Method for separating single chiral carbon nanotube mirror bodies

Abstract

The present application provides a method for separating single chiral carbon nanotube mirror bodies, comprising the following steps: (1) dispersing carbon nanotube raw materials into a solution of a composite surfactant to obtain a carbon nanotube dispersion liquid; (2) using gel chromatography for stepwise elution to separate the carbon nanotube dispersion liquid, and collecting the separation product to obtain single chiral carbon nanotube mirror bodies; wherein the solution of the composite surfactant comprises cholic acid, a first surfactant and an optional second surfactant, and a solvent; the first surfactant is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate and sodium n-hexadecyl sulfate; the second surfactant is selected from one or more of sodium cholate, sodium hydrate cholate, sodium dehydrocholate, sodium deoxycholate, sodium lithocholate, sodium hyodeoxycholate and sodium chenodeoxycholate. The method of the present application can separate and prepare single chiral carbon nanotube mirror bodies with a diameter of less than 0.69 nanometers.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of preparation and separation of nanomaterials. Specifically, the present application relates to a method for macro-scale separation of small-diameter single-chirality carbon nanotube mirror bodies from mixed-structure carbon nanotubes. BACKGROUND

[0002] For the past 30 years, structure control of carbon nanotubes has been a hot and difficult topic in the field of nanotechnology research. Carbon nanotubes can be divided into three levels in terms of structure and properties: (1) metallic / semiconducting carbon nanotubes; (2) single-chirality carbon nanotubes; (3) single-chirality carbon nanotube mirror bodies. As the classification becomes more refined, the structural and property differences between carbon nanotubes become smaller, and the difficulty of structural control increases. Single-chirality carbon nanotube mirror bodies are truly single-structure carbon nanotubes. Their macro-scale preparation is of great significance for fully revealing their intrinsic properties and promoting their applications. Currently, there are two main approaches to structural control of carbon nanotubes: one is to directly control the structure of carbon nanotubes through growth; the other is to first synthesize a mixture of carbon nanotubes containing different structures, and then separate the desired structure of carbon nanotubes through separation technology. Directly achieving precise control of carbon nanotube structure through growth is the most ideal approach, which can simply, efficiently and cost-effectively prepare the desired carbon nanotubes. However, there is currently no report on the growth preparation of single-chirality carbon nanotube mirror bodies. Compared with the direct growth method, separation technology has the advantage of easier control of carbon nanotube structure. In recent years, breakthrough progress has been made in the study of separation technology for separating carbon nanotube structures. Density gradient centrifugation, ion exchange chromatography, two-phase separation, polymer separation and gel chromatography separation technologies have been reported. These separation technologies show strong carbon nanotube structure resolution ability and can separate a variety of near-single-chirality semiconducting carbon nanotube mirror bodies. Among them, gel chromatography has the characteristics of simple operation, high efficiency and low cost, and is easy to realize large-scale separation. This makes it have great advantages in expanding scale and reducing cost under the premise of ensuring separation quality compared with other separation methods.

[0003] At present, various separation means based on gel chromatography have been able to separate a variety of single chiral carbon nanotube mirror bodies, but the separation yield and purity still need to be further improved, especially for the separation of single chiral mirror bodies of small-diameter carbon nanotubes which account for a small proportion in the raw materials. The fluorescence quantum efficiency of carbon nanotubes increases with the decrease of diameter, so small-diameter single chiral carbon nanotube mirror bodies have stronger application prospects in optoelectronic devices, biological molecule fluorescent probes and the like. At present, the smallest diameter single chiral carbon nanotube mirror body that can be separated and prepared is (6, 4) carbon nanotube, and the diameter is 0.692 nm. There is no report on the separation of carbon nanotube mirror bodies with smaller diameters. On the one hand, these small-diameter carbon nanotubes are difficult to nucleate due to large curling energy, and the yield is low, so the content in the raw materials is relatively small. On the other hand, the current separation system has low resolution for the structure of carbon nanotubes.

