Post on 23-May-2020
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www.reading.ac.uk/EMLab
Transmission Electron Microscopy
Peter Harris
EM Workshops 2017
Transmission electron microscopy
► What is transmission electron microscopy?
► TEM in biological science
► EMLab’s TEMs
► TEM in physical science
► Capabilities of our new TEM
EM Workshops 2017
SEM & TEM
Scanning electron microscope
Electron gun
Specimen
Electron gun
Condenser lens
Objective lens
Specimen
Projector lens
Fluorescent screen
Electron gun
Digital camera
Condenser lens
Objective lens
Specimen
Projector lens
Fluorescent screen
Electron gun
Digital camera
Transmission electron microscope
EM Workshops 2017
Transmission electron microscopy
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.
Electron gun
Current passed through LaB6 crystal causes electrons to be emitted. Anode accelerates electrons to 80 kV – 200kV.
EM Workshops 2017
Transmission electron microscopy
Specimens for TEM
3 mm TEM grid
Carbon films
EM Workshops 2017
Absorption contrast:
Heavy atoms absorb more
electrons than light atoms.
Contrast in the TEM - 1
Biological and “soft matter”
Scattering contrast:
Some electrons blocked by
objective aperture.
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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 2017
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 2017
Biological TEM - negative staining
Peptide fibrils, stained with methylamine tungstate (1%) on formvar/carbon grids.
Marta Krysmann, School of Chemistry
EM Workshops 2017
Biological TEM – preparing specimens from tissue
Microtome
Fix dehydrate set in resin section deposit on grids stain
EM Workshops 2017
Biological TEM – thin section
Kidney
EM Workshops 2017
Biological TEM – thin section
Chloroplast of basil leaf. Dr Carol Wagstaff, Kala Radha (Food Biosci) & Matthew Spink (EMLab).
Biological specimen preparation for TEM: 28 November
EM Workshops 2017
Easy!
TEM – specimen prep of inorganic powders
EM Workshops 2017
Electron diffraction
Diffraction pattern (crystalline C60)
EM Workshops 2017
Diffraction contrast
Contrast in the TEM - 2
EM Workshops 2017
Transmission electron microscopy
TEM in physical science – bright field imaging
Dislocations in stainless steel foil
Platinum/alumina catalyst
EM Workshops 2017
Phase contrast: lattice imaging
Contrast in the TEM - 3
EM Workshops 2017
Multiple electron scattering
Electrons passing through a crystal are multiply scattered
EM Workshops 2017
Image simulations
Example of image simulation: amphibole crystal
EM Workshops 2017
EM Lab’s TEMs
JEOL 2010 High resolution TEMJEOL 2100Plus TEM/STEM
(installed Feb. 2017)
EM Workshops 2017
Electron Microscopy Laboratory
Our new transmission electron microscope
JEOL 2100Plus
Capabilities:
Cryo imaging
Tomography
EM Workshops 2017
Cryo-TEM
● Samples suspended in amorphous ice
● No dehydration, fixing or staining: shows samples in their native environment
● Usually carried out using automatic plunge-freezer
FEI Vitrobot
EM Workshops 2017
Cryo-TEM
EM Workshops 2017
Cryo -TEM
Cryo-TEM of influenza virions
EM Workshops 2017
Nobel Prize for Chemistry 2017
EM Workshops 2017
Tomography – bringing the 3rd dimensionto TEM
EM Workshops 2017
Electron tomography
Tilt series of carbon
nanostructures
EM Workshops 2017
TEM at EMLab
Carbon nanostructures
EM Workshops 2017
TEM at EMLab
Nanoporous Pt particles -applications in catalysis.
Samina Akbar& Joanne Elliott,Department of Chemistry
EM Workshops 2017
TEM at EMLab
Micro-phase separated polymer particle, 120nm diameter. Hamley group.
EM Workshops 2017
Pseudomonas fluorescens bacteria, stained with UA. Othman Mohammed/Sheila MacIntyre, SBS.
EM Workshops 2017
TEM at EMLab
Chicken cells infected with coronaviruses.
Hasan Alrashedi, SBS.
EM Workshops 2017
Becoming an EMLab user
Sherrie Foo
EM Workshops 2017
Booking system
EM Workshops 2017
Remaining workshops
Date Topic
7 November 2017Environmental & Cryo
SEM
14 November 2017Biological specimen
preparation for SEM
21 November 2017X-ray Analysis and
Elemental Mapping
28 November 2017Biological specimen
preparation for TEM
EM Workshops 2017
► Questions?
Transmission electron microscopy
► Demo