Carbon nanotube dispersion system, high-purity carbon nanotube oriented array, and method of making

Abstract

The application discloses a carbon nanotube dispersion system, a high-cleanliness carbon nanotube oriented array and a preparation method. The preparation method of the high-cleanliness carbon nanotube oriented array comprises the following steps: uniformly mixing carbon nanotubes, an organic solvent and nitrogen-doped or non-nitrogen-doped pentacene system molecules to form a carbon nanotube dispersion system; immersing a substrate into the carbon nanotube dispersion system in a light-proof environment to prepare a carbon nanotube oriented array; and finally irradiating the carbon nanotube oriented array with ultraviolet rays, and then performing solution immersion and vacuum sublimation to obtain the high-cleanliness carbon nanotube oriented array. The carbon nanotube dispersion system provided by the application uses nitrogen-doped or non-nitrogen-doped pentacene system molecules as a dispersant, and the dispersant can be decomposed by ultraviolet irradiation, so that the dispersant will not be finally left on the surface of the carbon nanotubes, and the high-cleanliness carbon nanotube oriented array can be prepared.

Description

Technical Field

[0001] This invention relates to a carbon nanotube dispersion system, specifically to a carbon nanotube dispersion system for achieving high-purity carbon nanotube orientation array assembly, as well as a high-purity carbon nanotube orientation array and its preparation method, belonging to the field of carbon nanotube assembly technology. Background Technology

[0002] Carbon nanotubes, with their excellent electrical properties and intrinsic material advantages, are considered one of the most promising materials in nanoscience and technology, and are potential candidates for next-generation electronic devices. Industrially produced carbon nanotube powders are typically mixtures of semiconducting and metallic carbon nanotubes. The presence of metallic single-walled carbon nanotubes can cause short circuits in electronic devices, limiting their applications. Separation techniques for semiconducting single-walled carbon nanotubes have developed rapidly in recent years, including density gradient ultracentrifugation, gel chromatography, aqueous two-phase extraction, DNA encapsulation, and conjugated polymer encapsulation. When semiconducting carbon nanotubes are arranged in a high-density orientation in a thin film, they exhibit the highest axial carrier transport characteristics and minimal intertube overlap, fully utilizing the excellent performance of carbon nanotubes. However, current methods for dispersing and assembling carbon nanotubes in organic systems largely rely on conjugated polymer encapsulation, which in turn affects the performance of the carbon nanotube orientation array. Therefore, the purification of carbon nanotube orientation arrays has become a new challenge for application fields.

[0003] To achieve the assembly of highly clean carbon nanotube oriented arrays, researchers have made significant efforts in both solution purification and oriented array film purification. Solution purification primarily focuses on enhancing the removal of polymers from the carbon nanotube surface during the dispersion stage. A common method involves ultrasonically redispersing the carbon nanotubes in an organic solvent with high polymer solubility, ensuring that the polymer on the carbon nanotube surface dissolves as much as possible in the organic solution, followed by solvent removal through filtration. During the carbon nanotube redispersion process, the addition of trifluoroacetic acid can protonate the carbon nanotube surface, enhancing polymer removal efficiency. However, this method has drawbacks: the polymer cannot be completely removed, and repeated washing leads to carbon nanotube loss. Existing methods for purifying the carbon nanotube oriented array film utilize the difference in thermal expansion coefficients between the polymer and carbon nanotubes, employing rapid heating and cooling annealing to remove the side chains of the surface polymer. However, this method also has limitations: although the polymer branches are removed, the polymer backbone remains wrapped around the carbon nanotube surface, resulting in limited purification effectiveness. Summary of the Invention

[0004] The main objective of this invention is to provide a carbon nanotube dispersion system for achieving high-purity carbon nanotube orientation array assembly, thereby overcoming the shortcomings of the prior art.

[0005] Another objective of this invention is to provide a high-purity carbon nanotube orientation array and its preparation method.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a carbon nanotube dispersion system for at least achieving the assembly of highly clean carbon nanotube oriented arrays, comprising: carbon nanotubes, an organic solvent, and a dispersant, wherein the dispersant comprises nitrogen-doped or nitrogen-free pentane system molecules.

