Tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence ethanol biosensor based on ionic liquid doped titania-Nafion composite film

A highly sensitive tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)32+] electrogenerated chemiluminescence (ECL) biosensor for the detection of ethanol based on ADH and NAD+ cofactor with ionic liquid (IL) doped sol-gel titania-Nafion composite film has been developed. Regardless of the type of the ILs, the incorporation of IL in the composite resulted in the enhancement in both the electron transfer and diffusion rates in the composite modified electrode, thus leading to dramatic increase in ECL intensity. Among several ILs tested, 1-butyl-3-methylimidazolium with chloride counter anion was most effective for the construction of the Ru(bpy)32+ ECL biosensor. Two-layer system with the inner layer of Ru(bpy)32+ immobilized in IL-titania-Nafion composite film and the outer layer of ADH immobilized in titania-Nafion composite film has been used to maintain the activity of the enzyme and the overall stability of the ECL biosensor. The present biosensor exhibited linear response towards ethanol with a linear dynamic range of 1.2 × 10−5 M-2.5 × 10−1 M and a detection limit of 5.0 × 10−6 M (S/N = 3). The outstanding dynamic range showed the applicability of the present biosensor for ethanol detection not only in human blood but also in a variety of different fields such as alcoholic beverages or other commercially available products.