Transcription of TOP DOWN AND BOTTOM UP APPROACHES - BDU OMS
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TOP DOWN AND BOTTOM UP APPROACHES - BDU OMS
Dr. G. Anand, M. R. Govt. Arts College, Mannargudi Page 1 TOP DOWN AND BOTTOM UP APPROACHES There are plenty of methods to synthesis nano materials. These methods are grouped into two categories namely Top-Down and BOTTOM -Up techniques. The techniques are classified based on the phase of the starting material. In the Top-down class of techniques, the starting material is in solid state, whereas in BOTTOM -Up techniques the starting material is either in gaseous state or in liquid state. Top-down approach refers to a subtractive process in which a bulk starting material is divided into smaller ones of nanosize. BOTTOM -up approach refers to an additive process that starts with precursor atoms (or) molecules which combine to form nanosized structure. In BOTTOM -up approach, nanostructures are built atom-by-atom or molecule-by-molecule. Depending on the requirement we have to select an appropriate method for prepration of nano materials.
intercluster separation is less than interplanar separation in graphite. In addition, there are sizable empty holes, which constitute 26% of the total cell volume, within the fcc C60 lattice. As fullerene molecule is highly electronegative, it readily forms compounds with electron donating atoms, the most common examples being alkali metals.
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