[0008] In some embodiments, the dispersant has at least the structure shown in any one of formulas A, B, C, and D:

[0009]

[0010] Among them, Ar includes R, R is selected from at least one of the following groups: a hydrogen atom, a straight chain, a branched chain, or a cyclic alkyl chain having 1 to 20 carbon atoms.

[0011] This invention also provides a method for preparing a high-purity carbon nanotube orientation array, comprising:

[0012] Carbon nanotubes, organic solvents, and dispersants are mixed uniformly to form a carbon nanotube dispersion system, wherein the dispersant includes nitrogen-doped or non-nitrogen-doped pentabenzene system molecules;

[0013] In a light-protected environment, the substrate is immersed in the carbon nanotube dispersion system and a solution rich in hydroxyl groups is added. Then the substrate is pulled out to form a carbon nanotube orientation array on the substrate surface.

[0014] A high-purity carbon nanotube orientation array was prepared by irradiating a substrate with an oriented array of carbon nanotubes on its surface with ultraviolet light, followed by solution immersion and vacuum sublimation.

[0015] This invention also provides a high-purity carbon nanotube orientation array prepared by the aforementioned method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The carbon nanotube dispersion system provided by this invention for assembling high-purity carbon nanotube oriented arrays uses nitrogen-doped or non-nitrogen-doped pentacene system molecules as dispersants. These molecules can be decomposed by ultraviolet irradiation. After solution immersion and vacuum sublimation, no polymer molecules remain on the surface of the carbon nanotubes, thus achieving the preparation of high-purity carbon nanotube oriented arrays. Furthermore, since nitrogen-doped or non-nitrogen-doped pentacene system molecules can be decomposed by ultraviolet light, the cleaning process during redispersion can be simplified, thereby greatly reducing the loss of carbon nanotubes during the process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the process for preparing a high-purity carbon nanotube orientation array in a typical embodiment of the present invention;

[0020] Figure 2 This is a SEM image of the high-purity carbon nanotube orientation array prepared in Example 1 of this invention;

[0021] Figure 3a This is the AFM image of the high-purity carbon nanotube orientation array prepared in Example 1 of this invention;

[0022] Figure 3b This is the AFM image of the carbon nanotube orientation array with a large amount of dispersant polymer residue prepared in Comparative Example 1. Detailed Implementation

[0023] In view of the shortcomings of existing technologies, the inventors of this invention, after long-term research, proposed the technical concept of this invention. The main objective is to achieve the assembly of highly purified carbon nanotube oriented arrays. The invention employs a method that utilizes nitrogen-doped or non-nitrogen-doped pentabenzene system molecules to stably disperse carbon nanotube solutions, and then decomposes the assembled carbon nanotube arrays by ultraviolet irradiation, followed by solution immersion and vacuum sublimation to remove polymer molecules, thereby achieving the preparation of highly purified carbon nanotube oriented arrays. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0024] One aspect of this invention provides a carbon nanotube dispersion system for achieving the assembly of highly clean carbon nanotube oriented arrays, comprising: carbon nanotubes, an organic solvent, and a dispersant. The dispersant includes a nitrogen-doped pentane system molecular dispersant, but is also suitable for undoped pentane molecules. This dispersant can selectively target semiconducting single-walled carbon nanotubes through π-π interactions. Furthermore, due to the large conjugated structure of the molecules and the resulting high bond strain, its structure is unstable and photosensitive, leading to structural decomposition and destruction under high-energy light irradiation, thereby achieving the removal of the dispersant from the surface of the carbon nanotubes.

[0025] In some embodiments, the nitrogen-doped pentacene system molecular dispersant has at least the structure shown in any one of formulas A, B, and C, and structure D is also applicable for nitrogen-free pentacene molecules:

[0026]

[0027] Among them, Ar includes R, R is selected from at least one of the following groups: a hydrogen atom, a straight chain, a branched chain, or a cyclic alkyl chain having 1 to 20 (preferably 6 to 12) carbon atoms, but is not limited thereto.

