Particle Diffusion Odds and Ends
PES Membranes:
I tested 100 and 300kD PES membranes from Pall. 5 and 20 nm particles were used in both water and 10mM KCl. I won’t show all of the data, but I didn’t see any particles in any of the filtrates by absorbance or DLS. The filters were also stained red after the experiments. I’m guessing the particles are sticking to some extent and are unable to weave their way through these filters by diffusion.
(liberated PES membrane, rinsed 2x diH2O)
Pnc-Si retrial:
Since I hadn’t repeated the original study with the 5 nm particles in KCl, I reused one of the membranes that was initially used for the 10nm particle diffusion studies earlier. After 1 day it appeared neither 5 or 20 nm particles in 10mM KCl had gone through. I left the system set up, and checked it again after 2 more days. The retentate had dried up, but the membrane was still intact. There was a significant amount of discoloration – silver color around the slits – but this didn’t break the membrane either. Here are the absorbance curves for the filtrates:
You can see the peak in the 5nm filtrate around 525, and I could tell by eye that the gold had passed through to a very strong extent. There was nothing observable in the 20nm sample. It’s possible that because I had already used this membrane with a potentially contaminated 10nm gold solution it may have reduced the quality of the membrane, but we still see stuff going through over time.