Singlet oxygen phosphorescence

Scheme 1 predicts a complex decay for the singlet-oxygen phosphorescence. However, there are three simple, limiting situations. For simplicity, let us assume only two pseudophases, the lipidic and the aqueous pseudophases. The three above-mentioned situations are as follows ... 

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... 

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. 

Fig. 8 The simultaneous generation of singlet oxygen phosphorescence and erbimn(in) luminescence by an eosin-modified DTPA complex in buffered D20 (pD 8.3), dtanonstrating the ctnnpa-rable (very weak) luminescence intensities of erbium(III) luminescence and singlet oxygtai emission. Upon deoxygenation, the erbium(ni) luminescence yield increases, which shows the competition between oxygen and cu-biumflll) in the energy transfer liom eosin...

Room-temperature singlet oxygen phosphorescence can be detected at 1,270 nm with the help of an appropriate detector (e.g., Hamamatsu R5509-42 photomultiplier cooled to 193 K in a liquid nitrogen chamber), and following laser excitation (at 266, 355 or 532 nm) of aerated solutions of the samples in a laser flash photolysis spectrometer [11]. In addition, the interposition of a 600-line diffraction grating, instead of the standard spectrometer grating (1,200-line), is needed to extend spectral response to the infrared. 

Like the palladium(II) complexes, the platinum(II) porphyrins show appreciable phosphorescence even in aqueous media at room temperature in one study,169 singlet oxygen quantum yields ranged from 0.1 to 0.9 and were strongly influenced by dimerization/aggregation. Platinum(II) 5,10,15,20-tetrakis(/>-carboxyphenyl)porphyrin and platinum(II)coproporphyrin-I ((36) for Pd read Pt) have been studied as phosphorescent labels of antibodies for use in time-resolved microscopy.189... 

Beside the phosphorescence of the carbonyl compounds produced in autoxidation reactions, there is some additional luminescence by singlet oxygen 14,43) it js sometimes difficult to differentiate between emission and the longer-wavelength part of the ketone phosphorescence 38>. 

Very weak chemiluminescence (quantum yields of 6.5.. . 9.1 X 10-10) in the spectral ranges 400. 540 nm (benzaldehyde phosphorescence) and 600 nm (emission from excited singlet oxygen collision pairs)) was also observed on thermolysis of 5 with no fluorescer present. 

Jockusch, S., Sivaguru, J., Turro, N.J. and Ramamurthy, V. (2005). Direct measurement of the singlet oxygen lifetime in zeolites by near-IR phosphorescence. Photochem. Pho-tobiol. Sci. 4, 403-405... 

Although the above indirect method provided relatively accurate results, a new method of direct measurement of the IR phosphorescence of O2 ( A ) at 1270 nm was expected to improve the measurement [103]. The quantum yield of two-photon singlet oxygen generation, was calculated from... 

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