High aspect ratio copper nanowires and methods of making the same

Abstract

This invention relates to the field of nanomaterial preparation, specifically disclosing a method for preparing copper nanowires, comprising the following steps: (a) dissolving copper chloride dihydrate in deionized water; (b) adding glucose, sodium borohydride, and hexadecylamine, mixing for a period of time until a sky-blue suspension is obtained; (c) reacting at a certain temperature for a period of time; cooling to room temperature, and washing to obtain the copper nanowires. This invention also discloses the copper nanowires.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically a high aspect ratio copper nanowire and its preparation method. Background Technology

[0002] Silver and copper nanowires, due to their high electrical and thermal conductivity, as well as their high flexibility and high aspect ratio, have broad application prospects in micro-nanoelectronics, optoelectronics, sensors, and biomedicine. Their superior performance as transparent conductors is particularly noteworthy, and they can effectively improve the low electrical and thermal conductivity problems of polymer materials. However, copper has 1000 times the reserves of silver, and its electrical conductivity is second only to silver. Therefore, copper nanowires are currently one of the most effective materials for improving the thermal and electrical conductivity of polymer materials.

[0003] Research has shown that the practical application performance of copper nanowires is closely related to their diameter and aspect ratio. The higher the aspect ratio, the larger the diameter (generally ranging from 6-50 nm, with a length typically below 30 μm and an aspect ratio of approximately 2000), and the better their electrical and thermal conductivity.

[0004] Generally, the preparation of copper nanowires is a one-step process. Copper salts typically form copper nuclei, which act as seeds, and then gradually grow into copper particles or wires as energy increases. However, the formation of copper nuclei is uncontrollable in the early stages of the reaction, making it difficult to control the diameter of the copper nanowires. This results in poor experimental reproducibility. Furthermore, existing methods do not consider the influence of the pH value of the reaction environment on the copper nuclei.

[0005] This invention is proposed for this purpose. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, the present invention provides a simple, convenient, controllable reaction condition, and reproducible method for preparing copper nanowires with a high aspect ratio; another objective of the present invention is to provide copper nanowires with a high aspect ratio.

[0007] The technical solution of the present invention is as follows:

[0008] The present invention discloses a method for preparing high aspect ratio copper nanowires, comprising the following steps:

[0009] (a) Dissolve a certain amount of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water, stir for a period of time until completely dissolved, and that is solution A.

[0010] (b) Weigh a certain amount of glucose and sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add a certain amount of hexadecylamine and stir for a period of time until a sky-blue suspension is formed, which is a copper-based complex. This is denoted as solution B.

[0011] (c) Take a portion of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. React it at a certain temperature for a period of time. After the reaction is completed and cooled, wash it with deionized water and alcohol 3 to 6 times and store it in acetone.

[0012] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0013] Further, in steps (a, b), the molar ratio of copper chloride dihydrate, glucose, sodium borohydride and hexadecylamine is 1:1.05-1.1:0.04-0.07:1.3-1.6, wherein the concentration of copper chloride dihydrate is 0.02-0.04 mol / L.

[0014] Furthermore, in step (b), after adding hexadecylamine, the stirring time is 2 to 12 hours until the solution is a sky-blue suspension.

[0015] Furthermore, in step (c), the reaction time in the reactor is 4–10 h, and the reaction temperature is 80–140 °C.

[0016] Further, in step (c), the sample is washed 3 to 6 times with deionized water and alcohol, respectively.

[0017] Furthermore, in step (d), the diameter of the copper nanowires can be observed by electron microscopy to be between 10 and 30 nm; the length is 40-120 μm, and the aspect ratio is not less than 4000, exhibiting a high aspect ratio.

[0018] The reaction principle of this invention is as follows: By forming a copper-based complex in a reducing environment, the energy from the hydrothermal reaction promotes the formation of copper nuclei from copper ions. Hexadecylamine, as a surfactant, selectively adsorbs onto the surface of the copper nuclei. As the energy increases, due to the effect of hexadecylamine, the copper grows along the {100} plane, gradually becoming copper needles, and finally copper wires.

[0019] The beneficial effects of this invention are:

[0020] 1. The preparation method of the present invention is simple, safe, and does not require the use of an oil bath;

[0021] 2. The copper nanowires obtained by this invention have an ultra-high aspect ratio, with a diameter range of 10-30nm, and the diameter can be controlled to be as low as 10nm with a high aspect ratio. The beginning and end are not visible, and the length ranges from about 40-120μm. The aspect ratio is not less than 4000, while the aspect ratio of commercially available copper nanowires is generally around 3000.

[0022] 3. The preparation method of this invention uses a combination of sodium borohydride and glucose, which can reduce copper ions using a dual reducing agent. Under the action of the surfactant hexadecylamine, copper nanowires are slowly grown during the reaction. The copper nanowires obtained by the preparation method of this invention have uniform morphology and are all linear; the diameter and length can be adjusted according to the reaction time and the reaction temperature.

