Method for synthesizing superfine silver nanowire step by step

Abstract

The preparation technology specifically comprises the following steps: (1) weighing polyvinylpyrrolidone, sodium bromide and sodium chloride, adding the polyvinylpyrrolidone, the sodium bromide and the sodium chloride into ethylene glycol, and stirring until the polyvinylpyrrolidone, the sodium bromide and the sodium chloride are completely dissolved to obtain a solution A; (2) weighing silver nitrate, adding the silver nitrate into ethylene glycol, stirring, and carrying out ultrasonic treatment until the silver nitrate is completely dissolved to obtain a solution B; (3) continuously heating the solution A, dropwise adding the solution B into the solution A, and adding an ethylene glycol solution of sodium bromide for the second time after dropwise adding is completed; (4) cooling the reaction liquid in the step (3), then placing the reaction liquid in the oil bath again, and continuously stirring until the reaction is finished; and (5) acetone and ethyl alcohol are sequentially added into the reaction liquid, a product is precipitated, separated and cleaned, and the superfine nanometer silver wire with the diameter being 10-35 nm and the length-diameter ratio reaching 1200 or above is obtained. The invention aims to solve the problems that the traditional one-pot method for synthesizing silver nanowires has many impurities; and the diameter and the length-diameter ratio are difficult to control. The method for adding the control agent in multiple steps is creatively adopted, and the technological process has the advantages of being easy to control, high in yield, simple in equipment and the like.

Description

Technical Field

[0001] The invention belongs to the field of nano material preparation process modification, and specifically relates to a step-by-step synthesis ultrafine nano silver wire preparation modification method. Background Art

[0002] With the transformation and upgrading of the consumer electronics industry, sensing and display technologies are developing rapidly. This has led to the growth of various optoelectronic devices, including touch panels, liquid crystal displays, transparent organic light-emitting diodes (OLEDs), thin-film solar cells and conductive glass industries. These products based on transparent conductive film materials need to be flexible, soft and even stretchable. Therefore, there is an urgent need for a flexible conductive film to replace the traditional expensive, rigid and brittle indium tin oxide (ITO) film.

[0003] One-dimensional metal nanowires have a wide range of applications in optics, energy saving, biological applications, electromagnetic shielding and sensors due to their unique properties. Among them, silver nanowires have been widely studied for the manufacture of conductive films. In order to cope with different application scenarios, conductive films need to have high transmittance, low haze, low square resistance and other characteristics. Especially for advanced applications, the requirements for conductive film materials are more stringent. For example, a ponytail touch screen requires low haze and low resistance under extremely high transparency conditions.

[0004] The silver nanowires required to make transparent conductive films have a narrow distribution of line widths, and in order to produce a smoother surface, a smaller film haze is required. Theoretical predictions and experiments have shown that silver nanowires with low diameters and high aspect ratios are beneficial to improving the performance of transparent conductive films. Therefore, it is extremely important to use silver nanowires with low diameters and high aspect ratios to prepare transparent conductive films.

[0005] In the past few decades, many researchers have been studying the synthesis of silver nanowires and developed several synthesis methods. So far, polyol synthesis is considered to be the most likely method for preparing qualified silver nanowires. However, the traditional one-pot one-step polyol synthesis of silver nanowires is difficult to control experimental variables and silver wire size. The preparation process of ultrafine high-purity silver nanowires is not yet mature. Summary of the invention

[0006] To solve the above problems, the present invention analyzes the intermediate products in the synthesis process of nano silver wires and creatively proposes a method for synthesizing nano silver wires in a multi-step process. The first step is to mix the precursor solution for seeding, and form high-purity twin crystal seeds in the precursor solution by adjusting the proportion and amount of the control agent; the second step is to adjust the seed and silver wire size by adding bromide salt in steps before and after seeding; the third step is to quickly cool the precursor mother solution; and the fourth step is to carry out the subsequent growth of nano silver wires.

