The document discusses different methods for synthesizing nanomaterials, categorized as either top-down or bottom-up approaches. Top-down approaches like ball milling and electron beam lithography break down bulk materials into smaller structures but can result in surface imperfections. Bottom-up approaches like chemical synthesis build materials up atom by atom and molecule by molecule, allowing for controlled size and shape with fewer defects. Spark ablation is highlighted as a bottom-up method that produces pure metal nanoparticles through high-voltage sparks without needing further processing steps.

1. NANO MATERIALS SYNTHESIS
Top down and Bottom up approach
YOGESH T N 22ECR246

2. CONTENTS
1. Introduction
2. Quantum configurations
3. Needs for synthesis of nanomaterials:
4. Classification of techniques for synthesis of nanomaterials
a. Top- down approach
b. Electron beam lithography
c. Ball milling
d. Bottom–up approach.
e. Spark ablation method
5. Conclusion

3. INTRODUCTION
Nanotechnology is an emerging area of research which
has a potential in replacement of conventional micron
technologies and gives size dependent properties of the
functional materials. Let’s see the different
configurations of quantum structures and the methods
involved in their production in this presentation.

4. 01
02
03
Quantum well
If only one dimension of a three-dimensional
nanostructure is of nanoscale
Quantum wire
If two dimensions are of nanometer scale
Quantum dot
If all three dimensions are of nanometer
scale
QUANTUM CONFIGURATIONS

5. Need for synthesis of nanomaterials
Nanostructure materials have attracted a great deal of attention because their physical, chemical,
electronic and magnetic properties show dramatic change from higher dimensional counterparts and
depends on their shape and size.
• Many techniques have been developed to synthesize and fabricate nanostructure materials with
controlled shape, size, dimensionality and structure.
• The performance of materials depends on their properties. The properties in tern depend on the
atomic structure, composition, microstructure, defects and interfaces which are controlled by
thermodynamics and kinetics of the synthesis.
CLASSIFICATION OF TECHNIQUES FOR SYNTHESIS OF NANOMATERIALS
There are two general approaches for the synthesis of nanomaterials
a) Top- down approach
b) Bottom–up approach

6. Top-down approach
● Top-down approach involves the breaking down of the bulk
material into nanosized structures or particles.
● Top-down approaches are inherently simpler and depend either
on removal or division of bulk material or on miniaturization of
bulk fabrication processes to produce the desired structure
with appropriate properties.
● The major disadvantage with the top-down approach is the
imperfection of surface structure.
● For example, nanowires made by lithography are not smooth
and may contain a lot of impurities and structural defects on
its surface.
● Examples of such techniques are high-energy wet ball milling,
electron beam lithography, atomic force manipulation, gas-
phase condensation, aerosol spray, etc.

7. Ball milling
● Ball milling is a grinding method that grinds nanotubes into extremely fine
powders. During the ball milling process, the collision between the tiny rigid
balls in a concealed container will generate localized high pressure. Usually,
ceramic, flint pebbles and stainless steel are used.
● In order to further improve the quality of dispersion and introduce functional
groups onto the nanotube surface, selected chemicals can be included in the
container during the process.
● The factors that affect the quality of dispersion include the milling
time, rotational speed, size of balls and balls/ nanotube amount ratio.
● Under certain processing conditions, the particles can be ground to as small
as 100 nm.
● This process has been employed to transform carbon nanotubes into smaller
nanoparticles, to generate highly curved or closed shell carbon
nanostructures from graphite, to enhance the saturation of lithium
composition in SWCNTs, to modify the morphologies of cup-stacked carbon
nanotubes and to generate different carbon nanoparticles from graphitic
carbon for hydrogen storage application

8. Electron Beam lithography (EBL)
● Electron beam lithography (often abbreviated as e-beam
lithography or EBL) is the process of transferring a pattern onto
the surface of a substrate by first scanning a thin layer of
organic film (called resist) on the surface by a tightly focused
and precisely controlled electron beam (exposure) and then
selectively removing the exposed or nonexposed regions of the
resist in a solvent (developing).
● The process allows patterning of very small features, often
with the dimensions of submicrometer down to a few
nanometers, either covering the selected areas of the surface
by the resist or exposing otherwise resist-covered areas.
● The exposed areas could be further processed for etching or
thin-film deposition while the covered parts are protected
during these processes

9. Bottom-up approach
● The bottom – up approach has the potential of
creating less waste and hence the more
economical.
● Bottom-up approach refers to the build up of a
material from the bottom: atom-by-atom,
molecule-by-molecule, or cluster-by cluster.
● Examples of bottom – up approach are
oraganometallic chemical route, revere-micelle
route, sol-gel synthesis, colloidal precipitation,
hydrothermal synthesis, template assisted sol-
gel, electrodeposition etc,

10. Nanoparticles are traditionally synthesized using wet chemistry methods, which involve first
generating the particles in a solution, drop casting the wet particles onto a substrate, and
removing the solvent, surfactants, and other materials from the particles. This wet synthesis
method requires a significant amount of time and chemicals, and the resultant material may be
contaminated with residues from the solution.
Colloidal nanoparticle synthesis

11. Spark ablation nanoparticle synthesis
● One promising alternative to wet synthesis is
spark ablation. Spark ablation utilizes two
electrodes of the metal(s) of choice and
applies a fast (1-10 μs) high-voltage spark onto
the two electrodes. The spark produces an
aerosol of pure particles from the two ablated
metals, which are then transferred to a
downstream substrate. The resulting
nanoparticles are made of pure metal, and no
post-processing steps such as drying or
surfactant decomposition is required. Thus
spark ablation is a safer, greener, and more
economical way of producing high-quality
research or production-grade nanoparticles.

12. CONCLUSION
• A number of techniques have been explored to synthesis nanomaterials of desired size, shape,
orientation and these technical approaches can be grouped as Top-down and Bottom-up
approaches.
• These two approaches play very important roles in device industry as well in nanoproducts and
have their own merits and demerits.
• The biggest problem with top-down approach (physical methods) is the imperfection of the
surface structure.
• Such imperfections would have a significant impact on the physical and chemical properties of
nanostructures and nanomaterials.
• Among the top-down and bottom-up approaches, the bottom-up approach is more accepted in
synthesis of nanoparticles due to many merits as fewer defects, more homogenous chemical
composition and better ordering.
• It is found that the Gibbs free energy, thermodynamic equilibrium and kinetic methods are the
main strategies of nanoparticles synthesis in bottom-up approach.

13. THANK YOU!