Separation method of single-walled carbon nanotubes

Abstract

The invention provides a separation method of single-walled carbon nanotubes, which adopts a reversed-phase mode aqueous two-phase extraction separation of single chiral SWCNTs, and comprises the following processes: firstly preparing a PEG / Dex aqueous two-phase system and a single-walled carbon nanotube dispersion liquid SDC-SWCNTs dispersion liquid, then adding the SDC-SWCNTs dispersion liquid into an upper phase of the PEG / Dex aqueous two-phase system, then adding a SDS solution with a certain concentration into the system, and carrying out solid-liquid separation to obtain the single-walled carbon nanotubes. The preparation method comprises the following steps of: performing vortex mixing, centrifuging, adding an SDC solution with a certain concentration, performing extraction separation, and gradually increasing the SDC content in an extraction system to separate out single chiral single-walled carbon nanotubes with diameters from small to large. The separation method provided by the invention can realize rapid and efficient separation of the small-diameter single-walled carbon nanotubes.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon nanotubes, and in particular relates to a method for separating single-walled carbon nanotubes. Background Art

[0002] Single-walled carbon nanotubes (SWCNTs) are an important one-dimensional material, a member of the fullerene family, and one of the allotropes of crystalline carbon. It is usually composed of a hollow cylinder formed by curling a single or multi-layer graphene sheet, and its two ends are closed by fullerene hemispheres. Since the discovery of SWCNTs, due to its special molecular structure, single-walled carbon nanotubes have excellent properties, such as good electrical properties, mechanical properties, thermal properties and optical properties, and are widely used in the development of various new materials. However, the SWCNTs currently obtained are a mixture of metallic (m-SWCNTs) and semiconductor single-walled carbon nanotubes (s-SWCNTs). These mixtures of different chiral bodies have great differences in physical and chemical properties, mechanical properties, conductivity, etc. If the mixture material is directly applied to the fields of electronics, medicine and energy, its performance will be greatly limited. In order to obtain single-walled carbon nanotubes with specific structures and specific properties, they need to be separated. The properties of SWCNTs are closely related to their chirality, so it is of great significance to separate SWCNTs of a single chirality.

[0003] SWCNTs separation methods mainly include conjugated polymer encapsulation, density gradient centrifugation, ion exchange chromatography, gel chromatography and aqueous two-phase extraction (ATPE). Among them, ATPE is a commonly used separation method, usually composed of polyethylene glycol and dextran. Its basic principle is to mix the polymers in a certain mass ratio, and form two immiscible stable phases due to the density difference and interfacial tension of the two phases. In this case, the sample will be distributed between the two phases according to its hydrophilic / hydrophobic properties and the difference in the distribution coefficient relative to the two phases, thereby achieving separation.

[0004] The existing ATPE separation method usually adopts the normal phase separation mode, that is, the sample to be separated is loaded into the lower phase of the double aqueous phase, and the surfactant combination ratio is changed to gradually migrate the SWCNTs of different chirality from the hydrophilic lower phase to the hydrophobic upper phase, so as to achieve the effective separation of single chiral SWCNTs. This method is simple to operate. However, in the normal phase separation mode, carbon tubes with larger diameters are usually separated first, and small diameter carbon tubes are finally obtained. This method has problems such as long separation steps and low yield for the separation of small diameter SWCNTs. Summary of the invention

[0005] In view of this, the present invention provides a new method for separating single-walled carbon nanotubes, which shortens the steps of separating and purifying small-diameter SWCNTs.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for separating single-walled carbon nanotubes, using reverse phase double aqueous phase extraction to separate single chiral SWCNTs, comprises the following steps:

[0008] (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system;

[0009] (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system;

[0010] (3) Adding a certain concentration of SDS solution to the system obtained in step (2), vortex mixing and centrifuging, and then adding a certain concentration of SDC solution to perform extraction and separation, and by adjusting the SDC content in the extraction system, the desired single-chirality single-walled carbon nanotubes are directly separated after extraction and separation; and by gradually increasing the SDC content in the extraction system, single-chirality single-walled carbon nanotubes with diameters from small to large are separated.

