Preparation method of metal organic coordination polymer mediated silver nanowire

Abstract

The invention provides a preparation method of a metal organic coordination polymer mediated silver nanowire. The preparation method comprises the following steps: respectively preparing a supramolecular assembly agent, a high-molecular polymer protective agent, halide salt and a soluble silver salt solution; the supramolecular assembly agent is at least one of cinnamic acid, p-coumaric acid, caffeic acid, tannin and the like; halide salt and a supramolecular assembly agent are sequentially added into the soluble silver salt solution to form a silver ion-supramolecular assembly agent coordination polymer solution; adding a high-molecular polymer protective agent into the silver ion-supramolecular assembly agent coordination polymer solution, stirring, and reacting in a dark place at-20 to 80 DEG C for 0.1 to 10 hours; and after the reaction is completed, centrifuging, washing, drying in vacuum and re-dispersing to obtain the silver nanowire. According to the technical scheme, the prepared silver nanowire is superfine in diameter, the end has a curled shape, the interior contains defects, the reaction can be carried out in water, the productivity is high and is larger than 80 g / L, and the technology is simple and more environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of nanomaterials, and in particular to a method for preparing silver nanowires mediated by a metal organic coordination polymer. Background Art

[0002] At present, the preparation methods of silver nanowires mainly include template method, wet chemical method, ultraviolet light induction method, polyol method, solvothermal method, hydrothermal method, etc. Template method is divided into hard template and soft template method. The morphology and aspect ratio of silver nanowires are controlled by prefabricated templates. The removal of hard templates is more complicated, and the morphology of silver nanowires is poorly controlled by soft templates. The wet chemical method uses reducing agents such as sodium citrate, ascorbic acid, sodium borohydride, etc. to reduce the silver source into silver nanowires. The reaction process is sensitive and the reaction products are often poorly dispersed. In the ultraviolet light induction method, only reactants that are in contact with ultraviolet light can react, and uneven reactions are prone to occur. Polyol method, solvothermal method and hydrothermal method have been proven to be synthetic methods with high yield and good morphological control. However, polyol method often uses organic reagents such as ethylene glycol and propylene glycol that are harmful to the environment as solvents and reducing agents. Both methods need to be heated to a higher temperature, especially hydrothermal method or solvothermal method. The reaction is difficult to scale up in a closed reactor, which further restricts its application in industry. Moreover, the quality of the silver nanowires obtained by the above method needs to be improved. Therefore, it is urgent to develop a method for synthesizing silver nanowires that is environmentally friendly, has mild reaction conditions, controllable quality, high efficiency, and high productivity. Summary of the invention

[0003] In view of the above technical problems, the present invention discloses a method for preparing silver nanowires mediated by a metal organic coordination polymer. The obtained silver nanowire products are uniform, ultra-fine in diameter (20-50nm), have a curled morphology at the ends, contain defects inside, have high production capacity (80g-100 / L), and have an ultra-low reaction temperature. Moreover, the reaction can be carried out in water, and the process is simple and more environmentally friendly.

[0004] To this end, the technical solution adopted by the present invention is:

[0005] A method for preparing silver nanowires mediated by a metal organic coordination polymer comprises the following steps:

[0006] Step S1, respectively preparing a supramolecular assembly agent with dual functions of reduction and coordination polymerization, a high molecular polymer protective agent, a halide reaction rate control agent, and a soluble silver salt solution; the supramolecular assembly agent is one or a mixture of two or more of cinnamic acid, p-coumaric acid, caffeic acid, rosmarinic acid, gallic acid, sinapinic acid, protocatechuic acid, salicylic acid, benzoic acid, p-hydroxybenzoic acid, resveratrol, isodanin, piceatannol, coumarin, osthole, esculetin, angelica lactone, aporphine, erythrosine, chelidonine, tannin, and azafluoranthene;

[0007] Step S2, respectively, adding a halide salt and a supramolecular assembly agent to a soluble silver salt solution in sequence to form a silver ion-supramolecular assembly agent coordination polymer solution; adding a polymer protective agent to the silver ion-supramolecular assembly agent coordination polymer solution of step S2, wherein the mass ratio of the supramolecular assembly agent, the silver salt, the halide salt, and the polymer protective agent is (0.1-150): (0.1-100): (0.01-10): (1-600); then stirring, and reacting at a temperature of -20-80°C in the dark for 0.1-10h;

[0008] Step S3, after the reaction is completed, centrifugation and washing are performed to obtain the reaction product, and the reaction product is redispersed and vacuum dried to obtain silver nanowires.

