A method for preparing silver nanowires mediated by metal-organic coordination polymer

Abstract

The application provides a metal organic coordination polymer-mediated silver nanowire preparation method, and comprises the following steps: preparing a supramolecular assembly agent, a high molecular polymer protective agent, a halide salt and a soluble silver salt solution respectively; the supramolecular assembly agent is at least one of cinnamic acid, p-coumaric acid, coffee acid and tannin; the halide salt and the supramolecular assembly agent are sequentially added into the soluble silver salt solution to form a silver ion-supramolecular assembly coordination polymer solution; the high molecular polymer protective agent is added into the silver ion-supramolecular assembly coordination polymer solution, stirring is conducted, and the reaction is carried out at-20-80 DEG C under light shielding for 0.1-10 h; after the reaction is completed, centrifugation, washing, vacuum drying and re-dispersion are conducted, and the silver nanowire is obtained. The silver nanowire prepared by the technical scheme of the application is superfine in diameter, has a curled morphology at the end, contains defects inside, the reaction can be carried out in water, the production capacity is high (more than 80 g / L), the process is simple, and the application is more environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials technology, and in particular to a method for preparing silver nanowires mediated by metal-organic coordination polymers. Background Technology

[0002] Currently, the main methods for preparing silver nanowires include template methods, wet chemical methods, UV-induced methods, polyol methods, solvothermal methods, and hydrothermal methods. Template methods are divided into hard template and soft template methods, which control the morphology and aspect ratio of silver nanowires by pre-made templates. Removing hard templates is relatively complex, while soft templates offer poor morphological control. Wet chemical methods use reducing agents such as sodium citrate, ascorbic acid, and sodium borohydride to reduce silver sources to silver nanowires. The reaction process is sensitive, and the reaction products often have poor dispersibility. UV-induced methods only react with reactants exposed to UV light, easily leading to uneven reaction. Polyol methods, solvothermal methods, and hydrothermal methods have been proven to be synthetic methods with high yields and good morphological control. However, polyol methods often use environmentally harmful organic reagents such as ethylene glycol and glycerol as solvents and reducing agents. Both methods require heating to high temperatures. Hydrothermal and solvothermal methods, in particular, are difficult to scale up in closed reaction vessels, further limiting their industrial applications. Furthermore, the quality of silver nanowires obtained by the above methods needs to be improved. Therefore, there is an urgent need to develop an environmentally friendly, mild reaction condition, quality-controllable, high-efficiency, and high-yield method for synthesizing silver nanowires. Summary of the Invention

[0003] To address the above technical problems, this invention discloses a method for preparing silver nanowires mediated by metal-organic coordination polymers. The resulting silver nanowire products are uniform, ultra-fine in diameter (20-50 nm), have curled ends, contain internal defects, have high production capacity (80 g-100 g / L), operate at ultra-low reaction temperatures, and can be carried out in water. The process is simple and more environmentally friendly.

[0004] The technical solution adopted by this invention is as follows:

[0005] A method for preparing silver nanowires mediated by metal-organic coordination polymers includes the following steps:

[0006] Step S1: Prepare supramolecular assembling agents, polymer protectants, halide salt reaction rate controllers, and soluble silver salt solutions, each with dual functions of reduction and coordination polymerization. The supramolecular assembling agent is one or a mixture of two or more of the following: cinnamic acid, p-coumaric acid, caffeic acid, rosmarinic acid, gallic acid, sinapic acid, protocatechuic acid, salicylic acid, benzoic acid, p-hydroxybenzoic acid, resveratrol, isodane, paclitaxel, coumarin, osthol, aescin, angelicin, apophene, erythrosine, chelidonine, tannin, and azirmonanthracene.

[0007] In step S2, the halide salt and supramolecular assembly agent are sequentially added to a soluble silver salt solution to form a silver ion-supramolecular assembly agent coordination polymer solution; a polymeric protective agent is added to the silver ion-supramolecular assembly agent coordination polymer solution in step S2, wherein the mass ratio of the supramolecular assembly agent, silver salt, halide salt, and polymeric protective agent is (0.1-150):(0.1-100):(0.01-10):(1-600); then the mixture is stirred and reacted in the dark at a temperature of -20-80℃ for 0.1-10 hours.

[0008] Step S3: After the reaction is complete, centrifugation and washing are performed to obtain the reaction product. The reaction product is then redispersed and vacuum dried to obtain silver nanowires.

