Method for hydrothermal macroscopic preparation of silver nanowires

Abstract

The invention discloses a method for hydrothermal macro-quantity preparation of silver nanowires, which comprises the following steps of: reacting a mixed aqueous solution of PVP (Polyvinyl Pyrrolidone), silver nitrate and sodium chloride at 160-180 DEG C for 16-48 hours to prepare the silver nanowires, in the mixed aqueous solution, the mass concentration ratio of silver nitrate to sodium chloride is 1: (1-2.5). According to the preparation method of the silver nanowire, the silver nanowire with the average diameter ranging from 30 nm to 55 nm and the length capable of reaching 150 microns or above can be prepared, and the silver nanowire has unique optical, electrical and thermal performance and has application value in the emerging technical fields of microelectronics, photoelectric devices, sensors and the like.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a method for hydrothermal mass preparation of silver nanowires. Background Art

[0002] One-dimensional metal nanomaterials have unique optical, electrical and thermal properties and are widely used in emerging technology fields such as microelectronics, optoelectronic devices, sensors, etc. In particular, one-dimensional silver nanowires have great application potential in catalysis, surface-enhanced Raman technology, optical devices, sensor technology and other fields. One-dimensional silver nanowires with high length diameters have attracted increasing attention due to their excellent mechanical, thermal, optoelectronic and catalytic properties. In order to realize the commercialization of nanowires, large-scale production and preparation of silver nanowires are necessary.

[0003] There are many methods for preparing silver nanowires, including hydrothermal method, template method, electrochemical method, microwave-assisted method, wet chemical method, polyol method, etc. At present, the polyol method is the main way to mass-produce silver nanowires, but the silver nanowires prepared by the polyol method require complex purification steps to be put into use. In addition, the use of organic reagents is harmful to the environment and the production cost is high. These disadvantages can be avoided by synthesizing silver nanowires in an aqueous system. In addition, the hydrothermal method has the advantages of simple preparation method, good dispersion of the prepared silver nanowires and low cost. However, it is still difficult to achieve large-scale preparation of high aspect ratio silver nanowires by the hydrothermal method. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a method for hydrothermal mass preparation of silver nanowires, which can obtain silver nanowires with a diameter range of 30 to 55 nm and a length of up to 150 μm.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention provides a method for hydrothermal mass production of silver nanowires, comprising the following steps:

[0007] The mixed aqueous solution of PVP, silver nitrate and sodium chloride is reacted at 160-180° C. for 16-48 hours to obtain the silver nanowires; in the mixed aqueous solution, the mass concentration ratio of silver nitrate to sodium chloride is 1:(1-2.5).

[0008] In the present invention, PVP is used as a reducing agent, and the mass concentration ratio of silver nitrate to sodium chloride is controlled to be 1: (1-2.5), so as to effectively control the nucleation sites to be moderate, prevent excessive sodium chloride from increasing the nucleation sites and shortening the length of the silver nanowires, and react at 160-180° C. for 16-48 hours to make the reaction sufficient to obtain silver nanowires with a moderate diameter range and a length of more than 150 μm.

[0009] In some embodiments of the present invention, the reaction time is 16 to 48 hours, such as 20 to 40 hours, 30 hours; too short or too long a reaction time may result in a decrease in the length of the silver nanowires.

[0010] In some embodiments of the present invention, the mass concentration ratio of silver nitrate to sodium chloride is 1:(1.2-2.4).

[0011] In some embodiments of the present invention, in the mixed aqueous solution, the molar concentration of PVP is 40 to 1500 mmol / L, such as 100 to 1500 mmol / L, 300 to 1500 mmol / L.

[0012] In some embodiments of the present invention, the molar concentration of the silver nitrate solution in the mixed aqueous solution is 40 to 80 mmol / L. In the present invention, too low a concentration of silver nitrate will result in a reduced utilization rate of PVP, which will greatly increase production costs in industrial production.

[0013] In some embodiments of the present invention, the molar concentration of sodium chloride in the mixed aqueous solution is 60-120 mmol / L, such as 60-100 mmol / L, 65-95 mmol / L.