[0009] The generation of silver nanowires is generally divided into a nucleation and directional growth process. Different from the previously disclosed generation process of silver nanowires, in the technical solution of the present invention, with the addition of a soluble silver salt solution, the supramolecular assembler and the halide salt reaction rate controller will play a role, and the generated silver halide will slowly release the silver ions through slow ionization, and the supramolecular assembler will first form a silver ion-supramolecular assembler coordination polymer with the silver ions through coordination and complexation. The coordination polymer is a metal organic metal framework structure, and the formed silver ion-supramolecular assembler coordination polymer presents a long strip or ribbon-shaped nearly one-dimensional structure. The silver ion-supramolecular assembler coordination polymer plays a role as a template in the growth process of the silver nanowires. It is this one-dimensional structure that fixes the silver ions along a one-dimensional direction, laying the foundation for the silver ions to be reduced to silver atoms and then qualitatively arranged to grow into silver nanowires in the later stage. Subsequently, the supramolecular assembler plays the role of a reducing agent, and the silver atoms anchored in the silver ion-supramolecular assembler coordination polymer and arranged in a one-dimensional direction are reduced in situ by the supramolecular assembler, and the reduced silver atoms will attract the silver-philic groups (such as O, N) in the molecular structure of the polymer protective agent. Specifically, the outer layer of the silver ion-supramolecular assembler coordination polymer will adsorb a layer of polymer protective agent where the silver atoms are generated. Due to the steric hindrance between the polymers, the in-situ reduced silver atoms can be effectively wrapped to prevent the deposition of other silver atoms. As the reduction reaction proceeds, the silver atoms are accumulated along the one-dimensional structure of the silver ion-supramolecular assembler coordination polymer until the silver nanowires are generated, that is, the silver ions and the supramolecular assembler will be separated from the silver ion-supramolecular assembler coordination polymer framework, the silver ions become silver atoms and participate in the growth process of the silver nanowires, and the supramolecular assembler will be oxidized to become oxidation products.

[0010] In the technical solution of the present invention, a supramolecular assembling agent is used to work synergistically with a halide salt and a high molecular polymer protective agent:

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

[0012] Secondly, the supramolecular assembler with dual functions plays the role of template and reducing agent. This supramolecular assembler can well react with silver ions through coordination complexation to generate a one-dimensional or nearly one-dimensional structure of silver ion-supramolecular assembler coordination polymer template. The generation of this coordination polymer ensures that the silver ions in the reaction solution are no longer randomly distributed, but are orderly anchored by the coordination polymer into a one-dimensional directional arrangement, which lays a structural foundation for the directional deposition of silver atoms. Subsequently, the active groups in the supramolecular assembler play the role of reducing agent, which can slowly reduce the silver ions into silver atoms in situ.

[0013] Thirdly, the guiding role of the polymer protective agent. The outer electron configuration of the active groups (such as O and N) in the polymer protective agent is in a full electron configuration state, and there are empty orbitals without electrons in the atomic structure of the silver atom. Therefore, the outer electrons of O or N will be filled into the empty electron orbitals of the silver atom, which conforms to the lowest energy state. This is manifested in that the outer layer of the silver ion-supramolecular assembler coordination polymer will adsorb a layer of polymer protective agent where silver atoms are generated. At the same time, because polymers often have longer molecular chains, due to the effect of steric hindrance, the in-situ reduced silver atoms can be effectively wrapped, and the deposition of other silver atoms can be avoided.

[0014] In summary, the technical solution of the present invention benefits from the reaction rate controlling effect of the halide reaction rate controller, the dual functions of the template and reducing agent played by the supramolecular assembler, and the guiding effect of the high molecular polymer protective agent. The synergistic effect of the three successfully realizes the synthesis of silver nanowires.

[0015] As a further improvement of the present invention, the polymer protective agent is one or a mixture of two or more of gelatin, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methyl amyl alcohol, polyacrylamide, guar gum and polyethylene glycol fatty acid ester, polyethylene imine, hexadecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate. Further preferably, the polymer protective agent is polyvinyl pyrrolidone.

[0016] As a further improvement of the present invention, the halide salt reaction rate controller is one or a mixture of two or more of sodium chloride, sodium bromide, potassium chloride, potassium bromide, cupric chloride, cupric bromide, ferric chloride, ferrous chloride, ferrous 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 perbromide, silver periodate, silver bicarbonate, silver sulfide, silver gluconate and silver cyanate. Further 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 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. Further 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, in step S2, the reaction temperature is 0-65°C, preferably 0.5-6h. Further preferably, in step S2, the reaction temperature is 25-65°C, and the reaction time is 2-5h.

