High-length-diameter-ratio silver nanowire preparation method based on spatial effect adjustment

Abstract

The invention discloses a high length-diameter ratio silver nanowire preparation method based on spatial effect adjustment, which comprises the following steps: taking silver chloride as a silver source, compounding two different soft template agents based on the steric hindrance effect of a macromolecular chain to achieve the effects of modulating the steric hindrance of the macromolecular chain and enhancing the radial coating of the silver nanowire; therefore, the synthesis of the silver nanowire with high length-diameter ratio is assisted. The preparation method comprises the following specific steps: step 1, adding two different soft template agents into deionized water, and fully and uniformly stirring to obtain a solution A; step 2, adding glucose and sodium chloride into the solution A obtained in the step 1, and fully and uniformly stirring to obtain a solution B; 3, dissolving silver nitrate in deionized water to obtain a solution C; 4, dropwise adding the solution C into the solution B, and uniformly mixing under magnetic stirring to obtain a mixed solution; (5) transferring the mixed solution obtained in the step (4) into a reaction kettle for soft template-assisted hydrothermal reaction; and 6, the hydrothermal product obtained in the step 5 is centrifuged and washed, and the silver nanowire with the high length-diameter ratio is obtained. The average length of the prepared silver nanowire can reach 85 microns, the average diameter of the silver nanowire is 40 nm, and the length-diameter ratio of the silver nanowire exceeds 2000.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to a method for preparing silver nanowires with a high aspect ratio based on spatial effect regulation. Background Art

[0002] Flexible electronic products have the characteristics of softness, portability, and large-area application, which greatly expands the scope of use of electronic devices and is a hot spot for the development of the future electronic manufacturing industry. Driven by the industry trend, flexible transparent conductive films with flexibility, high light transmittance, and high conductivity have become strategic materials for the flexible optoelectronic industry.

[0003] Traditional transparent conductive materials such as indium tin oxide (ITO) are difficult to adapt to the demand for transparent electrodes in new flexible electronic devices due to their inherent brittleness, scarce raw materials, high cost and complex processes. It is urgent to develop new electrode materials that are cheap, have excellent mechanical properties and can be produced on a large scale. Compared with transparent conductive films such as ITO, metal grids, and carbon nanotubes, silver nanowire transparent conductive films have the advantages of good conductivity, good light transmittance, excellent bendability, good stability, no moiré, and easy access to raw materials. They are the most advantageous alternative materials to ITO transparent conductive films in the fields of flexible foldable and large-screen displays.

[0004] Flexible touch screens, flexible displays and other fields have placed extremely high demands on silver nanowire transparent conductive films. Only by using high aspect ratio (usually ≥1000) and high purity silver nanowires can a transparent conductive film with low square resistance, low haze and high transmittance be prepared. There are many methods for preparing silver nanowires, including template method, polyol method, hydrothermal method, etc. The template method is easy to control the morphology of the product, but the preparation process is complicated, and there are problems such as difficulty in removing the template and easy agglomeration of nanowires after removing the template; the polyol method is low in cost, high in efficiency and easy to operate, but the prepared nanowires have a small aspect ratio and low product purity. At present, the synthesis of high aspect ratio silver nanowires is still a bottleneck restricting the development of flexible transparent conductive films. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing silver nanowires with high aspect ratio based on spatial effect regulation. Environmentally friendly glucose is selected as a reducing agent, silver chloride is used as a silver source, a high molecular weight compound and a low molecular weight compound are compounded as a soft template, and a soft template-assisted hydrothermal method is used to synthesize silver nanowires with high aspect ratio.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for preparing silver nanowires with high aspect ratio based on spatial effect regulation, characterized in that it comprises the following steps:

[0008] Step 1: Add two different soft templates into deionized water and stir well to obtain solution A;

[0009] Step 2: Add glucose and sodium chloride to the solution A obtained in step 1, and stir well to obtain solution B;

[0010] Step 3: dissolving silver nitrate in deionized water to obtain solution C;

[0011] Step 4: Add solution C dropwise into solution B, and mix evenly under magnetic stirring to obtain a mixed solution;

[0012] Step 5: transferring the mixed solution obtained in step 4 to a reaction vessel for soft template-assisted hydrothermal reaction;

[0013] Step 6: Centrifuge and wash the hydrothermal product obtained in step 5 to obtain silver nanowires with a high aspect ratio.

