A method for preparing silver nanowires with ultra-high yield

Abstract

A method for preparing silver nanowires with ultra-high yield belongs to the technical field of one-dimensional nanomaterial preparation. The present invention first dissolves a chloride metal salt and polyvinyl pyrrolidone in a polyol to obtain a uniform transparent solution; then a polyol solution of silver nitrate is added dropwise thereto, a polyol solution containing a reducing agent is added after reflux reaction, the mixture is stirred and naturally cooled to room temperature, and the reaction product is centrifuged, washed and dried to obtain silver nanowires. The method for preparing silver nanowires provided by the present invention is an improvement on the polyol reduction method of silver nanowires, and the one-pot two-step reduction technology is used to greatly improve the reaction yield, and the yield can reach up to 95%. The preparation method not only has the advantages of simple operation, low cost and high repeatability, but also does not require inert gas protection, has a high yield, is suitable for large-scale production and use, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of one-dimensional nano material preparation, and specifically relates to a method for preparing ultra-high-yield silver nanowires. Background Art

[0002] Metallic one-dimensional nanostructured materials have excellent directional electron transport capabilities and have important applications in field effect transistor devices, electronic printing, catalysis, energy conversion and storage. Among them, silver nanowires have received more extensive attention due to their high conductivity and excellent environmental stability. The radial dimensions of the silver nanowires reported so far generally do not exceed 200nm, and the aspect ratio is generally greater than 10. In addition to excellent conductivity, silver nanowires also have good light transmittance and bending resistance. Therefore, silver nanowires are considered to be the most likely material to replace indium tin oxide (ITO) to manufacture transparent conductive films, and have important application prospects in touch screens and anti-bending LED displays. In addition, silver nanowires are also widely used in the preparation of conductive electrodes such as solar cells and screen printing. In addition, they also play an important role in biosensors, optical fibers, surface enhanced Raman spectroscopy and other fields.

[0003] At present, there are two main methods for preparing silver nanowires: template method and chemical synthesis method. The most typical chemical method is the polyol method, which is simple to operate and is the main process for the current industrial production of nano silver wires. The polyol method is mainly achieved by reducing metal salts with polyols. The method mainly includes silver source, solvent, reducing agent, coating agent and control agent. The main mechanism is that ethylene glycol decomposes into acetaldehyde with reducing ability at high temperature, reducing silver ions to zero-valent silver atoms, relying on the selective coating of PVP on the (100) crystal face of the silver seed, and the reduced silver element continuously deposits on the (111) crystal face of the silver seed, so that it grows into a silver nanowire with a one-dimensional nanostructure. Chloride ions are another important factor in the preparation of silver nanowires, which can coordinate with the silver core to stabilize them to prevent aggregation.

[0004] In the past period of time, various improved methods of polyol reduction have been developed at home and abroad to prepare silver nanowires, which can adjust the size, morphology and structure of silver nanowires. However, the current polyol method for preparing silver nanowires generally has the problem of low yield (usually around 50%). Therefore, achieving controllable preparation of ultra-high yield silver nanowires is still an important challenge. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing silver nanowires with ultra-high yield, aiming to solve the problem of low yield of current silver nanowires. The present invention adopts a one-pot two-step reduction method to prepare silver nanowires with a yield of up to 95%.

[0006] The method for preparing ultra-high-yield silver nanowires of the present invention comprises the following steps:

[0007] (1) Dissolve 15-35 mg of chloride metal salt and 2-10 g of polyvinyl pyrrolidone in 200 mL of polyol and completely dissolve at 80-100° C. to obtain a uniform transparent solution;

[0008] (2) adding 50-200 mL of a polyol solution containing 10-50 g / L silver nitrate dropwise to the transparent solution of step (1), stirring evenly, heating to 160-200° C., and refluxing for 0.5-2 hours;

[0009] (3) The reaction solution obtained in step (2) is cooled to 60-120° C., 8-60 mL of a polyol solution containing 2-15 mL of a reducing agent is added, the mixture is stirred and naturally cooled to room temperature, the reaction product is centrifuged and washed multiple times with deionized water and anhydrous ethanol, and then dried at 40-60° C. to obtain the silver nanowires of the present invention.

[0010] In the above method, the chloride metal salt includes but is not limited to sodium chloride, potassium chloride or a mixture thereof.

[0011] In the above method, the molecular weight of polyvinyl pyrrolidone is 300,000 to 2,000,000.

[0012] In the above method, the polyols used in step (1), step (2) and step (3) are the same, and the polyols include but are not limited to polyol solvents such as ethylene glycol, propylene glycol or glycerol.

[0013] In the above method, the reducing agent includes but is not limited to hydrazine hydrate or formaldehyde.

[0014] In the above method, the molar ratio of silver nitrate to reducing agent is 1:4-30.

[0015] In the above method, the diameter of the prepared silver nanowires is 40 to 110 nm, and the yield is 85 to 95%.

[0016] The advantages of the present invention are as follows: the preparation method of silver nanowires provided by the present invention is an improvement on the polyol reduction method of silver nanowires, and the one-pot two-step reduction technology is used to greatly improve the reaction yield, and the yield can reach up to 95%. The preparation method not only has the advantages of simple operation, low cost and high repeatability, but also does not require inert gas protection, has high yield, is suitable for large-scale production and use, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 : Scanning electron microscope photo of the silver nanowires prepared in Example 1;

[0018] Figure 2 : X-ray diffraction spectrum of the silver nanowires prepared in Example 1.

[0019] like Figure 1 As shown in the scanning electron microscope photograph of the silver nanowires prepared in Example 1, it can be seen that the material as a whole is in fiber morphology, the fiber diameter is about 40 to 110 nm, the fiber surface is smooth, and very few have protruding particles.

