I have synthesized silver nanoparticles using electrochemical reduction of silver nitrate solution. I also added citric acid as a stabilizing agent. Please say how I can conclude that all my Ag+ is reduced to Ag0.
Aswin Av
All your silver nitrate is not and cannot be reduced to metal. Silver on the surface (top 10 - 15 atomic layers) of the particles in aqueous systems and air is in the +1 oxidation state, i.e. Ag+ and not the metal (Ag0). This is easily shown by XPS. Ag+ is the (sparingly soluble) bactericide whereas Ag0 is not soluble in water. It's the surface (charge and oxidation state) of such particles that interacts with its environment not the bulk metal. The Ag2O is easily reduced (e.g. by H2) to Ag0. For further information view this webinar (registration required):
Silver colloids and invisible ink
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W150902SilverColloidInvisibleInk.html
Aswin Av Look at the webinar and XPS or Auger is the best technique to differentiate between Ag0 and Ag+.
Aswin Av Chandan Kumar Tiwari
TPR (Temperature Programmed Reduction) with H2 will allow the amount of surface Ag+ to be quantified. I mention the technique in the webinar having been instructed in its use by a wonderful gentleman, John Jenkins, the inventor of the technique. The total silver in the system can be quantified by standard techniques such as ICP or AAS. Thus, the amount of Ag+ and Ag0 can be quantified.
I built a simple TPR system with a bent 10 mL pipette making up one arm of a katharometer detection system in a GC.
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