TWI833002B - 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

Morphological control in the synthesis of metallic nanostructures

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

Transparent conductive includes optically clear and electrically conductive films. One of the important applications of silver nanowires (AgNW) is currently used to form transparent conductive (TC) layers in electronic devices such as touch panels, photovoltaic cells, flat liquid crystal displays (LCDs), and organic light-emitting diodes. body (OLED), etc. Various techniques have been developed to produce transparent conductors based on one or more conductive media such as conductive nanostructures. Generally speaking, conductive nanostructures form percolating networks with long-range interconnectivity.

As the number of applications using transparent conductivity continues to increase, improved preparation methods are needed to meet the demands 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 fabrication methods do not 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 The 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 includes 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 in a time interval of less than 10% of the total reaction time.

The above summary presents a brief summary to provide a basic understanding of some aspects of the systems and/or methods described herein. This summary is not an extensive description of the systems and/or methods described herein. It is not intended to identify key/critical elements or to delineate the scope of the system and/or method. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented below.

100:Method

102, 104, 106, 108: Steps

Although the technology presented herein may be implemented in various alternative forms, the specific implementation aspects depicted in the drawings are but a few examples that supplement the description provided herein. These embodiments should not be construed as limiting, such as limiting the patent scope of the appended applications.

The subject matter disclosed may take physical form in the form of specific components and arrangements of components, implementations of which are described in detail in this specification and illustrated in the accompanying drawings forming a part of this specification, in which:

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

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

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

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

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

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

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

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

The subject matter of the present invention will be described more fully hereinafter with reference to the accompanying drawings, which constitute a part of this specification and which illustratively show certain exemplary embodiments. This description is not intended to be an extensive or detailed exploration of known concepts. Details generally known to those of ordinary skill in the relevant art may be omitted or treated in a summarized manner.

The specific terms used herein are used for convenience only and should not be construed as limitations of the subject matter disclosed. The relevant text used in this article is best understood with reference to diagrams, which are similar to The component symbol is used to indicate similar or similar items. Additionally, in the drawings, certain features may be shown in somewhat schematic form.

The following subject matter may be implemented in various forms, such as methods, apparatus, components, and/or systems. Accordingly, this subject matter is not intended to be construed as limited to any illustrative implementations set forth herein as examples. Rather, implementation aspects are provided herein for illustrative purposes only. These implementations may, for example, be in the form of hardware, software, firmware, or any combination thereof.

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 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 includes 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 in a time interval of less than 10% of the total reaction time.

Such nanostructures can be electrically conductive and used to form a permeable conductive network of nanostructures in a device. As used herein, "conductive nanostructure" or "nanostructure" generally refers to conductive nanometer-sized structures, such as at least one dimension smaller than 500 nanometers, or smaller than 250 nanometers, 100 nanometers, 50 nanometers , or 25nm. Generally speaking, nanostructures are made of metallic materials, such as elemental metals (such as transition metals) or metal compounds (such as metal oxides). The metallic material can also be a bimetallic material or a metal alloy, which contains two or more types of metals. Suitable metals include, but are not limited to, silver, gold, copper, nickel, gold plated silver, platinum, and palladium.

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

Nanostructures can be solid or hollow. Solid nanostructures include, for example, nanoparticles, nanorods, and nanowires ("NWs"). NW generally refers to long and thin nanostructures with an aspect ratio 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 micrometer, greater than 5 micrometers, or greater than 10 micrometers. In one example, the NW is in the range of 5 microns to 10 microns. "Nanorods" are generally short and wide anisotropic nanostructures with an aspect ratio of no greater than 10, no greater than 50, no greater than 100, or no greater than 200. Although the present invention can be applied to prepare any kind of nanostructure, for the sake of simplicity, the synthesis of silver nanowires ("AgNW" or simply "NW") will be described as an example. However, it should be understood that the present invention is not limited thereto, and the present invention covers various nanostructures, metals, etc.

The electrical and optical properties of the TC layer are strongly dependent on the physical dimensions of the NW, that is, its length and diameter, and more generally, its aspect ratio. NWs with larger aspect ratios form more efficient conductive networks, which achieve higher transparency for a given film resistivity by allowing lower line density. Since each NW can be considered as a conductor, the respective NW length and diameter will Affects the conductivity of the overall NW network, and therefore the conductivity of the final film. For example, as nanowires become longer, fewer nanowires are needed to form a conductive network; and as NWs become thinner, the resistivity of the NWs increases, which makes the resulting film resistant to a given number of NW is less conductive.

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

In addition, low aspect ratio nanostructures in the TC layer (a by-product of the synthesis process) can cause increased haze because these structures scatter light without contributing to the conductivity of the network. Since synthetic methods for preparing metal nanostructures often produce compositions containing multiple nanostructure morphologies (ideal and non-ideal), such compositions need to be purified to enhance the retention of high aspect ratio nanostructures.