[0028] In some embodiments, the mass ratio of the dispersant to carbon nanotubes is 4:1 to 5:1.

[0029] In some embodiments, the carbon nanotubes include, but are not limited to, single-walled carbon nanotubes.

[0030] Furthermore, the organic solvent may include any one or a combination of two or more of toluene, xylene, chloroform, dichloromethane, cyclohexane, N-methylpyrrolidone, tetrahydrofuran, etc., but is not limited thereto.

[0031] The carbon nanotube dispersion system provided by this invention for achieving high-purity oriented array assembly can prepare stable and dispersed high-purity carbon nanotube oriented arrays on a large scale, rapidly and continuously.

[0032] As another aspect of the technical solution of the present invention, it also relates to a method for preparing a high-purity carbon nanotube orientation array, which includes:

[0033] Carbon nanotubes, organic solvents, and dispersants are mixed uniformly to form a carbon nanotube dispersion system, wherein the dispersant includes nitrogen-doped or non-nitrogen-doped pentabenzene system molecules;

[0034] In a light-protected environment, the substrate is immersed in the carbon nanotube dispersion system and a solution rich in hydroxyl groups is added. Then the substrate is pulled out to form a carbon nanotube orientation array on the substrate surface.

[0035] A high-purity carbon nanotube orientation array was prepared by irradiating a substrate with an oriented array of carbon nanotubes on its surface with ultraviolet light, followed by solution immersion and vacuum sublimation.

[0036] This invention utilizes the characteristic that nitrogen-doped or undoped pentacene system molecules can be decomposed by ultraviolet irradiation, thereby achieving high purity of the oriented carbon nanotube array and eliminating the influence of polymers on the performance of carbon nanotubes. The structures of the nitrogen-doped or undoped pentacene system molecules are as defined above.

[0037] In some more specific implementation examples, the preparation method includes: placing carbon nanotubes and a dispersant in an organic solvent and mixing them evenly, then centrifuging to collect the supernatant to obtain the carbon nanotube dispersion system (hereinafter also referred to as "carbon nanotube dispersion").

[0038] Furthermore, the mixing method includes ultrasonic dispersion. Regarding the preparation of the carbon nanotube dispersion, in addition to the ultrasonic dispersion method mentioned above, any one of the following methods can be used, such as oscillation, stirring, or ball milling, to uniformly mix carbon nanotubes and nitrogen-doped or non-nitrogen-doped pentabenzene system molecules in the dispersion medium to form the carbon nanotube dispersion system.

[0039] Furthermore, the ultrasonic dispersion time is 30 min to 4 h. The equipment used is an ultrasonic cell disruptor (model VCX500, operating frequency 20 kHz, total power 500 W), and the ultrasonic power parameters are set to 20% to 40%.

[0040] Furthermore, the centrifugation rate is 10000g to 100000g, and the centrifugation time is 20min to 1h.

[0041] The types of carbon nanotubes and organic solvents, as well as the ratio of dispersant to carbon nanotubes, are as previously stated and will not be repeated here.

[0042] In some implementation examples, the preparation method includes: cleaning the carbon nanotube dispersion system and redispersing the cleaned carbon nanotube dispersion system in a target polar organic solution.

[0043] In some more specific implementations, the preparation method may include: removing the organic solvent from the carbon nanotube dispersion system, and then redispersing it in a polar organic solvent to form a carbon nanotube polar organic solution.

[0044] In some more specific implementation examples, one cleaning method includes: removing the solvent from the carbon nanotube dispersion system using vacuum filtration, then cleaning the carbon nanotubes with a cleaning agent to remove nitrogen-doped or non-nitrogen-doped pentane system molecules, and finally ultrasonically dispersing the obtained carbon nanotubes in a polar organic solvent to form a carbon nanotube polar organic solution. Since nitrogen-doped or non-nitrogen-doped pentane system molecules can be decomposed by ultraviolet light, the cleaning process of the carbon nanotube dispersion system can be simplified, thereby greatly reducing the loss of carbon nanotubes during the process.

