6/3/99

Does anyone have a reliable "recipe" for preparing holey carbon grids. I'm

using a glycerol-formvar mixture, however my holes are not very homogeneous in

size and are very sparse. Maybe there's something I'm missing - any advice?

Does anyone know if these solutions store well?

Trinh, Minh-Uyen

TRIMY002@students.unisa.edu.au

For making holey carbon films, I use polystyrene films casted from glass

slides the same way as formvar. Polystyrene films are easy to float them

off after simple Kleenex cleaning of glass slides or mica sheets.

~0.25% w/v solution of polystyrene in amyl actate results in ~ silver film.

Breathing once on a drying film will give you a whole range of diameters

from a few nm to microns. Adding a few drops of water to polystyrene

solution and sonication before casting will give you very reproducible and

uniform holes.

You can evaporate carbon onto filmed grids or onto films on slides followed

by floating off carbon coated polystyrene films.

You can easily remove polystyrene by keeping the grids on a wire net or on

a filter paper over the amyl acetate to have clean holey carbon films only.

Let me know if you need more details.

Marek Malecki

malecki@MACC.WISC.EDU

I find that the best recipe for holey grids is to order them already made

from someone like EMS. They're not that expensive, especially if you

consider what your time is worth.

Mary Gail Engle

Electron Microscopy & Imaging Facility

University of Kentucky

Mary Gail Engle

mgengle@pop.uky.edu

Thanks for your advice - much appreciated ^_^

Regarding the floating of films - I found it is important for the slides to

have a clean/hydrophilic surface. If the slides are new, it is usually ok to

just rinse the slide with a bit of detergent and wiping it dry with lint free

tissue. However, if you don't have clean slides I find the following method

for cleaning surfaces 100% successful - the film easily floats off (and if

you're skilled enough you can float both sides off at the same time).

*Place slides in a beaker containing conc. HNO3 (~60%) and boil for 1 hr, rinse

with copious amounts of Milli-Q water several times.

*Rinse with a bit of detergent and wipe dry before dipping into mixture.

To get larger holes I presume you would need to add more glycerol to the

mixture.

Trinh, Minh-Uyen

TRIMY002@students.unisa.edu.au

We use 45 ml of actetone plus 45 ml of chloroform to which 0.2 g

of formvar and

between 0.82 and 1.5 ml 90% glycerine are added. The formvar is added to the

CHCl3 and

shaken until the formvar dissolves, then the acetone and glycerol are added and

skaken vigorously

for ~10 min. The mixture is sonicated for 5 min with a probe sonicator and must

be used within

a few hours or re-sonicated. If the mix is used immediately, I get a very large

number of small

holes (~2 um), and if the mix stands for ~1 hr, I get a large number of larger

holes (~5 um).

I almost always get "wall-to-wall" holes with very thin bars of formvar

remaining. Good

luck.

I always seem to have trouble floating the films off the slides; does anyone have

any tips?

Also, I'd like to get 10-20 um holes; any tips there?

Yours,

Bill

Tivol

tivol@wadsworth.org