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U. S. Behera and J. S. Sangwai
which produces a strong thermal plasma discharge. The discharge process leads to
raising the temperature of about thousand of degrees Celsius which vaporized the
electrode surfaces in the solvent medium. The vaporized metal gets condensed giving
nanoparticles.
Bottom-up Process
It is the process in which nanoparticles are formed from much smaller particles such
as atoms and hence also known as building up approach. This process involved in
producing the uniform size and required property of nanoparticles which is otherwise
quite difficult to produce in mechanical milling process of the top-down approach.
Chemical vapor decomposition (CVD), spinning, sol–gel, and biosynthesis are the
most commonly used processes which come under the bottom-up approach.
Chemical Vapor Deposition
In chemical vapor deposition, a thin layer of vapor is accumulated on the surface of
the solid substrate. The whole process of deposition is carried out inside the reactor
at ambient temperature. Initiation of a chemical reaction is observed when a heated
substrate comes in contact with the vapor. At the end of the reaction, a thin film of
nanoparticles is deposited on the solid surface, then the nanoparticles are separated,
which are found to be uniform, pure, hard and strong (Ealias and Saravanakumar
2017).
Spinning
In this process, synthesis of nanoparticles is done inside the reactor containing a
spinning disc under the control of the affecting factor such a temperature. The reactor
is packed with nonreacting gases like N 2 to avoid any reaction. The disc is rotated
at a variable speed in the presence of precursor and water. The rotation causes the
particle agglomerate and precipitate is formed. The precipitate is collected and dried
(Mohammadi et al. 2014). Other parameters such as liquid flow rate, rpm of the disc,
liquid precursor ratio, disc surface area, etc. determine the properties of nanoparticles.
Electrospinning is a kind of method used to produce a thin sheet of polymer fiber.
Sol–Gel
Sol–gel is the old industrial process for the production of colloidal nanoparticles
from the liquid phase. The sol–gel process is mostly used for generation of oxide
nanoparticles and composite nonmaterial. It is the most preferred bottom-up approach
to create nanoparticles due to its ease of operation. Sol is a colloidal solution of
U. S. Behera and J. S. Sangwai
which produces a strong thermal plasma discharge. The discharge process leads to
raising the temperature of about thousand of degrees Celsius which vaporized the
electrode surfaces in the solvent medium. The vaporized metal gets condensed giving
nanoparticles.
Bottom-up Process
It is the process in which nanoparticles are formed from much smaller particles such
as atoms and hence also known as building up approach. This process involved in
producing the uniform size and required property of nanoparticles which is otherwise
quite difficult to produce in mechanical milling process of the top-down approach.
Chemical vapor decomposition (CVD), spinning, sol–gel, and biosynthesis are the
most commonly used processes which come under the bottom-up approach.
Chemical Vapor Deposition
In chemical vapor deposition, a thin layer of vapor is accumulated on the surface of
the solid substrate. The whole process of deposition is carried out inside the reactor
at ambient temperature. Initiation of a chemical reaction is observed when a heated
substrate comes in contact with the vapor. At the end of the reaction, a thin film of
nanoparticles is deposited on the solid surface, then the nanoparticles are separated,
which are found to be uniform, pure, hard and strong (Ealias and Saravanakumar
2017).
Spinning
In this process, synthesis of nanoparticles is done inside the reactor containing a
spinning disc under the control of the affecting factor such a temperature. The reactor
is packed with nonreacting gases like N 2 to avoid any reaction. The disc is rotated
at a variable speed in the presence of precursor and water. The rotation causes the
particle agglomerate and precipitate is formed. The precipitate is collected and dried
(Mohammadi et al. 2014). Other parameters such as liquid flow rate, rpm of the disc,
liquid precursor ratio, disc surface area, etc. determine the properties of nanoparticles.
Electrospinning is a kind of method used to produce a thin sheet of polymer fiber.
Sol–Gel
Sol–gel is the old industrial process for the production of colloidal nanoparticles
from the liquid phase. The sol–gel process is mostly used for generation of oxide
nanoparticles and composite nonmaterial. It is the most preferred bottom-up approach
to create nanoparticles due to its ease of operation. Sol is a colloidal solution of