High-purity copper nanowires and methods for making the same

Abstract

The application provides a high-purity copper nanowire and a preparation method thereof, and the preparation method comprises the following steps: (1) adding hexadecylamine, a copper source and glucose into water, and stirring to obtain a mixed solution; (2) adding cocamide propyl betaine or an aqueous solution containing cocamide propyl betaine into the mixed solution, and stirring to obtain a mixture suspension; (3) heating the mixture suspension to perform a reaction, and obtaining a copper nanowire stock solution; and (4) dispersing the precipitate of the copper nanowire stock solution in an organic solvent after washing to obtain a high-purity copper nanowire dispersion. The application has the characteristics of environmental protection, low cost and high purity of the obtained copper nanowire.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a high-purity copper nanowire and its preparation method. Background Technology

[0002] Copper nanowires not only possess the excellent conductivity of silver, but also exhibit superior light transmittance and flexibility due to the nanoscale size effect. Furthermore, their price is far lower than that of precious metals such as gold and silver, making them an ideal electrode material for fabricating flexible electronic devices.

[0003] Currently, methods for synthesizing copper nanowires using hydrothermal reduction often employ long-chain alkylamines such as HDA (Angew. Chem. 2011, 123, 10748-10752), ODA (Chinese Patent CN108695014B), and OA, which are poorly soluble in water, as end-capping agents. These long-chain alkylamines adsorbed on the surface of the synthesized copper nanowires are difficult to remove, affecting their conductivity. In existing technologies, alcohols are added to the aqueous solvent as co-solvents to improve the solubility of the copper amine complex (Chinese Patent CN115464133A), but this method is relatively expensive.

[0004] Furthermore, during the preparation of copper nanowires, the inability to control the nucleation rate and seed type can lead to the generation of byproducts such as copper nanoparticles or nanocubes, resulting in reduced product yield and agglomeration. Before application, the prepared copper nanowires need to be purified using organic solvents such as hexane and chloroform (Multiphase separation or coppernanowires. Chem. Commun. 2016, 52(78), 11627-11630), or nitrogen or inert gas can be introduced into the polyol reaction system and heated at high temperature to remove water and oxygen from the solvent to obtain high-purity copper nanowires (Chinese Patent CN114603130A). Improper operation can easily cause safety hazards. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a high-purity copper nanowire and its preparation method, which is environmentally friendly, low-cost, and produces high-purity copper nanowires.

[0006] This invention is achieved through the following technical solution:

[0007] A method for synthesizing high-purity copper nanowires includes the following steps:

[0008] (1) Add hexadecylamine, copper source and glucose to water and stir to obtain a mixed solution;

[0009] (2) Add cocamidopropyl betaine or an aqueous solution containing cocamidopropyl betaine to the mixed solution, stir, and obtain a suspension of the mixture;

[0010] (3) The mixture suspension was heated to react and copper nanowire stock solution was obtained;

[0011] (4) The precipitate of the copper nanowire stock solution was washed and then dispersed in an organic solvent to obtain a high-purity copper nanowire dispersion.

[0012] Preferably, in step (1), the molar ratio of copper ions to hexadecylamine in the mixed solution is 1:(4-8), and the molar ratio of copper ions to glucose is 1:(2-4).

[0013] Preferably, in step (1), the copper source is one or more of copper sulfate, copper nitrate, copper chloride, copper acetate, copper acetylacetone, and copper carboxylate.

[0014] Preferably, in step (1), the stirring time is 2 to 5 hours.

[0015] Preferably, in step (2), the molar ratio of hexadecylamine to cocamidopropyl betaine in the mixture suspension is 100:(1-4).

[0016] Preferably, in step (2), the stirring time is 1 to 2 hours.

[0017] Preferably, in step (3), the heating temperature is 100-160°C and the reaction time is 2-24 hours.

[0018] Preferably, in step (4), the organic solvent is one or more of anhydrous ethanol, isopropanol, n-hexane and cyclohexane.

[0019] Preferably, in step (4), the washing process involves washing multiple times with deionized water and isopropanol respectively.

