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5. Surface Preparation

Table of Contents:

1. Introduction
2. Physical Considerations
3. Physical Considerations (Part 2)
4. Turbo Pumped, High Vacuum Systems
5. Surface Treatment

Freshly made carbon support films tend to be hydrophobic surface which inhibits the spreading of suspensions of particles in negative staining solutions. However, after glow discharge treatment with air, the carbon film is made hydrophilic and negatively charged, thus allowing easy spreading of aqueous suspensions. With subsequent magnesium acetate treatment, the surface is made hydrophilic and positively charged.

AtmosphereSurfaceCharge
Air Hydrophilic Negative
Air Hydrophilic Positive (With subsequent Magnesium Acetate Treatment)
Alkylamine Hydrophobic Positive
Methanol Hydrophobic Negative

In addition to glow discharge treatment using air, other process gases may be used to modify surface properties. For example, if Alkylamine is used as a process gas the carbon film surface will become hydrophobic and positively charged. On the other hand using methanol as a process gas results in the surface becoming hydrophobic and negatively charged. Such treatments can facilitate the optional absorption of selected biomolecules.

Note: The Emitech K350S or K350G, glow discharge attachment is available for subsequent surface treatment of carbon films produced with the Emitech carbon coating range, e.g. K450X, K950X. In addition separate freestanding glow discharge unit, the K100X is available.

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