Investigation of ionic liquids under Bi-ion and Bi-cluster ions bombardment by ToF-SIMS.

A systematic study of five different imidazolium-based room temperature ionic liquids, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium nitrate, 1-butyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide were carried out by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in positive and negative ion mode. The compounds were measured under Bi-ion and Bi-cluster ions (Bi(2-7)(+), Bi(3, 5)(2+)) bombardment, and spectral information and general rules for the fragmentation pattern are presented. Evidence for hydrogen bonding, due to high molecular secondary cluster ions, could be found. Hydrogen bonding strength could be estimated by ToF-SIMS via correlation of the anionic yield enhancement with solvent parameters.