[0004] In order to break through the separation of smaller diameter carbon nanotube mirror bodies, it is urgent to develop a higher precision separation system to separate and prepare smaller diameter single chiral carbon nanotube mirror bodies, and to promote the research on the properties and application of carbon nanotubes. SUMMARY

[0005] The purpose of the present application is to provide a method for separating single chiral carbon nanotube mirror bodies. The method of the present application uses a new surfactant separation system, breaks through the existing diameter limit of single chiral carbon nanotube mirror bodies, and can separate and prepare single chiral carbon nanotube mirror bodies with a diameter of less than 0.69 nm, such as (5, 4) carbon nanotube mirror bodies.

[0006] The above purpose of the present application is achieved by the following technical solutions.

[0007] The present application provides a method for separating single chiral carbon nanotube mirror bodies, which comprises the following steps:

[0008] (1) dispersing carbon nanotube raw materials into a solution of a composite surfactant to obtain a carbon nanotube dispersion;

[0009] (2) using gel chromatography for step-by-step elution to separate the carbon nanotube dispersion, and collecting the separation product to obtain single chiral carbon nanotube mirror bodies;

[0010] Wherein, the solution of the composite surfactant comprises cholic acid, a first surfactant and an optional second surfactant, and a solvent;

[0011] The first surfactant is selected from one or more of octyl sodium sulfate, decyl sodium sulfate, dodecyl sodium sulfate and n-hexadecyl sodium sulfate;

[0012] The second surfactant is selected from one or more of sodium cholate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, sodium lithocholate, sodium hyodeoxycholate, and sodium chenodeoxycholate.

[0013] The inventors of the present application have surprisingly found that the addition of cholic acid in a surfactant system such as a binary surfactant system of sodium dodecyl sulfate and sodium cholate can enhance the selective adsorption of small diameter carbon nanotubes such as (5,4) carbon nanotubes in a gel, and achieve the selective enrichment of small diameter carbon nanotubes such as (5,4) carbon nanotubes in a gel. Then, the stepwise desorption of the dispersion of carbon nanotubes using an eluent such as a solution of sodium dodecyl sulfate, sodium cholate, and sodium deoxycholate can achieve the separation of small diameter carbon nanotube isomers such as (5,4) carbon nanotube isomers. The present technology breaks the diameter limitation of the existing single-chirality carbon nanotube isomer separation, and achieves the separation of single-chirality carbon nanotube isomers with a diameter less than 0.69 nanometers, which is conducive to promoting the application of carbon nanotubes in optoelectronics, biomolecular probes, and imaging.

[0014] Preferably, in the carbon nanotube dispersion of the present application, the concentrations of cholic acid, carbon nanotubes, the first surfactant, and the second surfactant are respectively: cholic acid 0.001-0.1 wt%, carbon nanotubes 0.001-4 mg / ml, the first surfactant 0.001-2 wt%, and the second surfactant 0.001-2 wt%, with the balance being a solvent.

[0015] Preferably, in the method of the present application, the complex surfactant comprises cholic acid, sodium dodecyl sulfate, and sodium cholate.

[0016] Preferably, in the method of the present application, the eluent used in the stepwise elution is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium n-hexadecyl sulfate, sodium cholate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, sodium lithocholate, sodium hyodeoxycholate, and sodium chenodeoxycholate.

[0017] Preferably, in the method of the present application, the eluent used in the stepwise elution comprises sodium dodecyl sulfate, sodium cholate, and sodium deoxycholate.

[0018] Preferably, in the method of the present application, the carbon nanotube raw material is synthesized by a chemical vapor deposition method, an arc discharge method, or a laser ablation method.

[0019] Preferably, in the method of the present application, the carbon nanotube raw material is metallic carbon nanotubes or semiconductor carbon nanotubes after separation and purification.

