Superfine silver nanowire and preparation method thereof

Abstract

The preparation method comprises the following steps that polyvinylpyrrolidone is stirred and dissolved in a reducing agent under the heating condition, a solution A is obtained, a nucleating agent is dissolved in the reducing agent, a B-type solution is obtained, silver salt is dissolved in the reducing agent under the dark condition, and a solution C is obtained; heating and stirring the polyol dual-reducing agent solution in a reaction container, and adding the solution A and the solution B into the reaction container to obtain a reaction solution D; dropwise adding the solution C into the reaction solution D while heating and stirring, and carrying out quenching reaction on the reaction container after the reaction is finished. The diameter of the obtained superfine silver nanowire ranges from 11 nm to 25 nm, and the length-diameter ratio ranges from 2000 to 2500. According to the preparation method, the parameter conditions of the preparation process are controllable, the cost is remarkably reduced, the efficiency is improved, the operation is simple, and the silver nanowires with uniform morphology, high yield and high purity can be massively produced.

Description

Technical Field

[0001] The present invention relates to nanowires and a preparation method thereof, in particular to an ultrafine silver nanowire and a preparation method thereof. Background Art

[0002] Silver nanowires (AgNWs) exhibit the best performance among all solution-coated alternatives to ITO, including carbon nanotubes, graphene, and metal nanowires, due to their excellent conductivity, enhanced flexibility, and facile, low-cost solution-based thin-film fabrication technology. This holds great promise for applications in foldable electronic devices, large-area touchscreens, thin-film solar cells, and wearable displays. To achieve innovative functionalities, AgNWs with small diameters and high aspect ratios are often required.

[0003] Numerous chemical techniques have been developed for the synthesis of Ag NWs, including template-directed synthesis, electrochemical techniques, photoreduction based on UV irradiation, hydrothermal and solvothermal methods, and polyol synthesis. The polyol method remains one of the most promising due to its simplicity and high yield. Of course, there are other improved polyol methods, such as high pressure, high temperature, and nitrogen protection. However, to date, few reports have achieved fine nanowires with relatively few by-products. In addition, the necessary large-scale production of Ag NWs is difficult in most existing methods. Therefore, there is an urgent need for a low-cost method to mass-produce high-purity Ag NWs with uniform morphology and high yield. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing ultrafine silver nanowires with high preparation efficiency and simple operation. Another purpose of the present invention is to provide ultrafine silver nanowires with high purity.

[0005] Technical solution: The method for preparing ultrafine silver nanowires according to the present invention comprises the following steps:

[0006] Step 1: dissolving polyvinyl pyrrolidone in a reducing agent under heating and stirring to prepare solution A; directly dissolving a nucleating agent in the reducing agent to prepare solution B; and simultaneously dissolving a silver salt in the reducing agent under light-shielding conditions to obtain solution C;

[0007] Step 2: Heat and stir the polyol dual reducing agent solution in a reaction vessel, add solution A and type B solution into the reaction vessel to obtain reaction solution D;

[0008] Step 3: adding solution C dropwise to reaction solution D while heating and stirring; after the reaction is completed, quenching the reaction vessel to obtain ultrafine silver nanowires.

[0009] Furthermore, in step 1, the heating conditions are: heating temperature 165-175° C., heating time 8h-12h.

[0010] Furthermore, in step 1, the concentration of solution A is 110-130 g / L.

[0011] Furthermore, in step 1, the nucleating agent includes sodium chloride, sodium bromide, and ferric nitrate, the reducing agent is ethylene glycol, and the type B solution includes sodium chloride solution, sodium bromide solution, and ferric nitrate solution in a volume ratio of 115-125:55-65:30-90, the concentrations of sodium chloride and sodium bromide are both 0.2-0.5 mol / L, and the concentration of ferric nitrate solution is 0.3×10 -3 ~0.9×10 -3 mol / L.

[0012] Furthermore, in step 1, the silver salt is silver nitrate, and the concentration of solution C is 0.1-0.2 mol / L.

[0013] Furthermore, in step 2, the polyol dual reducing agent solution is a mixture of ethylene glycol and polyethylene glycol PEG-400, with a volume ratio of 10-14:1-5.

