CN-122010100-A - Carbon nano tube specific separation method using ammonium salt functionalized silicon oxide microsphere

Abstract

The invention discloses a method for specifically separating carbon nanotubes by using ammonium salt functionalized silica microspheres, belonging to the technical field of carbon nanotube purification. The method comprises the steps of firstly, carrying out surface modification on silicon oxide microspheres by utilizing aminosilane to graft amino groups, then converting the amino groups into ammonium salt groups through acid liquor treatment to obtain functional silicon oxide microspheres with the ammonium salt groups on the surfaces, contacting the microspheres with carbon nanotube dispersion liquid, selectively adsorbing metal carbon nanotubes and short carbon nanotubes in the dispersion liquid, and carrying out solid-liquid separation to obtain a semiconductor type carbon nanotube solution enriched with long carbon tubes. The method of the invention does not need to rely on ultra-high speed centrifugation, can synchronously realize the high purity separation of the metal type/semiconductor type of the carbon nano tube and the high efficiency separation of the long/short carbon tubes in a single process step, can reduce the damage to the long carbon tubes and simultaneously consider the separation efficiency and the material length, has simple and flexible process, and is suitable for preparing the semiconductor type carbon nano tube material required by the high-performance carbon-based electronic device.

Inventors

• XIA YU
• CHANG CHENG

Assignees

• 北京大学

Dates

Publication Date

20260512

Application Date

20260109

Claims (10)

1. 1. The carbon nanotube specific separation method for the silicon oxide microsphere functionalized by ammonium salt is characterized by comprising the following steps of: a) Providing a carbon nanotube dispersion, wherein the dispersion comprises metal type single-wall carbon nanotubes, semiconductor type single-wall carbon nanotubes and carbon nanotubes with different length-diameter ratios; b) Providing ammonium salt functionalized silica microspheres, wherein the silica microspheres are obtained by performing aminosilane functionalization and acidification treatment on the silica microspheres, and the surfaces of the silica microspheres are functionalized with ammonium salt groups; c) Contacting the carbon nanotube dispersion with the ammonium salt functionalized silica microsphere to selectively adsorb the metallic single-walled carbon nanotubes and short semiconducting carbon nanotubes, which are carbon nanotubes having an average length of less than 0.5 μm, to the surface of the ammonium salt functionalized silica microsphere, and D) And separating the ammonium salt functionalized silica microspheres and the adsorbed carbon nanotubes from the remaining carbon nanotube dispersion, thereby obtaining a dispersion enriched with long semiconductor-type carbon nanotubes.
2. 2. The method of claim 1, wherein the ammonium salt functionalized silica microspheres comprise a silica core and ammonium salt groups covalently attached to the surface of the silica core.
3. 3. The method of claim 2, wherein the ammonium salt functionalized silica microspheres are formed by: S1, dispersing silicon oxide microspheres in a mixed solution of aminosilane and toluene for reaction, grafting amino groups on the surfaces of the silicon oxide microspheres, and obtaining amino-functionalized silicon oxide microspheres after solid-liquid separation and drying; s2, placing the amino functionalized silica microspheres in an acid solution for surface modification to convert the amino groups on the surface into ammonium salt groups, and obtaining the ammonium salt functionalized silica microspheres after solid-liquid separation and drying.
4. 4. A method according to claim 3, wherein the aminosilane is N- (2-aminoethyl) -3-aminopropyl trimethoxysilane.
5. 5. A method according to claim 3, wherein in step S1 the silica microspheres have a particle size of 100 μm to 150 μm, preferably the silica microspheres have a particle size of 115 μm.
6. 6. The method according to claim 3, wherein the silica microspheres are placed in a mixture of aminosilane and toluene at a concentration of 10mM, magnetically stirred for 2 hours at 60℃and 750 rpm, then centrifugally separated and vacuum dried at 120℃for 30 minutes.
7. 7. The method according to claim 3, wherein the specific process of step S2 is that the dried amino-functionalized silica microspheres are placed in a dilute hydrochloric acid solution with a concentration of 3% for reaction for 2 hours, are subjected to solid-liquid separation by centrifugation, are subjected to solvent displacement by isopropanol, are subjected to solid-liquid separation again by centrifugation, and are dried under vacuum at 120 ℃.
8. 8. The method of claim 1, wherein the separating the ammonium salt functionalized silica microspheres and adsorbed carbon nanotubes from the remaining carbon nanotube dispersion is performed by a static adsorption method or a column filtration method.
9. 9. The method according to claim 8, wherein the static adsorption method comprises adding 0.4g of silica microspheres to 3mL of the carbon nanotube solution, standing for adsorption for 48 hours to dynamic balance, and separating the supernatant by centrifugation.
10. 10. The method according to claim 8, wherein the column filtration method is to fill the ammonium salt functionalized silica microspheres into a column, inject a carbon nanotube solution into the column for filtration, and collect an effluent.

