Carbon nanotubes (CNTs) have been attracting lots of attention from various fields of science and technology because of their extraordinary physical and chemical performances owing to their intrinsic nano-sized and one-dimensional nature. The most common process to synthesize carbon nanotubes is CCVD(Catalytic Chemical Vapor Deposition) method, because this technique is very powerful for large scale production and controlling the nanostructure. The CCVD method uses most commonly the nano-sized iron particles that are either dispersed on the substrate or floating reactant technique [1]. By using CCVD process, single, double and multi wall CNTs have been successfully grown, and based on the characteristic structure of CNTs various kinds of applications have been proposed and developed.

We are facing many environmental problems such as global warming and pollution, constant shortage of water and processing of agricultural wastes, etc. Therefore, finding measures for the resolution of such urgent issues is required. In this account, since we believe that CNTs and other nanocarbons have the ideal properties to solve such problems, some applications aiming toward resolving the environmental issues will be introduced.

At first, the current usage of CNTs in energy storage devices as one of the important component of high performance lithium ion secondary batteries is shown. Mainly, the effectiveness of the addition of CNTs to both cathode and anode electrode materials of lithium ion secondary batteries will be demonstrated[1].

The usage of CNTs as multi-functional filler in polymeric composites such as functional rubber[2], water desalination membranes [3] will be summarized. The water desalination and purification using reverse osmosis (RO) membrane prepared from polyamide/CNT nanocomposite is very promissing. We have successfully developed a high-concentration CNT dispersion method which was applied to the formation of PA/CNT RO membrane by interfacial polymerization. PA/CNT RO membrane has superior anti-fouling characteristics and high chroline resistance [3]. Desalination property and the science behind the high-performance PA/CNT RO membrane will be discussed.

For successful developments of CNT’s, the CNT’s safety is the most important issue [4,5,6]. By openly sharing all the information on toxicity risks and benefits of the carbon nanomaterials including CNTs with all the stakeholders, and by the responsible productions and uses through the designing safer nanostructure based on accumulated CNTs science and technology, CNTs can contribute to the sustainability of the 21^st century.

References

[1] M. Endo, Japanese Journal of Applied Physics 51, 040001(2012).

[2] M. Endo et al., Adv. Func. Mat. 18, 3403 (2008).

[3] S. Inukai , R. Cruz-Silva, J. Ortiz-Medina, A. Morelos-Gomez, K. Takeuchi, T. Hayashi, A. Tanioka, T. Araki, S. Tejima, T. Noguchi, M. Terrones, M. Endo, Scientific Reports 5, Article number:13562 (2015).

[4] A. Takagi, A. Hirose, T. Nishimura, N. Fukumori, A. Ogata, N. Ohashi, S. Kitajima, and J. Kanno: J. Toxicol. Sci. 33, 105 (2008).

[5] C. A. Poland, R. Duffin, I. Kinloch, A. Maynard, W. A. H. Wallace, A. Seaton, V. Stone, S. Brown, W. Macnee, K. Donaldson, Nature Nanotechnology 3, 423(2008).

[6] International Agency for Research on Cancer. Volume 111: Fluoro-edenite, silicon carbide fibres and whiskers, and single-walled and multi-walled carbon nanotubes IARC Working Group. Lyon; 30 Sep–7 Oct 2014.