Karl S. Coleman

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.

Graphene Film Growth on Polycrystalline Metals

Graphene, a true wonder material, is the newest member of the nanocarbon family. The continuous network of hexagonally arranged carbon atoms gives rise to exceptional electronic, mechanical, and thermal properties, which could result in the application of graphene in next generation electronic components, energy-storage materials such as capacitors and batteries, polymer nanocomposites, transparent conducting electrodes, and mechanical resonators. With one particularly attractive application, optically transparent conducting electrodes or films, graphene has the potential to rival indium tin oxide (ITO) and become a material for producing next generation displays, solar cells, and sensors. Typically, graphene has been produced from graphite using a variety of methods, but these techniques are not suitable for growing large-area graphene films. Therefore researchers have focused much effort on the development of methodology to grow graphene films across extended surfaces. This Account describes current progress in the formation and control of graphene films on polycrystalline metal surfaces. Researchers can grow graphene films on a variety of polycrystalline metal substrates using a range of experimental conditions. In particular, group 8 metals (iron and ruthenium), group 9 metals (cobalt, rhodium, and iridium), group 10 metals (nickel and platinum), and group 11 metals (copper and gold) can support the growth of these films. Stainless steel and other commercial copper-nickel alloys can also serve as substrates for graphene film growth. The use of copper and nickel currently predominates, and these metals produce large-area films that have been efficiently transferred and tested in many electronic devices. Researchers have grown graphene sheets more than 30 in. wide and transferred them onto display plastic ready for incorporation into next generation displays. The further development of graphene films in commercial applications will require high-quality, reproducible growth at ambient pressure and low temperature from cheap, readily available carbon sources. The growth of graphene on metal surfaces has drawbacks: researchers must transfer the graphene from the metal substrate or remove the metal by etching. Further research is needed to overcome these transfer and removal challenges.

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.

Pyridine-Functionalized Single-Walled Carbon Nanotubes as Gelators for Poly(acrylic acid) Hydrogels

Pyridine-functionalized single-walled carbon nanotubes (SWNTs) are prepared from the addition of a pyridine diazonium salt to nanotubes. The location and distribution of the functional groups is determined by atomic force microscopy using electrostatic interactions with gold nanoparticles. The pyridine-functionalized SWNTs are able to act as cross-linkers and hydrogen bond to poly(acrylic acid) to form SWNT hydrogels. The pyridine-functionalized SWNTs are further characterized using Raman, FTIR, UV/vis-NIR, and X-ray photoelectron spectroscopy and thermogravimetric analysis-mass spectrometry.

Silver(I) complex of a new imino-N-heterocyclic carbene and ligand transfer to palladium(II) and rhodium(I)

A new imino-N-heterocyclic carbene ligand precursor [1-(2,4,6-Me3C6H2)imidazolium-3-{CH2C(t-Bu)N(i-Pr)}] bromide has been synthesised and structurally characterised. The silver(I) complex [Ag(C⁁imine)2]AgBr2, where (C⁁imine) = 1-(2,4,6-Me3C6H2)imidazol-2-ylidene-3-{CH2C(t-Bu)N(i-Pr)}, was readily prepared by reaction with Ag2O. Transfer of the ligand from silver(I) to palladium(II) and rhodium(I) by reaction with [PdCl2(MeCN)2] and [Rh(cod)(THF)2][BF4] led to the tautomerisation of the imine moiety to the enamine affording the structurally characterised complex [PdCl2(C⁁enamine)] and [Rh(cod)(C⁁enamine)][BF4] respectively, where (C⁁enamine) = 1-(2,4,6-Me3C6H2)imidazol-2-ylidene-3-{CHC(t-Bu)NH(i-Pr)}.

Catalytic oxidation of alcohols into aldehydes and ketones by an osmium-copper bifunctional system using molecular oxygen

Abstract The oxidation of allylic and benzylic alcohols to aldehydes can be carried out at room temperature as low as 25°C with molecular oxygen, in the presence of the bifunctional osmium-copper system OsO 4 CuCl acting as the catalyst.

Directly observed covalent coupling of quantum dots to single-wall carbon nanotubes

Carboxylate chemistry is used to covalently couple metal nanoparticles to defect sites in controllably oxidized single-walled carbon nanotube termini and side-walls, and this process monitored by atomic force microscopy.

Effect of carburising agent on the structure of molybdenum carbides

Molybdenum carbides have been prepared by the temperature programmed reaction method using mixtures of hydrogen and methane, hydrogen and ethane, and hydrogen and butane, and characterised with X-ray diffraction, transmission electron microscopy, 13C solid state NMR and EXAFS spectroscopy. The results show that the choice of hydrocarbon used to synthesise molybdenum carbide significantly affects the structure and texture of the resultant materials. Increasing the chain length of the carburising agent reduces the particle size and the temperature for complete phase transformation from molybdenum oxide to carbide is lowered. Carburising with a mixture of hydrogen and methane gives rise to hexagonal closed packed (hcp) carbide, while when using butane as the carbon source, molybdenum oxide is mainly reduced to face centred cubic (fcc) carbide. However, using ethane as the carbon source, the resultant carbide has a mixed phase composition with the hcp phase predominant. The molybdenum carbide prepared with ethane as the carbon source has the roughest surface and highest hydrogen adsorption capacity, while that prepared with butane has a very condensed surface. There is a substantial difference in the molybdenum co-ordination environments present among the carbides prepared with different carburising agents.

Fluorescent Single-Walled Carbon Nanotubes Following the 1,3-Dipolar Cycloaddition of Pyridinium Ylides

Pyridinium ylides generated from simple Krohnke salts undergo a 1,3-dipolar cycloaddition to single-walled carbon nanotubes (SWNTs) offering a simple and convenient method for the covalent modification of carbon nanotubes. The indolizine functionalized SWNTs generated, emit blue light when excited at 335 nm. The location and distribution of the functional groups was determined by AFM using electrostatic interactions with gold nanoparticles. While resonance Raman spectroscopy showed that the 1,3-dipolar cylcloaddition of the pyridinium ylides to the nanotube surface was selective for metallic and large diameter semiconducting SWNTs. The indolizine functionalized SWNTs were further characterized using FTIR, UV-vis-NIR, TGA-MS, and XPS.