[0007] The present invention provides a method for preparing nano silver wires, comprising the following steps: (1) Using an electronic balance, weigh polyvinyl pyrrolidone, sodium bromide, and sodium chloride, add them to a three-necked flask containing ethylene glycol, and stir throughout the process until the added solutes are completely dissolved to obtain solution A; (2) Weigh silver nitrate and add it to a beaker containing ethylene glycol, stir and sonicate until it is completely dissolved to obtain solution B; (3) Continue to heat solution A to a fixed temperature and maintain it for a fixed time for preheating, and then add it dropwise. During the dropwise addition process, add solution B to solution A, and then add the control agent after the dropwise addition is completed. Continue to stir until the reaction has occurred for a period of time; (4) Cooling the reaction solution of step (3), then placing the three-necked flask containing the cooled reaction solution back into the oil bath, and continuing to stir until the reaction is complete; (5) adding acetone to the reaction solution and continuing stirring to precipitate; (6) adding ethanol to separate and wash the precipitate to obtain nano silver wires.

[0008] Furthermore, the molecular weight of the polyvinyl pyrrolidone is 1300000, and the amount of polyvinyl pyrrolidone used is 50-100 parts by weight, sodium bromide is 1-2 parts, sodium chloride is 2-5 parts, and ethylene glycol is 30000-60000 parts.

[0009] Furthermore, in step (1), the heating temperature is 150-200° C. and the stirring speed is 60-600 rpm.

[0010] Furthermore, in step (2), the amounts of silver nitrate and ethylene glycol used are 200-300 parts by weight and 800-1000 parts by weight, respectively.

[0011] Furthermore, the control agent added in step (3) is sodium bromide, and the amount used is 0.1-10 parts by weight.

[0012] Furthermore, the heating temperature of step (3) is 150-200° C., the stirring speed is 60-300 rpm, and the stirring time is 10-150 minutes.

[0013] Furthermore, in step (3), the feed rate of the peristaltic pump is 0.3-0.6 ml / min and the reaction time is 0.5-60 minutes.

[0014] Furthermore, the cooling temperature of step (4) is 20-60°C, the heating temperature is 100-150°C, and the stirring speed is 60-300rpm.

[0015] The method for preparing a nano silver wire of the present invention has the following beneficial effects: the prepared nano silver wire has the characteristics of ultra-fineness, ultra-high aspect ratio and low impurities. In the method for preparing a nano silver wire of the present invention, chloride salt and bromide salt are used as synergistic control agents, and a double ion-assisted method is used to synthesize silver nano wires with an average diameter of 18-35nm, without adding any external pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 TEM image of the silver nanowire of Example 1;

[0017] Figure 2 TEM image of the silver nanowire of Example 2;

[0018] Figure 3 This is the TEM image of the silver nanowire of Example 3; DETAILED DESCRIPTION

[0019] In order to specify the rights more specifically and clearly, the present invention is further described below through specific examples. Each specific example is only used to illustrate the implementation method and related parameters of the present invention, and is not used to limit the present invention.

[0020] Embodiment 1: (1) 3.6 g of polyvinyl pyrrolidone, 0.055 g of sodium chloride and 0.054 g of sodium bromide were weighed and added to 100 ml of ethylene glycol, and stirred at 200 rpm until they were completely dissolved to obtain solution A; (2) Weigh 0.6 g of silver nitrate and add it to 20 mL of ethylene glycol. Stir until completely dissolved to obtain solution B. (3) Continue heating solution A to 170°C for 60 minutes, and then drip solution B at a rate of 0.5 ml / min. After the dripping is complete, add 0.018 g of sodium bromide. Continue stirring and react for 5 minutes; (4) rapidly cooling the reaction solution of step (3) to 50° C., then placing it back in a 140° C. oil bath and continuing to stir until the reaction is complete; (5) Add three volumes of acetone to the reaction solution and continue stirring to precipitate; add three volumes of ethanol to separate and wash the precipitate to obtain a nanosilver wire with a length of 30-40 μm and a diameter of 18 nm. Figure 1 shown.