[0009] The generation of silver nanowires generally involves nucleation and directional growth. Unlike previously disclosed silver nanowire generation processes, the present invention's technical solution, with the addition of a soluble silver salt solution, utilizes supramolecular assemblies and halide salt reaction rate control agents. The generated silver halide slowly releases silver ions through ionization. The supramolecular assemblies first form silver ion-supramolecular assemblies coordination polymers with silver ions through coordination complexation. These coordination polymers have a metal-organic metal framework structure, exhibiting a near-one-dimensional structure in the form of long strips or ribbons. These silver ion-supramolecular assemblies act as templates during the growth of silver nanowires. It is this one-dimensional structure that fixes the silver ions along a one-dimensional direction, laying the foundation for the subsequent reduction of silver ions to silver atoms and their subsequent qualitative arrangement and growth into silver nanowires. Subsequently, the supramolecular assembler acts as a reducing agent. Silver atoms anchored in the silver ion-supramolecular assembler coordination polymer and oriented along the one-dimensional direction are reduced in situ by the supramolecular assembler. The reduced silver atoms will attract argentophilic groups (such as O and N) in the molecular structure of the polymer protectant. Specifically, a layer of polymer protectant will be adsorbed on the outer layer of the silver ion-supramolecular assembler coordination polymer where silver atoms are generated. Due to the steric hindrance between polymers, the in-situ reduced silver atoms can be effectively wrapped up, preventing the deposition of other silver atoms. As the reduction reaction proceeds, silver atoms accumulate along the one-dimensional structure of the silver ion-supramolecular assembler coordination polymer until the silver nanowires are generated. At this point, both silver ions and the supramolecular assembler will detach from the silver ion-supramolecular assembler coordination polymer framework. Silver ions become silver atoms and participate in the growth process of silver nanowires, while the supramolecular assembler will be oxidized into oxidation products.

[0010] In the technical solution of this invention, a supramolecular assembly agent works synergistically with a halide salt and a polymeric protective agent:

[0011] Firstly, the reaction rate control effect of the halide salt reaction rate controller is similar to that of the traditional silver nanowire synthesis method. The slow hydrolysis of the generated silver halide in the reaction solution has a slow release effect on silver ions, ensuring that the silver atoms in the reaction solution are always maintained within a certain concentration range. This greatly reduces the probability of collision between silver atoms generated in a short time in the solution, thus satisfying the concentration fluctuation conditions for the growth of silver nanowire nuclei. However, unlike the traditional silver nanowire synthesis method, the generated silver halide cannot be directly used as the nucleus site of silver nanowires.

[0012] Secondly, the supramolecular assembler, which has dual functions, acts as both a template agent and a reducing agent. This supramolecular assembler can effectively coordinate with silver ions to form a one-dimensional or near-one-dimensional silver ion-supramolecular assembler coordination polymer template. The formation of this coordination polymer ensures that the silver ions in the reaction solution are no longer randomly distributed, but are ordered and anchored into a one-dimensional directional arrangement by the coordination polymer. This lays the structural foundation for the directional deposition of silver atoms. Subsequently, the active groups in the supramolecular assembler act as a reducing agent, which can slowly reduce silver ions into silver atoms in situ.

[0013] Thirdly, the guiding role of polymer protective agents: the active groups (such as O and N) in polymer protective agents have a full electron configuration in their outer electron shells, while silver atoms have empty orbitals with unfilled electrons. Therefore, the electrons in the outer shells of O or N will fill the empty orbitals of silver atoms, which conforms to the lowest energy state. This means that a layer of polymer protective agent will be adsorbed on the outer layer of the silver ion-supramolecular assembly agent coordination polymer at the location where silver atoms are generated. At the same time, because polymers often have long molecular chains, the steric hindrance can effectively wrap the silver atoms that are reduced in situ, and also prevent the deposition of other silver atoms.

[0014] In summary, the technical solution of this invention benefits from the reaction rate control effect of the halide salt reaction rate controller, the dual function of the supramolecular assembly agent as a template agent and reducing agent, and the guiding effect of the polymer protectant. The synergistic effect of these three factors successfully achieved the synthesis of silver nanowires.

[0015] As a further improvement of the present invention, the polymeric protective agent is one or a mixture of two or more of gelatin, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, triethylhexylphosphate, sodium lauryl sulfate, methylpentanol, polyacrylamide, guru gum and fatty acid polyethylene glycol esters, polyethyleneimine, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium lauryl sulfonate, and sodium laurylbenzene sulfonate. More preferably, the polymeric protective agent is polyvinylpyrrolidone.

[0016] As a further improvement of the present invention, the halide salt reaction rate control agent is one or a mixture of two or more of the following: sodium chloride, sodium bromide, potassium chloride, potassium bromide, copper chloride, copper bromide, ferric chloride, ferrous chloride, ferric bromide, ferrous bromide, cobalt chloride, cobalt bromide, zinc chloride, zinc bromide, zinc chloride, and zinc bromide.

[0017] As a further improvement of the present invention, the soluble silver salt is one or a mixture of two or more of silver chloride, silver sulfate, silver carbonate, silver nitrite, silver acetate, silver sulfate, silver fluoride, silver chlorate, silver perchlorate, silver nitrate, silver perbromate, silver periodate, silver bicarbonate, silver sulfide, silver gluconate, and silver cyanate. More preferably, the soluble silver salt is silver nitrate.

[0018] As a further improvement of the present invention, the solvent of the soluble silver salt solution is at least one selected from water, alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide. More preferably, the solvent of the soluble silver salt solution is water.

[0019] As a further improvement of the present invention, in step S2, the stirring speed is 20-500 r / min. More preferably, the stirring speed is 50-300 r / min.

