Method for impurity-free short-cut dispersion of single-walled carbon nanotubes

Abstract

The invention relates to the field of carbon nanotube chopping and dispersion liquid preparation, in particular to a method for impurity-free chopping dispersion of a single-walled carbon nanotube. The method comprises the following steps: firstly, carrying out fluorination treatment on a macroscopic body of the single-walled carbon nanotube, wherein rich fluorocarbon bonds are formed on the surface of the single-walled carbon nanotube in the fluorination process; defluorinating the fluorinated single-walled carbon nanotube through heat treatment, and removing and consuming part of carbon atoms on the tube wall from bonded fluorine atoms on the surface of the single-walled carbon nanotube in the heat treatment process by utilizing the characteristic that fluocarbide is unstable at high temperature, so as to form a vacancy defect on the surface of the single-walled carbon nanotube; and further carrying out hydrogen peroxide treatment, and etching and short-cutting the single-walled carbon nanotubes by hydrogen peroxide by taking vacancy defects on the surfaces of the single-walled carbon nanotubes as etching sites. According to the preparation method, a surfactant is prevented from being introduced in the traditional carbon nanotube dispersion process, so that the single-walled carbon nanotube dispersion liquid and a subsequent single-walled carbon nanotube preparation material have fewer impurities, and the material performance is conveniently improved.

Description

Technical Field

[0001] This invention relates to the field of carbon nanotube shavings and dispersion preparation, specifically to a method for impurity-free shaving and dispersion of single-walled carbon nanotubes. This method achieves shaving of highly crystalline, long-length single-walled carbon nanotubes and establishes an impurity-free introduction and dispersion technology for macroscopic single-walled carbon nanotubes. Background Technology

[0002] Carbon nanotubes can be viewed as one-dimensional hollow tubular materials formed by rolling up graphene layers. Due to their excellent properties such as high electrical and thermal conductivity, high strength, and high chemical stability, they hold promise for applications in various fields including integrated circuits, flexible batteries, flexible displays, sensors or detectors, composite materials, and thermoelectric materials (Printed Carbon Nanotube Electronics and Sensor Systems. Adv. Mater. 28:4397-4414.). However, most carbon nanotube-based applications require their preparation as dispersions and assembly into macroscopic volumes. Based on the number of wall layers, carbon nanotubes can be classified into single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Currently, MWCNTs are mainly found in powder form, which allows for relatively easy dispersion in solvents. In contrast, SWCNTs have a larger aspect ratio and mostly exist as flocculent or intertwined sponge-like macroscopic bodies, making them difficult to directly disperse in solvents to form a uniform dispersion (Soluble ultra-shortsingle-walled carbon nanotubes. Journal of the American Chemical Society 2006, 128(32):10568-71.). For example, SWCNT sponge-like macroscopic bodies prepared by floating catalyst chemical vapor deposition (FCCVD) are still difficult to form a uniform dispersion even when mixed with alcohol solvents that are compatible with their surface. The most common method for preparing carbon nanotube dispersions is to use surfactants, such as sodium cholate and sodium dodecyl sulfate (Role and impact of surfactants in carbon nanotube dispersions and sorting. J Surfact Deterg. 2023, 26(5):607-622.). However, residual surfactants are usually difficult to remove, affecting the application performance of carbon nanotubes.

[0003] Besides using surfactants, the particle size of carbon nanotubes can be reduced by cleaving them, making them easier to disperse in solvents. Furthermore, in some applications, carbon nanotubes of specific lengths are required to achieve optimized performance (Influence of length on cytotoxicity of multi-walled carbon nanotubes against human acute monocytic leukemia cell line THP-1 in vitro and subcutaneous tissue of rats in vivo. Mol. BioSyst. 2005, 1:176-182.). Especially for macroscopic structures formed from highly crystalline SWCNTs, developing controllable cleavage techniques is crucial. In recent years, the most commonly used carbon nanotube cleavage method is chemical cleavage, typically using strong acids (such as high-concentration sulfuric acid and nitric acid) to oxidize the carbon nanotubes. However, strong oxidizing solutions can damage and consume the sidewalls of the carbon nanotubes, resulting in unsatisfactory cleavage quality. Moreover, the strong acid oxidation cleavage process is complex, and the subsequent cleaning process is time-consuming.

