Jinal Pothupitiya

Only thing I would add would be to consider the size of the staining molecule in relation to the size of the nanoparticle. The radius of an uranium atom is 230 pm and thus would add 0.92 nm (molecules either side of the nanoparticle) to the diameter of any nanoparticle (plus uranyl acetate is larger). One would be considering the use of a stain for a low optical contrast material which could be small. No issue with a 100 nm particle where an extra 0.92 nm probably means little other than taking it out of the 1 - 100 nanometer definition... Big issue for a 5 nm particle where nearly 20% of the diameter is added by the stain.

Uranil acetate and phosphotungstic acid are old, reliable negative stains, much cheaper than nano stains. It's easy to check which stain is better for your task and/or more convenient. Of course, if you already have good results, why to bother?

Jinal Pothupitiya

Only thing I would add would be to consider the size of the staining molecule in relation to the size of the nanoparticle. The radius of an uranium atom is 230 pm and thus would add 0.92 nm (molecules either side of the nanoparticle) to the diameter of any nanoparticle (plus uranyl acetate is larger). One would be considering the use of a stain for a low optical contrast material which could be small. No issue with a 100 nm particle where an extra 0.92 nm probably means little other than taking it out of the 1 - 100 nanometer definition... Big issue for a 5 nm particle where nearly 20% of the diameter is added by the stain.

With negative staining we do not increase particle size. Negative staining is surrounding a particle, not sticking to it. So, no trouble here. Anyway, size of stain particle/molecule should be much lees than one of a particle of interes.