Detection of transient absorption in a dyed cotton fabric and in semiconductor powders by diffuse reflectance laser flash photolysis

1985 ◽  
pp. 142 ◽  
Author(s):  
Frank Wilkinson ◽  
Charles Willsher
Keyword(s):  
Cotton Fabric ◽  
Diffuse Reflectance ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash

Intrazeolite photochemistry. IV. Studies of carbonyl photochemistry on the hydrophobic zeolite Silicalite using time-resolved diffuse reflectance techniques

1986 ◽  
Vol 64 (3) ◽  
pp. 539-544 ◽  
Author(s):  
F. Wilkinson ◽  
C. J. Willsher ◽  
H. L. Casal ◽  
Linda J. Johnston ◽  
J. C. Scaiano
Keyword(s):  
Diffuse Reflectance ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Heterogeneous Systems ◽  
Laser Flash ◽  
Close Packing ◽  
Time Resolved ◽  
Adsorption Sites ◽  
Norrish Type

Transient absorption and luminescence from aromatic ketone triplets (xanthone, acetophenone, butyrophenone, valerophenone, p-methoxyacetophenone, β-phenyl-p-methoxypropiophenone and benzil) supported on the hydrophobic zeolite Silicalite have been obtained by time-resolved diffuse reflectance laser flash photolysis. These experiments were aimed at establishing the usefulness of this technique for studies of zeolite supported photoreactions. While the transient spectral properties can be used to examine the properties of the supporting media, the decays of the signals frequently follow complex kinetic behaviour. The decays for such heterogeneous systems cannot be easily fit to clean first or second order kinetics and are thought to be a mixture of several first order decays arising from triplets in different inclusion and adsorption sites. Evidence is presented for close-packing of the aromatic substrates and for triplet lifetime enhancement. Although the triplet spectrum of included benzil shows evidence for considerable axial freedom, the results for β-phenylpropiophenones indicate that other types of motion are restricted for included ketones. It is also found that the rate of the Norrish Type II reactions of valerophenone and butyrophenone supported on Silicalite are decreased with respect to the rates in solution.

scholarly journals Surface photochemistry: Photodegradation study of pyrene adsorbed onto microcrystalline cellulose and silica

2004 ◽  
Vol 6 (4) ◽  
pp. 205-213 ◽  
Author(s):  
A. S. Oliveira ◽  
L. F. Vieira Ferreira ◽  
J. P. Da Silva ◽  
J. C. Moreira
Keyword(s):  
Radical Cation ◽  
Microcrystalline Cellulose ◽  
Ground State ◽  
Diffuse Reflectance ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Cation Radical ◽  
Laser Flash ◽  
Time Resolved

Ground-state diffuse reflectance, time resolved laser-induced luminescence, diffuse reflectance laser flash-photolysis transient absorption and chromatographic techniques were used to elucidate the photodegradation processes of pyrene adsorbed onto microcrystalline cellulose and silica. Ground-state diffuse reflectance showed that on both substrates low concentrations display absorption of pyrene monomers. At high concentrations spectral changes attributed to aggregate formation were observed. Laser induced fluorescence showed that pyrene onto microcrystalline cellulose mainly presents fluorescence from monomers, while for silica, excimer-like emission was observed from low surface loadings (≥0.5μmolg−1). Transient absorption and photodegradation studies were performed at concentrations where mainly monomers exist. On silica, pyrene presents transient absorption from its radical cation. On microcrystalline cellulose both radical cation, radical anion and pyrene triplet-triplet absorption were detected. Irradiation followed by chromatographic analysis showed that pyrene decomposes on both substrates. For pyrene on microcrystalline cellulose 1-hydroxypyrene was the main identified photoproduct since in the absence of oxygen further oxidation of 1-hydroxypyrene was very slow. For pyrene on silica photodegradation was very efficient. Almost no 1-hydroxypyrene was detected since in the presence of oxygen it is quickly oxidized to other photooxidation products. On both substrates, pyrene radical cation is the intermediate leading to photoproducts and oxygen it is not involved in its formation.

Triplet state quenching of phenosafranine dye by indolic compounds studied by transient absorption spectroscopy

2015 ◽  
Vol 14 (2) ◽  
pp. 407-413 ◽  
Author(s):  
Martín F. Broglia ◽  
Carlos M. Previtali ◽  
Sonia G. Bertolotti
Keyword(s):  
Triplet State ◽  
Absorption Spectroscopy ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Absorption Spectroscopy ◽  
Synthetic Dye ◽  
Biological Relevance ◽  
Indolic Compounds

The interaction of the triplet state of the synthetic dye phenosafranine (3,7-diamino-5-phenylphenazinium chloride) with indolic compounds of biological relevance was investigated in water by means of laser flash photolysis.

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