[0020] Preferably, the reaction temperature in step S2 is 0-65℃, and more preferably, the reaction time is 0.5-6h. More preferably, the reaction temperature in step S2 is 25-65℃, and the reaction time is 2-5h.

[0021] As a further improvement of the present invention, in step S3, the centrifugation speed is 1000-7000 r / min, and the number of centrifugal washing cycles is 1-4.

[0022] As a further improvement of the present invention, in step S3, the vacuum drying temperature is 30-80℃, and the vacuum drying time is 1-20h. Further, the vacuum drying temperature is 50-80℃. More preferably, the vacuum drying time is 3-10h.

[0023] As a further improvement of the present invention, in step S3, silver nanowire powder is obtained by air jet milling after vacuum drying.

[0024] As a further improvement of the present invention, in step S3, the reaction product is redispersed using an organic solvent, wherein the organic solvent includes one or more of alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide. More preferably, the organic solvent is one or more of ethanol, isopropanol, and n-hexane.

[0025] As a further improvement of the present invention, in the solution after adding the polymer protective agent in step S2, the mass ratio of the supramolecular assembling agent, silver salt, halide salt, and polymer protective agent is (24-30):10:(0.01-2):(80-120). More preferably, the mass ratio of the supramolecular assembling agent, silver salt, halide salt, and polymer protective agent in the solution after adding the polymer protective agent in step S2 is (24-30):10:(0.02-0.025):(80-100).

[0026] As a further improvement of the present invention, the mass concentration of the soluble silver salt solution is 0.1-1000 mg / ml.

[0027] As a further improvement of the present invention, the supramolecular assembling agent is at least one of cinnamic acid, tannin, p-hydroxybenzoic acid, and caffeic acid.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] First, the technical solution of the present invention uses halide salts as reaction rate control agents, supramolecular assembly agents that can have a certain reduction effect and can form coordination polymers with silver ions as reducing agents and template agents, and polymers as protective agents. By utilizing the synergistic effect among the three, the disadvantage of the nucleation growth process in water-based solutions being difficult to control is overcome. Under mild conditions, the silver source is reduced to high-quality silver nanowires. The prepared silver nanowire products are uniform, with ultra-fine diameters (20-50 nm), curled ends, and internal defects.

[0030] Secondly, the technical solution of this invention adopts a one-pot, one-step reduction technology, which greatly improves the reaction efficiency. The required equipment is simple and the operation is easy. It does not require inert gas protection or harsh reaction conditions such as high temperature and high pressure, avoids the introduction of environmentally harmful organic solvents, greatly reduces the complexity of subsequent purification, improves production efficiency, effectively reduces production costs, and has a high unit volume yield of silver nanowires (80g-100 / L), making it suitable for large-scale production and application with good prospects.

[0031] Third, the supramolecular assembly agent of the present invention uses plant-derived components extracted from plants, and the reaction solvent is not limited to traditional organic solutions, but can be a water-based solution, which has less environmental toxicity and is more in line with the requirements of green and environmentally friendly practices. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the reaction process in Embodiment 1 of the present invention.

[0033] Figure 2 and Figure 3 The above are SEM results of silver nanowires prepared in Example 1 of this invention at different magnifications.

[0034] Figure 4 and Figure 5 These are SEM images of the TEM results of the single silver nanowires prepared in Example 1 of this invention at different magnifications.

[0035] Figure 6 The XRD results are for the silver nanowires prepared in Example 1 of this invention.

[0036] Figure 7 and Figure 8 The above are SEM results of silver nanowires prepared in Comparative Example 1 of this invention at different magnifications.

[0037] Figure 9 and Figure 10 This is the SEM result of the intermediate process sample material of Comparative Example 2 of this invention at different magnifications.

[0038] Figure 11 The XRD results are for the intermediate process sample material of Comparative Example 2 of this invention.

[0039] Figure 12 and Figure 13 The above are SEM results of silver nanowires prepared at different magnifications for Comparative Example 2 of this invention.

[0040] Figure 14 and Figure 15 This is the SEM result of the intermediate process sample material of Comparative Example 3 of this invention at different magnifications.

[0041] Figure 16 The XRD results are for the intermediate sample material of Comparative Example 3 of this invention.

[0042] Figure 17 The above is the SEM result of the silver nanowires prepared in Comparative Example 3 of this invention.

[0043] Figure 18 and Figure 19 The SEM results of silver nanowires prepared in Example 2 of this invention are shown at different magnifications.

[0044] Figure 20 and Figure 21 The images show SEM images of the TEM results of the single silver nanowires prepared in Example 2 of this invention at different magnifications.

[0045] Figure 22 The image shows the SEM image of the product prepared in Example 3 of this invention.

[0046] Figure 23 The image shows the SEM results of the product prepared in Example 4 of this invention.

[0047] Figure 24 The image shows the SEM results of the product prepared in Comparative Example 5 of this invention.

[0048] Figure 25 and Figure 26 The images show SEM results of the product prepared in Comparative Example 6 of this invention at different magnifications.

