CN115740434A - Silver nanowire and separation and purification method thereof - Google Patents
Silver nanowire and separation and purification method thereof Download PDFInfo
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Abstract
A silver nanowire and a separation and purification method thereof relate to the technical field of nano material preparation; the method comprises the following steps: s1, adding acetone into a crude silver nanowire product to settle silver nanowires, performing solid-liquid separation, and dispersing the sediment into absolute ethyl alcohol to obtain a silver nanowire/ethanol dispersion liquid; and S2, carrying out negative pressure suction filtration on the silver nanowire/ethanol dispersion liquid by using a microporous filter membrane under stirring, and washing to obtain the separated and purified silver nanowires. According to the separation and purification method, the separation and purification of the silver nanowires are carried out by combining an acetone washing process and a negative pressure-stirring filtering process, so that the purity of the silver nanowires is effectively improved; the process is simple, the operation is easy, and the prepared silver nanowire has high purity and length-diameter ratio, controllable diameter and narrow distribution, and has good popularization and application values.
Description
Technical Field
The invention belongs to the technical field of nano material preparation, and particularly relates to a silver nanowire and a separation and purification method thereof.
Background
With the increasing development demand of the current flexible electronic product field, the silver nanowire is regarded as an excellent substitute of the traditional transparent conductive thin film indium tin oxide by virtue of excellent photoelectric properties such as conductivity, transparency, bending resistance and the like. However, in the synthesis and preparation process of the silver nanowires, byproducts such as silver nanoparticles and silver nanorods are inevitably generated, and the haze and the photoelectric property of the transparent conductive film are seriously affected. Therefore, a purification process of silver nanowires is crucial to the development of silver nanowires.
Conventional silver nanowire purification methods include centrifugation, conventional filtration, positive or negative pressure filtration, sedimentation separation, and the like. The centrifugation method is to remove the nanoparticles by using different rotation speeds required for the deposition of the nanowires and the nanoparticles, and if the centrifugation time is too long or the speed is too high, the large-diameter nanoparticles will settle together with the silver nanowires and irreversibly form lumps. For example: yuan et al used deionized water and ethanol as washing solvents, and centrifuged many times to obtain a silver nanowire product [ Yu Li,2019]; the method can only remove the small-diameter nano particles in the solution, and has poor separation effect on the silver nanowires and the large-diameter nano particles. The filtration method is an intuitive separation method, and can obtain silver nanowires with fewer nanoparticles and short rods. For example: kim et al used a conventional filtration operation to separate the silver nanowires [ Kim T,2013]; this method can simply obtain purified silver nanowires, but forms irreversible coagulation of silver nanowires, and is inconvenient for achieving a balance between purification effect and dispersibility. Most of the filtration methods reported so far achieve filtration by positive or negative pressure (vacuum filtration). For example: wan and its companion adopt positive pressure filtration method to separate by-products [ Wan M,2018] such as silver nanoparticle from crude product; according to the preparation method, after pressure is applied, the silver nanowires are very easy to connect together to form a filter cake, so that the membrane pores are blocked, the silver nanowires are agglomerated under pressure, and the silver nanowires cannot be redispersed, and the like, and large-scale production and application cannot be performed. Therefore, there is a need to develop a method for purifying silver nanowires that is non-destructive, simple to scale up, and continuously operable.
Disclosure of Invention
In order to overcome the defects of the prior art, one of the purposes of the invention is to provide a method for separating and purifying silver nanowires, which can purify the silver nanowires and remove byproducts, and has simple process and easy operation.
The second purpose of the invention is to provide a high-purity silver nanowire.
One of the purposes of the invention is realized by adopting the following technical scheme:
a separation and purification method of silver nanowires comprises the following steps:
s1, adding acetone into a crude silver nanowire product to settle silver nanowires, performing solid-liquid separation, and dispersing the sediment into absolute ethyl alcohol to obtain a silver nanowire/ethanol dispersion liquid;
and S2, carrying out negative pressure suction filtration on the silver nanowire/ethanol dispersion liquid by using a microporous filter membrane under stirring, and washing to obtain the separated and purified silver nanowires.
