Sensitive detection of barium ion based on its enhancing effect on luminol electrochemiluminescence at cucurbit[7]uril-modified electrode

Abstract In this paper, a sensitive electrochemiluminescence (ECL) method for the detection of Ba 2+ was proposed based on its apparent enhancing effect on the anodic luminol ECL at a cucurbit[7]uril (Q[7])-modified glassy carbon electrode (Q[7]/GCE). The cavity of the modified Q[7] could accommodate more dissolved oxygen at the electrode surface which reacted with luminol to generate strong anodic ECL signal compared with a bare GCE. Ba 2+ ions exhibited further enhancing effect on luminol ECL when they were immobilized at the portal of Q[7] through chelating with carbonyl group of Q[7]. The increment of ECL signal varied linearly with the concentration of Ba 2+ , as a result, an ECL sensor for the quantitative detection of Ba 2+ was constructed. Under the optimal condition, Ba 2+ could be sensitively detected in the range of 1.0 × 10 –7 to 1.0 × 10 –4  mol L −1 , and the detection limit was calculated as 10 nM (3σ). The proposed ECL sensor exhibited satisfactory analytical performance and could be used in real samples analysis, which provided a new strategy for metal ions detection. Graphic abstract The encapsulation of dissolved oxygen by Q[7] can enrich oxygen concentration at the electrode surface, which can react with luminol to emit enhanced ECL. The presence of Ba 2+ can increase the amount of O2 •- at the electrode surface through the formation of barium-peroxide species, which can further enhance luminol ECL. Thus, an ECL sensor for the sensitive detection of Ba 2+ was built.