| 研究実績の概要 |
Carbon nanotubes has potential application for high performance electronic devices. However, highly pure semiconducting and micrometer-long single-wall carbon nanotubes (SWCNTs) are essential for the electronic application. Therefore, separation process such as gel filtration is required to obtain semiconducting SWCNTs (s-SWCNTs) from its mixture with metallic SWCNTs (m-SWCNTs).
In conventional gel filtration, 2 surfactant solution are used for the elution process: first, sodium dodecyl sulfate (SDS) solution for selectively eluting m-SWCNTs while allowing s-SWCNTs to be adsorbed in the gel; second, sodium cholate (SC) solution for elute the adsorbed s-SWCNTs. However, in this SDS-SC exchange elution system, minor amount of m-SWCNTs are not eluted in the first SDS elution. Hence, this remaining m-SWCNTs impurities are eluted simultaneously with s-SWCNTs during SC elution, reducing the overall purity of s-SWCNTs.
Here, we introduce new elution method called Automatic Gradient Elution (AGE) system for the gel filtration to improve the purity of the separated s-SWCNTs. Instead of separated elution of SDS and SC solution, a gradually changing mixture of SDS and SC solution are used as eluent in this AGE system. Utilization of AGE system allow the remaining m-SWCNTs, which are not eluted during the high SDS concentration eluent, to be eluted selectively at lower SC concentration than the s-SWCNTs. As compared to the conventional elution method, the m-SWCNTs impurity are reduced to less than half amount, remarking the significant improvement s-SWCNTs purity by this AGE method.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
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理由
As described in the proposal, the purpose of our work is to obtain semiconducting single-wall carbon nanotubes (s-SWCNTs) which has high performance characteristic for electronic devices application such as high purity and ultra-long s-SWCNTs. As we also aim to evaluate the s-SWCNTs for electronic devices application, the present work can be described in 3 main goals: 1) obtaining high purity s-SWCNTs, 2) obtaining physically proper (ultra-long, large diameter, defectless) s-SWCNTs, and 3) fabricating electronic device of s-SWCNTs. As the 3 goals are allocated to be done in 3 years, we expect to attain each goal in each year of the research project.
In this first year of our project, we have developed an improvised elution method for the gel filtration of s-SWCNTs called as Automatic Gradient Elution (AGE) system. Compared to the conventional method, our AGE system can reduced the amount metallic impurities, thus significantly improves the purity of s-SWCNTs in single-run gel filtration. This achievement of improving the purity of s-SWCNTs remarks that we have attain our first goal in our first year of the project. Therefore, we can say that our progress goes well as we have expected.
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| 今後の研究の推進方策 |
To obtain high performance electronic devices based on semiconducting single wall carbon nanotubes (s-SWCNTs), not only high purity sample, but also physically proper (ultra-long, large diameter, defectless) s-SWCNTs are required. As we have successfully improved the purity of s-SWCNTs, we are now looking forward to obtain s-SWCNTs with the best structure for electronic devices.
As carbon nanotubes structures are defined during the synthesis process, obtaining physically proper s-SWCNTs for electronic devices requires sorting of various carbon nanotubes grown by different synthesis method. Instead of the usual arc-discharge grown SWCNTs (SO, purchased from Meijo Nano Carbon), we will also sort s-SWCNTs from commercially available chemical vapor deposition (CVD) -grown SWCNTs such as KH, HiPco, eDIPS, etc. By sorting various grown SWCNTs, we can obtained various s-SWCNTs which characteristic may best suited for various electronic devices, e.g. large diameter SWCNTs for high mobility devices.
In addition to sorting different type SWCNTs, utilization of mild condition for SWCNTs dispersion will be focus to maintain the length of SWCNTs. For this purpose, at least 2 approaches can be used: 1) bath sonication method with short time as possible, or 2) shear mixing method, with the cost of time-consuming process.
In the end, we will also measure the electronic device characterization of the separated s-SWCNTs. For devices measurement, we can use short-channel field effect transistor for single s-SWCNTs devices or thin film transistor for longer channel devices.
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