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

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

[0023] As a further improvement of the present invention, in step S3, air flow pulverization is used after vacuum drying to obtain silver nanowire powder.

[0024] As a further improvement of the present invention, in step S3, the reaction product is redispersed using an organic solvent, and the organic solvent includes one or more of an alcohol solvent, an ether solvent, a benzene solvent, a ketone solvent, an ester solvent, an alkane solvent, a halogenated hydrocarbon solvent, an ether alcohol solvent, tetrahydrofuran, acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide. Further 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 the polymer protective agent is added in step S2, the mass ratio of the supramolecular assembly agent, silver salt, halide salt, and polymer protective agent is (24-30):10:(0.01-2):(80-120). Further preferably, in the solution after the polymer protective agent is added in step S2, the mass ratio of the supramolecular assembly agent, silver salt, halide salt, and polymer protective agent 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 assembly agent is at least one of cinnamic acid, tannin, p-hydroxybenzoic acid and caffeic acid.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] First, the technical solution of the present invention adopts a halide salt as a reaction rate controller, a supramolecular assembler that has a certain reduction effect and can form a coordination polymer by supramolecular assembly with silver ions as a reducing agent and a template agent, and a high molecular polymer as a protective agent. The synergistic effect of the three is utilized to overcome the disadvantage that the nucleation growth process of the water-based solution is difficult to control, and the silver source is reduced to high-quality silver nanowires under mild conditions. The prepared silver nanowire products are uniform, have ultra-fine diameters (20-50nm), have curled morphology at the ends, and contain defects inside.

[0030] Second, the technical solution of the present invention adopts a one-pot one-step reduction technology, which greatly improves the reaction efficiency. The required equipment is simple and the operation is simple. It does not require inert gas protection, high temperature and high pressure and other harsh reaction conditions, and avoids the introduction of organic solvents that are harmful to the environment. It greatly reduces the tediousness of later purification, improves production efficiency, and effectively reduces production costs. The unit volume production capacity of silver nanowires is high (80g-100 / L), which is suitable for large-scale production and has good application prospects.

[0031] Thirdly, the supramolecular assembler of the technical solution of the present invention uses phytochemical components extracted from plants, and the reaction solvent is not limited to traditional organic solutions, but can be a water-based solution, which has little toxic effect on the environment and is more in line with the requirements of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The schematic diagram of the reaction process of Example 1 of the present invention.

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

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

[0035] Figure 6 This is the XRD result of the silver nanowires prepared in Example 1 of the present invention.

[0036] Figure 7 and Figure 8 SEM results of silver nanowires prepared in Comparative Example 1 of the present invention at different magnifications.

[0037] Fig. 9 and Fig.10 These are SEM results of different magnifications of the intermediate process sampling material of Comparative Example 2 of the present invention.

[0038] Fig.11 This is the XRD result of the sampled material in the intermediate process of Comparative Example 2 of the present invention.

[0039] Fig.12 and Fig.13 SEM results of silver nanowires prepared in Comparative Example 2 of the present invention at different magnifications.

[0040] Fig.14 and Fig.15 These are SEM results of different magnifications of the intermediate process sampling material of Comparative Example 3 of the present invention.

[0041] Fig.16 This is the XRD result of the sampled material in the intermediate process of Comparative Example 3 of the present invention.

[0042] Fig.17 This is the SEM result of silver nanowires prepared in Comparative Example 3 of the present invention.

[0043] Fig.18 and Fig.19 The SEM results of silver nanowires prepared in Example 2 of the present invention at different magnifications.

[0044] Fig. 20 and Fig.21 These are SEM images of TEM results of a single silver nanowire prepared in Example 2 of the present invention at different magnifications.

[0045] Fig. 22 This is the SEM image result of the product prepared in Example 3 of the present invention.

[0046] Fig.23 This is the SEM result of the product prepared in Example 4 of the present invention.

[0047] Fig.24 This is the SEM result of the product prepared in Comparative Example 5 of the present invention.

[0048] Fig.25 and Fig.26 These are SEM results of different magnifications of the product prepared in Comparative Example 6 of the present invention.

[0049] Fig. 27 It is the XRD result of the product prepared in Comparative Example 6 of the present invention.

