Research

An excited-state AIBN molecule dissociates, forming a pair of radicals and a nitrogen moleculeSnapshot taken near the end of a simulation where an excited-state AIBN molecule dissociates, forming a pair of radicals and a nitrogen molecule. The red (orange) isosurfaces indicate positive (negative) spin density.

Real time simulation

Methoxy to formaldehyde excited-state reaction trajectory: evolution of lengths of the C−H bond being cleaved and the O−H bond being formed. Reaction starts from methoxy on the upper left and proceeds to formaldehyde on the lower right. The yellow curve corresponds to the ground-state molecular dynamics trajectory prior to the electronic excitation. The cyan curve corresponds to the excited-state part of the trajectory. The blue curve corresponds to rapid hydrogen transfer.

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Heterogeneous Catalysis

The electron density of clorine adsorbed on a gold surface. This work determined the type of interaction between clorine and gold, important for improving the catalytic activity of gold.

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Biomolecules

Electron density of the mixed band at 0.65 eV below the HOMO

We investigate a system consisting of B-DNA and an array of (10,0) carbon nanotubes periodically arranged to fit into the major groove of the DNA. We obtain an accurate electronic structure of the combined system, which reveals that it is semiconducting and that the bands on either end of the gap are derived exclusively from one of the two components. We discuss in detail how this system can be used as either an electronic switch involving transport through both components, or as a device for ultrafast DNA sequencing.

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Nanomaterials

graphene starWe investigate, using benzenoid graph theory and first-principles calculations, the magnetic properties of arbitrarily shaped finite graphene fragments to which we refer as graphene nanoflakes (GNFs). We demonstrate that the spin of a GNF depends on its shape due to topological frustration of the π-bonds. For example, a zigzag-edged triangular GNF has a nonzero net spin, resembling an artificial ferrimagnetic atom, with the spin value scaling with its linear size. In general, the principle of topological frustration can be used to introduce large net spin and interesting spin distributions in graphene. These results suggest an avenue to nanoscale spintronics through the sculpting of graphene fragments.

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See also: 2D-Materials
We investigate the electronic coupling between a TiO2 nanowire and a natural dye sensitizer, using state-of-the-art time-dependent first-principles calculations. The model dye molecule, cyanidin, is deprotonated into the quinonoidal form upon adsorption on the wire surface. This results in its highest occupied molecular orbital (HOMO) being located in the middle of the TiO2 bandgap and its lowest unoccupied molecular orbital (LUMO) being close to the TiO2 conduction band minimum (CBM), leading to greatly enhanced visible light absorption with two prominent peaks at 480 and 650 nm. We find that excited electrons are injected into the TiO2 conduction band within a time scale of 50 fs with negligible electron−hole recombination and energy dissipation, even though the dye LUMO is located 0.1−0.3 eV lower than the CBM of the TiO2 nanowire.

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