Metal Ion Solubility in Deep Eutectic Solvents

Recent work on deep eutectic solvents (DES) has demonstrated that these novel H-bonded liquids can be used to modify nanomaterial morphologies under mild conditions in solvothermal syntheses. In addition to being inexpensive, non-flammable and having low volatility, it has been shown that DES can be excellent solvents for a variety of transition metal species. However the solubility of, for instance, metal oxides varies dramatically with the solvent type and molar ratio of the components. Here we wish to better understand how metal ions are solvated in DES using the example of p-toluenesulfonic acid:choline chloride DES, which dissolves substantial amounts of many transition metal oxides. The solubility of ZnO in this DES is much higher when a molar ratio of 2:1 is used than at a ratio of 1:2. We will probe the DES structure at these ratios and how addition of Zn2+ perturbs the structure