Further, in the step S1, the concentration of the silver nanowires in the silver nanowire/ethanol dispersion liquid is 0.15-0.6mg/mL.
Further, in step S2, the pore size of the microporous filter membrane is 1-10 μm.
Further, in step S2, the stirring speed is 200-1000rpm, and the suction filtration flow rate is 5-10L/min.
Further, in step S2, the flushing operation is: and (3) washing and dispersing the materials by adopting absolute ethyl alcohol, wherein the washing amount of an absolute ethyl alcohol washing liquid is 100-150mL each time, and circularly washing for 4-6 times.
Further, the preparation method of the silver nanowire crude product comprises the following steps:
1) Under the protection of inert gas, heating the composite diol solvent, and sequentially adding a PVP solution, a NaBr solution and a NaCl solution to obtain a mixed solution;
2) Dissolving silver nitrate in a composite glycol solvent to obtain a silver nitrate solution;
3) And (3) dropwise adding the silver nitrate solution obtained in the step 2) into the mixed solution obtained in the step 1), fully stirring, heating for reaction, and naturally cooling to obtain a silver nanowire crude product.
Further, in the step 1), the compound diol solvent is a composition of more than two of ethylene glycol, 1, 3-propanediol and 1, 3-butanediol; the temperature of the temperature rise is 150-170 ℃.
Further, in the step 1), the concentration of the PVP solution is 0.50-0.65mol/L; the concentration of the NaBr solution is 0.20-0.35mol/L, and the concentration of the NaCl solution is 0.20-0.35mol/L;
in the step 2), the dissolving is ultrasonic treatment in ice bath and dark, and the treatment time is 15-30min.
Further, the specific operation of step 3) is: dropwise adding the silver nitrate solution into the mixed solution at a dropping speed of 1.0-1.5mL/min, fully stirring, heating to 175-185 ℃ within 15min, closing nitrogen, cooling to 165-175 ℃, reacting at a constant temperature for 15-20min, and naturally cooling to obtain a silver nanowire crude product.
The second purpose of the invention is realized by adopting the following technical scheme:
the high-purity silver nanowire is prepared by the separation and purification method of the silver nanowire.
Compared with the prior art, the invention has the beneficial effects that:
according to the method for separating and purifying the silver nanowires, the silver nanowires are separated and purified by combining an acetone washing process and a negative pressure-stirring filtering process, so that the purity of the silver nanowires is effectively improved; the acetone washing process is that acetone is added to settle the silver nanowires from the mixed solution of the crude silver nanowire product, and the excessive organic reagent is effectively removed through simple solid-liquid separation; meanwhile, on the basis of a conventional filtering process, a mechanical stirring process and a negative pressure adjusting process are added to form a set of negative pressure-stirring filtering process, so that byproducts such as silver nanoparticles and the like can be effectively removed from a crude product, and a silver nanowire product is purified. In addition, the purification method of the silver nanowires has simple process and easy operation, and the prepared silver nanowires have high purity and long-diameter ratio, controllable diameter and narrow distribution, and have good popularization and application values.
The high-purity silver nanowire disclosed by the invention is high in purity, high in length-diameter ratio and narrow in diameter distribution, and has great application prospects.
Drawings
Fig. 1 is an SEM image of a silver nanowire crude product prepared in example 1 of the present invention.
Fig. 2 is an SEM image of purified silver nanowires prepared in example 1 of the present invention.
Fig. 3 is an infrared spectrum of the silver nanowire prepared in example 1 of the present invention after the silver nanowire is not purified and purified.
FIG. 4 is a SEM image of the metallographic phase of a sample treated by a negative pressure-stirring filtration process in comparative example 1 in which washing redispersion operation was not employed according to the present invention.
FIG. 5 is a SEM image of the metallographic phase of a sample treated by a negative pressure-stirring filtration process of a washing redispersion operation in example 1 of the present invention.
FIG. 6 is an SEM image of a sample filtered from a 0.3mg/mL silver nanowire/ethanol dispersion of example 1.
Fig. 7 is an SEM picture of a sample after filtering the silver nanowire/ethanol dispersion with the concentration of 0.15mg/mL in example 4 of the present invention.