[0004] Patent CN107235482A discloses a method for preparing surface-clean, dispersant-free single-walled carbon nanotubes, using a nitrogen-containing heterocyclic aromatic small-molecule compound as a dispersant. Although subsequent photo-treatment degrades this compound, complete removal is difficult to guarantee, potentially affecting the performance of the carbon nanotubes. Patent CN104724692A discloses a method for uniformly dispersing single-walled carbon nanotubes, using strong acid oxidation and UV-assisted cleaning. This may introduce impurities, and residual acid or oxidant requires further cleaning, increasing process complexity. Patent CN116425148A discloses a method for preparing neatly arranged monodisperse carbon nanotubes, focusing primarily on the dispersion and arrangement of carbon nanotubes, without addressing the shaving and dispersion of macroscopic bodies composed of highly crystalline, high aspect ratio single-walled carbon nanotubes. Microfluidic high-pressure homogenization technology requires specialized equipment with operating pressures as high as 5000–60000 psi, resulting in high equipment and operating costs.

[0005] In summary, developing simple, efficient, and controllable SWCNT short-cutting and dispersion methods is of great significance for improving the performance of SWCNT macroscopic bodies and promoting their practical applications. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the impurity-free short-cut dispersion of single-walled carbon nanotubes (SWCNTs). This method requires only a simple fluorination-assisted defect fabrication and etching process to form a uniform dispersion of SWCNTs with ultra-high crystallinity and ultra-high aspect ratio without introducing impurities. Furthermore, the slit length of the SWCNTs is controllable without causing excessive wall loss. This solves the bottleneck problem of the difficulty in cleanly and non-destructively dispersing macroscopic carbon nanotubes composed of ultra-long, highly crystalline SWCNTs.

[0007] The technical solution of the present invention:

[0008] A method for impurity-free short-cut dispersed single-walled carbon nanotubes is characterized by first subjecting the macroscopic single-walled carbon nanotubes to fluorination treatment, during which abundant carbon-fluorine bonds are formed on the surface of the single-walled carbon nanotubes; then, the fluorinated single-walled carbon nanotubes are defluorinated by heat treatment. Taking advantage of the instability of fluorocarbons at high temperatures, the bonded fluorine atoms on the surface of the single-walled carbon nanotubes are removed during the heat treatment process, consuming some of the carbon atoms on the tube wall, thereby forming vacancy defects on the surface of the single-walled carbon nanotubes; further, the defluorinated single-walled carbon nanotubes are treated with hydrogen peroxide, which uses the vacancy defects on the surface of the single-walled carbon nanotubes as etching sites to etch and short-cut the single-walled carbon nanotubes.

[0009] The method for impurity-free short-cut dispersed single-walled carbon nanotubes described herein uses macroscopic single-walled carbon nanotubes prepared by a floating catalyst chemical vapor deposition method.

[0010] The method for impurity-free short-cut dispersion of single-walled carbon nanotubes describes a macroscopic body of single-walled carbon nanotubes composed of intertwined single-walled carbon nanotubes or single-walled carbon nanotube bundles.

[0011] The method for impurity-free short-cut dispersion of single-walled carbon nanotubes, wherein the length of the single-walled carbon nanotubes or single-walled carbon nanotube bundles is 30–150 micrometers, and the single-walled carbon nanotubes are characterized by Raman spectroscopy. G / I D The range is 5–250, and the diameter of the single-walled carbon nanotubes is 0.3–3 nm.

[0012] The method for impurity-free short-cut dispersion of single-walled carbon nanotubes involves creating defects in the single-walled carbon nanotubes by first fluorinating and then defluorinating them, and then using hydrogen peroxide to etch the short-cut carbon nanotubes at the defect sites, ultimately forming a uniform dispersion in a solvent.

[0013] The method for producing impurity-free short-cut dispersed single-walled carbon nanotubes includes a fluorination process as follows: the macroscopic single-walled carbon nanotubes and a fluorinating agent are sealed in a polytetrafluoroethylene container, and the fluorinating agent is hydrogen fluoride (HF), fluorine (F2), or xenon fluoride (XeF2); the sealed container is placed in an oven and heated to 50–200°C. This process forms abundant carbon-fluorine bonds on the surface of the single-walled carbon nanotubes, and the molar ratio of fluorine in the prepared fluorinated single-walled carbon nanotubes is 5%–30%.