[0014] Furthermore, in step 2, the volume ratio of the polyol dual reducing agent solution to solution A is 11-19:3-7.

[0015] Furthermore, in step 2 and step 3, the temperature of heating and stirring is 165-175° C., and the speed of heating and stirring is 380-420 rpm.

[0016] Furthermore, in step 3, the rate of adding solution C is 0.2-0.3 mL / min, and the adding time is 33-50 min.

[0017] The ultrafine silver nanowires of the present invention have a diameter of 11 to 25 nm, an aspect ratio of 2000 to 2500, and a purity of 95%.

[0018] Preparation principle: The system is controlled by the synergistic kinetics of dual reducing agents (ethylene glycol provides the reduction driving force, and polyethylene glycol delays the subsequent reduction process through steric hindrance) and Fe 3+ Through nucleation control (oxidative etching and suppression of side reactions), the diameter of Ag NWs was refined and the purity was improved. Microscopically, multi-stage reduction-oxidation cycles and surface coordination interactions jointly determined the morphology and purity of the product, resulting in the synthesis of high-quality Ag NWs containing minimally contaminated silver nanoparticles.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. The preparation process parameters are controllable, which significantly reduces costs, improves efficiency, is simple to operate, and can mass-produce Ag NWs with uniform morphology, high yield, and high purity;

[0021] 2. The introduction of polyethylene glycol into the improved polyol method combined with ferric nitrate as a third nucleating agent achieved the preparation of ultrathin silver nanowires with high aspect ratio;

[0022] 3. The strong reducing power of polyethylene glycol allows the silver precursor to be quickly reduced to small silver cores, which are then uniaxially grown into fine silver nanowires. There are very few by-products and almost no contamination from silver nanoparticles, which enables large-scale production of silver nanowires.

[0023] 4. Fe 3+ Multiple twin seeds can be oxidatively etched, resulting in a reduction in the number of seeds and promoting the lateral growth of seeds to form AgNWs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a transmission electron microscope image of the product obtained in Example 1 of the present invention;

[0025] Figure 2 is a scanning electron microscope image of the product obtained in Example 1 of the present invention;

[0026] Figure 3 is a scanning electron microscope image of the product obtained in Example 2 of the present invention;

[0027] Figure 4 is a scanning electron microscope image of the product obtained in Example 3 of the present invention;

[0028] Figure 5 is a scanning electron microscope image of the product obtained in Comparative Example 1 of the present invention;

[0029] Figure 6 is a scanning electron microscope image of the product obtained in Comparative Example 2 of the present invention;

[0030] Figure 7 is a scanning electron microscope image of the product obtained in Comparative Example 3 of the present invention;

[0031] Figure 8 It is the visible absorption spectrum of the product obtained in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0032] Example 1

[0033] A method for preparing ultrafine silver nanowires comprises the following steps:

[0034] (1) Polyvinyl pyrrolidone was dissolved in ethylene glycol by stirring at 170°C and 400 rpm in an oil bath for 10 h to prepare a 120 g / L PVP solution. Sodium chloride was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium chloride solution. Sodium bromide was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium bromide solution. Ferric nitrate was added to ethylene glycol and shaken to dissolve to prepare a 0.03 mol / L ferric nitrate solution. 100 μL of the ferric nitrate solution was added to ethylene glycol for dilution to obtain a 0.3×10 -3 0.147 mol / L silver nitrate solution was prepared by dissolving silver nitrate in ethylene glycol by shaking under light-proof conditions.

[0035] (2) Heat 1 ml of polyethylene glycol PEG-400 and 14 ml of ethylene glycol in a reaction vessel in an oil bath at 170°C and 400 rpm for 15 min. Add 5 ml of the PVP solution to the reaction vessel, followed by 120 μL of sodium chloride solution, 60 μL of sodium bromide solution, and 60 μL of the diluted ferric nitrate solution to the reaction vessel for full reaction.

[0036] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and 10 ml was injected into the reaction container at a rate of 0.2 ml / min. After the reaction was completed for 50 minutes, the reaction container was quenched to obtain ultrafine silver nanowires.

[0037] like Figures 1 and 2 As shown, after measurement, the diameter of the ultrafine silver nanowires obtained in this embodiment is 15-25 nm, and the aspect ratio is 2000-2200.

