Electrochemiluminescence of an iridium complex doped with SiO2 nanoparticles to detect 2-adamantanamine based on the host–guest interaction of cucurbit[7]uril

Abstract

The poor solubility of iridium complexes severely hampers its application in the electrochemiluminescence (ECL) sensing field. The doping of an iridium complex with silica (SiO₂) nanospheres provides feasible solution for this problem. Herein, one kind of water insoluble iridium complex ([Ir(dFppy)₂(d(CF₃)bpy)](PF₆)) was doped with SiO₂ nanoparticles to obtain a luminescent nanocomposite (SiO₂@Ir) which could generate strong ECL signals to act as a beacon molecule. An “off–on–off” mode ECL sensor was proposed based on the competitive host–guest interactions between 2-adamantanamine (2-ADA), ferrocene (Fc) and cucurbit[7]uril (Q[7]). Fc could be used as an inhibitor to decrease the ECL signal, while Q[7] could wrap Fc to recover the ECL signal. Q[7] has a stronger binding ability with 2-ADA than Fc. As a result, 2-ADA could replace Fc from the cavity of Q[7], and the ECL signal was inhibited again. Under the optimal conditions, the ECL intensity varied linearly with 2-ADA concentration in the range of 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 2.5 × 10⁻¹⁰ mol L⁻¹. The results not only provided a new avenue for the application of water insoluble iridium complexes in ECL sensing, but also revealed the attractive potential of host–guest interactions in the fabrication of biosensors.