FIG. 8 is an SEM image of a sample filtered from the 0.6mg/mL silver nanowire/ethanol dispersion of example 5.
FIG. 9 is an SEM photograph of a filtrate obtained by filtering an unpurified crude silver nanowire product in comparative example 2 of the present invention using a microfiltration membrane having a pore size of 3 μm.
FIG. 10 is an SEM photograph of a filtrate obtained by filtering an unpurified crude silver nanowire product in comparative example 3 of the present invention using a microfiltration membrane having a pore size of 5 μm.
FIG. 11 is an SEM photograph of a filtrate obtained by filtering an unpurified crude silver nanowire product in comparative example 4 of the present invention using a microfiltration membrane having a pore size of 10 μm.
Fig. 12 is an SEM picture of the purified silver nanowire product after filtering the silver nanowires using a microfiltration membrane having a pore size of 3 μm according to example 6 of the present invention.
FIG. 13 is an SEM photograph of purified silver nanowire products obtained by filtering silver nanowires through a microfiltration membrane having a pore size of 5 μm in example 7 according to the present invention.
Fig. 14 is an SEM image of a silver nanowire product after purification by filtering silver nanowires using a microfiltration membrane having a pore size of 10 μm in example 1 of the present invention.
Detailed Description
The present invention is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.
Example 1
A filtering and purifying method of silver nanowires comprises the following steps:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Dissolving silver nitrate in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature was slowly raised to 180 ℃ within 15 minutes, the nitrogen was turned off and the temperature was lowered to 170 ℃ and the temperature was maintained for 1 hour to complete the reaction. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B, step B: firstly, pretreating a silver nanowire crude product by using acetone, settling the silver nanowire from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowire in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL to obtain a silver nanowire/ethanol dispersion solution. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of suction filtration is 5L/min; and (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Example 2
This example is different from example 1 in the kind of the mixed solvent in step A; the method specifically comprises the following steps:
step A: ethylene glycol and 1, 3-butanediol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-butanediol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then, silver nitrate was dissolved in a mixed solvent of ethylene glycol and 1, 3-butanediol in a volume ratio of 1. After the temperature is slowly raised to 180 ℃ within 15 minutes, the nitrogen is closed and the temperature is reduced to 170 ℃, and the reaction is finished by keeping the temperature for 1 hour. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B: firstly, pretreating a silver nanowire crude product by using acetone, precipitating the silver nanowire from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowire in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of suction filtration is 5L/min; in the suction filtration process, absolute ethyl alcohol is adopted to wash and disperse the materials, 100mL of absolute ethyl alcohol is added each time, and the circulation is carried out for 4 times to obtain a final sample.
Example 3
This example differs from example 1 in the concentration of NaBr solution, naCl solution and PVP solution in step a; the method comprises the following specific steps:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.35mol/L NaBr solution, 0.35mol/L NaCl solution and 0.65mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then, silver nitrate was dissolved in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature was slowly raised to 180 ℃ within 15 minutes, the nitrogen was turned off and the temperature was lowered to 170 ℃ and the temperature was maintained for 1 hour to complete the reaction. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B, step B: firstly, pretreating a crude product of the silver nanowires by using acetone, precipitating the silver nanowires from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowires in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of the suction filtration was 5L/min. And (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Example 4
The difference between this embodiment and embodiment 1 lies in the concentration of the diluted solution in step B, which specifically includes:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then dissolving silver nitrate in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature was slowly raised to 180 ℃ within 15 minutes, the nitrogen was turned off and the temperature was lowered to 170 ℃ and the temperature was maintained for 1 hour to complete the reaction. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B: firstly, pretreating a silver nanowire crude product by using acetone, precipitating the silver nanowire from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowire in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.15mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of suction filtration was 5L/min. In the suction filtration process, absolute ethyl alcohol is adopted to wash and disperse the materials, 100mL of absolute ethyl alcohol is added each time, and the circulation is carried out for 4 times to obtain a final sample.