[0011] The present invention is further configured to use a reverse phase mode aqueous two-phase extraction method to separate at least one single chiral SWCNTs in a single-walled carbon nanotube dispersion in order of diameter from small to large, comprising the following steps:

[0012] (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system;

[0013] (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system;

[0014] (3) using a certain concentration of SDS solution and SDC solution as extractants, adding them to the extraction system obtained in step (2), vortex mixing and centrifuging, taking the upper phase and the lower phase respectively, and detecting the phase where the single-walled carbon nanotubes are located; or, further comprising:

[0015] (4) adding the upper phase or lower phase that did not obtain a single chiral single-walled carbon nanotube in the previous step to the lower phase or upper phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; then adding a certain concentration of SDS solution and SDC solution as an extractant to the new two-phase aqueous system, separating the upper phase and the lower phase after vortex mixing and centrifugation to obtain single-walled carbon nanotubes of the desired diameter; or, further comprising:

[0016] (5) Step (4) is continued to be repeated until the desired single-walled carbon nanotubes are separated from the SDC-SWCNTs dispersion.

[0017] The present invention is further configured such that, in steps (3) to (5), the concentrations of the SDC solutions used in the extraction and separation processes are equal.

[0018] The present invention is further configured as follows: the concentration of the PEG solution used to prepare the PEG / Dex two-phase aqueous system is 10wt% to 20wt%, and the molecular weight of PEG is Mw=2000 to 10000; the concentration of the Dex solution is 10wt% to 20wt%, and the molecular weight of Dex is Mw=60000-70000.

[0019] The present invention is further configured such that, in the aqueous two-phase system, the concentrations and volumes of the PEG solution and the Dex solution are equal.

[0020] The present invention is further configured such that, in step (2), the volume ratio of the SDC-SWCNTs dispersion to the volume of the upper phase or the lower phase of the two-phase aqueous system is 1:(15-50).

[0021] The present invention is further configured that, in step (2), the SDC-SWCNTs dispersion is prepared by dispersing a certain mass of SWCNTs in the SDC solution, and the concentration of the SDC solution is 1.0 to 5.0 wt %; preferably, the concentration of the SDC solution is 1.0 to 2.5 wt %.

[0022] The present invention is further configured such that the mass volume ratio of the SWCNTs to the SDC solution is (0.5-1.5) mg / mL.

[0023] The present invention is further configured that in step (2), after mixing SWCNTs and SDC solution, ultrasonic dispersion and centrifugation are performed, and the supernatant obtained is the desired SDC-SWCNTs dispersion; the temperature of the ultrasonic dispersion is 0-10°C; and the centrifugal speed is 10000-20000rpm.

[0024] The present invention is further configured such that the mass fraction of the SDS solution added during the extraction and separation process is 5% to 15%, the mass fraction of the SDC solution is 0.5% to 2%, and the volume ratio of the SDS solution to the SDC solution is (10:1) to (1:5).

[0025] The present invention is further configured such that the mass fraction of the SDS solution is 9-11%, the concentration of the SDC solution is 0.8-1.2%, and the volume ratio of the SDS solution to the SDC solution is (5:1)-(1:5).

[0026] The present invention is further configured such that, in step (3), the amount of SDC solution added is gradually increased by fixing the amount of SDS solution added, so as to gradually increase the content of SDC in the extraction system.

[0027] The present invention is further configured such that the obtained single-chiral single-walled carbon nanotubes include one or more of (5,5)-SWCNTs, (7,3)-SWCNTs, (6,4)-SWCNTs, (9,1)-SWCNTs, (6,5)-SWCNTs, (8,3)-SWCNTs, (9,2)-SWCNTs, (7,5)-SWCNTs or (7,6)-SWCNTs.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The reverse phase mode aqueous two-phase extraction separation method provided by the present invention can enable small-diameter SWCNTs to migrate from the upper phase to the lower phase in preference to large-diameter SWCNTs under the action of SDC. Compared with the normal phase separation mode, this separation method is more conducive to the separation and purification of small-diameter SWCNTs, significantly shortens the separation steps, and improves the separation efficiency and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The UV-Vis-NIR absorption spectra of SWCNTs dispersed with different concentrations of dispersants in Example 1: (a) SDC; (b) SDS; (c) SC; (d) UV-Vis-NIR absorption spectra under the optimal dispersion conditions of the three surfactants.