[0020] Preferably, in the method of the present application, the carbon nanotube raw material is single-walled carbon nanotubes with a tube diameter ranging from 0.6 to 3.0 nanometers.

[0021] In specific embodiments of the present application, the carbon nanotubes can be carbon nanotubes synthesized by different methods, such as chemical vapor deposition, arc discharge, laser ablation, etc.; can be non-functionalized carbon nanotubes, or can be functionalized carbon nanotubes, can be metallic carbon nanotubes or semiconductor carbon nanotubes after separation and purification, etc.

[0022] Preferably, in the method of the present application, the dispersing of the carbon nanotube raw material into the solution of the composite surfactant in step (1) is carried out by water bath ultrasonic, cell disrupter ultrasonic, mechanical stirring or strong acid treatment. After dispersion, centrifugal purification can be performed or not.

[0023] Preferably, in the method of the present application, the solvent is an inorganic solvent and / or an organic solvent.

[0024] Preferably, in the method of the present application, the solvent is water.

[0025] Preferably, in the method of the present application, the gel filler used in the gel chromatography is agarose series Separose (e.g. produced by American Amersham), dextran-polyacrylamide series Sephacryl S (e.g. produced by Cytiva), dextran series SephadexTM (e.g. produced by American GRACE ALLTECH), or agarose-dextran series SurperdexTM.

[0026] Preferably, in the method of the present application, the matrix of the gel filler is dextran-polyacrylamide Sephacryl series gel produced by GE Healthcare.

[0027] In specific embodiments of the present application, the method of the present application can comprise the following steps:

[0028] (1) dispersing a carbon nanotube raw material into an aqueous surfactant solution to prepare a monodisperse carbon nanotube solution;

[0029] (2) adding cholic acid to the carbon nanotube dispersion obtained in step (1) to modulate the composite surfactant system and enhance the difference in the density of the surfactant wrapped around the surface of different carbon nanotubes;

[0030] (3) loading the carbon nanotube dispersion obtained in step (2) into a gel column to achieve selective adsorption of small-diameter carbon nanotubes in the gel column;

[0031] (4) using eluent to selectively stepwise elute the carbon nanotubes adsorbed in the gel, and separate single chiral carbon nanotube mirror bodies.

[0032] The present application combines cholic acid with traditional surfactants to establish a new composite surfactant system, uses the strong hydrophobicity of cholic acid to regulate the density difference of surfactants wrapped on the surface of small-diameter semiconductor carbon nanotubes and other carbon nanotubes, enhances the selective adsorption of small-diameter carbon nanotubes in the gel column, and further uses eluent such as ternary composite surfactant to selectively stepwise elute the mirror bodies, so that the separation of small-diameter carbon nanotube mirror bodies is realized.

[0033] Compared with the prior art, the method of the present application has the following advantages:

[0034] Through the regulation of the gel chromatography-compatible cholic acid surfactant, the selective adsorption of small-diameter carbon nanotubes with a small content in raw materials in the gel is realized, and the separation of small-diameter carbon nanotube (5, 4) single chiral mirror bodies is prepared by selective elution. The bottleneck that the traditional separation technology is difficult to separate the carbon nanotube mirror bodies with a diameter less than 0.69 nm is broken. The method of the present application is simple, efficient, and has strong industrialization prospect. The method of the present application can promote the application of carbon nanotubes in high-performance optoelectronic devices, biological molecule probes, and biological imaging. BRIEF DESCRIPTION OF DRAWINGS

[0035] Hereinafter, the embodiments of the present application will be described in detail with reference to the accompanying drawings, in which:

[0036] Figure 1 A schematic diagram for cholic acid regulating the selective adsorption of carbon nanotubes in the gel and the selective desorption and separation of (5, 4) carbon nanotube mirror bodies by eluent.

[0037] Figure 2A is the absorption spectrum of the original CoMoCAT (SG65i) carbon nanotubes according to Example 1 of the present application and the light absorption spectrum of the carbon nanotubes selectively adsorbed under different concentrations of cholic acid.

