used herein, "conductive nanostructure" or "nanostructure" generally refers to electrical nanostructures, for example, at least one dimension is less than 500 nanometers, or less than 250 nanometers, 100 nanometers, or 50 nanometers. , Or 25nm. Generally speaking, nanostructures are made of metal materials, such as elemental metals (such as transition metals) or metal compounds (such as metal oxides). The metal material can also be a bimetal material or a metal alloy, which includes two or more kinds of metals. Suitable metals include, but are not limited to, silver, gold, copper, nickel, gold-plated silver, platinum, and palladium.

The nanostructure can be of any shape or geometric form. The shape of a given nanostructure can be defined in a simplified way by its aspect ratio, where the aspect ratio is the ratio of the length of the nanostructure to the diameter. For example, some nanostructures are shaped isotropically (ie, aspect ratio = 1). Typical isotropic nanostructures include nanoparticles. In a preferred embodiment, the nanostructure is formed anisotropically (ie, aspect ratio≠1). Anisotropic nanostructures usually have a longitudinal axis along their length. Exemplary anisotropic nanostructures include nanowires, nanorods, and nanotubes, as defined herein.

The nanostructure can be solid or hollow. Solid nanostructures include, for example, nanoparticles, nanorods, and nanowires ("NW"). NW generally refers to a long and thin nanostructure with an aspect ratio of greater than 10, preferably greater than 50, more preferably greater than 100, and most preferably greater than 200. Generally speaking, the length of the nanowire is greater than 500 nanometers, greater than 1 micron, greater than 5 microns, or greater than 10 microns. In one example, NW is in the range of 5 microns to 10 microns. "Nanorods" are usually short and wide anisotropic nanostructures with an aspect ratio of not greater than 10, not greater than 50, not greater than 100, or not greater than 200. Although the present invention can be applied to the preparation of any kind of nanostructures, for the sake of brevity, the synthesis of silver nanowires ("AgNW" or "NW" for short) will be described as an example. However, it should be understood that the present invention is not limited to this, and the present invention covers various nanostructures, metals, etc.

The electrical and optical properties of the TC layer strongly depend on the physical dimensions of the NW, that is, its length and diameter, and more generally, its aspect ratio. NW with a larger aspect ratio forms a more effective conductive network, which achieves higher transparency for a given film resistivity by allowing lower linear density. Since each NW can be regarded as a conductivity, the length and diameter of the respective NW will affect the conductivity of the overall NW network, and therefore the conductivity of the final film. For example, as nanowires become longer, fewer nanowires are required to form a conductive network; and as NW becomes thinner, the resistivity of NW increases, which makes the formed film for a given number of NW is even less conductive.

Similarly, the NW length and diameter will affect the optical transparency and light scattering (haze) of the TC layer. Since nanowires only occupy a very small part of the film, the NW network is optically transparent. However, nanowires absorb and scatter light, so the length and diameter of the NW will largely determine the optical transparency and haze of the conductive NW network. Generally speaking, a thinner NW can increase transmission and reduce haze in the TC layer, which are ideal properties for electronic applications.

In addition, the low aspect ratio nanostructures (by-products in the synthesis process) in the TC layer will cause increased haze because these structures scatter light and do not contribute to the conductivity of the network. Since the synthetic methods for preparing metal nanostructures usually produce a composition containing a variety of nanostructure morphologies (ideal and unimaginable), it is necessary to purify this composition to improve the retention of high aspect ratio nanostructures.

However, NW can be synthesized with smaller and smaller diameters (for example, in the range of tens of nanometers), and these smaller diameters closely match the size of undesired by-products (such as low aspect ratio nanostructures). Due to the similarity in size, composition, and structure between NW and by-products, it is difficult to purify high aspect ratio NW for high-quality TC membranes. The synthesis of NW with uniform length and width distribution helps to purify the ability of such high aspect ratio nanostructures, because this uniform population is the most similar and allows the highest aspect ratio NW compared to the low aspect ratio by-products. Selective purification conditions. Therefore, it is ideal to develop methods for preparing high aspect ratio NWs with uniform length and width distribution, and/or methods that facilitate the formation of NW compared to other low aspect ratio nanostructures.

Once purified, the retained high aspect ratio NW can be used to form TC with desired electrical and optical properties.

