As most people here I have become used to evaluate the process, presence of AgNP, particle size and concentration based on colloid color. As soon as the colloid shows a strong yellow color we know that we have about 20-25 ppm concentration (cross-referencing mA and time), caused by the Plasmon effect.
I have reduced and capped nano silver using many different protocols, some with application of heat, some at or slightly above room temperature.
When I do a citrate reduction/capping, that has to be done at 70-80°C, I generally heat up the water, add the sodium carbonate, glucose (to ensure full reduction) and citrate, and then insert the silver electrode. I noted that when I wait a minute or ten, the water will color bright yellow even if no silver is present. As the Maillard reaction should not take place at such low temperatures, I was puzzled, but now I learned that sodium carbonate will drastically lower the temperatures for the Maillard reaction to happen.
So my question is: When heat reducing nano silver, how can I be sure that it is indeed reducing, or am I just looking at a yellow solution because of the Maillard reaction?
Also: If it is a combination of the Maillard reaction and Plasmon effect, how can I evaluate yellow/amber colors with respect to concentration? Any thoughts?