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AQUEOUS SOLUTION FOR STRUCTURAL SEPARATION OF CARBON NANOTUBES, METHOD FOR SEPARATING AND RECOVERING CARBON NANOTUBES WITH USE OF SAID AQUEOUS SOLUTION, AND CARBON NANOTUBES OBTAINED BY SAID METHOD 新技術説明会

外国特許コード F200010160
掲載日 2020年6月3日
出願国 世界知的所有権機関(WIPO)
国際出願番号 2019JP029149
国際公開番号 WO 2020022414
国際出願日 令和元年7月25日(2019.7.25)
国際公開日 令和2年1月30日(2020.1.30)
優先権データ
  • 特願2018-141827 (2018.7.27) JP
発明の名称 (英語) AQUEOUS SOLUTION FOR STRUCTURAL SEPARATION OF CARBON NANOTUBES, METHOD FOR SEPARATING AND RECOVERING CARBON NANOTUBES WITH USE OF SAID AQUEOUS SOLUTION, AND CARBON NANOTUBES OBTAINED BY SAID METHOD 新技術説明会
発明の概要(英語) The purpose of the present invention is to provide: an aqueous solution for structural separation, which is capable of separating carbon nanotubes (CNT) having a specific structure with high accuracy by acting on CNT; a separation/recovery method which is capable of separating CNT having a specific structure with high accuracy by causing this aqueous solution to act thereon; and CNT which are obtained by this separation/recovery method. The present invention made it possible to separate CNT having a specific structure with high accuracy by solubilizing lithocholic acid or a lithocholic acid isomer, which is highly hydrophobic and is not soluble in water by itself, and using an aqueous solution that contains this solubilized lithocholic acid or this solubilized lithocholic acid isomer as an aqueous solution for structural separation of CNT.
従来技術、競合技術の概要(英語) BACKGROUND ART
(CNT) is the optical characteristics of the single-walled carbon nanotubes and a conductive characteristic, it is excellent in mechanical strength, ultimate of research and development as a new material has been actively researched. CNT carbon atoms arranged in hexagonal structure of graphene sheet is rolled and seamlessly, the rounding direction (diameter) and thickness (chiral angle) and the structure is defined. CNT is, a laser evaporation method, an arc discharge method, a chemical vapor deposition method (CVD method) and the like are combined in a variety of ways. In the present state may be any synthetic method, only completely the same structure cannot be combined, and the mixture having a variety of different configurations. CNT is different depending on the structure by electrical properties, and also the size of the semiconductor metal, of the semiconductor band gap is different even CNT has a different structure. For the electronics of the CNT, a homogeneous electrical properties can be obtained, and to separation of the metal-semiconductor type CNT, CNT of the separation of the single structure, to realize a next generation electronics important issues have been studied actively.
(N, m) of the CNT structure 2 is referred to as a set of two integers are uniquely defined by the chiral indices (n≧m). CNT is a CNT-metal-type semiconductor, separated from the CNT and its electrical properties, metal type CNT is, the difference (n-m) of chiral index is a multiple of 3 and, semiconductor-CNT is, (n-m) is defined as being not a multiple of 3 (Non-Patent Document 1). The parameters of the structure of the CNT can be obtained by using the chiral index, d is the diameter of the typical parameters d=a {(n2+m2+ nm) 2 January / π, chiral angle θ is tan θ= (3) 1/2m/ (2n+m) in approximation can be obtained. Here, the length of the hexagonal lattice of a graphene (0.249nm, CNT carbon atoms (0.144nm) of √3 times the distance between) (Non-Patent Document 1) in.
Separating the single CNT structure of several studies and it is, a plurality of single structure can be separated into a high purity CNT method is limited. CNT is an expensive material and, in many cases several tens of different types of structure is contained. Single structure contained therein can be separated without loss of the high purity CNT method, production on an industrial scale in a single structure of the CNT is not only important, the application of a mixture of existing CNT is totally different from the expected to lead to new applications. However, this isolation method is superior to does not exist, a new method has been strongly desired.
Reported to this structure of the separation method of a single CNT, the CNT may be any industrial productivity in a single structure containing the problem. Problem can be summarized as follows. (1) Type of high purity can be separated into a single structure is limited by the amount of recovered low per raw materials, (2) require expensive equipment or chemicals can be separated, (3) a large amount does not take a long time, (4) since a complicated processes, (5) automation cannot be separated, and the like.
The specific structure of the CNT composite DNA binding, ion exchange chromatography or an aqueous two-phase separation with a specific structure is extracted by the CNT (non-patent document 2, 3). However, the structure of the base sequence is extracted for each different CNT expensive synthetic DNA needs to be provided separately, there is a problem in costs and mass separation. Further, 1 types of residue can be extracted a single CNT structure cannot be longer available, only 1 CNT 1 from the raw material type cannot be extracted, a problem that the recovery amount is low.
Coupled to the specific structure of the polymer synthesized CNT, the molecule may be used to disperse the CNT, CNT having a chiral angle of a specific extract (non-patent document 4) a method. However, likewise, requires a special synthesis of a polymer, a problem that production costs and mass separation. Can be separated from the chiral structure and a large angle of view is limited to CNT, and further a problem such as low purity.
