Solid-state tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence sensor based on ionic liquid/sol–gel titania/Nafion composite film

• ECL sensor was fabricated based on IL/titania/Nafion composite-modified GC electrode.
• Hydrophobic IL of BMImPF6 was mixed in the composite solution.
• The present ECL sensor showed improved ECL sensitivity for TPA.
• The selectivity of the present ECL sensor could be controlled by selecting IL.

The feasibility of being able to control the selectivity of solid-state tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)32+) electrogenerated chemiluminescence (ECL) sensor is proposed by selecting ionic liquids with appropriate hydrophobicity in the sol–gel titania/Nafion composite film. Four different kinds of ionic liquids with different hydrophobicity such as 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6), 1-ethyl-3-methylimidazolium hexafluorophosphate (EMImPF6), 1-hexyl-3-methylimidazolium hexafluorophosphate (HMImPF6), 1-benzyl-3-methylimidazolium hexafluorophosphate (BnMImPF6) were incorporated in the sol–gel titania/Nafion composite films. The sequence of the observed ECL intensities for hydrophobic analytes is closely related to the sequence of the hydrophobicity of the ionic liquids used in the composite-based ECL sensor. In contrast, the observed ECL sequence for hydrophilic analytes such as ascorbic acid and oxalate is the opposite to the sequence of the hydrophobicity of the ionic liquids used in the composite film. Due to the decreased electron transfer resistance in the ionic liquid-based sol–gel titania/Nafion composite films, the present ECL sensor based on the BMImPF6/titania/Nafion composite film gave a remarkable detection limit (S/N = 3) of 0.48 nM for TPA.

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