[0031] Figure 2 It is the UV-Vis-NIR absorption spectrum of SWCNTs dispersion raw material.

[0032] Figure 3 This is the UV-visible-near-infrared absorption spectrum of single chiral SWCNTs obtained in double aqueous phase separation mode. DETAILED DESCRIPTION

[0033] The present invention is described in detail and completely with specific embodiments and in conjunction with the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0034] The raw materials in the examples of the present invention were directly purchased.

[0035] The embodiment of the present invention provides a method for separating single-walled carbon nanotubes, which uses a reverse phase mode aqueous two-phase extraction to separate single chiral SWCNTs, comprising the following steps:

[0036] (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system;

[0037] (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system;

[0038] (3) Adding a certain concentration of SDS solution to the system obtained in step (2), vortex mixing and centrifuging, and then adding a certain concentration of SDC solution to perform extraction and separation, and by adjusting the SDC content in the extraction system, the desired single-chirality single-walled carbon nanotubes are directly separated after extraction and separation; and by gradually increasing the SDC content in the extraction system, single-chirality single-walled carbon nanotubes with diameters from small to large are separated.

[0039] According to the above reversed-phase aqueous two-phase extraction separation method, those skilled in the art can understand how to adjust the content of SDC in the extraction system to obtain the desired single-chiral single-walled carbon nanotubes.

[0040] In one embodiment of the present invention, a reverse phase aqueous two-phase extraction method is used to separate at least one single chiral SWCNTs in a single-walled carbon nanotube dispersion in order of diameter from small to large, which specifically includes the following steps:

[0041] (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system;

[0042] (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system;

[0043] (3) using a certain concentration of SDS solution and SDC solution as extractants, adding them to the extraction system obtained in step (2), vortex mixing and centrifuging, taking the upper phase and the lower phase respectively, and detecting the phase where the single-walled carbon nanotubes are located; or, further comprising:

[0044] (4) adding the upper phase or lower phase that did not obtain a single chiral single-walled carbon nanotube in the previous step to the lower phase or upper phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; then adding a certain concentration of SDS solution and SDC solution as an extractant to the new two-phase aqueous system, separating the upper phase and the lower phase after vortex mixing and centrifugation to obtain single-walled carbon nanotubes of the desired diameter; or, further comprising:

[0045] (5) Step (4) is continued to be repeated until the desired single-walled carbon nanotubes are separated from the SDC-SWCNTs dispersion.

[0046] According to the above reversed phase mode aqueous two-phase extraction separation method, those skilled in the art can separate at least one type of single-walled carbon nanotube in the single-walled carbon nanotube dispersion in order from small to large diameters.

[0047] In one embodiment of the present invention, in steps (3) to (5), the concentrations of the SDC solutions used in the extraction and separation processes are equal.

[0048] In one embodiment of the present invention, the concentration of the PEG solution used to prepare the PEG / Dex two-phase aqueous system is 10wt% to 20wt%, and the molecular weight of PEG is Mw=2000 to 10000; the concentration of the Dex solution is 10wt% to 20wt%, and the molecular weight of Dex is Mw=60000-70000.

[0049] In one embodiment of the present invention, in the aqueous two-phase system, the concentration and volume of the PEG solution and the Dex solution are equal.

[0050] In one embodiment of the present invention, in step (2), the volume ratio of the SDC-SWCNTs dispersion to the volume of the upper phase or the lower phase of the two-phase aqueous system is 1:(15-50).

[0051] In one embodiment of the present invention, in step (2), the SDC-SWCNTs dispersion is prepared by dispersing a certain mass of SWCNTs in the SDC solution, and the concentration of the SDC solution is 1.0 to 5.0 wt %; preferably, the concentration of the SDC solution is 1.0 to 2.5 wt %.

[0052] In one embodiment of the present invention, the mass volume ratio of the SWCNTs to the SDC solution is (0.5-1.5) mg / mL.

[0053] In one embodiment of the present invention, in step (2), SWCNTs and SDC solution are mixed, ultrasonically dispersed, and centrifuged to obtain the supernatant, which is the desired SDC-SWCNTs dispersion; the temperature of the ultrasonic dispersion is 0 to 10° C.; and the centrifugal speed is 10,000 to 20,000 rpm.

