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In the preparation of $\ce{Ag}$ doped $\ce{ZnO}$ thin films by sol-gel method, I dissolved zinc acetate in 2-propanol while adding DEA and the solution is ready.

After that I added different concentrations of $\ce{AgNO3}$ to the solution, stirring on a stirrer, starting with $0.005$ concentration, but I found that it didn't completely dissolved even after $20$ minutes, and it gets harder for higher concentrations. Can I get any help for this?

Ahmed Razeen
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We all learn right away (Chem I) that most silver salts are insoluble - except nitrate - in water, but how soluble are they in isopropanol? That lonely alcohol functional group may not give the same "umph" that water would for the dissolution of the Mighty Silver Cation.

Normally, you'd start with a ZnOAc dihydrate salt, so there's gonna be some water in your mix to dissolve the nitrate, but if you're going for an {aq.} soluble salt in ethanol, did you consider just adding DI to the mix?

What about changing your starting components to include the silver and zinc salts together in dissolution before adding the alcohol? Add them both gravimetrically ratioed as salt to your alcohol solvent and use the DEA to assist in solvation. There's docs on this, let me know if you can't find them.

Update:(moved from a second answer, ed.)

So we actually just tried using water to help dissolve the ZnOAc and AgNO3 in the ethanol solution and we found that adding DI water dropwise did help to dissolve the ZnOAc, but after aging overnight a cloudy precipitate had developed, after googling around a bit, I saw that water in ethanol could react with ZnOAc to form ZnOH. In order to test this, I added ~3M Nitric Acid dropwise, and it cleared up the solution. Unfortunately, the solution then failed to stick to our slides when spin-coating.

The good news is, the solution with the cloudy ZnOH actually produced similar XRD results to the solution without water added. We have been using monoethanolamine as a stabilizer to help dissolve the ZnOAc. MEA acts as a bidentate ligand to hold the Zn+ ions in solution. I should have a parametric analysis on a ZnO sol-gel process published by the end of semester - will post it when available.

Additionally, note from Ahmed's comment below. Silver salts tend to be extremely photosensitive, so the smallest amount of exposure of their solutions may cause discoloration. We have had improved success by performing as many steps as possible in darkness, and/or by covering glassware with aluminum foil.
Reed Thomas
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  • I tried adding silver and zinc salts together before adding the alcohol, increased the spinning period, and it worked and the solution dissolved, giving gradient brown colors for different concentrations of Ag salt from 0.005 to 0.5. – Ahmed Razeen Mar 13 '17 at 12:18