[0020] High-purity copper nanowires were obtained using the synthesis method described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention uses water as a solvent system and adds the stable and inexpensive amphoteric surfactant cocamidopropyl betaine to improve the solubility of the copper-alkylamine complex in aqueous solution, forming a well-dispersed reaction system at room temperature and pressure. The reaction is carried out under ambient pressure to obtain copper nanowires with a diameter of 20–50 nm and a length of over 10 μm, which are almost free of nanoparticles and require no purification before subsequent application. Compared with existing methods for synthesizing copper nanowires, this invention does not require the introduction of polyols or the introduction of inert gases, and the synthesis process is simple, low-cost, environmentally friendly, and highly safe.

[0023] Furthermore, by optimizing the amount of cocamidopropyl betaine added, this invention can obtain copper nanowires with suitable diameter and high purity. Attached Figure Description

[0024] Figure 1 Scanning electron microscope (SEM) images of the copper nanowires synthesized in Example 1 at different magnifications ((a) and (b)) and diameter distribution (c).

[0025] Figure 2 The image shows a scanning electron microscope (SEM) image of the synthesized copper nanowires in Comparative Example 1.

[0026] Figure 3 Scanning electron microscope (SEM) images of the copper nanowires synthesized in Example 2 at different magnifications ((a) and (b)) and diameter distribution (c).

[0027] Figure 4 The image shows a scanning electron microscope (SEM) image of the copper nanowires synthesized in Comparative Example 2.

[0028] Figure 5 This is a scanning electron microscope image of the copper nanowires synthesized in Example 3. Detailed Implementation

[0029] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0030] The method for synthesizing high-purity copper nanowires according to the present invention includes the following steps:

[0031] (1) Disperse hexadecylamine, copper source and glucose in deionized water at room temperature, seal and stir for 2 to 5 hours to obtain a mixed solution;

[0032] (2) Add an aqueous solution containing cocamidopropyl betaine to the mixed solution to improve the solubility of the copper-alkylamine complex, stir for 1 to 2 hours to obtain a suspension of the mixture;

[0033] (3) Transfer the mixture suspension to a reaction vessel, heat to 100-160℃, keep warm for 2-24 hours to obtain copper nanowire stock solution, and cool naturally to room temperature;

[0034] (4) Wash the precipitate of the copper nanowire stock solution and then store it in an organic solvent to obtain the copper nanowire dispersion.

[0035] In step (1) of this invention, the copper source is selected from one or more of copper sulfate, copper nitrate, copper chloride, copper acetate, copper acetylacetone and copper carboxylate.

[0036] In step (1) of the present invention, the organic solvent is one or more of anhydrous ethanol, isopropanol, n-hexane and cyclohexane.

[0037] In step (1) of the present invention, the molar ratio of copper ions to hexadecylamine in the mixed solution is 1:(4-8).

[0038] In step (1) of the present invention, the molar ratio of copper ions to glucose in the mixed solution is 1:(2-4).

[0039] In step (2) of this invention, the molar ratio of hexadecylamine to cocamidopropyl betaine in the mixture suspension is 100:(1-4). Before the synthesis reaction, the mixture suspension is thoroughly stirred at room temperature to ensure that the reactants are mixed evenly.

[0040] In step (3) of this invention, the mixture suspension occupies about 2 / 3 of the volume of the reaction vessel.

[0041] In step (4) of this invention, the precipitate of the copper nanowire stock solution is washed by centrifugation multiple times with deionized water and isopropanol.

[0042] The present invention also provides a method for preparing high-purity copper nanowires.

[0043] Example 1

[0044] This embodiment provides a method for synthesizing high-purity copper nanowires, specifically including the following steps:

[0045] (1) At room temperature, 1g hexadecylamine, 0.12g copper chloride dihydrate and 0.3g glucose were dispersed in 50ml of deionized water and stirred for 4 hours with a magnetic stirrer to obtain a mixed solution.

