JP5224515B2 - Dispersion method of carbon nanotube in aqueous medium - Google Patents
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 4
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- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
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- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
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- LDLCZOVUSADOIV-UHFFFAOYSA-N 2-bromoethanol Chemical compound OCCBr LDLCZOVUSADOIV-UHFFFAOYSA-N 0.000 description 1
- 241000283690 Bos taurus Species 0.000 description 1
- 108091003079 Bovine Serum Albumin Proteins 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical group [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 description 1
- 241000287828 Gallus gallus Species 0.000 description 1
- 239000004366 Glucose oxidase Substances 0.000 description 1
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- 239000003125 aqueous solvent Substances 0.000 description 1
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- Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)
- Colloid Chemistry (AREA)
- Carbon And Carbon Compounds (AREA)
Description
本発明は、水系媒体中へのカーボンナノチューブの効果的な分散方法に関する。 The present invention relates to an effective method for dispersing carbon nanotubes in an aqueous medium.
カーボンナノチューブは１９９１年の発見以来、機械的特性、熱特性、電気的特性などの点において非常に注目されてきた。しかしながら、カーボンナノチューブは水系媒体中に分散させようとしても凝集することがその応用への障壁となっていた。カーボンナノチューブの凝集の主因は、カーボンナノチューブ間の非共有結合であり、具体的にはファンデルワールス力、π−πスタッキング、疎水性相互作用などが挙げられる。カーボンナノチューブの特性は凝集することで著しく低下する。そのため、カーボンナノチューブを水系溶媒中に分散させる方法がこれまでにも各種提案されてきた。そのひとつとして、共有結合を利用してカーボンナノチューブを化学修飾する方法がある。しかしながら、共有結合を利用したカーボンナノチューブの化学修飾は、その特性を劣化させる原因になる。従って、水系媒体中にカーボンナノチューブを分散させる際には、共有結合を利用しない方法で行うことが望ましい。このような方法の代表例として、界面活性剤の存在下でカーボンナノチューブを分散させる方法が知られている。 Since its discovery in 1991, carbon nanotubes have received much attention in terms of mechanical properties, thermal properties, electrical properties, and the like. However, even if carbon nanotubes are dispersed in an aqueous medium, aggregation has been a barrier to their application. The main cause of carbon nanotube aggregation is non-covalent bonding between carbon nanotubes, and specific examples include van der Waals force, π-π stacking, and hydrophobic interaction. The properties of carbon nanotubes are significantly degraded by aggregation. Therefore, various methods for dispersing carbon nanotubes in an aqueous solvent have been proposed so far. One of them is a method of chemically modifying carbon nanotubes using a covalent bond. However, chemical modification of carbon nanotubes using a covalent bond causes deterioration of its properties. Therefore, it is desirable to disperse carbon nanotubes in an aqueous medium by a method that does not use covalent bonds. As a typical example of such a method, a method of dispersing carbon nanotubes in the presence of a surfactant is known.
近年、バイオマテリアルやドラッグデリバリーシステムなどにおけるカーボンナノチューブの利用が注目されてきており、このような分野での利用に向けて、水系媒体中へのカーボンナノチューブの分散方法として、生体分子を用いた方法が着目され、特許文献１では生体分子として卵白タンパク質を用いる方法が提案されている。このようなタンパク質を用いた方法は、バイオセンサーなどのバイオマテリアルにカーボンナノチューブを利用する際に有効であることが期待される。しかしながら、カーボンナノチューブ間の相互作用は強く、そのためタンパク質を用いただけでは、当該相互作用を十分に弱めることができず、その結果として、水系媒体中に分散させることができるカーボンナノチューブの量には限界があることが本発明者らの研究により明らかとなった。
そこで本発明は、タンパク質を用いた水系媒体中へのカーボンナノチューブの分散方法において、カーボンナノチューブの分散量を高める方法を提供することを目的とする。 Accordingly, an object of the present invention is to provide a method for increasing the amount of carbon nanotube dispersion in a method for dispersing carbon nanotubes in an aqueous medium using protein.
