阅读说明：本技术 一种提高单分散的碳纳米管分散液浓度的方法 (Method for improving concentration of monodisperse carbon nanotube dispersion liquid ) 是由 杨德华 刘华平 魏小均 周维亚 解思深 于 2019-03-26 设计创作，主要内容包括：本发明提供了一种提高单分散的碳纳米管分散液浓度的方法,所述方法包括以下步骤：1)制备碳纳米管材料与表面活性剂溶液的初始分散液；2)将步骤1)得到的碳纳米管的初始分散液离心,收集上层分散液；3)分散步骤2)得到的上层分散液；4)将步骤3)得到的分散液离心,取上层分散液,即得。本发明通过分散-离心-再分散-再离心的方式,去除了分散液中的杂质成分以及难以分散的碳纳米管团聚物,将分散设备输出的能量集中于小碳纳米管束的分散,保证了碳纳米管的充分分散,节省了总的能耗和样品的制备时间,尤其适合于含有杂质较多的碳纳米管以及高浓度碳纳米管分散液的制备。(The invention provides a method for improving the concentration of a monodisperse carbon nanotube dispersion liquid, which comprises the following steps: 1) preparing an initial dispersion liquid of a carbon nanotube material and a surfactant solution; 2) centrifuging the initial dispersion liquid of the carbon nano tube obtained in the step 1), and collecting the upper dispersion liquid; 3) dispersing the upper layer dispersion liquid obtained in the step 2); 4) centrifuging the dispersion liquid obtained in the step 3), and taking the upper-layer dispersion liquid to obtain the nano-silver-containing nano-silver dispersion liquid. According to the invention, through the modes of dispersion, centrifugation, redispersion and recentrifugation, impurity components and carbon nano tube agglomerates which are difficult to disperse in the dispersion liquid are removed, the energy output by the dispersion equipment is concentrated in the dispersion of the small carbon nano tube bundle, the full dispersion of the carbon nano tubes is ensured, the total energy consumption and the preparation time of the sample are saved, and the method is particularly suitable for preparing the carbon nano tubes containing more impurities and the high-concentration carbon nano tube dispersion liquid.)

1. A method of increasing the concentration of a monodisperse carbon nanotube dispersion, the method comprising the steps of:

1) preparing an initial dispersion liquid of a carbon nanotube material and a surfactant solution;

2) centrifuging the initial dispersion liquid of the carbon nano tube obtained in the step 1), and collecting the upper dispersion liquid;

preferably, 80 wt% to 90 wt% of the upper layer dispersion is collected;

3) further dispersing the upper layer dispersion liquid obtained in the step 2);

4) centrifuging the dispersion liquid obtained in the step 3), and collecting the upper-layer dispersion liquid, preferably collecting all the upper-layer dispersion liquid or collecting 90-99 wt% of the upper-layer dispersion liquid.

2. The process according to claim 1, wherein in step 1) the concentration of carbon nanotubes in the initial dispersion is between 0.001 and 4mg/mL, preferably between 1.5 and 4 mg/mL.

3. The method according to claim 1 or 2, wherein, in step 1), the carbon nanotube material is a powdered carbon nanotube, a bulk carbon nanotube, a sheet carbon nanotube, or a carbon nanotube film;

preferably, the carbon nanotube material is a single-walled carbon nanotube, a few-walled carbon nanotube, a multi-walled carbon nanotube, or a hybrid of carbon nanotubes with other carbon materials.

4. A process according to any one of claims 1 to 3, wherein, in step 1), the initial dispersion is obtained by a process comprising the steps of:

mixing a carbon nanotube material with a surfactant solution;

soaking in surfactant solution, shearing in an emulsifying machine and/or ultrasonic treatment to obtain initial dispersion liquid;

preferably, the ultrasonic treatment is ultrasonic treatment using a water bath ultrasonic device or ultrasonic treatment using a cell crusher; more preferably, the sonication power is 2-50W/cm depending on the total amount of dispersion to be prepared when using the cell disruptor²Preferably 2-30W/cm²The ultrasonic time is 2-50 hours, preferably 2-36 hours, and the ultrasonic mode is continuous ultrasonic or pulse ultrasonic.

