Preparation method and application of sintering-free silver nanowire aerogel

Abstract

The invention discloses a preparation method and application of a sintering-free silver nanowire aerogel. The preparation method comprises the following steps: firstly, synthesizing a silver nanowire, and then carrying out in-situ connection curing on the silver nanowire through nano-silver obtained by freezing phase separation and low-temperature secondary reduction to obtain a three-dimensional network aerogel with a silver nanowire structure. According to the preparation method, the problem that high-temperature sintering is difficult in preparation of the nano-silver aerogel is solved, and the three-dimensional network aerogel with the silver nanowire structure can be obtained without high-temperature sintering. The silver nanowire aerogel disclosed by the invention has high porosity and low density, and is used for desalting seawater by a thermal distillation method.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically relating to a method for preparing sinter-free silver nanowire aerogel and its applications. Background Technology

[0002] Aerogel materials are hailed as one of the top ten materials that will change the world. Generally, aerogels refer to silica aerogels. They are prepared by first creating a silica hydrogel using organosilicon or inorganic silicon. This hydrogel is mainly composed of three-dimensionally interconnected nano-silica and water. The preparation process includes steps such as aging, solvent replacement, and surface hydrophobic modification. Subsequently, by removing water while retaining the network-like porous structure, silica aerogels, commonly known as aerogel materials, are obtained. With the advancement of research in the field of aerogels, different types of aerogels have emerged, including organic aerogels, carbon aerogels, ceramic aerogels, and metal aerogels. Metal aerogels have low density, high porosity, large specific surface area, high electrical conductivity, low thermal conductivity, sound insulation properties, and good electromagnetic wave absorption properties. Due to their excellent properties, metal aerogels show broad application prospects in many fields. For example, they can be used as catalyst supports; their high surface area and abundant pore structure enhance catalytic activity, making them play an important role in chemical synthesis and catalytic reactions. Metal aerogels also have broad application prospects in sensor technology. Their large surface area and tunable pore structure make them an ideal choice for high-sensitivity sensors, covering multiple fields such as gas sensing and biosensing. In the energy field, metal aerogels are used as electrode materials in supercapacitors and lithium-ion batteries, fully leveraging their excellent conductivity and high surface area.

[0003] Research on metal aerogels is still in its early stages. Because the constituent metal materials of aerogels are nanoscale, with very low melting points, easy oxidation, and high reactivity, their preparation presents many challenges. One of these challenges is the inability to prepare aerogels by removing organic templates, as the melting points of nanoscale metals are below 300°C, making it difficult to ablate and remove the organic templates.

[0004] Qiang et al. at Lawrence Laboratories in the United States first synthesized silver nanowires using a polyol method and then prepared silver nanowire aerogels via cryogenic casting and sintering (Ultralight conductive silver nanowires aerogels, Qiang et al. Nano Lett. 17, 7171-7176 (2017)). However, silver nanowires have a very low melting point, and the melting point decreases with finer nanowires, generally around 200℃. When preparing silver nanowires via sintering, due to the difference in diameter of the raw material, finer nanowires melt while coarser ones have not yet reached their melting point, making sintering difficult. As the authors of the aforementioned paper pointed out, their success in preparing silver nanowire aerogels was due to their ability to produce high-quality silver nanowires. This method has extremely stringent requirements for nanowires, making it difficult to use widely. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing sinter-free silver nanowire aerogels to solve the problems mentioned in the background art. The technical solution of this invention is as follows: Step 1: Silver nanowires were synthesized using silver nitrate, ethylene glycol, polyvinylpyrrolidone (PVP), and copper chloride via a polyol method. Step 2: The silver nanowires in ethylene glycol were concentrated by centrifugation, the supernatant was discarded, and the nanowires were soaked in anhydrous ethanol to remove the PVP coating on the surface of the silver nanowires. Step 3: The sample was further centrifuged, the supernatant and ethanol were discarded, and water was added to adjust the concentration to obtain an aqueous dispersion of silver nanowires. Step 4: Silver nitrate was added to the dispersion. Step 5: The sample was frozen and kept in a low-temperature solid state under a 5–100 W UV lamp for 2–12 hours to obtain a silver nanowire hydrogel. During this process, the contact points of the silver nanowires were welded by secondary silver nanoparticles. Step 6: The sample was dried at normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel was 12–123 mg / cm³. 3 With a porosity of 89.2%–99.7%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

