Electrogenerated chemiluminescence at droplet-modified electrodes: towards biphasic pKₐ measurement via proton-coupled electron transfer at liquid|liquid interfaces

Lledo-Fernandez, Carlos; Lledo-Fernandéz, Carlos; Hatay, Imren; Ball, Michael J.; Greenway, Gillian M.; Wadhawan, Jay

Abstract

This preliminary work reports, for the first time, electrogenerated chemiluminescence (ECL) at droplet-modified electrodes. The system involves oxidation of aqueous tris(2,2′-bipyridyl)ruthenium(ii) ions at a glassy carbon electrode on which a random array of microdroplets of a highly hydrophobic tertiary amine (trioctylamine) are immobilised. Luminescence, produced via electron transfer over the cupola surface of the droplets from the oil to aqueous tris(2,2′-bipyridyl)ruthenium(iii) ions synthesised via intra muros electrochemical oxidation at the uncovered parts of the electrode surface, is demonstrated. The extent of ECL production is shown to be dependent on the degree of interfacial protonation, with a proton-coupled biphasic electron transfer reaction occurring when the liquid|liquid interface is fully protonated, changing to a biphasic outer-sphere electron transfer mechanism when the interface is fully deprotonated. The competition and gradual dominance of one of these extreme mechanisms under intermediate interfacial protonation conditions thence enables the sensitive, kinetic estimation of the biphasic pKₐ.

Citation

Lledo-Fernandéz, C., Hatay, I., Ball, M. J., Greenway, G. M., & Wadhawan, J. (2009). Electrogenerated chemiluminescence at droplet-modified electrodes: towards biphasic pKₐ measurement via proton-coupled electron transfer at liquid|liquid interfaces. New journal of chemistry = Nouveau journal de chimie, 33(4), 749-759. https://doi.org/10.1039/b810844g

• Journal Article Type: Article
• Publication Date: Apr 20, 2009
• Deposit Date: Nov 13, 2014
• Journal: New Journal Of Chemistry
• Print ISSN: 1144-0546
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 33
• Issue: 4
• Pages: 749-759
• DOI: https://doi.org/10.1039/b810844g
• Keywords: electrogenerated chemiluminescence, biphasic pKa measurements,
• Public URL: https://hull-repository.worktribe.com/output/461063
• Contract Date: Nov 13, 2014