[0046] (2) Add 0.015g of cocamidopropyl betaine to the mixed solution and stir for 1 hour to obtain a suspension of the mixture;

[0047] (3) Transfer the mixture suspension to a 100ml reaction vessel, heat it to 140℃ in a forced-air oven, and keep it at that temperature for 6 hours;

[0048] (4) Stop heating and wait for the solution temperature to cool to room temperature. Take the lower layer of solution and centrifuge it at 6000 r / min for 5 min. Discard the supernatant and add 40℃ deionized water to the precipitate. Centrifuge it at 6000 r / min for 5 min. Repeat 3 times. Then wash it with isopropanol 3 times to obtain a pure copper nanowire dispersion.

[0049] According to the appendix Figure 1 It can be seen that the copper nanowires prepared by this method have a length of more than 10 μm, an average diameter of 39.02 ± 6.70 nm, and a purity of up to 95%.

[0050] Comparative Example 1

[0051] This comparative example provides a method for synthesizing copper nanowires, which specifically includes the following steps:

[0052] (1) At room temperature, 1g hexadecylamine, 0.12g copper chloride dihydrate and 0.3g glucose were dispersed in 50ml of deionized water and stirred for 5 hours with a magnetic stirrer to obtain a mixed solution.

[0053] (3) Transfer the mixed solution to a 100ml reaction vessel, heat it to 140℃ in a forced-air oven, and keep it at that temperature for 6 hours;

[0054] (4) Stop heating and wait for the solution temperature to cool to room temperature. Take the lower layer of solution and centrifuge it at 6000 r / min for 5 min. Discard the supernatant and add 40℃ deionized water to the precipitate. Centrifuge it at 6000 r / min for 5 min and repeat 3 times. Then wash it with isopropanol 3 times to obtain the copper nanowire dispersion.

[0055] According to the appendix Figure 2 It can be seen that the copper nanowires prepared by this method contain a large number of particles and other byproducts with different morphologies.

[0056] The only difference between Comparative Example 1 and Example 1 is whether or not cocamidopropyl betaine is added. Figure 1 and attached Figure 2 The scanning electron microscopy results show that the addition of cocamidopropyl betaine can effectively improve the purity of copper nanowires.

[0057] Example 2

[0058] This embodiment provides a method for synthesizing high-purity copper nanowires, specifically including the following steps:

[0059] (1) At room temperature, 1g hexadecylamine, 0.12g copper chloride dihydrate and 0.3g glucose were dispersed in 50ml of deionized water and stirred for 4 hours with a magnetic stirrer to obtain a mixed solution.

[0060] (2) Add 0.06g of cocamidopropyl betaine to the mixed solution and stir for 1 hour to obtain a suspension of the mixture;

[0061] (3) Transfer the mixture suspension to a 100ml reaction vessel, heat it to 140℃ in a forced-air oven, and keep it at that temperature for 6 hours;

[0062] (4) Stop heating and wait for the solution temperature to cool to room temperature. Take the lower layer of solution and centrifuge it at 6000 r / min for 5 min. Discard the supernatant and add 40℃ deionized water to the precipitate. Centrifuge it at 6000 r / min for 5 min. Repeat 3 times. Then wash it with isopropanol 3 times to obtain a pure copper nanowire dispersion.

[0063] According to the appendix Figure 3 It can be seen that the copper nanowires prepared by this method have a length greater than 10 μm, an average diameter of 28.96 ± 5.95 nm, and a purity of up to 85%. For details on the morphology and dimensions of the obtained copper nanowires, please refer to [link to relevant documentation]. Figure 3 .

[0064] The only difference between this embodiment and Example 1 is the amount of cocamidopropyl betaine added.

[0065] The scanning electron microscopy results from Examples 1 and 2 show that adding a large amount of cocamidopropyl betaine can reduce the diameter of copper nanowires, but it also makes the surface rougher and reduces the purity.

[0066] Comparative Example 2

[0067] (1) At room temperature, 1 g cetylamine, 0.12 g copper chloride dihydrate, 0.3 g glucose and 0.06 g cocamidopropyl betaine were dispersed in 50 ml of deionized water and stirred for 5 hours with a magnetic stirrer to obtain a mixed suspension.

