A method for separating and purifying nanosilver wires

Abstract

The present application relates to the technical field of nanometer silver wire separation and purification, and particularly relates to a nanometer silver wire separation and purification method, comprising the following steps: (1) preparing nanometer silver wire by using a polyol solvothermal method to obtain a mixed solution containing nanometer silver wire and ethylene glycol; (2) taking alcohol-decomposing bacteria and preparing cell suspension; (3) taking the mixed solution obtained in step (1) and adding it to one side of a semi-permeable membrane, taking the cell suspension obtained in step (2) and adding it to the other side of the semi-permeable membrane, and performing separation and decomposition of ethylene glycol, and continuously decomposing to obtain nanometer silver wire solution after separation and purification. The present application decomposes ethylene glycol, a by-product in the preparation process of nanometer silver wire, by using alcohol-decomposing bacteria, thereby avoiding the use of acetone washing in the traditional separation and purification method, the bending problem of nanometer silver wire caused by mechanical impact in the washing process, greatly reducing the bending rate, maintaining the morphology of nanometer silver wire in a complete manner, avoiding the use of toxic washing agent, being green and environmentally friendly, and being low in cost and simple in operation.

Description

Technical Field

[0001] This invention relates to the field of silver nanowire separation and purification technology, and in particular to a method for separating and purifying silver nanowires. Background Technology

[0002] Nanowires are nanoscale devices (1 nanometer = 10⁻⁶). -9 Nanowires are one-dimensional structures with a transverse dimension limited to less than 100 nanometers (with no longitudinal limitation). At this scale, quantum mechanical effects are significant, hence they are also called quantum wires. Depending on the constituent materials, nanowires can be classified into different types, including metallic nanowires (e.g., Ni, Pt, Au), semiconductor nanowires (e.g., InP, Si, GaN), and insulating nanowires (e.g., SiO2, TiO2). Molecular nanowires are composed of repeating molecular units and can be organic (e.g., DNA) or inorganic (e.g., Mo6S9-xIx). As an important component of nanotechnology, nanowires can be used to fabricate ultra-small circuits. One-dimensional silver nanowires exhibit unique physicochemical properties due to their high axis-to-diameter ratio structure and are widely used in fields such as conductivity, thermal conductivity, sterilization, catalysis, and biological and chemical sensors. Based on their outstanding conductivity, light transmittance, and mechanical flexibility, silver nanowire transparent electrodes have broad market prospects in flexible wearable electronic devices such as flexible touchscreens, flexible displays, flexible solar cells, and flexible OLEDs. In addition to silver's excellent conductivity, silver nanowires also exhibit superior light transmittance and flexibility due to their nanoscale size effect. Therefore, they are considered the most promising material to replace traditional ITO transparent electrodes, offering possibilities for flexible, bendable LED displays and touchscreens, and numerous studies have already explored their application in thin-film solar cells. Furthermore, the high aspect ratio of silver nanowires also gives them significant advantages in applications such as conductive adhesives and thermally conductive adhesives.

[0003] Currently, many methods for preparing silver nanowires have been developed. Among these methods, the polyol solvothermal method has become the most important method for preparing silver nanowires due to its low cost, simple operation, and high yield. The polyol solvothermal method generally involves adding a silver nitrate solution to an ethylene glycol solution containing PVP and halides, and reacting at a certain temperature to obtain silver wires. The drawback of this method is that the environment in which the silver nanowires are formed is ethylene glycol and silver nitrate. The next step is to replace the ethylene glycol in the silver nanowires. The conventional method is to wash with acetone, which uses a large amount of toxic acetone, is costly and environmentally unfriendly, and the impact during the organic solvent washing process can easily cause the silver nanowires to agglomerate and bend, affecting the use of subsequent products. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for separating and purifying silver nanowires, based on existing separation and purification processes.

[0005] On one hand, the present invention provides a method for separating and purifying silver nanowires, comprising the following steps:

[0006] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0007] (2) Take the alcohol-degrading bacteria and prepare an alcohol-degrading bacterial solution;

[0008] (3) Take the mixed liquid obtained in step (1) and add it to one side of the semipermeable membrane, and take the alcohol-degrading bacterial liquid obtained in step (2) and add it to the other side of the semipermeable membrane to separate and decompose ethylene glycol, so as to obtain the separated and purified nano-silver wire liquid.

