Exams have kept me busy this week but I have read some interesting papers. The papers have clear diagrams of the experimental setup used and some nice TEM images of the nanoparticles that were produced. Both papers I have posted to the ctools page use a similar setup to ours. One setup does use a magnetic stirrer to mix the sample with the intention of having the particles be exposed to multiple pulses to narrow the size distribution and try to get rid of large agglomerates. They also aged the colloids for a few months then evaluated the sizes again. The aging narrowed the size distribution and reduced the number of large agglomerates. I think it would be interesting to see if this is actually due to time or if centrifuging a sample would have the same effect.
The other paper details why the colloids are stable. They say that the colloid is so stable is because the zeta potential is large (-35mV). This means that the Au nanoparticles in water are charged and thus repel each other in water. This electrostatic repulsion keeps the particles separated and thus they do not clump together and precipitate out. I am interested to see if other papers claim that aging does narrow the distribution of sizes and I will search for a bit information about about the zeta potenital and the stability of the nanoparticle colloids.