Example 5
The difference between this example and example 1 lies in the concentration of the diluted solution in step B being different, specifically:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then dissolving silver nitrate in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature was slowly raised to 180 ℃ within 15 minutes, the nitrogen was turned off and the temperature was lowered to 170 ℃ and the temperature was maintained for 1 hour to complete the reaction. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B, step B: firstly, pretreating a crude product of the silver nanowires by using acetone, precipitating the silver nanowires from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowires in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.6mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of the suction filtration was 5L/min. And (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Example 6
The difference between this embodiment and embodiment 1 lies in that the pore size of the microporous filter membrane in step B is different, specifically:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then, silver nitrate was dissolved in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature is slowly raised to 180 ℃ within 15 minutes, the nitrogen is closed and the temperature is reduced to 170 ℃, and the reaction is finished by keeping the temperature for 1 hour. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B: firstly, pretreating a crude product of the silver nanowires by using acetone, precipitating the silver nanowires from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowires in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 3 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; and (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Example 7
The difference between this embodiment and embodiment 1 lies in that the pore size of the microporous filter membrane in step B is different, specifically:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then dissolving silver nitrate in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature is slowly raised to 180 ℃ within 15 minutes, the nitrogen is closed and the temperature is reduced to 170 ℃, and the reaction is finished by keeping the temperature for 1 hour. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B: firstly, pretreating a silver nanowire crude product by using acetone, precipitating the silver nanowire from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowire in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 5 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of the suction filtration was 5L/min. The vacuum pressure of the suction filtration is 80Pa; and (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Example 8
The difference between this embodiment and embodiment 1 lies in the process parameters of the negative pressure-stirring filtration process in step B, which specifically include:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Then, silver nitrate was dissolved in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature is slowly raised to 180 ℃ within 15 minutes, the nitrogen is closed and the temperature is reduced to 170 ℃, and the reaction is finished by keeping the temperature for 1 hour. Naturally cooling to room temperature to obtain a silver nanowire crude product, as shown in fig. 1.
And B: firstly, pretreating a silver nanowire crude product by using acetone, precipitating the silver nanowire from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowire in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed in the negative pressure-stirring filtration process is 800 r/min; the flow rate of the suction filtration was 10L/min. And (3) in the suction filtration process, washing and dispersing the material by using absolute ethyl alcohol, supplementing 100mL of absolute ethyl alcohol each time, and circulating for 4 times to obtain a final sample.
Comparative example 1
This comparative example differs from example 1 in that: the silver nanowire separation and purification process in the step B does not adopt washing redispersion operation, and specifically comprises the following steps:
step A: ethylene glycol and 1, 3-propylene glycol are taken as solvents, and 0.20mol/L NaBr solution, 0.20mol/L NaCl solution and 0.50mol/L PVP solution are prepared in advance respectively. Adding 50mL of ethylene glycol and 50mL of 1, 3-propylene glycol into a round-bottom flask under the protection of nitrogen, heating to 150 ℃, and then sequentially adding PVP, naBr and NaCl solution. Dissolving silver nitrate in a mixed solvent of ethylene glycol and 1, 3-propylene glycol in a volume ratio of 1. After the temperature is slowly raised to 180 ℃ within 15 minutes, the nitrogen is closed and the temperature is reduced to 170 ℃, and the reaction is finished by keeping the temperature for 1 hour. Naturally cooling to room temperature to obtain the silver nanowire crude product.
And B: firstly, pretreating a crude product of the silver nanowires by using acetone, precipitating the silver nanowires from an original mixed solution by using 100mL of acetone, fully dispersing the silver nanowires in absolute ethyl alcohol after solid-liquid separation, and diluting to 0.3mg/mL. Then pouring 100mL of silver nanowire/ethanol dispersion into a Buchner funnel with mechanical stirring, and carrying out negative pressure suction filtration on the silver nanowire dispersion under stirring by using a microporous filter membrane with the pore diameter of 10 mu m, wherein the stirring speed is 200 r/min in the negative pressure-stirring filtration process; the flow rate of the suction filtration is 5L/min, and the final sample is obtained.
Comparative example 2
This comparative example differs from example 6 in that: and (3) directly filtering the silver nanowire crude product by using a microporous filter membrane with the pore diameter of 3 mu m.