[0009] Further, the alcohol-degrading bacteria mentioned in step (2) include one or more of the following: Paracoccus, Bacillus thuringiensis, Bacillus cereus, Bacillus licheniformis, Bacillus pumilus, Bacillus anthracis, and Bacillus megaterium.

[0010] Furthermore, the alcohol-degrading bacteria mentioned in step (2) are alcohol-degrading bacteria in the logarithmic growth phase, and the alcohol-degrading bacterial solution has a density of 5 × 10⁻⁶. 5 ~6×10 5 Single-cell suspension.

[0011] Furthermore, the semipermeable membrane in step (3) is a hollow fiber membrane.

[0012] Furthermore, the hollow fiber membrane includes cellulose acetate hollow fiber membrane, polyamide hollow fiber membrane, polyvinylidene fluoride hollow fiber membrane, and polysulfone hollow fiber membrane.

[0013] Furthermore, in step (3), the liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacteria liquid is added.

[0014] Furthermore, in step (3), peristaltic pumps are provided on both sides of the semipermeable membrane.

[0015] Furthermore, the separation and decomposition time in step (3) is 4-7 days.

[0016] Furthermore, the semipermeable membrane in step (3) consists of 1 to 3 layers, with the layers of semipermeable membrane arranged in parallel to each other.

[0017] Furthermore, the pH value of the alcohol-degrading bacterial solution is 6-8, and the temperature is 25-35℃.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention proposes a novel method for separating and purifying silver nanowires, based on the conventional solvothermal method for preparing silver nanowires. Alcohololytic bacteria are prepared into an alcohololytic bacterial solution. A semi-permeable membrane separates the side receiving the mixed solution from the side receiving the alcohololytic bacterial solution. Ethylene glycol can then diffuse through the semi-permeable membrane to the alcohololytic bacterial solution side, serving as a carbon source for the bacteria's growth. During the growth process, the alcohololytic bacteria continuously consume ethylene glycol, allowing ethylene glycol from the mixed solution side to continuously permeate to the alcohololytic bacterial solution side until the ethylene glycol concentration in the mixed solution side reaches the product usage standard, thus achieving the separation and purification of the silver nanowires. This method decomposes ethylene glycol, a byproduct of the silver nanowire preparation process, avoiding the bending problem of silver nanowires caused by mechanical impact during acetone washing in traditional separation and purification methods. It significantly reduces the bending rate, preserves the morphology of the silver nanowires intact, avoids the use of toxic detergents, is environmentally friendly, low-cost, and simple to operate.

[0020] 2. The method for separating and purifying silver nanowires proposed in this invention allows for smoother ethylene glycol diffusion on the mixed liquid side by setting the liquid level on the mixed liquid side higher than that on the side containing the alcohol-degrading bacteria liquid. A peristaltic pump on the mixed liquid side prevents silver nanowire deposition, which could affect the subsequent performance of the silver nanowires. A peristaltic pump on the alcohol-degrading bacteria liquid side prevents the alcohol-degrading bacteria from clumping together during growth, thus reducing decomposition efficiency. Furthermore, two to three layers of semi-permeable membrane can be arranged in parallel to allow for adjustment of the ethylene glycol concentration on the alcohol-degrading bacteria liquid side based on the ethylene glycol tolerance concentration of different alcohol-degrading bacteria species, thereby maximizing decomposition efficiency. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are morphological photographs of the silver nanowires obtained by separation and purification in Example 1 of this invention.

[0023] Figure 2 These are morphological photographs of the silver nanowires obtained by separation and purification in Example 2 of this invention.

[0024] Figure 3 These are morphological photographs of the silver nanowires obtained by separation and purification in Example 3 of this invention.

[0025] Figure 4 This is a photograph of the morphology of the silver nanowires obtained by separation and purification in Example 4 of the present invention;

[0026] Figure 5 These are morphological photographs of the silver nanowires obtained by separation and purification in Example 5 of this invention.

[0027] Figure 6 This is a morphological photograph of the silver nanowires obtained by separation and purification in Example 6 of the present invention;

[0028] Figure 7 These are morphological photographs of the silver nanowires obtained by separation and purification in Example 7 of this invention.

[0029] Figure 8 This is a photograph of the morphology of the silver nanowires obtained by separation and purification in Comparative Example 1 of this invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. 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 within the protection scope of the present invention.

