Influence of solvents on the quantum efficiency of laser-excited delayed fluorescence of phthalocyanine sensitised by singlet oxygen

Journal Article · Sun Feb 28 00:00:00 EST 1999 · Quantum Electronics (Woodbury, N.Y.)

DOI:https://doi.org/10.1070/QE1999V029N02ABEH001439· OSTI ID:21439460

Bashtanov, M E; Krasnovskii, A A ^[1]

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1. A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow (Russian Federation)

An investigation was made of the intensity ratios of the phosphorescence of singlet oxygen {sup 1}O{sub 2} at {lambda} = 1270 nm (L{sub 1270}) and of the {sup 1}O{sub 2}-sensitised delayed fluorescence (L{sub df}) of tetra-(4-tert-butyl)phthalocyanine (Pc) in hexafluorobenzene, benzene, and acetone were also studied. Tetraphenylporphine and Pc were used as photosensitisers of O{sub 2} formation. Excitation was provided by a pulsed nitrogen laser emitting at {lambda} = 337 nm. The ratio L{sub df}{sup 0} =L{sup 0}{sub 1270} of the initial intensities of the delayed fluorescence of Pc and of the {sup 1}O{sub 2} phosphorescence varied from 14 to 70, depending on the energy of the laser pulses (1 - 2 mJ cm{sup -2}), on the Pc concentration (0.25 - 1.2 {mu}M), and on the nature of the photosensitiser and its optical density (0.1 - 0.2) in the excitation region. A criterion of the quantum efficiency of the delayed fluorescence was defined as the coefficient {alpha} = (L{sub df}{sup 0}/L{sub 1270}{sup 0}k{sub r}/{gamma}{sub f}) [{sup 1}O{sub 2}]{sub 0}[Pc], where [{sup 1}O{sub 2}]{sub 0} is the initial concentration of {sup 1}O{sub 2} after a laser pulse; [Pc] is the concentration of Pc; k{sub r} is the rate constant of radiative deactivation of {sup 1}O{sub 2} in the investigated solvent; {gamma}{sub f} is the quantum yield of the Pc fluorescence. Within the limits of the experimental error, the coefficient {alpha} was the same for all the investigated media and amounted approximately to 4 x 10{sup 13} M{sup -2} s{sup -1}. An analysis of the results indicated that the quantum efficiency of the delayed fluorescence of Pc excited in aprotic media remained high irrespective of the presence and number of hydrogen atoms in the solvent molecule and also independent of the solvent permittivity in the range 2.3(benzene) - 21.5(acetone). (laser applications and other topics in quantum electronics)

• OSTI ID: 21439460
• Journal Information: Quantum Electronics (Woodbury, N.Y.), Vol. 29, Issue 2; Other Information: DOI: 10.1070/QE1999v029n02ABEH001439; ISSN 1063-7818
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACETONE
BENZENE
DEACTIVATION
EXCITATION
FLUORESCENCE
HYDROGEN
LASER RADIATION
LASERS
NITROGEN
OPACITY
ORGANIC FLUORINE COMPOUNDS
OXYGEN
PERMITTIVITY
PHOSPHORESCENCE
PHTHALOCYANINES
PULSES
QUANTUM EFFICIENCY
REACTION KINETICS
SOLVENTS
AROMATICS
DIELECTRIC PROPERTIES
DYES
EFFICIENCY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
ENERGY-LEVEL TRANSITIONS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
KETONES
KINETICS
LUMINESCENCE
NONMETALS
OPTICAL PROPERTIES
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PHOTON EMISSION
PHYSICAL PROPERTIES
RADIATIONS