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.
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 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
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
3 mm TEM grid Carbon films Transmission electron microscopy Specimens for TEM
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.
Positive staining Electron-dense heavy metal salt selectively stains certain features within the sample. Block copolymer containing polystyrene and polymethylmethacrylate stained with ruthenium tetroxide.
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.
Biological TEM - negative staining Peptide fibrils, stained with methylamine tungstate (1%) on formvar/carbon grids. Marta Krysmann, School of Chemistry
Biological TEM – preparing specimens from tissue Fix dehydrate set in resin section deposit on grids stain Microtome
Energy dispersive X-ray spectrum The transmission electron microscope is not just a microscope! X-ray analysis workshop: November 27 Diffraction pattern (crystalline C60)
Contrast in the TEM - 2 Diffraction contrast
Dislocations in stainless steel foil Platinum/alumina catalyst Transmission electron microscopy TEM in physical science – bright field imaging
Contrast in the TEM - 3 Phase contrast: lattice imaging
Multiple electron scattering Electrons passing through a crystal are multiply scattered
Image simulations Example of image simulation: amphibole crystal
FEI/Philips CM20 Analytical TEM JEOL 2010 High resolution TEM EM Lab’s TEMs
New developments in TEM - 1 Ultra-high resolution TEM, with aberration correction, Tsukuba, Japan.
New developments in TEM - 2 Tomography – bringing the 3rd dimension to TEM
TEM at CfAM Carbon nanostructures
TEM at CfAM Nanoporous Pt particles - applications in catalysis. Samina Akbar& Joanne Elliott, Department of Chemistry
TEM at CfAM Micro-phase separated polymer particle, 120nm diameter. Hamley group.
Becoming an EMLab user Sherrie Foo
Transmission electron microscopy • ►Questions? • ►Demo