5. The method according to any one of claims 1 to 4, wherein, in step 1), the solute of the surfactant solution is one or more surfactants; the solvent is water or an organic solvent;

preferably, the surfactant is selected from anionic, cationic or nonionic surfactants; more preferably, the surfactant is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium n-hexadecyl sulfate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, and sodium deoxycholate hydrate; still further preferably, the surfactant is selected from one or more of sodium lauryl sulfate, sodium cholate and sodium deoxycholate;

preferably, the surfactant solution is an aqueous solution containing one or more of the following components:

0 to 1 weight percent of sodium deoxycholate, 0.1 to 2 weight percent of sodium cholate and 0.3 to 5 weight percent of sodium dodecyl sulfate.

6. The method according to any one of claims 1 to 5, wherein, in step 2), the centrifugation is ordinary centrifugation, centrifugal ultrafiltration, ultracentrifugation or density gradient ultracentrifugation;

preferably, the centrifugation is ultracentrifugation or density gradient ultracentrifugation;

preferably, the centrifugal force of the centrifugation is 210000g-1050000g, and the centrifugation time is 2-120 minutes; more preferably, the centrifugation time is 2-60 minutes.

7. The method according to any one of claims 1 to 6, wherein, in step 3), the further dispersing is ultrasonic dispersing with a cell crusher; preferably, when the ultrasonic dispersion is carried out by using a cell crusher, the power of the ultrasonic dispersion is 2-50W/cm²(ii) a Preferably, the ultrasonic dispersion power is 2-30W/cm²The dispersion time is 1 minute to 3 hours, and the ultrasonic mode is continuous ultrasonic or pulse ultrasonic.

8. The method according to claim, wherein, in step 4), the centrifugation is ordinary centrifugation or ultracentrifugation;

preferably, the centrifugal force of the common centrifugation is 200g-10000g, and the time is 2-30 min;

more preferably, the centrifugal force of the ultracentrifugation is 210000g-1050000g for 2-30 min.

Technical Field

The invention belongs to the field of preparation of nano materials. In particular, the present invention relates to a method of increasing the concentration of a monodisperse carbon nanotube dispersion.

Background

The carbon nano tube has excellent electrical, mechanical and thermal properties and high chemical stability due to the unique one-dimensional tubular structure, and has wide application prospects in the fields of electronics, optoelectronic integrated circuits, optical communication, biological medicine and the like. However, the special properties of carbon nanotubes are derived from their structure, and small differences in structure will result in large differences in properties. For a long time, synthesized carbon nanotubes usually exist in the form of a mixture of various structures, and due to the diversity of the structures, the properties of the synthesized carbon nanotubes are unpredictable and difficult to be directly applied, which requires the preparation of carbon nanotubes with uniform properties by subsequent separation techniques. In the process of growing and preparing the carbon nano tube, because strong intermolecular force exists among the tubes, a plurality of carbon nano tubes with different structures are usually intertwined together to form a beam shape, and macroscopically, the carbon nano tubes are usually expressed as powder, a film or a block. In order to realize the separation of the carbon nanotube structure, the precondition is that the carbon nanotube solution is prepared by suspending the carbon nanotube which is dispersed into single carbon nanotube powder, thin film or block in the aqueous solution or organic solvent in the aqueous solution or organic solution.