[0014] In some embodiments of the present invention, the hydrothermal method for preparing silver nanowires in large quantities further comprises adding a PVP solution to the reaction product for sedimentation to obtain the silver nanowires. In the present invention, PVP is used as a reducing agent in the hydrothermal reaction; after the reaction is completed, PVP is continued to be added as a coating agent to allow the product to be precipitated and separated. Compared with the general centrifugation method, adding PVP for flocculation sedimentation can achieve one-time processing of more products without introducing additional impurities.

[0015] In some embodiments of the present invention, the sedimentation is repeated 2 to 5 times.

[0016] In some embodiments of the present invention, the molar concentration of the PVP solution is 300-500 mmol / L, such as 350 mmol / L, 400 mmol / L, 450 mmol / L; at this molar concentration, the amount of the PVP solution added is 0.8-2 times the volume of the silver wire solution, such as 1 times, 1.5 times, 1.8 times, etc.

[0017] In some embodiments of the present invention, the PVP includes at least one of PVP-K13-18, PVP-K23-27, PVP-K30, and PVP-K90.

[0018] In some embodiments of the present invention, the hydrothermal method for preparing silver nanowires in large quantities comprises the following steps:

[0019] Stirring the PVP aqueous solution and the silver nitrate solution for 20 to 40 minutes to obtain a first mixed aqueous solution;

[0020] Adding sodium chloride solution to the first mixed aqueous solution, and continuing stirring for 40 to 90 minutes to obtain a second mixed aqueous solution;

[0021] The second mixed aqueous solution is placed at 160-180° C. to react for 16-48 hours, and then the PVP solution is added for precipitation, and the process is repeated 2-5 times to obtain the silver nanowires.

[0022] In some embodiments of the present invention, the stirring rate is 800-1200 rpm, such as 900 rpm, 1000 rpm, 1100 rpm, etc.

[0023] The second aspect of the present invention provides silver nanowires produced by the hydrothermal method for preparing silver nanowires in large quantities.

[0024] In some embodiments of the present invention, the silver nanowires have an average diameter of 30 to 55 nm and a length of 50 to 180 μm, such as 80 to 180 μm.

[0025] The third aspect of the present invention provides an application of the silver nanowires in microelectronic devices, optoelectronic devices, and sensors.

[0026] The beneficial effects of the present invention are:

[0027] The present invention uses silver nitrate as a silver source and PVP as a reducing agent and a coating agent, and uses a hydrothermal method at 160 to 180° C. to prepare silver nanowires with an average diameter range of 30 to 55 nm and a length of more than 150 μm. The silver nanowires have unique optical, electrical, and thermal properties and have application value in emerging technology fields such as microelectronics, optoelectronic devices, and sensors.

[0028] The silver nanowires prepared by the method of the present invention have uniform morphology and a yield greater than 70%. The method is simple to operate, avoids the use of a large amount of organic solvents to achieve environmental protection purposes, and has strong repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the XRD diagram of silver nanowires in Example 1 of the present invention.

[0030] Figure 2 These are the SEM images (a, b), HRTEM image (c), and electron diffraction image (d) of the silver nanowires in Example 1 of the present invention.

[0031] Figure 3 These are SEM images of silver nanowires of Examples 2 (a), 3 (b), 4 (c), 5 (d), 6 (e), 7 (f), 8 (g), and 9 (h) of the present invention.

[0032] Figure 4 This is the SEM image of the silver nanowires in Example 10 of the present invention.

[0033] Figure 5 These are SEM images of silver nanowires in comparative examples 1 (a), 2 (b), 3 (c), and 4 (d) of the present invention.

[0034] Figure 6 This is the SEM image of the silver nanowires in comparative example 5 of the present invention.

