Mechanical and structural properties of ionically self-assembled nanostructures of meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) and meso-tetra(4-pyridyl)porphyrin (TPyP) are presented. This is the first time that elastic modulus of an ionic porphyrin nanostructure has been reported. X-ray photoelectron spectroscopy (XPS), UV-visible spectra, and elemental analysis all support a stoichiometric 1 : 1 TSPP to TPyP composition. Atomic force microscopy (AFM) revealed that the porphyrin nanostructure is composed of stacked ribbons about 20 nm tall, 70 nm wide, and several microns in length. High resolution transmission electron microscopy (HRTEM) images showed clear lattice fringes 1.5 ± 0.2 nm in width aligned along the length of the nanorod. Selected area electron diffraction (SAED) and powder X-ray diffraction patterns of TSPP:TPyP are consistent with an orthorhombic system and space group Imm2 with lattice parameters a = 26.71 Å, b = 20.16 Å, and c = 8.61 Å. Crystallographic data is consistent with an arrangement of alternating face-to-face TSPP and TPyP molecules forming ordered columns along the length of the nanorods. The structural integrity of the solid is attributed to combined noncovalent interactions that include ionic, hydrogen bonding, and π-π interactions. The values of Young's modulus obtained for the crystalline TSPP:TPyP nanorods averaged 6.5 ± 1.3 GPa. This modulus is comparable to those reported for covalently bonded flexible polymeric systems. The robust bonding character of the TSPP:TPyP nanostructures combined with their mechanical properties makes them excellent candidates for flexible optoelectronic devices.

The use of conjugated polymers such as poly(3-hexylthiophene) (P3HT) in the active layers of plastic electronic devices could provide a more practical and accessible form of energy production and storage. The efficiency of these devices is intimately connected to the morphology of the polymer chains in the active layer materials, as polymer folding affects mesoscale material morphology. The latter in turn influences electronic structure and thus performance of the active layer. It is, however, highly challenging to determine molecular structure and folding properties in a bulk material. Here, it is shown that through the use of nanoparticles as a model system for the bulk material insight in molecular morphology can be gained through single particle fluorescence excitation spectroscopy. The study of P3HT chain morphologies was accomplished through the investigation of neat (0 wt% PCBM) P3HT nanoparticles and 25, 50 and 75 wt% PCBM blended P3HT nanoparticles. A striking discontinuous trend in P3HT chain morphology as a function of PCBM blending ratio was observed, where P3HT morphologies at 25 wt% and 75 wt% blending ratios appear to be more disordered than those observed for the 50 wt% blending ratio. These data suggest that at least from the morphological perspective, the 1:1 blending ratio appears to yield the better P3HT chain alignment. [Formula: see text]Special Issue Comment: This paper about solving single molecule conformations is related to the papers in this Special Issue on mathematical models for treatment of single molecule trajectories,1 nonblinking inorganic nanocrystals,2 and hybrid quantom dot–fullerence composite nanoparticles.3