Therefore, it is advantageous to develop a controlled synthesis method for preparing NW that is thinner or longer than the current state of the art, or better thinner and longer. It is also preferred that these synthesis methods produce NWs with uniform length and width distribution. Finally, it is better to develop synthetic methods that are more conducive to the preparation of NW than other low aspect ratio nanostructures.

This article describes methods for controlling the preparation of NW to meet the standards.

According to some embodiments, the conductive NW can be prepared by a synthetic method that improves the optical properties of the TC film. This synthesis method controls the length and width distribution of NW and obtains high-yield nanowires at the same time through the following steps: Synthesize reactant composition using polyol line, Introducing various additives, and Use polyol line synthesis method steps and conditions.

The result is a unique NW length and width distribution, which is mixed in the reaction at a high ratio of NW to low aspect ratio nanostructures. Subsequent purification (such as the sedimentation process method) for further removal of low aspect ratio nanostructures can maintain this unique NW length and diameter distribution for incorporation into the final TC material.

In some test samples, ethylene glycol (EG), polyvinylpyrrolidone (PVP), sodium chloride (NaCl), sodium bromide (NaBr), and silver nitrate (AgNO ₃ ) are mixed in the mixture, and then in a nitrogen blanket Under the nitrogen blanket, it is heated to the reaction temperature to produce a mixture of silver nanostructures. Once the reaction is complete, it is removed from heating. The completion of the reaction is defined as when most (>90%) silver ions (Ag ⁺ ) are reduced to silver metal (Ag ⁰ ). The concentration of silver ions was monitored by potentiometric titration of an aliquot of the reaction mixture obtained during the reaction. The crude mixture is characterized by the following: scanning electron microscope (SEM) to measure NW width, and dark field (DF) microscope with customized image analysis software to measure NW length and low aspect ratio by-products to high aspect ratio The ratio of NW. These test samples represent different strategies for controlling the width and length distribution of NW, and/or the ratio of NW to by-products. The average NW width, length, and low aspect ratio by-products (ie, "Objects") to NW ratio system of each test sample are summarized in Table 1.

In the connotation of reaction, timing can be defined in many ways. In one embodiment, the timing may refer to the total reaction time, so it is referred to as "total reaction time" below. Alternatively, timing can refer to a specific point in time that occurs within the time period defined by the start and end of the reaction. Finally, timing can refer to the "addition time" for adding one or more reactants to the reactor and/or the reaction mixture.

In many prior art examples of polyol reaction, silver salt is added at the beginning of the reaction, along with other reactants, before heating the mixture. Generally speaking, in these examples, the addition time of the silver salt to the reaction mixture is undefined.

Alternatively, in other prior art examples, the silver salt is only added when the reaction mixture is heated to the reaction temperature. Generally speaking, in these examples, the addition time of the silver salt to the reaction mixture is relatively long, that is, greater than 10% of the total reaction time.

The present invention provides that precise control of the NW width and length distribution can be achieved by carefully controlling the time point and the addition time of the silver salt. In one example, the present invention shows that limiting the addition time of silver salt to less than 10% of the total reaction time can increase the number of NW formed in the reaction (relative to the low aspect ratio by-product), and the resulting The average diameter of NW decreases.

Limiting the addition time to less than 10% of the total reaction time can be called "short", "fast", or other similar expressions. In contrast, an addition time greater than 10% of the total reaction time can be called "slow", "long", or other similar expressions. It should be understood that making the addition time less than 10% is an aspect of the present invention. Other solutions of the present invention are: making the addition time less than 5% of the total reaction time, making the addition time less than 2.5% of the total reaction time, making the addition time less than 1% of the total reaction time, and making the addition time less than 0.5 of the total reaction time %.

Figure 1 presents an example of the method according to the invention. The illustrated method 100 of FIG. 1 starts with step 102, in which a first-stage reaction mixture is provided. The first-stage reaction mixture may include a polyol solvent, a coating agent, and a halogen salt. In step 104, the first-stage reaction mixture is heated to the reaction temperature. In step 106, the second stage reaction mixture is added to the heated first stage reaction mixture to provide a combined mixture. The second stage reaction mixture may include a metal salt dissolved in a polyol solvent. In step 108, the reaction in the combined mixture is allowed to proceed for a total reaction time. It should be understood that the addition of the second-stage reaction mixture to the first-stage reaction mixture in step 106 is performed within a time interval of less than 10% of the total reaction time.

