Nanotechnology The Top Down and Bottom Up Approaches

Foster, L. E., Nanotechnology Science, Innovation, and Opportunity, Prentice Hall Upper Saddle River, NJ, USA, 2005. 

Supramolecular Chemistry, 2nd edition J. W. Steed and J. L. Atwood 2009 John Wiley Sons, Ltd ISBN 978-0-470-51233-3 

Study of nanoscale biological systems and phenomena, the use of biological components in nanotechnological applications and the synthesis or construction of nanometre scale mimics of biological entities. Examples include the use of DNA for molecular computing, or as a nanoscale structural scaffold, and the temptation of nanostructures using bacterial S-layers (Section 14.6.2). With these ideas in mind we turn first to templated morphosynthesis the chemical synthesis of nanoscale morphologies that often mimic complex structures found in the Natural world. 

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Nanostructures are being constructed by either bottom-up or top-down approaches for various applications ranging from microelectronics to protein microarrays (see Nanotechnology The Top-Down and Bottom-Up Approaches, Nanotechnology). From the bottom-up, AFM is an ideal tool in studying the self-assembly and selforganization of molecules on a surface. Tapping mode... 

Table 1.1 summarizes the types of processes for generating nanoparticles that are currently involved in the top-down and bottom-up approaches (or their mixed variants). It should be noted that many of these processes have their origin and primary applications predominantly in the pharmaceutical industry so far the commercial food applications of nanotechnology are still in their infancy. For each of the processes mentioned in Table 1.1, the kinds of nanoparticles involved are listed along with a brief indication of their characteristic properties and their approximate particle dimensions. Also presented are some recent literature sources on these various topics (mainly review-type articles) where the interested reader can obtain further background material. 

This article provides an overview of nanotechnology, describing the origins of the field, present technology, ongoing research, and future aspirations. In addition, the two possible methodologies of fabrication—the top-down and bottom-up approaches—are discussed, covering the merits and drawbacks of each approach. 

The engineering of materials at the nanoscale level with novel properties, through controlled synthesis and assembly, is an important issue. In recent years, nanotechnology has reached a stage whereby it is possible to produce, characterize and specifically tailor, the functional properties of nanoparticles. Nanoparticle synthesis has been pursued intensively not only for fundamental scientific interest but also for many technological applications [16, 30, 55-58], and the synthesis of uniformly sized (or monodisperse) nanoparticles has become a very important research area [59-63]. The two fundamentally different approaches used to synthesize nanomaterials are known as top-down and bottom-up ... 

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... 

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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