[0038] The flexible transparent conductive film made of ultrafine silver nanowires has a resistance of 27Ωsq at 550nm. -1 , with a transmittance of 88% and a haze of 3.08%. It also has performance advantages such as excellent flexibility and bending stability. Its slender nanostructure can form a low-density and uniform conductive network, reducing the surface contact resistance and the junction resistance between nanowires. At the same time, the high transmittance makes it suitable for optical devices; the flexibility supports flexible electronic applications such as folding screens and wearable devices. Compared with traditional indium tin oxide (ITO), silver nanowire films have better mechanical durability and controllable costs. They are mainly used in flexible touch screens, OLED displays, wearable sensors, transparent electrodes for solar cells, and electromagnetic shielding materials. It is an ideal conductive substrate for the next generation of flexible electronic devices.

[0039] Example 2

[0040] A method for preparing ultrafine silver nanowires comprises the following steps:

[0041] (1) Polyvinyl pyrrolidone was dissolved in ethylene glycol by stirring at 170°C and 400 rpm in an oil bath for 10 h to prepare a 120 g / L PVP solution. Sodium chloride was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium chloride solution. Sodium bromide was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium bromide solution. Ferric nitrate was added to ethylene glycol and shaken to dissolve to prepare a 0.03 mol / L ferric nitrate solution. 100 μL of the ferric nitrate solution was added to ethylene glycol for dilution to obtain a 0.3×10 -3 0.147 mol / L silver nitrate solution was prepared by dissolving silver nitrate in ethylene glycol by shaking under light-proof conditions.

[0042] (2) Heat 3 ml of polyethylene glycol PEG-400 and 12 ml of ethylene glycol in a reaction vessel in an oil bath at 170°C and 400 rpm for 15 min. Add 5 ml of the PVP solution to the reaction vessel, followed by 120 μL of sodium chloride solution, 60 μL of sodium bromide solution, and 60 μL of the diluted ferric nitrate solution to the reaction vessel for complete reaction.

[0043] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and 10 ml was injected into the reaction container at a rate of 0.2 ml / min. After the reaction was completed for 50 minutes, the reaction container was quenched to obtain ultrafine silver nanowires.

[0044] like Figure 3 As shown, after measurement, the diameter of the ultrafine silver nanowires obtained in this embodiment is 11-24 nm, and the aspect ratio is 2000-2200.

[0045] Example 3

[0046] A method for preparing ultrafine silver nanowires comprises the following steps:

[0047] (1) Polyvinyl pyrrolidone was dissolved in ethylene glycol by stirring at 170°C and 400 rpm in an oil bath for 10 h to prepare a 120 g / L PVP solution. Sodium chloride was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium chloride solution. Sodium bromide was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium bromide solution. Ferric nitrate was added to ethylene glycol and shaken to dissolve to prepare a 0.03 mol / L ferric nitrate solution. 100 μL of the ferric nitrate solution was added to ethylene glycol for dilution to obtain a 0.3×10 -3 0.147 mol / L silver nitrate solution was prepared by dissolving silver nitrate in ethylene glycol by shaking under light-proof conditions.

[0048] (2) Heat 5 ml of polyethylene glycol PEG-400 and 10 ml of ethylene glycol in a reaction vessel in an oil bath at 170°C and 400 rpm for 15 min. Add 5 ml of the PVP solution to the reaction vessel, followed by 120 μL of sodium chloride solution, 60 μL of sodium bromide solution, and 60 μL of the diluted ferric nitrate solution to the reaction vessel for full reaction.

[0049] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and 10 ml was injected into the reaction container at a rate of 0.2 ml / min. After the reaction was completed for 50 minutes, the reaction container was quenched to obtain ultrafine silver nanowires.

[0050] like Figure 4 As shown, after measurement, the diameter of the ultrafine silver nanowires obtained in this embodiment is 13-23 nm, and the aspect ratio is 2200-2500.