[0014] The method for producing impurity-free short-cut dispersed single-walled carbon nanotubes includes a defluorination process as follows: fluorinated single-walled carbon nanotubes are removed from a sealed container and placed in a tube furnace; the temperature is raised to 300–700°C under an argon or nitrogen protective atmosphere. At this high temperature, fluorine atoms are removed and some carbon atoms are consumed, forming vacancy defects on the tube wall. The remaining fluorine molar ratio of the prepared defluorinated single-walled carbon nanotubes is 0–2%.

[0015] The method for impurity-free short-cut dispersion of single-walled carbon nanotubes involves placing defluorinated single-walled carbon nanotubes in a hydrogen peroxide solution with a volume concentration of 30% to 50% and stirring them. During the stirring process, hydrogen peroxide is selectively adsorbed onto defects on the tube wall and etched to shorten them.

[0016] In the method for dispersing single-walled carbon nanotubes with impurities by short cutting, the mass ratio of single-walled carbon nanotubes to hydrogen peroxide after defluorination is 1 / 3 to 3 / 1 during the etching and short cutting process.

[0017] The method for impurity-free short-cut dispersion of single-walled carbon nanotubes involves removing hydrogen peroxide solution from etched and short-cut single-walled carbon nanotubes or single-walled carbon nanotube bundles by centrifugation or vacuum filtration, and then washing and collecting them with water or ethanol. The length of the short-cut single-walled carbon nanotubes or single-walled carbon nanotube bundles is controllable within the range of 0.5 to 15 micrometers. The collected single-walled carbon nanotubes or single-walled carbon nanotube bundles are stirred in water, ethanol, isopropanol, or acetone to form a stable suspension.

[0018] The design concept of this invention:

[0019] Traditional methods (such as those using surfactants and strong acids) inevitably introduce impurities. This invention aims to prepare SWCNT dispersions by controllably shaving SWCNTs without introducing impurities. It employs a strategy of "first creating defects, then etching and shaving," achieving a completely impurity-free process through a three-step method of fluorination, defluorination, and hydrogen peroxide. The macroscopic material composed of highly crystalline, high aspect ratio SWCNTs is fluorinated, forming abundant carbon-fluorine bonds on the SWCNT surface. The fluorinated SWCNT material is then defluorinated through heat treatment. Taking advantage of the instability of fluorocarbons at high temperatures, the bonded F atoms on the tube wall surface are removed during heat treatment, consuming some carbon atoms and creating vacancy defects on the SWCNT surface. Finally, the defluorinated SWCNT material is treated with H2O2, which uses these vacancy defects on the tube wall as etching sites to etch and shave the SWCNTs. This invention creates vacancy defects on the surface of SWCNTs through fluorination-defluorination, and utilizes hydrogen peroxide to selectively adsorb onto the defect sites for directional etching, achieving controllable short-cutting. The fluorinating agent is completely decomposed during the defluorination process, and the hydrogen peroxide is removed by centrifugation or filtration after etching, resulting in a dispersion free of residual impurities.

[0020] The length of stubbed SWCNTs can be controlled within a certain range, and they can form stable and uniform suspensions in solvents such as water and ethanol. This method avoids the drawback of introducing surfactants in the traditional carbon nanotube dispersion process, resulting in fewer impurities in the SWCNT dispersion and subsequent SWCNT-based materials, which is beneficial for significantly improving material performance.

[0021] The advantages and beneficial effects of this invention are:

[0022] 1. The advantage of the method of the present invention is that no impurities are introduced throughout the process, the fluorinating agent used can be completely removed during the defluorination process, and the H2O2 used for etching the short cut can be decomposed into water by simply placing and heating.

[0023] 2. This invention avoids the introduction of surfactants and can form a uniform SWCNT suspension in solvents such as water, ethanol, acetone, isopropanol, and toluene.

[0024] 3. The present invention has the advantages of not significantly damaging the SWCNT structure and strong controllability. The SWCNT short-cut length is controllable in the range of 0.5 to 15 micrometers.

