Molecular electronic and photonic device

The LB deposition is one of the best methods to prepare highly organized molecular systems, in which various molecular parameters such as distance, orientation, extent of chromophore interaction, or redox potential can be controlled in each monolayer. We have been studying photophysical and photochemical properties of LB films in order to construct molecular electronic and photonic devices. The molecular orientation and interactions of redox chromophores are very important in controlling photoresponses at the molecular level. Absorption and fluorescence spectra give important information on them. We have studied photoresponses, specific interactions, and in-plane and out-of-plane orientation of various chromophores in LB films [3-11], In addition to the change of absorp-... 

Transition metal polypyridine complexes are highly redox-active, both in their electronic ground- and excited states. Their electron transfer reactivity and properties can be fine-tuned by variations in the molecular structure and composition. They are excellent candidates for applications in redox-catalysis and photocatalysis, conversion of light energy into chemical or electrical energy, as sensors, active components of functional supramolecular assemblies, and molecular electronic and photonic devices. 

The introduction of supramolecular multi-porphyrin assemblies is expected to contribute significantly to the field of molecular electronic and photonic devices because of their excellent levels of light absorption and charge sep-... 

C. W. Spangler, P.-K. Liu, and K. O. Havelka, The formation of charge states in organic molecules, oligomers and polymers for applications in molecular electronic and photonic devices, in Molecular Electronics and Molecular Electronic Devices, Vol. Ill (K. Sie-nicki, ed,), CRC Press, Boca Raton, FL, 1994, pp, 97-115. 

Heller, M. J. Utilization of synthetic DNA for molecular electronic and photonic-based device applications, in Lee, S. C. and Savage, L. (eds), Biological Molecules in Nanotechnology the Convergence of Biotechnology, Polymer Chemistry and Materials Science, IBC Press, Southborough, MA, USA, 1998, pp. 59-66. 

Polynuclear complexes, molecular dyads, triads, and other supermolecules composed of redox- and photo-active metal polypyridine units have a great promise as components of future molecular electronic or photonic devices as optical switches, relays, memories, etc. [38, 46],... 

The construction of intramolecular molecular system whose photo active molecule linked with conducting molecular wire is an important subject in realization of. molecular electronic or photonic devices. For such objectives, systematization of donor-photosensitizer-acceptor triad molecules into large molecular systems is one of the feasible approaches because the exquisite incorporation of the photosensitizer and a suitable electron donor and/or acceptor into a conducting polymeric chain is useful for various molecular systems based on the photoinduced electron transfer. With this in mind, we synthesized symmetrical donor-acceptor-donor triad molecules which can be polymerized by the normal electrochemical oxidation. By the polymerization, one-dimensional donor-acceptor polymers with porphyrin moieties separated by ordered oligothienyl molecular wire which is considered as a proto-type molecular device was obtained. 

From Table 2.3, which lists typical // values, it can be seen that the hole mobility in conjugated polymers is lower than that in organic crystals and amorphous silicon, but much larger than that in undoped poly(N-vinyl carbazole). Therefore, conjugated polymers have potential for applications in conducting opto-electronic and photonic devices. In principle, this also applies to liquid-crystal systems that can exhibit enhanced molecular order due to their self-organizing ability, as has been pointed out in a progress report [42]. 

Polymer electronics, including the use of polymer-nanocomposite-based devices, provide a number of alternative approaches, such as the use of adaptive circuits or the neural network-based processor architectures. Combined with a better understanding of the conductivity mechanism in conjugated polymers such as poly(acetylene) [2, 3] and poly(thiophenes) [4], these factors have initiated this second wave of interest in the low molecular weight organic and polymer-based optoelectronic, electronic and photonic devices. 

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

Champagne, B., Kirtman, B. Theoretical approach to the design of organic molecular and polymeric nonlinear optical materials. In Handbook of Advanced Electronic and Photonic Materials and Devices, vol. 9. Academic, San Diego (2001)... 

---