Introduction
Nanoparticle characterization techniques
Electron Microscope
Scanning electron microscope
Transmission electron Microscope
X-ray powder diffraction
Nuclear Magnetic Resonance
2. Introduction
Nanoparticle characterization techniques
Electron Microscope
Scanning electron microscope
Transmission electron Microscope
X-ray powder diffraction
Nuclear Magnetic Resonance
Contents
3. Characterization refers to the study of material’s features such as its
composition, structure,& various properties like physical, electrical,
magnetic etc.
Nano = 10-9 (extremely small) Particle = Small piece of matter
Nanoparticle is a microscopic particle whose size is measured in
nanometers (nm).
These particles can be spherical, tubular, or irregularly shaped and can
exist in fused, aggregated or agglomerated forms.
7. Electron Probe Characterization Techniques
Acronym Technique Utility
SEM Scanning Electron Microscopy Imaging/ topology
morphology
EPMA Electron Probe Microanalysis Particle size/ local chemical
analysis
TEM Transmission Electron Microscopy Imaging/ Particle size shape
HRTEM High Resolution Transmission Electron
Microscopy
Imaging structure chemical
analysis
LEED Low Energy Electron Diffraction Surface/ adsorbate bonding
EELS Electron Energy Loss Spectroscopy Inelastic electron
interaction
AES Auger Electron Spectroscopy Chemical surface analysis
8. Scanning Probe Characterization Techniques
Acronym Technique Utility
AFM Atomic Force Microscopy Imaging/ topology/ surface
structure
CFM Chemical Force Microscopy Chemical/surface analysis
MFM Magnetic Force Microscopy Magnetic material analysis
STM Scanning Tunnelling Microscopy Topology/Imaging /surface
APM Atomic Probe Microscopy Three dimensional Imaging
FIM Field Ion Microscopy Chemical profiles/ atomic spacing
APT Atomic probe tomography Position sensitive lateral location
of atoms
10. Ion-particle probe Characterization Techniques
Acronym Technique Utility
RBS Rutherford back scattering Quantitative- Qualitative elemental
analysis
SANS Small angle neutron scattering Surface characterization
NRA Nuclear reaction analysis Depth profiling of solid thin film
RS Raman Spectroscopy Vibration analysis
XRD X-ray diffraction Crystal structure
EDX Energy dispersive X-ray spectroscopy Elemental analysis
SAXS Small angle X-ray scattering Surface analysis/ particle sizing (1-100 nm)
CLS Cathodoluminescence Characteristics emission
NMR Nuclear magnetic resonance
spectroscopy
Analysis of odd no. of nuclear species
11. Thermodynamic Characterization Techniques
Acronym Technique Utility
TGA Thermal gravimetric analysis Mass loss Vs. Temperature
DTA Differential thermal analysis Reaction heat capacity
DSC Differential scanning calorimetry Reaction heat phase changes
NC Nanocalorimetry Latent heats of fusion
BET Brunauer-Emmett-Teller method Surface area analysis
Sears Sears method Colloid size, specific surface area
12. Light microscopes cannot resolve structures closer than 200 nm
Electron microscopes have greater resolving power and magnification
Magnifies objects 10,000X to 100,000X
Detailed views of bacteria, viruses, internal cellular structures,
molecules, and large atoms
Two types
• Transmission electron microscopes
• Scanning electron microscopes
The Electron Microscope
13. • Energy source is a beam of electrons
• Image is created and viewed on a monitor
• TEM (transmission electron microscope) utilizes staining procedures
prior to use
• SEM (scanning electron microscope) adds three-dimensional viewing
The Electron Microscope
14. • Beams of electrons are used to
produce images
• Wavelength of electron beam is
much shorter than light,
resulting in much higher
resolution
The Electron Microscope
15. • In transmission electron microscopy electrons pass through thin
specimens (50-1000 nm). BULK BEAM
• In scanning electron microscopy signals emitted from the surface of
thick specimens. NARROW BEAM
Physical Limitations
16. • Uses electrons reflected from the surface of a specimen to create
image
• Produces a 3-dimensional image of specimen’s surface features
Scanning Electron Microscope (SEM)
20. The SEM is an instrument that produces a largely magnified
image by using electrons instead of light to form an image.
A beam of electrons is produced at the top of the microscope
by an electron gun.
The electron beam follows a vertical path through the
microscope, which is held within a vacuum.
The beam travels through electromagnetic fields and lenses,
which focus the beam down toward the sample.
Once the beam hits the sample, electrons and X-rays are
ejected from the sample.
