Transmission Electron Microscopy Peter Harris www reading ac

Transmission Electron Microscopy Peter Harris www. reading. ac. uk/EMLab

Transmission electron microscopy ► What is transmission electron microscopy? ► TEM in biological science ► TEM in physical science ► Cf. AM’s TEMs ► EM Workshops 2013 Recent developments in TEM

SEM & TEM Electron gun Condenser lens Condenser Objective lens Objective Specimen Projector lens Fluorescent screen Digital camera Specimen Scanning electron microscope EM Workshops 2013 Transmission electron microscope

Transmission electron microscopy Electron gun Current passed through La. B 6 crystal causes electrons to be emitted. Anode accelerates electrons to 80 k. V – 200 k. V. 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. EM Workshops 2013

Transmission electron microscopy Specimens for TEM 3 mm TEM grid Carbon films EM Workshops 2013

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. EM Workshops 2013

Positive staining Electron-dense heavy metal salt selectively stains certain features within the sample. Block copolymer containing polystyrene and polymethylmethacrylate stained with ruthenium tetroxide. EM Workshops 2013

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. Adenovirus negatively stained with uranyl acetate EM Workshops 2013

Biological TEM - negative staining Peptide fibrils, stained with methylamine tungstate (1%) on formvar/carbon grids. Marta Krysmann, School of Chemistry EM Workshops 2013

Biological TEM – preparing specimens from tissue Fix dehydrate set in resin section deposit on grids stain Microtome EM Workshops 2013

Biological TEM – thin section Kidney EM Workshops 2013

The transmission electron microscope is not just a microscope! Energy dispersive X-ray spectrum Diffraction pattern (crystalline C 60) EM Workshops 2013 X-ray analysis workshop: November 27

Contrast in the TEM - 2 Diffraction contrast EM Workshops 2013

Transmission electron microscopy TEM in physical science – bright field imaging Dislocations in stainless steel foil Platinum/alumina catalyst EM Workshops 2013

Contrast in the TEM - 3 Phase contrast: lattice imaging EM Workshops 2013

Multiple electron scattering Electrons passing through a crystal are multiply scattered EM Workshops 2013

Image simulations Example of image simulation: amphibole crystal EM Workshops 2013

EM Lab’s TEMs FEI/Philips CM 20 Analytical TEM EM Workshops 2013 JEOL 2010 High resolution TEM

New developments in TEM - 1 Ultra-high resolution TEM, with aberration correction, Tsukuba, Japan. EM Workshops 2013

New developments in TEM - 2 Tomography – bringing the 3 rd dimension to TEM EM Workshops 2013

TEM at Cf. AM Carbon nanostructures EM Workshops 2013

TEM at Cf. AM Nanoporous Pt particles - applications in catalysis. Samina Akbar& Joanne Elliott, Department of Chemistry EM Workshops 2013

TEM at Cf. AM Micro-phase separated polymer particle, 120 nm diameter. Hamley group. EM Workshops 2013

Becoming an EMLab user Sherrie Foo EM Workshops 2013

Remaining workshops Date 20 November 2013 27 November 2013 EM Workshops 2013 Topic Environmental & Cryo SEM X-ray Analysis and Elemental Mapping

Transmission electron microscopy ► Questions? ► Demo EM Workshops 2013