[0038] Figure 2B is the absorption spectrum of the selectively enriched (5, 4) carbon nanotubes according to Example 1 of the present application and the light absorption spectrum of the carbon nanotubes eluted under different concentrations of sodium deoxycholate.

[0039] Figure 2C is the circular dichroism spectrum of the single chiral (4, 5) carbon nanotube mirror body and the (5, 4) carbon nanotube mirror body separated and obtained.

[0040] Figure 3A is the absorption spectrum of the original CoMoCAT (SG76) carbon nanotubes according to Example 2 of the present application and the light absorption spectrum of the carbon nanotubes selectively adsorbed under different concentrations of cholic acid.

[0041] Figure 3B Absorption spectra of selectively enriched (5,4) carbon nanotubes according to embodiment 2 of the present application and optical absorption spectra of eluted carbon nanotubes at different sodium deoxycholate concentrations.

[0042] Figure 3C Circular dichroism spectra of isolated single chiral (4,5) carbon nanotube and (5,4) carbon nanotube mirror bodies.

[0043] Figure 4 Absorption spectra of original CoMoCAT (SG65i) carbon nanotubes according to comparative example 1 of the present application and optical absorption spectra of eluted carbon nanotubes at different sodium deoxycholate concentrations. DETAILED DESCRIPTION

[0044] The present application will be further described in conjunction with the specific embodiments, and the examples given are only to illustrate the present application, but not to limit the scope of the present application.

[0045] The carbon nanotube solution is characterized by the following methods:

[0046] 1. Absorption spectrum characterization

[0047] The chiral structure distribution of carbon nanotubes can be characterized by ultraviolet-visible-near infrared absorption spectrum. Different structures and different chiral carbon nanotubes have specific and discrete absorption peaks in a certain wavelength range. The peak position of each absorption peak in the absorption spectrum can accurately determine the type of carbon nanotubes in the measured sample, and the relative value of the peak area of each absorption peak can be used to calculate the purity of the carbon nanotubes.

[0048] 2. Circular dichroism spectrum test

[0049] Circular dichroism spectrum is a common means to determine the configuration and conformation of asymmetric structure molecules. For chiral carbon nanotubes, carbon nanotubes with the same chiral index may also have different helical structures, and their properties are extremely similar, which also leads to more difficult separation of carbon nanotubes with different helical structures. Although the optical absorption spectrum can accurately identify the carbon nanotubes according to the chiral index, it cannot distinguish the helical structure. The absorption coefficients of chiral carbon nanotubes with helical structure for left and right circularly polarized light are different, which is reflected in the circular dichroism spectrum as a series of positive or negative absorption peaks. The helical chirality of carbon nanotubes can be identified by the peak position and intensity of specific peaks.

[0050] Example 1

[0051] 1) 20 mg of CoMoCAT(SG65i) carbon nanotubes and 0.2 g of sodium cholate powder were weighed and added to 20 mL of water. The solution was ultrasonically dispersed at a temperature of 15°C for 40 minutes using a cell disruptor at a power of 30 W / mL.

[0052] The CoMoCAT(SG65i) carbon nanotube raw material was a single-walled carbon nanotube synthesized by a CoMoCAT catalytic chemical vapor deposition method and commercially available from Sigma-Aldrich, USA. Through control of the condition parameters during the synthesis process, the average diameter of the CoMoCAT(SG65i) was about 0.78 nm.

[0053] 2) The metal catalyst particles, carbon nanotube bundles and amorphous carbon impurities in the dispersion liquid of step 1) were removed by centrifugal purification, the centrifugal force was set to 210,000 x g, the centrifugal time was 40 minutes, and 80% of the supernatant was taken.