本発明者らは上記の点に鑑みて鋭意研究を重ねた結果、タンパク質を用いて水系媒体中にカーボンナノチューブを分散させる際、系中にアルコールを存在させることで、カーボンナノチューブの分散量を容易に高めることができることを知見した。 As a result of intensive studies in view of the above points, the present inventors have made it easy to disperse carbon nanotubes by disposing alcohol in the system when carbon nanotubes are dispersed in an aqueous medium using proteins. It has been found that it can be increased.
上記の知見に基づいてなされた本発明の水系媒体中へのカーボンナノチューブの分散方法は、請求項１記載の通り、タンパク質とハロゲン原子を含むアルコールの存在下でカーボンナノチューブを分散させることを特徴とする。
また、請求項２記載の方法は、請求項１記載の方法において、タンパク質の濃度を０．０１ｍｇ／ｍＬ〜１０ｍｇ／ｍＬとすることを特徴とする。
また、請求項３記載の方法は、請求項１記載の方法において、アルコールの濃度を１０ｍＭ〜５００ｍＭとすることを特徴とする。
また、本発明のカーボンナノチューブ分散水系溶液の製造方法は、請求項４記載の通り、水系媒体中においてタンパク質とハロゲン原子を含むアルコールの存在下でカーボンナノチューブを分散させることを特徴とする。
また、本発明のカーボンナノチューブ分散水系溶液は、請求項５記載の通り、水系媒体中にカーボンナノチューブとともにタンパク質とハロゲン原子を含むアルコールを含んでなることを特徴とする。
The method for dispersing carbon nanotubes in the aqueous medium of the present invention based on the above knowledge is characterized in that, as described in claim 1, carbon nanotubes are dispersed in the presence of protein and an alcohol containing a halogen atom. To do.
A method according to claim 2 is characterized in that, in the method according to claim 1, the protein concentration is 0.01 mg / mL to 10 mg / mL.
The method according to claim 3 is characterized in that, in the method according to claim 1, the concentration of alcohol is 10 mM to 500 mM .
Also, the method of manufacturing the carbon nanotube dispersion aqueous solution of the present invention, as claimed in claim 4, wherein the dispersing carbon nanotubes in the presence of an alcohol containing protein and halogen atom in an aqueous medium.
Moreover, the carbon nanotube dispersion | distribution aqueous solution of this invention is characterized by including the alcohol containing protein and a halogen atom with a carbon nanotube in an aqueous medium as described in Claim 5 .
本発明によれば、水系媒体中へのカーボンナノチューブの効果的な分散方法が提供される。 According to the present invention, an effective method for dispersing carbon nanotubes in an aqueous medium is provided.
本発明の水系媒体中へのカーボンナノチューブの分散方法は、タンパク質とアルコールの存在下でカーボンナノチューブを分散させることを特徴とするものである。 The method for dispersing carbon nanotubes in an aqueous medium of the present invention is characterized in that carbon nanotubes are dispersed in the presence of protein and alcohol.
本発明の適用対象となるカーボンナノチューブは、主に炭素原子で構成される中空部材として当業者に認識されているものであればどのようなものであってもよく、具体的には単層カーボンナノチューブ（Ｓｉｎｇｌｅ−Ｗａｌｌｅｄ Ｃａｒｂｏｎ Ｎａｎｏｔｕｂｅｓ：ＳＷＮＴｓ）や多層カーボンナノチューブ（Ｍｕｌｔｉ−Ｗａｌｌｅｄ Ｃａｒｂｏｎ Ｎａｎｏｔｕｂｅｓ：ＭＷＮＴｓ）などが挙げられる。 The carbon nanotube to which the present invention is applied may be any carbon nanotube as long as it is recognized by those skilled in the art as a hollow member mainly composed of carbon atoms. Examples thereof include nanotubes (Single-Walled Carbon Nanotubes: SWNTs) and multi-walled carbon nanotubes (MWNTs).