[0014] In some embodiments, in step 1, among the soft template agents sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone K30, and polyvinyl pyrrolidone K90, a high molecular weight compound and a low molecular weight compound are selected for compounding, wherein the molar ratio of polyvinyl pyrrolidone K90 to polyvinyl pyrrolidone K30 is 1:(0.25-4), the molar ratio of polyvinyl pyrrolidone K90 (K30) to sodium dodecylbenzene sulfonate or hexadecyltrimethylammonium bromide is (5-15):1, and the molar ratio of the polymer is calculated according to the monomer.

[0015] In some embodiments, in step 2, the molar ratio of glucose to sodium chloride in solution B is (1-1.5):1.

[0016] In some embodiments, in step 3, the concentration of silver nitrate is 0.03 M.

[0017] In some embodiments, in step 4, the dropwise addition rate of solution C is 0.2 mL / s, the magnetic stirring rate is 600 rpm, and stirring is maintained for 5-10 min after the dropwise addition is completed.

[0018] In some embodiments, in step 4, the molar ratio of the soft template, glucose, sodium chloride, and silver nitrate in the mixed solution is (30-60): (2-3): 2:1.

[0019] In some embodiments, in step 5, the reaction temperature is 145-170° C., and the reaction time is 20-28 h.

[0020] In some embodiments, in step 6, the centrifugation is performed in descending order at 2000 rpm, 1500 rpm, and 1000 rpm, and the centrifugation time at each speed is 20 min, 15 min, and 10 min, respectively, and the dispersion solvent is water or ethanol.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses silver chloride as a silver source. The low solubility of silver chloride can not only make the initial silver ion concentration in the solution low, which is conducive to the formation of multiple twins; but also in the reaction process, the silver ions are slowly released, which is conducive to the anisotropic growth of silver nanowires, thereby promoting the formation of high aspect ratio silver nanowires. Silver nanowires are prepared by using a high molecular weight compound and a low molecular weight compound as a soft template. After the high molecular weight compound is dissolved, the steric hindrance effect in the solution forms a three-dimensional cavity; the low molecular weight compound enters the cavity to modulate its steric hindrance effect, thereby enhancing the radial coating effect on the silver nanowires and promoting the growth of high aspect ratio silver nanowires.

[0023] Specifically, the present invention uses silver chloride as a silver source, based on the spatial effect of a soft template, and utilizes a soft template-assisted hydrothermal method to grow silver nanowires with a high aspect ratio, which has the following effects:

[0024] (1) By adjusting the ratio of the soft template agent, the average length of the silver nanowires can reach 85 μm, the average diameter can reach 40 nm, and the aspect ratio can exceed 2000;

[0025] (2) This method does not use organic solvents to prepare silver nanowires, does not produce harmful substances, and is green, environmentally friendly, simple to operate, and low in cost;

[0026] (3) The use of low-speed descending centrifugation can effectively purify the prepared silver nanowires while reducing the difficulty of centrifugation operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the silver nanowire morphology provided in Example 1;

[0028] Figure 2 is the silver nanowire morphology provided in Example 1;

[0029] Figure 3 is the silver nanowire morphology provided in Example 2;

[0030] Figure 4 is the silver nanowire morphology provided in Example 2;

[0031] Figure 5 is the silver nanowire morphology provided in Example 3;

[0032] Figure 6 is the silver nanowire morphology provided in Example 3;

[0033] Figure 7 This is the morphology of the silver nanowires provided in Comparative Example 1;

[0034] Figure 8 This is the morphology of the silver nanowires provided in Comparative Example 1. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solution of the invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0036] Embodiment 1:

[0037] Weigh 0.50 g polyvinyl pyrrolidone K90 and 0.081 g hexadecyl trimethyl ammonium bromide and dissolve them in 15 mL deionized water to obtain solution A; weigh 0.0175 g sodium chloride and 0.06 g glucose and add them to solution A, dissolve and stir to obtain solution B; weigh 0.0255 g silver nitrate and dissolve it in 5 mL deionized water to obtain solution C. Add 5 mL of solution C dropwise to solution B at 0.2 mL / s and stir for 20 min to obtain a reaction solution. Transfer the reaction solution to the polytetrafluoroethylene liner of a stainless steel reactor, heat it to 160 °C and keep it for 24 h. After the reaction is completed, it is allowed to cool naturally to room temperature to obtain a stock solution containing silver nanowires. Deionized water is added to the stock solution and centrifuged at 2000 rpm for 20 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1500 rpm for 15 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1000 rpm for 10 min. The supernatant is extracted and dispersed in anhydrous ethanol to obtain a silver nanowire dispersion. Take a certain amount of the silver nanowire dispersion, dilute it with ethanol, and then drop it on the silicon wafer. After drying naturally, observe it under a scanning electron microscope. Figure 1 , Figure 2 The average length of the silver nanowires obtained was 75 μm, the average diameter was 70 nm, and the aspect ratio was over 1000.

[0038] Embodiment 2:

[0039] Weigh 0.50 g polyvinyl pyrrolidone K90 and 0.078 g sodium dodecylbenzene sulfonate and dissolve them in 15 mL deionized water to obtain solution A; weigh 0.0175 g sodium chloride and 0.06 g glucose and add them to solution A, dissolve and stir to obtain solution B; weigh 0.0255 g silver nitrate and dissolve it in 5 mL deionized water to obtain solution C. Add 5 mL of solution C to solution B at 0.2 mL / s and stir for 20 min to obtain a reaction solution. Transfer the reaction solution to the polytetrafluoroethylene liner of a stainless steel reactor, heat it to 160 °C and keep it for 24 h. After the reaction is completed, it is allowed to cool naturally to room temperature to obtain a stock solution containing silver nanowires. Deionized water is added to the stock solution and centrifuged at 2000 rpm for 20 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1500 rpm for 15 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1000 rpm for 10 min. The supernatant is extracted and dispersed in anhydrous ethanol to obtain a silver nanowire dispersion. Take a certain amount of the silver nanowire dispersion, dilute it with ethanol, and then drop it on the silicon wafer. After drying naturally, observe it under a scanning electron microscope. Figure 3 , Figure 4 The average length of the silver nanowires obtained was 65 μm, the average diameter was 60 nm, and the aspect ratio was over 1000.

[0040] Embodiment 3:

[0041] Weigh 0.75 g polyvinyl pyrrolidone K30 and 0.25 g polyvinyl pyrrolidone K90 and dissolve them in 15 mL deionized water to obtain solution A; weigh 0.0175 g sodium chloride and 0.06 g glucose and add them to solution A, dissolve and stir to obtain solution B; weigh 0.0255 g silver nitrate and dissolve it in 5 mL deionized water to obtain solution C. Add 5 mL of solution C dropwise to solution B at 0.2 mL / s and stir for 20 min to obtain a reaction solution. Transfer the reaction solution to the polytetrafluoroethylene liner of a stainless steel reactor, heat it to 160 °C and keep it for 24 h. After the reaction is completed, it is allowed to cool naturally to room temperature to obtain a stock solution containing silver nanowires. Deionized water is added to the stock solution and centrifuged at 2000 rpm for 20 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1500 rpm for 15 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1000 rpm for 10 min. The supernatant is extracted and dispersed in anhydrous ethanol to obtain a silver nanowire dispersion. Take a certain amount of the silver nanowire dispersion, dilute it with ethanol, and then drop it on the silicon wafer. After drying naturally, observe it under a scanning electron microscope. Figure 3 , Figure 4 The average length of the silver nanowires obtained was 85 μm (some exceeded 120 μm), the average diameter was 40 nm, and the aspect ratio was over 2000.