However, NWs can be synthesized at increasingly smaller diameters (e.g., in the tens of nanometer range), and these smaller diameters closely match the size of undesirable byproducts (e.g., low aspect ratio nanostructures). Due to the similarity in size, composition, and structure between NWs and by-products, it is difficult to purify high aspect ratio NWs for use in high-quality TC membranes. Synthesizing NWs with uniform length and width distributions facilitates the ability to purify such high aspect ratio nanostructures, as such uniform populations behave most similarly and allow optimal processing of high aspect ratio NWs compared to low aspect ratio by-products. Selective purification conditions. Therefore, it would be ideal to develop high-length fabrics with uniform length and width distribution. The method of NW with aspect ratio, and/or the method that is more beneficial to the formation of NW compared with other low aspect ratio nanostructures.

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

Therefore, it would be advantageous to develop controlled synthetic methods for producing NWs that are preferably thinner or longer, or better still, both thinner and longer than the current state of the art. It is also preferred that these synthesis methods produce NWs with uniform length and width distribution. Ultimately, it would be preferable to develop synthetic methods that are more conducive to the preparation of NWs than other low aspect ratio nanostructures.

This article describes methods to control the preparation of NWs to comply with these standards.

According to some embodiments, conductive NWs can be prepared by a synthesis method that improves the optical properties of the TC film. This synthesis method controls the length and width distribution of NWs and simultaneously obtains high-yield nanowires through the following steps: using polyol wires to synthesize reactant compositions, introducing various additives, and using polyol wire synthesis method steps and conditions .

The result is a unique NW length and width distribution that is mixed in the reaction with a high ratio of NW to low aspect ratio nanostructures. Subsequent purification (eg, sedimentation process methods) used to further remove 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 ) were mixed in the mixture and then covered with nitrogen. The mixture is heated under a nitrogen blanket to the reaction temperature of the mixture forming the silver nanostructure. Remove from heat once the reaction is complete, defined as when the majority (>90%) of the silver ions (Ag ⁺ ) have been reduced to silver metal (Ag ⁰ ). Silver ion concentration was monitored by potentiometric titration of aliquots of the reaction mixture taken during the reaction. The crude mixture was characterized by scanning electron microscopy (SEM) to measure NW width, and dark field (DF) microscopy with custom image analysis software to measure NW length and low aspect ratio by-products versus high aspect ratio The ratio of NW. The test samples represent different strategies for controlling NW width and length distribution, and/or NW to byproduct ratio. The average NW width, length, and low aspect ratio by-products (i.e., "objects") to NW ratios for each test sample are systematically summarized in Table 1.

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

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

Alternatively, in other prior art examples, the silver salt is added only when the reaction mixture is heated to 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.

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

Limiting the addition time to less than 10% of the total reaction time may be referred to as "short", "fast", or other similar expressions. In contrast, an addition time greater than 10% of the total reaction time may be referred to as "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 a method according to the invention. The illustrative method 100 of Figure 1 begins with step 102 in which a first stage reaction mixture is provided. The first stage reaction mixture may include a polyol solvent, a capping agent, and a halide salt. In step 104, the first stage reaction mixture is heated to 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 comprise 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 occurs within a time interval of less than 10% of the total reaction time.

It would be useful to provide some comparisons of prior art methods and the method according to the present invention. Therefore, five embodiments are briefly indicated below.

Example 1 is a prior art method in which the 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 a prior art network at 60,000 magnification.

Example 2 is a prior art method in which the silver salt is introduced when the reaction mixture is heated to reaction temperature, where 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 a prior art network at 60,000 magnification.

Embodiment 3 is a method according to one aspect of the present invention. The method of Example 3 includes introducing the silver salt while the reaction mixture is heated to 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 at 60,000 magnification of a network according to one aspect of the present invention.

In addition, as an optional variation of Example 3, the control of the NW distribution can be achieved by tuning the relative loading amounts of chloride ions (Cl ^- ) and bromide ions (Br ^- ) in the reaction mixture. Halide ions (such as Cl ^- and Br ^- ) help NW nucleation in the early stages of the reaction and control the total halide loading (i.e., the sum of Cl ^- and Br ^- ), or the ratio of Br ^- to Cl ^- , or both , can affect the NW length and width distribution as well as the relative numbers of low aspect ratio by-products and high aspect ratio NWs formed. This can be called halide tuning to further control the NW morphology (and reduce the formation of low aspect ratio by-products).

Embodiment 4 is a method according to one aspect of the present invention. Specifically, this example method still uses an addition time of less than 10% of the total reaction time and also includes replacing all Cl ^- salts with Br ^- salts, but maintaining the same total halogen concentration. This substitution can result in a decrease in the average NW diameter. The product of the method of Example 4 is shown in Figure 2D, which is an SEM image at 60,000 magnification of a network according to one aspect of the present invention.