[0025] 4. The method of the present invention can be used to process macroscopic bodies formed by winding highly crystalline, high aspect ratio SWCNTs. The macroscopic bodies include various forms such as powder, flocculents, films, and sponges.

[0026] 5. The impurity-free short-cut dispersion SWCNT method proposed in this invention has a simple process and avoids the complex process required for traditional strong acid short-cutting. Attached Figure Description

[0027] Figure 1 A schematic diagram of the process for impurity-free short-cut dispersion of SWCNTs. In the diagram, 1. SWCNT, 2. Fluorinated SWCNT, 3. F atom, 4. Defluorinated SWCNT, 5. Defect vacancy, 6. H2O2 molecule, 7. SWCNT after etching and short-cutting.

[0028] Figure 2 Spectral characterization of the products during the preparation process. (a) X-ray photoelectron spectra (XPS) of pristine SWCNTs, fluorinated SWCNTs (F-SWCNTs), and defluorinated SWCNTs (DF-SWCNTs), with the vertical axis representing intensity (au) and the horizontal axis representing binding energy (eV). (b) Raman spectra of SWCNTs, F-SWCNTs, and DF-SWCNTs, with the vertical axis representing intensity (au) and the horizontal axis representing Raman shift (cm). -1 ).

[0029] Figure 3 Optical photographs of the actual objects. (a) Sponge-like macrostructure of SWCNT grown by FCCVD, (b) Optical photograph of SWCNT obtained after fluorination and defluorination and H2O2 treatment, (c) Optical photograph of SWCNT after direct H2O2 treatment and stirring, (d) Optical photograph of SWCNT after heat treatment in air at 500°C and then H2O2 treatment and stirring.

[0030] Figure 4 Scanning electron microscope (SEM) images of SWCNT samples after fluorination, defluorination, and H2O2 treatment and stirring. (a) Low magnification (the stubbed SWCNTs are circled in the image), (b) High magnification SEM image, (c) SEM image of SWCNTs after direct H2O2 treatment and stirring. Detailed Implementation

[0031] like Figure 1 The diagram shows the microscopic principle of the impurity-free short-cut dispersion SWCNT method proposed in this invention. The method consists of the following steps:

[0032] (1) Take the original macroscopic body of SWCNT1 and weigh it using an analytical balance.

[0033] (2) Select a polytetrafluoroethylene reactor of appropriate volume according to the mass and volume of the original SWCNT1. Weigh the fluorinating agent according to the set ratio of SWCNT to fluorinating agent, and place it together with the SWCNT in the reactor and seal it. Place the sealed reactor in a heating device and heat it to 50-200°C for fluorination treatment. F atoms 3 are bonded to the surface of the SWCNT1 tube wall to obtain fluorinated SWCNT2.

[0034] (3) After fluorination treatment, fluorinated SWCNT2 is taken out from the reactor. The fluorinated SWCNT2 is collected and placed in a tube furnace for defluorination heat treatment. It is heated to 300-700℃ and held for 0.5-3 hours. Ar or N2 gas is introduced for protection throughout the process. After defluorination heat treatment, defluorinated SWCNT4 with defect vacancy 5 on the SWCNT tube wall is obtained.

[0035] (4) Take the defluorinated SWCNT4 out of the tube furnace and put it into a beaker of appropriate volume according to its volume. Add an aqueous solution of H2O2 with a volume concentration of 30% and stir magnetically. The H2O2 molecules will etch and cut the defluorinated SWCNT4 at the defect. The mass ratio of defluorinated SWCNT4 to H2O2 in the solution is 1 / 3 to 3 / 1.

[0036] (5) The SWCNT7 after etching and short cutting is collected by vacuum filtration or centrifugation and dispersed in other target solvents.

[0037] The present invention will be further described in detail below through embodiments.

[0038] Example 1

[0039] In this embodiment, a method for dispersing impurity-free short-cut single-walled carbon nanotubes is as follows:

[0040] (1) Take as Figure 3 (a) The spongy macroscopic SWCNTs shown were weighed to a mass of 40 mg using an analytical balance; XPS analysis of the SWCNTs revealed that their surface contained only carbon (C) and a small amount of adsorbed oxygen (O). Figure 2 a) Raman spectroscopy was performed on SWCNTs, and its I G / I D 89.5 Figure 2 b).