[0031] Example 1

[0032] This embodiment provides a method for separating and purifying silver nanowires, specifically including the following steps:

[0033] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0034] (2) Take a culture of Paracoccus in the logarithmic growth phase and prepare it with a complete culture medium with a density of 5 × 10⁻⁶. 5 Paracoccus single-cell suspension;

[0035] (3) Take the mixed liquid obtained in step (1) and add it to one side of a single-layered cellulose acetate hollow fiber semipermeable membrane. Take the paracoccus single-cell suspension obtained in step (2) and add it to the other side of the cellulose acetate hollow fiber semipermeable membrane. Peristaltic pumps are set on both sides to slowly stir the liquids on both sides. The liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacteria liquid is added. The pH value on the side where the alcohol-degrading bacteria liquid is added is 7 and the temperature is 30℃. Ethylene glycol separation and decomposition are carried out.

[0036] (4) During the continuous decomposition process, the ethylene glycol content on the mixed liquid side was measured. After 4 days, the mass fraction of ethylene glycol on the mixed liquid side was found to be ≤5%, and the nano silver wire liquid with separation and purification effect met the product use requirements was obtained.

[0037] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 1 As shown. By Figure 1It can be seen that in this example, peristaltic pumps are installed on both the alcohol-degrading bacterial solution side and the mixed liquid side, logarithmic growth phase strains are used, and a single-layer semi-permeable membrane is set to achieve the best purification effect of silver nanowires. The silver nanowires are not bent and have no adverse effects on subsequent use.

[0038] Example 2

[0039] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that a peristaltic pump is not installed on the side where the alcohol-degrading bacterial solution is added in this embodiment. The specific steps include:

[0040] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0041] (2) Take a mixed bacterial suspension of Bacillus anthracis and Bacillus megaterium in the logarithmic growth phase and prepare it with a density of 5 × 10⁻⁶ in complete culture medium. 5 Single-cell suspension;

[0042] (3) Take the mixed liquid obtained in step (1) and add it to one side of the single-layer polyamide hollow fiber semipermeable membrane. Take the single-cell suspension obtained in step (2) and add it to the other side of the polyamide hollow fiber semipermeable membrane. Only set up a peristaltic pump on the side where the mixed liquid is added to slowly stir the liquid. The liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacteria solution is added. The pH value on the side where the alcohol-degrading bacteria solution is added is 6.5 and the temperature is 32℃. Perform the separation and decomposition of ethylene glycol.

[0043] (4) During the continuous decomposition process, the ethylene glycol content on the mixed liquid side was measured. After 5 days, the mass fraction of ethylene glycol on the mixed liquid side was found to be ≤5%, and the nano silver wire liquid with separation and purification effect met the product use requirements was obtained.

[0044] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 2 As shown. By Figure 2 It can be seen that in this case, no peristaltic pump was set on the alcohol-degrading bacterial solution side, a logarithmic growth phase strain was used, and a single-layer semi-permeable membrane was set up, which achieved a satisfactory purification effect of silver nanowires and a satisfactory dispersibility of silver nanowires.

[0045] Example 3

[0046] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that a peristaltic pump is not installed on the side where the mixed liquid is added in this embodiment. The method specifically includes the following steps:

[0047] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0048] (2) Take a mixed bacterial suspension of Bacillus cereus, Bacillus licheniformis, and Bacillus pumilus in the logarithmic growth phase and prepare it with a density of 6×10⁻⁶ using complete culture medium. 5 Single-cell suspension;

[0049] (3) Take the mixed liquid obtained in step (1) and add it to one side of a single-layer polyvinylidene fluoride hollow fiber semipermeable membrane. Take the mixed single-cell suspension of Bacillus cereus, Bacillus licheniformis, and Bacillus pumilus obtained in step (2) and add it to the other side of the polyvinylidene fluoride hollow fiber semipermeable membrane. Set a peristaltic pump on the side where the alcohol-degrading bacterial solution is added and slowly stir the liquid. The liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacterial solution is added. The pH value on the side where the alcohol-degrading bacterial solution is added is 7 and the temperature is 35℃. Perform the separation and decomposition of ethylene glycol.

[0050] (4) During the continuous decomposition process, the ethylene glycol content on the side of the added mixture was measured. After 5 days, the mass fraction of ethylene glycol on the side of the added mixture was found to be ≤5%, and the nano silver wire material solution with separation and purification effect met the requirements for product use was obtained.

[0051] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 3 As shown. By Figure 3 It can be seen that in this case, no peristaltic pump was installed on the mixed liquid side, and logarithmic growth phase strains were used. The purification effect of the silver nanowires was acceptable, but a small amount of agglomeration and bending of the silver nanowires occurred.