[0045] Furthermore, the cleaning agent includes, but is not limited to, tetrahydrofuran. And the cleaning temperature is 40–45°C.

[0046] Furthermore, the ultrasonic dispersion time is 4–6 minutes, and the ultrasonic power is set to 20–25%.

[0047] Furthermore, the polar organic solvent includes chloroform, and using chloroform will result in a larger array area and better stability and continuity.

[0048] In some more specific implementations, another cleaning method includes: adding a precipitant to the carbon nanotube dispersion system to cause the carbon nanotubes to flocculate, collecting the carbon nanotube precipitate after centrifugation, and ultrasonically dispersing the carbon nanotube precipitate in a polar organic solvent to form a carbon nanotube polar organic solution.

[0049] Specifically, in the step of cleaning the carbon nanotube dispersion system, a small amount of ethanol can be added to the solution to cause the carbon nanotubes to flocculate. After centrifugation, the carbon nanotube precipitate is collected and then ultrasonically dispersed in trichloroethane to achieve simple cleaning of the carbon nanotube dispersion system.

[0050] Furthermore, the precipitant includes, but is not limited to, ethanol, water, etc.

[0051] In some embodiments, the preparation method includes: vertically immersing a substrate in the carbon nanotube dispersion system or the carbon nanotube polar organic solution under a light-protected environment, adding a hydroxyl-rich solution, and slowly pulling the substrate out of the carbon nanotube dispersion system or the carbon nanotube polar organic solution after the liquid level stabilizes, thereby preparing a carbon nanotube orientation array. The addition of the hydroxyl-rich solution utilizes its immiscibility with the polar organic solution to form a two-dimensional confinement region near the silicon wafer, allowing the carbon nanotubes to self-assemble within this two-dimensional confinement region. The amount of water added is determined according to the size of the substrate, generally 5mm-10mm of pure water is added to the tank.

[0052] Furthermore, the hydroxyl-rich solution has a lower density than the polar organic solution and is completely immiscible with the polar organic solution. Specifically, it can be at least one of water, ethylene glycol, etc.

[0053] Furthermore, the lifting rate is 2–5 μm / s.

[0054] Furthermore, the substrate may include, but is not limited to, a silicon wafer.

[0055] In other embodiments, in the carbon nanotube orientation array preparation steps, besides the schemes described above, carbon nanotubes can be collected by filtration and redispersed in m-chlorotoluene. Ethylene glycol is first added to a square tank, then a silicon wafer is immersed in it. The m-chlorotoluene carbon nanotube dispersion is then added along the tank wall, and finally the silicon wafer is slowly pulled out of the solution, which can also form a carbon nanotube orientation array. Alternatively, a carbon nanotube orientation array can be prepared by the slow evaporation of a polar organic solution. Specifically, a silicon wafer is vertically inserted into a polar organic solution, a bell-shaped container is placed over the solution with small vent holes, and the solution is left to stand at 10°C for 1-2 days. After the solution slowly evaporates, a carbon nanotube orientation array can be formed on the silicon wafer.

[0056] In this invention, the post-processing of the carbon nanotube orientation array includes three consecutive processes: ultraviolet irradiation, solution immersion, and vacuum sublimation, in order to achieve complete removal of polymer molecules from the carbon nanotube surface.

[0057] In some embodiments, the irradiation time with ultraviolet light is 20 min to 1 h, and the wavelength of the ultraviolet light used is 200 to 450 nm, so that the nitrogen-doped or undoped pentabenzene molecules on the surface of the carbon nanotube oriented array film are fully decomposed.

[0058] In some embodiments, the solution soaking includes: placing the irradiated substrate with a carbon nanotube orientation array on its surface in toluene and soaking it for 1 to 2 hours.