本発明において用いることができるタンパク質としては、特許文献１に記載の卵白タンパク質（卵白リゾチーム）の他、例えばNepal et al. Small 2007 3: 1259-1265に記載のヒストン、ヘモグロビン、ミオグロビン、オボアルブミン、ウシ血清アルブミン、トリプシン、グルコースオキシダーゼや、ペプシンなどが挙げられる。タンパク質は単独で用いてもよいし、複数種類を混合して用いてもよい。系中におけるタンパク質の濃度は０．０１ｍｇ／ｍＬ〜１０ｍｇ／ｍＬが望ましく、０．１ｍｇ／ｍＬ〜５ｍｇ／ｍＬがより望ましい。濃度が低すぎるとカーボンナノチューブの分散量が少なくなってしまうといった恐れがある一方、濃度が高すぎると共存するアルコールによってその一部または全部が変性したり沈殿したりしてしまうといった恐れがある。 Examples of the protein that can be used in the present invention include egg white protein (egg white lysozyme) described in Patent Document 1, as well as histone, hemoglobin, myoglobin, ovalbumin described in Nepal et al. Small 2007 3: 1259-1265, Examples include bovine serum albumin, trypsin, glucose oxidase, and pepsin. A protein may be used independently and may be used in mixture of multiple types. The protein concentration in the system is preferably 0.01 mg / mL to 10 mg / mL, more preferably 0.1 mg / mL to 5 mg / mL. If the concentration is too low, the amount of carbon nanotube dispersion may be reduced. On the other hand, if the concentration is too high, part or all of the carbon nanotube may be denatured or precipitated by the coexisting alcohol.
本発明において用いることができるアルコールとしては、メタノール、エタノール、ｉｓｏ−プロパノール、ｎ−ブタノールなどの一般式：ＲＯＨ（Ｒは炭素数１〜１８の直鎖または分岐鎖のアルキル基である）で表されるアルコールが挙げられるが、望ましいアルコールとしては、水系媒体中におけるタンパク質のカーボンナノチューブの分散作用に対してより効果的に機能するハロゲン原子を含むアルコールが挙げられる。ハロゲン原子を含むアルコールとしては、例えば前出の一般式：ＲＯＨにおけるＲで表されるアルキル基の水素原子の一部または全部がフッ素原子、塩素原子、臭素原子などのハロゲン原子に置換されたアルコールが挙げられ、具体的には２，２，２−トリフルオロエタノール、１，１，１，３，３，３−ヘキサフルオロイソプロパノール、２−ブロモエタノール、１，３−ジクロロ−２−プロパノールなどが挙げられる。アルコールは単独で用いてもよいし、複数種類を混合して用いてもよい。系中におけるアルコールの濃度は１０ｍＭ〜５００ｍＭが望ましく、１５０ｍＭ〜３５０ｍＭがより望ましい。濃度が低すぎるとカーボンナノチューブの分散量を高める効果が発揮されないといった恐れがある一方、濃度が高すぎると共存するタンパク質の一部または全部を変性させたり沈殿させたりしてしまうといった恐れがある。 The alcohol that can be used in the present invention is represented by the general formula: ROH (R is a linear or branched alkyl group having 1 to 18 carbon atoms) such as methanol, ethanol, iso-propanol, and n-butanol. Desirable alcohols include alcohols containing halogen atoms that function more effectively with respect to the dispersing action of protein carbon nanotubes in an aqueous medium. Examples of the alcohol containing a halogen atom include alcohols in which a part or all of the hydrogen atoms of the alkyl group represented by R in the above general formula: ROH are substituted with halogen atoms such as fluorine atom, chlorine atom and bromine atom Specifically, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, 2-bromoethanol, 1,3-dichloro-2-propanol, etc. Can be mentioned. Alcohol may be used alone or in combination of two or more. The concentration of alcohol in the system is preferably 10 mM to 500 mM, more preferably 150 mM to 350 mM. If the concentration is too low, the effect of increasing the amount of carbon nanotube dispersion may not be exhibited. On the other hand, if the concentration is too high, some or all of the coexisting proteins may be denatured or precipitated.
