Transition from H-Aggregate Nanotubes to J-Aggregate Nanoribbons

J- and H-aggregates of pi-conjugated dyes are particularly interesting because of their unique optical and excitonic properties. However, control of the size and morphology of J- and H-aggregates remains a challenge. Here, we report the coassembly of lithocholic acid (LCA) and 3,3'-diethylthiacarbocyanine iodide (DiSC(2)(3)) into H-aggregate nanotubes through helical H-aggregate nanoribbons as a precursor in 30% ammonia solution. As the ammonia evaporates, H-aggregate nanotubes transition into flat J-aggregate nanoribbons. The electronic properties of H-aggregate nanotubes and J-aggregate nanoribbons are studied by integrating them with interdigitated gold electrodes. We find that H-aggregate nanotubes form a Schottky junction and J-aggregate nanoribbons form Ohmic contact. In the temperature range from 18 to 28 degrees C, the resistance of the H-aggregate nanotubes is nearly constant, whereas the resistance of the J-aggregate nanoribbons significantly increases with the increase of temperature. Our findings provide a new strategy for controlling the formation of H-aggregate nanotubes and J-aggregate nanoribbons, which can serve as smart building blocks in electronic and optoelectronic devices.