[0020] like Figure 2 As shown in the X-ray diffraction spectrum of the silver nanowires prepared in Example 1, it can be seen that the silver nanowires prepared in the present invention have characteristic peaks of silver (111), (200), (220), (311), and (222) planes at 38.7°, 44.9°, 65.0°, 77.9°, and 82.0°, respectively, proving that the present invention successfully prepared the silver nanowire material. DETAILED DESCRIPTION

[0021] Embodiment 1:

[0022] 2.4 g of silver nitrate was dissolved in 100 mL of ethylene glycol to prepare solution a; 26 mg of sodium chloride and 6 g of polyvinyl pyrrolidone (molecular weight 1300000) were dissolved in 200 mL of ethylene glycol and completely dissolved at 90° C. to prepare solution b; solution a was added dropwise to solution b, and the mixture was stirred continuously. After mixing evenly, the mixture was heated to 170° C., refluxed for 1 hour, and then cooled to 80° C., 24 mL of ethylene glycol solution containing 6 mL of hydrazine hydrate was added, stirred and naturally cooled to room temperature, and the reaction product was centrifugally washed with deionized water and anhydrous ethanol for multiple times, and then dried at 50° C. to obtain the silver nanowires of the present invention, with a yield of 95%.

[0023] Embodiment 2:

[0024] The same as Example 1, except that in the preparation of silver nanowires, the amount of silver nitrate was halved, the amounts of other reactants and the reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, with a yield of 95%.

[0025] Embodiment 3:

[0026] The same as Example 1, except that in the preparation of silver nanowires, the amount of silver nitrate was doubled, the amounts of other reactants and the reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, with a yield of 92%.

[0027] Embodiment 4:

[0028] The same as Example 1, except that in the preparation of silver nanowires, the amount of sodium chloride was halved, the amounts of other reactants and the reaction conditions remained unchanged, the proportion of silver nanowires in the product was reduced, and the yield was 87%.

[0029] Embodiment 5:

[0030] The same as Example 1, except that in the preparation of silver nanowires, the amount of sodium chloride was doubled, the amounts of other reactants and the reaction conditions remained unchanged, the proportion of silver nanowires in the product was reduced, and the yield was 88%.

[0031] Embodiment 6:

[0032] The same as Example 1, except that in the preparation of silver nanowires, the amount of hydrazine hydrate was halved, the amounts of other reactants and the reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, with a yield of 91%.

[0033] Embodiment 7:

[0034] The same as Example 1, except that in the preparation of silver nanowires, the amount of hydrazine hydrate was doubled, the amounts of other reactants and the reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, with a yield of 95%.

[0035] Embodiment 8:

[0036] The same as Example 1, except that in the preparation of silver nanowires, the amounts of silver nitrate, ethylene glycol, sodium chloride, polyvinyl pyrrolidone and hydrazine hydrate were halved, and other reaction conditions remained unchanged. The product was the same silver nanowires as in Example 1, with a yield of 90%.

[0037] Embodiment 9:

[0038] The same as Example 1, except that in the preparation of silver nanowires, the amounts of silver nitrate, ethylene glycol, sodium chloride, polyvinyl pyrrolidone and hydrazine hydrate were doubled, and other reaction conditions remained unchanged. The product was the same silver nanowires as in Example 1, with a yield of 93%.

[0039] Embodiment 10:

[0040] The same as Example 1, except that in the preparation of silver nanowires, hydrazine hydrate was replaced with formaldehyde, the amounts of other reactants and reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, with a yield of 85%.

[0041] Comparative Example 1:

[0042] The same as Example 1, except that hydrazine hydrate was not added in the preparation of silver nanowires, the amounts of other reactants and the reaction conditions remained unchanged, and the product was the same silver nanowires as in Example 1, but the yield was only 45%.

Claims

1. A method for preparing ultra-high yield silver nanowires with a yield of 85-95%, the steps of which are as follows: (1) Dissolve 15-35 mg of chloride metal salt and 2-10 g of polyvinyl pyrrolidone in 200 mL of polyol and completely dissolve at 80-100°C to obtain a uniform transparent solution; (2) adding 50-200 mL of a polyol solution of 10-50 g / L silver nitrate dropwise to the transparent solution of step (1), stirring evenly, heating to 160-200° C., and reflux for 0.5-2 hours; (3) The reaction solution obtained in step (2) is cooled to 60-120° C., 8-60 mL of a polyol solution containing 2-15 mL of a reducing agent is added, the mixture is stirred and naturally cooled to room temperature, the reaction product is centrifuged and washed multiple times with deionized water and anhydrous ethanol, and then dried at 40-60° C. to obtain the ultra-high yield silver nanowires; the reducing agent is hydrazine hydrate or formaldehyde, and the diameter of the prepared silver nanowires is 40-110 nm; The polyol used in step (1), step (2) and step (3) is the same.

2. The method for preparing ultra-high yield silver nanowires with a yield of 85-95% as claimed in claim 1, characterized in that: The chloride metal salt is sodium chloride, potassium chloride or a mixture thereof.

3. The method for preparing ultra-high yield silver nanowires with a yield of 85-95% as claimed in claim 1, characterized in that: The molecular weight of polyvinyl pyrrolidone is 300,000~2,000,000.

4. The method for preparing ultra-high yield silver nanowires with a yield of 85-95% as claimed in claim 1, characterized in that: The polyol is ethylene glycol, propylene glycol or glycerol.

5. The method for preparing ultra-high yield silver nanowires with a yield of 85-95% as claimed in claim 1, characterized in that: The molar ratio of silver nitrate to reducing agent is 1:4~30.

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