[0059] In some embodiments, the vacuum sublimation is performed in a vacuum oven at a temperature of 120–200°C for a time of 30 min–1 h.

[0060] In some more specific embodiments, the preparation process of a high-purity carbon nanotube orientation array provided by the present invention includes the following steps:

[0061] First, carbon nanotubes are dispersed in an organic phase using nitrogen-doped or undoped pentane system molecules. Then, free polymers in the solution are removed by filtration and washing. The collected carbon nanotubes are then redispersed in a target polar organic phase solution. Subsequently, a carbon nanotube oriented array film is prepared. The carbon nanotube oriented array film is subjected to ultraviolet irradiation to achieve photodecomposition of nitrogen-doped or undoped pentane system molecules. The photodecomposed molecules are then removed by solution immersion and vacuum sublimation to finally obtain a highly clean carbon nanotube oriented array film.

[0062] Please see Figure 1 As shown, the preparation method of high-purity carbon nanotube oriented array assembly according to the present invention mainly includes the following steps:

[0063] (1) Preparation of carbon nanotube dispersion using nitrogen-doped or undoped pentane system molecules: Nitrogen-doped or undoped pentane system molecules and single-walled carbon nanotubes in a mass ratio of 4:1 to 5:1 are placed in an organic solvent such as toluene (xylene, chloroform, dichloromethane, cyclohexane, NMP, tetrahydrofuran, etc.), and sonicated at 20% to 40% ultrasonic power (depending on the volume of solution) for a specific time (30 min to 4 h). Then, the solution is placed in a centrifuge at a centrifuge rate of 10,000 g to 100,000 g for 20 min to 1 h, and the supernatant is collected.

[0064] (2) Simple cleaning and redispersion of carbon nanotube dispersion in a polar organic solvent: The prepared carbon nanotube dispersion was vacuum filtered to remove most of the solvent, and the filter membrane was rinsed at 40–45°C with a certain amount (depending on the solution volume and the desired cleaning effect) of tetrahydrofuran solution at a fixed ratio (1:20–1:25). Then the filter membrane was placed in 20 ml of trichloroethane solution and sonicated at 20–25% ultrasonic power for 4–6 min to redisperse the carbon nanotubes in the polar organic solvent.

[0065] (3) Preparation of carbon nanotube orientation array: Under light-proof environment, the silicon wafer is vertically immersed into a square tank containing a polar organic solution of carbon nanotubes. Then, a hydroxyl-rich solution with a height of 5 mm-10 mm is added to the square tank. After the liquid surface stabilizes, the silicon wafer is slowly pulled out of the square tank to realize the preparation of carbon nanotube orientation array.

[0066] (4) Preparation of high-purity carbon nanotube orientation array: The silicon wafer is irradiated with ultraviolet light (200-450nm) for 20min-1h to fully decompose the nitrogen doping and pentabenzene molecules on the surface of the film. Then, the silicon wafer is immersed in toluene solution for 1-2h to remove some of the fragment molecules after photodecomposition. Finally, it is stored in a vacuum oven at 120-200℃ for 30min-1h to remove all remaining fragment molecules by vacuum sublimation, and finally, a high-purity carbon nanotube orientation array film is obtained.

[0067] As another aspect of the technical solution of this invention, it also relates to a high-purity carbon nanotube orientation array prepared by the aforementioned method. The inventors used AFM to measure the height of the carbon nanotubes before and after ultraviolet irradiation and found that the height of the carbon nanotubes decreased significantly after irradiation. Raman spectroscopy of the high-purity carbon nanotube orientation array film after ultraviolet irradiation revealed the disappearance of the Raman resonance peaks of nitrogen-doped or undoped pentacene system molecules, indicating effective removal of the dispersant.

[0068] According to the above technical solution, the present invention uses nitrogen-doped or undoped pentaphenyl system molecules as dispersants, and can be decomposed by ultraviolet irradiation, so that they will not remain on the surface of the carbon nanotube orientation array film, thereby realizing the preparation of high-purity carbon nanotube orientation arrays.

