Oxidative-Reduction Co-reactants

B ard and co-workers in 1977 observed ECL emission from oxalate in acetonitrile [8]. Later, they observed it in aqueous solutions following mechanism as shown in Eqs. (2.13)-(2.19) for the detection of oxalate and Ru(bpy)3 [10, 14]. In the following years, a fiber-optic-based ECL sensor for oxalate detection was constructed [18], and the reaction mechanism of the oxalate system was further investigated and applied to study the electron transfer at liquid/liquid interface [19]. Simultaneous electrochemical and ECL detection of oxalate was reported in 2000 by Forster et al. [20]. 

ECL generated by oxidation of Ru(bpy)3, Ru(phen)3, Ru(bpy)2(dmbp) Ru-(dmphen)3, or Ru(dmbp)3 (dmbp) 4,4 -dimethyl-2,2 -bipyridine (dmphen), 4,7-dimethyl-l,10-phenanthroline, and oxalate in aqueous solution was attributed to the driving force for the electron-transfer reactions and the different pathways for co-reactant (i.e., C02 ) reaction [19]. 

Further studies on the ECL intensity of the Ru(bpy)3 /TPA system reveals that it strongly depends on the solution pH. A large number of ECL applications in biological systems appear in literature, owing to its feature that the maximum value of 

ECL can also be generated via hot electrons emitted into electrolyte solution from an oxide-covered electrode surface, sometimes called a conductor/insulator/elec-trolyte surface [53]. This special light emission pathway in ECL is commonly known as hot-electron-induced ECL [54—56], where hot electrons are defined as 

Soon afterward, a detection method for Ru(bpy)3 based on the ECL of Ru(bpy)3 and persulfate on oxide-covered aluminum electrode [60] and Ru(bpy)3 in acetonitrile and aqueous solution on oxide-covered tantalum electrode was developed [11]. The ECL intensity showed linearity in the concentration range of 10 ° M and 10 M Ru(bpy)3 in the presence of 1 mM persulfate. The sensitivity was improved by an order of magnitude in the presence of Tween 20, and this technique was applied to immunoassays. The ECL emission on oxide-covered 

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Keywords Annihilation Pathway Electron-transfer reaction Gibbs free energy Energy sufficient reaction Reductive-oxidation co-reactant Oxidative-reduction co-reactant Hot-electron ECL... 

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