[0023] 4. The preparation method of the present invention does not require adjustment of the pH value of the system, and is highly operable. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the copper nanowires prepared in Example 5.

[0025] Figure 2 This is a transmission electron microscope (TEM) image of the copper nanowires prepared in Example 5.

[0026] Figure 3 This is the energy spectrum of the copper nanowires prepared in Example 5.

[0027] Figure 4 This is a scanning electron microscope image of the copper nanowires prepared in Comparative Example 3.

[0028] Figure 5 This is a scanning electron microscope image of the product prepared in Comparative Example 5. Detailed Implementation

[0029] To make the objectives and technical solutions of this invention clearer, detailed descriptions are provided below in conjunction with specific embodiments. These embodiments are intended to illustrate the content of this invention and not to further limit the scope of protection of this invention. The processes, conditions, reagents, experimental methods, etc., used in the implementation, except as specifically mentioned below, are all common knowledge and general knowledge in the field, and this invention does not impose any particular limitations. Experimental methods in the embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the manufacturer's recommendations. Unless otherwise stated, all technical terms and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art to which this invention pertains. However, in case of conflict, this specification, including the definitions, shall prevail.

[0030] Example 1: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0031] (a) Dissolve 0.04 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0032] (b) Weigh 0.042 mol of glucose and 0.0016 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.060 mol of hexadecylamine and stir for 2 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0033] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 100℃ and the reaction time is 4 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0034] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0035] Example 2: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0036] (a) Dissolve 0.06 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0037] (b) Weigh 0.0642 mol of glucose and 0.0024 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.082 mol of hexadecylamine and stir for 4 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0038] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 80℃ and the reaction time is 6 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0039] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0040] Example 3: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0041] (a) Dissolve 0.06 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0042] (b) Weigh 0.066 mol of glucose and 0.0036 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.09 mol of hexadecylamine and stir for 8 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0043] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 100℃ and the reaction time is 4 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0044] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0045] Example 4: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0046] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0047] (b) Weigh 0.0856 mol of glucose and 0.0048 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.12 mol of hexadecylamine and stir for 12 h until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0048] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 140℃ and the reaction time is 4 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0049] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0050] Example 5: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0051] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0052] (b) Weigh 0.0872 mol of glucose and 0.0056 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.128 mol of hexadecylamine and stir for 5 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0053] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 120°C and the reaction time is 8 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0054] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0055] Example 6: A method for preparing copper nanowires with ultra-high aspect ratio, comprising the following steps:

[0056] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0057] (b) Weigh 0.0856 mol of glucose and 0.0048 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.12 mol of hexadecylamine and stir for 12 h until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0058] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 140℃ and the reaction time is 4 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0059] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0060] Comparative Example 1, same as Example 5, but without the addition of glucose:

[0061] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0062] (b) Weigh 0.0056 mol of sodium borohydride and add it to solution A. Stir until completely dissolved, then add 0.128 mol of hexadecylamine and stir for 5 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0063] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 120°C and the reaction time is 8 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0064] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0065] Comparative Example 2, same as Example 5, but without the addition of sodium borohydride:

[0066] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0067] (b) Weigh 0.0872 mol of glucose and add it to solution A. Stir until completely dissolved, then add 0.0128 mol of hexadecylamine and stir for 5 hours until a sky-blue suspension is formed, which is a copper-based complex. This is denoted as solution B.

[0068] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 120°C and the reaction time is 8 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0069] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0070] Comparative Example 3, same as Example 2, but with a shorter mixing time:

[0071] (a) Dissolve 0.06 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0072] (b) Weigh 0.0642 mol of glucose and 0.0024 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.082 mol of hexadecylamine and stir for 0.5 h. The solution is a mixture of suspension and solution, and is denoted as solution B.

[0073] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 80℃ and the reaction time is 6 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0074] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0075] Comparative Example 4, same as Example 2, but without the addition of glucose and sodium borohydride:

[0076] (a) Dissolve 0.06 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0077] (b) Without adding a reducing agent, 0.082 mol of hexadecylamine was added directly, and after stirring for 4 hours, a suspension was obtained, which was denoted as solution B;

[0078] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 80℃ and the reaction time is 6 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0079] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0080] Comparative Example 5, same as Example 5, but without the addition of hexadecylamine:

[0081] (a) Dissolve 0.08 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0082] (b) Weigh 0.0872 mol of glucose and 0.0056 mol of sodium borohydride and add them to solution A in sequence. Stir for 5 hours until completely dissolved, and record this as solution B.

[0083] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 120°C and the reaction time is 8 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol, and store it in acetone.

