Luminescence electrogenerated

Wallace WL, Bard AJ (1979) Electrogenerated chemi-luminescence. 35. Temperature-dependence of the ECL efficiency of Ru(bpy)32+ in acetonitrile and evidence for very high excited-state yields from electron-transfer reactions. J Phys Chem 83 1350-1357... 

Let us now briefly outline the structure of this review. The next section contains information concerning the fundamentals of the electrochemistry of semiconductors. Part III considers the theory of processes based on the effect of photoexcitation of the electron ensemble in a semiconductor, and Parts IV and V deal with the phenomena of photocorrosion and light-sensitive etching caused by those processes. Photoexcitation of reactants in a solution and the related photosensitization of semiconductors are the subjects of Part VI. Finally, Part VII considers in brief some important photoelectrochemical phenomena, such as photoelectron emission, electrogenerated luminescence, and electroreflection. Thus, our main objective is to reveal various photo-electrochemical effects occurring in semiconductors and to establish relationships among them. 

Fig. 35. Occurrence of electrogenerated luminescence with the participation of excited charge carriers in a semiconductor without (I) and with (II) energy levels in the forbidden band involved and , are the energies of surface and bulk levels, respectively.

Fig. 36. Electrogenerated luminescence spectra for semiconductor electrodes. is luminescence intensity energies corresponding to maxima on the curves are shown in the figure (in electron-volts). [From Pettinger et al. (1976).]...

Thus, the study of electrogenerated luminescence spectra may give information on the energy of recombination centers. This method was used to study recombination properties of photoelectrodes in cells for solar energy conversion (Ellis and Karas, 1980). 

Photoelectrochemistry (PEC) is emerging from the research laboratories with the promise of significant practical applications. One application of PEC systems is the conversion and storage of solar energy. Chapter 4 reviews the main principles of the theory of PEC processes at semiconductor electrodes and discusses the most important experimental results of interactions at an illuminated semiconductor-electrolyte interface. In addition to the fundamentals of electrochemistry and photoexcitation of semiconductors, the phenomena of photocorrosion and photoetching are discussed. Other PEC phenomena treated are photoelectron emission, electrogenerated luminescence, and electroreflection. Relationships among the various PEC effects are established. 

Electrogenerated luminescence (ECL) Luminescence produced by electrode reactions. Also called electroluminescence or electrochemiluminescence. 

Bard and co-workers have pointed out that it is frequently difficult to attribute the electrogenerated luminescence unambiguously to the process discussed above [62]. In several cases, instead of reaction (Eq. 10.29), the reduced species is also formed at a semiconductor electrode leading to the annihilation process (Eq. 10.27). This difficulty is caused by the fact that the reduction potential of a molecule in the dark ( Frejjox(M/ M )) is frequently rather close to the oxidation potential of the excited molecule ( predox(MVM)) (see e.g. Fig. 10.3). Luttmer and Bard found one system, rubrene, for which these two potentials are well separated. These authors observed a luminescence due to electron transfer from a ZnO electrode to the oxidized species of rubrene [62j. Another interesting example is the formation of an excited molecule by transfer of hot electrons, as already discussed in Section 7.8. 

Marquette C, Leca B, Blum LJ. Electrogenerated chemiluminescence of luminol for oxidase- based fibre-optic biosensors. Luminescence 2001 16 159-65. 

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