Technical Tips

Grids: Shiny Side vs Dull Side?

Basically you need to understand that the shiny side of the grid is also the smooth side of the grid. The dull side is the side with the rougher surface - it scatters the light more than the smooth and shiny side does. If you have a section with a rough surface it will probably stick better on the rough side of the grid. Imagine a grid to be a single sided piece of sandpaper and the section to be a double sided piece of sandpaper. Sandpaper grips another piece of sandpaper much more readily than it does a smoothly polished metal surface.

For the most secure adhesion of rough sections to grids sections should be picked up on the rough side of the grid.

The smooth and shiny side of the grid is preferably used for flat specimen. Ultraflat sections (cut with a sharp diamond knife), carbon-, formvar-, SiN-films and such should be picked up with the shiny side of the grid. So flat samples stay flat and capillary action causes sticking of the two surfaces.

All coated grids come with the film laid on the shiny side of the grid!

 

Grids: Removing a Charge from the Surface of Grids

Sometimes when you are trying to pick up sections, they won’t adhere to the grid surface. If you don’t have time to glow discharge clean the grid surfaces, try this little trick. Dip the grids in distilled water for a moment and wick off the excess with filter paper. Let them dry while you are arranging your sections. Your sections should now adhere to the grid surface. Some labs soak the grids they will use for the day in distilled water until they are needed. If this procedure fails, reclean your grids with acetone or chloroform or glow discharge clean the grid surfaces.

Reference:
Jeanette Killius, NEOUCOM, Rootstown, OH.

 

On-Grid Enhancement
The use of nickel grids is recommended for on-grid enhancement, as nickel is relatively insensitive to silver enhancement. Gold or copper grids should not be used.

 

Reaction of Ni and Cu Grids

How do Nickel and Copper Grids React with Periodic Acid?

Periodic Acid + Ni → Ni-Periodate + H2
Periodic Acid + Cu → Cu-Periodate + H

In this case you should use Gold Grids.

 

Picking Up of Carbon Film

The Preparation of Adhesive Coated Grids for Picking Up Carbon Film to Make Carbon Coated Grids

The following steps should be followed in the preparation of adhesive coated grids:

  1. Submerge about 2" of Scotch clear tape (3M) into 10ml of Dichloroethane (Ethylene Dichloride); shake and discard the tape.
  2. The solution now becomes “grid-glue”.
  3. Place the grids (dull side up) on a piece of filter paper (dust-free room).
  4.  Take a pipette and place a drop of“grid-glue” on top of each grid.
  5. Let the grids dry.
  6. The grids are now ready to pick up the carbon foil and make the carbon coated grids.

 

A Simple Method for Handling Grids

A simplified method for handling EM grids is described. This new method not only offers safety and identification of your samples but offers you improved handling, temporary storage, and identification of grids bearing ultrathin sections as well as a novel method for preparing bulk samples.

Reference:
Gorycki, M. (1992). A Simple Method for Handling Grids. Biotechnic & Histochemistry 67/5, 313-314.

 

Section Pick-up with `The Perfect Loop`
The Perfect Loop (# E70944) allows you to pick up sections consistently without causing any damage to the sections. It is the only loop that is currently available where the outside diameter of the loop is the same as the grid and the inside diameter is slightly larger than the observation area of the electron microscope. The thickness is about 40 microns. Due to the fact that the loop and the grid are of the same diameter they are attracted to one another when in water and attach together through the surface tension of the water. Even if the section touches the inside of the grid during blotting the touching area is minor and, therefore, the section is not damaged. When the grid is removed from the loop the section remains in place without fail. The area equals the observation field (about 2mm diameter) of the electron microscope; thus pieces can be fully observed.