Laboratory Instruments 1 PDF

Laboratory instruments 1 Lce1 Asst. Lecturer Zahraa Alamery 1 alkafeel.edu.iq info@...

Laboratory instruments 1 Lce1 Asst. Lecturer Zahraa Alamery 1 alkafeel.edu.iq [email protected] 2023  Electron Microscope (EM) Electron Microscope (EM): A type of microscope that uses an electron beam to illuminate a specimen and produce a magnified image, an EM has greater resolving power than a light microscope and can reveal the structure of smaller objects because electrons have short wavelengths. Some electron microscopes can magnify specimens up to 2 million times, while the best light microscopes are limited to magnifications of 1000 time. It is much useful in studying virus and components of cell. The observable samples include biological specimens as well as inorganic and organic materials. 2 alkafeel.edu.iq [email protected] 2023  The electron microscope uses electrostatic and electromagnetic lenses to control the electron beam and focus it to form an image. These lenses are analogous to the glass lenses of a light microscope. 3 alkafeel.edu.iq [email protected] Types of (EM): 1.Transmission electron microscope (TEM): A transmission electron microscope (TEM) is an analytical tool allowing visualization and analysis of specimens in the realms of microspace (1 micron = 10-6m) to nanospace (1 nanometer/nm = 10-9m). TEM involves a high voltage electron beam emitted by an electron gun, usually fitted with a tungsten filament cathode as the electron source. The electron beam is focused by electrostatic and electromagnetic lenses, and transmitted through a specimen that is in part transparent to electrons and in part scatters them out of the beam. 4 alkafeel.edu.iq [email protected] 2023  When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by the objective lens system of the microscope. The image is recorded by projecting the magnified electron image onto a fluorescent viewing screen coated with a phosphor or scintillator material such as zinc sulfide. The aim of biological sample preparation is the generation of ultra- thin samples transparent for electron beams. For biological samples, sample preparation may be the longest part of the electron microscopic experiment 5 alkafeel.edu.iq [email protected]  Steps: 1. Fixation 2. Dehydration 3. Embedding 4. Cutting with an ultra-microtome 5. Samples are placed on a grid made of copper 6. Staining 6 alkafeel.edu.iq [email protected] Tuesday, August 24, 2021  2.Scanning electron microscope (SEM): type of electron microscope, designed for directly studying the surfaces of solid objects, that utilizes a beam of focused electrons of relatively low energy as an electron probe that is scanned in a regular manner over the specimen. Scanning electron microscope, like the TEM, consists of an electron optical column, a vacuum system, electronics controls, detectors, scanning system, and display. The column is considerably shorter; in addition, there are no lenses below the specimen. The specimen chamber, on the other hand, is larger. 7 alkafeel.edu.iq [email protected] Tuesday, August 24, 2021  What are the Differences between SEM and TEM? - TEM enables data to be captured regarding the sample’s inner structure, where SEM provides data about the surface of the analyzed object. - TEM offers a greater resolution compared to SEM. - In comparison to SEM, TEM has more stringent requirements concerning the preparation of samples and the conditions of analysis -SEM produces an image of the three-dimensional structure of the surface of a specimen, TEM produces two- dimensional images 8 alkafeel.edu.iq [email protected]  Disadvantages of EM Black and white images – Only black and white images can be produced  by an electron microscope. Images must be falsely colorized. Cost – Electron microscopes are expensive pieces of highly specialized  equipment. As most projects have limited budgets, it may prove detrimental to use an electron microscope in the research. Size – electron microscopes are still large, bulky pieces of equipment  which require plenty of space in a laboratory as electron microscopes are highly sensitive, magnetic fields and  vibrations caused by other lab equipment may interfere with their operation. Consideration must be given to this if the researcher is looking to install an electron microscope in their laboratory. Training – Specialist operators are required to operate electron microscope 9 alkafeel.edu.iq [email protected]  10 Tuesday, August 24, 2021 alkafeel.edu.iq [email protected]