[0035] Figure 7 These are SEM images of silver nanowires before (left) and after (right) precipitation by adding PVP in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0037] Example 1

[0038] This embodiment prepares a silver nanowire, and the specific process is as follows:

[0039] 1.5 g PVP-K30 was added to 12 mL water, heated and stirred at 65 ° C to prepare a PVP-K30 aqueous solution, 0.272 g silver nitrate was added to 8 mL water and stirred under light-proof conditions to prepare a silver nitrate aqueous solution, and 0.14 g sodium chloride was added to 12 mL water and stirred to prepare a sodium chloride aqueous solution. The silver nitrate aqueous solution and the PVP aqueous solution were mixed and stirred at 1000 rpm for 30 minutes, and then the sodium chloride aqueous solution was added and stirred at 1000 rpm for 1 hour. Among them, the PVP concentration in the mixed solution was 4.2×10 2mmol / L, silver nitrate concentration is 50mmol / L, sodium chloride concentration is 75mmol / L. The mixed solution is transferred to a reactor, placed in an oven for heating, and reacted at 170°C for 24 hours. After the reaction is completed, wait for the reactor to cool to room temperature, take out the sample, add a 400mmol / L PVP aqueous solution with the same volume concentration as the sample to the obtained gray-green solution, let it stand for 5 hours, pour out the supernatant, add the PVP aqueous solution again, repeat 3 times, and finally obtain silver nanowires A, separate the product by sedimentation, take the bottom precipitate, and vacuum dry the product with a yield of about 70%.

[0040] Example 2

[0041] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the method of Example 1, except that the concentration of PVP-K30 in the mixed solution is reduced to 40 mmol / L to obtain silver nanowire B1. The product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 70%.

[0042] Example 3

[0043] In this embodiment, a silver nanowire was prepared. The preparation method was carried out according to the method of embodiment 1, except that the concentration of PVP-K30 in the mixed solution was increased to 1.5×10 3 mmol / L, silver nanowires B2 were obtained, the product was separated by sedimentation, the bottom precipitate was taken, and the product yield was about 70% after vacuum drying.

[0044] Example 4

[0045] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the method of Example 1, except that the concentration of NaCl in the mixed solution is reduced to 60 mmol / L to obtain silver nanowire C1, the product is separated by sedimentation, the bottom precipitate is taken, and the product yield is about 70% after vacuum drying.

[0046] Example 5

[0047] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the method of Example 1, except that the concentration of NaCl in the mixed solution is increased to 120 mmol / L to obtain silver nanowire C2. The product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 50%.

[0048] Example 6

[0049] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the embodiment 1, except that the reaction time is 16 hours. Silver nanowire D1 is prepared, the product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 50%.

[0050] Example 7

[0051] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the embodiment 1, except that the reaction time is 48 hours. Silver nanowire D2 is prepared, the product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 70%.

[0052] Example 8

[0053] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the embodiment 1, except that the reaction temperature is 160° C., and the silver nanowire E1 is prepared. The product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 70%.

[0054] Example 9

[0055] In this embodiment, a silver nanowire is prepared. The preparation method is carried out according to the embodiment 1, except that the reaction temperature is 180°C, and the silver nanowire E2 is prepared. The product is separated by sedimentation, and the bottom precipitate is taken. After vacuum drying, the product yield is about 70%.

[0056] Example 10

[0057] This embodiment prepares a silver nanowire, and the specific process is as follows:

[0058] 37.5 g of PVP-K30 was added to 300 mL of water, heated and stirred at 65 ° C to prepare a PVP-K30 aqueous solution, 6.7948 g of silver nitrate was added to 200 mL of water and stirred under light-proof conditions to prepare a silver nitrate aqueous solution, and 3.5 g of sodium chloride was added to 300 mL of water and stirred to prepare a sodium chloride aqueous solution. The silver nitrate aqueous solution and the PVP aqueous solution were mixed and stirred at 1000 rpm for 30 minutes, and then the sodium chloride aqueous solution was added and stirred at 1000 rpm for 1 hour. Among them, the PVP concentration in the mixed solution was 4.2×10 2 mmol / L, silver nitrate concentration is 50mmol / L, sodium chloride concentration is 75mmol / L. The mixed solution was transferred to a 1L reactor, placed in an oven for heating, and reacted at 170°C for 24 hours. After the reaction was completed, the reactor was cooled to room temperature, the sample was taken out, and a PVP aqueous solution with the same volume concentration of 400mmol / L as the sample was added to the obtained gray-green solution, and the solution was allowed to stand for 5 hours. The supernatant was poured out, and the PVP aqueous solution was added again, and the reaction was repeated 3 times to finally obtain silver nanowires. The product was separated by sedimentation, and the bottom precipitate was taken. After vacuum drying, the product yield was about 70%.

