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We describe here the high yield filling (i.e. > 50%) of single walled nanotubes (SWNTs) with a variety of halides, achieved according to various modified filling procedures. Both bundles and discrete SWNTs can be filled continuously up to lengths of several hundred nm, often with filling yields approaching 60-70% or better. In addition some high yield filled SWNTs were subjected to long-term washing in either boiling or room temperature, aqueous media, which does not remove the filling from the tubules, but enables effective removal of water-soluble extraneous materials.

The complete crystallography of a one-dimensional crystal of potassium iodide encapsulated within a 1.6-nanometer-diameter single-walled carbon nanotube has been determined with high-resolution transmission electron microscopy. Individual atoms of potassium and iodine within the crystal were identified from a phase image that was reconstructed with a modified focal series restoration approach. The lattice spacings within the crystal are substantially different from those in bulk potassium iodide. This is attributed to the reduced coordination of the surface atoms of the crystal and the close proximity of the van der Waals surface of the confining nanotube.

Iodinated single-walled carbon nanotubes, with iodine covalently bound to the nanotube surface, have been synthesized by oxidation of the carbon nanotubes followed by a modified Hunsdiecker reaction using elemental iodine and iodosobenzene diacetate (IBDA). High-resolution transmission electron microscopy (HRTEM) images show small high-contrast spots which are stable to the electron beam and are assigned to iodine atoms bonded to the surface of the nanotube. Importantly, the electronic properties of the nanotubes were found to be largely intact after functionalization. The iodinated carbon nanotubes were fully characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, UV-vis-NIR spectroscopy, and thermogravimetric analysis-mass spectrometry (TGA-MS).

The formation of ‘all surface’ 4:4 co-ordinated KI crystals within 1.4 nm diameter single walled carbon nanotubes (SWNT) is reported. KI was inserted into the SWNTs by a capillary method [J. Sloan, D.M. Wright, H.G. Woo, S. Bailey, G. Brown, A.P.E. York, K.S. Coleman, J.L. Hutchison, M.L.H. Green, J. Chem. Soc. Chem. Commun. (1999) 699], whereby the nanotubes were combined intimately with the molten halide. The crystals grew withh 001 i (relative to bulk KI) parallel to the tubule axes and were continuous tetragonally distorted bilayer crystals composed of alternating columns of K‐I and I‐K pairs when viewed along h 100 i. ” 2000 Elsevier Science B.V. All rights reserved.

The relative size distributions of molecules of C60 and higher fullerenes observed in single walled carbon nanotubes (SWNTs) produced by arc vaporization of carbon in the presence of a mixed Ni/Y catalyst are described. The experimental and calculated imaging properties of the fullerenes, which were observed in ca. 5–10% of SWNTs, are also described. The in situ e-beam irradiation in a 300 kV field emission gun transmission electron microscope causes rapid coalescence of the fullerenes within the SWNTs. The incorporated fullerenes also directly impede crystal growth in SWNTs when their cavities are filled by the liquid phase capillary method.

Single-walled carbon nanotubes have been cyclopropanated under Bingel reaction conditions, and the functionalized nanotubes have been characterized by atomic force microscopy using "chemical tagging" techniques.

High-resolution transmission electron microscopy and spatially resolved electron loss spectroscopy have revealed that a eutectic mixture of AgCl and AgI crystallizes within single walled carbon nanotubes (SWNTs) as metastable AgCl(1-)(x)I(x) 1D solid solution crystals. The incorporated halide crystals form wurzite "tunnel" structures with locally varying Cl:I ratios and reduced Ag coordination.

Spatially resolved electron loss spectra (EELS) have been recorded for single walled carbon nanotubes (SWNTs) filled with metastable crystalline AgCl1−xIx. High resolution transmission electron microscopy (HRTEM) revealed that the incorporated halide crystals are derived from a 1D wurzite ‘tunnel’ structure with reduced Ag coordination with Cl and I randomly distributed over the halogen sites. High resolution EELS line scan profiles were used to probe the local composition of the nanocomposites and to distinguish between filled and unfilled tubules.

The encapsulation of halides and other materials within SWNTs makes possible the study of 1D crystal structures formed on the smallest scale possible. For example, we have shown that either 2×2 or 3×3 atomic layer thick KI crystals can be formed in SWNTs according to their diameter. Such crystals have reduced coordination (e.g. all the atoms in the 2×2 crystal are 4:4 coordinated) and exhibit lattice distortions compared to the corresponding bulk halide. With respect to more complex binary structures, such as 3D network, chain halides, layered halides, or complex 3D oxides, 1D crystals of these structures can be studied. The application of advanced HRTEM imaging techniques to these materials is also described.

The crystal growth behaviour and crystallography of a variety of metal halides incorporated within single walled carbon nanotubes (SWNTs) as determined by high resolution electron microscopy (HRTEM) is described. Simple packed structures, such as the alkali halides, form related structures within SWNTs that are found to be integral atomic layers in terms of their thickness as a function of the encapsulating SWNT diameter. An enhanced HRTEM image restoration technique reveals precise data concerning lattice distortions present in these crystals. More complex structures, such as those derived from 3D complex, layered and chain halides form related crystal structures within SWNTs. In narrow SWNTs (i.e. with diameters less than ca. 1.6 nm), structures consisting of individual 1D polyhedral chains (1D-PHCs) were obtained that were derived from the corresponding bulk halides structures. In the case of infinite 3D network and layered halides, the 1D polyhedral chains form with lower co-ordinations than in the bulk. Molecular halides also intercalate into SWNTs but these do not readily form organised structures within SWNTs.

Cluster formation can be induced in situ in SWNTs filled with ZrCl4 by electron beam irradiation of SWNT/ZrCl4 composites within a field emission gun transmission electron microscope (FEGTEM); the process represents a possible route to the synthesis of 1D-quantum dot arrays formed by related materials.

1D crystals of lanthanide halides of the form LnCl3 (Ln = La, Nd, Sm, Eu, Gd, Tb or Yb) have been inserted into single-walled carbon nanotubes (SWNTs) using the molten salt capillary filling method; ca. 20–40% of all the observed SWNTs were filled with melts in the range 650–910 °C with no observable damage to the carbon tubules; high resolution transmission electron microscopy (HRTEM) studies showed that the nanostructures of the encapsulated crystals varied with tubule diameter.