Open-ended SWCNTs

Owens and Iqbal [146] succeeded in an electrochemical hydrogenation of open-ended SWCNTs synthesized by CVD. Sheets of SWCNT bucky paper were used as the negative electrode in an electrochemical cell containing aqueous KOH solution as electrolyte. The authors claimed to have incorporated up to 6 wt. % of hydrogen into the tubes, determined by laser Raman IR spectroscopy and hydrogen release by thermolysis at 135 °C under TGA conditions [146], However, the stability of exohydrogenated carbon nanotubes and the low temperature of hydrogen release at 135 °C [146] is contradictory with the 400-500 °C reported elsewhere [79a, 145],... 

We have performed simulations of the thermally activated self-capping process of carbon-only (CUT) and edge-oxidized (OX) models of open-ended SWCNTs, using quantum chemical molecular dynamics (QM/MD) simulations. We observed the following important features in trajectories up to 150 picoseconds ... 

Most of the experimental work on fluorination has been performed using elemental fluorine diluted in an inert gas at elevated temperatures [28, 30, 31], Comparative fluorination of open- and closed-end SWCNTs was performed with ele-... 

Carboxylic groups positioned at the open ends of SWCNTs were coupled to amines to form AFM probes with basic or hydrophobic functionalities by Wong et al. [117] (Scheme 1.8). Force titrations recorded between the ends of the SWCNT-AFM tips and hydroxy-terminated SAMs confirmed the chemical sensitivity and robustness of the AFM tips. Images recorded on patterned SAM allowed real molecular-resolution imaging [117]. 

In 2003, Lim et al. [142] succeeded in a direct thiolation of the open ends of SWCNTs via successive carboxylation (H2S04-HN03 H202-H2S04 sonication), NaBH4 reduction, chlorination with SOCl2 and thiolation (Na2S-NaOH) (Scheme 1.12). The intermediates and the final products were verified by FT-IR and NMR spectroscopy [142]. 

Encapsulation of Metal Complexes The nanostructure of CNTs (typical diameters range from 0.7 to 2.0 mn for SWCNTs) enables the endohedral encapsulation of molecules [14,15,21,31b,38]. It is possible to encapsulate molecules inside the tubes as long as the size of the molecules is smaller than the nanotubes and have enough kinetic energy to enter the open ends of CNTs. Practically, all organic solvents have a surface tension that makes possible the insertion of molecnles into the CNT internal diameters. 

In another study involving porphyrins, acid-oxidized SWCNTs bearing carboxyl groups at the open ends and defect sites were made to react with thionyl chloride and then with aminoporphyrins to yield multiporphyrin-linked SWCNTs... 

Water in well-characterized pores is a system of general interest because it serves as model system for the non-bulk or inhomogeneous water that is ubiquitous in biological and geological systems, as well as in nano-sfructured materials. Often confined or interfacial water is highly relevant to the properties and functions of entire systems, e.g., those in ion channels and clay minerals. X-ray diffraction studies show that water can fill the inner space of open-ended single-walled carbon nanotubes (SWCNTs) under ambient conditions and freezes into crystalline solids. These are often referred to as ice nanotubes . Ice stmctures in confined systems are characterized as stacked n-membered rings or equivalently as a rolled square-net sheet. The formation of the ice nanotubes in CNTs has also been observed by NMR, neutron diffraction, and vibrational spectroscopy studies. 

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