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The top-down approach is breaking down of a system into small components, while bottom-up is assembling sub-systems into larger system. [15] A bottom-up approach for nano-assembly is a primary research target for nano-fabrication because top down synthesis is expensive (requiring external work) and is not selective on very small length scales, but is currently the primary mode of industrial ...
A nanostructure is a structure of intermediate size between microscopic and molecular structures.Nanostructural detail is microstructure at nanoscale.. In describing nanostructures, it is necessary to differentiate between the number of dimensions in the volume of an object which are on the nanoscale.
There are two basic approaches to synthesizing nanowires: top-down and bottom-up. A top-down approach reduces a large piece of material to small pieces, by various means such as lithography, [5] [6] milling or thermal oxidation. A bottom-up approach synthesizes the nanowire by combining constituent adatoms. Most synthesis techniques use a ...
Several synthesis methods are known for SiNWs and these can be broadly divided into methods which start with bulk silicon and remove material to yield nanowires, also known as top-down synthesis, and methods which use a chemical or vapor precursor to build nanowires in a process generally considered to be bottom-up synthesis.
Self-assembly is a process which is easily influenced by external parameters. This feature can make synthesis rather complex because of the need to control many free parameters. Yet self-assembly has the advantage that a large variety of shapes and functions on many length scales can be obtained. [31]
Molecular self-assembly is a key concept in supramolecular chemistry. [6] [7] [8] This is because assembly of molecules in such systems is directed through non-covalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-stacking interactions, and/or electrostatic) as well as electromagnetic interactions.
The general idea behind top-down approaches is to take bulk h-BN, break the Van der Waals forces between the hexagonal layers and separate the resulting two-dimensional sheets of h-BN. These techniques mainly consist of mechanical and chemical exfoliation methods.
Nanochemistry is an emerging sub-discipline of the chemical and material sciences that deals with the development of new methods for creating nanoscale materials. [1] The term "nanochemistry" was first used by Ozin in 1992 as 'the uses of chemical synthesis to reproducibly afford nanomaterials from the atom "up", contrary to the nanoengineering and nanophysics approach that operates from the ...