[0049] Figure 27 The XRD results are those of the product prepared in Comparative Example 6 of this invention.

[0050] Figure 28 This is a reaction mechanism analysis diagram of the silver nanowire preparation method of the present invention. Detailed Implementation

[0051] The preferred embodiments of the present invention will be described in further detail below.

[0052] A method for preparing silver nanowires mediated by metal-organic coordination polymers, such as... Figure 1 As shown, it includes the following steps:

[0053] Step S1: Prepare solutions of supramolecular assembling agent with dual functions of reduction and coordination polymerization, polymer protectant, halide salt reaction rate controller and soluble silver salt, respectively, and stir and mix them evenly for later use.

[0054] Step S2: The halide salt and supramolecular assembly agent are added sequentially to the soluble silver salt solution to form a silver ion-supramolecular assembly agent coordination polymer.

[0055] Step S3: Add the polymer protectant to the solution from step S2 and react in the dark.

[0056] Step S4: The reaction product is centrifuged and washed with water. The reaction product is redispersed with an organic solvent to obtain a silver nanowire concentrate. The silver nanowire concentrate is vacuum dried and finally pulverized with airflow to obtain silver nanowire powder.

[0057] In step S1, a supramolecular assembling agent with dual functions of reduction and coordination polymerization, a polymer protectant, a halide salt reaction rate controller, and a soluble silver salt are prepared into a solution, stirred and mixed evenly for later use. When preparing the soluble silver salt, it should be prepared in a dark environment to avoid any photoreduction.

[0058] The solvents used in preparing supramolecular assembly agents, polymer protectants, halide salt reaction rate controllers, and soluble silver salt solutions include, but are not limited to, one or more of water, alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide; preferably, one or more of water, ethanol, ethylene glycol, glycerol, N,N-dimethylformamide, and N-methylpyrrolidone.

[0059] The supramolecular assembling agents include, but are not limited to, one or more of the following: cinnamic acid, p-coumaric acid, caffeic acid, rosmarinic acid, gallic acid, sinapic acid, protocatechuic acid, salicylic acid, benzoic acid, p-hydroxybenzoic acid, resveratrol, isodane, paclitaxel, coumarin, osthol, aescin, angelicin, apophene, erythrosine, chelidonine, tannin, and azirmonanthracene. The selection of these supramolecular assembling agents is mainly based on aromatic derivatives with benzene rings and side chain groups containing oxygen-containing groups such as hydroxyl, carbonyl, or carboxyl groups. The supramolecular assembly mainly originates from the coordination of lone electrons of oxygen occupying empty orbitals in the outer shell of silver particles.

[0060] The polymeric protective agent includes, but is not limited to, one or more of gelatin, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, triethylhexylphosphate, sodium lauryl sulfate, methylpentanol, polyacrylamide, guru gum and fatty acid polyethylene glycol esters, polyethyleneimine, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium lauryl sulfonate, and sodium laurylbenzene sulfonate; preferably, one or more of gelatin, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, sodium lauryl sulfate, sodium lauryl sulfonate, and sodium laurylbenzene sulfonate, and more preferably, one or more of gelatin, gum arabic, polyvinyl alcohol, and polyvinylpyrrolidone.

[0061] The halide salt reaction rate control agent includes, but is not limited to, one or more of sodium chloride, sodium bromide, potassium chloride, potassium bromide, copper chloride, copper bromide, ferric chloride, ferrous chloride, ferric bromide, ferrous bromide, cobalt chloride, cobalt bromide, zinc chloride, zinc bromide, nickel chloride, and nickel bromide; preferably, one or more of sodium chloride, sodium bromide, potassium chloride, potassium bromide, copper chloride, and copper bromide.

[0062] The soluble silver salt includes, but is not limited to, one or more of silver chloride, silver sulfate, silver carbonate, silver nitrite, silver acetate, silver sulfate, silver fluoride, silver chlorate, silver perchlorate, silver nitrate, silver perbromate, silver periodate, silver bicarbonate, silver sulfide, silver gluconate, and silver cyanate; preferably, one or more of silver chloride, silver sulfate, silver carbonate, silver acetate, silver sulfate, silver chlorate, silver nitrate, silver perbromate, silver bicarbonate, silver gluconate, and silver cyanate; more preferably, any one of silver chloride, silver sulfate, silver carbonate, silver acetate, silver sulfate, silver chlorate, silver nitrate, silver perbromate, silver bicarbonate, silver gluconate, and silver cyanate.

[0063] In the solution of step S3, the mass ratio of the supramolecular assembling agent, silver salt, halide salt, and polymer protective agent is (0.1-150):(0.1-100):(0.01-10):(1-600); more preferably, the mass ratio of the supramolecular assembling agent:silver salt:halide salt, and polymer protective agent is (24-30):10:(0.01-2):(80-120).

[0064] The mass concentration of the supramolecular assembly agent solution is 0.1-1000 mg / ml; preferably 1-100 mg / ml. The mass concentration of the polymer protective agent solution is 0.1-2000 mg / ml; preferably 10-200 mg / ml. The mass concentration of the halide salt reaction rate control agent solution is 0.1-3000 mg / ml; preferably 1-1000 mg / ml. The mass concentration of the soluble silver salt solution is 0.1-1000 mg / ml; preferably 1-500 mg / ml.