[0068] (2) Transfer the mixture suspension to a 100ml reaction vessel, heat it to 140℃ in a forced-air oven, and keep it at that temperature for 6 hours;

[0069] (3) Stop heating and wait for the solution temperature to cool to room temperature. Take the lower layer of solution and centrifuge it at 6000 r / min for 5 min. Pour off the supernatant and centrifuge the resulting precipitate in deionized water at 40℃ for 5 min at 6000 r / min. Repeat this process 3 times. Then wash it with isopropanol 3 times to obtain a pure copper nanowire dispersion.

[0070] According to the appendix Figure 4 It can be seen that the copper nanowires obtained by this method are relatively few, with copper nanoparticles and nanosheets being the majority. (See details...) Figure 4 .

[0071] The only difference between Comparative Example 2 and Example 2 is the timing of cocamidopropyl betaine addition. The comparison shows that the timing of cocamidopropyl betaine addition affects the growth of copper nanowires.

[0072] Example 3

[0073] This embodiment provides a method for synthesizing high-purity copper nanowires, specifically including the following steps:

[0074] (1) At room temperature, 1g hexadecylamine, 0.12g copper chloride dihydrate and 0.3g glucose were dispersed in 50ml of deionized water and stirred for 4 hours with a magnetic stirrer to obtain a mixed solution.

[0075] (2) Add 0.045g of cocamidopropyl betaine to the mixed solution and stir for 1 hour to obtain a suspension of the mixture;

[0076] (3) Transfer the mixture suspension to a 100ml reaction vessel, heat it to 140℃ in a forced-air oven, and keep it at that temperature for 6 hours;

[0077] (4) Stop heating and wait for the solution temperature to cool to room temperature. Take the lower layer of solution and centrifuge it at 6000 r / min for 5 min. Discard the supernatant and add 40℃ deionized water to the precipitate. Centrifuge it at 6000 r / min for 5 min. Repeat 3 times. Then wash it with isopropanol 3 times to obtain a pure copper nanowire dispersion.

[0078] According to the appendix Figure 5 It can be seen that the purity of copper nanowires prepared by this method can reach 90%. The morphology of the obtained copper nanowires is detailed in [link to relevant documentation]. Figure 5 .

[0079] The scanning electron microscopy results of Examples 1, 2, and 2 show that the timing and content of cocamidopropyl betaine addition are particularly important for the formation of impurity seed crystals. Appropriate timing and content can reduce the formation of impurities.

[0080] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for synthesizing high-purity copper nanowires, characterized in that, Includes the following steps: (1) Add hexadecylamine, copper source and glucose to water and stir to obtain a mixed solution; (2) Add cocamidopropyl betaine or an aqueous solution containing cocamidopropyl betaine to the mixed solution, stir, and obtain a mixture suspension; in the mixture suspension, the molar ratio of hexadecylamine to cocamidopropyl betaine is 100:(1~4). (3) The mixture suspension was heated to react and copper nanowire stock solution was obtained; (4) The precipitate of the copper nanowire stock solution was washed and dispersed in an organic solvent to obtain a high-purity copper nanowire dispersion.

2. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (1), the molar ratio of copper ions to hexadecylamine in the mixed solution is 1:(4~8), and the molar ratio of copper ions to glucose is 1:(2~4).

3. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (1), the copper source is one or more of copper sulfate, copper nitrate, copper chloride, copper acetate, copper acetylacetone and copper carboxylate.

4. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (1), the stirring time is 2 to 5 hours.

5. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (2), the stirring time is 1 to 2 hours.

6. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (3), the heating temperature is 100~160℃ and the reaction time is 2~24 hours.

7. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (4), the organic solvent is one or more of anhydrous ethanol, isopropanol, n-hexane and cyclohexane.

8. The method for synthesizing high-purity copper nanowires according to claim 1, characterized in that, In step (4), the washing process involves washing multiple times with deionized water and isopropanol.

9. High-purity copper nanowires obtained by the synthesis method according to any one of claims 1 to 8.

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