Description

Carbon nano tube specific separation method using ammonium salt functionalized silicon oxide microsphere Technical Field The invention belongs to the technical field of carbon nanotube purification, and particularly relates to a carbon nanotube specific separation method utilizing ammonium salt functionalized silica microspheres. Background Single-walled carbon nanotubes (SWNTs) are a typical class of one-dimensional nanomaterials with anisotropic and quasi-one-dimensional ballistic transport properties. Due to the extremely small pipe diameter and the excellent energy band structure, SWNTs can realize weak scattering transmission, high carrier mobility and long free path under proper conditions, and can effectively inhibit short channel effect under the condition of short channel length. These characteristics make SWNTs widely recognized as potential channel materials for new generation high performance field effect transistors, flexible electronics, and other carbon-based electronics. From the energy band structure, SWNTs can be classified into metallic type single-walled carbon nanotubes (METALLIC SWNT, m-SWNTs) and semiconducting type single-walled carbon nanotubes (semiconducting SWNT, s-SWNTs) according to the chirality and diameter. In switching devices such as field effect transistors, s-SWNTs mainly play a role in channel conduction, while a small amount of residual m-SWNTs can provide leakage paths in an off state, which results in an increase in off-state current and a decrease in the switching ratio (I on/Ioff) of the device, and seriously affects subthreshold characteristics and circuit-level integration reliability of the device. Therefore, to take advantage of the performance of SWNTs in logic and analog circuits, it is highly desirable to obtain s-SWNTs that have extremely low metallic content and extremely high semiconductor purity. In addition to purity of the electrical type, the length distribution of SWNTs is also an important factor affecting device performance. For single or few SWNT channel devices that require crossing source-drain electrodes, too short an s-SWNT tends to be difficult to effectively bridge the electrodes, or a conductive path needs to be formed in series through multiple short tubes, with the result that channel resistance increases, effective mobility decreases, device transconductance (G m), on-state current (I on), and noise level are adversely affected. For thin film devices that rely on network conduction, if the ratio of long tubes in the network is low, a higher areal density is required to form the through-paths, again introducing additional scattering and device uniformity issues. Therefore, in practical applications, it is desirable not only to effectively remove m-SWNTs and increase the electrical purity of s-SWNTs, but also to preserve and enrich long tubes as much as possible to compromise conductivity and device controllability. In response to the above-mentioned needs, a variety of SWNT purification and separation techniques have been proposed in the academia and industry. For example, density gradient ultracentrifugation (DENSITY GRADIENT ultracentrifugation, DGU), electrophoretic separation, aqueous two-phase partition (ATPE), gel permeation chromatography, selective separation methods based on surfactant or conjugated polymer coating, and the like. These methods typically utilize differences in the density, charged state, hydrophilicity and hydrophobicity of SWNTs of different chiralities/diameters or interactions with the functionalizing medium to effect separation of m-SWNTs from s-SWNTs. However, the existing method generally has the problems of complex flow, high dependence on expensive equipment such as ultra-high speed centrifugation, narrow parameter window, difficult large-scale amplification and the like. By taking DGU as an example, an accurate density gradient system needs to be configured and operated for a long time under the ultra-high speed centrifugation condition, while partial gel permeation chromatography or an aqueous phase two-phase system needs to finely adjust the formula and the temperature, and the process reproducibility is greatly influenced by the operation condition. On the other hand, many prior art separation techniques do not provide for optimal retention of SWNT length while achieving electrical type purification. In order to obtain better dispersion stability, strong ultrasonic treatment or repeated high-intensity centrifugation is usually required, and the steps are easy to introduce cutting and defects, so that a long tube is damaged in a large amount, and a short tube is mainly used in the final product. Even though this problem can be alleviated to some extent by adjusting the ultrasonic power, treatment time or dispersant type, there is often a tradeoff between separation efficiency, semiconductor purity and average length, which makes it difficult to combine both the high purity s-SWNTs and long tube enrichme