Ultraweak emission of the Eu(III) ions in cathodic generated electrochemiluminescence

Abstract High voltage cathodic generated electrochemiluminescence (ECL) of selected systems generating weak photon emission was studied. The investigated systems contained europium salts, and co-reactants: H2O2 and K2S2O8. During the cathodic pulse polarization of an oxide-covered working aluminum electrode, hot electrons in metal may enter the conduction band of water through the oxide layer/solution interface and turn into hydrated electron after salvation. The ECL intensity and spectra was measured though a suitable cut-off filters, with a photon counting unit attached to a PC computer. On the basis of the analysis of the spectra in particular systems, emitters were identified and simplified scheme of the processes was proposed. The Eu(III)-specific electro generated luminescence is produced via several parallel mechanisms, which usually involve a type of the co-reactant, oxidation state changes of europium ions in aqueous solution and the influence of working electrode surface emission.