The current methods for preparing carbon nanotube dispersions include emulsification, milling and ultrasonic dispersion. Although the emulsification method and the grinding method can disperse the solid carbon nanotube powder in the solution, the dispersibility is difficult to achieve the monodispersion effect, and the separation of the carbon nanotube structure cannot be satisfied. The ultrasonic dispersion method has higher dispersion capability and is the most effective method for preparing the monodisperse carbon nanotube solution at present. The ultrasonic dispersion of carbon nanotubes is to tear the carbon nanotube bundle into single carbon nanotubes to suspend in water solution or organic solvent under the adsorption of surfactant molecules or organic polymer molecules and the action of high-power ultrasonic waves. However, the traditional ultrasonic dispersion method is difficult to disperse and prepare high-concentration monodisperse carbon nanotube solution, and greatly reduces the separation efficiency and yield of the carbon nanotubes, thereby preventing the application of the carbon nanotubes in the fields of electronics, photoelectrons, biomedicine and the like.

With the development of the carbon nanotube separation technology and the continuous breakthrough of the application field of the carbon nanotube and the gradual market orientation, the demand for developing the macro preparation technology of the high-concentration monodisperse carbon nanotube solution becomes more urgent.

Disclosure of Invention

The invention aims to provide a preparation method of a high-concentration monodisperse carbon nanotube solution aiming at the defects of the prior art. By using the method of the invention, on the basis of preparing the single-dispersion carbon nanotube solution by traditional ultrasonic waves (the highest dispersion concentration can reach 1mg/mL generally), the concentration of the carbon nanotube dispersion solution is increased by multiple times (the dispersion concentration can reach 1.5-4mg/mL), the monodispersion effect is still achieved, and the dispersion and separation efficiency of the carbon nanotube is greatly improved.

In one aspect, the present invention provides a method for increasing the concentration of a monodisperse carbon nanotube dispersion, the method comprising the steps of:

1) preparing an initial dispersion liquid of a carbon nanotube material and a surfactant solution;

2) centrifuging the initial dispersion liquid of the carbon nano tube obtained in the step 1), and collecting the upper dispersion liquid;

preferably, 80 wt% to 90 wt% of the upper layer dispersion is collected;

3) dispersing the upper layer dispersion liquid obtained in the step 2);

4) centrifuging the dispersion liquid obtained in the step 3), and collecting the upper-layer dispersion liquid, preferably collecting all the upper-layer dispersion liquid or collecting 90-99 wt% of the upper-layer dispersion liquid to obtain the dispersion liquid;

the method according to the invention, wherein in step 1), the concentration of carbon nanotubes in the initial dispersion is between 0.001 and 4 mg/mL; preferably 1.5-4 mg/mL.

The method according to the present invention, wherein, in step 1), the carbon nanotube material is a powdered carbon nanotube, a bulk carbon nanotube, a sheet carbon nanotube or a carbon nanotube film;

preferably, the structure of the carbon nanotube is a single-walled carbon nanotube, a few-walled carbon nanotube, a multi-walled carbon nanotube, and a hybrid of the carbon nanotube and other carbon materials.

The method according to the invention, wherein the initial dispersion of step 1) is obtained by a method comprising the following steps:

mixing a carbon nanotube material with a surfactant solution;

soaking in surfactant solution, shearing in emulsifier and/or ultrasonic treatment to obtain initial dispersion liquid;

preferably, the ultrasound is sonication using a water bath sonication apparatus or sonication using a cell disruptor; more preferably, the sonication power is 2-50W/cm when using a cell disruptor²Preferably 2-30W/cm²(ii) a The ultrasound time is 2-50 hours, preferably 2-36 hours, and the ultrasound mode is continuous ultrasound or pulse ultrasound.

The method according to the present invention, wherein, in step 1), the solute of the surfactant solution is one or more surfactants; the solvent is water or an organic solvent;

preferably, the surfactant is selected from one or more of an anionic surfactant, a cationic surfactant or a nonionic surfactant; more preferably, the surfactant comprises one or more anionic surfactants; further preferably, the anionic surfactant is selected from one or more of sodium octyl sulfate, sodium decyl sulfate, sodium dodecyl sulfate, sodium n-hexadecyl sulfate, sodium cholate hydrate, sodium dehydrocholate, sodium deoxycholate, and sodium deoxycholate hydrate; still further preferably, the anionic surfactant is selected from one or more of Sodium Dodecyl Sulfate (SDS), Sodium Cholate (SC), and sodium Deoxycholate (DOC).