[0042] Comparative Example 1:

[0043] Weigh 0.50 g of polyvinyl pyrrolidone K90 and dissolve it in 15 mL of deionized water to form solution A; weigh 0.0175 g of sodium chloride and 0.06 g of glucose and add them to solution A, dissolve and stir to obtain solution B; weigh 0.0255 g of silver nitrate and dissolve it in 5 mL of deionized water to obtain solution C. Add 5 mL of solution C dropwise to solution B at 0.2 mL / s and stir for 20 min to obtain a reaction solution. Transfer the reaction solution to the polytetrafluoroethylene liner of a stainless steel reactor, heat it to 160 °C and keep it for 24 h. After the reaction is completed, the solution is cooled naturally to room temperature to obtain a stock solution containing silver nanowires. Deionized water is added to the stock solution and centrifuged at 2000 rpm for 20 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1500 rpm for 15 min. The supernatant is extracted and then dispersed with anhydrous ethanol and centrifuged at 1000 rpm for 10 min. The supernatant is extracted and dispersed in anhydrous ethanol to obtain a silver nanowire dispersion. A certain amount of the silver nanowire dispersion is taken, diluted with ethanol, and then dripped onto a silicon wafer. After drying naturally, it is observed by scanning electron microscopy. The average length of the silver nanowires obtained is 35 μm, the average diameter is 43 nm, and the aspect ratio is less than 1000.

[0044] The above-mentioned embodiments only express the specific implementation methods of the present application, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of protection of the present application. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, which all belong to the protection of the present application.

Claims

1. A method for preparing silver nanowires with high aspect ratio based on spatial effect regulation, characterized in that: The steps include: Step 1: Add two different soft templates into deionized water and stir well to obtain solution A; Step 2: Add glucose and sodium chloride to the solution A obtained in step 1, and stir well to obtain solution B; Step 3: dissolving silver nitrate in deionized water to obtain solution C; Step 4: Add solution C dropwise into solution B, and mix evenly under magnetic stirring to obtain a mixed solution; Step 5: transferring the mixed solution obtained in step 4 to a reaction vessel for soft template-assisted hydrothermal reaction; Step 6: Centrifuge and wash the hydrothermal product obtained in step 5 to obtain silver nanowires with a high aspect ratio.

2. The preparation method according to claim 1, characterized in that: In step 1, a high molecular weight compound and a low molecular weight compound are selected from the soft template agents sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl pyrrolidone K30, and polyvinyl pyrrolidone K90 for compounding, wherein the molar ratio of polyvinyl pyrrolidone K90 to polyvinyl pyrrolidone K30 is 1:(0.25-4), the molar ratio of polyvinyl pyrrolidone K90 or polyvinyl pyrrolidone K30 to sodium dodecylbenzene sulfonate or hexadecyltrimethylammonium bromide is (5-15):1, and the molar ratio of the polymer is calculated according to the monomer.

3. The preparation method according to claim 1, characterized in that: In step 2, the molar ratio of glucose to sodium chloride in the solution B is (1-1.5):

1.

4. The preparation method according to claim 1, characterized in that: In step 3, the concentration of silver nitrate is 0.03M.

5. The preparation method according to claim 1, characterized in that: In step 4, the dropwise addition rate of solution C is 0.2 mL / s, the magnetic stirring rate is 600 rpm, and stirring is maintained for 5-10 min after the dropwise addition is completed.

6. The preparation method according to claim 1, characterized in that: In step 4, the molar ratio of the soft template, glucose, sodium chloride and silver nitrate in the mixed solution is (30-60): (2-3): 2:

1.

7. The preparation method according to claim 1, characterized in that: In step 5, the reaction temperature is 145-170° C., and the reaction time is 20-28 h.

8. The preparation method according to claim 1, characterized in that: In step 6, the centrifugation is performed in descending order at 2000 rpm, 1500 rpm, and 1000 rpm, and the centrifugation time at each speed is 20 min, 15 min, and 10 min, respectively. The dispersion solvent is water or ethanol.

Images