[0050] Fig.28 This is a reaction mechanism analysis diagram of the silver nanowire preparation method of the present invention. DETAILED DESCRIPTION

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

[0052] A method for preparing silver nanowires mediated by a metal organic coordination polymer, such as Figure 1 As shown, the following steps are included:

[0053] Step S1, respectively preparing a solution of a supramolecular assembly agent having dual functions of reduction and coordination polymerization, a high molecular polymer protective agent, a halide reaction rate control agent, and a soluble silver salt, and stirring and mixing them uniformly for later use;

[0054] Step S2, respectively adding a halide salt and a supramolecular assembly agent into a soluble silver salt solution in sequence to form a silver ion-supramolecular assembly agent coordination polymer;

[0055] Step S3, adding a high molecular polymer protective agent to the solution of step S2, and reacting in the dark;

[0056] Step S4, centrifugally separating and washing the reaction product, redispersing the reaction product with an organic solvent to obtain a silver nanowire concentrate, vacuum drying the silver nanowire concentrate, and finally pulverizing with air flow to obtain silver nanowire powder.

[0057] In the step S1, a supramolecular assembler having dual functions of reduction and coordination polymerization, a high molecular polymer protective agent, a halide 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 the supramolecular assembly agent, high molecular polymer protective agent, halide salt reaction rate controller, and soluble silver salt solution 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 assembly agent includes, but is not limited to, one or more of cinnamic acid, p-coumaric acid, caffeic acid, rosmarinic acid, gallic acid, sinapinic acid, protocatechuic acid, salicylic acid, benzoic acid, p-hydroxybenzoic acid, resveratrol, isodanin, piceatannol, coumarin, osthole, esculetin, angelica lactone, aporphine, erythrosine, chelidonine, tannin, and azafluoranthene. The selection of such supramolecular assembly agents is mainly based on aromatic derivatives with benzene rings, and the side chain groups have oxygen-containing groups such as hydroxyl, carbonyl or carboxyl groups, and the supramolecular assembly effect mainly originates from the coordination effect of the lone electron pair of oxygen occupying the empty outer orbit of the silver particle.

[0060] The polymer protective agent includes, but is not limited to, one or more of gelatin, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, triethylhexyl phosphoric acid, sodium dodecyl sulfate, methyl amyl alcohol, polyacrylamide, guar gum and polyethylene glycol esters of fatty acids, polyethylene imine, cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; preferably, one or more of gelatin, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; further preferably, one or more of gelatin, gum arabic, polyvinyl alcohol, and polyvinyl pyrrolidone.

[0061] The halide salt reaction rate controller includes but is not limited to one or more of sodium chloride, sodium bromide, potassium chloride, potassium bromide, cupric chloride, cupric bromide, ferric chloride, ferrous chloride, ferrous 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, cupric chloride, and cupric 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 perbromide, 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 perbromide, silver bicarbonate, silver gluconate and silver cyanate, and further preferably any one of silver chloride, silver sulfate, silver carbonate, silver acetate, silver sulfate, silver chlorate, silver nitrate, silver perbromide, silver bicarbonate, silver gluconate and silver cyanate.

[0063] In the solution of step S3, the mass ratio of the supramolecular assembly agent, silver salt, halide salt, and polymer protective agent is (0.1-150): (0.1-100): (0.01-10): (1-600); further preferably, the mass ratio of the supramolecular assembly 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 reaction rate controller 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 assembly agent, the high molecular polymer protective agent, the halide reaction rate controller, and the 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°C, preferably 0-60°C; the reaction time is 0.1-10h, preferably 0.5-6h; the stirring speed is 20-500r / min, preferably 50-300r / min. More preferably, the reaction temperature is 25-65°C, and the reaction time is 2-6h. More preferably, the reaction temperature is 40-65°C, and the reaction time is 2-5h.

[0067] In the 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 air flow pulverized to obtain silver nanowire powder.

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

[0069] The organic solvent used for the dispersed silver nanowire concentrate includes, but is not limited to, one or a mixture of two 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, N,N-dimethylformamide; preferably one or more of ethanol, isopropanol, and n-hexane.

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

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

[0072] Example 1

[0073] Aqueous solutions with mass concentrations of 2.5 mg / ml cinnamic acid, 20 mg / ml polyvinyl pyrrolidone, 0.1 mg / ml sodium chloride and 2 mg / ml silver nitrate were prepared respectively, stirred and mixed evenly for use; 0.5 ml sodium chloride solution and 10 ml silver nitrate solution were added to 20 ml cinnamic acid solution respectively, stirred and mixed evenly, and then 9 ml polyvinyl pyrrolidone solution was added to the above mixed solution, and reacted at 60° C. under stirring conditions for 2 hours, the solution gradually changed from colorless to light yellow, and finally gradually changed to gray, and flocculent substances were produced; the reaction product was centrifuged and washed with water at a speed of 4000 r / min, and the above steps were repeated twice, and the reaction product was redispersed with 10 ml ethanol to obtain a silver nanowire concentrate, the silver nanowire concentrate was vacuum dried at 70° C. for 10 hours, and finally the silver nanowire powder was obtained by air flow pulverization.