In a preferred embodiment of the present invention, the surfactant solution is an aqueous solution of one or more selected from sodium dodecyl sulfate, sodium cholate, sodium deoxycholate;

the method according to the invention, wherein the aqueous surfactant solution has one or more of the following components:

0-1 wt% of sodium Deoxycholate (DOC), 0.1-2 wt% of Sodium Cholate (SC) and 0.3-5 wt% of Sodium Dodecyl Sulfate (SDS).

The method according to the invention, wherein, in step 2), the centrifugation is ordinary centrifugation, centrifugal ultrafiltration, ultracentrifugation or density gradient ultracentrifugation; preferably, the centrifugation is ultracentrifugation or density gradient ultracentrifugation; preferably, the centrifugal force of the centrifugation is 210000g-1050000g, and the centrifugation time is 2-120 minutes; more preferably, the centrifugation time is 2-60 minutes.

The method according to the invention, wherein, in step 3), the dispersing is ultrasonic dispersing by using a cell crusher; preferably, when the ultrasonic dispersion is carried out by using a cell crusher, the power of the ultrasonic dispersion is 2-50W/cm²(ii) a Preferably, the ultrasonic dispersion power is 2-30W/cm²The dispersion time is 1 minute to 3 hours, and the ultrasonic mode is continuous ultrasonic or pulse ultrasonic.

The method according to the invention, wherein, in step 4), the centrifugation is ordinary centrifugation or ultracentrifugation;

preferably, the centrifugal force of the ordinary centrifugation is 200g-10000g, and the time is 2-30 min.

Preferably, the centrifugal force of the ultracentrifugation is 210000g-105000g for 2-30 min.

The inventors have found that, using the method of the present invention, bundled high concentration carbon nanotubes have been dispersed to an extent that they can remain stable in solution when preparing the initial dispersion; during the first centrifugation, impurities in the original carbon nano tube and carbon nano tube agglomerates which are difficult to disperse in the solution can be removed; then, the carbon nano tubes with better dispersion in the upper layer liquid are dispersed for a short time or mildly, and then the monodisperse carbon nano tube dispersion liquid can be obtained.

According to the invention, impurity components and carbon nanotube agglomerates which are difficult to disperse in the dispersion liquid are removed through a dispersion-centrifugation mode, the energy output by the dispersion equipment is concentrated on the dispersion of the carbon nanotubes in the redispersion process, and the carbon nanotubes are fully dispersed, so that the high-efficiency preparation of the monodisperse carbon nanotube solution is realized.

The invention provides a method for efficiently preparing a monodisperse carbon nanotube solution. The dispersion degree of the carbon nanotube dispersion liquid is subjected to structural separation on the carbon nanotubes in the dispersion liquid by adopting a gel chromatography, and then the monodispersity of the carbon nanotubes in the dispersion liquid is evaluated according to the structural purity of the carbon nanotubes prepared by separation.

The conventional procedure of gel chromatography can be described as regulating the gel chromatography column, the carbon nanotube dispersion, the eluent to a set separation temperature; loading the carbon nanotube dispersion liquid into a chromatographic column, wherein at the temperature, the packing matrix in the chromatographic column selectively adsorbs the carbon nanotubes with specific structures, and other carbon nanotubes which are not adsorbed flow out from an outlet of the chromatographic column along with the solution; and then injecting the eluent into a gel column, and collecting the eluted carbon nanotube solution at an outlet at the lower end of the gel column to obtain the carbon nanotube with the specific structure prepared by separation. According to a feature of the present invention, the temperature for separating the carbon nanotubes is set to 8 to 11 ℃.

