2. Table of Contents
1. Nanoparticles synthesis
2. Dry Synthesis(Physical
method/Top-Down ) Method
3. Wet based method
4. Characterisation of
Nanomaterials
3. Nanoparticles
synthesis
Two approaches can be
taken when making
something at the nano scale
1. Top Down approach
2. Bottom Up approach
Top Down approach(dry production method) Bottom Up approach(wet production method)
Breaking Down matter into more basic building blocks
.Frequently uses chemical and thermal method
Building Complex system by combining simple
atomic-level components
Top Down fabrication is often more easiily
accomplished using Proven techniques ,but a lot of
material wasted
Less wastage,as strong covalent bonds will hold the
constituent parts together
Top-down approaches, like lithography, can cause
significant crystallographic damage and introduce
additional defects during the etching process, making
surface structure imperfection a major issue.
Bottom-up approach also promises a better
chance to obtain nano- structures with less
defects, more homogeneous chemical
composition, and better short and long range
ordering
Formation of variable nano-sized particles Size and shape of Nano-Particles can be controlled
Eg:-Attrition ,milling Eg:-colloidal dispersion ,etching
5. Ball Milling(Mechanical)
• Reactant powder (50 um particle) are introduced typically in a sealed vial
with hardened steel coated balls.
• The milling is performed by shaking and violent agitation (Fig.). The vial is
filled with gas (often inert).
• The powder is splitted and exposed highly reactive surfaces.
• The severe plastic deformation due to violent agitation leads to nanometer-
scale structures of the powder.
• Production of NPs using ball milling may involve a significant amount of
solvent (water, solvents (n-butyl acetate, acetone, ethyl acetate etc.) during
particle size reduction.
• Addition of fluid inside the mill can moderate the mechanical shock and
minimize the amorphization of the material (e.g., graphite) and reagent
• Also used for the synthesis of alloys, nano-composites
• Intermetallic materials: TisAls NPs, Fe-C alloy NPs, Pd NPs, ZnO NP, Mg-Ti-C
nanocomposite can be synthesized
6. Gas phase synthesis:
Gas-phase synthesis of NPs could be divided into two categories.
First category Second category
To fabricate NP the first category consists
of solid precursors used ir
• inert-gas condensation
• laser ablation,
• spark discharge, and
In the second category, liquid and vapor
precursors are used in coniunction with
• Combustion Flame Synthesis:
• spray and laser pyrolysis,, flame
pyrolysis, or
• Plasma processing
Evaporation Techniques
7. Inert-Gas
Condensation
• Used to synthesize numerous metallic, compound, and oxide NPs like
manganese (Mn) nanoparticles, Nickel (Ni) nanoparticles, iron and iron
oxide nanoparticles and size-controlled gold/palladium nanoparticles
(Au/Pd NPs).
• The evaporation is done by thermal evaporation, laser evaporation,
sputtering, electric Arc discharge and plasma heating.
• The first step involves the evaporation of the material and the second
is the rapid condensation of the evaporate material to favor the
particle size and morphology.
• The inert gas is condensed in a condensation devices whose pressure
is evacuated to fall down to 2 × 10-6 Torr using a diffusion pump
• After the evacuation is done, inert gases like He, Xe, or Ar are leaked
into the chamber with lower pressures of about 0.5 to 4 atm. with the
subsequent fast heating of chamber at constant temperature and
inert gas pressure.
• At this point, the particles with ultrafine sizes that are formed in the
inert gas phase are collected in a surface that is cooled by water.
8. Combustion Flame Synthesis
• A couple of million tons of carbon black, silica, and titania are produced annually
• The combustion heat can activate a number of reactions such as oxidation, hydrolysis, pyrolysis, and reduction,
which can be manipulated based on precursors used and the flame environment.
• Widely used to synthesize small oxide particles from redox oxides.
• Flame heat is used to initiate nucleation of both aerosol and "non- aerosol" precursors.
• The precursors consist of redox mixtures.
• The reducing agent (fuel) is an organic compound such as urea, citric acid, or PVA (polyvinyl alcohol) polymer.
