Scheme 1. Schematic description of the chemical lens strategy applied to the ECL mechanism of a microbead (Ru@bead) functionalized with the ECL luminophore ([Ru(bpy)3]2+), here denoted as Ru2+. The tri-n-propylamine (TPrA) coreactant is oxidized at the electrode generating the cation radical (TPrA˙+) that deprotonates to give the neutral radical (TPrA˙). The neutral radical and then the cation radical react sequentially with [Ru(bpy)3]2+ immobilized on the magnetic beads and generate its excited state. [PB] indicates a variation of the phosphate buffer concentration that allows controlling the thickness of the ECL-emitting layer. On the right, both optical configurations used to image the functionalized beads are presented: (i) top view and (ii) side view. P1 is the product of homogeneous TPrA˙ oxidation with [Ru(bpy)3]2+.
