title: Electrogenerated chemiluminescence induced by sequential hot electron and hole injection into aqueous electrolyte solution.
abstract: Hole injection into aqueous electrolyte solution is proposed to occur when oxide-coated aluminum electrode is anodically pulse-polarized by a voltage pulse train containing sufficiently high-voltage anodic pulses. The effects of anodic pulses are studied by using an aromatic Tb(III) chelate as a probe known to produce intensive hot electron-induced electrochemiluminescence (HECL) with plain cathodic pulses and preoxidized electrodes. The presently studied system allows injection of hot electrons and holes successively into aqueous electrolyte solutions and can be utilized in detecting electrochemiluminescent labels in fully aqueous solutions, and actually, the system is suggested to be quite close to a pulse radiolysis system providing hydrated electrons and hydroxyl radicals as the primary radicals in aqueous solution without the problems and hazards of ionizing radiation. The analytical power of the present excitation waveforms are that they allow detection of electrochemiluminescent labels at very low detection limits in bioaffinity assays such as in immunoassays or DNA probe assays. The two important properties of the present waveforms are: (i) they provide in situ oxidation of the electrode surface resulting in the desired oxide film thickness and (ii) they can provide one-electron oxidants for the system by hole injection either via F- and F(+)-center band of the oxide or by direct hole injection to valence band of water at highly anodic pulse amplitudes.
authors.affiliation: Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland.
authors.forename: Kalle
authors.initials: K
authors.lastname: Salminen
authors.affiliation: Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland.
authors.forename: Päivi
authors.initials: P
authors.lastname: Kuosmanen
authors.affiliation: Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Pusa
authors.affiliation: University of Helsinki, Department of Physics, P.O. Box 64, FI-00014, Finland.
authors.forename: Oskari
authors.initials: O
authors.lastname: Kulmala
authors.affiliation: Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland.
authors.forename: Markus
authors.initials: M
authors.lastname: Håkansson
authors.affiliation: Aalto University, Department of Chemistry, Laboratory of Analytical Chemistry, P.O. Box 16100, FI-00076 Aalto, Finland. Electronic address: sakari.kulmala@aalto.fi.
authors.forename: Sakari
authors.initials: S
authors.lastname: Kulmala
mesh_terms: D004566:Electrodes; D004573:Electrolytes / Q000737:chemistry*; D004583:Electrons; D016166:Free Radical Scavengers / Q000737:chemistry; D057230:Limit of Detection; D049449:Luminescence; D012996:Solutions; D014867:Water
chemical_list: D004573:Electrolytes; D016166:Free Radical Scavengers; D012996:Solutions; D014867:Water
keywords: ECL; Electrogenerated chemiluminescence; Electron injection; HECL; Hole injection; Hot electron-induced electrochemiluminescence; Tb(III) chelates