There is limited information provided in internet regarding this. Thallium iodide is water insoluble and slightly soluble in acetone. But I am looking for solvents in which TlI will be completely soluble.
In this case, I suggest you using a solvent system consisting of a surfactant, preferably non-ionic surfactant with very low HLB such as Lauroglycol (Gattefosse) with a cosolvent such as PG or PEG-400.