[0052] Example 4

[0053] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that no peristaltic pump is installed on either the side where the mixed liquid is added or the side where the alcohol-degrading bacterial solution is added. The method specifically includes the following steps:

[0054] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0055] (2) Take a culture of Paracoccus in the logarithmic growth phase and prepare it with a complete culture medium with a density of 5 × 10⁻⁶. 5 Single-cell suspension;

[0056] (3) Take the mixed liquid obtained in step (1) and add it to one side of the single-layer polysulfone hollow fiber semipermeable membrane, and take the single cell suspension obtained in step (2) and add it to the other side of the polysulfone hollow fiber semipermeable membrane; the liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacteria liquid is added, the pH value on the side where the alcohol-degrading bacteria liquid is added is 7, and the temperature is 27℃, and the separation and decomposition of ethylene glycol is carried out.

[0057] (4) During the continuous decomposition process, the ethylene glycol content on the side of the added mixture was measured. After 6 days, the mass fraction of ethylene glycol on the side of the added mixture was found to be ≤5%, and the nano silver wire material solution with separation and purification effect met the requirements for product use was obtained.

[0058] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 4 As shown. By Figure 4 It can be seen that in this case, no peristaltic pumps were installed on either the mixed liquid side or the alcohol-degrading bacteria side. Logarithmic growth phase strains were used, and a double-layer semi-permeable membrane was set up. The purification effect of the silver nanowires was acceptable, although a small amount of agglomeration and bending of the silver nanowires occurred.

[0059] Example 5

[0060] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that the bacterial culture selected in this example is not in the logarithmic growth phase. The specific steps include:

[0061] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0062] (2) Take a mixed bacterial culture of Paracoccus and Bacillus thuringiensis in the non-logarithmic growth phase and prepare it with complete culture medium to a density of 5×10⁻⁶. 5 Single-cell suspension;

[0063] (3) Take the mixed liquid obtained in step (1) and add it to one side of the single-layer polyamide hollow fiber semipermeable membrane. Take the single-cell suspension obtained in step (2) and add it to the other side of the polyamide hollow fiber semipermeable membrane. Both the side with the mixed liquid and the side with the alcohol-degrading bacteria solution are equipped with peristaltic pumps to slowly stir the liquids on both sides. The liquid level on the side with the mixed liquid is higher than the liquid level on the side with the alcohol-degrading bacteria solution. The pH value on the side with the alcohol-degrading bacteria solution is 7 and the temperature is 35℃. Ethylene glycol separation and decomposition are carried out.

[0064] (4) During the continuous decomposition process, the ethylene glycol content on the side of the added mixture was measured. After 7 days, the mass fraction of ethylene glycol on the side of the added mixture was found to be ≤5%, and the nano silver wire material solution with separation and purification effect met the requirements for product use was obtained.

[0065] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 5 As shown. By Figure 5 It can be seen that in this example, peristaltic pumps were installed on both the alcohol-degrading bacterial solution side and the mixed liquid side, and non-logarithmic growth phase strains were used. The purification effect of the silver nanowires was acceptable, with no bending of the silver nanowires, but the purification time was relatively long.

[0066] Example 6

[0067] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that this embodiment uses two semi-permeable membrane layers, and specifically includes the following steps:

[0068] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0069] (2) Take a mixed bacterial culture of Paracoccus and Bacillus megaterium in the logarithmic growth phase and prepare it with a density of 6 × 10⁻⁶ using complete culture medium. 5 Single-cell suspension;

[0070] (3) Take the mixed liquid obtained in step (1) and add it to one side of the double-layered parallel cellulose acetate hollow fiber semipermeable membrane. Take the single cell suspension obtained in step (2) and add it to the other side of the cellulose acetate hollow fiber semipermeable membrane. Both the side with the mixed liquid and the side with the alcohol-degrading bacteria solution are equipped with peristaltic pumps to slowly stir the liquids on both sides. The liquid level on the side with the mixed liquid is higher than the liquid level on the side with the alcohol-degrading bacteria solution. The pH value on the side with the alcohol-degrading bacteria solution is 7.5 and the temperature is 28℃. Ethylene glycol separation and decomposition are carried out.

[0071] (4) During the continuous decomposition process, the ethylene glycol content on the side of the added mixture was measured. After 5 days, the mass fraction of ethylene glycol on the side of the added mixture was found to be ≤5%, and the nano silver wire material solution with separation and purification effect met the requirements for product use was obtained.

