Does anyone explains what does Na do to cause aggregation between gold nanoparticles?
It's called 'salting out' and the double layer surrounding the particles is destroyed by the high ionic background strangth. A similat effect occurs in the delta of the Yellow River in China where the clay materials are precipitated out when the river encounters the salt of the ocean.
This is not limited to gold but holds for any colloid where electrostatic interactions are the main contribution to colloidal stability. More specifically, it is not the "Na" but rather the concentration of positive and negative ions surrounding the gold nanoparticles.
this might Tpost also be of interest: http://www.materials-talks.com/blog/2017/07/27/isoelectric-points-of-nanomaterials-qa/
Dear all.I have synthesized gold nanoparticles with CTAC as a stabilizer in water solution. The pH of nanoparticles is about 2 and I need to increase it to 6. I found that by adding NaOH or sodium acetate buffer the nanoparticles start to aggregation that I think it is because of what you mentioed in your answers. I would like to know how can I increase the pH without any change in nanoparticles' size and shape?
Thank you all for the replies. But I have a basic question, i found zeta potential for my AuNPs which is negative around -30 in buffer pH 7.5. But after aggregation with NaCl, I took the aggregate in same buffer and check the DLS and I found the zeta potential value around -40 to -45. I like to know why does zeta potential is still in negative?
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