[0006] The purpose of removing the alcohol coating on the surface of the silver nanowires in step 2 of this application is to create conditions for the subsequent in-situ bonding and solidification of silver particles at the contact points. The freezing method in step 5 aims to repel other components in the original aqueous solution, such as silver nanowires and silver nitrate, to the ice crystal boundaries through freezing. These non-aqueous components are squeezed by the ice crystal boundaries, creating conditions for subsequent photoreduction curing.

[0007] Beneficial effects: The method for preparing silver nanowire aerogel disclosed in this invention uses secondary nanosilver obtained by reduction to perform in-situ welding of silver nanowires at room temperature, overcoming the difficulty of sintering in the prior art; in addition, since the silver nanowire hydrogel has very good strength, the use of atmospheric pressure drying avoids the problem of high cost of supercritical drying. Attached Figure Description

[0008] Figure 1 The image shows a scanning electron microscope (SEM) image of the silver nanowire aerogel prepared in Example 1.

[0009] Figure 2 This is a scanning electron microscope image of the silver nanowire aerogel prepared in Example 4. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0011] Example 1: A method for preparing a sinter-free silver nanowire aerogel includes the following steps: Step 1: Add 3.2g of silver nitrate, 9g of polyvinylpyrrolidone, and 0.01g of copper chloride to 100ml of ethylene glycol and react in an oil bath at 180℃ for 3h to obtain a silver nanowire ethylene glycol dispersion; Step 2: Centrifuge and concentrate the silver nanowire ethylene glycol dispersion, discard the supernatant, and wash with alcohol three times for 30 minutes each time; Step 3: Centrifuge the sample, discard the supernatant and alcohol, and add 50ml of water to obtain a silver nanowire aqueous dispersion; Step 4: Add 1mg of silver nitrate to the dispersion; Step 5: Freeze-solidify the sample and keep it in a low-temperature solid state under a 5W UV lamp for 12 hours to obtain a silver nanowire hydrogel, during which the contact points of the silver nanowires are welded by secondary silver nanoparticles; Step 6: Dry the sample under normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel is 123mg / cm³. 3 With a porosity of 89.2%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

[0012] Example 2: A method for preparing a sinter-free silver nanowire aerogel includes the following steps: Step 1: Add 2.8g silver nitrate, 8.7g polyvinylpyrrolidone, and 0.01g copper chloride to 100ml ethylene glycol and react in an oil bath at 180℃ for 3h to obtain a silver nanowire ethylene glycol dispersion; Step 2: Centrifuge and concentrate the silver nanowire ethylene glycol dispersion, discard the supernatant, and wash with alcohol three times for 30 minutes each time; Step 3: Centrifuge the sample, discard the supernatant and alcohol, and add 50ml of water to obtain a silver nanowire aqueous dispersion; Step 4: Add 1mg silver nitrate to the dispersion; Step 5: Freeze-solidify the sample and keep it in a low-temperature solid state under a 20W UV lamp for 10 hours to obtain a silver nanowire hydrogel, during which the contact points of the silver nanowires are welded by secondary silver nanoparticles; Step 6: Dry the sample under normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel is 98mg / cm³. 3 With a porosity of 89.7%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

[0013] Example 3: A method for preparing a sinter-free silver nanowire aerogel includes the following steps: Step 1: Add 2.4g silver nitrate, 8.2g polyvinylpyrrolidone, and 0.01g copper chloride to 100ml ethylene glycol and react in an oil bath at 180℃ for 3h to obtain a silver nanowire ethylene glycol dispersion; Step 2: Centrifuge and concentrate the silver nanowire ethylene glycol dispersion, discard the supernatant, and wash with alcohol three times for 30 minutes each time; Step 3: Centrifuge the sample, discard the supernatant and alcohol, and add 50ml of water to obtain a silver nanowire aqueous dispersion; Step 4: Add 1mg silver nitrate to the dispersion; Step 5: Freeze-solidify the sample and keep it in a low-temperature solid state under a 50W UV lamp for 8 hours to obtain a silver nanowire hydrogel, during which the contact points of the silver nanowires are welded by secondary silver nanoparticles; Step 6: Dry the sample under normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel is 88mg / cm³. 3 With a porosity of 99.1%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