[0072] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 6 As shown. By Figure 6 It can be seen that in this example, peristaltic pumps were installed on both the alcohol-degrading bacterial solution side and the mixed liquid side, logarithmic growth phase strains were used, and a double-layer semi-permeable membrane was set up to achieve a purification effect of silver nanowires that is similar to that of Example 1. The silver nanowires are not bent and have no adverse effects on subsequent use.

[0073] Example 7

[0074] This embodiment provides a method for separating and purifying silver nanowires. The main difference from Embodiment 1 is that this embodiment uses three semi-permeable membrane layers, and specifically includes the following steps:

[0075] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0076] (2) Take the bacterial suspension of Bacillus cereus in the logarithmic growth phase and prepare it with complete culture medium to a density of 6×10⁻⁶. 5 Single-cell suspension;

[0077] (3) Take the mixed liquid obtained in step (1) and add it to one side of the three parallel polyamide hollow fiber semipermeable membrane. Take the single cell suspension obtained in step (2) and add it to the other side of the polyamide hollow fiber semipermeable membrane. Both the side with the mixed liquid and the side with the alcohol-degrading bacteria solution are equipped with peristaltic pumps to slowly stir the liquids on both sides. The liquid level on the side with the mixed liquid is higher than the liquid level on the side with the alcohol-degrading bacteria solution. The pH value on the side with the alcohol-degrading bacteria solution is 8 and the temperature is 25℃. Ethylene glycol separation and decomposition are carried out.

[0078] (4) During the continuous decomposition process, the ethylene glycol content on the side of the added mixture was measured. After 6 days, the mass fraction of ethylene glycol on the side of the added mixture was found to be ≤5%, and the nano silver wire material solution with separation and purification effect met the requirements for product use was obtained.

[0079] The morphology of the silver nanowires obtained by separation and purification in this embodiment is as follows: Figure 7 As shown. By Figure 7 It can be seen that in this example, peristaltic pumps were installed on the alcoholysis bacterial solution side and the mixed liquid side, logarithmic growth phase strains were used, and three semi-permeable membranes were set up to achieve a purification effect of silver nanowires that is close to that of Example 1. The silver nanowires are not bent and have no adverse effects on subsequent use.

[0080] Comparative Example 1

[0081] This comparative example provides a traditional method for separating and purifying silver nanowires. The main difference from Example 1 is that this example uses acetone washing to separate and purify the silver nanowires, specifically including the following steps:

[0082] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0083] (2) After the mixture obtained in step (1) is cooled, it is separated and purified by centrifugation using acetone, distilled water and anhydrous ethanol at a speed of 0. The impurities such as solvent, stabilizer and complexing agent in the silver nanowire suspension are separated out continuously. Finally, the purified silver nanowires are dispersed in ethanol for preservation to obtain the separated and purified silver nanowire solution.

[0084] The morphology of the silver nanowires obtained by separation and purification in this comparative example is as follows: Figure 8 As shown. By Figure 8 It can be seen that the silver nanowires separated by the traditional acetone washing method exhibited significant agglomeration and bending.

[0085] Comparative Example 2

[0086] This comparative example provides a method for separating and purifying silver nanowires. The main difference from Example 1 is that this example uses a common filter membrane, and specifically includes the following steps:

[0087] (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol;

[0088] (2) Take a culture of Paracoccus in the logarithmic growth phase and prepare it with a complete culture medium with a density of 5 × 10⁻⁶. 5 Single-cell suspension;

[0089] (3) Take the mixed liquid obtained in step (1) and add it to one side of the ordinary silver nanowire filter membrane with a single layer. Take the single cell suspension obtained in step (2) and add it to the other side of the ordinary silver nanowire filter membrane. Both the side with the mixed liquid and the side with the alcohol-degrading bacteria solution are equipped with peristaltic pumps to slowly stir the liquids on both sides. The liquid level on the side with the mixed liquid is higher than the liquid level on the side with the alcohol-degrading bacteria solution. The pH value on the side with the alcohol-degrading bacteria solution is 7 and the temperature is 30℃. Ethylene glycol is separated and decomposed.

[0090] (4) During the continuous decomposition process, the ethylene glycol content on the side of the mixed liquid added is measured by sampling.

