Novel Mechanism Insight for Enhanced Electrochemiluminescence Signal

Abstract

Electrochemiluminescence (ECL) is a leading technique in bioanalysis.[1] Since the excited species are produced with an electrochemical stimulus rather than with a light excitation source, ECL displays improved signal-to-noise ratio compared to photoluminescence, with minimized effects due to light scattering and luminescence background. The most challenging breakthrough in the development of analytical electrochemiluminescence (ECL) applications was reported from Bard and co workers that presented for the first time the generation of ECL with a coreactant.[1] This finding opened the application of ECL to large literature and transformed ECL from an academic curiosity to a real application and industrial success. In this context, the only real used materials for the ECL analytical and commercial application are tripropylamine (TPrA) as sacrificial ”oxidative-reductant” coreactant and Ruthenium(II)-tris(2,2’-bipyridine) ([Ru(bpy)3]2+) as emitting species. In this case the mechanism for the ECL generation was proposed by Bard and still nowadays the only one accepted.[2],[3]Here we show an additional, and very efficient, mechanism pathway for the generation of ECL by using TPrA as coreactant. Thanks to the combination between ECL and microscopy we experimentally prove the alternative mechanism with the standard [Ru(bpy)3]2+/TPrA system.[3],[4] These mechanistic findings allow us to propose alternative amines as coreactant enhancing the ECL signal of more than one order of magnitude.The reported results, besides contributing to a better understanding of the mechanisms operating in the chemiluminescence generation, also pave the way for the development of very highly efficient ECL coreactants for ultrasensitive bioanalysis.[5][1] Miao W.; Choi J. P.; Bard A. J., J. Am. Chem. Soc. 2002, 124, 14478-14485[2] Sentic M.; Milutinovic M.; Kanoufi F.; Manojlovic D.; Arbault S.; Sojic N., Chem. Sci. 2014, 5, 2568-2572[3] Valenti G.; Scarabino S.; Goudeau B.; Lesch A.; Jović M.; Villani E.; Sentic M.; Rapino S.; Arbault S.; Paolucci F.; Sojic N., J. Am. Chem. Soc. 2017, 139, 16830-16837.[4] a) Valenti G.; Zangheri M.; Sansaloni S. E.; Mirasoli M.; Penicaud A.; Roda A.; Paolucci F., Chem. Eur. J., 2015, 21, 12640–12645; b) Zanut A.; Fiorani A.; Rebeccani S.; Kesarkar S.; Valenti G., Anal. Bioanal. Chem., 2019, 411(19), 4375-4382.[5] Zanut A. at al Nature Commun. 2020, 11, 2668 Figure 1