It would be useful to provide some comparisons between the prior art method and the method according to the invention. Therefore, five embodiments are briefly pointed out below.

Example 1 is a prior art method in which silver salt is introduced at the beginning of the reaction before heating the reaction mixture. The product of the method of Example 1 is shown in Figure 2A, which is an SEM image of the prior art network at 60,000 magnification.

Embodiment 2 is a prior art method, which introduces silver salt when the reaction mixture is heated to the reaction temperature, wherein the addition time is greater than 10% of the total reaction time. The product of the method of Example 2 is shown in Figure 2B, which is an SEM image of the prior art network at 60,000 magnification.

Example 3 is a method according to one aspect of the present invention. The method of Example 3 includes introducing the silver salt when the reaction mixture is heated to the reaction temperature, wherein the addition time is less than 10% of the total reaction time. The product of the method of Example 3 is shown in Figure 2C, which is an SEM image of a network according to one aspect of the present invention at a magnification of 60,000.

In addition, as an optional change in Example 3, the control of the NW distribution can be achieved by tuning the relative loadings of chloride ions (Cl ⁻ ) and bromide ions (Br ⁻ ) in the reaction mixture. Halides (e.g. Cl ^- and Br ^-) help in the early stages of the reaction to form the core NW and controls the total halogen loading (i.e., Cl ^- and Br ^- of the sum) or Br ^- Cl ^- on scale, or both , Can affect the NW length and width distribution and the formation of low aspect ratio by-products and the relative number of high aspect ratio NW. This can be called halogen tuning to further control the NW morphology (and reduce the formation of low aspect ratio by-products).

Example 4 is a method according to one aspect of the present invention. Specifically, this embodiment using the method still less than 10% of the total reaction time, and further comprising adding time to Br ^- salt instead of all Cl ^- salt, but maintaining the same total concentration of halogen. This substitution can lead to a reduction in the average NW diameter. The product of the method of Example 4 is shown in Figure 2D, which is an SEM image of a network according to one aspect of the present invention at a magnification of 60,000.

In Example 5, it is shown that careful tuning of the relative loading of Br ^- and Cl ^- salt can maintain the reduced NW diameter obtained in the example using only Br ^- , while increasing the high aspect ratio NW versus the low aspect ratio by-product The relative number of. The product of the method of Example 5 is shown in Figure 2E, which is an SEM image of a network according to one aspect of the present invention at a magnification of 60,000.

The following provides a more detailed discussion for the five embodiments.

In Example 1, the silver salt was added at the beginning of the reaction. The method of Example 1 includes the following steps: In a 1 liter reaction vessel, 420 grams of ethylene glycol (EG), 56.2 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000) solution (5% (weight/weight) in EG) ), 2.45 grams of NaCl solution (5% (weight/weight) in EG), 2.26 grams of NaBr solution (5% (weight/weight) in EG), and 16.21 grams of silver nitrate (AgNO ₃ ) solution (14 in EG) % (Weight/weight)) was heated to 170°C and stirred under a nitrogen (N ₂ ) blanket for 60 minutes. The reaction mixture was removed from the heating and then allowed to cool to room temperature under a nitrogen blanket while stirring. The average width and length of the nanowires are 21.6 nm and 15.9 μm, respectively. The ratio of returned products with low aspect ratio to NW is 7.03.

In Example 2, the silver salt was added at the reaction temperature with an addition time greater than 10% of the total reaction time. The method of Example 2 includes the following steps: in a 1 liter reaction vessel, 476 grams of ethylene glycol (EG), 2.81 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000), 2.45 grams of NaCl solution (5% (in EG) (Weight/weight)), and 2.26 grams of NaBr solution (5% (weight/weight) in EG) heated to 170°C and stirred under nitrogen (N ₂ ) blanket for 50 minutes. To the stirred mixture, 13.50 ml of silver nitrate (AgNO ₃ ) solution (14% (weight/weight) in EG) was added during 10 minutes at an addition rate of 1.35 ml/min by means of a syringe pump. The above reaction mixture was then stirred at 170°C under a nitrogen blanket for 1 hour. The reaction mixture was removed from the heating and then allowed to cool to room temperature under a nitrogen blanket while stirring. In this embodiment, the addition time (ie, 10 minutes) is relatively slow or long compared to 1 hour. The average width and length of the nanowires are 21.3 nm and 15.2 μm, respectively. The ratio of returned products with low aspect ratio to NW is 7.03.

