An ionic liquid-mediated electrochemiluminescent sensor for the detection of sulfur dioxide at the ppb level

Abstract

A novel portable SO₂ gas sensor based on ionic liquid (IL) mediated electrochemiluminescence (ECL) for detecting SO₂ at the ppb levels has been developed. The sensing system for SO₂ detection is based on the strong quenching effect of SO₂ on the ECL of the tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺)/O₂ coreactant system in the IL film. Over the potential window between −1.0 and +1.3 V, O₂ can act as an effective coreactant for Ru(bpy)₃²⁺ ECL in ILs, giving a bright ECL emission. The ECL of the Ru(bpy)₃²⁺/O₂ system can be strongly inhibited by SO₂ through the direct quenching of the excited state of the luminophore, i.e. Ru(bpy)₃²⁺*, by SO₂ molecules. The inhibited ECL intensity is proportional to the concentration of SO₂ in the range from 40 to 2000 ppb with a detection limit of 20 ppb. The proposed SO₂ ECL sensor can be operated at room temperature and shows high selectivity, good reproducibility and long-term stability in a dry atmosphere.