Inorganic nanocrystals with well defined shapes are important for understanding basic size-dependent scaling laws, and may be useful in a wide range of applications. Methods for controlling the shapes of inorganic nanocrystals are evolving rapidly. This talk will focus on a strategy that involves pyrolysis of organometallic precursos in mixtures of hot organic surfactants. The surfactant mixtures can be used to control the growth rates of differnet facets of the nanocrystals, allowing for wide tunability of shape. This will be illustrated with CdSe and Co nanocrystals. Both of these materials show pronounced variation of fundamental properties with aspect ratio. The nanorods can be aligned in a variety of ways. For instance, monolayers of surfacatant coated rod-like nanocrystals of these materials display a very rich phase diagram, analogous to the phases of liquid crystals. Block copolymers can be used to orient the rods. Finally, very special inorganic structures, tetrapods consisting of four rods at the tetrahedral angle, will always spontaneously align perpendicular to a surface. The possible application of these aligend nanorods in biological detection, photovoltaics, and light emitting diodes will be described briefly.
Molecular-Level Devices and Machines Vincenzo Balzani
Università di Bologna, ItalyA molecular-level device can be defined as an assembly of a discrete number of molecular components (that is, a supramolecular structure) designed to achieve a specific function. Each molecular component performs a single act, while the entire supramolecular structure performs a more complex function, which results from the cooperation of the various molecular components. Molecular-level devices operate via electronic and/or nuclear rearrangements, and like macroscopic devices they need energy to operate and signals to communicate with the operator. Light is the most important answer to this dual requirement, as shown by Nature where photons are used as energy by the devices responsible for photosynthetic processes and as signals by the devices responsible for vision-related processes. Another useful technique to cause and to monitor the occurrence of electronic and nuclear rearrangements in molecular and supramolecular systems is electrochemistry.In the last few years prototypes of very simple molecular-level machines and molecular-level components related to the construction of molecular-based (chemical) computers have been developed by several research groups. 1 Examples of molecular-level devices and machines investigated in our laboratory will be illustrated and discussed. For many applications manufactured surfaces with engineered structures in the nano-meter range are desirable. The properties of nucleic acids makes them a perfect material for this purpose: Nucleic acids have a regular structure with a 0.34 nm period, through its sequence it is addressable in a nanometer range.Technically we propose to immobilise DNA-oligomers on multiple points in an ordered way. It is important to retain its functional...