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Transmission Electron Micros

Transmission Electron Microscopy (TEM) is a powerful imaging technique used to visualize biological and non-biological samples at the molecular level, providing detailed information on their structure and composition. Sample preparation involves several steps including tissue sectioning, fixation, staining, and dehydration, but the process is labor-intensive and requires specialized training. While TEM offers high magnification and resolution, it is expensive, requires special housing, and produces 2D black and white images.

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11 views16 pages

Transmission Electron Micros

Transmission Electron Microscopy (TEM) is a powerful imaging technique used to visualize biological and non-biological samples at the molecular level, providing detailed information on their structure and composition. Sample preparation involves several steps including tissue sectioning, fixation, staining, and dehydration, but the process is labor-intensive and requires specialized training. While TEM offers high magnification and resolution, it is expensive, requires special housing, and produces 2D black and white images.

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Transmission Electron Microscopy

(TEM)
• Telegram Channel: SCIENCE WORKSHOP
• Twitter: Kusum Chaudhary
Transmission Electron Microscope
Sample Preparation
• Tissue sectioning – thined to less than 100nm on an ultramicrotome .
• Fixation – fixed with chemical products ( Glutaraldehyde)
• Rinsing and Staining - treated with heavy metal compunds ( osmium,
lead , uranium)
• Dehydration – washing with increasing eathanol concentration.
• Live cells cannot be seen in this microscopy.
• Both biological and non biological components can be visualized with
electron microscopy.
Applications of TEM
• TEM provide topographical, morphological , compositional and
crystalline information.
• TEM is used to study a sample at the molecular level, to do structure
analysis and texture analysis.
• Cancer research – studies of tumor cell ultrastructure.
Advantages of TEM
• TEM offer very powerful magnification and resolution.
• TEM provide information on element and compund structure.
• Image are High quality and detailed.
Disadvantages of TEM
• TEM are large and very expensive.
• Laborious sample preparation.
• Opration and analysis requires special training.
• TEM require special housing and maintenance.
• Image are black and white (2D).
Components of TEM
(TEM)
How it’s Work
- Principal
TEM Image
Principal
• TEM is complex and sophisticated but the basic principle behind its operation can be readily
understood.
• A heated tungsten filament in the electron gun generates a beam of electrons that is then
focused on the specimen by the condenser.
• Since electrons cannot pass through a glass lens ,magnetic lenses are used to focus the beam.
• The column containing the lenses and specimen must be under high vaccum to obtain a clear
image because electrons are deflicted by collisions with air molecules.
• The specimen scatters electron passing through it, and the beam is focused by magnetic lenses
to form an enlarged , visible image of the specimen on a fluorescent screen.
• A denser region in the specimen scatters more electron and therefore appears darker in the
image.
• In contrast, electron-transparent regions are brighter.
• The screen can also be moved aside and the image captured on photographic film as a
permanent record.
How it’s Work
• Electron beams are produced from the electron source.
• Electron beams fall on the sample through the condenser lens.
• Some electrons are transmitted from the sample, the transmitted electrons
pass through the objective lens and reach the objective aperture.
• Then passing through the objective aperture, these electrons fall on the
screen through the intermediate lens.
• Here the image develops on the basis of how many electrons have been
transmitted. We can see this image on the computer screen .
• We get the image on the basis of how many electrons are scattered here.
• In the sample, the energy of the electron crossing from the electron
beam nucleus in the molecule is not much lost and there is less
scatter.
• The electrons of the electron beam which cross through the existing
electron, their energy decreases, they become more scattered.
• If the electrons are more scatter then the image will appear dark from
there.
• The image will appear brighter from where the electrons are less
scattered.

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