Stacy E. Snyder

Polarization Component of Cohesion Energy in Single-Wall Carbon Nanotube-DNA Complexes ¶

Within the framework of a quantum mechanical model, the polarization component of the energy of cohesion of an ionized DNA molecule to the surface of a nanotube has been calculated. Neglecting the polarization of the DNA, and in the absence of external screening, the binding energy is ∼0.47 eV per elementary charge. The effective nanotube screening parameter is ∼2 and cannot be reduced to classical expressions for metallic and dielectric screening.

Effect of nitrogen gas on the lifetime of carbon nanotube field emitters for electron-impact ionization mass spectrometry

The lifetime of a patterned carbon nanotube film is evaluated for use as the cold cathode field emission ionization source of a miniaturized mass spectrometer. Emitted current is measured as a function of time for varying partial pressures of nitrogen gas to explore the robustness and lifetime of carbon nanotube cathodes near the expected operational voltages (70-100 eV) for efficient ionization in mass spectrometry. As expected, cathode lifetime scales inversely with partial pressure of nitrogen. Results are presented within the context of previous carbon nanotube investigations, and implications for planetary science mass spectrometry applications are discussed.

Optical Identification of a DNA‐Wrapped Carbon Nanotube: Signs of Helically Broken Symmetry

High intrinsic mobility and small, biologically-compatible size make single-walled carbon nanotubes (SWNTs) in demand for the next generation of electronic devices. Further, the wide range of available bandgaps due to changes in diameter and symmetry give SWNTs greater versatility than traditional semiconductors. Single-stranded DNA has been employed to make these desirable properties accessible for large scale fabrication of devices. Because single-stranded DNA can helically wrap a SWNT, forming a stable hybrid structure, DNA/polymer wrapping has been used to disperse bundles of intrinsically hydrophobic SWNTs into individual tubes in aqueous solution. The ability to isolate individual tubes, make them soluble, and separate them according to symmetry would enable fabrication of SWNT optoelectronic devices that benefit from the unique electronic properties of specific nanotube structures. Envisioning optoelectronic applications of nanotubes, we investigate whether the optical properties of DNA-wrapped SWNT materials are different than those of pristine SWNTs. Our previous work found that bandstructures of DNA-SWNTs were indeed affected by the charged wrap. That is, the direct optical bandgap,

Effect of isotope mass on simulations of the high-mode pedestal and edge localized modes

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DNA-Wrapped Carbon Nanotubes as Potential Optoelectronic Materials

, decreases, but changes are fairly small. This is consistent with the available experimental data in standard experimental geometry in which incident light is polarized along the SWNT axis. Here we consider optical absorption of light with perpendicular (or circular) polarization with respect to the tube axis, which has been measured experimentally for SWNTs dispersed using a surfactant. In this geometry we find qualitative changes in the absorption spectra of SWNTs upon hybridization with DNA, including strong optical circular dichroism in non-chiral SWNTs.

Cross-polarized spectroscopy of DNA-wrapped nanotubes: unraveling the nature of optical response

Simulations of Joint European Torus (JET) [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] type I high-mode (H-mode) discharges with edge localized modes (ELMs) are used to study the effect of isotope mass on the height of the pedestal and the frequency of ELMs. A dynamic model for the H-mode pedestal and ELM cycles is employed in the JETTO integrated modeling code [M. Erba et al., Plasma Phys. Control. Fusion 39, 261 (1997)]. The stability criteria that are used to trigger ELM crashes in the JETTO simulations are calibrated with the HELENA and MISHKA ideal magnetohydrodynamic (MHD) stability codes [A. B. Mikhailovskii et al., Plasma Phys. Rep. 23, 713 (1997)]. Results obtained using a pedestal model in which the pedestal width increases with isotope mass are compared with those obtained using a fixed, prescribed pedestal width. In JET type I ELMy H-mode discharges, it is found that the height of the pressure pedestal increases and that the frequency of the ELMs decreases as the isotope mass is increase...

Theory of Electronic and Optical Properties of DNA–SWNT Hybrids

In the frame of tight-binding theory, we investigate modulation of the optical properties of single-wall carbon nanotubes (SWNTs) helically wrapped with single-stranded DNA. We predict that certain wraps may qualitatively change the one-electron absorption spectrum for light polarized across the SWNT. Lifting of the optical selection rules is due to nanotube symmetry-breaking in the Coulomb potential of the ionized DNA backbone.