| AVS 56th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Monday Sessions |
| Session NS+BI-MoM |
| Session: | Nanowires and Nanoparticles I |
| Presenter: | U.M. Mazur, Washington State University |
| Authors: | U.M. Mazur, Washington State University K.W. Hipps, Washington State University B.C. Wiggins, Washington State University B.A. Friesen, Washington State University |
| Correspondent: | Click to Email |
Synthetic porphyrins form excitonically coupled ring- and rod-shaped nanostructures, which are of interest for their potential applications in optoelectronic devices and solar cells. Nanorods produced from the sodium salt of tetrakis(4-sulfonatophenyl) porphyrin, TSPP, dissolved in acidic aqueous solutions, were deposited onto Au(111) substrates and were imaged by scanning probe microscopy. Ambient and UHV scanning tunneling microcopy, STM, images revealed individual rods with diameters of 25-40 nm and lengths of hundreds of nanometers. High resolution STM images of TSPP on Au(111) showed that the rods are composed of disk-like building blocks approximately 6.0 nm in diameter. We speculate that the disks are formed by a circular J-aggregation of 14-16 overlapping electronically coupled porphyrin chromophores and that this circular porphyrin organization is driven by nonplanar distortions of the porphyrin diacid. X-ray photoelectron spectroscopy, XPS, was employed to investigate the structural changes in TSPP associated with the protonation of the porphyrin ring and aggregation. Scanning tunneling spectroscopy, STS, results indicate high conductivity of TSPP nanorods that can be attributed LUMO based conductivity in the nanorods.
Our results shed light not only on the structural model for TSPP basic aggregate unit but also on the conduction mechanism within the TSPP nanorod structure.