Plasma Chemistry Applied to Electron Microscopy (EM) Preparation Procedures

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
samples.

"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.

Source unknown.

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 68.

"Improved gas-discharge etching techniques in the Electron Microscope studies of Polyamide structures." L I Bezruk. Vysokomol. Soyed. A10: No. 6 1434-1437, 1968.

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 be defusants.

"Oxygen etching method of making an Electron Microscopy study of Polyethylene Tetraphthalate films." K Z Gumargaliyeva. Vosokomol. Soyed. 8: No. 10 1742-1744, 1966.

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 47-54.

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 for Sulphur and Iron and also revealed particulates not previously observed.

Source unknown

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 CA USA.

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 of tissue.

"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 analysis.

"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 281-290 1981.