• The oxidizing agent is a metal salt such as nitrate. After ignition using an external source, the precursor mixture
burns via an exothermic redox reaction to form the product.
• The presence of a large volume of gas formed after the combustion induces disintegration of large particles into
IPs.
9. Chemical Vapor
Deposition (CVD)
• The chemical vapor deposition method
• (CVD) involves a chemical reaction.
• The method involves one or more volatile precursors
• The substrate is exposed to those precursors that decompose on it and form the
desired deposit.
• The vaporized precursors are inserted into a CVD reactor and adsorb onto a
substance being placed at high temperature.
• The molecules that get adsorbed react with other molecules or decompose to
form crystals.
• Homogeneous nucleation occurs in gas phase and heterogeneous nucleation
happens in a substrate.
• The reaction can be controlled to produce nanoparticles of size ranging from 10
to
• 100 nm
• The three steps in CVD method are:
• 1. Reactants are transported on the growth surface by a
boundary layer.
• 2. Chemical reactions occur on the growth surface.
• 3. Byproducts produced by the gas-phase reaction has to be
removed from the surface.
10. Different Wet-based Method(Bottom Up approach)
I. Wet-based techniques provide the simplest approach to produce small and monodispersed partices
II. These methods are often classified on the basis of either the source of energy or size selection
III. The following methods are generally used:
1. Polyol Method
2. Microemulsion method
3. Sol-gel method
4. Thermal decomposition
5. Hydrothermal
The Polyol Method-:
• This method uses non-aqueous liquid (polyol) (e.g., ethylene glycol, polyethylene glycol, and diethylene glycol) as a
solvent and reducing agent
• Metal, metal oxide nanoparticles, synthesis of bimetallic alloys and core-shell nanoparticles are widely synthesized by
Polyo method
• It involves the reduction of a precursor (such as metal salt) by ethylene glycol at elevated temperatures in the presence of
poly (vinyl pyrrolidone) (or PVP).
• The trace amounts of additives has a dramatic effect on the synthetic pathways, as well as on the morphologies of both
nuclei and products of NP
.
11. Microemulsion Method
• Microemulsion is the thermodynamically stable isotropic dispersal of two immiscible water and oil phases in the
presence of a surfactant.
• The surfactant molecules can form a monolayer at the interface between the oil and water, with the hydrophilic head
aroups in the aqueous phase and the hydrophobic tails of the surfactant molecules dissolved in the oil phase
• The properties of NPs prepared by the microemulsion method depend on the type and structure of the surfactant.
The Sol-gel Methods
• The sol-gel method is a proper wet route for the preparation of nanostructured metal oxides.
• This method is based on the hydroxylation and condensation of molecular precursors in solution, initiating a "sol" of
nanometric particles.
• Additional condensation and inorganic polymerization lead to a three-dimensional metal oxide network, denominated as
wet gel.
• Extra heat treatments are needed to obtain the final crystalline state, because these reactions are performed at room
temperature.
• The sol-gel process includes hydrolysis and condensation of metal alkoxides.
• Metal alkoxides are good precursors, due to their endurance in the face of hydrolysis, i.e. the hydrolysis step replaces an
alkoxide with a hydroxide group from water and a free alcohol is generated.
• Factors that need to be considered in a sol-gel method are the solvent type, temperature, precursors, catalysts, pH,
additives and mechanical agitation.
12. Hydrothermal synthesis :-Hydrothermal synthesis is an artificial method for synthesizing single-crystal nanoparticles using
high vapor pressure and high-temperature aqueous solutions. This process requires a Hydrothermal Autoclave Reactor, a
strong vessel designed to withstand high temperatures and pressure levels. The autoclave is made of thick, steel-walled
cylindrical vessels with hermetic sealing, and must be resistant to solvents. Special protective coatings are applied to prevent
corrosion, typically made of gold, platinum, silver, carbon-free iron, titanium, glass or copper, and Teflon. The specific
protective layer depends on the solution and temperature used in the hydrothermal synthesis method.