[0069] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be noted that the following embodiments are intended to facilitate understanding of the present invention, and do not constitute any limitation thereof. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the manufacturer.

[0070] Example 1

[0071] (1) Nitrogen-doped pentabenzene system molecules (structure as shown below) with a mass ratio of 4:1 were placed in toluene and sonicated at 40% ultrasonic power for 30 min. Then, the mixture was placed in a centrifuge at a centrifuge rate of 50000g for 40 min and the supernatant was taken.

[0072]

[0073] Ar includes as R is an ethylbase.

[0074] (2) Simple washing and redispersion of carbon nanotube dispersion in polar organic solvent: The prepared carbon nanotube dispersion was vacuum filtered to remove most of the solvent, and the filter membrane was rinsed with a 1:20 tetrahydrofuran solution at 40°C. Then the filter membrane was placed in 20 ml of chloroform solution and sonicated at 20% ultrasonic power for 4 min to redisperse the carbon nanotubes in the polar organic solvent.

[0075] (3) Preparation of carbon nanotube orientation array: Under light-proof environment, the silicon wafer is vertically immersed into a square tank containing a polar organic solution of carbon nanotubes. Then, 8 mm of pure water is added to the square tank. After the liquid level stabilizes, the silicon wafer is pulled out of the square tank at a pulling speed of 2 μm / s to realize the preparation of carbon nanotube orientation array.

[0076] (4) Preparation of high-purity carbon nanotube orientation array: The silicon wafer was irradiated with ultraviolet light (200 nm) for 1 h to fully decompose the nitrogen-doped and pentabenzene molecules on the film surface. Then, the silicon wafer was immersed in toluene solution for 2 h to remove some of the photodecomposed fragment molecules. Finally, it was stored in a vacuum oven at 120 °C for 1 h, and all remaining fragment molecules were removed by vacuum sublimation to obtain a high-purity carbon nanotube orientation array film. Its SEM image is shown below. Figure 2 As shown in the figure. Raman spectroscopy revealed the disappearance of the Raman absorption peak of the nitrogen-doped pentacene system molecules, proving that the nitrogen-doped pentacene system molecules on the film surface were fully decomposed. Figure 3a An AFM (atomic force microscopy) image of an oriented array of highly clean carbon nanotubes is shown.

[0077] Example 2

[0078] (1) Nitrogen-doped pentabenzene system molecules (structure as shown below) with a mass ratio of 5:1 were placed in toluene and sonicated at 30% ultrasonic power for 4 hours. Then, the mixture was placed in a centrifuge at a centrifuge rate of 100,000g for 20 minutes and the supernatant was taken.

[0079]

[0080] Ar includes as R stands for cyclohexyl.

[0081] (2) Simple washing and redispersion of carbon nanotube dispersion in polar organic solvent: The prepared carbon nanotube dispersion was vacuum filtered to remove most of the solvent, and the filter membrane was rinsed with a 1:20 tetrahydrofuran solution at 45°C. Then the filter membrane was placed in 20 ml of chloroform solution and sonicated at 25% ultrasonic power for 5 min to redisperse the carbon nanotubes in the polar organic solvent.

[0082] (3) Preparation of carbon nanotube orientation array: Under light-proof environment, the silicon wafer is vertically immersed into a square tank containing a polar organic solution of carbon nanotubes. Then, 10 mm of pure water is added to the square tank. After the liquid level stabilizes, the silicon wafer is pulled out of the square tank at a pulling speed of 3 μm / s to realize the preparation of carbon nanotube orientation array.

[0083] (4) Preparation of high-purity carbon nanotube orientation array: The silicon wafer was irradiated under ultraviolet light (450nm) for 20min to fully decompose the nitrogen-doped pentaphenyl molecules on the film surface. Then, the silicon wafer was immersed in toluene solution for 1h to remove some of the photodecomposed fragment molecules. Finally, it was stored in a vacuum oven at 200℃ for 30min to remove all remaining fragment molecules by vacuum sublimation. Finally, a high-purity carbon nanotube orientation array film was obtained. After Raman testing, the Raman absorption peak of the nitrogen-doped pentaphenyl system molecules disappeared, proving that the nitrogen-doped pentaphenyl system molecules on the film surface were fully decomposed.

