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[Suppression of singlet oxygen luminescence by porphyrins and metalloporphyrins].

The luminescene of 1O2 (1270 nm) has been observed upon illumination of air saturated solutions of different porphyrins and their complexes with Zn in CCl4. In solutions of Co-, Cu-, Ni- and Fe-porphyrins this luminescence has not been revealed. All the porphyrins studied have shown to quench 1O2, the rate constants of the "physical" and "chemical" quenching being measured. The physical way of quenching is found to be much more effective. The quenching activity of the pigments depends greatly on the presence and nature of the central metall atom incorporated into porphyrin (H2 less than Cu less than Zn less than Co approximately Ni approximately Fe) increases with hydrogenation of the semiisolated double bonds (porphyrins are less active than chlorins and bacteriochlorins).

Chemical Phenomena↗
PubMed1983

Singlet oxygen production by lactoperoxidase.

Infrared chemiluminescence with maximum intensity near 1270 nm was detected in the lactoperoxidase, H2O2, Br- system. No emission was observed when heat-inactivated enzyme was used or when Br- or H2O2 was deleted from the system. The chemiluminescence was increased by a factor of 42 +/- 5 (mean +/- S.E.) in 98% 2H2O. These results are strong evidence for the production of 1O2 in this system.

Bromides↗
PubMed1993

The linear energy transfer dependence of excited singlet-state lifetimes of hydrocarbon liquids exposed to X rays.

The absorption of X rays in liquids provides low-energy electrons in the energy range 2 to 20 keV when synchrotron radiation is used as the X ray source. Such low-energy electrons have short ranges and produce a dense track of ionization where dE/dx = 10(7) to 10(8) eV/cm. Fluorescent molecules provide a sensitive probe of the early-time structure of such tracks. From the extent of quenching of excited states and the consequent decrease in fluorescence lifetimes, the concentration of free radicals in the track can be inferred. Experiments done with the hydrocarbons cis-decalin and dodecane demonstrate this effect. In both hydrocarbons, the lifetimes (tau) are significantly smaller with excitation by X rays than with UV radiation, and tau-1 increases linearly with dE/dx.

Alkanes↗