Hi,
We using 3-aminopropyltrimethoxysilane to self-assemble gold nanoparticles on glass fibers. I've been coating the gold monolayers with carboxy-PEG-thiols. I've noticed that after we put these fibers into phosphate buffer saline (0.14mM salt), they seem to undergo baseline instabilities; sometimes for hours. It also appears that the baseline effect may be proportional to the amount of carboxy on the surface, although its hard to say for sure.
We are wondering what underlying mechanism is causing this baseline effect. Do you think the negatively charged gold particles are more likely to aggregate or move around the monolayer when in a salt-containing solution?
Search for answer in "Ionic Strength-Controlled Deposition of Charged Nanoparticles on a Solid Substrate", The Journal of Physical Chemistry C. 01/2011; 115(39):19096-19103.
Baseline effect is due to negatively charged GPs. Baseline can be reduced by changing the Solution
Thanks Jan, I will read up on that.
Muhammad, do you have any recommended resources where I can learn more about this?
Hi Adam, not sure if I got your question right, but it seems to me that in a highly saline solution (high Ionic Strength), the high ionic concentration will "shield" all the ionic interactions, including the COO- +H3N one, a well known effect. In other words, the higher the ionic strength, the weaker the electrostatic interactions between charged particles and other charged particles or charged surfaces.