The document discusses various methods for synthesizing nanomaterials, including top-down and bottom-up approaches. Top-down approaches begin with bulk materials and make them smaller through processes like lithography or milling. Bottom-up approaches build materials up from atomic or molecular levels using chemical synthesis or self-assembly. Specific bottom-up methods discussed include sol-gel processing, chemical vapor deposition, and chemical reduction of metal salts to produce colloidal nanoparticles. The document compares advantages and limitations of different nanomaterial synthesis techniques.

1. INTRODUCTION TO
NANOMEDICINE
TOPIC:SYNTHESIS OF NANOMATERIALS
ANANTHAKUMAR.T
BMS14312
IV YEAR

2. INTRODUCTION
• Materials scientists are conducting research to
develop novel materials with better
properties, more functionality and lower cost
than the existing one.
• Several physical, chemical methods have been
developed to enhance the performance of
nanomaterials displaying improved properties
with the aim to have a better control over the
particle size, distribution

3. Methods to Synthesis of
Nanomaterials
• In general, top-down and bottom-up are the
two main approaches for nanomaterials
synthesis.
• a. Top-down: size reduction from bulk
materials.
• b. Bottom-up: material synthesis from atomic
level.

4. TOP-DOWN
• Top-down routes are included in the typical
solid –state processing of the materials.
• This route is based with the bulk material and
makes it smaller, thus breaking up larger
particles by the use of physical processes like
crushing, milling or grinding.

5. Cont..
• Usually this route is not suitable for preparing
uniformly shaped materials, and it is very difficult
to realize very small particles even with high
energy consumption.
• The biggest problem with top-down approach is
the imperfection of the surface structure.
• Such imperfection would have a significant
impact on physical properties and surface
chemistry of nanostructures and nanomaterials.

6. Top-Down: lithography
• At the moment, the most used top-down
approach is photolithography.
• It has been used for a while to manufacture
computer chips and produce structures
smaller than 100 nm.
• Typically, an oxidized silicon (Si) wafer is
coated with a 1µm thick photoresist layer.

7. Cont..
• After exposure to ultraviolet (UV) light, the
photoresist undergoes a photochemical
reaction, which breaks down the polymer by
rupturing the polymer chains.
• Subsequently, when the wafer is rinsed in a
developing solution, the exposed areas are
removed.

9. NANOLITHOGRAPHY
• Nanolithography is the branch of nanotechnology
concerned with the study and application of
fabricating nanometer-scale structures, meaning
patterns with at least one lateral dimension
between 1 and 100 nm
• It comes from the Greek word “nanos” meaning
dwarf and “graphene” meaning to write.
• It is a very active area of research in academia
and in industry.

10. WORKING
• It used for further fabrications of nanometer
materials and molecules.
• Two of most important instruments used in
the nanolithography processing are
• Scanning Probe Microscope (SPM)
• Atomic Force Microscope (ATM)

11. TYPES
• Optical nanolithography (EUV)
• X-ray Nanolithography
• Electron beam lithography
• Nanoimprint lithography (NIL)
• Multiphoton lithography
• Scanning probe lithography
• Charged-particle lithography
• Neutral Particle Lithography
• Atomic Force Microscopic Nanolithography

12. OPTICAL NANOLITHOGRAPHY
• Traditional method of lithography
• It is a technique for patterning the various
surfaces and have the capability for producing
sub patterns up-to to 100 nm with minor wave
lengths.
• Optical nanolithography requires the use of
liquid immersion and resolution host.
• Most cost effective method of lithography

13. X RAY NANOLITHOGRAPHY
• It is quite different from traditional X-ray
lithography.
• It has the ability to improve and extend optical
resolution of 15 nm by using the short
wavelengths of 1 nm for the illumination.
• This is performed by printing approach and is
used for batch processing.
• It consists of 3 elements-A mask consisting of a
pattern made with an X ray absorbing material on
a thin x ray transparent membrane, an X ray
source, an X ray sensitive resist material

15. Cont..
• It is the most famous nanolithography
method which makes use of electron beam to
draw a pattern.
• It is mostly used in the polymers to obtain
different patterns of polymeric structures

16. Electron Beam Lithography (EBL)
• Electron Beam Lithography (EBL) uses a tightly
focussed beam of electrons scanned over the
surface of a substrate to etch a pattern of
nano sized features.
• EBL can produce features as small as 20nm
but is very expensive and time consuming.
• For example a lithographic process that would
take 5 minutes using photolithography would
take approximately 5 hours using EBL.

17. Nanoimprint lithography
• Nanoimprint lithography is a simple process that uses a
mould to emboss the resist with the required pattern.
• After embossing the resist, compressed resist material
is removed using anisotropic etching and the substrate
exposed.
• Nanoimprint lithography can give resolutions lower
than 10nm with high throughput and low cost.
• The current barrier to production at these resolutions
is the development of the mould itself.
• Nanomanufacturing using self assembly may hold the
solution to this hurdle.