Comparative example 3
This comparative example differs from example 7 in that: and directly filtering the silver nanowire crude product by using a microporous filter membrane with the pore diameter of 5 mu m.
Comparative example 4
The comparative example differs from example 1 in that: and (3) directly filtering the silver nanowire crude product by using a microporous filter membrane with the pore diameter of 10 mu m.
Performance testing
1. Analytical experiments for isolation and purification
SEM image analysis and infrared spectrogram analysis were performed on the silver nanowire crude product sample before and after the separation and purification treatment in example 1, respectively, and the results are shown in fig. 1 to 3.
As shown in fig. 1, it is apparent that the crude product without purification contains a large amount of impurities. The impurities are mainly divided into two types, one is organic reagent impurities (such as black films, various random non-particle substances and the like in an SEM picture) which are mainly mixed polyalcohol solvent and consist of excessive unreacted PVP raw material and the like; the other is the by-product impurities (such as short rods, particles and the like in the SEM partial enlarged view) of silver nanoparticles, silver nanorods and the like generated in the synthesis process. The silver nanowire crude products prepared in examples 1 to 3 were synthesized by the polyol blend method, so that the crude products prepared in examples 2 and 3 were similar to example 1, and repeated analysis experiments were not performed.
According to different properties of the two impurities, the method combines the washing process of acetone and the negative pressure-stirring filtration process to purify the crude product of the silver nanowires. As shown in FIG. 2, the purified silver nanowires have no obvious impurities, the average diameter of the silver nanowires is 41nm, the average length of the silver nanowires is 45 μm, and the obtained silver nanowires have higher length-diameter ratio and narrower diameter distribution. As shown in FIG. 3, infrared spectroscopic analysis shows that the separation and purification method of the invention can effectively remove the by-products, and the purity of the silver nanowires after the separation and purification method is extremely high.
2. Experiment of Effect of flushing Dispersion
In this experiment, the products of example 1 and comparative example 1 were examined and analyzed by metallographic SEM, and the results are shown in fig. 4 to 5.
As can be seen from FIGS. 4 to 5, the sample obtained by filtration without rinsing the filter membrane of comparative example 1 still had a portion of impurities such as silver nanoparticles and silver nanorods left unremoved; in contrast, the sample after washing the membrane in example 1 had a significant reduction in impurities and, more importantly, a significant increase in aspect ratio. In the purification process, the operation of flushing the filter membrane to redisperse the silver nano product is added in the negative pressure-stirring filtration process, so that the coagulation of the silver nano wires and the blockage of the pore passages of the filter membrane can be effectively prevented, and more and thinner silver nano wires with high length-diameter ratio can be obtained under control.
3. Experiment of influence of concentration of silver nanowire/ethanol dispersion on length
In this experiment, the silver nanowire products of examples 1 and 4 to 5 were examined and analyzed by SEM, and the results are shown in fig. 6 to 8.
Referring to fig. 6, the silver nanowire/ethanol dispersion of example 1 has a dilution concentration of 0.3mg/mL, and the silver nanowires having a length of 40 to 50 μm in the obtained silver nanowire product account for about 60% of the total amount, and has a narrow length distribution range and a high aspect ratio; referring to fig. 7, the dilution concentration of the silver nanowire/ethanol dispersion of example 4 is 0.15mg/mL, and most of the lengths of the obtained silver nanowire product are distributed between 30 μm and 50 μm, which is wider than that in comparative example 1; referring to fig. 8, the silver nanowire/ethanol dispersion of example 5 was diluted to a concentration of 0.6mg/mL, and the silver nanowires having the same length of 40 to 50 μm accounted for about 60% of the total amount of the obtained silver nanowire product, but the content of the silver nanowires having a length of 30 μm or less was significantly increased.
4. Influence experiment of microporous filter membrane aperture and filtering process
1) SEM detection analysis is carried out on the filtrate of the silver nanowire crude product by using the microporous filter membranes with different pore diameters in the comparative examples 2-4, and the results are shown in figures 9-11.