本発明における水系媒体中へのカーボンナノチューブの分散は、例えば水系媒体中にタンパク質とアルコールを存在せしめた後、過剰量のカーボンナノチューブを添加し、５℃〜３５℃で１分間〜１時間超音波処理することで行うことができる。この際、必要に応じて、水系媒体のｐＨを、系中に存在せしめるタンパク質の等電点から少なくとも３以上離れるように酸またはアルカリを用いて調整することが望ましい。タンパク質の等電点付近のｐＨでは、タンパク質の表面電荷が小さいため、カーボンナノチューブの分散作用が低いからである。超音波処理を行った後、遠心分離を行えば、カーボンナノチューブ分散水系溶液をその上澄み液として得ることができる。こうして得られたカーボンナノチューブ分散水系溶液は、タンパク質と高度に分散したカーボンナノチューブを多量に含む複合材料として、バイオマテリアルやドラッグデリバリーシステムなどの分野において利用することができる。 The dispersion of the carbon nanotubes in the aqueous medium in the present invention is performed, for example, by allowing protein and alcohol to exist in the aqueous medium, adding an excessive amount of carbon nanotubes, and ultrasonicating at 5 ° C. to 35 ° C. for 1 minute to 1 hour. It can be done by processing. At this time, it is desirable to adjust the pH of the aqueous medium using an acid or an alkali so as to be at least 3 or more away from the isoelectric point of the protein existing in the system, if necessary. This is because, at a pH near the isoelectric point of the protein, the surface charge of the protein is small, and thus the carbon nanotube dispersion action is low. If the centrifugal treatment is performed after the ultrasonic treatment, a carbon nanotube-dispersed aqueous solution can be obtained as the supernatant. The carbon nanotube-dispersed aqueous solution thus obtained can be used as a composite material containing a large amount of protein and highly dispersed carbon nanotubes in fields such as biomaterials and drug delivery systems.
なお、本発明において、水系媒体とは、５０重量％〜１００重量％の水と０重量％〜５０重量％の水溶性有機溶媒とからなる媒体を意味する。水溶性有機溶媒としては、メタノールやエタノールなどのアルコールの他、アセトン、メチルエチルケトン、テトラヒドロフランなどが挙げられる。水系媒体としてアルコールを含む水を用いた場合、そこにタンパク質とカーボンナノチューブを添加することで、本発明を実施することができる。必要に応じて、水系媒体には緩衝剤や防腐剤などの添加剤が含まれていてもよい。 In the present invention, the aqueous medium means a medium comprising 50% by weight to 100% by weight of water and 0% by weight to 50% by weight of a water-soluble organic solvent. Examples of the water-soluble organic solvent include acetone, methyl ethyl ketone, tetrahydrofuran and the like in addition to alcohols such as methanol and ethanol. When water containing alcohol is used as the aqueous medium, the present invention can be carried out by adding protein and carbon nanotubes thereto. If necessary, the aqueous medium may contain additives such as buffering agents and preservatives.
以下、本発明を実施例によって詳細に説明するが、本発明は以下の記載に限定して解釈されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is limited to the following description and is not interpreted.