[0065] The volume ratio of the supramolecular assembling agent, polymer protectant, halide salt reaction rate controller, and soluble silver salt solution is (0.1-100):(0.1-100):(0.1-10):(0.1-200); preferably (1-50):(1-30):(0.1-5):(1-100).

[0066] In step S3, the reaction temperature is -20-80℃, preferably 0-60℃; the reaction time is 0.1-10h, preferably 0.5-6h; and the stirring speed is 20-500r / min, preferably 50-300r / min. More preferably, the reaction temperature is 25-65℃, and the reaction time is 2-6h. More preferably, the reaction temperature is 40-65℃, and the reaction time is 2-5h.

[0067] In step S4, the reaction product is centrifuged and washed with water, and the reaction product is redispersed with an organic solvent to obtain a silver nanowire concentrate. The silver nanowire concentrate is then vacuum dried and finally pulverized with airflow to obtain silver nanowire powder.

[0068] The centrifugation speed of the reaction product is 1000-7000 r / min, preferably 2000-5000 r / min; the number of centrifugation and washing cycles is 1-4 times, preferably 1-2 times.

[0069] The organic solvents used in the dispersed silver nanowire concentrate include, but are not limited to, one or a mixture of two or more of the following: alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide; preferably, one or more of the following: ethanol, isopropanol, and n-hexane.

[0070] The vacuum drying temperature is 30-80℃, preferably 40-70℃; the vacuum drying time is 1-20h, preferably 3-10h.

[0071] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0072] Example 1

[0073] Aqueous solutions of 2.5 mg / ml cinnamic acid, 20 mg / ml polyvinylpyrrolidone, 0.1 mg / ml sodium chloride, and 2 mg / ml silver nitrate were prepared and stirred until homogeneous. 0.5 ml of sodium chloride solution and 10 ml of silver nitrate solution were added to 20 ml of cinnamic acid solution and stirred until homogeneous. Then, 9 ml of polyvinylpyrrolidone solution was added to the mixture. The reaction was carried out at 60°C with stirring for 2 hours. The solution gradually changed from colorless to light yellow, and finally to gray, with the formation of flocculent substances. The reaction product was centrifuged at 4000 r / min and washed with water. This process was repeated twice. The reaction product was redispersed with 10 ml of ethanol to obtain a concentrated silver nanowire solution. The concentrated silver nanowire solution was vacuum dried at 70°C for 10 hours and finally pulverized by air jet milling to obtain silver nanowire powder.

[0074] Depend on Figure 2-6The product obtained in this example is a silver nanowire with uniform size, no obvious particulate impurities, ultra-fine diameter (20-40 nm), curled ends, and internal defects. The curled ends and internal defects of the silver nanowires obtained in this example may be related to the special reaction mechanism of this method. Due to the coordination complexation between the supramolecular assembly agent and the silver atom, the distribution of silver ions in the solution changes from random distribution to one-dimensional directional arrangement. When the active groups in the supramolecular assembly agent act as reducing agents, the silver ions are slowly reduced to silver atoms in situ. The silver atoms are stacked together in layers, thus showing a layered contrast image with alternating light and dark areas in the TEM results. It is this special reaction mechanism that may cause the silver nanowires synthesized by this method to have a curled end structure and internal defects.

[0075] Comparative Example 1

[0076] Based on Example 1, the difference in this comparative example is that no halide salt reaction rate control agent was added during the preparation process. Aqueous solutions of 2.5 mg / ml cinnamic acid, 8 mg / ml polyvinylpyrrolidone, and 2 mg / ml silver nitrate were prepared and mixed thoroughly. 10 ml of silver nitrate solution was added to 20 ml of cinnamic acid solution and mixed thoroughly. Then, 5 ml of polyvinylpyrrolidone solution was added to the above mixture, and the reaction was carried out at 60°C with stirring for 2 hours. The reaction product was centrifuged at 4000 rpm and washed with water. This process was repeated twice. The reaction product was redispersed using 10 ml of ethanol to obtain a concentrated product solution. The concentrated solution was dropped onto a silicon wafer for SEM characterization to obtain the results.

[0077] Figure 7-8 The product obtained in this comparative example was silver nanoparticles with uneven size and shape, without the formation of silver nanowires. No halide salts were added as reaction rate control agents in this comparative example. A large number of silver ion-supramolecular assembly agent coordination polymer intermediates were formed, resulting in a large number of silver atoms reduced in a short time. Due to the adsorption of silver atoms by the polymer protective agent, when there were many silver atoms, they aggregated along a one-dimensional oriented arrangement, forming silver nanoparticles. Scanning electron microscopy results also showed that the growth pattern of the silver particles was similar to that of condensation from surrounding material.