2) SEM detection analysis was performed on the final silver nanowire products after the silver nanowires were purified in examples 1 and 6 to 7 by using microporous filter membranes with different pore sizes, and the results are shown in FIGS. 12 to 14.
As shown in FIGS. 9 to 11, in comparative examples 2 to 4, the coarse product of the silver nanowires without purification treatment was filtered by microporous filter membranes with pore sizes of 3 μm, 5 μm and 10 μm, respectively, and the coarse product was contaminated with particles, short silver nanowires and low filtration efficiency. As shown in fig. 12-14, in examples 1 and 6-7, on the basis of a conventional filtering apparatus, a mechanical stirring system and a negative pressure regulating system are added to form a set of negative pressure-stirring filtering process apparatus, which can effectively remove by-products such as silver nanoparticles and the like from a crude product and obtain more and finer silver nanowires with high aspect ratio; meanwhile, compared with the silver nanowire product processed by the microporous filter membrane of 3-5 microns, the average length of the silver nanowire product processed by the microporous filter membrane of 10 microns is larger.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. A method for separating and purifying silver nanowires is characterized by comprising the following steps:
s1, adding acetone into a crude silver nanowire product to settle silver nanowires, performing solid-liquid separation, and dispersing the sediment into absolute ethyl alcohol to obtain a silver nanowire/ethanol dispersion liquid;
and S2, carrying out negative pressure suction filtration on the silver nanowire/ethanol dispersion liquid by using a microporous filter membrane under stirring, and washing to obtain the separated and purified silver nanowires.
2. The method for separating and purifying silver nanowires of claim 1, wherein: in the step S1, the concentration of the silver nanowires in the silver nanowire/ethanol dispersion liquid is 0.15-0.6mg/mL.
3. The method for separating and purifying silver nanowires of claim 1, wherein: in step S2, the aperture of the microporous filter membrane is 1-10 μm.
4. The method for separating and purifying silver nanowires of claim 1, wherein: in step S2, the stirring speed is 200-1000rpm, and the flow rate of suction filtration is 5-10L/min.
5. The method for separating and purifying silver nanowires of claim 1, wherein in step S2, the rinsing operation is: and (3) washing and dispersing the materials by adopting absolute ethyl alcohol, wherein the washing amount of an absolute ethyl alcohol washing liquid is 100-150mL each time, and circularly washing for 4-6 times.
6. The method for separating and purifying silver nanowires of claim 1, wherein the method for preparing the crude product of silver nanowires comprises the following steps:
1) Under the protection of inert gas, heating the composite diol solvent, and sequentially adding a PVP solution, a NaBr solution and a NaCl solution to obtain a mixed solution;
2) Dissolving silver nitrate in a composite glycol solvent to obtain a silver nitrate solution;
3) And (3) dropwise adding the silver nitrate solution obtained in the step 2) into the mixed solution obtained in the step 1), fully stirring, heating for reaction, and naturally cooling to obtain a silver nanowire crude product.
7. The method for separating and purifying silver nanowires of claim 6, wherein: in the step 1), the compound diol solvent is a composition of more than two of ethylene glycol, 1, 3-propylene glycol and 1, 3-butanediol; the temperature of the temperature rise is 150-170 ℃.
8. The method for separating and purifying silver nanowires according to claim 6, wherein: in the step 1), the concentration of the PVP solution is 0.50-0.65mol/L; the concentration of the NaBr solution is 0.20-0.35mol/L, and the concentration of the NaCl solution is 0.20-0.35mol/L;
in the step 2), the dissolving is ultrasonic treatment in ice bath and dark place, and the treatment time is 15-30min.
9. The method for separating and purifying silver nanowires of claim 6, wherein: the specific operation of step 3) is as follows: dropwise adding the silver nitrate solution into the mixed solution at a dropping speed of 1.0-1.5mL/min, fully stirring, heating to 175-185 ℃ within 15min, closing nitrogen, cooling to 165-175 ℃, reacting at a constant temperature for 15-20min, and naturally cooling to obtain a silver nanowire crude product.
10. A high purity silver nanowire characterized by: is prepared by the method for separating and purifying the silver nanowires of any one of claims 1 to 9.
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