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I'm trying to understand the procedure used to produce AgI nanoplates described in the linked paper. Specifically, I have a few questions about the following text:

When silver acetate is in deficiency, all of silver acetate reacts with KI and only forms pure AgI nanoplates. ... However, when KI is in deficiency, i.e., silver acetate is in excess, the redundant Ag ions may be reduced by the component of EG to produce Ag NPs on the surface of AgI nanoplates (i.e., formation of Ag/AgI nanoplates).

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The AgI and heterostructured Ag/AgI nanoplates were synthesized by using simple aqueous solution, as illustrated with the schematic images in Figure S1 (Supporting Information). For the synthesis of AgI nanoplates, 9 mL of EG was taken with the addition of 0.5 × 10−3 M of silver acetate and 160 mg of PVP (K29-32) in a 20 mL vial. The solution was stirred with a magnetic stirring bar at a rate of 400 rpm for 4 min. In the second stage 1 M of KI was dissolved in deionized water, and 150 µL was added and stirred at room temperature for 10 min until the formation of a homogeneous mixture. In the next step, the vial was put into an oil bath keeping at 140 °C for 90 min with magnetic bar at a rate of 400 rpm. ... For the synthesis of heterostructured Ag/AgI nanoplates, the concentration of silver acetate was changed from 0.5 × 10−3 m to 2 × 10−3 m. The procedure and other conditions were kept same with the synthesis of AgI nanoplates.

My questions are:

  1. If I'm understanding correctly, they are reacting around 5(20) micromoles of silver acetate with 150 micromoles of Potassium Iodide. But why is 150 micromoles of KI considered a deficit for 20 micromoles of silver acetate? It seems like equals moles of both should be balanced (CH3CO2Ag + KI -> AgI + CH3COOK). How can I compute the "balanced" amount if I am wrong?
  2. Is the choice of solvent (Ethylene Glycol) and silver precursor (Silver Acetate) important for the production of AgI here? I understand that Ethylene Glycol can be a reducing agent, but is that only relevant for the production of AgI? Does the ethylene glycol do something else? I guess it provides the ability to heat it to 140C (vs water). Same on the silver precursor? Is there some significance to silver acetate (vs. for example, silver nitrate?)

Just in general, if you have any information of the production of silver halide nanoplates on the scale of 100 nm- several ums, let me know!

Thanks in advance!

Paper in question: M. U. Khan, H. J. You, X. T. Liu, L. L. Zhang, J. X. Fang, Small 2018, 14, 1702948. https://doi.org/10.1002/smll.201702948

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  • $\begingroup$ Thanks for the reply. My confusion is that the article appears to produce AgI nanoplates with a 5/150 ratio of silver to iodide, but produces AgI/Ag composites with 20/150. To me, both of these seem like an excess of iodide, and I would expect both to produce AgI nanoparticles. I am unsure of why 20 micromoles of silver acetate is seemingly considered an "excess" for 150 micromoles of KI. $\endgroup$
    – rmueller
    Commented Mar 12 at 17:50
  • $\begingroup$ Oops... my misreading. Do your calculations take into account the four-fold increase of Ag? "For the synthesis of heterostructured Ag/AgI nanoplates, the concentration of silver acetate was changed from 0.5 × 10−3 m to 2 × 10−3 m." $\endgroup$
    – DrMoishe Pippik
    Commented Mar 12 at 19:41
  • $\begingroup$ Yeah, my math is that (Volume solvent)*(M)=9ml*2 × 10−3 m ~ 20 micromoles for the silver excess case (vs 5 micromoles for the silver deficient case). Perhaps my understanding is off on that. $\endgroup$
    – rmueller
    Commented Mar 13 at 3:55

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