[0078] Comparative Example 2

[0079] Based on Example 1, the difference is that no polymeric protective agent was added during the preparation process. Aqueous solutions of 2.5 mg / ml cinnamic acid, 0.1 mg / ml sodium chloride, and 2 mg / ml silver nitrate were prepared and stirred until homogeneous. Then, 0.5 ml of sodium chloride solution and 10 ml of silver nitrate solution were added to 20 ml of cinnamic acid solution, stirred until homogeneous, and reacted at 60°C for 2 h. The reaction product was centrifuged at 4000 r / min and washed with water. The above steps were repeated twice. The reaction product was redispersed with 10 ml of ethanol to obtain a concentrated product solution. The concentrated solution was dropped onto a silicon wafer for SEM characterization to obtain the results.

[0080] Figure 9-11 The results were obtained by sampling during the intermediate process of the reaction 30 minutes after the start of this embodiment. The products obtained were silver ion-supramolecular assembly agent coordination polymer, silver halide, and a small amount of silver nanoparticles. The elongated product, which has a one-dimensional structure, is the silver ion-supramolecular assembly agent coordination polymer, which has poor conductivity and appears charged when observed under a scanning electron microscope. The spherical or cubic products are the generated silver halide. The dotted particulate products distributed on the surface of the elongated product are silver nanoparticles generated by in-situ reduction of the supramolecular assembly agent. Only a small amount of silver nanowires were generated in the products, and the dispersibility was poor.

[0081] Figure 12-13 The product obtained in this embodiment, in addition to the complex components of the silver ion-supramolecular assembly agent coordination polymer and Ag ions, silver halide, and a small amount of silver nanoparticles, also includes entangled silver nanoribbons and silver nanoplates with uneven size distribution. The entangled structures appearing as filaments or ribbons are the generated silver nanoribbons, while the products appearing as triangles or hexagons are silver nanoplates. The formation of silver nanoribbons is also related to the silver ion-supramolecular assembly agent coordination polymer anchoring the silver atoms into a one-dimensional structure. However, due to the lack of a polymeric protective agent, although the silver atoms are reduced in the one-dimensional direction, they are not effectively protected, increasing the probability of collisions with other silver atoms and generating silver nanoribbon structures and silver nanoplates with poor morphology. The prolonged reaction time may be related to the equilibrium of the chemical reaction. Due to the lack of a polymeric protective agent, the silver atoms reduced in situ cannot be removed from the silver ion-supramolecular assembly agent coordination polymer system. A higher concentration of silver atoms in the coordination polymer will reduce the chemical reaction rate of the reduction reaction, thus increasing the reaction time.

[0082] Comparative Example 3

[0083] Based on Example 1, the difference in this comparative example is that no halide salt reaction rate control agent and polymer protectant were added during the preparation process. Aqueous solutions of 2.5 mg / ml cinnamic acid and 2 mg / ml silver nitrate were prepared and stirred until homogeneous. Then, 10 ml of silver nitrate solution was added sequentially to 20 ml of cinnamic acid solution, stirred until homogeneous, and reacted at 60°C for 2 hours. The reaction product was centrifuged at 4000 rpm and washed with water. This process was repeated twice. The reaction product was redispersed using 10 ml of ethanol to obtain a concentrated product solution. The concentrated solution was dropped onto a silicon wafer for SEM characterization to obtain the results.

[0084] Figure 14-16 The results were obtained by sampling during the intermediate process of the reaction, 30 minutes after the start of the reaction in this embodiment. The product obtained in this embodiment is a silver ion-supramolecular assembly agent coordination polymer and a small amount of silver nanoparticles. The elongated product is a complex of silver ion-supramolecular assembly agent and Ag ion, which has poor conductivity and shows charging under a scanning electron microscope. The dotted products distributed on the surface of the elongated product are the generated silver nanoparticles. There are no silver nanowires in the product. The formation of the silver ion-supramolecular assembly agent coordination polymer and silver nanoparticles is the same as in Example 2.

[0085] Figure 17 The product obtained in this embodiment consists of entangled silver nanoribbons and silver nanoplates with uneven size distribution. The entangled structures, appearing as filaments or ribbons, are the generated silver nanoribbons, while the triangular or hexagonal products are the silver nanoplates. Only a small amount of silver nanowires are produced in the product, resulting in poor dispersibility. The reasons for the product appearance and prolonged reaction time are the same as in Example 2. Unlike Example 2, this comparative example also did not add a polymeric protective agent but still generated a small amount of entangled silver nanoribbons. This is because, although the halide salt reaction rate control agent was absent, the generated silver atoms were not adsorbed by the polymeric protective agent, and a small amount of silver atoms could still deposit along a one-dimensional direction, generating near-one-dimensional silver nanoribbons. Unlike Example 2, the lack of a halide salt reaction rate control agent resulted in the formation of more silver nanoparticles in the product.

