Phosphorescence, of singlet oxygen

R. Dedic, A. Svoboda, J. Psencik, L. Lupinkova, J. Komenda, J. Hala, Time and spectral resolved phosphorescence of singlet oxygen and pigments in photosystem II particles, J. Luminesc. 102-103, 313-317 (2003)... 

Fig. 15.4 Plots of the initial phosphorescence of singlet oxygen at 1,270 nm as a function of laser Intensity for l//-phenalen-l-one and an oligothiophene derivative in air-saturated toluene solutions at 293 K. Reproduced with permission from Ref. [95], Copyright 2006, the American Chemical Society...

When the above conditions are met, the kinetics of singlet-oxygen decay will be monoexponential and the effect of the quencher upon the steady-state singlet-oxygen phosphorescence will present similar characteristics in the micellar... 

The photophysical properties of Ceo and C70 have been reported.Ceo does not display any detectable fluorescence or phosphorescence, but is an efficient producer of singlet oxygen ( O2) with a quantum yield of unity (532nm). The properties of C70 are similar, except that a weak fluorescence is now apparent and the quantum yield of O2 is slightly less than unity. These differences are explained by the lower symmetry of the C70 molecule relaxing the forbidden nature of some of the absorption and emission processes. In addition, the fluorescence, phosphorescence, and nonlinear optical... 

It should be emphasized that the measurement of the singlet oxygen phosphorescence intensity at 1270 nm confirmed the values <1>A for the porphyrins but gave systematically lower values for the bacteriochlorins. PAC measures the amount of heat released in the formation of transient species, whereas phosphorescence at 1270 nm measures the aunoimt of singlet oxygen species. The apparent discrepancy between the two techniques may be related to the natime of the species that are formed from the triplet state of bacteriochlorins in the presence of oxygen and will be discussed in the next section. 

Figure 10.2 Graphical representation of Metal-Enhanced Fluorescence (Top), Metal-Enhanced Phosphorescence (Middle), and for the generation of Singlet Oxygen (Bottom). F - Fluorophore, RB - Rose Bengal, P - Phosphorescence and MEP - Metal-Enhanced Phosphorescence, 302 — triplet ground state oxygen. 102 -singlet oxygen. Adopted from ref [25].

Chignell (1987) developed a near-infrared detective system, based on the phosphorescence emission of the excited singlet oxygen, under steady state conditions. Using this technique, Motten et al. (1999) have determined the quantum yields of singlet oxygen formation for a series of antimalarial drugs in D20 as shown in Table 12.2. 

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