Autocatalytic Electrochemiluminescence

Abstract 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 (C 2 O 4 2− ) and peroxydisulfate (S 2 O 8 2− ) radicals, mediated by Ru(NH 3 ) 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 (SO 4 • − and CO 2 • − ) to populate the Ru(bpy) 3 2 ⁺* excited state. Experimental investigation at different Ru(NH 3 ) 6 3+ /S 2 O 8 2 − /C 2 O 4 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.