Morphology of self-assembled merocyanine J-aggregates in films studied by scanning near-field optical microscope

Uniform exciton fluorescence from individual molecular nanotubes immobilized on solid substrates

Self-assembled quasi one-dimensional nanostructures of pi-conjugated molecules may find a use in devices owing to their intriguing optoelectronic properties, which include sharp exciton transitions, strong circular dichroism, high exciton mobilities and photoconductivity. However, many applications require immobilization of these nanostructures on a solid substrate, which is a challenge to achieve without destroying their delicate supramolecular structure. Here, we use a drop-flow technique to immobilize double-walled tubular J-aggregates of amphiphilic cyanine dyes without affecting their morphological or optical properties. High-resolution images of the topography and exciton fluorescence of individual J-aggregates are obtained simultaneously with polarization-resolved near-field scanning optical microscopy. These images show remarkably uniform supramolecular structure, both along individual nanotubes and between nanotubes in an ensemble, demonstrating their potential for light harvesting and energy transport.

Optical waveguide self-assembled from organic dye molecules in solution

Fiber-shaped H-aggregates with lengths of up to 300 microm are synthesized by self-assembly of thiacyanine (TC) dye molecules in solution. Photoluminescence (PL) images and spatially resolved PL spectra of the fibers that are transferred onto a glass substrate reveal that the fibers act as single-mode optical waveguides that propagate PL in the range of 520 to 560 nm over 250 microm without any loss.