It is shown in Example 5 that careful tuning of the relative loadings of ^Br- and ^Cl- salts can maintain the reduced NW diameter obtained in the Br ^- only examples while increasing the contribution of high aspect ratio NWs to low aspect ratio byproducts relative number. The product of the method of Example 5 is shown in Figure 2E, which is an SEM image at 60,000 magnification of a network according to one aspect of the present invention.

A more detailed discussion is provided below for these 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) and 56.2 grams of polyvinylpyrrolidone (PVP) (molecular weight: 1,300,000) solution (5% (weight/weight) in EG ), 2.45 grams of NaCl solution (5% (w/w) in EG), 2.26 grams of NaBr solution (5% (w/w) in EG), and 16.21 grams of silver nitrate (AgNO ₃ ) solution (14 in EG % (wt/wt)) heated to 170°C and stirred under nitrogen (N ₂ ) blanket for 60 minutes. The reaction mixture was removed from the heat and allowed to cool to room temperature under a blanket of nitrogen while stirring. The average width and length of the nanowires are 21.6 nanometers and 15.9 micrometers respectively. The ratio of low aspect ratio returns 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) w/w)), and 2.26 g of NaBr solution (5% (w/w) in EG) was 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% (w/w) in EG) was added via syringe pump at an addition rate of 1.35 ml/min over the course of 10 minutes. The reaction mixture was then stirred at 170°C for 1 hour under a blanket of nitrogen. The reaction mixture was removed from the heat and allowed to cool to room temperature under a blanket of nitrogen while stirring. In this example, this 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 nanometers and 15.2 micrometers respectively. The ratio of low aspect ratio returns 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) w/w)), and 2.26 g of a NaBr solution (5% (w/w) in EG) was heated to 170°C and stirred under a nitrogen ( _N2 ) blanket for 50 minutes. To the stirred mixture, 16.21 grams of silver nitrate ( _AgNO3 ) solution (14% (w/w) in EG) was added over the course of 3 seconds. The reaction mixture was then stirred at 170°C for 1 hour under a blanket of nitrogen. The reaction mixture was removed from the heat and allowed to cool to room temperature under a blanket of nitrogen while stirring. In this example, this addition time (ie, 3 seconds) is relatively short or fast compared to 1 hour. The average width and length of the nanowires are 16.2 nanometers and 6.2 micrometers respectively. The ratio of low aspect ratio returns to NW is 2.55.

In Example 4, a Br ^- only variant was used at reaction temperature with an addition time of less than 10% of the total reaction time. 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 (wt/wt)) was heated to 170°C and stirred under nitrogen ( _N2 ) blanket for 50 minutes. To the stirred mixture, 16.21 grams of silver nitrate ( _AgNO3 ) solution (14% (w/w) in EG) was added over the course of 3 seconds. The reaction mixture was then stirred at 170°C for 1 hour under a blanket of nitrogen. The reaction mixture was removed from the heat and allowed to cool to room temperature under a blanket of nitrogen while stirring. The average width and length of the nanowires are 13.3 nanometers and 5.4 micrometers respectively. The ratio of low aspect ratio returns to NW is 9.75.

In Example 5, a finely tuned halogen concentration was used at 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) w/w)), and 3.70 g of NaBr solution (5% (w/w) in EG) was heated to 170°C and stirred under nitrogen ( _N2 ) blanket for 60 minutes. To the stirred mixture, 16.8 grams of silver nitrate ( _AgNO3 ) solution (14% (w/w) in EG) was added over the course of 3 seconds. The reaction mixture was then stirred at 170°C for 1 hour under a blanket of nitrogen. The reaction mixture was removed from the heat and allowed to cool to room temperature under a blanket of nitrogen while stirring. The average width and length of the nanowires are 12.8 nanometers and 5.7 micrometers respectively. The ratio of low aspect ratio returns to NW is 3.52.

Examples of physical dimensions of silver nanowires formed in accordance with the present invention are listed in Table 1 below.

Table 1 Average NW width, length, and returned product/NW ratio

The NW width and length distributions of Examples 1 to 5 are shown in Figure 3 and Figure 4 respectively. Note that in Figure 4, the peak value of the length distribution curve of Examples 1 and 2 (ie, the prior art) is significantly lower than the peak value of the length distribution curve of Examples 3 to 5 (ie, the present invention). Also note that in Figure 3, the peak value of the width (diameter) distribution curve of Examples 1 and 2 (i.e., the prior art) is significant compared to the peak value of the width distribution curve of Examples 3 to 5 (i.e., the present invention). The ground is more to the right.

As a whole, 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 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 includes 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 in a time interval of less than 10% of the total reaction time.

