We report spectrally-narrowed emissions that take place from an organic semiconductor slab crystal of 2,5-bis(4-biphenylyl)thiophene (BP1T) under a low excitation-intensity regime. These emissions are caused with a mercury lamp that operates on a household power supply with an electric current approximately 1 A. The BP1T slab crystal is equipped with a distributed Bragg reflector. To complete this structure the slab crystal is attached to a diffraction grating that is engraved on a surface of a quartz glass substrate. The diffraction gratings have precisely been formed using a focused ion beam with a nanometer-defined precision. The spectral narrowing accompanied by the emission intensity increment is related to the strong mode-coupling between the forward electromagnetic wave and the backward (i.e., reflected) wave within the grating zone. Using a laser we also carried out the emission measurements on the BP1T crystals under a high excitation-intensity regime. The emissions are characterized as the longitudinal multimode laser oscillation, enabling us to determine the group refractive index of 4.56 for the BP1T slab crystal. Under both the low and high excitation-intensity regimes excitons are dominant species of the emission. Their participation in the spectrally-narrowed emissions is briefly discussed.

Microphase-separated structures in poly(styrene-block-isoprene) (SI) block copolymer thin films were investigated by transmission electron microtomography (TEMT). The SI block copolymer showed cylindrical microdomains in the bulk state. Several block copolymer thin films with different thicknesses were prepared by spin-coating and were extensively annealed before the TEMT experiments. Intriguingly, although the cylindrical morphology orienting parallel to the substrate was observed in most of the cases, spherical microdomains were found at certain film thicknesses. The thickness dependence was investigated using a computer simulation based on the self-consistent-field theory, producing a morphological phase diagram based on minimizing free energy. We find that the distortion of the hexagonal lattice of the cylindrical microdomains caused the morphological transition to the spherical microdomains.

The preparation of highly fluorescent one-dimensional (1D) nanostructures within a selected area of a solid substrate is a challenging requirement for the realization of optoelectronic nanodevices. We present a novel method for fabricating highly fluorescent organic nanowires (NWs) embedded in a variety of polymer films through the combined processes of photochemical lithography and solventvapor annealing (SVA). To achieve this, we designed and synthesized an acid-responsive organic fluorophore bearing a self-assembly moiety. The in situ self-assembly of this fluorophore into ultralong nanowires proceeds selectively in designated regions of the polymer matrix via a simple selected-area SVA process. The I-V electrical characteristics of 2-(3 0 ,5 0 -bis(trifluoromethyl)biphenyl-4-yl)-3-(6-3,5-bis(trifluoromethyl)phenyl)pyridine-3-yl)acrylonitrile (Py-CN-TFMBE) structures, selfassembled using the SVA method, were measured on a two-terminal electrode device. This unique fabrication approach, which combines photochemical lithography and SVA, eliminates the difficulties of transferring preformed 1D organic nanostructures to fixed locations on a substrate, thereby establishing a new method for the fabrication control of optoelectronic nanodevices.

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