And characterizing the carbon nano tube prepared by separation by using an ultraviolet-visible-near infrared spectrophotometer. The carbon nano tube is a one-dimensional tubular molecule and has a splitting energy band structure with adjustable structure. So that the carbon nanotubes with different structures show different optical transition energies, namely characteristic light absorption peaks. The carbon nanotube structure can be determined by testing and characterizing the light absorption peak of the carbon nanotube. Each structural carbon nanotube has several discrete sharp absorption peaks corresponding to its corresponding energy sub-band. When the tested sample contains carbon nanotubes with various structures, a plurality of light absorption peaks are formed on the light absorption spectrum of the tested sample and respectively correspond to the carbon nanotubes with different structures. Accordingly, the structural distribution or purity of the carbon nanotubes prepared by separation can be evaluated by light absorption spectroscopy.

Compared with the traditional preparation method of the dispersion liquid, the method provided by the invention has the advantages of high dispersion efficiency, high dispersion concentration and low energy consumption, so that the method is an efficient high-concentration monodisperse carbon nanotube solution method, the separation efficiency and the yield of the carbon nanotubes are greatly improved, and the property and application research of the carbon nanotubes are effectively promoted.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a graph showing absorption spectra of an initial dispersion of carbon nanotubes and an effluent from the end of a gel column at 10 ℃ in example 1 according to the present invention; wherein FIG. 1A is a light absorption spectrum of a carbon nanotube dispersion of 2mg/mL, and FIG. 1B is a light absorption spectrum of a carbon nanotube solution separated by gel chromatography at 10 ℃.

FIG. 2 is an absorption spectrum of an initial dispersion of carbon nanotubes and an effluent from the end of a gel column at 10 ℃ according to example 2 of the present invention; wherein FIG. 2A is a light absorption spectrum of an original carbon nanotube dispersion of 1.5 mg/mL; FIG. 2B is a light absorption spectrum of the carbon nanotube solution separated by gel chromatography at 10 ℃.

FIG. 3 is an absorption spectrum of an initial dispersion of carbon nanotubes and an effluent from the end of a gel column at 10 ℃ according to example 3 of the present invention; wherein FIG. 3A is a light absorption spectrum of a 4mg/mL original carbon nanotube dispersion; FIG. 3B is a normalized light absorption spectrum of a carbon nanotube solution separated by gel chromatography at 10 ℃.

FIG. 4 is an absorption spectrum of an initial dispersion of carbon nanotubes and an effluent from the end of a gel column at 10 ℃ according to example 4 of the present invention; wherein FIG. 4A is a light absorption spectrum of an original carbon nanotube dispersion of 3mg/mL, and FIG. 4B is a light absorption spectrum of a carbon nanotube solution separated by gel chromatography at 10 ℃.

FIG. 5 is an absorption spectrum of the initial dispersion of carbon nanotubes and the effluent from the end of the gel column at 10 ℃ according to comparative example 1 of the present invention; wherein FIG. 5A is a light absorption spectrum of an original 1mg/mL carbon nanotube dispersion, and FIG. 5B is a light absorption spectrum of a carbon nanotube solution eluted and collected from a gel column by an eluent.

FIG. 6 is a graph showing the integration of the absorption spectra of the original carbon nanotube dispersion of FIGS. 1A, 4A and 5A and the end of the column effluent of FIGS. 1B, 4B and 5B; in which the original dispersion light absorption spectra are integrated in figure 6A, their corresponding light absorption spectra for the carbon nanotube solution eluted from the gel column at 10 ℃ are integrated in figure 6B.

FIG. 7 is an absorption spectrum showing the integration of the line in FIG. 1B and the absorption spectrum of the effluent at the end of the gel column at 10 ℃ of comparative example 2 according to the present invention.

Fig. 8 is a flow chart of a method according to the invention.

Detailed Description

The following examples illustrate the invention in detail.