Autocatalytic Electrochemiluminescence

Electrochemiluminescence (ECL) is a powerful analytical technique that generates light through electrochemically induced reactions, enabling ultrasensitive biosensing and imaging of submicrometric objects. Conventional ECL systems, such as those using Ru(bpy)₃ ²⁺ and tri-n-propylamine (TPrA), require high applied potentials (oxidation at ∼1.4 V versus Ag/AgCl), leading to electrode surface modification and parasitic reactions. Herein, we present a novel autocatalytic ECL mechanism that drastically lowers the triggering potential to -0.2 V by exploiting the synergistic interplay between oxalate (C₂O₄ ^2-) and peroxydisulfate (S₂O₈ ^2-) radicals, mediated by Ru(NH₃)₆ ³⁺ reduction. This system generates ECL without direct oxidation of the luminophore, but instead through a mild reduction process, relying on homogeneous radical reactions (SO₄ ^• ^- and CO₂ ^• ^-) to populate the Ru(bpy)₃ ²⁺* excited state. Experimental investigation at different Ru(NH₃)₆ ³⁺/S₂O₈ ² ^-/C₂O₄ ² ^- concentration ratios, backed by finite element simulations, demonstrates the autocatalytic cycle's capability of exciting luminophores with a bandgap as high as 2.77 eV (blue-emitting Ir(III) complex), while also showing a more stable ECL emission and achieving an emitting layer as thick as ∼4.8 ± 0.2 µm. These findings establish a low-potential ECL pathway with a large emitting layer, extending the applicability of such nontoxic coreactants-historically limited by their short-lived radicals-and potentially paving the way for new frontiers in ECL.