Anisotropy in the electrical conductivity of rutile TiO(2) in the (110) plane.

The bulk electrical conductivity of a TiO(2)(110) single crystal has been measured in all azimuths parallel to the (110) plane using a four-point probe. A distinct anisotropy in the conductivity has been found, with the highest bulk conductivity direction being parallel to the 001 direction.

Unusual hydrogen bonding in water-filled carbon nanotubes.

We present the first experimental vibrational spectroscopy study providing direct evidence of a water phase inside single-walled carbon nanotubes that exhibits an unusual form of hydrogen-bonding due to confinement. Water adopts a stacked-ring structure inside nanotubes, forming intra- and inter-ring hydrogen bonds. The intra-ring hydrogen bonds are bulk-like while the inter-ring hydrogen bonds are relatively weak, having a distorted geometry that gives rise to a distinct OH stretching mode.

Adsorption of triethylenediamine on Al2O3-III: Bonding to Lewis acid Al3+ sites.

The adsorption of triethylenediamine (TEDA) on Lewis acid (Al(3+)) sites of the highly dehydroxylated Al(2)O(3) surface has been observed by FT-IR spectroscopy. This was done by monitoring the competitive adsorption of TEDA and CO on the Al(3+) sites. A stoichiometric replacement of Al(3+)-CO species was observed as Al(3+)-TEDA surface species were formed.

The adsorption of triethylenediamine on Al(2)O(3)-II: hydrogen bonding to Al-OH groups.

The hydrogen bonding of the triethylenediamine (TEDA) molecule to isolated Al-OH groups on partially dehydroxylated high area gamma-Al(2)O(3) powder has been studied using transmission IR spectroscopy. It has been found that TEDA adsorbs both singly and as multiple species to single Al-OH groups in clearly separable equilibrium stages of adsorption at 300 K. The reversible adsorption of a single TEDA molecule to Al-OH fits the Langmuir adsorption isotherm well, and the enthalpy of adsorption is found to be -15.

The adsorption of triethylenediamine on Al(2)O(3)-I: a vibrational spectroscopic and desorption kinetic study of surface bonding.

The adsorption of triethylenediamine (TEDA) at 300 K is observed to occur via hydrogen bonding to isolated Al-OH groups on the surface of partially dehydroxylated high area gamma-Al(2)O(3) powder. This form of bonding results in +0.3 to +0.

Spectroscopic measurement of diffusion kinetics through subnanometer and larger Al2O3 particles by a new method: the interaction of 2-chloroethylethyl sulfide with gamma-Al2O3.

A new method to study the diffusion properties of molecules into porous materials using transmission IR spectroscopy is employed. A measurement of the diffusion of the 2-chloroethylethyl sulfide (2-CEES) molecule into two types of gamma-Al2O3 powder is performed, showing that the diffusion rate into subnanometer crystallite particle size gamma-Al2O3 powders (subnano-Al2O3) is higher than that into the larger crystallite particle size powder. It is shown that a surface diffusion mechanism can be used to model the diffusion process giving good agreement with the experimental results, where Dsubnano-Al2O3 is approximately 5 times larger than Dmultinano-Al2O3 at 170 K for the 2-CEES molecule.

Perturbation of adsorbed CO by amine derivatives coadsorbed on the gamma-Al2O3 surface: FTIR and first principles studies.

The coadsorption of CO and triethylenediamine (TEDA) (also called 1,4-diazabicyclo[2.2.2]octane, DABCO) on a high-area gamma-Al2O3 surface has been investigated with use of transmission FTIR spectroscopy.

Etching of carbon nanotubes by ozone--a surface area study.

The oxidative etching of single walled carbon nanotubes (SWNTs) is useful for opening the end caps and the sidewalls of the nanotubes to provide access to the interior. We have studied the effect of successive treatment of SWNTs by 95% pure O(3)(g), which is a powerful and convenient oxidizing agent. The surface area of the SWNTs was measured following exposure to O(3)(g) at 300 K and also following heating to 1073 K in a vacuum to decompose the oxidized groups on the nanotubes, a procedure called etching.

Dimensional effects on the LO-TO splitting in CF4: first-principles and infrared absorption studies.

The development of longitudinal optical-transverse optical (LO-TO) modes in CF(4) has been studied experimentally and theoretically as a function of dimensionality. Infrared absorption experiments for CF(4) adsorbed on single-walled carbon nanotubes indicate a lack of LO-TO splitting at low coverage and a gradual appearance of LO-TO modes as the coverage of CF(4) on the nanotubes is increased. We have performed density functional perturbation theory calculations for the vibrational frequencies, IR absorption spectra, and phonon density of states for CF(4) in one, two, and three dimensions.

Vibrational behavior of adsorbed CO2 on single-walled carbon nanotubes.

We present theoretical and experimental evidence for CO(2) adsorption on different sites of single walled carbon nanotube (SWNT) bundles. We use local density approximation density functional theory (LDA-DFT) calculations to compute the adsorption energies and vibrational frequencies for CO(2) adsorbed on SWNT bundles. The LDA-DFT calculations give a range of shifts for the asymmetric stretching mode from about -6 to -20 cm(-1) for internally bound CO(2), and a range from -4 to -16 cm(-1) for externally bound CO(2) at low densities.

Adsorption of CF4 on the internal and external surfaces of opened single-walled carbon nanotubes: a vibrational spectroscopy study.

Infrared spectroscopy has been used to make the first experimental discrimination between molecules bound by physisorption on the exterior surface of carbon single-walled nanotubes (SWNTs) and molecules bound in the interior. In addition, the selective displacement of the internally bound molecules has been observed as a second adsorbate is added. SWNTs were opened by oxidative treatment with O(3) at room temperature, followed by heating in a vacuum to 873 K.