[0054] 3) Sodium dodecyl sulfate and cholic acid were introduced into the supernatant obtained in step 2), and the surfactant in the carbon nanotube dispersion liquid was adjusted to a composite surfactant of sodium dodecyl sulfate, sodium cholate and cholic acid by adding pure water. After comparing the chiral distribution of the adsorbed carbon nanotubes at different cholic acid concentrations Figure 2A ), it was found that the degree of (5, 4) enrichment was the highest when the cholic acid concentration was 0.035wt%. Therefore, the concentrations of cholic acid, carbon nanotubes, sodium dodecyl sulfate, sodium cholate in the composite surfactant were set as follows: cholic acid 0.035wt%, carbon nanotubes 0.2mg / ml, sodium dodecyl sulfate 0.5wt%, sodium cholate concentration 0.5wt%.

[0055] 4) A 10 mL medical gravity column cylinder was filled with 5 mL Sephacryl S-200HR gel, 5 mL of the carbon nanotube dispersion liquid in step 3) was loaded into the prepared gel column, and then sodium dodecyl sulfate (0.5wt%) + sodium cholate (0.5wt%) + deoxycholic acid sodium (X wt%) were used to stepwise elute the carbon nanotubes adsorbed in the gel column, and the eluted carbon nanotube solution was collected below the chromatographic column. The concentration of deoxycholic acid sodium (X wt%) was gradually increased, and X = 0.015wt%, 0.020wt%, 0.025wt%, 0.028wt%, 0.029wt%, 0.031wt%, 0.033wt%, 0.035wt%, 0.038wt%, 0.040wt%, 0.045wt%, 0.050wt%.

[0056] The original carbon nanotube dispersion liquid, the carbon nanotubes adsorbed in the gel at different cholic acid concentrations, and the carbon nanotube solutions eluted stepwise were characterized by absorption spectroscopy, and the results are shown in Figures 2A-2C .Figure 2A The black spectrum in the upper graph represents the absorption spectrum of the original CoMoCAT (SG65i) carbon nanotubes, and the spectra in the lower graph represent the absorption spectra of the carbon nanotubes selectively adsorbed in the gel at different concentrations of cholic acid, in order. Figure 2B The black spectrum in the upper graph represents the absorption spectrum of the selectively enriched (5,4) carbon nanotubes, and the spectra in the lower graph represent the absorption spectra of the carbon nanotubes eluted step by step from the enriched (5,4) carbon nanotubes, in order. Figure 2C The circular dichroism spectra of the single-handed (4,5) carbon nanotube mirror and the (5,4) carbon nanotube mirror obtained by separation are shown. It is clear that high-purity single-handed (5,4) carbon nanotube mirrors can be separated from CoMoCAT (SG65i) carbon nanotubes using the method of the present application.

[0057] Example 2

[0058] 1) 20 mg of CoMoCAT (SG76) carbon nanotubes and 0.2 g of sodium cholate powder were weighed and added to 20 mL of water. The above solution was ultrasonically dispersed at a temperature of 15°C for 40 minutes using a cell disruptor at a power of 30 W / mL.

[0059] CoMoCAT (SG76) is a single-walled carbon nanotube commercially available from Sigma-Aldrich Company, USA, synthesized by CoMoCAT catalytic chemical vapor deposition method, and has an average diameter of about 0.84 nm.

[0060] 2) The dispersion liquid of step 1) was centrifuged to remove metal catalyst particles, carbon nanotube bundles, and amorphous carbon impurities, and the centrifugal force was set to 210,000 x g for 40 minutes, and 80% of the supernatant was taken.

[0061] 3) Sodium dodecyl sulfate and cholic acid were introduced into the supernatant obtained in step 2), and the surfactant in the carbon nanotube dispersion liquid was adjusted to a composite surfactant of sodium dodecyl sulfate, sodium cholate, and cholic acid by adding pure water. After comparing the chiral distribution of the adsorbed carbon nanotubes at different concentrations of cholic acid, Figure 3A ) it was found that the (5,4) enrichment was the highest when the concentration of cholic acid was 0.035 wt%. Therefore, the concentrations of cholic acid, carbon nanotubes, sodium dodecyl sulfate, and sodium cholate in the composite surfactant were set to be: cholic acid 0.035 wt%, carbon nanotubes 0.2 mg / ml, sodium dodecyl sulfate 0.5 wt%, and sodium cholate 0.5 wt%.