[0086] Example 2

[0087] Based on Example 1, solutions with mass concentrations of 30 mg / ml tannin, 500 mg / ml dodecyl dimethylamine oxide, 10 mg / ml sodium chloride, and 800 mg / ml silver nitrate were prepared using a mixed solution of ethanol and water in a 3:1 ratio. The solutions were stirred and mixed thoroughly. 1 ml of sodium chloride solution and 10 ml of silver nitrate solution were added to 20 ml of tannin solution and stirred thoroughly. Then, 20 ml of dodecyl dimethylamine oxide solution was added to the mixed solution and stirred thoroughly. The mixture was reacted at 40°C in the dark for 4 hours with stirring. The solution gradually changed from colorless to light yellow, and finally to gray, with the formation of flocculent substances. The reaction product was centrifuged at 6000 r / min and washed with water. This process was repeated once. The reaction product was redispersed using 15 ml of ethanol to obtain a concentrated silver nanowire solution. The concentrated silver nanowire solution was vacuum dried at 60°C for 15 hours and finally pulverized using an air jet mill to obtain silver nanowire powder.

[0088] Depend on Figure 18-21 As can be seen, the product obtained in this example is a silver nanowire with uniform size, no obvious particulate impurities, ultra-fine diameter (20-40 nm), curled ends, and internal defects. The curled ends and internal defects of the silver nanowires obtained in this example may be related to the special reaction mechanism of this method.

[0089] Example 3

[0090] Based on Example 1, aqueous solutions of caffeic acid (20 mg / ml), gum arabic (100 mg / ml), potassium chloride (5 mg / ml), and silver acetate (70 mg / ml) were prepared and stirred until homogeneous. 1 ml of sodium chloride solution and 10 ml of silver acetate solution were added to 20 ml of caffeic acid solution and stirred until homogeneous. Then, 20 ml of gum arabic solution was added to the above mixture and stirred until homogeneous. The mixture was reacted at 25°C in the dark for 6 hours. The solution gradually changed from colorless to light yellow, and finally to gray, with the formation of flocculent substances. The reaction product was centrifuged at 5500 rpm and washed with water. This process was repeated once. The reaction product was redispersed with 15 ml of ethanol to obtain a concentrated silver nanowire solution. The concentrated silver nanowire solution was vacuum dried at 50°C for 12 hours and finally pulverized using an air jet mill to obtain silver nanowire powder.

[0091] Depend on Figure 22 As can be seen, the product obtained in this example is silver nanowires with uniform size, no obvious particulate impurities, and curled ends. The curling of the ends of the silver nanowires obtained in this example may be related to the special reaction mechanism of this method.

[0092] Example 4

[0093] Based on Example 1, aqueous solutions with mass concentrations of 15 mg / ml p-hydroxybenzoic acid, 100 mg / ml dodecylamine, 0.2 mg / ml sodium chloride, and 10 mg / ml silver nitrate were prepared and stirred until homogeneous. 1 ml of sodium chloride solution and 10 ml of silver nitrate solution were added sequentially to 20 ml of p-hydroxybenzoic acid solution and stirred until homogeneous. Then, 10 ml of dodecylamine solution was added to the above mixture. The mixture was reacted at 65°C under stirring in the dark for 3 hours. The solution gradually changed from colorless to light yellow, and finally to gray, with the formation of flocculent substances. The reaction product was centrifuged at 4500 r / min and washed with water. This process was repeated twice. The reaction product was redispersed with 10 ml of ethanol to obtain a concentrated silver nanowire solution. The concentrated silver nanowire solution was vacuum dried at 80°C for 8 hours, and finally, silver nanowire powder was obtained by air jet milling.

[0094] Depend on Figure 23 As can be seen, the products obtained in this example are silver nanowires and silver nanoparticles distributed in a granular manner.

[0095] Comparative Example 5

[0096] Based on Example 1, the difference in this comparative example is that the reducing agent used is the ineffective supramolecular assembly agent 4-methylcatechol. Aqueous solutions of 2.5 mg / ml 4-methylcatechol, 8 mg / ml polyvinylpyrrolidone, 0.1 mg / ml sodium chloride, and 2 mg / ml silver nitrate were prepared and stirred until homogeneous. 0.5 ml of sodium chloride solution and 10 ml of silver nitrate solution were added sequentially to 20 ml of 4-methylcatechol solution and stirred until homogeneous. Then, 5 ml of polyvinylpyrrolidone solution was added to the above mixture and stirred until homogeneous. The mixture was reacted at 60°C for 2 hours with stirring. The reaction product was centrifuged at 4000 rpm and washed with water. This process was repeated twice. The reaction product was redispersed using 10 ml of ethanol to obtain a concentrated product solution. The concentrated solution was dropped onto a silicon wafer for SEM characterization.

[0097] Depend on Figure 24 As can be seen, the product obtained in this comparative example is irregularly shaped silver nanoparticles, with no silver nanowires generated. This is because an ineffective supramolecular assembling agent was used; this component could not participate in supramolecular assembly with silver ions to form coordination polymers, but only acted as a reducing agent, thus failing to generate silver nanowires.