[0084] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0085] Comparative Example 6, same as Example 2, but with a shorter reaction time:

[0086] (a) Dissolve 0.06 mol of copper chloride dihydrate granules in an Erlenmeyer flask containing 500 ml of deionized water and stir for a period of time until completely dissolved. This is solution A.

[0087] (b) Weigh 0.066 mol of glucose and 0.0036 mol of sodium borohydride and add them to solution A in sequence. Stir until completely dissolved. Then add 0.09 mol of hexadecylamine and stir for 8 hours until a sky-blue suspension is formed. This is a copper-based complex and is denoted as solution B.

[0088] (c) Take 60 ml of solution B and put it into a reaction vessel lined with polytetrafluoroethylene. The reaction temperature is 100℃ and the reaction time is 0.5 h. After the reaction is completed and cooled, wash it 3 to 6 times with deionized water and alcohol and store it in acetone.

[0089] (d) Its phase and morphology were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy.

[0090] The products obtained from Examples 1 to 6 and Comparative Examples 1 to 6 were analyzed for phase and microstructure using X-ray diffraction and scanning electron microscopy. The results are shown in the figures and tables below.

[0091]

[0092] In the table above: S1 to S6 represent Examples 2 to 6, and D1 to D6 represent Comparative Examples 1 to 6.

[0093] Figure 1 This is a scanning electron microscope image of the copper nanowires prepared in Example 5. Figure 2 This is a transmission electron microscope (TEM) image of the copper nanowires prepared in Example 5. Figure 3 This is the energy spectrum of the copper nanowires prepared in Example 5; Figure 4 This is a scanning electron microscope (SEM) image of the copper nanowires prepared in Comparative Example 3. Figures 1-3 It can be seen that the copper nanowires prepared by this invention have a linear morphology and no other morphology overall. Figure 4 It can be seen that when hexadecylamine is introduced, without sufficient stirring time, the product consists of copper wires and copper carbon oxides, with linear and granular morphologies and uneven sizes. Figure 5 It can be seen that when the surfactant hexadecylamine is not introduced, the product is particulate single-phase copper.

[0094] The results in the table show that, based on Examples 1 to 6, the diameter of the copper nanowires produced is determined by the hydrothermal reaction temperature and reaction time. Within a certain range, the longer the reaction time and the higher the temperature, the larger the diameter of the copper nanowires. However, when the temperature exceeds 140°C, the product is still copper nanowires, but the diameter change is not significant. Because hydrothermal reactions aim for low energy consumption and low pollution, temperatures exceeding 140°C are not considered. Similarly, after the reaction time exceeds a certain period, the diameter change is also not significant.

[0095] From Examples 5, 1, and 2, it can be seen that when using a single reducing agent, the product is copper and copper oxide. Energy dispersive spectroscopy (EDS) analysis shows that the linear product is single-phase copper, and the particulate product is copper oxide. Using two reducing agents is necessary to ensure the product is single-phase copper and has a completely linear morphology. From Comparative Example 4, it can be seen that when there is no reducing agent and only the surfactant hexadecylamine, no copper nanowire product is produced. This is because copper always exists in the form of copper ions. Comparing Example 2 with Comparative Example 3, it can be seen that after adding the surfactant hexadecylamine, stirring is required for at least 2 hours for the solution to transform into a sky-blue suspension and become a copper-based complex. Therefore, to ensure the product is linear single-phase copper, stirring and mixing are required for at least 2 hours after adding hexadecylamine. Comparing Comparative Example 6 with Example 3, it can be seen that the hydrothermal reaction time is at least 4 hours to obtain copper nanowires. From Comparative Example 5, it can be seen that when the surfactant hexadecylamine is not introduced, the product is particulate single-phase copper, such as… Figure 5 As shown, this indicates that in order to obtain linear copper products, a surfactant needs to be added to promote their growth in the same direction.

[0096] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the materials and novel features disclosed herein.

Claims

1. A method for preparing copper nanowires, characterized in that, The copper nanowires have a diameter of 10-30 nm, a length of 40-120 μm, and an aspect ratio of not less than 4000. The preparation method includes the following steps: (a) Dissolve copper chloride dihydrate in deionized water and mix thoroughly to obtain a copper chloride solution, denoted as solution A; the concentration of copper chloride is 0.02~0.04 mol / L; (b) Weigh a certain amount of glucose, sodium borohydride, and hexadecylamine and place them in solution A in sequence. Mix for a period of time until a sky-blue suspension forms, which is a copper-based complex, and denoted as solution B. The molar ratio of copper chloride dihydrate, glucose, sodium borohydride, and hexadecylamine is 1:(1.05~1.1):(0.04~0.07):(1.3~1.6); the mixing time is 2~12 h. (c) React solution B at a certain temperature for a period of time, the reaction temperature is 80~140℃ and the reaction time is 4~10 h; cool to room temperature and wash with deionized water and alcohol 3-6 times respectively to obtain the copper nanowires.

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