[0051] Example 4

[0052] A method for preparing ultrafine silver nanowires comprises the following steps:

[0053] (1) Dissolve polyvinyl pyrrolidone in ethylene glycol by stirring at 165°C and 400 rpm in an oil bath for 12 hours to prepare a 110 g / L PVP solution. Add sodium chloride to ethylene glycol and ultrasonically dissolve it to prepare a 0.2 mol / L sodium chloride solution. Add sodium bromide to ethylene glycol and ultrasonically dissolve it to prepare a 0.2 mol / L sodium bromide solution. Add ferric nitrate to ethylene glycol and shake it to dissolve it to prepare a 0.09 mol / L ferric nitrate solution. Take 100 μL of the ferric nitrate solution and add it to ethylene glycol for dilution to obtain a 0.9×10 -3 Prepare a 0.1 mol / L silver nitrate solution by dissolving silver nitrate in ethylene glycol under light-shielding conditions by shaking.

[0054] (2) Heat 2 ml of polyethylene glycol PEG-400 and 11 ml of ethylene glycol in a reaction vessel in an oil bath at 165°C and 380 rpm for 15 min. Add 3 ml of the PVP solution to the reaction vessel, followed by 115 μL of sodium chloride solution, 55 μL of sodium bromide solution, and 30 μL of the diluted ferric nitrate solution to the reaction vessel for complete reaction.

[0055] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and injected into the reaction container at a rate of 0.3 ml / min. After the reaction was completed for 33 minutes, the reaction container was quenched to obtain ultrafine silver nanowires.

[0056] The diameter of the ultrafine silver nanowires obtained in this embodiment is 12-19 nm, and the aspect ratio is 2100-2400.

[0057] Example 5

[0058] A method for preparing ultrafine silver nanowires comprises the following steps:

[0059] (1) Dissolve polyvinyl pyrrolidone in ethylene glycol by stirring at 175°C and 400 rpm in an oil bath for 8 hours to prepare a 130 g / L PVP solution. Add sodium chloride to ethylene glycol and ultrasonically dissolve it to prepare a 0.5 mol / L sodium chloride solution. Add sodium bromide to ethylene glycol and ultrasonically dissolve it to prepare a 0.5 mol / L sodium bromide solution. Add ferric nitrate to ethylene glycol and shake it to dissolve it to prepare a 0.05 mol / L ferric nitrate solution. Take 100 μL of the ferric nitrate solution and add it to ethylene glycol for dilution to obtain a 0.5×10 - 3 Prepare a 0.2 mol / L silver nitrate solution by dissolving silver nitrate in ethylene glycol under light-shielding conditions by shaking.

[0060] (2) Heat 4 ml of polyethylene glycol PEG-400 and 13 ml of ethylene glycol in a reaction vessel in an oil bath at 175°C and 420 rpm for 15 min. Add 7 ml of the PVP solution to the reaction vessel, followed by 125 μL of sodium chloride solution, 65 μL of sodium bromide solution, and 90 μL of the diluted ferric nitrate solution to the reaction vessel for complete reaction.

[0061] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and 10 ml was injected into the reaction container at a rate of 0.3 ml / min. After the reaction was completed for 40 minutes, the reaction container was quenched to obtain ultrafine silver nanowires.

[0062] The diameter of the ultrafine silver nanowires obtained in this embodiment is 16-25 nm, and the aspect ratio is 2100-2300.

[0063] Comparative Example 1

[0064] A method for preparing silver nanowires comprises the following steps:

[0065] (1) Polyvinyl pyrrolidone was dissolved in ethylene glycol by stirring at 170°C and 400 rpm in an oil bath for 10 h to prepare a 120 g / L PVP solution. Sodium chloride was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium chloride solution. Sodium bromide was added to ethylene glycol and ultrasonically dissolved to prepare a 0.3 mol / L sodium bromide solution. Ferric nitrate was added to ethylene glycol and shaken to dissolve to prepare a 0.03 mol / L ferric nitrate solution. 100 μL of the ferric nitrate solution was added to ethylene glycol for dilution to obtain a 0.3×10 -3 0.147 mol / L silver nitrate solution was prepared by dissolving silver nitrate in ethylene glycol by shaking under light-proof conditions.