[0098] Comparative Example 6

[0099] Based on Example 1, the difference in this comparative example is that melamine, a non-active ingredient, is used instead of the supramolecular assembling agent in Example 1. Aqueous solutions of melamine (2.5 mg / ml), polyvinylpyrrolidone (8 mg / ml), sodium chloride (0.1 mg / ml), and silver nitrate (2 mg / ml) were prepared and mixed thoroughly. 0.5 ml of sodium chloride solution and 10 ml of silver nitrate solution were added sequentially to 20 ml of melamine solution and mixed thoroughly. Then, 5 ml of polyvinylpyrrolidone solution was added to the above mixture and mixed thoroughly. The mixture was reacted at 60°C for 2 hours with stirring. The reaction product was centrifuged at 4000 rpm and washed with water. This process was repeated twice. The reaction product was redispersed using 10 ml of ethanol to obtain a concentrated product solution. The concentrated solution was dropped onto a silicon wafer for SEM characterization.

[0100] Depend on Figure 25-27 The SEM results show a clear charging phenomenon. Combined with the XRD results, the product obtained in this comparative example is a one-dimensional silver ion-melamine supramolecular self-assembly polymer, without the formation of silver nanowires. Because an ineffective supramolecular assembly agent was used, although this component can participate in supramolecular assembly with silver ions to form a coordination polymer, melamine lacks a reducing agent and therefore cannot generate silver nanowires.

[0101] Comparative analysis of the SEM and XRD results of the examples and comparative examples reveals that the synergistic effect of the halide salt reaction rate controller, the dual function of the supramolecular assembly agent as both a template and a reducing agent, and the guiding role of the polymer protectant successfully achieved the synthesis of silver nanowires. A schematic diagram of the reaction mechanism is shown below. Figure 28 As shown. The silver nanowires prepared in the above embodiments have ultra-fine diameters of 20-50 nm, with curled ends and internal defects; the preparation method has high production capacity per unit volume of reaction solution (80 g-100 g / L), ultra-low reaction temperature, and can be carried out in water, making the process simple and more environmentally friendly.

[0102] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing silver nanowires mediated by metal-organic coordination polymers, characterized in that: Includes the following steps: Step S1: Prepare supramolecular assembling agent, polymer protectant, halide salt, and soluble silver salt solution, which have dual functions of reduction and coordination polymerization; the supramolecular assembling agent is at least one of cinnamic acid, tannin, p-hydroxybenzoic acid, and caffeic acid. Step S2: The halide salt and supramolecular assembly agent are sequentially added to a soluble silver salt solution to form a silver ion-supramolecular assembly agent coordination polymer solution. The formed silver ion-supramolecular assembly agent coordination polymer exhibits a near-one-dimensional structure in the form of long strips or bands. A polymeric protective agent is added to the silver ion-supramolecular assembly agent coordination polymer solution, and the mass ratio of the supramolecular assembly agent, silver salt, halide salt, and polymeric protective agent in the solution is (24-30):10:(0.01-2):(80-120). Then, the mixture is stirred and reacted in the dark at 25-65℃ for 2-5 hours. Step S3: After the reaction is completed, centrifugation and washing are performed to obtain the reaction product. The reaction product is then redispersed and vacuum dried to obtain silver nanowires. The silver nanowires have a diameter of 20-50 nm and have a curled end.

2. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 1, characterized in that: The polymer protective agent is one or a mixture of two or more of the following: gelatin, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, triethylhexylphosphate, sodium lauryl sulfate, methylpentanol, polyacrylamide, polyethyleneimine, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium lauryl sulfonate, and sodium laurylbenzene sulfonate. The halide salt reaction rate control agent is one or a mixture of two or more of the following: sodium chloride, sodium bromide, potassium chloride, potassium bromide, copper chloride, copper bromide, ferric chloride, ferrous chloride, ferric bromide, ferrous bromide, cobalt chloride, cobalt bromide, zinc chloride, zinc bromide, zinc chloride, and zinc bromide. The soluble silver salt is one or a mixture of two or more of the following: silver chloride, silver sulfate, silver carbonate, silver nitrite, silver acetate, silver sulfate, silver fluoride, silver chlorate, silver perchlorate, silver nitrate, silver perbromate, silver periodate, silver bicarbonate, silver sulfide, silver gluconate, and silver cyanate. The solvent for the soluble silver salt solution is at least one of water, alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide.

3. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 1, characterized in that: In step S2, the stirring speed is 20-500 r / min.

4. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 1, characterized in that: In step S3, the centrifugation speed is 1000-7000 r / min, the number of centrifugal washing cycles is 1-4, and the vacuum drying temperature is 50-80℃.

5. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 4, characterized in that: In step S3, the vacuum drying temperature is 30-80℃ and the vacuum drying time is 1-20h; after vacuum drying, silver nanowire powder is obtained by air jet pulverization.

6. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 1, characterized in that: In step S3, the reaction product is redispersed using an organic solvent, which includes one or more of the following: alcohol solvents, ether solvents, benzene solvents, ketone solvents, ester solvents, alkane solvents, halogenated hydrocarbon solvents, ether alcohol solvents, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide.

7. The method for preparing silver nanowires mediated by metal-organic coordination polymers according to claim 6, characterized in that: The mass concentration of the soluble silver salt solution is 0.1-1000 mg / ml.

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