Introduction to the Electron Microscopy Laboratory · Wavelength of an electron (200 kV): 0.0025...
Transcript of Introduction to the Electron Microscopy Laboratory · Wavelength of an electron (200 kV): 0.0025...
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Introduction to the Electron Microscopy Laboratory
Peter Harris
EM Workshops 2014
Who we are
Why electron microscopy?
Specimen preparation for SEM; advanced forms of SEM
EMLab’s facilities
Specimen preparation for TEM
Electron diffraction and X-ray analysis
Becoming an EMLab user
Tour/questions
Electron Microscopy Laboratory
EM Workshops 2014
Electron Microscopy Laboratory
School of Chemistry, Food and Pharmacy (SCFP)
Chemical Analysis Facility
Electron Microscopy Laboratory
EM Workshops 2014
Electron Microscopy Laboratory
Pharmacy: SEM of polyurethane microcapsules
Chemistry: TEM of peptide nanotapes
Food Biosciences: SEM of bacteria
Biological Sciences: SEM of flower from insectivorous plant
Soil Science: SEM of biochar
EM Workshops 2014
Microscopy basics: why electron microscopy?
The highest resolution achievable by a lens is given by the Rayleigh criterion:
sin
.
nd
610
where d is the resolution, λ is the wavelength of emitted light, and n is the refractive index of
the lens and α is the semi-angle subtended by the aperture.
Wavelength of an electron (200 kV): 0.0025 nm.
Highest resolution of transmission electron microscope ~ 0.1 nm. Individual atoms!
Highest resolution of scanning electron microscope ~ 10 nm.
Wavelength of light (blue): ~ 400 nm.
Highest resolution of optical microscope ~ 200 nm.
EM Workshops 2014
Electron Microscopy Laboratory
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
Workshop: November 5 Workshop: November 12
EM Workshops 2014
Electron Microscopy Laboratory
EMLab’s scanning electron microscopes
Cambridge S360 High Vac SEM FEI Quanta Environmental SEM
EM Workshops 2014
Electron Microscopy Laboratory
EMLab’s transmission electron microscopes
FEI/Philips CM20 Analytical TEM JEOL 2010 High resolution TEM
EM Workshops 2014
Looking at “wet” samples in the high vacuum SEM
Animal and plant tissues up to 98% water.
Options for examining these materials in the high vacuum SEM:
Freeze drying
Chemical fixation, critical point drying
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Critical point drying
Substitution of water with liquid CO2, which has
lower surface tension
Controlled removal of liquid CO2
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Coating SEM specimens
For conventional (high vacuum) SEM, surface
must be electrically conducting.
Usually coat with gold, but can also coat with
chromium or carbon.
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Sample prepared by fixation & critical point drying
Euphorbia seed. Amal Al Hasan, SBS.
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Cryo-SEM
Workshop: November 19
Potato showing starch grains
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Environmental SEM
Workshop: November 19
Cooled specimen
• Special pumping system allows water vapour to be introduced into chamber.
• Cooled specimen to retain moisture.
• New (backscattered) electron detector.
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Environmental SEM
• Raspberry buds : Hiroyuki Imanishi, Plant Sciences
EM Workshops 2014
Specimen preparation for TEM
Specimens for TEM
3 mm TEM grid
Carbon films
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Specimen preparation for TEM
Inorganic powders – easy!
EM Workshops 2014
TEM in physical science
Platinum/alumina catalyst
Gold nanoparticle
Carbon nanostructures
EM Workshops 2014
TEM in biology
Adenovirus negatively stained with
uranyl acetate
EM Workshops 2014
Specimen preparation for TEM
Biological TEM – preparing specimens from tissue
Microtome
Fix dehydrate set in resin section deposit on grids stain
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Specimen preparation for TEM
Specimen preparation laboratory
EM Workshops 2014
Specimen preparation for TEM
Microtome
EM Workshops 2014
Biological TEM – thin section
Kidney
TEM in biology
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An electron microscope is not just a microscope
Elemental analysis - determining the composition of materials
Workshop: November 26 Diffraction pattern (crystalline C60)
Electron diffraction in the TEM
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X-ray Analysis: Mapping
Workshop: November 27
Tracey Finn/Amy Smith (Ure Museum)
Fragments of Egyptian pot
EM Workshops 2014
Becoming an EMLab user
Sherrie Foo
EM Workshops 2014
Booking system
EM Workshops 2014
Remaining workshops
Date
Topic
5 November 2014 Scanning Electron
Microscopy
12 November 2014 Transmission Electron
Microscopy
19 November 2014 Environmental & Cryo
SEM
26 November 2014 X-ray Analysis and
Elemental Mapping
EM Workshops 2014
Electron Microscopy Laboratory
Tour/questions