[0054] In one embodiment of the present invention, the mass fraction of the SDS solution added during the extraction and separation process is 5% to 15%, the mass fraction of the SDC solution is 0.5% to 2%, and the volume ratio of the SDS solution to the SDC solution is (10:1) to (1:5).

[0055] In one embodiment of the present invention, the mass fraction of the SDS solution is 9-11%, the concentration of the SDC solution is 0.8-1.2%, and the volume ratio of the SDS solution to the SDC solution is (5:1)-(1:5).

[0056] In one embodiment of the present invention, in step (3), the amount of SDS solution added is fixed and the amount of SDC solution added is gradually increased to gradually increase the content of SDC in the extraction system.

[0057] In one embodiment of the present invention, the obtained single-chirality single-walled carbon nanotubes include one or more of (5,5)-SWCNTs, (7,3)-SWCNTs, (6,4)-SWCNTs, (9,1)-SWCNTs, (6,5)-SWCNTs, (8,3)-SWCNTs, (9,2)-SWCNTs, (7,5)-SWCNTs or (7,6)-SWCNTs.

[0058] The separation of single chiral SWCNTs by reverse phase aqueous two-phase extraction according to the present invention will be further described below with reference to specific examples.

[0059] Example 1

[0060] Preparation of SWCNTs dispersion

[0061] Take 3 portions of 1.0 mg SWCNTs and add them to 3 1.5 mL centrifuge tubes respectively. Add 1 mL of 1%, 2% and 5% SDC aqueous solution to each centrifuge tube, mix well and centrifuge for 5 seconds. Ultrasonic dispersion is performed at 225 W for 1 hour. Then, transfer the supernatant to a new centrifuge tube and centrifuge at 14800 rpm for 1 hour. Finally, take out the supernatant to obtain 3 different concentrations of SDC-SWCNTs dispersions.

[0062] Repeat the above operation and replace the three different mass fractions of SDC aqueous solution with 1%, 2% and 5% mass fractions of SDS aqueous solution and 1%, 2% and 5% mass fractions of sodium cholate (SC) aqueous solution, respectively, to obtain three different SDS-SWCNTs dispersions and three different SC-SWCNTs dispersions.

[0063] The SDC-SWCNTs dispersion, SDS-SWCNTs dispersion and SC-SWCNTs dispersion obtained above were diluted 40 times with pure water, and then the UV-visible-near infrared absorption spectra of the samples were measured in the wavelength range of 300-1300 nm. The results are as follows: Figure 1 As shown, Figure 1 (a) is the spectra of three SDC-SWCNTs dispersions, (b) is the spectra of three SDS-SWCNTs dispersions, (c) is the spectra of three SC-SWCNTs dispersions, and (d) is the curve comparison of the optimal results in (a), (b) and (c).

[0064] According to the results of UV-visible-near infrared absorption spectrum, it was finally determined that 1% SDC solution was used as a dispersant to prepare SWCNTs dispersion. The SDC-SWCNTs dispersion used in the subsequent examples was prepared by the following method: prepare a 2mL centrifuge tube, weigh 1.0mg SWCNTs and place it in the centrifuge tube, then add 1.0mL of 1% SDC solution by mass, and ultrasonically disperse it at 250W and ice water bath for 1h. Centrifuge the dispersion at 13800rpm for 1h at room temperature, take the supernatant to obtain SDC-SWCNTs dispersion, which is used in the subsequent examples. The UV-visible-near infrared absorption spectrum of the sample is as follows: Figure 2 shown.

[0065] Example 2

[0066] Separation of single chiral SWCNTs by aqueous two-phase extraction in reversed phase mode

[0067] (1) Prepare 12 1.5 mL centrifuge tubes, add 250 μL PEG (Mw=8000, 15 wt%) and 250 μL Dex (Mw=70000, 15 wt%) respectively, vortex mix and centrifuge to form a two-phase aqueous system.

[0068] (2) Add 10 μL of the SDC-SWCNTs dispersion prepared in Example 1 to the upper phase of the two-phase aqueous system into 12 centrifuge tubes respectively, and then add 15 μL of a 10% SDS solution, vortex mix, and centrifuge.

