Assembling Photo- and Electroresponsive Molecules and Nano-Objects
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Photo- and Electroresponsive Molecules and Nano-Objects
Michael Busby, Luisa De Cola, Gregg S. Kottas, and Zoran Popovic′ Abstract The self-assembly of small molecules into large, functional nanostructures has led to the construction of supramolecular systems, both in solution and on solid substrates, with defined dimensions that display unique properties through collective interactions, much like natural systems. In this article, we show how one assembles photo- and electroluminescent molecules through coordination chemistry for the purpose of producing novel materials that can be used for displays and lighting applications. In a stepwise process, we discuss the design and synthesis of the components, their spectroscopic behavior, and finally the properties arising from the assembly. We then move from molecules to more complex systems such as zeolite L nano-objects that can be used as nanocontainers and functionalized in different ways. We show how it is possible to organize rods of micron length in a geometrically controlled manner in solution and on surfaces. The assemblies are built by coordinative bonds and are luminescent materials that can be constructed from fluorescent building blocks, with potential applications as optoelectronic materials, in analogy to their molecular counterparts.
Introduction The need to circumvent the expected physical limitations that the semiconductor industry will likely encounter (i.e., the inability to effectively pattern transistors at atomic or molecular dimensions) is a driving force in the broad field of nanotechnology. The desire is to solve this problem with the same apparent effortlessness with which nature constructs large, complex systems. The technique currently used in the semiconductor industry is known as the top-down approach, because large substrates are etched to form small features (analogous to a sculpture made from a block of marble). The bottom-up approach that drives nanotechnology is the antithesis to this
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and is concerned with the building up of these same features using small building blocks (i.e., atoms and molecules). Synthetic chemistry is a powerful technique for designing and preparing molecules and is a potential starting point for the bottom-up fabrication of bulk materials and complex interacting systems. However, for the construction of larger and more complex ensembles, such as those found in biology, it can be timeconsuming and impractical. Nature has solved this problem using self-assembly,1 which can be readily exploited for the bottom-up fabrication of new materials. Living systems synthesize relatively small components (e.g., nucleic acids) and
assemble them through cooperative interactions to produce superstructures that form the basis for life (e.g., DNA). The self-assembly strategy applied to artificial systems uses the ability of synthetic chemists to design building blocks (i.e., molecules) with variable chemical, physical, and structural properties. When these building blocks are combined and the functionalities of different
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