[0041] (2) Weigh 160 mg of XeF2 powder and place it in a polytetrafluoroethylene reaction vessel. Then transfer 40 mg of SWCNT to the reaction vessel and seal it. Place the reaction vessel in a muffle furnace and heat it to 200 °C for fluorination treatment, and keep it at that temperature for 8 hours. Take out the treated reaction vessel and remove the fluorinated SWCNT inside. Perform XPS detection on the fluorinated SWCNT. Compared with the original SWCNT, a significant F peak position appears, and the calculated F atomic molar ratio is 17.3%. Figure 2 a).

[0042] (3) The fluorinated SWCNTs were collected and placed in a tube furnace for defluorination heat treatment. The furnace was heated to 600℃ at a heating rate of 10℃ / min and held for 1 hour, with Ar gas at a rate of 200 standard cubic centimeters per minute (sccm) purging throughout the process. The furnace was then allowed to cool freely to room temperature. The defluorinated SWCNTs were removed from the tube furnace and subjected to XPS analysis. The results showed that the F peak had disappeared and the surface F atomic molar ratio was below the detection limit of 0.1%. Raman spectroscopy was performed on the defluorinated SWCNTs, and their I... G / I D It dropped to 4.3 ( Figure 2 b) The dedoping of F atoms consumes some of the C atoms on the tube wall, forming abundant vacancy defects.

[0043] (4) Place the defluorinated SWCNTs into a beaker of appropriate volume, add a 30% (v / v) H2O2 aqueous solution, and etch and cut the SWCNTs by magnetic stirring; the mass ratio of SWCNTs to H2O2 in the solution is 1:2, and a uniformly dispersed suspension can be formed after cutting. Figure 3 b); The chopped SWCNTs can be collected by vacuum filtration or centrifugation and dispersed in other target solvents; a small amount of chopped SWCNTs is dropped onto a Si / SiO2 substrate, and the length of the chopped SWCNTs is observed using a scanning electron microscope, showing that the length is approximately 2-5 micrometers. Figure 4 ab).

[0044] Example 2

[0045] In this embodiment, a method for dispersing impurity-free short-cut single-walled carbon nanotubes is as follows:

[0046] (1) Step 1 is the same as Step 1 in Example 1, using the same batch of SWCNT macroscopic samples.

[0047] (2) Step 2 adopts the method and process of Step 2 in Example 1, using 80 mg of XeF2 and shortening the fluorination time to 4 hours. The surface F atom molar ratio of the fluorinated sample was 6.3% by XPS detection, indicating that the amount of fluorinating agent and the fluorination time can significantly affect the degree of fluorination of SWCNT.

[0048] (3) Step 3 uses the method and process of Step 3 in Example 1 to perform XPS detection on the defluorinated SWCNTs. The F peak disappears, and the surface F atomic molar ratio is below the detection limit of 0.1%. The defluorinated SWCNTs are then subjected to Raman detection, and their I... G / I D The concentration decreased to 21.4; compared with Example 1, this shows that the degree of fluorination on the surface can further affect the defect concentration on the SWCNT surface after defluorination.

[0049] (4) Step 4 is exactly the same as step 4 in Example 1, which can form a uniformly dispersed suspension. Scanning electron microscopy shows that the length of SWCNT is about 10 to 15 micrometers.

[0050] Example 3

[0051] In this embodiment, a method for dispersing impurity-free short-cut single-walled carbon nanotubes is as follows:

[0052] (1) Step 1 is the same as Step 1 in Example 1, using the SWCNT macroscopic sample manufactured by OCSiAL. G / I D It is 30.

[0053] (2) Step 2 adopts the method and process of Step 2 in Example 1, using 320 mg of XeF2 and 16 hours of fluorination time; XPS detection results show that the surface F atom molar ratio is 32.2%, indicating that the amount of fluorinating agent, the fluorination time and the type of original sample can significantly affect the degree of fluorination of SWCNT.