In Example 3, the silver salt was added at the reaction temperature with an addition time less than 10% of the total reaction time. The method of Example 3 includes the following steps: in a 1 liter reaction vessel, 476 grams of ethylene glycol (EG), 2.81 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000), 2.45 grams of NaCl solution (5% (in EG) (Weight/weight)), and 2.26 grams of NaBr solution (5% (weight/weight) in EG) heated to 170°C and stirred under nitrogen (N ₂ ) blanket for 50 minutes. To the stirring mixture, 16.21 grams of silver nitrate (AgNO ₃ ) solution (14% (weight/weight) in EG) was added in the course of 3 seconds. The above reaction mixture was then stirred at 170°C under a nitrogen blanket for 1 hour. The reaction mixture was removed from the heating and then allowed to cool to room temperature under a nitrogen blanket while stirring. In this embodiment, the addition time (ie, 3 seconds) is relatively short or faster than 1 hour. The average width and length of the nanowires are 16.2 nanometers and 6.2 microns, respectively. The ratio of returned products with low aspect ratio to NW is 2.55.

In Example 4, the Br ^- only variable was used with an addition time of less than 10% of the total reaction time at the reaction temperature. The method of Example 4 includes the following steps: in a 1 liter reaction vessel, 477 grams of ethylene glycol (EG), 2.81 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000), and 6.78 grams of NaBr solution (5% in EG (Weight/weight)) Heat to 170°C and stir for 50 minutes under nitrogen (N ₂ ) coating. To the stirring mixture, 16.21 grams of silver nitrate (AgNO ₃ ) solution (14% (weight/weight) in EG) was added in the course of 3 seconds. The above reaction mixture was then stirred at 170°C under a nitrogen blanket for 1 hour. The reaction mixture was removed from the heating and then allowed to cool to room temperature under a nitrogen blanket while stirring. The average width and length of the nanowire are 13.3 nanometers and 5.4 microns, respectively. The ratio of returned products with low aspect ratio to NW is 9.75.

In Example 5, a finely tuned halogen concentration was used at the reaction temperature with an addition time of less than 10% of the total reaction time. The method of Example 5 includes the following steps: in a 1 liter reaction vessel, 477 grams of ethylene glycol (EG), 2.81 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000), 2.10 grams of NaCl solution (5% (in EG) (Weight/weight)), and 3.70 grams of NaBr solution (5% (weight/weight) in EG) heated to 170°C and stirred under nitrogen (N ₂ ) blanket for 60 minutes. To the stirred mixture, 16.8 grams of silver nitrate (AgNO ₃ ) solution (14% (weight/weight) in EG) was added in the course of 3 seconds. The above reaction mixture was then stirred at 170°C under a nitrogen blanket for 1 hour. The reaction mixture was removed from the heating and then allowed to cool to room temperature under a nitrogen blanket while stirring. The average width and length of the nanowire are 12.8 nm and 5.7 μm, respectively. The ratio of returned products with low aspect ratio to NW is 3.52.

A series of examples of the physical dimensions of silver nanowires formed according to the present invention are shown in Table 1 below. Table 1 Average NW width, length, and return product/NW ratio Sample number Average NW width (standard deviation) (nm) Average NW length (standard deviation) (nm) Low aspect ratio returned products/NW Example 1 21.6 (5.6) 15.9 (11.2) 7.03 Example 2 21.3 (4.3) 15.2 (11.4) 7.03 Example 3 16.2 (3.2) 6.2 (4.3) 2.55 Example 4 13.3 (4.1) 5.4 (5.0) 9.75 Example 5 12.8 (3.3) 5.7 (4.3) 3.52

The NW width and length distributions of Examples 1 to 5 are shown in Figs. 3 and 4, respectively. Note that in Figure 4, the peaks of the length distribution curves of Examples 1 and 2 (ie, the prior art) are significantly lower than the peaks of the length distribution curves of Examples 3 to 5 (ie, the present invention). Note also that in Figure 3, the peak values of the width (diameter) distribution curves of Examples 1 and 2 (ie, the prior art) are more significant than those of Examples 3 to 5 (ie, the present invention). The ground is more to the right.

