Effects of water on ionic liquid electrochemical microsensor for oxygen sensing

Abstract The effect of water on ionic liquid (IL) planar electrochemical microsensor was studied in the case of sensing oxygen. This study compared the key analytical performances of the IL based electrochemical microsensor devices using an IL BmimBF 4 direct from the vendor and ‘wet’ BmimBF 4 containing different amount of water as electrolytes. The electrochemical properties in [Bmim][BF 4 ] with or without oxygen using a planar microsensor device were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). With the increasing of water concentrations in the IL, a positive shift of redox potential of O 2 and a higher reduction current of oxygen in CV measurement were observed. The constant potential chronoamperometry measurements were conducted to assess the sensitivity, reproducibility and stability of microsensor at varying O 2 concentration using these wet ILs as electrolytes. The short term and long-term stability evaluation of these IL microsensor for sensing oxygen was performed. Our results show that the electrochemical planar microsensor device demonstrates a good sensitivity, reproducibility and stability for sensing oxygen even though the ‘wet’ ILs were used as electrolytes. A remarkable stability of sensor was observed in stability test using as an electrolyte.