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Pore characterization of assembly-structure controlled single wall carbon nanotube M. Arai · M. Kanamaru · T. Matsumura · Y. Hattori · S. Utsumi · T. Ohba · H. Tanaka · C.M. Yang · H. Kanoh · F. Okino · H. Touhara · K. Kaneko

Received: 11 June 2007 / Revised: 10 September 2007 / Accepted: 13 September 2007 / Published online: 3 October 2007 © Springer Science+Business Media, LLC 2007

Abstract Single wall carbon nanotube (SWCNT), which has bundle structure and entangled structure, was untangled and cut by sonication in hydrogen peroxide (H2 O2 ) solution. The untangled state of SWCNT was examined by SEM, TEM, Raman spectroscopy and N2 adsorption. It was confirmed that the surface area of sonicated nanotubes strongly depended on the sonication time. The BET specific surface area (SSA) of nanotubes sonicated for 3 h was maximum. The SSA decreased at 6 h or more of sonication time. These results indicated that the bundle structure was untangled and the cap of SWCNT was opened. Thus, N2 molecules can access the most efficiently inside of the SWCNT sonicated for 3 h. On the contrary, the sonication treatment for 6 h or more decomposed the nanotubes to produce amorphous carbon, evidenced by TEM and SEM observation; the amorphous carbon blocked the open pore sites such as the internal pore spaces and interstitial pores. Keywords Carbon nanotube · Nanopore characterization · Micropore filling · Raman spectroscopy · Molecular simulation Abbreviations E The change of energy in the system T Temperature (K)

M. Arai · M. Kanamaru · T. Matsumura · Y. Hattori · S. Utsumi · T. Ohba · H. Tanaka · C.M. Yang · H. Kanoh · K. Kaneko () Graduate School of Science, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8533, Japan e-mail: [email protected] F. Okino · H. Touhara Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda 386-8567, Japan

(r) Lennard-Jones potential energy r The distance between the center of particle i and particle j (Å) εij The particle i-particle j potential well depth σij The effective distance between the center of particle i and particle j (Å) kB Boltzmann constant (J/K) P /P0 Relative pressure

1 Introduction Single wall carbon nanotube (SWCNT) has gathered great attention in various fields of science and technology (Saito et al. 2000). Ordinary SWCNTs have bundle structures which are also entangled with each other (Hirsch 2002), although Hata et al. succeeded to prepare highly pure SWCNTs which are mutually isolated (Hata et al. 2004). The bundle structure provides interstitial nanopores of the very strong interaction potential for molecules and thereby the designated bundle structure is preferable for the application of SWCNT as an adsorbent, membrane filter, and gas sensor (Cao et al. 2003). If the geometry of the SWCNT bundle, such as the tubule length, bundle thickness and intertube distance can be controlled, the performance of SWCNT is highly improved. On the other hand, the entangled structure of SWCNTs have merits for application to fabricated films which are r