Controlled deposition of highly ordered soluble acene thin films: effect of morphology and crystal orientation on transistor performance

Radially oriented anthracene nanowire arrays: preparation, growth mechanism, and optical fluorescence

Radially oriented anthracene nanowires and their self-assembled concentric ring arrays were prepared through a facial solvent-evaporation method. The successful growth of anthracene nanowires can be attributed to a combined mechanism of molecular self-assembly facilitated by strong π-π intermolecular interactions together with evaporation-induced capillary flow and fingering instability. Their radial orientation is determined by the capillary flow; their shape (either straight or curved nanowires) is governed by the competition between the capillary and Marangoni convectional flows. The self-assembly of nanowires into large-scale concentric ring arrays can be interpreted in terms of the repeated slipping-and-sticking motions of the contact line. The high-quality crystalline anthracene nanowire arrays exhibit size-dependent fluorescence emission with high-degree anisotropy.

Crystal growth near moving contact lines on homogeneous and chemically patterned surfaces

We have systematically investigated how solution crystallization in the proximity of moving contact lines can be modulated by the parameters of the coating flow as well as chemical patterning of the substrate surface. We have studied the monoclinic model substance nicotinamide in the solvent isopropanol, which tends to form needle-like crystals in bulk solution. Three crystallization regimes were identified dependent on the coating speed. At high speeds viscous entrainment dominates over solvent evaporation, and an essentially azimuthally isotropic, spherulithic morphology results. For intermediate speeds a branched morphology with preferential alignment parallel to the coating direction is observed. For low speeds, filament-like crystal patterns well aligned with the coating direction were obtained.