[0084] Example 3

[0085] (1) Nitrogen-doped pentabenzene system molecules (structure as shown below) with a mass ratio of 4.5:1 were placed in toluene and sonicated at 20% ultrasonic power for 2 hours. Then, the mixture was placed in a centrifuge at a centrifuge rate of 10000g for 1 hour and the supernatant was collected.

[0086]

[0087] Ar includes as R stands for methyl.

[0088] (2) Simple washing and redispersion of carbon nanotube dispersion in polar organic solvent: The prepared carbon nanotube dispersion was vacuum filtered to remove most of the solvent, and the filter membrane was rinsed with a 1:20 tetrahydrofuran solution at 42°C. Then the filter membrane was placed in 20 ml of chloroform solution and sonicated at 20% ultrasonic power for 6 min to redisperse the carbon nanotubes in the polar organic solvent.

[0089] (3) Preparation of carbon nanotube orientation array: Under light-proof environment, the silicon wafer is vertically immersed into a square tank containing a polar organic solution of carbon nanotubes. Then, 5 mm high ethylene glycol is added to the square tank. After the liquid level stabilizes, the silicon wafer is pulled out of the square tank at a pulling speed of 5 μm / s to realize the preparation of carbon nanotube orientation array.

[0090] (4) Preparation of high-purity carbon nanotube orientation array: The silicon wafer was irradiated under ultraviolet light (300nm) for 30min to fully decompose the nitrogen-doped pentaphenyl molecules on the film surface. Then, the silicon wafer was immersed in toluene solution for 1.5h to remove some of the photodecomposed fragment molecules. Finally, it was stored in a vacuum oven at 180℃ for 40min to remove all remaining fragment molecules by vacuum sublimation. Finally, a high-purity carbon nanotube orientation array film was obtained. After Raman testing, the Raman absorption peak of the nitrogen-doped pentaphenyl system molecules disappeared, proving that the nitrogen-doped pentaphenyl system molecules on the film surface were fully decomposed.

[0091] Example 4

[0092] (1) Nitrogen-doped pentabenzene system molecules (structure as shown below) with a mass ratio of 4:1 were placed in toluene and sonicated at 20% ultrasonic power for 2 hours. Then, the mixture was placed in a centrifuge at a centrifuge rate of 10000g for 1 hour and the supernatant was collected.

[0093]

[0094] Ar includes as R is a straight chain with 20 carbon atoms.

[0095] The remaining steps are the same as in Example 1.

[0096] Example 5

[0097] (1) The nitrogen-free pentacene system molecules (structure as shown below) with a mass ratio of 5:1 and multi-walled carbon nanotubes were placed in toluene and sonicated at 20% ultrasonic power for 2 hours. Then, the mixture was placed in a centrifuge at a centrifuge rate of 10000g for 1 hour and the supernatant was taken.

[0098]

[0099] In this case, Ar is R, which is a hydrogen atom.

[0100] The remaining steps are the same as in Example 1.

[0101] Comparative Example 1

[0102] (1) Preparation of carbon nanotube dispersion using other polymer dispersants: PCz was selected as the polymer dispersant in this comparative example. PCz and single-walled carbon nanotubes were placed in an organic solvent with a mass ratio of 1:1. After sonication for a specific time (1-2h) at 40%-50% ultrasonic power (depending on the solution volume), the mixture was placed in a centrifuge at a centrifuge rate of 10000g to 100000g for 20min to 1h, and the supernatant was collected.

[0103] (2) Simple cleaning and redispersion of carbon nanotube dispersion in a polar organic solvent: The prepared carbon nanotube dispersion was vacuum filtered to remove most of the solvent, and the filter membrane was rinsed multiple times at 40-45℃ with a certain amount (depending on the solution volume and the desired cleaning effect) of tetrahydrofuran solution at a fixed ratio (1:20-1:25). Then the filter membrane was placed in 20ml of chloroform solution and sonicated at 20-25% ultrasonic power for 4-6min to redisperse the carbon nanotubes in the polar organic solvent.