[0091] In this comparative example, since ordinary filter membranes can only intercept longer silver nanowires and cannot prevent bacteria from penetrating, and silver nanowires have a bactericidal effect, the bacteria cannot grow and decompose ethylene glycol normally. After 7 days, the mass fraction of ethylene glycol on the side with added mixed liquid was still higher than 5%, which does not meet the production requirements.

[0092] This invention proposes a novel method for the separation and purification of silver nanowires, building upon the conventional solvothermal method for preparing silver nanowires. It utilizes alcohol-degrading bacteria to prepare a single-cell suspension. A semi-permeable membrane separates the side receiving the mixed feed solution from the side receiving the alcohol-degrading bacteria solution. Ethylene glycol can then selectively diffuse through the semi-permeable membrane to the alcohol-degrading bacteria solution side, serving as a carbon source for bacterial growth. During the growth process, the alcohol-degrading bacteria continuously consume ethylene glycol, allowing ethylene glycol from the mixed feed solution side to continuously permeate to the alcohol-degrading bacteria solution side until the ethylene glycol concentration in the mixed feed solution reaches the product usage standard, thus achieving the separation and purification of the silver nanowires. This method decomposes ethylene glycol, a byproduct of the silver nanowire preparation process, avoiding the bending problems caused by mechanical impact during acetone washing in traditional separation and purification methods. It significantly reduces the bending rate, preserves the morphology of the silver nanowires intact, avoids the use of toxic detergents, is environmentally friendly, low-cost, and simple to operate. Meanwhile, the method for separating and purifying silver nanowires proposed in this invention allows for smoother ethylene glycol diffusion on the mixed liquid side by setting the liquid level on the mixed liquid side higher than that on the alcohol-degrading bacteria side. A peristaltic pump on the mixed liquid side prevents the deposition of silver nanowires, thus avoiding impact on their subsequent performance. The peristaltic pump on the alcohol-degrading bacteria side also prevents the bacteria from agglomerating during growth, thus reducing decomposition efficiency. Furthermore, two to three parallel layers of the semi-permeable membrane can be arranged to adjust the ethylene glycol concentration on the alcohol-degrading bacteria side according to the ethylene glycol tolerance concentration of different alcohol-degrading bacteria species, thereby maximizing decomposition efficiency.

[0093] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for separating and purifying silver nanowires, characterized in that, Includes the following steps: (1) Silver nanowires were prepared by polyol solvothermal method to obtain a mixed solution containing silver nanowires and ethylene glycol; (2) Take the alcohol-degrading bacteria and prepare an alcohol-degrading bacterial solution; (3) Take the mixed liquid obtained in step (1) and add it to one side of the semipermeable membrane, and take the alcohol-degrading bacterial liquid obtained in step (2) and add it to the other side of the semipermeable membrane to separate and decompose ethylene glycol, so as to obtain the separated and purified nano-silver wire liquid. The alcohol-degrading bacteria include one or more of the following: Paracoccus, Bacillus thuringiensis, Bacillus cereus, Bacillus licheniformis, Bacillus pumilus, Bacillus anthracis, and Bacillus megaterium. The semipermeable membrane is a hollow fiber membrane; The hollow fiber membrane includes any one of cellulose acetate hollow fiber membrane, polyamide hollow fiber membrane, polyvinylidene fluoride hollow fiber membrane, and polysulfone hollow fiber membrane.

2. The method for separating and purifying silver nanowires according to claim 1, characterized in that, The alcohol-degrading bacteria mentioned in step (2) are alcohol-degrading bacteria in the logarithmic growth phase, and the alcohol-degrading bacterial solution has a density of 5 × 10⁻⁶. 5 ~6×10 5 Single-cell suspension.

3. The method for separating and purifying silver nanowires according to claim 1, characterized in that, Step (3) The liquid level on the side where the mixed liquid is added is higher than the liquid level on the side where the alcohol-degrading bacteria liquid is added.

4. The method for separating and purifying silver nanowires according to claim 1, characterized in that, In step (3), peristaltic pumps are installed on both sides of the semipermeable membrane.

5. The method for separating and purifying silver nanowires according to claim 1, characterized in that, The separation and decomposition process in step (3) takes 4-7 days.

6. The method for separating and purifying silver nanowires according to claim 1, characterized in that, The semipermeable membrane in step (3) consists of 1 to 3 layers, with the layers of semipermeable membrane arranged in parallel to each other.

7. The method for separating and purifying silver nanowires according to claim 1, characterized in that, The pH value of the alcohol-degrading bacteria culture is 6-8, and the temperature is 25-35℃.

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