​Dual-Coreactants Enhanced Electrochemiluminescence.

The electrochemiluminescence (ECL) of ruthenium(II) tris(2,2'-bipyridyl) (Ru(bpy)32+) with tri-n-propylamine (TPrA) as the good coreactant can be unexpectedly enhanced by a weak coreactant, such as triethanolamine (TEOA). First, the intensity of ECL emitted by Ru(bpy)32+/TPrA can be remarkably amplified by 10.8-fold after adding some amount of TEOA. Moreover, the ECL layer thickness, measured by self-interference spectroscopy, is also doubled. The enhancement far exceeding the superposition of respective contribution of TPrA and TEOA was elucidated by a "chemical oxidation mechanism", in which TEOA+• acts as a chemical enhancer to oxidize TPrA in solution and to accelerate significantly the ECL reaction kinetics. This mechanism was proved by single-photon counting experiment and finite element simulations. In addition, the dual-coreactants strategy works well not only in solution with freely diffusive Ru(bpy)32+, but also on Ru(bpy)32+-functionalized microbeads, suggesting that ethanolamines could act as cheap, easily available and low-background enhancers for ECL-based bioanalysis and microscopy.