[0104] (3) Preparation of carbon nanotube orientation array: Under non-light-shielded environment, the silicon wafer is vertically immersed into a square tank containing a polar organic solution of carbon nanotubes, and then 5 mm of pure water is added to the square tank. After the liquid level stabilizes, the silicon wafer is slowly pulled out of the square tank to realize the preparation of carbon nanotube orientation array. Figure 3b An AFM image of the oriented carbon nanotube array is shown, revealing a significant amount of dispersant polymer residue.

[0105] Comparative Example 2

[0106] This comparative example differs from Example 1 in that it lacks the solution soaking step. The final result shows dispersant polymer residue on the surface of the carbon nanotube orientation array.

[0107] Comparative Example 3

[0108] This comparative example differs from Example 1 in that it lacks the vacuum sublimation step. The final result shows dispersant polymer residues on the surface of the carbon nanotube orientation array.

[0109] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0110] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a high-purity carbon nanotube orientation array, characterized in that, include: Carbon nanotubes and a dispersant are placed in an organic solvent and mixed evenly. The supernatant is then collected by centrifugation to obtain a carbon nanotube dispersion system. The mixing method is selected from at least one of ultrasonic dispersion, oscillation, stirring, and ball milling. The organic solvent in the carbon nanotube dispersion system is removed by vacuum filtration. Then, the carbon nanotubes are cleaned with a cleaning agent to remove the dispersant. Finally, the obtained carbon nanotubes are ultrasonically dispersed in a polar organic solvent to form a carbon nanotube polar organic solution. In a light-protected environment, the substrate is vertically immersed in a polar organic solution of carbon nanotubes, and a solution rich in hydroxyl groups is added. After the liquid surface stabilizes, the substrate is slowly pulled out of the polar organic solution of carbon nanotubes to form an oriented array of carbon nanotubes on the substrate surface. The pulling rate is 2~5 μm / s. The solution rich in hydroxyl groups is at least one of water and ethylene glycol. A high-purity carbon nanotube orientation array is prepared by irradiating a substrate with an oriented array of carbon nanotubes on its surface with ultraviolet light, followed by solution immersion and vacuum sublimation; the irradiation time is 20 min to 1 h, and the wavelength of the ultraviolet light used is 200 to 450 nm; the vacuum sublimation is carried out in a vacuum oven at a temperature of 120 to 200 °C for 30 min to 1 h. The dispersant has at least the structure shown in any one of formulas A, B, and D: ； Where Ar is R, , , , R is selected from at least one of the following groups: a hydrogen atom, a straight chain, a branched chain, or a cyclic alkyl chain having 1 to 20 carbon atoms.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the dispersant to carbon nanotubes is 4:1 to 5:

1.

3. The preparation method according to claim 1, characterized in that: The carbon nanotubes are single-walled carbon nanotubes.

4. The preparation method according to claim 1, characterized in that: The organic solvent is selected from any one or a combination of two or more of toluene, xylene, chloroform, dichloromethane, cyclohexane, N-methylpyrrolidone, and tetrahydrofuran.

5. The preparation method according to claim 1, characterized in that: The cleaning agent is tetrahydrofuran, and the cleaning temperature is 40~45℃.

6. The preparation method according to claim 1, characterized in that: The ultrasonic dispersion time is 4-6 minutes.

7. The preparation method according to claim 1, characterized in that: The polar organic solvent is chloroform.

8. The preparation method according to claim 1, characterized in that: The substrate is a silicon wafer.

9. The preparation method according to claim 1, characterized in that, The solution soaking includes: placing the irradiated substrate with a carbon nanotube orientation array on its surface in toluene and soaking it for 1-2 hours.

10. A high-purity carbon nanotube orientation array prepared by any one of claims 1-9.

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