[0069] (3) Add 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, and 30 μL of 1% SDC solution to 12 centrifuge tubes, respectively, vortex to mix, and centrifuge;

[0070] (4) Take the upper phase and lower phase of the two-phase aqueous system in each centrifuge tube respectively, and different chiral SWCNTs can be obtained in the lower phase. The separation order is small diameter SWCNTs first, and large diameter SWCNTs later. The UV-visible-near infrared absorption spectrum of the sample is measured in the range of 300-1300nm. The results show that with the increase of SDC concentration, the separated high-purity SWCNTs are (5,5)-SWCNTs, (6,4)-SWCNTs, (7,3)-SWCNTs, (9,1)-SWCNTs, (6,5)-SWCNTs, (8,3)-SWCNTs, (9,2)-SWCNTs, (7,5)-SWCNTs and (7,6)-SWCNTs.

[0071] The UV-Vis-NIR absorption spectra of single chiral SWCNTs obtained under the double water phase separation mode are shown in Figure 2. Figure 3 shown.

[0072] Comparative Example 1

[0073] Normal phase aqueous two-phase extraction of single chiral SWCNTs

[0074] (1) Prepare 12 1.5 mL centrifuge tubes, add 250 μL PEG (Mw=8000, 15%, wt) and 250 μL Dex (15%, wt) respectively, vortex mix and centrifuge to form the same PEG / Dex two-phase aqueous system as in Example 2.

[0075] (2) Then, 10 μL of the SDC-SWCNTs dispersion prepared in Example 1 using a 2% SDC solution as a dispersant was added to each of the 12 centrifuge tubes to the lower phase of the aqueous double phase, and then 15 μL of a 1% SDC solution was added, vortexed and centrifuged.

[0076] (3) Add 3, 6, 10, 13, 16, 20, 23, 26, 30, 33, 36, and 40 μL of 10% SDS solution to the 12 centrifuge tubes, respectively, vortex to mix, and then centrifuge.

[0077] (4) Take the upper phase and lower phase of the two-phase aqueous system in each centrifuge tube respectively, and different chiral SWCNTs can be obtained in the upper phase. The separation order is large-diameter SWCNTs first, and small-diameter SWCNTs later. The UV-visible-near infrared absorption spectrum of the sample is measured in the range of 300-1300nm. The test results show that with the increase of SDS concentration, the separated SWCNTs are: (8,4)-SWCNTs, (7,5)-SWCNTs, (9,2)-SWCNTs, (8,3)-SWCNTs, (6,5)-SWCNTs, (9,1)-SWCNTs, (7,3)-SWCNTs and (6,4)-SWCNTs, and high-purity (5,5)-SWCNTs cannot be obtained.

[0078] The reverse phase two-phase aqueous extraction method described in Example 2 is used to continuously separate single-chiral SWCNTs in the single-walled carbon nanotube dispersion.

[0079] Example 3

[0080] The separation of (5,5)-SWCNTs specifically includes the following steps:

[0081] (1) Prepare a 1.5 mL centrifuge tube, add 250 μL PEG (15%, wt) and 250 μL Dex (15%, wt), vortex mix and centrifuge to form the same PEG / Dex two-phase aqueous system as in Example 2.

[0082] (2) 10 μL of the SDC-SWCNTs dispersion prepared in Example 1 was added to the upper phase of the PEG / Dex aqueous two-phase system, 15 μL of SDS solution (10%, wt) was added, vortexed and centrifuged, and then 5 μL of SDC solution (1%, wt) was added. After vortexing and centrifugation, the gray-white lower phase was removed with a pipette to obtain (5,5)-SWCNTs with a purity of 66.4%.

[0083] Comparative Example 2

[0084] The separation of (5,5)-SWCNTs specifically includes the following steps:

[0085] (1) Prepare a 1.5 mL centrifuge tube, add 250 μL PEG (15%, wt) and 250 μL Dex (15%, wt), vortex mix and centrifuge to form the same PEG / Dex two-phase aqueous system as in Example 2.

