TEM is a type of electron microscope that uses electron beams to produce magnified images of samples. TEMs can magnify up to 1 million times, allowing observation of ultrafine cell structures. Sample preparation is required to make specimens thin enough for electrons to pass through. TEMs are very expensive, ranging from $95,000 to over $100,000, but provide high resolution imaging useful for fields like nanotechnology, biology and materials science.

1. NANO SCIENCE
TRANSMISSION ELECTRON MICROSCOPE
BY
U. Monika
I- M.Sc Biochemistry

3. INTRODUCTION
ELECTRON MICROSCOPE - System of
electromagnetic coils where electron beams are used as a
source of illumination.
Electron microscope = Magnification is
high.
Magnification of 2000 times than that
of light microscope.

4. TYPES OF ELECTRON MICROSCOPE
1. Transmission Electron Microscope (TEM)
2. Scanning Electron Microscope (SEM)

5. TRANSMISSION ELECTRON MICROSCOPE
TEM is a special type of microscope that uses
electron for magnification.
Electrons - smaller wavelength.
Achieve extreme magnification.
Average TEM - Magnification of 1,000,000x

6. DEFINITION :
Electron Microscope in which electron beam is
passed through the specimen to produce its image.
First TEM was designed by Max knoll and Ernest
ruska in 1931.
TEM is a powerful tool for Material science.
Reveals the finest details of internal structures.

7. PRINCIPLE
Basic principle of electron microscope is
similar to that of the ordinary compound microscope.
Electron Beam - Light Beam
Electromagnetic coils - Optical lenses.
When light voltage current is passed through
a filament of cathode ray tube, electron beams are
produced from the filament.

8. If some voltage of current is applied to
electromagnetic coils kept around the path of electron
beam, the direction of electron beam can be changed
suitably to focus on the specimen.
When an electron beam is passed through a
specimen stained with metallic gold or osmium, the
specimen absorbs some rays and reflects some rays to pass
through it.

10. Interaction between electrons and specimen in
the beam produces the image of the specimen.
Image of the specimen can be collected by an
objective lens (an electromagnetic coil)
Magnified by an Amplifier (another coil)
Due to electron distribution, image cannot be
seen with naked eyes.
Image - Recorded on a Screen or Camera.

11. INSTRUMENTATION
TEM consists of electron gun, condenser lens,
objective lens, amplifier lens, projector lens & fluorescent
screen.
ELECTRON GUN - Source of electron beam
CONDENSER LENS - Located below the electron gun
Collect and concentrate the
electron into a strong beam
before focusing onto specimen.

12. SPECIMEN STAGE - Below the condenser lens
OBJECTIVE LENS - Another electromagnetic coil,
placed below the specimen stage.
It collects the images of the
specimen and focuses it towards
the amplifier lens.
AMPLIFIER LENS - Magnifies image produced by the
objective lens to several 1000
Times.
PROJECTOR LENS - Collects the magnified image &
focus it onto fluorescent screen.

14. SAMPLE PREPARATION
The biological samples have to be loaded
with heavy atoms like gold or osmonium.
SAMPLE PREPARATION AND EXAMINATION :
1. Wet specimen is dehydrated using ethanol or acetone.
2. Fixation is done by Osmonium tetroxide,
glutaraldehyde, potassium permanganate,formalin etc.

15. 3. The fixed specimen is embedded in hard embedding
medium like aradilite and cut into thin section of 50-
100nm thickness using ultramicrotome.
4. Thin sections subjected to metallic staining and placed
on the specimen stage between the condenser lens coil
and objective coil.

16. IMAGING
A Transmission Electron Microscope produces a
high-resolution, black and white image from the
interaction that takes place between prepared samples
and energetic electrons in the vacuum chamber.
Air needs to be pumped out of the vacuum
chamber, creating a space where electrons are able to
move.
The electrons then pass through multiple
electromagnetic lenses.

17. These solenoids are tubes with coil wrapped around
them.
The beam passes through the solenoids, down the
column, makes contact with the screen where the
electrons are converted to light and form an image.
The image can be manipulated by adjusting the
voltage of the gun to accelerate or decrease the speed of
electrons as well as changing the electromagnetic
wavelength via the solenoids.
The coils focus images onto a screen or photographic
plate.

18. During transmission, the speed of electrons directly
correlates to electron wavelength; the faster electrons
move, the shorter wavelength and the greater the quality
and detail of the image.
The lighter areas of the image represent the places
where a greater number of electrons were able to pass
through the sample and the darker areas reflect the dense
areas of the object.
These differences provide information on the
structure, texture, shape and size of the sample.

19. SAMPLE PROPERTIES :
Samples need to have certain properties.
They need to be sliced thin enough for electrons to
pass through, a property known as electron transparency.
Samples need to be able to withstand the vacuum
chamber and often require special preparation before
viewing.
Types of preparation include dehydration, sputter
coating of non-conductive materials, cryofixation,
sectioning and staining.

20. APPLICATIONS
● Ideal tool for study of ultra structure of cells.
● Identification of plant and animal viruses based on
their structural features.
● Employed in the localization of nucleic acid, enzymes
and proteins in cell and cell organelles.
● Used in cancer research for the cytological
observation of cancer cells.

21. ● Used in various fields such as nanotechnology, life
sciences, medical, biological, material research,
forensic analysis, metallurgy as well as in industries
and education.
● Used in the production and manufacturing of
computer and silicon chips.
● Provide topographical, morphological, compositional
and crystalline informations.

22. Advantages
A Transmission Electron Microscope is an
impressive instrument with a number of advantages such
as:
● TEMs offer the most powerful magnification,
potentially over one million times or more.
● TEMs have a wide-range of applications and can be
utilized in a variety of different scientific, educational
and industrial fields

23. ● TEMs provide information on element and
compound structure
● Images are high-quality and detailed
● TEMs are able to yield information of surface
features, shape, size and structure
● They are easy to operate with proper training

24. Disadvantages
Some limitations of electron microscopes include:
● TEMs are large and very expensive
● Laborious sample preparation
● Operation and analysis requires special training
● Samples are limited to those that are electron
transparent, able to tolerate the vacuum chamber and
small enough to fit in the chamber.
● TEMs require special housing and maintenance
● Images are black and white

25. What is the Cost?
TEMs are manufactured by companies such as
Jeol, Philips and Hitachi and are extremely expensive.
Examples of prices for new TEM models include
$95,000 for a Jeol and Philips and $100,000 for a
Hitachi.
In India, the cheapest one costs about
80-90 lakhs.

26. SUMMARY
TEM is useful for small, nanoscale analytes.
TEM can create 3D images of samples.
TEM can be modified for different atoms and
molecules.
TEM is not cheap. It is Good!