[0054] (3) Step 3 uses the method and process of Step 3 in Example 1 to perform XPS detection on the defluorinated SWCNTs. The F peak disappears, and the surface F atomic molar ratio is below the detection limit of 0.1%. The defluorinated SWCNTs are then subjected to Raman detection, and their I... G / I D It dropped to 0.5.

[0055] (4) Step 4 is exactly the same as step 4 in Example 1, and a uniformly dispersed suspension can be formed. Figure 3 b) The length of SWCNTs observed by scanning electron microscopy is approximately 0.5–2 micrometers. Compared with Example 1, although the short-cutting effect is improved, excessive fluorination leads to serious loss of SWCNT quality. Therefore, it is necessary to reasonably control the fluorination and short-cutting processes.

[0056] Comparative Example 1

[0057] In this comparative example, pure SWCNTs were directly placed in H2O2 for short-cutting without fluorination and defluorination treatment to study their short-cutting dispersion effect. The specific steps are as follows:

[0058] (1) Step 1 is exactly the same as Step 1 in Example 1.

[0059] (2) Step 2 is exactly the same as step 4 in Example 1. The SWCNTs treated with H2O2 still exhibit an aggregated state in the solution, making it difficult to achieve a uniform suspension. Figure 3 c); Scanning electron microscopy was used to observe the length of SWCNTs. Figure 4 c), it can be seen that they still remain entangled and agglomerated, and it is impossible to obtain a uniformly dispersed suspension.

[0060] Comparing with Example 1, it is shown that the defective manufacturing process of fluorination and defluorination is crucial for the short cutting of highly crystalline SWCNTs.

[0061] Comparative Example 2

[0062] Oxidation in air can also create defects to some extent on the SWCNT tube wall. In this comparative example, pure SWCNTs were first oxidized in air at 500°C for 1 hour, and then chopped in H2O2 to study their chopping and dispersion effect. The specific steps are as follows:

[0063] (1) Step 1 is exactly the same as Step 1 in Example 1.

[0064] (2) Place SWCNT in a tube furnace and heat it to 500°C for oxidation treatment. The heating rate is 10°C / min. Keep both ends of the furnace open to ensure air circulation. After holding the temperature for 1 hour, allow it to cool to room temperature.

[0065] (3) Step 3 is exactly the same as step 4 in Example 1. The SWCNTs treated with H2O2 still exhibit an aggregated state in the solution, making it difficult to obtain a uniform suspension. Figure 3 d).

[0066] As can be seen from Examples 1-3 and Comparative Examples 1-2, after fluorination-defluorination treatment in Examples 1-3, vacancy defects are formed on the surface of SWCNTs. Hydrogen peroxide can selectively etch these defect sites, ultimately forming a stable and uniform suspension in solvents such as water and ethanol. The dispersion shows no obvious agglomeration and remains stable. In contrast, Comparative Example 1 did not undergo fluorination-defluorination treatment; the original SWCNTs were directly treated with hydrogen peroxide. Because there are no defect sites on the surface, hydrogen peroxide cannot effectively etch them, and the SWCNTs remain in an agglomerated state. Scanning electron microscopy shows that they are still entangled and cannot form a uniform dispersion. Therefore, the defect manufacturing process of fluorination-defluorination achieves uniform dispersion of highly crystalline SWCNTs, solving the bottleneck of SWCNT dispersion in traditional methods. In addition, by adjusting the amount of fluorinating agent, fluorination time, and defluorination temperature, the short-cut length of SWCNTs can be precisely controlled in Examples 1-3. Comparative Example 2 uses oxidation in air at 500°C to create defects, followed by treatment with hydrogen peroxide. Due to the non-selectivity of the oxidation process, the SWCNT tube wall is severely damaged, and the dispersion effect is poor, making it impossible to achieve controllable length.

[0067] The results of the examples and comparative examples demonstrate that this invention proposes a novel method for impurity-free short-cut dispersion of SWCNTs, achieving controllable short-cutting of highly crystallinity, high aspect ratio SWCNTs, and dispersing them in different solvents without introducing impurities. This invention requires only three steps—fluorination, defluorination, and etching—to precisely control the short-cut length within the range of 0.5–15 micrometers, avoiding excessive damage to the tube walls caused by strong acid oxidation or high-temperature oxidation. This method avoids the surfactants introduced in traditional carbon nanotube dispersion processes, resulting in less impurities in the single-walled carbon nanotube dispersion and subsequent single-walled carbon nanotube materials, thus facilitating improved material properties.

