Nanoscale chemical structure clusters

Nanotechnology is the term generaly used to describe the creation and exploitation of materials with at least one dimension in the nanometer range (1-1000 nm). These include nanocrystals and clusters (quantum dots), nanowires, nanotubes, thin films and superlattices (3-Dimensional structures) [1,2]. Usually, nanostmctures have more reactive surfaces and exhibit new functions for the same chemical composition. Investigations of organization of matter at the nano-level are under way in many chemical systems with present and potential applications in nanotechnology. Recently, nanoscale stmctures were reported for the first time for actinide-containing compounds as well [3-6]. 

Little is known so far about the chemical properties, yet first results suggest a reactivity similar to that of multiwalled carbon nanotubes. Furthermore, a transformation of nano-onions into other forms of carbon can be achieved by heating (equihbration as faceted nanoparticles) or electron bombardment. In large carbon onions, a formation of small diamond clusters due to internal self-compression has been observed. These grow up to be nanoscale diamond particles under complete consumption of the onion structure. 

The definition above is a particularly restrictive description of a nanocrystal, and necessarily limits the focus of this brief review to studies of nanocrystals which are of relevance to chemical physics. Many nanoparticles, particularly oxides, prepared through the sol-gel method are not ineluded in this discussion as their internal structure is amorphous and hydrated. Nevertheless, they are important nanomaterials several textbooks deal with their synthesis and properties [4, 5]. The material science community has also contributed to the general area of nanocrystals however, for most of their applications it is not necessary to prepare fully isolated nanocrystals with well defined surface chemistry. A good discussion of the goals and progress can be found in references [6, 7, 8 and 9]. Finally, there is a rich history in gas-phase chemical physics of the study of clusters and size-dependent evaluations of their behaviour. This topic is not addressed here, but covered instead in chapter Cl.l. Clusters and nanoscale structures, in this same volume. 

The size-dependent evolutions of the structures and physical and chemical properties of nanoscale clusters have been subjects of continuing basic and applied research interests. Structure determination is one of the outstanding challenges of cluster... 

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