[0074] Depend on Figure 2-6It can be obtained that the product obtained in this example is a silver nanowire with uniform size, no obvious granular impurities, ultra-fine diameter (20-40nm), curled morphology at the end, and defects inside. The curling of the silver nanowire ends and the internal defects obtained in this example may be related to the special reaction mechanism of this method. Due to the coordination and complexation between the supramolecular assembly agent and the original silver ions, the distribution of silver ions in the solution is transformed from random distribution to one-dimensional directional arrangement. When the active groups in the supramolecular assembly agent play the role of the reducing agent, the silver ions are slowly reduced to silver atoms in situ, and the silver atoms are stacked together in layers, so the TEM results show a layered contrast image with light and dark interlaced. It is also this special reaction mechanism that may cause the silver nanowire ends synthesized by this method to have a curled structure and internal defects.

[0075] Comparative Example 1

[0076] Based on Example 1, the difference of this comparative example is that no halide reaction rate controller is added during the preparation process. Prepare aqueous solutions with mass concentrations of 2.5 mg / ml cinnamic acid, 8 mg / ml polyvinyl pyrrolidone, and 2 mg / ml silver nitrate, stir and mix them evenly for use; add 10 ml of silver nitrate solution to 20 ml of cinnamic acid solution, stir and mix evenly, then add 5 ml of polyvinyl pyrrolidone solution to the above mixed solution, and react for 2 hours under stirring conditions at 60°C; centrifuge and wash the reaction product at a speed of 4000 r / min, repeat the above steps twice, use 10 ml of ethanol to redisperse the reaction product to obtain a concentrated solution of the product, and drop the concentrated solution on a silicon wafer for SEM characterization to obtain the results.

[0077] Figure 7-8 The product obtained in this comparative example is nano silver particles of uneven size and shape, and no silver nanowires are generated. In this comparative example, no halide salt is added as a reaction rate controller, and more silver ion-supramolecular assembly agent coordination polymer intermediates are formed, and more silver atoms are reduced in a short time. Due to the adsorption of the high molecular polymer protective agent on silver atoms, when there are more silver atoms, the silver atoms are oriented along the one-dimensional direction and aggregated to generate silver nanoparticles. From the results of the scanning electron microscope, it can be seen that the growth mode of the silver particles is similar to that of condensation from the surrounding.

[0078] Comparative Example 2

[0079] The method is based on Example 1, except that no polymer protective agent is added during the preparation process, and aqueous solutions with mass concentrations of 2.5 mg / ml cinnamic acid, 0.1 mg / ml sodium chloride, and 2 mg / ml silver nitrate are prepared respectively, stirred and mixed evenly for use; then 0.5 ml of sodium chloride solution and 10 ml of silver nitrate solution are added to 20 ml of cinnamic acid solution in sequence, stirred and mixed evenly, and reacted at 60° C. for 2 h; the reaction product is centrifuged and washed at a speed of 4000 r / min, the above steps are repeated twice, and the reaction product is re-dispersed with 10 ml of ethanol to obtain a concentrated solution of the product, and the concentrated solution is dropped on a silicon wafer for SEM characterization to obtain the result.

[0080] Figure 9-11 The results of sampling in the middle of the reaction for 30 minutes after the start of the reaction in this embodiment are obtained. The obtained products are silver ion-supramolecular assembly agent coordination polymer, silver halide and a small amount of nano silver particles. The long strip product is a one-dimensional structure of 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 square products are the generated silver halide; the granular products distributed in a dotted manner on the surface of the coordination polymer, which is a complex component of the silver ion-supramolecular assembly agent and Ag ions, are nano silver particles generated by in-situ reduction of the supramolecular assembly agent; only a small amount of silver nanowires are produced in the product, and the dispersibility is 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 ion coordination polymer, silver halide and a small amount of nano silver particles, also generates mutually entangled silver nanobelts and silver nanoplates with uneven size distribution, wherein the entangled objects in the form of threads or bands are generated silver nanobelts, and the products in the form of triangles or hexagons are silver nanoplates. The generation of silver nanobelts is also related to the fact that the silver ion-supramolecular assembly agent coordination polymer anchors the original silver ions in a one-dimensional structure, but because of the lack of the effect of the polymer protective agent, the silver atoms are reduced in one-dimensional direction but are not effectively protected, and the probability of collision with other silver atoms increases, generating silver nanobelt structures and silver nanoplates with poor morphology, and the extension of the reaction time may be related to the balance of the chemical reaction, because the lack of the effect of the polymer protective agent makes it impossible for the silver atoms reduced in situ to be removed from the silver ion-supramolecular assembly agent coordination polymer system, and the high concentration of silver atoms in the coordination polymer will reduce the chemical reaction rate of the reduction reaction, and increase the reaction time.