[0059] Comparative Example 1

[0060] In this comparative example, a silver nanowire was prepared. The preparation method was carried out according to Example 1, except that the concentration of PVP-K30 in the mixed solution was replaced with 15 mmol / L, and no silver nanowire was prepared.

[0061] Comparative Example 2

[0062] In this comparative example, a silver nanowire was prepared. The preparation method thereof was carried out with reference to Example 1, except that the concentration of NaCl in the mixed solution was replaced with 20 mmol / L, and no silver nanowire was prepared.

[0063] Comparative Example 3

[0064] In this comparative example, a silver nanowire was prepared. The preparation method thereof was carried out with reference to Example 1, except that the reaction time was replaced with 14 hours, and no silver nanowire was prepared.

[0065] Comparative Example 4

[0066] In this comparative example, a silver nanowire was prepared. The preparation method thereof was carried out with reference to Example 1, except that the reaction temperature was replaced with 150° C., and no silver nanowire was prepared.

[0067] Comparative Example 5

[0068] In this comparative example, a silver nanowire was prepared. The preparation method was carried out according to Example 1, except that the concentration ratio of AgNO3 to NaCl in the mixed solution was controlled to be 1:2.7, and silver nanowire F5 was obtained. The product was separated by sedimentation, and the bottom precipitate was taken. After vacuum drying, the yield was about 50%.

[0069] Test example

[0070] This test example characterizes the prepared silver nanowires, specifically:

[0071] Figure 1 XRD of the silver nanowires prepared in Example 1 Figure 4 The diffraction peaks correspond to the (111), (200), (220), and (311) crystal planes of face-centered cubic silver (JCPDS NO.04-0783). Figure 1 It can be seen that there are no other impurity peaks, which proves that the silver nanowires prepared in Example 1 are of high purity.

[0072] Figure 2 a and b are SEM images of the silver nanowires prepared in Example 1. Figure 2 c is the HRTEM image of the silver nanowires prepared in Example 1, Figure 2 d is the selected area electron diffraction pattern of the silver nanowires prepared in Example 1. Figure 2 From a and b, we can see that the average diameter of the silver nanowires prepared in Example 1 is 35 nm, and the aspect ratio is as high as 2800. Figure 2 c It can be seen that there are clear lattice fringes in the image, which indicates that the crystal structure of the silver nanowire has a high degree of crystallinity. The lattice distances of 0.236nm and 0.202nm shown in the image are consistent with the crystal plane spacing of the (111) and (200) planes. The selected area electron diffraction pattern of the silver nanowire is shown in Figure 2 d, indicating that the diffraction spots can be compared with the Ag <112> and <001> Diffraction patterns are indexed.

[0073] Figure 3 The SEM images of the silver nanowires prepared in Examples 2 to 9 are shown in FIG. Figure 3 a is the SEM image of the silver nanowires prepared in Example 2, Figure 3 b is the SEM image of the silver nanowires prepared in Example 3, Figure 3 c is the SEM image of the silver nanowires prepared in Example 4, Figure 3 d is the SEM image of the silver nanowires prepared in Example 5, Figure 3 e is the SEM image of the silver nanowires prepared in Example 6, Figure 3 f is the SEM image of the silver nanowires prepared in Example 7, Figure 3 g is the SEM image of the silver nanowires prepared in Example 8, Figure 3 h is the SEM image of the silver nanowires prepared in Example 9. Figure 3 From a to h, it can be seen that silver nanowires were obtained in Examples 2 to 9.

