Theoretical analysis of sulfur dioxide–imidazolium ionic liquid interaction and its application in electrochemical sensing

Sulfur dioxide (SO 2 ) is a common atmospheric pollutant. Its testing is mandatory, especially in the areas of occupational health and safety. In this work, the interaction of SO 2 and [Emim]BF 4 was studied firstly by quantum chemical calculations. The results showed that the adsorption of SO 2 by ionic liquids (ILs) was primarily governed by physical interactions dominated with electrostatic forces. The strength of weak interactions between [Emim] + and [BF 4 ] - exceeded that of X-H˙˙˙O type weak hydrogen bonds, indicating no substitutional adsorption of SO 2 at the [BF 4 ] site. Electron flow towards SO 2 was confirmed through density difference mapping during all three adsorption processes. Finally, the electrochemical behaviors of SO 2 on the [Emim]BF 4 modified screen-printed electrodes (SPEs) were studied by Differential Pulse Voltammetry (DPV), Electrochemical Impedance Spectroscopy (EIS) and Amperometric i-t curve (I-t), respectively, and an electrochemical sensor for SO 2 was set up. This work is necessary for understanding the mechanism of SO 2 capture by ILs, rationally designing the functional ILs, and promoting their application in sensing pollutant gases.