[0082] Comparative Example 3

[0083] Based on Example 1, the difference of this comparative example is that no halide reaction rate controller and high molecular polymer protective agent are added during the preparation process. Prepare aqueous solutions with mass concentrations of 2.5 mg / ml cinnamic acid and 2 mg / ml silver nitrate respectively, stir and mix evenly for use; then add 10 ml of silver nitrate solution to 20 ml of cinnamic acid solution in sequence, stir and mix evenly, and react at 60°C for 2 hours; centrifuge and wash the reaction product at a speed of 4000 r / min, repeat the above steps twice, use 10 ml of ethanol to redisperse the reaction product to obtain a concentrated solution of the product, and drop the concentrated solution on a silicon wafer for SEM characterization to obtain the results.

[0084] Figure 14-16 The results of sampling in the middle of the reaction 30 minutes after the start of the reaction in this embodiment are obtained. The products obtained in this embodiment are silver ion-supramolecular assembly agent coordination polymer and a small amount of nano silver particles. The long strip product is a complex component coordination polymer of silver ion-supramolecular assembly agent and Ag ion, which has poor conductivity and appears charged when observed under a scanning electron microscope; the long strip product is the silver ion-supramolecular assembly agent coordination polymer, and the point-shaped product distributed on the surface is the generated nano silver particles; there are no silver nanowires in the product. The reasons for the generation of silver ion-supramolecular assembly agent coordination polymer and silver nano particles are the same as those in Example 2.

[0085] Fig.17 The product obtained in this embodiment is a silver nanobelt entangled with each other and a silver nanoplate with uneven size distribution, wherein the filamentous or ribbon-shaped entanglements are the generated silver nanobelts, and the triangular or hexagonal products are silver nanoplates; only a small amount of silver nanowires are produced in the product, and the dispersion is poor. The reasons for the appearance of the product and the extension of the reaction time are the same as those in Example 2. Unlike Example 2, this comparative example also does not add a high molecular polymer protective agent but generates a small amount of entangled silver nanobelts, because although the addition of a halide salt reaction rate controller is lacking, the generated silver atoms are not subject to the adsorption effect of the high molecular polymer protective agent on the in-situ reduced silver atoms, and a small amount of silver atoms can also be deposited along a one-dimensional direction to generate nearly one-dimensional silver nanobelts. Unlike Example 2, due to the lack of the effect of the halide salt reaction rate controller, more silver nanoparticles are generated in the generated product.

[0086] Example 2

[0087] On the basis of Example 1, solutions with mass concentrations of 30 mg / ml tannin, 500 mg / ml dodecyl dimethyl amine oxide, 10 mg / ml sodium chloride, and 800 mg / ml silver nitrate were prepared respectively, the solvent was a mixed solution of ethanol and water, the ratio of ethanol to water was 3:1, and the mixture was stirred and mixed for use; 1 ml of sodium chloride solution and 10 ml of silver nitrate solution were added to 20 ml of tannin solution respectively, and the mixture was stirred and mixed evenly, and then 20 ml of dodecyl dimethyl amine oxide solution was added to the above mixed solution, and the mixture was stirred and mixed evenly, and the mixture was reacted at 40° C. in the dark for 4 hours, and the solution gradually changed from colorless to light yellow, and finally gradually changed to gray, and flocculent substances were produced; the reaction product was centrifuged and washed with water at a speed of 6000 r / min, and the above steps were repeated once, and 15 ml of ethanol was used to redisperse the reaction product to obtain a silver nanowire concentrate, and the silver nanowire concentrate was vacuum dried at 60° C. for 15 hours, and finally pulverized by air flow to obtain a silver nanowire powder.

