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Transmission Electron Microscopy. Peter Harris. Transmission electron microscopy. ► What is transmission electron microscopy?. ► TEM in biological science . ► TEM in physical science . ► CfAM’s TEMs. ► Recent developments in TEM. SEM & TEM. Electron gun. Electron gun. Electron gun.

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Transmission Electron Microscopy


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    Presentation Transcript
    1. Transmission Electron Microscopy Peter Harris

    2. Transmission electron microscopy ► What is transmission electron microscopy? ► TEM in biological science ► TEM in physical science ► CfAM’s TEMs ► Recent developments in TEM

    3. SEM & TEM Electron gun Electron gun Electron gun Electron gun Condenser lens Condenser lens Objective lens Objective lens Specimen Specimen Projector lens Projector lens Fluorescent screen Fluorescent screen Digital camera Digital camera Specimen Scanning electron microscope Transmission electron microscope

    4. Electron gun Current passed through LaB6 crystal causes electrons to be emitted. Anode accelerates electrons to 80 kV – 200kV. Electromagnetic lenses A current through the coils creates a magnetic field, symbolized by red lines in the diagram on the left. Electrons close to the centre are less strongly deflected than those passing through the lens far from the axis. Transmission electron microscopy

    5. 3 mm TEM grid Carbon films Transmission electron microscopy Specimens for TEM

    6. Contrast in the TEM - 1 Biological and “soft matter” Absorption contrast: Heavy atoms absorb more electrons than light atoms. Scattering contrast: Some electrons blocked by objective aperture.

    7. Positive staining Electron-dense heavy metal salt selectively stains certain features within the sample. Block copolymer containing polystyrene and polymethylmethacrylate stained with ruthenium tetroxide.

    8. Adenovirus negatively stained with uranyl acetate Biological TEM - negative staining Surrounding biomolecules with thin amorphous layer of heavy metal salt. Reveals structure, and reduces structural flattening that occurs in the absence of stain. Commonly used stains: uranyl acetate, uranyl formate, sodium/potassium phosphotungstate, ammonium molybdate.

    9. Biological TEM - negative staining Peptide fibrils, stained with methylamine tungstate (1%) on formvar/carbon grids. Marta Krysmann, School of Chemistry

    10. Biological TEM – preparing specimens from tissue Fix  dehydrate  set in resin  section  deposit on grids  stain Microtome

    11. Biological TEM – thin section Kidney

    12. Energy dispersive X-ray spectrum The transmission electron microscope is not just a microscope! X-ray analysis workshop: November 27 Diffraction pattern (crystalline C60)

    13. Contrast in the TEM - 2 Diffraction contrast

    14. Dislocations in stainless steel foil Platinum/alumina catalyst Transmission electron microscopy TEM in physical science – bright field imaging

    15. Contrast in the TEM - 3 Phase contrast: lattice imaging

    16. Multiple electron scattering Electrons passing through a crystal are multiply scattered

    17. Image simulations Example of image simulation: amphibole crystal

    18. FEI/Philips CM20 Analytical TEM JEOL 2010 High resolution TEM EM Lab’s TEMs

    19. New developments in TEM - 1 Ultra-high resolution TEM, with aberration correction, Tsukuba, Japan.

    20. New developments in TEM - 2 Tomography – bringing the 3rd dimension to TEM

    21. TEM at CfAM Carbon nanostructures

    22. TEM at CfAM Nanoporous Pt particles - applications in catalysis. Samina Akbar& Joanne Elliott, Department of Chemistry

    23. TEM at CfAM Micro-phase separated polymer particle, 120nm diameter. Hamley group.

    24. Becoming an EMLab user Sherrie Foo

    25. Remaining workshops

    26. Transmission electron microscopy • ►Questions? • ►Demo