In this critical review we survey non-covalent interactions of carbon nanotubes with molecular species from a chemical perspective, particularly emphasising the relationship between the structure and dynamics of these structures and their functional properties. We demonstrate the synergistic character of the nanotube-molecule interactions, as molecules that affect nanotube properties are also altered by the presence of the nanotube. The diversity of mechanisms of molecule-nanotube interactions and the range of experimental techniques employed for their characterisation are illustrated by examples from recent reports. Some practical applications for carbon nanotubes involved in non-covalent interactions with molecules are discussed.

This Account focuses on structural and dynamic behavior of molecules encapsulated in carbon nanotubes. The impact of the confinement on the molecular packing, orientation, translation, rotation, and reactivity is demonstrated for a range of fullerene and nonfullerene molecules. These phenomena are described and analyzed using the current understanding of molecule-nanotube and intermolecular interactions.

We have assembled molecular arrays of C60 inside double-walled carbon nanotubes (DWNTs) with internal diameters of 11-26 A and directly observed the existence of different crystalline phases of C60 previously predicted theoretically. The structure of the encapsulated C60 crystal is defined by the internal diameter of the DWNT, as the molecules adjust their packing arrangement in order to maximize van der Waals interactions. We have also shown that fullerenes in C(60)@DWNT interact with the outer layer of DWNTs, as demonstrated by the efficient filling of DWNTs with internal diameters of less than 12 A.

Abstract. Molecular structures appear to be natural candidates for a quantum technology: individual atoms can support quantum superpositions for long periods, and such atoms can in principle be embedded in a permanent molecular scaffolding to form an array. This would be true nanotechnology, with dimensions of order of a nanometre. However, the challenges of realising such a vision are immense. One must identify a suitable elementary unit and demonstrate its merits for qubit storage and manipulation, including input / output. These units must then be formed into large arrays corresponding to an functional quantum architecture, including a mechanism for gate operations. Here we report our efforts, both experimental and theoretical, to create such a technology based on endohedral fullerenes or 'buckyballs'. We describe our successes with respect to these criteria, along with the obstacles we are currently facing and the questions that remain to be addressed.

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We report the application of SWNTs as templates for forming covalent polymeric chains from C(60)O reacting inside SWNTs; the resulting peapod polymer topology is different from the bulk polymer in that it is linear and unbranched.

Molecules assembled inside nanotubes to form 1D arrays exhibit functional properties different to the bulk crystal and have been proposed for many applications ranging from catalysis to quantum computing. We have discovered that single-walled carbon nanotubes can be efficiently filled with fullerenes in supercritical fluids at temperatures as low as 30-50 uC. Despite the low solubility of fullerenes in supercritical fluids, the nanotube filling was particularly effective in supercritical carbon dioxide producing C n @SWNT structures in 70% yield at 50 uC. This method was also applied for functionalized and endohedral fullerenes and allows insertion of thermally unstable molecules which would be impossible to insert in nanotubes using standard techniques. We discuss the advantages of using supercritical fluids as compared to conventional solvents and propose mechanisms for fullerene encapsulation at low temperatures.

Production and purification of iCeC 82Ce-containing endohedral fullerenes were produced by the so-called reversed arc technique developed by the Nagoya group as described previously. 1 A Ce-doped graphite rod (anode) was kept a few mm apart from a graphite block (cathode) in a vacuum chamber. The rod and the block were connected to an external power supply and high current was passed through them (300 -500 A). The vaporisation took place in He atmosphere (50 -100 Torr). The resulting soot contained 10 -20 % fullerenes.The fullerenes were soxhlet-extracted from the soot for ca. 4 hours in o-xylene. A twostage high performance liquid chromatography (HPLC) method was employed to isolate individual fullerene isomers. In the first stage, the o-xylene solution was passed through a Cosmosil 5PBB column (20 250 mm, Nacalai Tesque) with o-xylene eluent (flow rate: 11 ml/min). Figure 1 shows the HPLC chromatogram of Ce-containing endohedral fullerenes.