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

[0089] Example 3

[0090] On the basis of Example 1, aqueous solutions with mass concentrations of 20 mg / ml caffeic acid, 100 mg / ml gum arabic, 5 mg / ml potassium chloride, and 70 mg / ml silver acetate were prepared respectively, stirred and mixed evenly for use; 1 ml of sodium chloride solution and 10 ml of silver acetate solution were added to 20 ml of caffeic acid solution respectively, stirred and mixed evenly, and then 20 ml of gum arabic solution was added to the above mixed solution, stirred and mixed evenly, and reacted in the dark at 25° C. for 6 hours, the solution gradually changed from colorless to light yellow, and finally gradually changed to gray, and flocculent substances were produced; the reaction product was centrifuged and washed at a speed of 5500 r / min, and the above steps were repeated once, and the reaction product was redispersed with 15 ml of ethanol to obtain a silver nanowire concentrate, the silver nanowire concentrate was vacuum dried at 50° C. for 12 hours, and finally pulverized by air flow to obtain silver nanowire powder.

[0091] Depend on Fig. 22 It can be seen that the product obtained in this example is a silver nanowire with uniform size, no obvious granular 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] On the basis of 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 respectively, stirred and mixed evenly for use; 1 ml of sodium chloride solution and 10 ml of silver nitrate solution were added to 20 ml of p-hydroxybenzoic acid solution in sequence, stirred and mixed evenly, and then 10 ml of dodecylamine solution was added to the above mixed solution, and the mixture was reacted at 65° C. in the dark for 3 h, and the solution gradually changed from colorless to light yellow, and finally gradually changed to gray, and flocculent substances were produced; the reaction product was centrifuged and washed with water at a speed of 4500 r / min, and the above steps were repeated twice, and the reaction product was redispersed with 10 ml of ethanol to obtain a silver nanowire concentrate, the silver nanowire concentrate was vacuum dried at 80° C. for 8 h, and finally pulverized with air flow to obtain silver nanowire powder.

[0094] Depend on Fig.23 It can be seen that the products obtained in this example are silver nanowires and silver nanoparticles distributed in granular form.

[0095] Comparative Example 5

[0096] Based on Example 1, the difference of this comparative example is that the reducing agent uses a non-effective supramolecular assembly agent 4-methylcatechol. Prepare aqueous solutions of 4-methylcatechol with a mass concentration of 2.5 mg / ml, 8 mg / ml polyvinyl pyrrolidone, 0.1 mg / ml sodium chloride, and 2 mg / ml silver nitrate respectively, stir and mix evenly for use; add 0.5 ml sodium chloride solution and 10 ml silver nitrate solution to 20 ml 4-methylcatechol solution in turn, stir and mix evenly, then add 5 ml polyvinyl pyrrolidone solution to the above mixed solution, stir and mix evenly, and react at 60°C for 2 hours; centrifuge the reaction product at a speed of 4000 r / min and wash it with water, repeat the above steps twice, use 10 ml ethanol to redisperse the reaction product to obtain a concentrated solution of the product, and drop the concentrated solution on a silicon wafer for SEM characterization to obtain the results.

[0097] Depend on Fig.24 It can be seen that the product obtained in this comparative example is irregularly shaped nanosilver particles, and no silver nanowires are generated. Because an ineffective supramolecular assembly agent is used, this component cannot play a supramolecular assembly with silver ions to form a coordination polymer, but only plays a role of a reducing agent, so no silver nanowires can be generated.

[0098] Comparative Example 6

[0099] Based on Example 1, the difference of this comparative example is that the non-effective ingredient melamine is used to replace the supramolecular assembly agent of Example 1. Melamine, 8mg / ml polyvinyl pyrrolidone, 0.1mg / ml sodium chloride, and 2mg / ml silver nitrate aqueous solutions with a mass concentration of 2.5mg / ml are respectively prepared, stirred and mixed evenly for use; 0.5ml sodium chloride solution and 10ml silver nitrate solution are added to 20ml melamine solution in sequence, stirred and mixed evenly, and then 5ml polyvinyl pyrrolidone solution is added to the above mixed solution, stirred and mixed evenly, and reacted at 60℃ for 2h; the reaction product is centrifuged and washed at a speed of 4000r / min, and the above steps are repeated twice, and the reaction product is redispersed with 10ml ethanol to obtain a concentrated solution of the product, and the concentrated solution is dropped on a silicon wafer for SEM characterization to obtain the result.

[0100] Depend on Figure 25-27 It can be seen that the SEM results show that the charging phenomenon is obvious. Combined with the XRD results, the product obtained in this comparative example is a one-dimensional silver ion-melamine supramolecular self-assembled coordination polymer, and no silver nanowires are generated. Because a non-effective supramolecular assembly agent is used, although this component can play a supramolecular assembly with silver ions to form a coordination polymer, because melamine does not act as a reducing agent, it cannot generate silver nanowires.

