Gareth Brown

The size distribution, imaging and obstructing properties of C60 and higher fullerenes formed within arc-grown single walled carbon nanotubes

Abstract 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.

Two layer 4:4 co-ordinated KI crystals grown within single walled carbon nanotubes

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.

Capillarity and silver nanowire formation observed in single walled carbon nanotubes

Single walled carbon nanotubes (SWNTs) exhibit similar capillarity properties to those exhibited by multiple walled carbon nanotubes (MWNTs); SWNTs, previously filled in low yield (ca. 2%) by solution chemistry techniques, can be filled in high yield (up to ca. 50%) by the liquid phase method; compositions from the KCl–UCl4 and AgCl–AgBr systems were used to fill SWNTs without causing them significant chemical or thermal damage; in the case of the latter, exposure to light or an electron beam resulted in the partial photolytic reduction of SWNT incorporated silver halides to continuous metallic silver ‘nanowires’ within the capillaries.

1D lanthanide halide crystals inserted into single-walled carbon nanotubes

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.

Electron beam induced in situ clusterisation of 1D ZrCl4 chains within single-walled carbon nanotubes

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.

Molecules that add up

As information technology encroaches more and more into our lives, attention is turning to how the revolution started by silicon logic gates can be carried forward. Smaller-scale information processors is one approach to which chemical solutions can be imagined. The first molecular logic gates were built in Belfast a few years back. These artificial systems use chemical inputs and light output, reversing the natural roles existing within the eye. They can now do simple addition.

The characterization of sub-nanometer scale structures within single walled carbon nanotubes

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 Crystallography of Metal Halides formed within Single Walled Carbon Nanotubes

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 integral atomic layers in terms of their thickness. An enhanced HRTEM image restoration technique reveals precise data concerning lattice distortions present in these crystals. More complex structures formed within SWNTs, such as those derived from 3D complex, layered and chain halides form related crystal structures within SWNTs. In narrow (i.e. 1.6nm diameter) SWNTs, these halides form structures that consist of individual 1D polyhedral chains (1D-PHCs) derived from the corresponding bulk halides within SWNTs. In the case of the 3D complex and layered halide structures, the polyhedral chains form with lower coordination than in the bulk. Molecular halides also form within SWNTs but these are frequently disordered and do not readily form organised structures within SWNTs.