that's interesting. So the nano-particles stay stable while the water evaporated to the point the PVA finally bonds and hardens? I wonder if this works for the silver as well.
When in a liquid PVA acts as a surfactant, "holding apart" the nanoparticles. As the water evaporates, the molecules form a polymer lattice, and the particles get stuck in. I'm not sure when the surfactant properties stop working while dehydrating, but the films look fairly uniform. I haven't bothered to do any tests on them.
Silver works as well. It's not as pretty though
. Though I've been making some wacky coloured silver nanoparticles. I cant keep them for very long before they crash out. I use polystyrene sulfonate for stabilization in one method of silver np synthesis. I may try PVA next week. Maybe I'll make a concentrated batch and make a few films.