[0066] (2) Heat 10 ml of polyethylene glycol PEG-400 and 5 ml of ethylene glycol in a reaction vessel in an oil bath at 170°C and 400 rpm for 15 min. Add 5 ml of the PVP solution to the reaction vessel, followed by 120 μL of sodium chloride solution, 60 μL of sodium bromide solution, and 60 μL of the diluted ferric nitrate solution to the reaction vessel for full reaction.

[0067] (3) While heating and stirring, 13 ml of silver nitrate solution was taken with a syringe and injected into the reaction container at a rate of 0.2 ml / min. After the reaction was completed for 50 minutes, the reaction container was quenched to obtain silver nanowires.

[0068] like Figure 5 The diameter of the ultrafine silver nanowires obtained in this comparative example was measured to be 13 to 30 nm, and the aspect ratio was 500 to 800. Compared with Example 3, this comparative example differed only in the volume of polyethylene glycol PEG-400 and ethylene glycol in step (2), resulting in a significantly reduced aspect ratio.

[0069] Comparative Example 2

[0070] The remaining steps of this comparative example are the same as those of Example 3, except that polyethylene glycol PEG-400 is not added, and only ethylene glycol is added. Figure 6 , after measurement, the diameter of the silver nanowires obtained in this comparative example is 20-35 nm, and the aspect ratio is 1400-2000. Compared with Example 3, the diameter is larger.

[0071] Comparative Example 3

[0072] The remaining steps of this comparative example are the same as those of Example 3, except that the ferric nitrate in step (1) is replaced by copper nitrate. Figure 7 The diameter of the silver nanowires obtained in this comparative example was measured to be 30 to 50 nm, and the aspect ratio was 700 to 900. Compared with Example 3, the diameter was significantly increased, and the aspect ratio was reduced.

[0073] Comparative Example 4

[0074] The remaining steps of this comparative example are the same as those of Example 3, except that the heating temperature is changed to 150°C. Figure 8 , the longitudinal surface plasmon resonance peak of the UV-visible absorption spectrum is at 435 nm, indicating large particles.

Claims

1. A method for preparing ultrafine silver nanowires, characterized in that: The following steps are involved: Step 1: dissolving polyvinyl pyrrolidone in a reducing agent under heating and stirring to prepare solution A; directly dissolving a nucleating agent in the reducing agent to prepare solution B; and simultaneously dissolving a silver salt in the reducing agent under light-shielding conditions to obtain solution C; Step 2: Heat and stir the polyol dual reducing agent solution in a reaction vessel, add solution A and type B solution into the reaction vessel to obtain reaction solution D; Step 3: adding solution C dropwise to reaction solution D while heating and stirring; after the reaction is completed, quenching the reaction vessel to obtain ultrafine silver nanowires.

2. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 1, the heating conditions are: heating temperature 165-175° C., heating time 8 h to 12 h.

3. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 1, the concentration of solution A is 110-130 g / L.

4. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 1, the nucleating agent includes sodium chloride, sodium bromide, and ferric nitrate, the reducing agent is ethylene glycol, and the type B solution includes sodium chloride solution, sodium bromide solution, and ferric nitrate solution in a volume ratio of 115-125:55-65:30-90. The concentrations of the sodium chloride and sodium bromide are both 0.2-0.5 mol / L, and the concentration of the ferric nitrate solution is 0.3×10 -3 ~0.9×10 -3 mol / L.

5. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 1, the silver salt is silver nitrate, and the concentration of the solution C is 0.1-0.2 mol / L.

6. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 2, the polyol dual reducing agent solution is a mixture of ethylene glycol and polyethylene glycol PEG-400, with a volume ratio of 10-14:1-5.

7. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 2, the volume ratio of the polyol dual reducing agent solution to solution A is 11-19:3-7.

8. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the steps 2 and 3, the temperature of heating and stirring is 165-175° C., and the speed of heating and stirring is 380-420 rpm.

9. The method for preparing ultrafine silver nanowires according to claim 1, wherein: In the step 3, the rate of adding solution C is 0.2-0.3 mL / min, and the adding time is 33-50 min.

10. The ultrafine silver nanowires obtained by the method for preparing ultrafine silver nanowires according to claim 1, characterized in that: The ultrafine silver nanowire has a diameter of 11-25 nm, an aspect ratio of 2000-2500, and a purity of 95%.

Images