- isomerization of dimethyl 2,3-dibromofumarate.

The isomerization of dimethyl 2,3-dibromofumarate in chloroform solutions was investigated by the combination of nuclear magnetic resonance (NMR) and density functional theory (DFT) calculations. The bromination of dimethyl acetylenedicarboxylate leading to dimethyl 2,3-dibromofumarate produces the isomer initially, which however converts into the more stable isomer. The conversion from to is spontaneous and greatly accelerated by light.

Tunable plasmonic resonances in Si-Au slanted columnar heterostructure thin films.

We report on fabrication of spatially-coherent columnar plasmonic nanostructure superlattice-type thin films with high porosity and strong optical anisotropy using glancing angle deposition. Subsequent and repeated depositions of silicon and gold lead to nanometer-dimension subcolumns with controlled lengths. We perform generalized spectroscopic ellipsometry measurements and finite element method computations to elucidate the strongly anisotropic optical properties of the highly-porous Si-Au slanted columnar heterostructures.

Laterally extended atomically precise graphene nanoribbons with improved electrical conductivity for efficient gas sensing.

Narrow atomically precise graphene nanoribbons hold great promise for electronic and optoelectronic applications, but the previously demonstrated nanoribbon-based devices typically suffer from low currents and mobilities. In this study, we explored the idea of lateral extension of graphene nanoribbons for improving their electrical conductivity. We started with a conventional chevron graphene nanoribbon, and designed its laterally extended variant.

Bulk properties of solution-synthesized chevron-like graphene nanoribbons.

Graphene nanoribbons (GNRs) have received a great deal of attention due to their promise for electronic and optoelectronic applications. Several recent studies have focused on the synthesis of GNRs by the bottom-up approaches that could yield very narrow GNRs with atomically precise edges. One type of GNRs that has received a considerable attention is the chevron-like GNR with a very distinct periodic structure.

Tuning the energy level offset between donor and acceptor with ferroelectric dipole layers for increased efficiency in bilayer organic photovoltaic cells.

Ultrathin ferroelectric polyvinylidene fluoride (70%)-tetrafluoroethylene (30%) copolymer film is inserted between the poly3(hexylthiophene) (P3HT) donor and [6,6]-phenyl-C61-butyric acid methylester (PCBM) acceptor layers as the dipole layer to tune the relative energy levels, which can potentially maximize the open circuit voltage of bilayer organic solar cells. In this work, the power conversion efficiency of P3HT/PCBM bilayer solar cells is demonstrated to be doubled with the inserted dipoles.

Orientational order of a ferroelectric liquid crystal with small layer contraction.

We present spectroscopic and optical studies of a non-layer-shrinkage ferroelectric liquid crystal DSiKN65. The orientational order parameters S, measured with respect to the smectic layer normal using IR spectroscopy on a sample aligned homeotropically, does not exhibit any significant variation between the smectic-A∗ and smectic-C∗ phases. In contrast the birefringence of a planar homogenous sample abruptly increases at the smectic-A∗ to smectic-C∗ transition.

Optical Fourier transform spectroscopy of single-walled carbon nanotubes and single molecules.

We use two-beam interferometry in combination with confocal microscopy for Raman and fluorescence studies of spatially isolated single-walled carbon nanotubes and single dye molecules. We investigate the potential of optical Fourier transform spectroscopy for the spectral characterization of single molecules and molecular nanostructures. We demonstrate that it is possible to obtain the temporal coherence characteristics as well as reliable spectroscopic data of the single photon fluorescence emission of an isolated molecule from one measured interferogram, even though the molecule exhibits intensity fluctuations and spectral jumps.