Physicochemical Properties of Bi-containing Ionic Liquid Analogs Based on Choline Chloride

The preparation and characterization of homogeneous and colorless ionic liquid analogs(ILAs) containing choline chloride(ChC1), malonic acid and bismuth chloride were investigated. The structure of the above mixture was preliminarily analyzed, and then the physicochemical properties including viscosity, conductivity and density were investigated as functions of temperature and composition. Additionally, the thermal stability of the ILAs and the electrochemical behavior of Bi3+ ions in the medium were studied. Structure analysis reveals that the synthesis of deep eutectic solvents(DESs) is closely related to the formation of hydrogen bonds between malonic acid and ChC1, with their viscosity, conductivity and density being greatly dependent on the temperature and composition. Thermo-gravimetric analysis demonstrates that the ILAs are very stable between room temperature and 398.15 K. And the electrochemical experiments indicate that the bismuth films can be successfully deposited from this ILAs and the deposition mechanism of bismuth is a rather irreversible process. The surface morphology of bismuth films deposited on Cu substrates was very compact and smooth. Thus, ChCl-malonic acid DESs were shown to be a good alternative to aqueous solvents for various deposition-related applications.