Homopolar dihydrogen bonding in alkali metal amidoboranes: crystal engineering of low-dimensional molecular materials.

Hydrogen bonding is a predominant interaction in supramolecular chemistry. The absence of a conventional hydrogen bond donor in LiNMe(2)BH(3) and KNMe(2)BH(3) results in the formation of elaborate M···H-B polymeric arrays supported by heteropolar and homopolar H···H bonding, in a unique synergistic combination of unconventional intermolecular interactions.

Plasmon-enhanced spectral changes in surface sum-frequency generation with polychromatic light.

We theoretically explore the spectral behavior of the fundamental and sum-frequency waves generated from the surface of a thin metal film in the Kretschmann configuration with coherent ultrashort pulses. We show that the spectra of reflected sum-frequency waves exhibit pronounced shifts for the incident fundamental waves close to the plasmon coupling angle. We also demonstrate that the scale of discovered plasmon-enhanced spectral changes is strongly influenced by the magnitude of the incidence angle and the bandwidth of the source spectrum.

Homopolar dihydrogen bonding in alkali-metal amidoboranes and its implications for hydrogen storage.

The solid-state structures of LiNH(2)BH(3) and NaNH(2)BH(3) have been shown recently to exhibit intricate M(δ+)···(δ-)H-B and N-H(δ+)···(δ-)H-B interactions. However, closer inspection of these structures reveals additional homopolar H···H interactions, viz., B-H(δ-)···(δ-)H-B and N-H(δ+)···(δ+)H-N, which contribute to the relative stability of the extended structures of these crystalline materials. In addition, an NMR study of the isotopomer LiND(2)BH(3) shows that a significant quantity of H(2) is desorbed thermally along with HD, which can only arise from hydride-hydride interactions, either directly from B-H(δ-)···(δ-)H-B moieties or indirectly through the participation of Li-H intermediates.

Electrical properties of Si-SiO(2)-Si nanogaps.

The chances of attaching organic molecules to silicon surfaces can be considerably enhanced if a robust nanogap structure with silicon electrodes can be used to connect the molecules. We describe the electrical properties of such an electrode structure, with a separation of the silicon surfaces in the 3-7 nm range. These silicon nanogaps are manufactured by partly removing the silicon dioxide insulator from a silicon-oxide-silicon material stack, by using a selective oxide etchant. After the activation of the gap (the etching), current instabilities appear, which are comparable to the properties of thin oxides after soft breakdown. Applying a constant voltage can reduce these current instabilities. We also address the issue of surface leakage currents for these nanogap structures.