実施例：
（実験方法）
５０ｍＭのクエン酸・リン酸緩衝液、２５０ｍＭのアルコール、１．０ｍｇ／ｍＬのタンパク質を含有する１０ｍＬの溶液（ｐＨ３．４の溶液とｐＨ６．５の溶液の２種類）に、十分量の単層カーボンナノチューブ（Carbon Nanotechnologies社製）を添加し、ボルテックスミキサー（Vortex Genie 2, Scientific incustries社製）で攪拌した後、２０℃で１５分間超音波処理を行った（装置：UT-250S, Sharp社製）。その後、再び溶液をボルテックスミキサーで攪拌した後、再度、２０℃で１５分間超音波処理を行った。溶液を室温で１時間放置した後、２５℃で３０分間遠心分離（４０，０００ｇ）を行い（装置：SRX-201, TOMY社製）、その上澄み液のＶｉｓ−ＮＩＲ吸収スペクトルを測定することで（装置：UV-3150, SHIMADZU社製）、上澄み液中のカーボンナノチューブの分散量を評価した（ｎ＝３）。なお、この実験においては、アルコールとして、１，１，１，３，３，３−ヘキサフルオロイソプロパノール（ＨＦＩＰ）、２，２，２−トリフルオロエタノール（ＴＦＥ）、ｎ−ブタノール（ＢｕｔＯＨ）、エタノール（ＥｔＯＨ）、メタノール（ＭｅｔＯＨ）を用いた。また、タンパク質として、ペプシン（ブタ由来、ｐＩは約１）、ヘモグロビン（ウシ由来、ｐＩは約６．５）、卵白リゾチーム（ニワトリ由来、ｐＩは約１１）を用いた。また、比較対照として、アルコールを添加しないこと以外は上記と同様の実験を行った（ｎ＝３）。
（実験結果）
タンパク質としてペプシンを用いた場合、溶液のｐＨが３．４であるとカーボンナノチューブの分散が行えなかったが、溶液のｐＨが６．５では効果的に行うことができ、いずれのアルコールを添加した場合においても、アルコールを添加しない場合に比較して、カーボンナノチューブの分散量を大いに高めることができた（図１（Ａ）参照、吸光度は６００ｎｍ、“ｎｏ ａｄｄｉｔｉｖｅ”はアルコールを添加していない対照群（以下同じ））。一方、タンパク質としてヘモグロビンを用いた場合、溶液のｐＨが３．４ではカーボンナノチューブの分散を効果的に行うことができ、とりわけ２，２，２−トリフルオロエタノール、ｎ−ブタノール、エタノールを添加した場合において、アルコールを添加しない場合に比較して、カーボンナノチューブの分散量を大いに高めることができたが（図１（Ｂ）参照、吸光度は９００ｎｍ）、溶液のｐＨが６．５であるとカーボンナノチューブの分散が行えなかった。また、タンパク質として卵白リゾチームを用いた場合、溶液のｐＨが３．４ではカーボンナノチューブの分散を効果的に行うことができ、とりわけ１，１，１，３，３，３−ヘキサフルオロイソプロパノール、２，２，２−トリフルオロエタノールを添加した場合において、アルコールを添加しない場合に比較して、カーボンナノチューブの分散量を大いに高めることができたが（図１（Ｃ）参照、吸光度は６００ｎｍ）、溶液のｐＨが６．５であるとカーボンナノチューブの分散が行えなかった。以上の結果から、用いるタンパク質とアルコールの組み合わせを適宜選択し、タンパク質の等電点を考慮して溶液のｐＨを適切に調整することで、好適なタンパク質とアルコールの組み合わせと溶液のｐＨを設定することにより、タンパク質だけを用いる場合に比較して、水系媒体中へのカーボンナノチューブの分散量を大いに高めることができることがわかった。
Example:
(experimental method)
Sufficient monolayer in 10 mL solution (2 types, pH 3.4 solution and pH 6.5 solution) containing 50 mM citrate / phosphate buffer, 250 mM alcohol, 1.0 mg / mL protein Carbon nanotubes (Carbon Nanotechnologies) were added and stirred with a vortex mixer (Vortex Genie 2, Scientific incustries), followed by sonication at 20 ° C. for 15 minutes (apparatus: UT-250S, Sharp) ). Thereafter, the solution was again stirred with a vortex mixer, and then sonicated again at 20 ° C. for 15 minutes. The solution is allowed to stand at room temperature for 1 hour, and then centrifuged (40,000 g) at 25 ° C. for 30 minutes (apparatus: SRX-201, manufactured by TOMY), and the Vis-NIR absorption spectrum of the supernatant is measured. (Apparatus: UV-3150, manufactured by SHIMADZU), the amount of carbon nanotube dispersion in the supernatant was evaluated (n = 3). In this experiment, 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), 2,2,2-trifluoroethanol (TFE), n-butanol (ButOH), ethanol are used as alcohols. (EtOH) and methanol (MetOH) were used. Moreover, pepsin (derived from pig, pI is about 1), hemoglobin (derived from bovine, pI is about 6.5) and egg white lysozyme (derived from chicken, pI is about 11) were used as proteins. As a comparative control, an experiment similar to the above was performed except that no alcohol was added (n = 3).