[0068] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for dispersing impurity-free short-cut single-walled carbon nanotubes, characterized in that, First, the macroscopic single-walled carbon nanotubes are fluorinated, which forms abundant carbon-fluorine bonds on the surface of the single-walled carbon nanotubes. Then, the fluorinated single-walled carbon nanotubes are defluorinated by heat treatment. Taking advantage of the instability of fluorocarbons at high temperatures, the bonded fluorine atoms on the surface of the single-walled carbon nanotubes are removed during the heat treatment process, consuming some of the carbon atoms on the tube wall, thus forming vacancy defects on the surface of the single-walled carbon nanotubes. The defluorinated single-walled carbon nanotubes are then further treated with hydrogen peroxide. The hydrogen peroxide uses the vacancy defects on the surface of the single-walled carbon nanotubes as etching sites to etch and shorten the single-walled carbon nanotubes.

2. The method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1, characterized in that, The macroscopic single-walled carbon nanotubes used were prepared by floating catalyst chemical vapor deposition.

3. The method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1, characterized in that, Macroscopic volumes of single-walled carbon nanotubes are composed of intertwined single-walled carbon nanotubes or bundles of single-walled carbon nanotubes.

4. The method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 3, characterized in that, The length of single-walled carbon nanotubes or bundles of single-walled carbon nanotubes is 30–150 micrometers. The Ig of single-walled carbon nanotubes is characterized by Raman spectroscopy. G / I D The range is 5–250, and the diameter of the single-walled carbon nanotubes is 0.3–3 nm.

5. The method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1, characterized in that, Defects were created in single-walled carbon nanotubes by first fluorinating and then defluorinating them. Hydrogen peroxide was then used to etch short carbon nanotubes at the defect sites, ultimately forming a uniform dispersion in a solvent.

6. A method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1 or 5, characterized in that, The fluorination process is as follows: the macroscopic single-walled carbon nanotubes and the fluorinating agent are sealed in a polytetrafluoroethylene container. The fluorinating agent is hydrogen fluoride (HF), fluorine (F2), or xenon fluoride (XeF2). The sealed container is placed in an oven and heated to 50-200°C. This process will form abundant carbon-fluorine bonds on the surface of the single-walled carbon nanotubes. The molar ratio of fluorine in the prepared fluorinated single-walled carbon nanotubes is 5%-30%.

7. A method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1 or 5, characterized in that, The defluorination process is as follows: fluorinated single-walled carbon nanotubes are taken out of the sealed container and placed in a tube furnace; the temperature is raised to 300-700℃ under the protective atmosphere of argon or nitrogen. At high temperature, fluorine atoms are removed and some carbon atoms are consumed, forming vacancy defects on the tube wall. The molar ratio of residual fluorine in the prepared defluorinated single-walled carbon nanotubes is 0-2%.

8. A method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1 or 5, characterized in that, The defluorinated single-walled carbon nanotubes were placed in a hydrogen peroxide solution with a volume concentration of 30% to 50% and stirred. During the stirring process, hydrogen peroxide was selectively adsorbed onto the defects on the tube wall and etched and cut.

9. A method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 8, characterized in that, During the etching and short-cutting process, the mass ratio of defluorinated single-walled carbon nanotubes to hydrogen peroxide is 1 / 3 to 3 / 1.

10. A method for dispersing impurity-free short-cut single-walled carbon nanotubes according to claim 1 or 5, characterized in that, The etched and truncated single-walled carbon nanotubes or single-walled carbon nanotube bundles are dehydrogenated by centrifugation or vacuum filtration to remove hydrogen peroxide solution, and then washed and collected with water or ethanol. The length of the truncated single-walled carbon nanotubes or single-walled carbon nanotube bundles is controllable in the range of 0.5 to 15 micrometers. The truncated and collected single-walled carbon nanotubes or single-walled carbon nanotube bundles are stirred to form a stable suspension in water, ethanol, isopropanol or acetone.

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