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Photoluminescence intensity potential

Fig. 52. Effect of additive ionization potentials on the pliotoluminescence intensity ( ) and the rate R) of the photocatalytic hydrogenation of the added unsaturated hychocarbons with H2O on TiOi (O). /q and are maximum photoluminescence intensities, respectively, under vacuum (or in Ni) and in the presence of added compounds 1, 1,3-butadiene 2, 1-butylene 3, propylene 4,1-butyne 5,1-propyne 6, ethylene 7, acetylene. Photoluminescence spectra recorded at 77 K photocatalytic reactions carried out at 298 K [reproduced with permission from Anpo el al. (223)]. Fig. 52. Effect of additive ionization potentials on the pliotoluminescence intensity ( ) and the rate R) of the photocatalytic hydrogenation of the added unsaturated hychocarbons with H2O on TiOi (O). /q and are maximum photoluminescence intensities, respectively, under vacuum (or in Ni) and in the presence of added compounds 1, 1,3-butadiene 2, 1-butylene 3, propylene 4,1-butyne 5,1-propyne 6, ethylene 7, acetylene. Photoluminescence spectra recorded at 77 K photocatalytic reactions carried out at 298 K [reproduced with permission from Anpo el al. (223)].
In many cases, the photoluminescence intensity of -type electrodes at negative potential does not attain a constant value as would be expected from Eq. (16) [25]. Hysteresis is also frequently encountered in cyclic scanning experiments [25]. Such effects are due to potential-dependent changes in the surface chemistry. Under accumulation conditions in aqueous solution, hydrogen is evolved and may be incorporated into the electrode. In addition, the semiconductor may undergo... [Pg.76]

The choice of new complexes was guided by some simple considerations. The overall eel efficiency of any compound is the product of the photoluminescence quantum yield and the efficiency of excited state formation. This latter parameter is difficult to evaluate. It may be very small depending on many factors. An irreversible decomposition of the primary redox pair can compete with back electron transfer. This back electron transfer could favor the formation of ground state products even if excited state formation is energy sufficient (13,14,38,39). Taking into account these possibilities we selected complexes which show an intense photoluminescence (0 > 0.01) in order to increase the probability for detection of eel. In addition, the choice of suitable complexes was also based on the expectation that reduction and oxidation would occur in an appropriate potential range. [Pg.160]

If the internuclear equilibrium distance of the excited electronic state (r s) shifts by the value A from the internuclear equilibrium distance of the ground state ( e). the Franck-Condon principle allows transitions to many excited vibrational levels. The shapes of the harmonic potentials also have an effect on the magnitude of the Franck-Condon integral. In this case, the theoretical intensities have been calculated as a function of A and B. The parameters B and A were varied until the theoretical intensities showed the closest match to the experimental intensities. In Fig. 21, the best fit for the progression obtained from the photoluminescence spectrum for the anchored vanadium oxidc/Si02 catalyst and theoretical Franck-Condon analysis is represented (725). [Pg.163]

Silicon nanoparticles (Si NPs) with sizes in the order of bulk exciton Bohr radius [1, 2] present interesting optical properties for fluorescent labeling in biological imaging applications with their potential nontoxicity [3-6], However, the origin of their photoluminescence has been subjected to intense debate for almost two decades. This debate has been focused on whether quantumatomic-scale defects at the surface of the nanocrystals are responsible for the light emission [7]. [Pg.135]

Photoluminescence (PL), like photocurrent, is a technique in which a light flux incident on the working electrode acts as a perturbation. In this case, the response of the system is followed by measuring the intensity of the emitted hght. As in photocurrent measurements, the electrode potential can be used as an additional variable. As explained in Sect. 2.1.2.2, photocurrent is obtained when, under depletion conditions, electrons and holes created... [Pg.68]

The opto-electrical property of the ZnO/Pt IPMC was characterized using photoluminescence (PL). In order to understand the PL quenching phenomenon, measurements of the PL spectrum as a function of the potential were carried out with potential variation of 0-2.0 V. Fig 3.14 (a) shows the variation of PL spectra of the ZnO/PT IPMC recorded at the room temperature using an excitation wavelength of 280 nm. The spectra of the sample displays a broad emission band with some vibronic structure from 350 to 500 nm and the maximum emission wavelength is Xmax = 468 nm. The blue emission is believed to originate from intrinsic defects, particularly interstitial zinc [Fang et al. (2004)]. The maximum PL intensity is observed... [Pg.74]


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