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Self Assembling of Porphyrin-Fullerene Dyads in the Langmuir and Langmuir-Blodgett Films: Formation as well as Spectral, Electrochemical and Vectorial Electron Transfer Studies

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Abstract:

Donor–acceptor dyads of water-soluble Zn porphyrins and C60 bearing either pyridine or imidazole ligand were self assembled via axial coordination in Langmuir and Langmuir-Blodgett (LB) films. Compression and surface potential versus area per molecule isotherms as well as ellipsometry and BAM measurements showed that molecules were aggregated in all Langmuir films before compression. The area per molecule in the absence of aggregation was determined by linear extrapolation of the area at the zero surface pressure to infinite adduct dilution. Comparison of the extrapolated and theoretically calculated areas, being dependent on the composition of the subphase solution, indicated that dyads were oriented with their porphyrin macrocycles in plane of the air–solution interface. Calculated by molecular modeling thickness of the Langmuir films was in accord with that determined by ellipsometry. The Langmuir films were transferred, by using the LB technique, onto different solid substrates for spectroscopic, microscopic, electroanalytical, and photochemical characterization. From the IR spectroscopy investigations it followed that the porphyrin macrocycle of the dyad was either nearly parallel or tilted with respect to the substrate plane. Molecularly modeled pseudo-hexagonal packing and thickness of the LB films were in accord with that imaged by STM and determined by ellipsometry, respectively. The electrochemical redox states of the dyads were established by performing simultaneous cyclic voltammetry and piezoelectric microgravimetry mea surements of the LB films on Au-quartz electrodes. Both steady-state and time-resolved emission studies of the zinc porphyrin-fullerene LB films revealed efficient quenching of the singlet-excited Zn porphyrin. Based on the free-energy calculations and dyad orientation in the film, this quenching was attributed to vectorial electron transfer within the dyad.

Keywords: DONOR-ACCEPTOR SUPRAMOLECULAR DYADS; LANGMUIR AND LANGMUIR-BLODGETT FULLERENE FILMS; SOLUBLE ZINC PORPHYRINS; VECTORIAL ELECTRON TRANSFER; [60]FULLERENE IMIDAZOLE ADDUCTS; [60]FULLERENE PYRIDINE ADDUCTS

Document Type: Research Article

DOI: https://doi.org/10.1166/jnn.2007.328

Publication date: 2007-04-01

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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