[0014] Example 4: A method for preparing a sinter-free silver nanowire aerogel includes the following steps: Step 1: Add 1.2g silver nitrate, 3.7g polyvinylpyrrolidone, and 0.01g copper chloride to 100ml ethylene glycol and react in an oil bath at 180℃ for 3h to obtain a silver nanowire ethylene glycol dispersion; Step 2: Centrifuge and concentrate the silver nanowire ethylene glycol dispersion, discard the supernatant, and wash with alcohol three times for 30 minutes each time; Step 3: Centrifuge the sample, discard the supernatant and alcohol, and add 50ml of water to obtain a silver nanowire aqueous dispersion; Step 4: Add 1mg silver nitrate to the dispersion; Step 5: Freeze-solidify the sample and maintain it in a low-temperature solid state under a 70W UV lamp for 5 hours to obtain a silver nanowire hydrogel, during which the contact points of the silver nanowires are welded by secondary silver nanoparticles; Step 6: Dry the sample under normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel is 38mg / cm³. 3 With a porosity of 99.3%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

[0015] Example 5: A method for preparing a sinter-free silver nanowire aerogel includes the following steps: Step 1: Add 0.8g silver nitrate, 2.7g polyvinylpyrrolidone, and 0.01g copper chloride to 100ml ethylene glycol and react in an oil bath at 180℃ for 3h to obtain a silver nanowire ethylene glycol dispersion; Step 2: Centrifuge and concentrate the silver nanowire ethylene glycol dispersion, discard the supernatant, and wash with alcohol three times for 30 minutes each time; Step 3: Centrifuge the sample, discard the supernatant and alcohol, and add 50ml of water to obtain a silver nanowire aqueous dispersion; Step 4: Add 1mg silver nitrate to the dispersion; Step 5: Freeze-solidify the sample and maintain it in a low-temperature solid state under a 100W UV lamp for 2 hours to obtain a silver nanowire hydrogel, at which point the contact points of the silver nanowires are welded by secondary silver nanoparticles; Step 6: Dry the sample under normal pressure to obtain a silver nanowire aerogel. The density of the prepared silver nanowire aerogel is 12mg / cm³. 3 With a porosity of 99.7%, the prepared silver nanowire aerogel was used for seawater desalination by thermal distillation.

Claims

1. A method for preparing a non-sintering silver nanowire aerogel, characterized by the following steps: Step 1, silver nanowires are synthesized using silver nitrate, ethylene glycol, polyvinylpyrrolidone, and copper chloride as raw materials via a polyol method; Step 2, the silver nanowires in ethylene glycol are centrifuged and concentrated, the supernatant is discarded, and the nanowires are soaked in anhydrous ethanol to remove the polyvinylpyrrolidone (PVP) coating on the surface of the silver nanowires; Step 3, the sample is centrifuged and the supernatant ethanol is discarded, and water is added to adjust the concentration of silver nanowire aqueous dispersions; Step 4, silver nitrate is added to the dispersion and the sample is frozen at low temperature to form a solid state, so that the ice crystals compress the non-aqueous components such as silver nanowires and silver nitrate at the ice crystal boundaries; Step 5, the sample is kept in a low-temperature solid state and placed under a UV lamp for photoreduction to obtain a silver nanowire hydrogel, at which point the contact points of the silver nanowires are welded by secondary nano-silver; Step 6, the sample is dried at normal pressure to obtain a silver nanowire aerogel.

2. According to claim 1, a method for preparing a non-sintering silver nanowire aerogel, wherein the low-temperature cryogenic molding temperature is -20 to -40°C.

3. According to claim 1, a method for preparing a non-sintering silver nanowire aerogel, wherein the power of the ultraviolet lamp is 5 to 100 watts.

4. According to claim 1, a method for preparing a non-sintering silver nanowire aerogel, wherein the standing time under ultraviolet light is 2 to 12 hours.

5. An application of a non-sintering silver nanowire aerogel for seawater desalination by thermal distillation.

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