(Experimental result)
When pepsin was used as the protein, the carbon nanotube could not be dispersed when the pH of the solution was 3.4, but it could be effectively performed when the pH of the solution was 6.5, and any alcohol was added. Even in the case where the alcohol was not added, the dispersion amount of the carbon nanotubes could be greatly increased (see FIG. 1 (A), the absorbance was 600 nm, and “no additive” was a control in which no alcohol was added). Group (hereinafter the same)). On the other hand, when hemoglobin is used as the protein, the carbon nanotubes can be dispersed effectively when the pH of the solution is 3.4. In particular, 2,2,2-trifluoroethanol, n-butanol and ethanol are added. In this case, compared with the case where no alcohol was added, the amount of carbon nanotubes dispersed could be greatly increased (see FIG. 1B, the absorbance was 900 nm), but when the pH of the solution was 6.5 Nanotubes could not be dispersed. Further, when egg white lysozyme is used as a protein, carbon nanotubes can be dispersed effectively when the pH of the solution is 3.4, particularly 1,1,1,3,3,3-hexafluoroisopropanol, 2 , 2,2-trifluoroethanol was added, the amount of carbon nanotube dispersion could be greatly increased compared to the case where no alcohol was added (see FIG. 1C, absorbance is 600 nm). When the pH of the solution was 6.5, carbon nanotubes could not be dispersed. Based on the above results, a suitable combination of protein and alcohol and the pH of the solution are set by appropriately selecting the protein and alcohol combination to be used and appropriately adjusting the pH of the solution in consideration of the isoelectric point of the protein. As a result, it was found that the amount of carbon nanotubes dispersed in the aqueous medium can be greatly increased as compared with the case where only protein is used.
参考例：
実施例１において得られた、タンパク質としてペプシンを用いた場合のｐＨが６．５のカーボンナノチューブ分散液、タンパク質としてヘモグロビンを用いた場合のｐＨが３．４のカーボンナノチューブ分散液、タンパク質として卵白リゾチームを用いた場合のｐＨが３．４のカーボンナノチューブ分散液のそれぞれに対し、塩酸または水酸化ナトリウムを添加することでそのｐＨを変化させた後、遠心分離（１８，０００ｇ）を行い、実施例と同様にして、その上澄み液のＶｉｓ−ＮＩＲ吸収スペクトルを測定することで、上澄み液中のカーボンナノチューブの分散量を評価した（ｎ＝１）。結果をそれぞれ図２（Ａ）〜（Ｃ）に示す。図２から明らかなように、用いたタンパク質の等電点付近ではカーボンナノチューブの分散量は少なく、等電点から離れるにつれて分散量が高まった。以上の結果から、用いるタンパク質とアルコールの組み合わせの適切な選択と、溶液のｐＨの変更により、水系媒体中においてカーボンナノチューブの分散制御が行えることがわかった。
Reference example:
Carbon nanotube dispersion with pH 6.5 when using pepsin as protein, carbon nanotube dispersion with pH 3.4 when using hemoglobin as protein, egg white lysozyme as protein, obtained in Example 1 When each of the carbon nanotube dispersion liquids having a pH of 3.4 was changed by adding hydrochloric acid or sodium hydroxide to each of the carbon nanotube dispersion liquids, centrifugation (18,000 g) was performed. In the same manner as described above, the dispersion amount of the carbon nanotubes in the supernatant was evaluated by measuring the Vis-NIR absorption spectrum of the supernatant (n = 1). The results are shown in FIGS. 2 (A) to (C), respectively. As is clear from FIG. 2, the amount of carbon nanotube dispersion was small near the isoelectric point of the protein used, and the amount of dispersion increased as the distance from the isoelectric point was increased. From the above results, it was found that the dispersion of carbon nanotubes can be controlled in an aqueous medium by appropriately selecting the combination of protein and alcohol to be used and changing the pH of the solution.
本発明は、水系媒体中へのカーボンナノチューブの効果的な分散方法を提供することができる点において産業上の利用可能性を有する。 The present invention has industrial applicability in that it can provide an effective method for dispersing carbon nanotubes in an aqueous medium.
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