As an integration, the present invention provides a method for controlling morphology in the synthesis of metal nanostructures. The method includes providing a first-stage reaction mixture, wherein the first-stage reaction mixture includes a polyol solvent, a coating agent, and a halogen salt. The method includes heating the first stage reaction mixture to reaction temperature. The method includes adding a second-stage reaction mixture to the heated first-stage reaction mixture to provide a combined mixture, wherein the second-stage reaction mixture includes a metal salt dissolved in a polyol solvent. The method involves subjecting the reactions in the combined mixture to a total reaction time. The second stage reaction mixture is added to the first stage reaction mixture within a time interval less than 10% of the total reaction time.

The present invention provides changes to the time of addition. As some examples, the addition time is less than 5% of the total reaction time, the addition time is less than 2.5% of the total reaction time, the addition time is less than 1% of the total reaction time, and the addition time is less than 0.5% of the total reaction time.

The present invention provides that the total reaction time can be defined as the duration between the start of the addition of the second-stage reaction mixture and the stopping of the heating of the combined reactants. In some examples, the total reaction time is less than 360 minutes, the total reaction time is less than 240 minutes, the total reaction time is less than 120 minutes, and the total reaction time is less than 60 minutes.

The present invention provides that when the total reaction time is presented in a specific duration, the addition time can also be defined as a specific duration. As some examples, the addition time can be less than 10 minutes, the addition time can be less than 5 minutes, the addition time can be less than 1 minute, and the addition time can be less than 30 seconds.

The present invention provides the use of various materials. As an example, the polyol includes at least one of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, and 1,2-butanediol. As an example, the coating includes polyvinylpyrrolidone. As an example, the halide salt includes at least one of the following: bromide salt, chloride salt, or both bromide salt and chloride salt. As an example, the metal salt includes at least one of the following: silver salt, copper salt, and gold salt. As an example, the metal salt contains silver nitrate.

The present invention provides various reactant concentrations. As an example, the concentration of silver salt may be at least 10 mM, but less than 120 mM. As an example, the total concentration of halide salt may be at least 2 mM, but less than 30 mM. As an example, the molar ratio of bromide salt to chloride salt may be at least 0.2, but less than 5.

The present invention provides various results. As an example, the resulting metal nanostructure has an average width of less than or equal to 20 nanometers and an average length of at least 5 microns, or an average width of less than or equal to 15 nanometers and an average length of at least 5 microns. As an example, the obtained metal nanostructure has a width coefficient of variation of less than 30%.

This application claims the priority of U.S. Provisional Application No. 62/828,644, titled "MORPHOLOGY CONTROL IN SYNTHESIS OF METAL NANOWIRES" filed on April 3, 2019, which is incorporated herein for reference.

Unless otherwise indicated, "first", "second", and/or similar terms are not intended to imply time schemes, spatial schemes, sequences, etc. Instead, such terms are only used as indications, names, etc. of features, elements, items, etc. For example, the first object and the second object generally correspond to item A and item B or two different or identical items or the same item.

In addition, the "example" used herein refers to use as an illustration, description, etc., and is not necessarily advantageous. As used herein, "or" is intended to be an inclusive "or" rather than an exclusive "or". In addition, the "one" used in this application is usually constructed to mean "one or more", unless otherwise specified or directed to the singular form in the text. In addition, at least one of A and B and/or similar terms generally refers to A or B or both A and B. In addition, as for the "including", "having", "with", and/or variations thereof used for detailed description and the scope of patent application, such terms are intended to be inclusive similar to the term "including".

Although the subject matter of the invention has been described by text specific to structural features and/or methodological rules, it should be understood that the subject matter defined in the scope of the appended patent application is not necessarily limited to the specific features or rules described above. Rather, the above-mentioned specific features or rules are disclosed as an example form for implementing at least part of the claims.

This article provides various operations for implementation. The order in some or all operations described herein should not be constructed to imply that these operations must rely on the order. Those skilled in the art can perceive alternative sequences that have the advantages of this description. In addition, it will be understood that not all operations must be present in every implementation aspect provided herein.

In addition, although the present invention is presented and described for one or more embodiments, those skilled in the art can think of and equivalent substitutions and changes based on the reading and understanding of this specification and the accompanying drawings. The present invention includes all such substitutions and changes, and is limited to the scope of the following patent applications. In particular, for various functions performed by the above-mentioned elements (e.g., elements, sources, etc.), the terms used to describe such elements are intended to correspond to any element that can perform the specific function of the described element (e.g., function The equivalent of the above), although not the structural equivalent of the disclosed structure, unless otherwise indicated. In addition, although a particular feature of the present invention may only be disclosed by one of multiple embodiments, if it can be ideal and advantageous for any given or specific application, such feature may be combined with one or more other embodiments. Combination of other features.

