Methods of preparing Nano-particles.

1. TOP-DOWN AND BOTTOM-UP
APPROACHES
IGNTU AMARKANTAK
DEPARTMENT OF BIOTECHNOLOGY
Submitted By
Dileep Kumar Banjare
B.Sc. 5th Sem
Enrollment no. 17120006
Submitted To
Pooja Singh

2. TOP DOWN and BOTTOM UP APPROCHES
This is two different methods of design and
preparation of nano-particles with high
functionality.
The fabrication of nano-materials of tailored
properties involve the control of size, structure,
composition and purity of their constituents.
I,e to fabricate nano-materials which have the
suitable properties for application.

3. TOP-DOWN APPROACHES
The top down approach refers to slicing or successive
cutting of a bulk materials to get nano-sized particles.
In top down method or technique the starting
materials is solid state.
Nano-materials are synthesized by breaking down
bulk solid into nano-sized and provides desired shape
and order.

4. BALL MILLING METHOD
This method is popular, simple, inexpensive or
extremely scalable material to synthesize all classes of
nano-particle.
Can produce amorphous or nano-crystalline materials.
Can use either re-factory balls or steel balls or plastic
balls depending on the material to be synthesized.
When the balls rotate at particular rpm, the necessary
energy is transferred to the powder which in turn
reduce the powder of coarse grain sized structure to
ultrafine nano-range particles.

5. TOP-DOWN METHOD

6. The energy transferred to the powder from the balls
depends on many factors such as
1. Rotational speed of the balls.
2. Size of the balls.
3. Numbers of the balls.
4. Milling time.
5. Ratio of ball to powder mass.
6. Milling medium/atmosphere.
Cryogenic liquid can be used to increase the
brittleness of the product.

7. One has to take necessary step to prevent oxidation
during milling process.
The selection of ball material influence the type of
material obtained.
Alpha-alumina and zirconia are widely used ball
materials due to their high grinding resistance values.

8. ADVANTAGE and DISADVANATGE
 Screening can be
achieved up to tonnage
quantity materials for
wider application.
 Large scale production.
 Contamination of the
milling mill.
 Non metal oxides
requires an inert
medium and vacuum or
glove box to use powder
particles so this milling
process is re-constrictive.

9. BOTTOM-UP APPROACHES
Bottom-up approach refers to the build up of a
materials from the bottom : atom by atom, molecule
by molecule.
Atom by atom deposition leads to formation of self-
assembly of atoms/molecule and clusters.
This clusters come together to form self-assembled
monolayer on the surface of substrate.
All the bottom-up technique, the starting material is
either gaseous state or liquid state of matter.

10. BOTTOM-UP METHOD

11. NUCLEATION METHOD
Synthesis of nano-particles is a combination of two
stage process : Nucleation and Growth.
Most phase transformation begin with the formation
of numerous small particles (clusters) of the new
phase that increase in size until the transformation is
complete.
Nucleation is the process whereby nuclei (seeds) act
as template for crystal growth.

12. NUCLEATION

13. There are two different categories of nucleation
1. Heterogeneous nucleation
The nucleation of critical nuclei forming at defects
such as surface imperfection, grain boundaries is
called heterogeneous nucleation.
Nucleation is much easier since stable “Nucleating
Surface” is already present.
Requires slight super c0oling (0.1-10℃ )

14. 2. Homogenous
⃰ This happens spontaneously.
⃰ Nucleation that randomly occurs away from a
surface nuclei form uniformly throughout the parent
phase.
⃰ Requires considerable super-cooling (30-300℃)

15. ⃰ Super-cooling
During a cooling of a liquid solidification (nucleation) will
begin only after the temperature has been lowered below
the equilibrium solidification (or melting) temperature to
this phenomenon is termed super-cooling (under-cooling).
The driving force to nucleate increase as ΔT increases.
Small super-cooling → slow nucleation rate → few nuclei
→large crystal.
Large super-cooling →rapid nucleation rate →many nuclei
→small crystal.

16. ADVANTAGE and DISADVANATGE
 Ultra-fine nano-particles,
nano-shells, nano-tubes,
can be prepared.
 Deposition parameter
can be controlled.
 Narrow size distribution
is possible (1-20nm).
 Cheap technique.
 Large scale production is
difficult.
 Chemical purification of
nano-particles is
required.