Thermal Decomposition:-
• Nanoparticles with a high level of monodispersity and size control can be achieved by high-temperature
decomposition of organometallic precursors, or carbonyls using organic solvents and surfactants. Generally metal oxide
nanoparticles are produced by this method.
• In principle, the ratios of the starting reagents including organometallic compounds, surfactant, and solvent are the
decisive parameters for the control of the size and morphology of magnetic nanoparticles.
• The reaction temperature, reaction time, are crucial for the precise control of size and morphology.
13. Characterisation of Nanomaterials
• Nanomaterials & Nanostructures are characterized by:
• X-ray diffraction (XRD)
• Small angle X-ray scattering (SAXS)
• Various Electron Microscopy (EM)
• Scanning Electron Microscopy (SEM)
• Transmission Electron Microscopy (TEM)
• Gas adsorption
• Chemical Characterization Techniques
• Optical Spectroscopy
• Electron Spectroscopy
• Ionic Spectrometry
14. • XRD is a crucial experimental technique used to analyze solid crystal structure.
• It addresses issues related to lattice constants, geometry, identification of unknown materials,
orientation of single crystals, preferred orientation of polycrystals, defects, and stresses.
• X-rays, incident on a specimen, are diffracted by the crystalline phases according to Bragg's law.
• The intensity of the diffracted X-rays is measured as a function of the diffraction angle and the
specimen's orientation.
• XRD is nondestructive and does not require elaborate sample preparation, making it widely
used in materials characterization.
• XRD accurately measures diffraction peak positions, making it ideal for characterizing
homogeneous and inhomogeneous strains.
• Homogeneous strain shifts the diffraction peak positions, calculating the change in d-spacing.
• Inhomogeneous strains vary from crystallite to crystallite or within a single crystallite, causing a
broadening of the diffraction peaks.
• If no inhomogeneous strain is present, crystallite size can be estimated from the peak width
using Scherrer's formula..
X-ray diffraction (XRD)
Figure shows the powder
XRD spectra of a series of
InP nanoparticles with
different sizes.1
SAXS is a powerful tool for characterizing nanostructured materials, providing information about
the size and surface area of particles, regardless of whether the sample or particles are crystalline
or amorphous. It uses X-rays scattered from ordered arrays of atoms and molecules, allowing for
the analysis of scattered intensity at low angles.
Small angle X-ray scattering (SAXS)
15. Scanning electron
microscopy (SEM)
• It provides a valuable combination of high resolution
imaging, elemental analysis, and recently,
crystallographic analysis.
• It is used for inspecting topographies of specimens at
very high magnifications using a piece of equipment
called the scanning electron microscope.
• SEM magnifications can go to more than 300,000 X
but most semiconductor manufacturing applications
require magnifications of less than 3,000 X only.
• It is often used in the analysis of die/package cracks
and fracture surfaces, bond failures, and physical
defects on the die or package surface.
• Identifying crystalline compounds and determining
crystallographic orientations of microstructural features
as small as 1 um (recently developed capability--not
currently widely used, but likely to become so).
16. Transmission Electron
Microscope(TEM)
• In it a beam of highly focused electrons are
directed toward a thinned sample
• (<200 nm).
• Normally no scanning required - helps the high
resolution, compared to SEM.
• These highly energetic incident electrons
interact with the atoms in the sample producing
characteristic radiation
• And particles providing information for
materials characterization.
• Information is obtained from both deflected
and non-deflected transmitted electrons,
backscattered and secondary electrons,
andemitted photons.
17. Advantages Disadvantages
•High resolution &Depth
offocus (1 X 10^-6 nm)
•Elemental analysis
attachments
•Almost all kinds of samples,
conducting and non-conducting
(stain coating needed)
• Based on surface interaction
- no requirement of
electron-transparent sample
Imaging at all directions
through x-y-z (3D) rotation
of sample.
•Cost
•More knobs
•Vacuum
• Low resolution, usually
above a few tens of
nanometers.
Usually required surface
stain-coating with metals for
electron cond
Scanning Electron Microscope (SEM) TransmissionElectronMicroscope(TEM)
Advantages Disadvantages
•High resolution, as small as 0.2
nm.