18. Scanning Probe Microscope
Lithography (SPM)
• Scanning Probe Microscope Lithography (SPM)
uses the electric field at the tip of a scanning
probe microscope to oxidise material in a
specific pattern.
• The oxidised material can then be removed
by preferential etching

19. Chemical Vapor Deposition (CVD)
• This process is often used in the semiconductor
industry to produce high-purity, high-
performance thin films.
• In a typical CVD process, the substrate is exposed
to volatile precursors, which react and/or
decompose on the substrate surface to produce
the desired film.
• Frequently, volatile by products that are
produced are removed by gas flow through the
reaction chamber.

20. Cont.
• The quality of the deposited materials strongly
depends on the reaction temperature, the
reaction rate, and the concentration of the
precursors.
• Cao et al. prepared Sn4+-doped TiO2
nanoparticles films by the CVD method and
found that more surface defects were present
on the surface due to doping with Sn .

21. Cont..
• Gracia et al.synthesized M (Cr, V, Fe, Co)-
doped TiO2 by CVD and found that TiO2
crystallized into the anatase or rutile
structures depending on the type and amount
of cation present in the synthesis process
• Moreover, upon annealing, partial segregation
of the cations in the form of M2On was
observed.

22. Cont..
• The advantages of this method include the
uniform coating of the nanoparticles or nano
film.
• However, this process has limitations including
the higher temperatures required, and it is
difficult to scaleup .

23. Bottom –up
• Bottom –up approach refers to the build-up of
a material from the bottom: atom-by-atom,
molecule-by-molecule or cluster-by-cluster.
• This route is more often used for preparing
most of the nano-scale materials with the
ability to generate a uniform size, shape and
distribution.

24. Cont.
• It effectively covers chemical synthesis and
precisely controlled the reaction to inhibit
further particle growth.
• Although the bottom-up approach is nothing
new, it plays an important role in the
fabrication and processing of nanostructures
an nanomaterials.

25. Cont..
• Synthesis of nanoparticles to have a better
control over particles size distribution,
morphology, purity, quantity and quality, by
employing environment friendly economical
processes has always been a challenge for the
researchers

26. SOL-GEL METHOD
• Two types of materials or components- “sol”
and “gel”
• M. Ebelman synthesized them in 1845
• Low temperature process- less energy
consumption and less pollution Generates
highly pure, well controlled ceramics
• Economical route, provided precursors are not
expensive Possible to synthesize
nanoparticles, nanorods, nanotubes etc.,

27. Cont..
• Sols are solid particles in a liquid- subclass of
colloids
• Gels – polymers containing liquid
• The process involves formation of ‘sols’ in a
liquid and then connecting the sol particles to
form a network
• Liquid is dried- powders, thin films or even
monolithic solid Particularly useful to
synthesize ceramics or metal oxides

29. Cont..
• The precursors for synthesizing these colloids
consist : -
• metal alkoxides e.g: tetramethoxysilane
(TMOS) and tetraethoxysilane (TEOS)
• Metal chlorides
• They readily react with water.
• Three reactions are generally used to describe
the sol-gel process: - hydrolysis –
condensation-polycondensation

30. Cont..
• For ex: in SiO₄, Si is at the centre and 4 oxygen
atoms at the apexes of tetrahedron
• Very ideal for forming sols
• By polycondensation process sols are
nucleated and sol-gel is formed

33. Application of Sol-Gel
• Protective Coatings
• Thin film and fibers
• Nanoscales powder
• Opto-mechanical

34. Advantages
• Cheap and low temperature operation
• Very thin of metals oxide can be obtained
• Better alternative approach to conventional
production of glasses
• Sol gel material can be obtained as bulks, thin
films (nano) powders

35. CHEMICAL METHODS OF SYNTHESIS
• Advantages
• Simple techniques
• Inexpensive instrumentation
• Low temperature (<350ºC) synthesis
• Doping of foreign atoms (ions) is possible during
synthesis
• Large quantities of material can be obtained
Variety of sizes and shapes are possible
• Self assembly or patterning is possible

36. COLLOIDS AND COLLOIDS IN
SOLUTION
• Nanoparticles synthesized by chemical methods
form “colloids”
• Two or more phases (solid, liquid or gas) of same
or different materials co-exist with the
dimensions of at least one of the phases less than
a micrometre
• May be particles, plates or fibres
• Nanomaterials are a subclass of colloids, in which
the dimensions of colloids is in the nanometre
range

38. SYNTHESIS OF METAL NANOPARTICLES
BY COLLOIDAL ROUTE
• Reduction of some metal salt or acid
• Highly stable gold particles can be obtained
by reducing chloroauric acid
• Metal gold nanoparticles exhibit intense red,
magenta etc., colours depending upon the
particle size

40. Cont..
• Gold nanoparticles can be stabilised by
repulsive Coloumbic interactions
• Also stabilised by thiol or some other capping
molecules
• In a similar manner, silver, palladium, copper
and few other metal nanoparticles can be
synthesized.