The present invention provides for variation in addition time. 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 starting to add the second stage reaction mixture and stopping 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 as 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 for the use of a variety of materials. As examples, the polyol includes at least one of: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, and 1,2-butanediol. As an example, the coating agent includes polyvinylpyrrolidone. As examples, halide salts include at least one of: bromide salts, chloride salts, or both bromide salts and chloride salts. As examples, metal salts include at least one of the following: silver salts, copper salts, and gold salts. As an example, metal salts include silver nitrate.

The present invention provides various reactant concentrations. As an example, the concentration of silver salt may be at least 10mM, but less than 120mM. As an example, the total concentration of halide salts may be at least 2mM, but less than 30mM. 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 less than or equal to 15 microns. An average width of nanometers and an average length of at least 5 microns. As an example, the resulting metal nanostructure has a coefficient of variation of width less than 30%.

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

Unless otherwise indicated, "first," "second," and/or similar terms are not intended to imply a temporal scheme, spatial scheme, sequence, or the like. Rather, such terms are used only as designators, 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 in this article means that it is used as an illustration, explanation, etc., and does not necessarily have to be advantageous. As used herein, "or" is intended to be an inclusive "or" and not an exclusive "or." In addition, "a" as used in this application is generally constructed to mean "one or more" unless otherwise specified or directed to the singular form in the context. In addition, at least one of A and B and/or similar terms generally refer to A or B or both A and B. Additionally, with respect to the terms "includes," "has," "with," and/or variations thereof when used in detailed descriptions and claims, such terms are intended to be inclusive similar to the term "includes."

Although inventive subject matter has been described in terms specific to structural features and/or methodological rules, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or rules described above. Rather, the specific features or rules described above are disclosed as exemplary forms of implementing at least some of the claimed claims.

This article provides various operations for implementation. The order in some or all operations described herein should not be construed to imply that such operations must rely on the order. Those skilled in the art will recognize alternative sequences that have the advantages of this description. Additionally, it will be understood that not all operations necessarily exist in every implementation provided herein.

In addition, although the present invention has been presented and described with respect to one or more embodiments, equivalent substitutions and changes may be contemplated by others skilled in the art based on a 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 claims. In particular, for the various functions performed by the above-described elements (e.g., elements, sources, etc.), the terms used to describe such elements are intended to correspond to any element (e.g., function) that performs the specified function of the described element. equivalents), although not structural equivalents to the disclosed structures, unless otherwise indicated. Additionally, although specific features of the invention may be disclosed in only one of the various embodiments, such features may be combined with one or more other embodiments if such features are desirable and advantageous for any given or particular application. Combined with other features.

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102, 104, 106, 108: Steps

Claims (19)

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); heating the first-stage reaction mixture to 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 contains water dissolved in a polyol solvent. a metal salt in the combined mixture; and allowing the reaction in the combined mixture to proceed for a total reaction time; wherein the total reaction time is defined as the duration between starting to add the second stage reaction mixture and stopping heating of the combined mixture; wherein The second stage reaction mixture is added to the first stage reaction mixture in a time interval of less than 10% of the total reaction time. The method of claim 1, wherein the time interval is less than 5% of the total reaction time. The method of claim 2, wherein the time interval is less than 2.5% of the total reaction time. The method of claim 3, wherein the time interval is less than 1% of the total response time. The method of claim 4, wherein the time interval is less than 0.5% of the total reaction time. The method of claim 1, wherein the total reaction time is less than 360 minutes. The method of claim 6, wherein the total reaction time is less than 240 minutes. The method of claim 7, wherein the total reaction time is less than 120 minutes. The method of claim 1, wherein the polyol solvent includes at least one of the following: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, and 1,2-butanediol. The method of claim 1, wherein the coating agent contains polyvinylpyrrolidone. The method of claim 1, wherein the halide salt includes at least one of the following: bromide salt, chloride salt, or both bromide salt and chloride salt. The method of claim 1, wherein the metal salt includes at least one of the following: silver salt, copper salt, and gold salt. The method of claim 1, wherein the metal salt contains silver nitrate. The method of claim 1, wherein the obtained metal nanostructure has an average width less than or equal to 20 nanometers and an average length of at least 5 micrometers. The method of claim 14, wherein the obtained metal nanostructure has an average width less than or equal to 15 nanometers and an average length of at least 5 micrometers. The method of claim 1, wherein the obtained metal nanostructure has a coefficient of variation of width less than or equal to 30%. The method of claim 12, wherein the concentration of the silver salt is at least 10mM but less than 120mM. The method of claim 1, wherein the total concentration of the halide salt is at least 2mM but less than 30mM. The method of claim 11, wherein the molar ratio of the bromide salt to the chloride salt is at least 0.2 but less than 5.