[0086] (2) 10 μL of the SDC-SWCNTs dispersion prepared in Example 1 was added to the upper phase of the aqueous biphase system, 30 μL of SDS solution (10%, wt) was added, vortexed and centrifuged, the upper phase was removed with a pipette, the lower phase was mixed with the blank aqueous biphase upper phase, and about 2 μL of SDS solution (10%, wt) was added, vortexed and centrifuged, and the upper phase was removed with a pipette to obtain (5,5)-SWCNTs with a purity of 65.0%.

[0087] Example 4

[0088] Separation of (7,3)-SWCNTs and (6,4)-SWCNTs

[0089] (1) Prepare a 1.5 mL centrifuge tube, add 250 μL PEG (15%, wt) and 250 μL Dex (15%, wt) respectively, vortex mix and centrifuge to form a blank PEG / Dex two-phase aqueous system the same as Example 2.

[0090] (2) Take the upper phase separated in step (2) of Example 3 and the lower phase of the blank PEG / Dex aqueous two-phase system, vortex and centrifuge to form a new aqueous two-phase system, add 15 μL SDS solution (10%, wt), vortex and centrifuge, add 10 μL SDC solution (1%, wt), vortex and centrifuge, remove the gray-purple lower phase and the blank aqueous two-phase upper phase with a pipette, vortex and centrifuge, and form a new aqueous two-phase system again. Then add about 10 μL SDC solution (1%, wt), vortex and centrifuge, and remove the upper phase and lower phase with a pipette to obtain high-purity (7,3)-SWCNTs and (6,4)-SWCNTs, respectively.

[0091] Example 5

[0092] Separation of (9,1)-SWCNTs

[0093] Prepare a 1.5mL centrifuge tube, add 250μL PEG (15%, wt) and 250μL Dex (15%, wt) respectively, vortex mix and centrifuge to form a blank PEG / Dex two-phase aqueous system the same as Example 2. Take the upper phase after removing the gray-purple lower phase from the first new two-phase aqueous system in step (2) of Example 4 and the lower phase of the blank PEG / Dex two-phase aqueous system, vortex mix and centrifuge to form a new two-phase aqueous system, add 15μL SDS solution (10%, wt) and vortex mix and centrifuge, then add 12.5μL SDC solution (1%, wt), vortex mix and centrifuge, remove the gray-purple lower phase and the blank two-phase upper phase with a pipette, vortex mix and centrifuge, and form a new two-phase aqueous system again. Add about 12.5μL SDC solution (1%, wt), vortex mix and centrifuge, remove the lower phase with a pipette, and remove the lower phase with a pipette to obtain (9,1)-SWCNTs with a purity of 92.3%.

[0094] Example 6

[0095] Separation of (6,5)-SWCNTs

[0096] Prepare a 1.5mL centrifuge tube, add 250μL PEG (15%, wt) and 250μL Dex (15%, wt) respectively, vortex mix and centrifuge to form the same blank PEG / Dex two-phase aqueous system as in Example 2. Vortex mix and centrifuge the remaining upper phase after removing the lower phase in the last step of Example 5 and the lower phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; add 15μL SDS solution (10%, wt) and vortex mix and centrifuge, then add 15μL SDC solution (1%, wt), vortex mix and centrifuge, remove the dark purple lower phase and the blank two-phase upper phase with a pipette, vortex mix and centrifuge, and form a new two-phase aqueous system again. Add 10μL SDC solution (1%, wt), vortex mix and centrifuge, remove the light purple lower phase with a pipette, and separate (6,5)-SWCNTs with a purity of 97.7%.

[0097] Example 7

[0098] Prepare a 1.5mL centrifuge tube, add 250μL PEG (15%, wt) and 250μL Dex (15%, wt) respectively, vortex mix and centrifuge to form a blank PEG / Dex two-phase aqueous system as in Example 2. Vortex mix and centrifuge the remaining upper phase after removing the lavender lower phase in the last step of Example 6 and the lower phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; add 15μL SDS solution (10%, wt) and vortex mix and centrifuge, then add 18μL SDC solution (1%, wt), vortex mix and centrifuge, remove the gray-green lower phase and the blank two-phase upper phase with a pipette, vortex mix and centrifuge, and form a new two-phase aqueous system again. Add 15-18μL SDC solution (1%, wt), vortex mix and centrifuge, remove the light green upper phase with a pipette, and obtain (8,3)-SWCNTs with a purity of 96.7%.