[0101] By comparing and analyzing the SEM and XRD results of the embodiment and the comparative example, it can be found that the reaction rate controlling effect of the halide reaction rate controller, the dual functions of the template agent and the reducing agent played by the supramolecular assembling agent, and the guiding effect of the high molecular polymer protective agent, the synergistic effect of the three successfully achieved the synthesis of silver nanowires. The reaction mechanism diagram is shown in Fig.28 The silver nanowires prepared in the above embodiment have an ultra-fine diameter of 20-50nm, a curled morphology at the end, and defects inside; the preparation method has a high production capacity per unit volume of reaction solution (80g-100 / L), an ultra-low reaction temperature, and can be reacted in water, with a simple process and more environmentally friendly.

[0102] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing silver nanowires mediated by a metal organic coordination polymer, characterized in that: The steps include: Step S1, respectively preparing a supramolecular assembly agent with dual functions of reduction and coordination polymerization, a polymer protective agent, a halide salt, and a soluble silver salt solution; the supramolecular assembly agent is one or a mixture of two or more of cinnamic acid, p-coumaric acid, caffeic acid, rosmarinic acid, gallic acid, sinapinic acid, protocatechuic acid, salicylic acid, benzoic acid, p-hydroxybenzoic acid, resveratrol, isodanin, piceatannol, coumarin, osthole, esculetin, angelica lactone, aporphine, erythrosine, chelidonine, tannin, and azafluoranthene; Step S2, respectively, adding a halide salt and a supramolecular assembly agent to a soluble silver salt solution in sequence to form a silver ion-supramolecular assembly agent coordination polymer solution; adding a polymer protective agent to the silver ion-supramolecular assembly agent coordination polymer solution of step S2, wherein the mass ratio of the supramolecular assembly agent, the silver salt, the halide salt, and the polymer protective agent in the solution is (0.1-150): (0.1-100): (0.01-10): (1-600); then stirring, reacting at a temperature of -20-80°C in the dark for 0.1-10h, Step S3, after the reaction is completed, centrifugation and washing are performed to obtain the reaction product, and the reaction product is redispersed and vacuum dried to obtain silver nanowires.

2. The method for preparing silver nanowires mediated by metal organic coordination polymer according to claim 1, characterized in that: The polymer protective agent is one or a mixture of two or more of gelatin, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, triethylhexyl phosphoric acid, sodium lauryl sulfate, methyl amyl alcohol, polyacrylamide, guar gum and polyethylene glycol ester of fatty acids, polyethylene imine, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; The halide salt reaction rate controller is one of sodium chloride, sodium bromide, potassium chloride, potassium bromide, cupric chloride, cupric bromide, ferric chloride, ferrous chloride, ferrous bromide, ferrous bromide, cobalt chloride, cobalt bromide, zinc chloride, zinc bromide, zinc chloride, and zinc bromide, or a mixture of two or more thereof; 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 perbromide, silver periodate, silver bicarbonate, silver sulfide, silver gluconate and silver cyanate; The solvent of 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 polymer 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 polymer according to claim 1, characterized in that: In step S2, the reaction temperature is 25-65°C and the reaction time is 2-5h.

5. The method for preparing silver nanowires mediated by metal organic coordination polymer according to claim 1, characterized in that: In step S3, the centrifugal speed is 1000-7000 r / min, the number of centrifugal washings is 1-4 times, and the vacuum drying temperature is 50-80°C.

6. The method for preparing silver nanowires mediated by metal organic coordination polymer according to claim 5, characterized in that: In step S3, the vacuum drying temperature is 30-80° C., and the vacuum drying time is 1-20 h. After vacuum drying, the silver nanowire powder is crushed by air flow to obtain the silver nanowire powder.

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

8. The method for preparing silver nanowires mediated by a metal organic coordination polymer according to any one of claims 1 to 7, characterized in that: In the solution after adding the polymer protective agent in step S2, the mass ratio of the supramolecular assembly agent, the silver salt, the halide salt and the polymer protective agent is (24-30):10:(0.01-2):(80-120).

9. The method for preparing silver nanowires mediated by metal organic coordination polymer according to claim 8, characterized in that: The mass concentration of the soluble silver salt solution is 0.1-1000 mg / ml.

10. The method for preparing silver nanowires mediated by metal organic coordination polymer according to claim 8, characterized in that: The supramolecular assembling agent is at least one of cinnamic acid, tannin, p-hydroxybenzoic acid and caffeic acid.

Images