Be used as the above-described isolation method is a special, high cost and large amounts are difficult to separate any problem is not solved. In addition, strongly bound to remove the dispersing agent is also a problem that operations become necessary. On the other hand, inexpensive and commercially available as a dispersing agent, a surfactant is a separation method using, as a technique for solving the aforementioned problems has attracted attention. More specifically, density gradient ultracentrifugation, an aqueous two-phase separation method, such as chromatography. These separation method as a dispersant, a straight chain structure (SDS) with sodium dodecyl sulfate, sodium cholate having a steroid skeleton (SC) and sodium deoxycholate (DOC) or the like, a surfactant is used in common (non-patent document 5). In addition, all of the method, also plays a role for the surfactants are common, the electrical characteristics of the CNT in the SDS, due to a difference in band gap separation, and in which the diameter of the CNT are mixed DOC SC, are separated by the difference of the chiral angle (non-patent document 5). In recent years, such surface-active agent (or less, selectivity) of the different roles in order to use, different types of surface-active agent used and studies have been conducted, without using a special dispersing agent of the high purity CNT structure of a single successful separation of the (non-patent document 6, 7, 8). However, even in the case of these separation methods, as described below, are still remain some problems.
CNT coated with a surfactant by using density gradient ultracentrifugation separation, a method for recovering a specific structure of the CNT (non-patent document 6, 7) is. In this method the ultracentrifuge for expensive equipment that requires high cost occupied for a long time, a single separation takes a long time does not increase throughput, there is a limit in the size of the ultracentrifuge separation is difficult because a large, a problem that it is difficult to automate.
CNT is coated with a surfactant solution containing two different type of polymer is formed and separated using an aqueous two-phase separation method, a method for recovering a specific structure of the CNT (non-patent document 8) is. In this method, high purity can be separated and the type of CNT is limited, the recovery amount is also low which is problematic. In addition, high purity CNT depending on the raw material in order to separate the single structure, a complicated step is required, the automated problem difficult.
The inventors of the present invention, a novel method of the prior art structure is different from a single CNT undertaken separation method, the CNT coated with a surfactant, the gel and the gel is separated using the invention (Patent Document 1). The invention is, in the SDS gel coated CNT by the action of an excessive amount, the semiconductor structure only a single particular selectively adsorbed to the CNT can be a gel, the separation, in that recovery. In this method, an inexpensive equipment can be separated has the advantage that, in order to separate good reproducibility the amount of CNT gel injected into the gel ratio of the amount of constant has the disadvantage that it needs.
The inventors of the present invention further, in the technique described in Patent Document 1 is used instead of the aqueous solution of SDS, and SC to the SDS surfactant aqueous solution mixed with the DOC is used, it can be separated into a high purity CNT having a specific structure is not a new developed gel separation (non-patent document 9). In this method, first, the ratio of SDS/SC prepared in the concentration and mixing the CNT coated with a surfactant by the action of the gel, having a chiral angle of a particular semiconductor-type CNT is selectively adsorbed on the gel. Then, to which SDS/SC ratio and the concentration of the DOC was added to the mixture while maintaining a SDS/SC/DOC aqueous solution of surfactant by, a single structure having a particular diameter of the CNT was eluted with the semiconductor, separation, recovery. According to the procedure, the adsorption step and the chiral angle to select the diameter of the elution steps can be performed in one separation, the two chiral angle and diameter determined by the parameter CNT structure can be separated with high accuracy. In fact, this method to all of high purity cannot be separated (9, 4) (10, 3) and a single successful separation of the CNT structure. This technique is, as shown in Patent Document 1 and the ratio of the amount of CNT gel is not constant with good reproducibility as well as the separation becomes possible, high purity, a short, inexpensive equipment, throughput, and a method capable of automatic processing, a single CNT structure of the industrial productivity is very excellent.
However, the method described above, (9, 4) (10, 3) with respect to the type and p-type, high-purity of a single CNT structure can be created but the separation method, separation of the single structure of the structure of the other CNT was not achieved. One of the reasons for this, an aqueous surfactant mixture used in the elution step SDS/SC/DOC the selected diameter of the incomplete and the like. That is, SDS/SC/DOC DOC concentration of surfactant in the aqueous solution mixture is made higher, 1nm CNT having a diameter smaller than 1nm and the same CNT having a diameter larger than the concentration of eluted, each of the low purity. (9, 4) And (10, 3) are just the diameter of the intermediate diameter of about 1nm of the magnitude respectively. Therefore, 1nm CNT having a diameter smaller than 1nm and having a larger diameter than the CNT after elution from the column, the column can be separated as the remaining CNT. However, (9, 4) and (10, 3) with a large diameter or a smaller diameter than a single high purity CNT structure is separate, but elution of both, either one of them can be separated from the specialized elution is desirable that the surfactant.
Therefore, the inventors of the present invention, such a surfactant is searched for. Non-Patent Document 9 of the above separation method, the concentration of SDS and SC does not change the adsorption step and for the elution step, the elution step is added to the CNT contributes to dissolution of the DOC is considered. Instead of this DOC to search for the surfactant, the surfactant added to the elution step, is replaced with a less hydrophobic than DOC SC and a control experiment, the elution step is added to the surfactant having a hydrophobic steroid elution of the CNT is found that an important role (non-patent document 10). That is, SC and DOC in either case, the elution of the CNT having a diameter smaller than 1nm and 1nm CNT having a diameter larger than that of the elution is confirmed, the accuracy of the diameter of the separation, the less hydrophobic SC and high hydrophobicity greatly different from the DOC, the DOC of the high hydrophobicity of the peak of the few kinds of high purity CNT is obtained. Further, the different hydrophobic and easily eluted in the DOC SC CNT is also different, the less hydrophobic SC CNT having a diameter larger than 1nm is easily eluted, having high hydrophobicity is DOC CNT having a diameter of less than 1nm is more likely to eluted.
  • 出願人(英語)
  • ※2012年7月以前掲載分については米国以外のすべての指定国
  • NATIONAL INSTITUTE OF ADVANCED INDUSTRIAL SCIENCE AND TECHNOLOGY
  • 発明者(英語)
  • TANAKA TAKESHI
  • YOMOGIDA YOHEI
  • KATAURA HIROMICHI
国際特許分類(IPC)
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