Nanoscale molecules

Nanoscale molecules and molecular assemblies are being used more and more frequently as they reduce costs and use fewer resources. In order to be able to analyze and characterize these materials, new techniques have to be developed or refined. This two-volurne work brings together the knowledge from research and from industry of molecular nano dynamics. The topics are clearly divided into five parts over the 2 volumes, which focus on different topics. 

Materials synthesis is a necessary component in the development of advanced technologies for national security and homeland defense. For instance, new composites, nanoscale molecules and compounds, and polymers are needed for tougher, explosion- or puncture-resistant materials that can be employed in buildings, garments, bridges, and other products and structures. Personal protective materials could be enhanced with new chemical adsorbents filter materials, impermeable membranes, artificial sutures, and improved energetic materials for... 

The 1,2,5-dithiazepine 386, upon reaction with the adamantane 389, gave the symmetrically tetrasubstituted adamantane 391, whereas 386 and 388 upon treatment with 390 afforded the tetraphenylmethane 392 and its larger analogue 393 (Scheme 81). Similar procedures were adopted in synthesizing other tetrahedral-shaped nanoscale molecules <2003JOC4862>. 

Dendrimers are seen to have applications in medicine, especially in diagnostics [57 a]. Apart from good solubility in water, the possibility of introducing multiple special functionalities into the periphery of the nanoscale molecules permits high sensitivity to be attained and variation of the parameters over a wide range as required by the prevailing conditions. 

This award is considered to have generated a new field known as nanotechnology, as worldwide exposure was instantly aware of these nanoscale molecules, and other developments in this size regime were found shortly thereafter. It should be noted that the discovery of dendrimers by Denkwalter and coworkers from AlUed Corporation was disclosed in 1981, 4 years before bucky balls were discovered. It may be expected that these nanopolymeric materials will be extremely influential toward the nanotechnology revolution (see Chapter 5 for more information on dendritic materials). 

Some of the critical length scales of circuits that can now be fabricated, such as the diameter of the wires and the interwire separation distance (or pitch), are more commonly associated with biological macromolecules, such as proteins, mRNA oligonucleotides, and so on, than with electronics circuitry. In fact, one unique application of nanoscale molecule-electronics circuitry, and perhaps the... 

The hot topics on the physics of liquid crystals shown in this chapter have the ke)word nano (molecular scale) in common. It has been a big challenge for us to build a bridge between the nanoscale molecules and their macroscopic properties. Hopefully the remarkable works introduced in this chapter will give us some clues on how we can contribute to the bridge constraction, how fast and which direction the physics of liquid crystals will go in the future. 

The most recent approach to reductive nanofabrication that can indeed constmct nanoscale stmctures and devices uses microscopic tools (local probes) that can build the stmctures atom by atom, or molecule by molecule. Optical methods using laser cooling (optical molasses) are also being developed to manipulate nanoscale stmctures. 

Despite advances, it seems unlikely that the reductive approaches outlined above can, by themselves, teach the level of control, fiexibiUty, discrimination, and versatiUty of atomic and molecular manipulation that will be needed to manufacture the molecular and suptamoleculat nanodevices envisaged to be the products of nanotechnology. Studies of biological nanodevices (eg, proteins) suggest that under proper conditions, atoms and molecules can assemble into functional nanoscale units that can carry out all the functions of life. 

Nanomaterials can be manufactured by one of two groups of methods, one physical and one chemical. In top-down approaches, nanoscale materials are carved into shape by the use of physical nanotechnology methods such as lithography (Fig. 15.30). In bottom-up approaches, molecules are encouraged to assemble themselves into desired patterns chemically by making use of specific... 

For a flying height around 2 nm, collisions between the molecules and boundary have a strong influence on the gas behavior and lead to an invalidity of the customary definition of the gas mean free path. This influence is called a "nanoscale effect" [46] and will be discussed more specifically in Chapter 6. 

Tools shape how we think when the only tool you have is an axe, everything resembles a tree or a log. The rapid advances in instrumentation in the last decade, which allow us to measure and manipulate individual molecules and structures on the nanoscale, have caused a paradigm shift in the way we view molecular behavior and surfaces. The microscopic details underlying interfacial phenomena have customarily been inferred from in situ measurements of macroscopic quantities. Now we can see and fmgeT physical and chemical processes at interfaces. 

Nanotechnology is the branch of engineering that deals with the manipulation of individual atoms, molecules, and systems smaller than 100 nanometers. Two different methods are envisioned for nanotechnology to buUd nanostructured systems, components, and materials. One method is the top-down approach and the other method is called the bottom-up approach. In the top-down approach the idea is to miniaturize the macroscopic structures, components, and systems toward a nanoscale of the same. In the bottom-up approach the atoms and molecules constituting the building blocks are the starting point to build the desired nanostmcture [96-98]. 

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