Hi,
I�m following your posts regarding the making of colloidal gold/Colloidal Silver and noticed the different types of reducing agents are being used. Coming from a non-chemistry background sometimes I struggle following and understanding the technicality behind the preference of one type over the other. Can someone summarizes the different reducing agents of choice and the difference and effectiveness of each and under what conditions.
From following your posts, I�m reading about:
Sodium Citrate
Glucose
Maltodextrin
I recall that someone mentioned that any sodium salt can act as a reducing agent as well. Is that correct.
I don't know about any sodium salt, but probably. Any metal except platinum can reduce gold. But then sodium salt is not the same as sodium metal.
Also, can these reducing agents be used to reduce other colloidal metals such as copper, zinc, platinum or palladium.
I really haven't explored other colloids very much, so I do not know.
I also read about the hydrogen peroxide, sodium carbonate, starch as catalysts and stabilizers. But noticed sometimes they are used and sometimes they are not. Could�t draw a conclusion about their importance so far.
There are many reducing agents, and while they all reduce gold chloride to gold particles, they don't all produce the same result regarding particle size and shape. I am on a permanent quest to find the best one
I can tell you though that peroxide is the absolute worst.
sodium carbonate + maltodextrin has worked best for me so far.
I had success making colloidal gold with the citrate and also with Maltodextrin. I was following the recipes very precisely but noticed that even if I add far more of the reducing agent than what has been specified it doesn�t fail. Is there any effect on stability if we are not very careful about how much of reducing agent we add?
Sorry for the long post but I was holding back throwing questions before doing enough reading on your forum.
Thanks,
Excess citrate usually resulted in ruined colloidal gold for me, as excess electrolytes in the colloidal gold reduce the repulsive forces which keep the particles apart.
Excess maltodextrin does not seem to hurt anything though.
In general, I judge the citrate or carbonate by calculating the moles of citrate/carbonate needed and then increase it a little so that there is an excess of reducing agent. This is to guarantee that no gold chloride will be left, as gold chloride is rather toxic.
When using sodium citrate with gold, the citrate is both the reducing agent and the stabilizer. When using carbonate with maltodextrin, the sodium carbonate is the reducing agent, and the maltodextrin is the stabilizer.