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W Edward Billups

Publications and source records attributed to W Edward Billups.

7 recordsLinked to original sources
PubMed2006

Epoxidation and deoxygenation of single-walled carbon nanotubes: quantification of epoxide defects.

Epoxidation of single-walled carbon nanotubes (SWNTs) may be carried out by the reaction of SWNTs with either trifluorodimethyldioxirane or 3-chloroperoxybenzoic acid; the resulting O-SWNTs are spectroscopically similar to those formed by ozonolysis. Quantification of the epoxide substituents is possible through the catalytic de-epoxidation reaction using MeReO3/PPh3 and the 31P NMR spectroscopy. The de-epoxidation methodology may be used to determine that wet air oxidation is preferable to either acid or O2/SF6 purification. We have demonstrated that previously assumed "pure" SWNTs are actually "doped" to a level of at least 1 oxygen per 250 carbon atoms.

Journal Article↗
PubMed2006

Effect of magnesium and iron on the hydration and hydrolysis of guar gum.

The effect that magnesium and iron have on the hydration and hydrolysis of guar gum at pH 12 was studied as a function of viscosity. It was found that small concentrations of magnesium do not affect the dissolution ratio of guar but significantly decrease hydrolysis at high temperatures. These results suggest that Mg(OH)(2) forms an adduct with the polysaccharide that prevents thermal hydrolysis of the guar. Viscosity measurements recorded in the presence of iron at pH 12 show that ferric iron inhibits hydration or dissolution of guar and may accelerate chain scission of fully hydrated guar when solutions are heated in an autoclave at 121 degrees C.

Carbohydrate Conformation↗
PubMed2005

Functionalization density dependence of single-walled carbon nanotubes cytotoxicity in vitro.

The cytotoxic response of cells in culture is dependant on the degree of functionalization of the single-walled carbon nanotube (SWNT). After characterizing a set of water-dispersible SWNTs, we performed in vitro cytotoxicity screens on cultured human dermal fibroblasts (HDF). The SWNT samples used in this exposure include SWNT-phenyl-SO(3)H and SWNT-phenyl-SO(3)Na (six samples with carbon/-phenyl-SO(3)X ratios of 18, 41, and 80), SWNT-phenyl-(COOH)(2) (one sample with carbon/-phenyl-(COOH)(2) ratio of 23), and underivatized SWNT stabilized in 1% Pluronic F108. We have found that as the degree of sidewall functionalization increases, the SWNT sample becomes less cytotoxic. Further, sidewall functionalized SWNT samples are substantially less cytotoxic than surfactant stabilized SWNTs. Even though cell death did not exceed 50% for cells dosed with sidewall functionalized SWNTs, optical and atomic force microscopies show direct contact between cellular membranes and water-dispersible SWNTs; i.e. the SWNTs in aqueous suspension precipitate out and selectively deposit on the membrane.

Cells, Cultured↗
PubMed2005

Structure analyses of dodecylated single-walled carbon nanotubes.

Alkylation of nanotube salts prepared using either lithium, sodium, or potassium in liquid ammonia yields sidewall-functionalized nanotubes that are soluble in organic solvents. Atomic force microscopy and transmission electron microscopy studies of dodecylated SWNTs prepared from HiPco nanotubes and 1-iodododecane show that extensive debundling results from intercalation of the alkali metal into the SWNT ropes. TGA-FTIR analyses of samples prepared from the different metals revealed radically different thermal behavior during detachment of the dodecyl groups. The SWNTs prepared using lithium can be converted into the pristine SWNTs at 180-330 degrees C, whereas the dodecylated SWNTs prepared using sodium require a much higher temperature (380-530 degrees C) for dealkylation. SWNTs prepared using potassium behave differently, leading to detachment of the alkyl groups over the temperature range 180-500 degrees C. These differences can be observed by analysis of the solid-state 13C NMR spectra of the dodecylated SWNTs that have been prepared using the different alkali metals and may indicate differences in the relative amounts of 1,2- and 1,4-addition of the alkyl groups.

Alkylation↗
PubMed2004

Gas hydrate single-crystal structure analyses.

The first single-crystal diffraction studies on methane, propane, methane/propane, and adamantane gas hydrates SI, SII, and SH have been performed. To circumvent the problem of very slow crystal growth, a novel technique of in situ cocrystallization of gases and liquids resulting in oligocrystalline material in a capillary has been developed. With special data treatment, termed oligo diffractometry, structural data of the gas hydrates of methane, acetylene, propane, a propane/ethanol/methane-mixture and an adamantane/methane-mixture were obtained. Cell parameters are in accord with reported values. Host network and guest are subject to extensive disorder, reducing the reliability of structural information. It was found that most cages are fully occupied by a guest molecule with the exception of the dodecahedral cage in the acetylene hydrate which is only filled to 60%. For adamantane in the icosahedral cage a disordered model is proposed.

Journal Article↗
PubMed2002

Fluorination of single-wall carbon nanotubes and subsequent derivatization reactions.

This Account focuses on the most recent and systematic efforts in the area of functionalization chemistry of the single-wall carbon nanotubes (SWNTs) which utilizes direct fluorination for the preparation of "fluoronanonotubes" and their subsequent derivatization. The results obtained prove that the addition of fluorine drastically enhances the reactivity of the nanotube side walls. The use of this strategy as a versatile tool for preparation and manipulation of SWNTs with variable side-wall functionalities has been demonstrated. The functionalized SWNTs have shown an improved solubility in selected solvents and significantly altered electrical, mechanical, and optical properties. An overview of new synthetic methods for preparation and a discussion of characterization data for the functionalized SWNTs are provided.

Journal Article↗