A novel host–guest recognition electrochemiluminescence system for phenylalanine detection based on Ir@ZnO nanocomposites and cucurbit[8]uril

Iridium complexes have been considered as potential promising electrochemiluminescent (ECL) reagents in recent years. However, the instability of ECL signal and easy leaching from the electrode severely limit their applications. In this work, iridium complex doped zinc oxide (ZnO) nanocomposites (Ir@ZnO) were synthesized, which could not only increase the loading amount of iridium complex, but also improve the stability of ECL signal. A sensitive ECL sensor for the detection of phenylalanie (Phe) was proposed via the host–guest recognition of cucurbit[8]uril (Q[8]) and Phe with Ir@ZnO nanocomposites as a signal probe. Q[8] was combined with Ir@ZnO nanocomposites via coordinate bond between carbonyl group of Q[8] and Ir and Zn atoms, which could quench the ECL intensity due to the accommodating ability of Q[8] for dissolved oxygen. In the presence of Phe, Q[8] could be released from the electrode surface through the strong host–guest interaction, and the ECL intensity was restored. The ECL system performed high sensitivity and low detection limit, indicating that the proposed ECL strategy was suitable for the detection of amino acids. Moreover, this work provided a new avenue for the application of water insoluble Ir complexes in ECL sensing field.