Porphyrin Nanowires with Epitaxially Locked Uniaxial Orientation

The ability to drive the growth of nano-objects of functional materials with desired shape, size, and orientation is necessary for exploiting the potentiality of organic-based nanoelectronics. Here, we present a methodology for growing by vacuum sublimation low-dimensional structures of a free-base porphyrin, in particular metal-free tetraphenylporphyrin nanowires with the structure of the known triclinic polymorph and uniaxial orientation. This peculiar structure and morphology is achieved through a double coincidence between lattice lines of a properly designed substrate and those of the deposited crystalline nanowires. In addition, the same substrate is also chosen for its water solubility, which allows the wet transfer of films on any solid surface, a fundamental prerogative for a thorough characterization and the successful device integration of functional organic materials. Finally, the optical analysis of highly ordered nanowires highlights for the first time the anisotropic response of triclinic metal-free tetraphenylporphyrin single crystals and gives some insights on the intermolecular interactions within the crystal.