Plasma Chemistry Applied to Electron Microscopy (EM) Preparation
A selection of published work covering a range of applications using
plasma chemistry as a preparation technique.
Analysis of paint pigment distribution
Paint on microscope slides is ashed in Oxygen for progressively
longer periods with intermittent weight and surface sampling by EM
replication techniques. Pigment distribution through the film thickness
can be evaluated in an "onion peel" fashion. Also applicable
to accelerated weathering of paint finishes.
"Analysis of paint pigment distribution" Paint Research Association
Newsletter April 1979 no. 12.
Evaluation of implants in primates
A range of Tantalum samples prepared in a variety of ways were implanted
and then evaluated in relation to effects on surrounding tissue by
a variety of techniques, including EM. Samples treated in an Oxygen
plasma prior to implanting showed high surface energy and bio-adhesion
compared to untreated
"Tissue response to surface treated Tantalum implants. Preliminary observations
in primates." Michael A Meenaghan. Journal of Biomedical Materials Research.
Vol 12, 631443 (1979).
Plasma ashing of paper
SEM studies of paper. Oxygen ashing over progressive periods of
up to 30 minutes indicated the gradual destruction of cellulose while
the Kaolin filler remains unaffected.
Replica EM studies of Polyamide structure
Use of Oxygen plasma for differential etching of ordered and disordered
regions in organic samples. Rates of etching reduced from lower molecular
weight substances through disordered (amorphous) regions to ordered
(crystalline) regions. This allowed identification by replica EM
of simultaneous presence of single crystals and spherilites in Polyamide
"Improved gas-discharge etching techniques in the Electron Microscope studies
of Polyamide structures." L I Bezruk. Vysokomol. Soyed. A10: No. 6 1434-1437,
Replica EM studies of latexes of Acrylic Copolymers
Using replica EM and Oxygen ashing it was shown that latex particles
of Polyalkylacrylates and Alkylacrylate-Methacrylic Acid Copolymers
are aggregates of primary globules, the size of the globules depends
upon the polymer.
"Particle and film structures of films of some latexes of acrylic copolymers." V
I Yeliseyeva. Vosokomol. Soyed. A9: No. 11 2478-2481, 1967.
EM studies of Polyethylene Tetraphthalates films and fibres
Oxygen ashing in conjunction with replica EM revealed supra molecular
structure with correlation between EM and X-ray diffraction data.
Oxygen ashing; followed by SEM examination allowed identification
of three types of internal flaw in bright fibres. Results showed
high concentration of Titanium Dioxide in regions containing voids,
and highly ordered polymers which had previously been assumed to
"Oxygen etching method of making an Electron Microscopy study of Polyethylene
Tetraphthalate films." K Z Gumargaliyeva. Vosokomol. Soyed. 8: No. 10 1742-1744,
Quantitative bulk analysis by TEAM of biological microsamples
100 um sections of Wistar rat hearts were Oxygen plasma ashed and
then dissolved and sprayed onto grids. The droplets were then individually
analysed. The method was found to retain volatiles such as Sulphur
and possibly Chlorine. Ashing times when compared to high temperature
ashing are considerably reduced.
"The application of X-ray analysis in Transmission Electron Analytical Microscope
(TEAM) to the quantitative bulk analysis of biological microsamples." T
W Davies & A J Morgan. Journal of Microscopy Vol 107, part 1, May 1976,pp
Detection of inorganic materials in biological samples
Plasma ashed coal samples and Wandering Jew leaf observed
using SEM and EDS showed 3-5 fold improvement in detection levels
and Iron and also revealed particulates not previously observed.
Microincineration for EM localization of biological materials
A review of high temperature ashing and plasma ashing
of various materials. "Microincineration techniques for electron-microscopic
localization of biological minerals"
Richard S Thomas, W Region
Research Lab, Agricultural Research Service, US Dept. of Ag. Albany
Review of techniques for SEM and Electron Probe Microanalysis
Amongst many applications the following are highlighted: microelectronic
failure analysis; grain boundary composition in mineralogical specimens
containing silicates and carbonaceous material; discovery of microvoids
and flaws in Carbon reinforcing fibres; differential etching of polymers;
formation of 3-dimensional ash skeletons; studies of modular graphite
inclusions in cast iron; mineral staining of brain tissue followed
by Oxygen ashing.
"Use of chemically reactive gas plasma in preparing specimens for SEM and
Electron Probe Microanalysis" Richard S Thomas. SEM/1974 part 1 proc 7th
SEM Symp- April, 1974.
Low temperature ultra microincineration of thin sectioned tissue
Plasma incineration used to determine the morphological localization
of structure bound mineral and metallic elements within biological
cells at TEM levels.
"Low temperature ultra-microincineration of thin section tissue" Wayne
Hohman & Harold Shraer. Journal of Cell Biology, Volume 55 1972 pp 328-354. "Ultra-microincineration
of thin-sectioned tissue" Principles and Techniques of EM- 1976.
Ultrastructure of cell organelles in thick plasma-etched sections
1 um sections of fixed and embedded kidney tissue when surface etched
by Oxygen plasma, allowed etch resistant cell components to be imaged
with clarity. Resolution was better than other preparation techniques
for SEM of internal structures of cells and organelles in bulk samples
"Ulrastructure of cell organelles by Scanning Electron Microscopy of thick
sections and surface-etched by an Oxygen plasma" W J Humphreys. Journal
of Microscopy Vol 116 July 1979.
TEM-EDS of silica in cell walls of rye grass
A comparison of preparation methods, including plasma ashing, to
determine amounts of Silicon in cell wall material.
"Silica in the mesophyll cell walls of Italian Rye Grass" D Dinsdale
Ann. Bot 44 73-77 1979.
Plasma ashing moths and insects prior to EM and XES
Oxygen ashing of insects allowed the removal of organic material
but left the structure intact. This allowed area sectioning for subsequent
"Ashing moths and various insects" J Bowden (pr comm) Rothampstead
Research Station. July, 1979.
X-ray microanalysis of Epon sections after Oxygen plasma ashing
Improved X-ray detectability of elements retained in ash by lowered
background counts. Method removes Osmium fixative and Chlorine to
reveal hidden Phosphorous peak; pattern fidelity allows microanalytical
resolution of 0.1 um.
"X-ray microanalysis of Epon sections after Oxygen plasma microincineration" Tudor
Barnard and R S thomas. Journal of Microscopy Vol 113 Pt 3 Aug 1978, pp 269-276.
SEM of embedded biological specimens surface plasma etched
As a general technique for SEM, Oxygen plasma etching thick sections
of a wide variety of different types of embedded tissue yields specimens
that show a resolution that is considerably better than that obtainable
by most other methods; particularly for viewing internal structure
of cells and organelles in bulk structure.
"Scanning Electron Microscopy of biological specimens surface-etched by
an Oxygen plasma" W J Humphries. Scanning Electron Microscopy 1979/11.
Measuring the concentration of Asbestos in air samples
Oxygen plasma used to remove high levels of airborne organic contaminants
and to remove filter paper prior to TEM sizing.
"Asbestos counting method using TEM." Ontario Research Foundation.
Identification second counting of Asbestos fibres on membrane filters
Methods are described whereby Asbestos fibres can be counted by
phase contrast microscopy and identified on the same membrane filter
by optical and SEM techniques. Airborne concentration of different
Asbestos types in mixed clouds can therefore be estimated.
"In situ identification of Asbestos fibres collected on membrane filters
for counting" N P Vaughn and S J Rooker. Ann. Occup. Hyg. Vol 24 No 3 pp