I want to make a 1M solution of PbI2 in DMF. I mixed 460 mg PbI2 in 1 ml DMF and kept it for overnight stirring at 70 oC and found that only about 40 % of PbI2 was dissolved in DMF. How can I solve this solubility problem?
The solubility of ionic compounds is generally related to the dielectric constant of the solvent, the higher the better. Water is 78 but DMF is 36.7. Below 10 and few ionic compounds are soluble to any significant extent. PbI2 in DMF will be ionised, with four DMF molecules datively associated or bound to each Pb2+. Thus you can pull more PbI2 into solution if a suitable ligand is present or added.
Some salts need more than gentle heat and time to reach a saturated solution. Place your DMF and lead iodide in an ultrasonic bath for an hour or more. This method gets sparingly soluble salts to become a saturated solution in an hour that otherwise would take two weeks of standing or shaking.
Well, maybe you have hit the limit of solubility. Is it known to be soluble to 1M in DMF? If not, can you scale your process down and use a 0.1M or 0.2M solution? There may be ways of increasing the solubility, but they would involve adding other species to solution, and the lead-containing species might not be "PbI2" anymore.
Thank you Kyle for your answer. But I have seen many research papers with 1M PbI2 solution in DMF. I don't know how they managed to dissolve it.
The solubility of ionic compounds is generally related to the dielectric constant of the solvent, the higher the better. Water is 78 but DMF is 36.7. Below 10 and few ionic compounds are soluble to any significant extent. PbI2 in DMF will be ionised, with four DMF molecules datively associated or bound to each Pb2+. Thus you can pull more PbI2 into solution if a suitable ligand is present or added.
Some salts need more than gentle heat and time to reach a saturated solution. Place your DMF and lead iodide in an ultrasonic bath for an hour or more. This method gets sparingly soluble salts to become a saturated solution in an hour that otherwise would take two weeks of standing or shaking.
Check this paper.
"Reproducible Fabrication of Efficient Perovskite-based Solar Cells: X-ray Crystallographic Studies on the Formation of CH3NH3PbI3 Layers "
- Chem. Lett. 2014, 43, 711–713 | doi:10.1246/cl.140074
The dehydrated PbI2 dissolved easily in DMF.
or you can get the PbI2/dmf solution if increase the temperature until 100oC.
It will not be fully soluble, since it depends on many parameters. Supplier, dmf it self, dryness of PbI2 etc. Since there are so many methods published now, for perovskite, getting the clear bright yellow solution of PbI2 is the main point, before spin coating. At the end of solubility period (70C, 1hr), from mostly hazy solution, you can use syringe filter (2 micrometer) to get clear bright yellow solution.
Those interested at this discussion may possibly find useful to check the following somewhat related discussion: https://www.researchgate.net/post/Which_organic_solvents_can_be_used_to_disolve_PbI2_or_PbCl3_crystals
As your research work is just focus on improvement of solubility of PbI2 in DMF, so you cant add any external excipients to improve solubility. If addition of other ingredients or co-solvents is permited then you can use sodium lauryl asulphate, Tweeen 80, SPan 80, or any other cosolvent slike DMSO.If addition of other excipients not permitted then agitation, sonication will improve solubility, But scuh appraoaches cant improve solubility from 40% to 100%.
1 M (460 mg) of PbI2 is fully soluble in 1 ml DMF at 700C for over night stirring. PbI2 in DMF is transparent yellowish solution at 70C but at room temperature it,s converted into gel like appearance but after heating it again converted into transparent solution. I have prepared this solution many times for the 2 step perovskite coating. In your case I think there is problem with PbI2 purity. I am using PbI2 of sigma (98% Purity).
Griffiths Sir, you are right, By mistake 460 gm was mentioned..it is 460 mg PbI2 in 1ml DMF.
Can PbBr2 be completely dissolved in DMF? I tried to make a solution of PbBr2 in DMF by keep it in stirring for the period of 15 hrs at room temperature.but it didn't dissolve well.then i kept the solution at 70C ,slowly it got dissolved but after half an hour stirring it was precipitated in white colour. why this happened?How can I get a solution of PbBr2 in DMF?
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