[0062] 4) A 10 mL medical gravity column was packed with 5 mL of Sephacryl S-200HR gel. 5 mL of the carbon nanotube dispersion from step 3) was added to the prepared gel column. Then, the carbon nanotubes adsorbed in the gel column were eluted stepwise using a solution of sodium dodecyl sulfate (0.5 wt%), sodium cholate (0.5 wt%), and sodium deoxycholate (X wt%). The eluted carbon nanotube solution was collected at the bottom of the column. The concentration of sodium deoxycholate (X wt%) gradually increased to 0.02 wt%, 0.025 wt%, 0.028 wt%, 0.029 wt%, 0.031 wt%, 0.033 wt%, 0.035 wt%, 0.038 wt%, 0.040 wt%, 0.045 wt%, and 0.050 wt%.

[0063] Absorption spectroscopy was used to characterize the original carbon nanotube dispersion, carbon nanotubes adsorbed in gels at different cholic acid concentrations, and carbon nanotube solutions eluted stepwise. The results are as follows: Figures 3A-3C As shown. Figure 3A In the upper figure, the black spectral lines represent the absorption spectrum of the original CoMoCAT (SG76) carbon nanotubes, while the spectral lines in the lower figure represent the absorption spectra of carbon nanotubes selectively adsorbed in the gel at different bile acid concentrations. Figure 3B In the upper figure, the black spectral lines represent the absorption spectra of selectively enriched (5,4) carbon nanotubes, while the spectral lines in the lower figure represent the absorption spectra of carbon nanotubes eluted stepwise from enriched (5,4) carbon nanotubes. Figure 3C The circular dichroism spectra represent the isolated single-chiral (4,5) carbon nanotube mirror images and (5,4) carbon nanotube mirror images. Clearly, the method of this invention can separate high-purity single-chiral (5,4) carbon nanotube mirror images from CoMoCAT (SG76) carbon nanotubes.

[0064] Comparative Example 1

[0065] This comparative example uses a similar procedure to Example 1, except that the entire process does not contain bile acids, and specifically includes the following steps:

[0066] 1) Weigh 20 mg of CoMoCAT (SG65i) carbon nanotubes and 0.2 g of sodium cholate powder, and add them together to 20 mL of water. Use a cell disruptor to sonicate the solution at 15 °C for 40 minutes at a power of 30 W / mL.

[0067] 2) Remove impurities such as metal catalyst particles, carbon nanotube bundles and amorphous carbon from the dispersion in step 1) by centrifugation purification. The centrifugation force is set to 210,000×g and the centrifugation time is 40 minutes. Take 80% of the supernatant.

[0068] 3) Introducing sodium dodecyl sulfate into the supernatant obtained in step 2), and modulating the surfactant in the carbon nanotube dispersion liquid into a composite surfactant of sodium dodecyl sulfate and sodium cholate by adding pure water, wherein the concentrations of carbon nanotubes, sodium dodecyl sulfate and sodium cholate are respectively: carbon nanotubes 0.6 mg / ml, sodium dodecyl sulfate 0.5 wt%, and sodium cholate concentration 0.5 wt%.

