CHED 75 |
| The idea of harnessing the molecular building blocks to assemble nanometer-scale devices promises the fascinating applications ranging from electronic to medical ones. Due to recent progress in synthesis techniques, complex self-assembled systems started to appear. Additionally, advances in atomic-scale experimental imagining and manipulation techniques have paved the way to the first practical control of transport in molecular devices, in which all elements are parts of a single macro-assembly. We use ab initio techniques, such as Density Functional Theory (DFT) in combination with classical force field (FF) calculations to predict and to explain experimental results of transport and photoexcited properties of several molecular composites/hybrids, as well as of disordered materials. Among the considered systems are: i) Adsorbed DNA strands on metallic surfaces. Here the unique STM spectra of bases promise resolution of the structure and fast sequencing of DNA. To interpret experimental results, we simulate tunneling spectra and identify the underlying electronic features of each DNA bases adsorbed on Cu(111) surface. Large dipole moments of bases containing only one oxygen atom, lead to the strong interaction of cytosine and guanine with the substrate through chemisorptions. Thymine and adenine, having smaller dipole moments, interact weakly with the surface through physisorption. The observed diversity of the geometrical and electronic structures of the nucleobases on the Cu substrate provides guidelines for interpreting DNA tunneling spectra in the STM experiments, and shows perfect agreement of simulation results with available dI/dV STM measurements. ii) We also investigated structural relaxation and uncaging of DNA strands wrapping around carbon nanotubes. Our simulated structures coincide with recently resolved STM images of these systems. Our quantum-classical numerical approach allows to describe extended complex systems on a quantum mechanical level and opens a new prospective for understanding of transport properties in biopolymers, interacting with inorganic substrates. |
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Sci-Mix
8:00 PM-10:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Sci-Mix
General Posters
Division of Chemical Education |