[0099] Example 8

[0100] Separation of (9,2)-SWCNTs

[0101] Prepare a 1.5mL centrifuge tube, add 250μL PEG (15%, wt) and 250μL Dex (15%, wt) respectively, vortex mix and centrifuge to form the same blank PEG / Dex two-phase aqueous system as in Example 2. Vortex mix and centrifuge the remaining upper phase after removing the gray-green lower phase from the first new two-phase aqueous system in Example 7 and the lower phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; add 10μL SDS solution (10%, wt) and vortex mix and centrifuge, add 10μL SDC solution (1%, wt), vortex mix and centrifuge, remove the lower phase and the blank two-phase upper phase with a pipette, vortex mix and centrifuge to form a new two-phase aqueous system. Then add about 15μL SDC solution (1%, wt), vortex mix and centrifuge, remove the light green upper phase and the blank two-phase lower phase with a pipette, vortex mix and centrifuge to form a new two-phase aqueous system. Then, SDC solution (1%, wt) was slowly added, vortexed and centrifuged, and the lower phase of the biphasic aqueous phase was observed. When the lower phase turned light green, the upper phase was removed with a pipette to obtain (9,2)-SWCNTs.

[0102] Example 9

[0103] Separation of (7,6)-SWCNTs and (7,5)-SWCNTs

[0104] Prepare a 1.5mL centrifuge tube, add 250μL PEG (15%, wt) and 250μL Dex (15%, wt) respectively, vortex mix and centrifuge to form the same blank PEG / Dex two-phase aqueous system as in Example 2. Vortex mix and centrifuge the remaining upper phase after removing the lower phase of the first new two-phase aqueous system in Example 8 and the lower phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase system; vortex mix and centrifuge 15μL SDS solution (10%, wt), add 20μL SDC solution (1%, wt), vortex mix and centrifuge, remove the upper phase and the blank two-phase lower phase with a pipette, vortex mix and centrifuge to form a new two-phase system. Then add about 18μL SDC solution (1%, wt), vortex mix and centrifuge, remove the lower phase and the blank two-phase upper phase with a pipette, vortex mix and centrifuge to form a new two-phase system. SDC solution (1%, wt) was then slowly added, vortexed and centrifuged until both the upper and lower phases became slightly turbid. The upper and lower phases were removed with a pipette to obtain (7,6)-SWCNTs and (7,5)-SWCNTs, with purity values ​​of 51.4% and 65.2%, respectively.

[0105] Comparative Example 3

[0106] Prepare a 1.5 mL centrifuge tube, add 250 μL PEG (15%, wt) and 250 μL Dex (15%, wt), vortex mix and centrifuge to form a two-phase aqueous system.

[0107] Add 10 μL of SDC-SWCNTs dispersion to the upper phase of the biphasic aqueous phase, add 22 μL of SDS solution (10%, wt), vortex mix and centrifuge, remove the upper phase with a pipette, mix the lower phase with the blank biphasic aqueous phase upper phase, add about 2 μL of SDS solution (10%, wt), vortex mix and centrifuge, remove the upper phase with a pipette to obtain (9,1)-SWCNTs with a purity of 91.0%.

[0108] Comparative Example 4

[0109] Prepare a 1.5 mL centrifuge tube, add 250 μL PEG (15%, wt) and 250 μL Dex (15%, wt), vortex mix and centrifuge to form the same two-phase aqueous system as Example 2. Add 10 μL SDC-SWCNTs dispersion to the upper phase of the two-phase aqueous system, add 19 μL SDS solution (10%, wt), vortex mix and centrifuge, remove the upper phase with a pipette, mix the lower phase with the blank two-phase upper phase, add 2 μL SDS solution (10%, wt), vortex mix and centrifuge, remove the upper phase with a pipette to obtain (6,5)-SWCNTs with a purity of 95.0%.

[0110] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for separating single-walled carbon nanotubes, characterized in that: The single chiral SWCNTs are separated by aqueous two-phase extraction in reverse phase mode, comprising the following steps: (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system; (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system; (3) Adding a certain concentration of SDS solution to the system obtained in step (2), vortex mixing and centrifuging, and then adding a certain concentration of SDC solution to perform extraction and separation, and by adjusting the SDC content in the extraction system, the desired single-chirality single-walled carbon nanotubes are directly separated after extraction and separation; and by gradually increasing the SDC content in the extraction system, single-chirality single-walled carbon nanotubes with diameters from small to large are separated.