[0069] 4) Using a 10 mL medical gravity column cylinder to fill 5 mL Sephacryl S-200HR gel, loading 5 mL of the carbon nanotube dispersion liquid in step 3) into the prepared gel column, and then using sodium dodecyl sulfate (0.5 wt%) + sodium cholate (0.5 wt%) + sodium deoxycholate (X wt%) to stepwise elute the carbon nanotubes adsorbed in the gel column, and collecting the eluted carbon nanotube solution under the chromatographic column. The concentration of sodium deoxycholate (X wt%) is gradually increased, and is respectively X = 0.015 wt%, 0.02 wt%, 0.025 wt%, 0.028 wt%, 0.029 wt%, 0.031 wt%, 0.033 wt%, 0.035 wt%, 0.038 wt%, 0.040 wt%, 0.045 wt%, 0.050 wt%.

[0070] The original carbon nanotube dispersion liquid and the solutions of the eluted carbon nanotubes at different concentrations of sodium deoxycholate were characterized by absorption spectroscopy, and the results are shown in Figure 4 The black spectrum in the upper graph represents the absorption spectrum of the original CoMoCAT (SG65i) carbon nanotubes, and the spectra in the lower graph represent the absorption spectra of the stepwise eluted carbon nanotubes from the original carbon nanotubes in turn. The results show that it is impossible to separate the (5, 4) single-handed carbon nanotubes without cholic acid, and it is even more impossible to separate the (5, 4) single-handed mirror bodies, which further illustrates the important role of cholic acid therein.

Claims

1. A method for separating single chiral carbon nanotube enantiomers, comprising the steps of: (1) dispersing carbon nanotube raw material into a solution of composite surfactant to obtain a carbon nanotube dispersion; (2) separating the carbon nanotube dispersion by stepwise elution using gel chromatography and collecting the separation product to obtain single chiral carbon nanotube enantiomers; wherein the solution of composite surfactant comprises cholic acid, a first surfactant and optionally a second surfactant, and a solvent; the first surfactant is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate and sodium n-hexadecyl sulfate; the second surfactant is selected from one or more of sodium cholate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, sodium lithocholate, sodium hyodeoxycholate and sodium chenodeoxycholate; the method is used to separate small-diameter (5, 4) carbon nanotube enantiomers.

2. The method of claim 1, wherein, In the carbon nanotube dispersion, the concentrations of cholic acid, carbon nanotube, first surfactant and second surfactant are respectively: cholic acid 0.001-0.1 wt%, carbon nanotube 0.001-4 mg / ml, first surfactant 0.001-2 wt%, second surfactant 0.001-2 wt%, and the balance is solvent.

3. The method of claim 1, wherein, The composite surfactant comprises cholic acid, sodium dodecyl sulfate and sodium cholate.

4. The method of claim 1, wherein, The eluent used in stepwise elution is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium n-hexadecyl sulfate, sodium cholate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, sodium lithocholate, sodium hyodeoxycholate and sodium chenodeoxycholate.

5. The method of claim 1, wherein, The eluent used in stepwise elution comprises sodium dodecyl sulfate, sodium cholate and sodium deoxycholate.

6. The method of claim 1, wherein, The carbon nanotube raw material is synthesized by chemical vapor deposition, arc discharge or laser ablation.

7. The method of claim 1, wherein, The carbon nanotube raw material is metallic carbon nanotube or semiconductor carbon nanotube after separation and purification.

8. The method of claim 1, wherein, The carbon nanotube raw material is single-walled carbon nanotube with a tube diameter ranging from 0.6 to 3.0 nanometers.

9. The method of claim 1, wherein, The dispersing of carbon nanotube raw material into the solution of composite surfactant in step (1) is performed by water bath ultrasonic, cell disrupter ultrasonic, mechanical stirring or strong acid treatment.

10. The method of claim 1, wherein, The solvent is inorganic solvent and / or organic solvent.

11. The method of claim 10, wherein, The solvent is water.

12. The method of claim 1, wherein, The gel packing used in the gel chromatography is agarose series Separose, dextran-polyacrylamide series Sephacryl S, dextran series Sephadex™ or agarose-dextran series Surperdex™.

13. The method of claim 12, wherein, The matrix of the gel packing is dextran-polyacrylamide Sephacryl series gel produced by GE Healthcare.

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