A simple strategy for enhancing the detection limits of blue-green ECL emitters

Ultra-low detection limits of metal complexes are achievable using electrochemiluminescence (ECL). However, the limit of detection (LOD) can be retarded by background ECL which arises from electrogenerated oxygen excimers in the diffusion layer. In this study, the blue-green ECL of [Ir(dF(CF3)ppy)2(dtbbpy)](PF6), (where dF(CF3)ppy = 2-(2,4-difluorophenyl)-5-trifluoromethylpyridine, and dtbbpy = 4,4′-di-tert-butyl-2,2′-dipyridyl), in aqueous media is reported, using tri-n-propylamine as the co-reactant. The use of a short-pass optical filter virtually eliminates the red background ECL from measurements. This significantly alters the signal to background ratio, resulting in a considerably lower LOD of 1 nM for the luminophore, despite its relatively weak ECL in aqueous media. The results suggest a general and easily implemented strategy to improve detection limits of non-red ECL emitters.