[0021] Embodiment 2: (1) 3.3 g of polyvinyl pyrrolidone, 0.06 g of sodium chloride and 0.045 g of sodium bromide were weighed and added to 100 ml of ethylene glycol, and stirred at 200 rpm throughout the process until they were completely dissolved to obtain solution A; (2) Weigh 0.6 g of silver nitrate and add it to 20 mL of ethylene glycol. Stir until completely dissolved to obtain solution B. (3) Continue heating solution A to 170°C for 60 minutes, and then drip solution B at a rate of 0.5 ml / min. After the dripping is complete, add 0.02 g of sodium bromide. Continue stirring and react for 5 minutes; (4) rapidly cooling the reaction solution of step (3) to 50° C., then placing it back in a 120° C. oil bath and continuing to stir until the reaction is complete; (5) Add three volumes of acetone to the reaction solution and continue stirring to precipitate; add three volumes of ethanol to separate and wash the precipitate to obtain nanosilver wires with a length of 30-40 μm and a diameter of 22 nm. Figure 2 shown.

[0022] Embodiment 3: (1) Weigh 2.8 g of polyvinyl pyrrolidone, 0.06 g of sodium chloride and 0.035 g of sodium bromide by weight, add them to 100 ml of ethylene glycol, and stir at 200 rpm until they are completely dissolved to obtain solution A; (2) Weigh 0.6 g of silver nitrate and add it to 20 mL of ethylene glycol. Stir until completely dissolved to obtain solution B. (3) Continue heating solution A to 160°C for 60 minutes, and then drip solution B at a rate of 0.5 ml / min. After the dripping is complete, add 0.15 g of sodium bromide. Continue stirring and react for 5 minutes; (4) rapidly cooling the reaction solution of step (3) to 50° C., then placing it back in a 120° C. oil bath and continuing to stir until the reaction is complete; (5) Add three volumes of acetone to the reaction solution and continue stirring to precipitate; add three volumes of ethanol to separate and wash the precipitate to obtain a nanosilver wire with a length of 30-40 μm and a diameter of 35 nm. Figure 3 shown.

[0023] Characterization analysis by TEM, such as Figure 1-3 As shown, the diameter of the nano silver wire is 18-35nm. The above embodiments are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or supplements to the described specific embodiments or adopt similar methods without departing from the concept of the invention or exceeding the scope defined by the claims, which shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing silver nanowires, characterized in that: The steps include: (1) Weigh polyvinyl pyrrolidone, sodium bromide, and sodium chloride, add them to ethylene glycol, and stir throughout the process until they are completely dissolved to obtain solution A; (2) Weigh silver nitrate and add it to ethylene glycol, stirring until it is completely dissolved to obtain solution B; (3) Continue to heat solution A to a fixed temperature and maintain it for a fixed time for preheating, and then add it dropwise. During the dropwise addition process, add solution B to solution A, and then add the control agent after the dropwise addition is completed. Continue to stir until the reaction has occurred for a period of time; (4) cooling the reaction solution of step (3), then placing it back in the oil bath and continuing to stir until the reaction is complete; (5) Cool the reaction solution to room temperature. Add acetone to the reaction solution and continue stirring to precipitate. (6) adding ethanol to separate and wash the precipitate to obtain nano silver wires.

2. The method for preparing nano silver wires according to claim 1, characterized in that: In step (1), 50-100 parts of polyvinyl pyrrolidone, 1-2 parts of sodium bromide and 2-5 parts of sodium chloride are weighed and added to 30,000-60,000 parts of ethylene glycol, and stirred at a speed of 60-800 rpm throughout the process.

3. The method for preparing nano silver wire according to claim 1, characterized in that: In step (2), 200-300 parts of silver nitrate are weighed and added to 800-1000 parts of ethylene glycol. In step (3), the heating temperature in the preheating stage is 160-200°C and the stirring speed is 200-800 rpm; the heating temperature in the dropwise addition stage is 150-200°C and the stirring speed is 60-500 rpm.

4. The method for preparing nano silver wire according to claim 1, characterized in that: In step (3), the heating temperature is 150-200° C., the added control agent is sodium bromide, 0.1-10 parts by weight, and the reaction time is 0.5-10 minutes.

5. The method for preparing nano silver wire according to claim 1, characterized in that: The cooling temperature in step (4) is 20-60°C, the subsequent growth temperature is 120-180°C, and the reaction time is 30-180 minutes.

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