Detectors collect these X-rays, backscattered electrons, and
secondary electrons and convert them into a signal that is
sent to a screen similar to a television screen. This produces
the final image.
Working of SEMWorking of Scanning Electron Microscope (SEM)
24. • Electrons scatter when they pass through thin sections of a
specimen
• Transmitted electrons (those that do not scatter) are used to
produce image
• Denser regions in specimen, scatter more electrons and appear
darker
Transmission Electron Microscope (TEM)
25. Working of Transmission Electron Microscope (TEM)
Unlike SEM that bounces electrons off the surface of a sample
to produce an image, Transmission Electron Microscopes
(TEMs) shoot the electrons completely through the sample.
TEMs work by using a tungsten filament to produce an
electron beam in a vacuum chamber.
The emitted electrons are accelerated through an
electromagnetic field that also narrowly focuses the beam.
The beam is then passed through the sample material. The
specially prepared sample is a very thin (less than 100nm) slice
of material. The electrons that pass through the sample hit a
phosphor screen, CCD or film and produce an image. Where
the sample has less density, more electrons get through and
the image is brighter. A darker image is produced in areas
where the sample is more dense and therefore less electrons
pass through.
TEMs can produce images with resolution down to 0.2nm. This
resolution is smaller than the size of most atoms and therefore
images can be produced using TEM that show the true
structural arrangement of atoms in the sample material.
26. • X-ray diffraction is used to obtain
structural information about crystalline
solids.
• Useful in biochemistry to solve the 3D
structures of complex biomolecules.
• Bridge between physics, chemistry, and
biology.
• X-ray diffraction is important for
Solid-state physics
Biophysics
Medical physics
Chemistry and Biochemistry
Introduction of X-ray Diffraction
27. • Most useful in the characterisation of
• Crystalline materials;
• Ceramics,
• Metals,
• Intermetallic,
• Minerals,
• Inorganic compounds
• Rapid and non destructive techniques
• Provide information on unit cell dimension
Structural Analysis
• X-ray diffraction provides most definitive
structural information
• Interatomic distances and bond angles
What is X-ray Diffraction
28. • Beams of electromagnetic radiation
• *smaller wavelength than visible light,
• *higher energy
• *more penetrative
29. • (1895) X-rays discovered by Roentgen
• (1914) First diffraction pattern of a crystal made by
Knipping and von Laue
• (1915) Theory to determine crystal structure from
diffraction pattern developed by Bragg.
• (1953) DNA structure solved by Watson and Crick
• Now Diffraction improved by computer technology;
methods used to determine atomic structures and in
medical applications
History of X-ray Diffraction
30. • The prime component in X-Ray tube are
filament (cathode), vacuum room, anode,
and high voltage
• When high energy electrons strike an anode
in a sealed vacuum, x-rays are generated.
Anodes are often made of copper, iron or
molybdenum.
• High energy electron come from heated
filament in X-Ray tube.
• X-rays are electromagnetic radiation.
• They have enough energy to cause
ionization.
X-ray Production
31. • English physicists Sir W.H. Bragg and his son Sir W.L.
Bragg developed a relationship in 1913 to explain
why the cleavage faces of crystals appear to reflect
X-ray beams at certain angles of incidence (theta, θ).
• d is the distance between atomic layers in a
crystal,
• lambda λ is the wavelength of the incident X-ray
beam;
• n is an integer.
• This observation is an example of X-ray wave
interference (Roentgen strahl interferenzen),
commonly known as X-ray diffraction (XRD), and
was direct evidence for the periodic atomic
structure of crystals postulated for several centuries.
Bragg’s Law
nλ = 2d sin θ
32. • Wave Interacting with a Single Particle
• Incident beams scattered uniformly in all directions
• Wave Interacting with a Solid
• Scattered beams interfere constructively in some directions, producing
diffracted beams
• Random arrangements cause beams to randomly interfere and no distinctive
pattern is produced
• Crystalline Material
• Regular pattern of crystalline atoms produces regular diffraction pattern.
• Diffraction pattern gives information on crystal structure
How Diffraction Works
33. • X-ray source
• Device for restricting wavelength
range “goniometer”
• Sample holder
• Radiation detector
• Signal processor and readout
Components of X-ray Diffraction
34. X-ray Diffraction Instrumentation
X-ray diffractometers consist of three basic elements:
an X-ray tube,
a sample holder,
an X-ray detector.
X rays are generated in a cathode ray tube by heating a filament to produce electrons,
accelerating the electrons toward a target by applying a voltage, and bombarding the
target material with electrons.
