Computational Analysis of Transition Metal Doped Nanotubes and Their Application to Molecular Electronics

We have previously proposed molecular circuits designed from polyaniline polymer strands, polyacetylene polymer strands and charge transfer salts acting as transistors. Due to unique properties that are demonstrated in this manuscript, we propose the use of carbon single wall nanotubes and transition metal endohedrally doped single wall carbon nanotubes (SWNTs) for utilization in molecular electronics. Different transition metals were used in a systematic fashion to manipulate the molecular orbital energy gap (HOMO-LUMO gap) of metallic (Ch = (n = m)) nanotubes. Gradient corrected, Density Functional Theory (DFT) Self Consistent Field (SCF) calculations were used to calculate molecular orbital energy levels, HOMO-LUMO gaps, electron affinities, ionization energies and other electronic properties for these molecules. The effect that a SWNT’s length has on its HOMO-LUMO gap was investigated. DFT-SCF calculations were also used to demonstrate how multiple metal filled nanotubes could be used to construct a molecular nanotube based transistor.

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Instrumentation for multi-modal spectroscopic diagnosis of epithelial dysplasia

Reflectance and fluorescence spectroscopies have shown great promise for early detection of epithelial dysplasia. We have developed a clinical reflectance spectrofluorimeter for multimodal spectroscopic diagnosis of epithelial dysplasia. This clinical instrument, the FastEEM, collects white light reflectance and fluorescence excitation-emission matrices (EEM’s) within a fraction of a second. In this paper we describe the FastEEM instrumentation, designed for collection of multi-modal spectroscopic data. We illustrate its performance using tissue phantoms with well defined optical properties and biochemicals of known fluorescence properties. In addition, we discuss our plans to develop a system that combines a multi-spectral imaging device for wide area surveillance with this contact probe device.

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Electron transfer to oriented molecules: Surprising steric effect in t-butyl bromide

Collisions between neutral K atoms and oriented t-butyl bromide molecules produce the ions K+ and Br− at energies high enough to separate charged particles (≳4 eV). Ions are detected by coincidence tof mass spectrometry for orientation of the t-butyl bromide such that the K atom attacks either the Br end or the t-butyl end of the molecule. At high energies the steric asymmetry factor is larger than that for CH3Br. But at energies near threshold, the steric asymmetry factor reverses sign and attack at the t-butyl end becomes more reactive than attack at the Br end. The electron is apparently transferred into different orbitals at different ends.

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