Greetings Katarina,

I have not dealt with silver nanoparticles suspended in a hydrogel but I have dealt with polymers and silver nanoparticles separately so here are my two cents.

Like you mentioned, after 24 hours of drying the polymer probably cured on the surface of your sample, giving it a cloudy top surface and making TEM viewing impossible. To tackle this, i would suggest the following:

1) Dry the specimen for a much shorter period of time and view the samples before the polymer has time to crosslink too much and become cloudy.

2) Instead of dropping a blob of solution (drop casting) on I assume a Cu TEM window and letting it dry, how about spin coating your substrate instead? That way you can achieve a much thinner layer.

3) Another possibility would be for you to ion mill the sample after the cloudy surface forms. Ion milling results in a shallow wedge like structure that would still provide a lot of viewing surface area. That way, you could still view the silver nanoparticles that are sandwiched in between the cloudy opaque polymer films.

Thats all I can think of for now, hope it turns out well!

Regards

Janel

I do not think you can get advice with exact procedure for your specimens. You need to find it by yourself.

After you put drop on a grid, do not leave it as is. It's too much of solution for TEM. Touch side of a grid with a filter paper to absorb most of a liquid from a grid. Try much lower concentrations of solution. Good luck.

If you have no use for the hydrogel, you could try dialysis to get rid of it prior to supplying the sample to the grid. Otherwise washing a few times on the EM grid could help bring down the concentration. Just blot with filterpaper, add water and blot again. You can repeat this a few times and indeed don't let the full amount dry, but blot prior to drying. You can try to avoid losing the nanoparticles by waiting a minute each time before blotting.

Greetings!

PVOH after freeze-drying procedure have a cellular sponge-like structure, where are walls of the bigger caverns contain the smaller caverns. Yesterday I examined a sample with immobilized bacterial cells in PVOH. SEM resolution is adequate for this pourpose, samples cut off from the gel after freeze-drying. Diamond and glass knives crumple the structures, I found that ordinary razor blades are better. When you drying samples without freezing, your samples fold up into a thick layer and you just can't reach 20-50 nm for TEM.