When electrons have sufficient energy to dislodge inner shell electrons of the target
material, characteristic X-ray spectra are produced. These spectra consist of several
components, the most common being Kα and Kβ.
Kαconsists, in part, of Kα1 and Kα2.
Kα1 has a slightly shorter wavelength and twice the intensity as Kα2.
The specific wavelengths are characteristic of the target material (Cu, Fe, Mo, Cr).
Filtering, by foils or crystal monochrometers, is required to produce monochromatic X-
rays needed for diffraction. Kα1and Kα2 are sufficiently close in wavelength such that a
weighted average of the two is used.
35. X-ray Diffraction Instrumentation
Copper is the most common target material for single-crystal diffraction, with
CuKα radiation = 1.5418Å.
These X-rays are collimated and directed onto the sample.
As the sample and detector are rotated, the intensity of the reflected X-rays is recorded.
When the geometry of the incident X-rays impinging the sample satisfies the Bragg
Equation, constructive interference occurs and a peak in intensity occurs.
A detector records and processes this X-ray signal and converts the signal to a count rate
which is then output to a device such as a printer or computer monitor.
The geometry of an X-ray diffractometer is such that the sample rotates in the path of
the collimated X-ray beam at an angle θ while the X-ray detector is mounted on an arm
to collect the diffracted X-rays and rotates at an angle of 2θ.
The instrument used to maintain the angle and rotate the sample is termed
a goniometer.
For typical powder patterns, data is collected at 2θ from ~5° to 70°, angles that are
present in the X-ray scan.
36. • A continuous beam of X-rays is
incident on the crystal
• The diffracted radiation is very
intense in certain directions
• These directions correspond to
constructive interference from
waves reflected from the layers of
the crystal
• The diffraction pattern is detected
by photographic film
How X-ray Diffraction works
40. Used to determine
• Crystal structure
• Orientation
• Degree of crystalline perfection/imperfections
Sample is illuminated with monochromatic radiation
• Easier to index and solve the crystal structure because it
diffraction peak is uniquely resolved
Single Crystal X-ray Diffraction
41. A single crystal at random orientations and its corresponding diffraction pattern.
Just as the crystal is rotated by a random angle, the diffraction pattern
calculated for this crystal is rotated by the same angle
Single Crystal X-ray Diffraction
42. More appropriately called polycrystalline X-ray diffraction, because it
can also be used for sintered samples, metal foils, coatings and films,
finished parts, etc.
Used to determine
phase composition (commonly called phase ID)-what phases are
present?
quantitative phase analysis-how much of each phase is present?
unit cell lattice parameters, crystal structure
average crystallite size of nanocrystalline samples
crystallite microstrain and texture
residual stress (really residual strain)
X-ray Powder Diffraction
43. Fundamental Principle of X-ray Powder Diffraction
This law relates the wavelength of electromagnetic radiation to the diffraction angle and
the lattice spacing in a crystalline sample.
These diffracted X-rays are then detected, processed and counted.
By scanning the sample through a range of 2θangles, all possible diffraction directions of
the lattice should be attained due to the random orientation of the powdered material.
Conversion of the diffraction peaks to d-spacings allows identification of the mineral
because each mineral has a set of unique d-spacings.
Typically, this is achieved by comparison of d-spacings with standard reference patterns.
All diffraction methods are based on generation of X-rays in an X-ray tube.
These X-rays are directed at the sample, and the diffracted rays are collected.
A key component of all diffraction is the angle between the incident and diffracted rays.
44. Single crystal Vs. Powder crystal XRD
Although the single crystal and powder crystal XRD patterns essentially contain
the same Information, but in the former case the information is distributed in
three dimensional space whereas In the latter case the three dimensional data
are “compressed” into one dimension
45. X-ray Powder Diffraction Applications
Characterization of crystalline materials
Identification of fine-grained minerals such as clays and mixed layer clays that are
difficult to determine optically
Determination of unit cell dimensions
Measurement of sample purity
Determine of modal amounts of minerals (quantitative analysis)
Characterize thin films samples by:
determining lattice mismatch between film and substrate and to inferring stress and
strain
determining dislocation density and quality of the film by rocking curve
measurements
measuring superlattices in multilayered epitaxial structures
determining the thickness, roughness and density of the film
make textural measurements, such as the orientation of grains, in a polycrystalline
sample
46. Strength of X-ray Powder Diffraction
1. Powerful and rapid (< 20 min) technique for
identification of an unknown mineral
2. In most cases, it provides an unambiguous
mineral determination
3. Minimal sample preparation is required
4. XRD units are widely available
5. Data interpretation is relatively straight forward