2. The method for separating single-walled carbon nanotubes according to claim 1, characterized in that: The method uses a reverse phase aqueous two-phase extraction method to separate at least one single chiral SWCNTs in a single-walled carbon nanotube dispersion in order of diameter from small to large, comprising the following steps: (1) taking a PEG solution and a Dex solution, vortex mixing and then centrifuging to obtain a PEG / Dex aqueous two-phase system; (2) using sodium deoxycholate aqueous solution as a dispersant to prepare a single-walled carbon nanotube dispersion SDC-SWCNTs dispersion, and adding the SDC-SWCNTs dispersion to the upper phase of the PEG / Dex two-phase aqueous system; (3) using a certain concentration of SDS solution and SDC solution as an extractant, adding them to the extraction system obtained in step (2), vortex mixing and centrifuging, taking the upper phase and the lower phase respectively, and detecting the phase where the single-walled carbon nanotubes are located; Or, also include: (4) adding the upper phase or lower phase that did not obtain a single chiral single-walled carbon nanotube in the previous step to the lower phase or upper phase of the blank PEG / Dex two-phase aqueous system to form a new two-phase aqueous system; then adding a certain concentration of SDS solution and SDC solution as an extractant to the new two-phase aqueous system, separating the upper phase and the lower phase after vortex mixing and centrifugation to obtain single-walled carbon nanotubes of the desired diameter; or, further comprising: (5) Step (4) is continued to be repeated until the desired single-walled carbon nanotubes are separated from the SDC-SWCNTs dispersion.

3. The method for separating single-walled carbon nanotubes according to claim 2, characterized in that: In steps (3) to (5), the concentrations of the SDC solutions used in the extraction and separation processes are equal.

4. The method for separating single-walled carbon nanotubes according to claim 1 or 2, characterized in that: In step (1), the concentration of the PEG solution used to prepare the PEG / Dex two-phase aqueous system is 10wt% to 20wt%, and the molecular weight of PEG is Mw=2000 to 10000; the concentration of the Dex solution is 10wt% to 20wt%, and the molecular weight of Dex is Mw=60000-70000.

5. The method for separating single-walled carbon nanotubes according to claim 1 or 2, characterized in that: In step (2), the volume ratio of the SDC-SWCNTs dispersion to the upper phase or lower phase of the PEG / Dex aqueous two-phase system is 1:(15-50).

6. The method for separating single-walled carbon nanotubes according to claim 1 or 2, characterized in that: In step (2), the SDC-SWCNTs dispersion is prepared by dispersing a certain mass of SWCNTs in the SDC solution, and the concentration of the SDC solution is 1.0 to 5.0 wt %.

7. The method for separating single-walled carbon nanotubes according to claim 6, characterized in that: In step (2), SWCNTs and SDC solution are mixed, ultrasonically dispersed, and centrifuged to obtain the supernatant, which is the desired SDC-SWCNTs dispersion. The temperature of the ultrasonic dispersion is 0-10°C; and the centrifugal speed is 10000-20000 rpm.

8. The method for separating single-walled carbon nanotubes according to claim 1 or 2, characterized in that: The mass fraction of the SDS solution added during the extraction and separation process is 5% to 15%, the mass fraction of the SDC solution is 0.5% to 2%, and the volume ratio of the SDS solution to the SDC solution is (10:1) to (1:5).

9. The method for separating single-walled carbon nanotubes according to claim 1, characterized in that: In step (3), the amount of SDS solution added is fixed and the amount of SDC solution added is gradually increased to gradually increase the content of SDC in the extraction system.

10. The method for separating single-walled carbon nanotubes according to claim 1 or 2, characterized in that: The obtained single-chiral single-walled carbon nanotubes include one or more of (5,5)-SWCNTs, (7,3)-SWCNTs, (6,4)-SWCNTs, (9,1)-SWCNTs, (6,5)-SWCNTs, (8,3)-SWCNTs, (9,2)-SWCNTs, (7,5)-SWCNTs or (7,6)-SWCNTs.

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