•Direct imaging of crystalline
lattice.
•Delineate the defects inside the
sample.
•N o metallic stain-coating needed,
thus convenient for structural
imaging of organic materials,
•Electron diffraction technique:
phase identification, structure and
symmetry determination, lattice
parameter measurement, disorder
and defect identification.
•ow sampling volume and rather slow
process of obtaining information.
•High capital and running cost.
•Special training required for the
operation of the equipment.
•Difficult sample preparation.
Possibility of electron beamdamage.
Samples which are not stable in
vacuum are difficult to study.
••Magnetic samplesrequire special
care.
••Non-conducting samples require
gold or carbon coating.
• D i f fi c u l t y in the interpretation
of images. In usual mode of
operation information is
integrated along the beam
direction.
18. Gas adsorption
•Physical and Chemical Adsorption Isotherm
•Technique used to determine surface area and
size of particles and porous structures.
•Adsorption occurs when a gas molecules adsorb
onto a solid surface to reduce surface energy.
• Adsorption can be physical or chemical.
Physically adsorbed gases can be removed by
reducing partial pressure.
•Chemisorbed gases are difficult to remove
unless heated to higher temperatures.
• Gas adsorption isotherm measures the
amount of gas needed to form a monolayer or
fill pores.
• When the relative pressure continues to
increase further, capillary condensation will
occur on the inner surface of the pores in
accordance with the Kelvin equation
Five basic types of gas sorption isotherms: (I), monolayer sorption
in pores of moleculardimension;(11, IVandV),multi layer sorptionin
highly porous materials with pores up to -100nm; (111), multilayer
sorption on a nonwetting material. [S. Brunauer,
TheAdsoptionofGasesand Vapors,Princeton
UniversityPress,Princeton,NJ, 1945.1
19. • Opticalspectroscopy
• Optical spectroscopy is a widely used
method for characterizing nano-materials,
categorized into emission spectroscopy
and vibrational spectroscopy.
• The electronic structures of atoms, ions,
molecules, or crystals are determined
through absorption and emission of
electrons from the ground to excited
states. Ex:-absorption and
photoluminescence spectroscopy
• Vibrational techniques involve photon
interactions with species in a sample,
resulting in energy transfer via excitation
or de-excitation, providing chemical bond
information for sample detection. Ex:-
infrared spectroscopy and Raman
spectroscopy
Electron spectroscopy
• The electron spectroscopy relies on
the unique energy levels of the
emission of photons (X-ray) or
electrons ejected from the atoms in
question
• When an electron or photon, like X-rays
or y-rays, hits an unexcited atom, an
inner shell electron is ejected, leaving a
hole. The outer shell electron fills the
hole, releasing excess energy through X-
ray emission (used in EDS) or ejection of
an Auger electron.
• The chemical composition of a material
can be determined by measuring the
energies of X-rays and Auger electrons
emitted by the element in question.
Ionic Spectrometry
• Ion scattering
spectroscopy describes
experiments involving
ionized atoms directed
onto a sample,
determining the energy of
backscattered particles.
This often involves low
energy ions in the 0.5-10
keV range. Energy refers
to kinetic energy.
20. Nanotechonology -Application
Industry Information technolog
y
Medicine Consumer
Goods
Energy
Advantage of
using
nanotechnology
• Smaller, faster, more energy
efficient and powerful
computing and other IT-
based systems
• Cancer treatment
• Bone treatment
• Drug delivery
• Appetite control
• Drug development
• Medical tools
• Diagnostic tests
• Imaging
• Foods and
beverages
• Advanced
packaging materials,
sensors, and lab-on-
chips for food quality
testing
• Appliances and
textiles
• Stain proof, water
proof and wrinkle
free textiles
• Household and
cosmetics
• Self-cleaning and
scratch free
products, paints,
and better
cosmetics
• More efficient
and cost
effective
technologies for
energy
production
• Solar cells
• Fuel cells
• Batteries
• Bio fuels