100: method 102, 104, 106, 108: steps

Although the technology presented herein can be implemented in various alternative forms, the specific implementation aspects depicted in the drawings are only a few examples that supplement the description provided herein. These implementation aspects should not be construed as restrictive, such as limiting the scope of the attached patent application.

The disclosed subject matter can take the physical form of specific components and the arrangement of components, and its implementation will be described in detail in this specification and the accompanying drawings that form part of the specification, in which:

Figure 1 presents an example of the method according to the invention.

Figure 2A is an SEM image of a prior art silver nanowire network prepared according to the details outlined in Example 1, at a magnification of 60,000.

Figure 2B is an SEM image of a prior art silver nanowire network prepared according to the details outlined in Example 2, at a magnification of 60,000.

Figure 2C is an SEM image of the silver nanowire network prepared according to the present invention and outlined in Example 3 at a magnification of 60,000.

Figure 2D is an SEM image of the silver nanowire network prepared according to the present invention and outlined in Example 4 at a magnification of 60,000.

Figure 2E is an SEM image of the silver nanowire network prepared according to the present invention and outlined in Example 5 at a magnification of 60,000.

Fig. 3 is a graph showing the frequency of occurrence of nanowire width/diameter in the permeable nanowire network formed by Examples 1 and 2 (prior art) and Examples 3 to 5 of the method of the present invention.

Figure 4 shows the permeable nanowire network formed by Embodiments 1 and 2 (prior art) and Embodiments 3 to 5 of the present invention, and the length distribution of the nanowires.

100: method

102, 104, 106, 108: steps

Claims (20)

A method for controlling morphology in the synthesis of metal nanostructures, the method comprising: Providing a first-stage reaction mixture, wherein the first-stage reaction mixture includes a polyol solvent, a capping agent, and a halide salt; The first stage reaction mixture is heated to the reaction temperature: Adding a second-stage reaction mixture to the heated first-stage reaction mixture to provide a combined mixture, wherein the second-stage reaction mixture comprises a metal salt dissolved in a polyol solvent; and Allowing the reaction in the combined mixture to proceed for a total reaction time; The second-stage reaction mixture is added to the first-stage reaction mixture within a time interval less than 10% of the total reaction time. The method according to claim 1, wherein the time interval is less than 5% of the total reaction time. The method according to claim 2, wherein the time interval is less than 2.5% of the total reaction time. The method according to claim 3, wherein the time interval is less than 1% of the total reaction time. The method according to claim 4, wherein the time interval is less than 0.5% of the total reaction time. The method according to claim 1, wherein the total reaction time is defined as the duration between the start of adding the second-stage reaction mixture and the stopping of heating the combined mixture. The method according to claim 6, wherein the total reaction time is less than 360 minutes. The method according to claim 7, wherein the total reaction time is less than 240 minutes. The method according to claim 8, wherein the total reaction time is less than 120 minutes. The method according to claim 1, wherein the polyol solvent comprises at least one of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, and 1,2-butanediol. The method according to claim 1, wherein the coating agent comprises polyvinylpyrrolidone. The method according to claim 1, wherein the halide salt comprises at least one of the following: bromide salt, chloride salt, or both bromide salt and chloride salt. The method according to claim 1, wherein the metal salt comprises at least one of the following: silver salt, copper salt, and gold salt. The method according to claim 1, wherein the metal salt comprises silver nitrate. The method according to claim 1, wherein the resulting metal nanostructure has an average width less than or equal to 20 nanometers and an average length of at least 5 microns. The method according to claim 15, wherein the obtained metal nanostructure has an average width less than or equal to 15 nanometers and an average length of at least 5 microns. The method according to claim 1, wherein the obtained metal nanostructure has a width coefficient of variation of less than or equal to 30%. The method according to claim 13, wherein the concentration of the silver salt is at least 10 mM but less than 120 mM. The method according to claim 1, wherein the total concentration of the halide salt is at least 2 mM but less than 30 mM. The method according to claim 12, wherein the molar ratio of the bromide salt to the chloride salt is at least 0.2 but less than 5.

Images