[0074] Figure 4 This is the SEM image of the industrially prepared silver nanowires in Example 10.

[0075] Figure 5 The SEM images of the products obtained based on Comparative Examples 1 to 4 are shown in FIG. Figure 5 a is the SEM image of the product prepared in Comparative Example 1, Figure 5 b is the SEM image of the product prepared in Comparative Example 2, Figure 5 c is the SEM image of the product prepared in Comparative Example 3, Figure 5 d is the SEM image of the product prepared in Comparative Example 4. Figure 5 No silver nanowires were found in a~d, that is, comparative examples 1~4 did not successfully prepare silver nanowires.

[0076] Figure 6 This is a SEM image of the product obtained in Comparative Example 5. Excessive NaCl will lead to an increase in nucleation sites, thereby shortening the length of the silver nanowires.

[0077] Figure 7 The SEM images of silver nanowires before (left) and after (right) precipitation after adding PVP in Example 1. It can be seen that the particles in the SEM image after precipitation are reduced, and this method effectively removes other impurities except silver nanowires.

[0078] The average length of the silver nanowires was obtained from the low-magnification SEM image, where Example 1 was approximately 150 μm; Example 2 was approximately 25 μm; Example 3 was approximately 100 μm; Example 4 was approximately 84 μm; Example 5 was approximately 30 μm; Example 6 was approximately 30 μm; Example 7 was approximately 50 μm; Example 8 was approximately 60 μm; Example 9 was approximately 80 μm; Example 10 was approximately 150 μm; and Comparative Example 5 was approximately 25 μm.

[0079] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing silver nanowires in large quantities by hydrothermal method, characterized in that: The following steps are involved: The mixed aqueous solution of PVP, silver nitrate and sodium chloride is reacted at 160-180° C. for 16-48 hours to obtain the silver nanowires; in the mixed aqueous solution, the mass concentration ratio of silver nitrate to sodium chloride is 1:(1-2.5).

2. The method for preparing silver nanowires by hydrothermal method according to claim 1, characterized in that: The mass concentration ratio of the silver nitrate to the sodium chloride is 1:(1.2-2.4).

3. The method for preparing silver nanowires by hydrothermal method according to claim 1, characterized in that: In the mixed aqueous solution, the molar concentration of PVP is 40-1500 mmol / L, such as 100-1000 mmol / L, 300-600 mmol / L.

4. The method for preparing silver nanowires by hydrothermal method according to claim 1, characterized in that: In the mixed aqueous solution, the molar concentration of the silver nitrate solution is 40-80 mmol / L.

5. The method for preparing silver nanowires by hydrothermal method according to claim 1, characterized in that: In the mixed aqueous solution, the molar concentration of sodium chloride is 60-120 mmol / L.

6. The method for preparing silver nanowires in large quantities by hydrothermal method according to claim 1, characterized in that: The hydrothermal method for preparing silver nanowires in large quantities also includes adding a PVP solution to the reaction product for precipitation to obtain the silver nanowires.

7. The method for preparing silver nanowires in large quantities by hydrothermal method according to claim 1, characterized in that: The method for preparing silver nanowires in large quantities by hydrothermal method comprises the following steps: Stirring the PVP aqueous solution and the silver nitrate solution for 20 to 40 minutes to obtain a first mixed aqueous solution; Adding sodium chloride solution to the first mixed aqueous solution, and continuing stirring for 40 to 90 minutes to obtain a second mixed aqueous solution; The second mixed aqueous solution is placed at 160-180° C. to react for 16-48 hours, and then the PVP solution is added for precipitation, and the process is repeated 2-5 times to obtain the silver nanowires.

8. Silver nanowires prepared by the method for preparing silver nanowires in large quantities by hydrothermal method according to any one of claims 1 to 7.

9. The silver nanowire according to claim 8, characterized in that: The average diameter of the silver nanowires is 30 to 55 nm, and the length is 50 to 180 μm.

10. Use of the silver nanowire according to claim 8 or 9 in microelectronic devices, optoelectronic devices and sensors.

Images