Growing crystals in ionic liquids
Crystallisation is an important process for a number of industries such as pharmaceuticals and electronics, as well as for researchers studying protein structure. ILs can be used as additives to influence the crystallisation process, but little is known about the underlying mechanisms of ILs as solvents. The 'Crystallization in iIonic liquid solutions' (CRYSTILS) project used IL additives to elucidate the relationship between IL and the crystallisation process in an aqueous (water-based) solution. The project aimed to design an aqueous solvent with predictable and controllable crystallisation properties. A model system was set up using the precipitation of barium sulphate crystals in various IL-containing solutions. The first major finding of the project was a link between the conductivity of the IL used and the size of the precipitating crystalline particles. The model system also revealed the fundamental properties of nucleation in aqueous ionic solutions, such as different precipitation effects at the liquid surface and interior. In general, the properties observed were true for both inorganic and protein crystals. Finally, CRYSTILS used these findings to synthesise inorganic crystals with specific properties. This included complex crystal structures, permeable crystals and crystals with internal cavities. The experimental knowledge gained over the course of the CRYSTILS project provides a solid foundation for future work in this new field. Understanding the relationship between ILs in solution and the precipitation of crystals from that solution will allow for manufacture of novel functional materials.
Keywords
Crystals, ionic liquid, crystallisation, protein structure, solvents, precipitation, nucleation, aqueous ionic solution, inorganic crystal, functional material
