Nanotechnology

  2010 MAR 22 - (VerticalNews.com) -- According to a study from Jinan, People's Republic of China, "DFT calculations are used to investigate the origin of the experimentally observed changes in the visible photoactivity of Cubic and rhombic In2O3 induced by N doping. Two possible mechanisms for the red shift in N-doped In2O3 are tentatively put forward, according to the doping types."

  "For substitutional N-doping models, our results Show that, in both polymorphs, partial N 2p states mix with 0 2p states and localized lie above the top of the valence band, acting as the frontier orbital level. Electronic transitions from these localized states induce a red shift to the visible region of the optical absorption edge. For interstitial N-doping models, NO pi-antibonding states localized in the gap contribute to the impurity levels. The electronic transition from these states may well explain the mechanism of the red shift in interstitial N-doped In2O3. The calculated optical properties for all N-doped In2O3 show a significant visible light absorption at about 400-600 nm, which corresponds to the experimental result," wrote H.G. Sun and colleagues, Shandong University ...read more

  2010 MAR 22 - (VerticalNews.com) -- "It is shown that the lines of adsorbed hydrogen pair atoms divide a graphene sheet into electronically independent strips and form all electron waveguide or 2H-line graphene-based superlattice (2HG-SL). We investigated the electronic properties of such structures in detail," investigators in Russia report.

  "The electronic spectra of a ''zigzag'' (17,0)2HG-SL are similar to those of armchair graphene ribbons and have similar oscillation of the band gap with the width between adjacent 2H-lines (number n). The induced strain with the direction perpendicular to the hydrogen pair ''lines'' significantly changes the electronic properties of(he investigated Structures. For example, in the case of the 2HG-SL (3n,0) (n > 2) we observed the semiconductor-metal transition. Superlattices of the (n,n) type with a ''staircase'' of adsorbed pairs of H atoms are semiconductors with nearly linear decreasing of the band gap with increasing n. We found that the configuration with the opposite spin (antiferromagnetic) orientation between ferromagnetically ordered edge states of the (n,n) 2HG-SL is energy favorable. We also Suggested all experimental way of fabricating these superlattices," wrote L.A. Chernozatonskii and colleagues, Russian Academy of Science ...read more

  2010 MAR 22 - (VerticalNews.com) -- "The electronic structure at organic/organic interfaces plays a key role, among others, in defining the quantum efficiency of organics-based photovoltaic cells," investigators in Talence, France report.

  "Here, we perform quantum-chemical and microelectrostatic calculations oil molecular aggregates of various sizes and shapes to characterize the interfacial dipole moment at pentacene/C-60 heterojunctions. The results show that the interfacial dipole mostly originates in polarization effects Clue to the asymmetry in the Multipolar expansion of the electronic density distribution between the interacting molecules, rather than in a charge transfer from donor to acceptor," wrote M. Linares and colleagues, University of Bordeaux ...read more