A novel optical oxygen sensing system based on triplet–triplet reflectance of fullerene C60-polystyrene film by time-resolved spectroscopy using diffuse reflectance laser flash photolysis

The Analyst ◽  
2000 ◽  
Vol 125 (3) ◽  
pp. 523-526 ◽  
Author(s):  
Yutaka Amao ◽  
Keisuke Asai ◽  
Ichiro Okura
Keyword(s):  
Diffuse Reflectance ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Oxygen Sensing ◽  
Laser Flash ◽  
Fullerene C60 ◽  
Polystyrene Film ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Sensing System

Oxygen sensing based on lifetime of photoexcited triplet state of platinum porphyrin-polystyrene film using time-resolved spectroscopy

2000 ◽  
Vol 04 (03) ◽  
pp. 292-299 ◽  
Author(s):  
YUTAKA AMAO ◽  
KEISUKE ASAI ◽  
ICHIRO OKURA
Keyword(s):  
Triplet State ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Oxygen Sensing ◽  
Laser Flash ◽  
Quenching Rate ◽  
Time Resolved ◽  
Quenching Rate Constant ◽  
Volmer Plot ◽  
Platinum Porphyrin

Optical oxygen-sensing systems based on the quenching of the photoexcited triplet state of platinum porphyrins—platinum octaethylporphyrin (PtOEP) and platinum tetrakis(pentafluorophenyl)porphyrin (PtTFPP)—in polystyrene (PS) using two different time-resolved spectroscopies (luminescence lifetime measurement and diffuse reflectance laser flash photolysis) have been developed. Using both spectroscopies, the same values of Stern-Volmer constant KSV and quenching rate constant kq (KSV = kqτ0) are obtained. The decays of the luminescence and triplet-triplet reflectance of the platinum porphyrins in PS consisted of two components (faster and slower lifetimes) in the absence and presence of oxygen. For both faster and slower components the lifetime decreases with increasing oxygen concentration. For both components a Stern-Volmer plot of the platinum porphyrin-PS films exhibits linearity. However, kq of the faster component is larger than that of the slower component (for PtOEP, three times larger; for PtTFPP, 40 times larger), indicating that two different oxygen-accessible sites exist in the platinum porphyrin-PS films. The faster and slower components are related to oxygen-accessible sites on the surface and in the bulk of the platinum porphyrin films respectively. Concerning the fractional contributions of each lifetime component, the contribution of the faster component is greater than that of the slower component, indicating that the sensing site on the surface is important for optical sensing. The contribution of different oxygen-accessible sites in platinum porphyrin-PS films for oxygen sensing is clarified by these techniques.

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.

Structures of Reactive Nitrenium Ions:  Time-Resolved Infrared Laser Flash Photolysis and Computational Studies of SubstitutedN-Methyl-N-arylnitrenium Ions

2000 ◽  
Vol 122 (34) ◽  
pp. 8271-8278 ◽  
Author(s):  
Sanjay Srivastava ◽  
Patrick H. Ruane ◽  
John P. Toscano ◽  
Michael B. Sullivan ◽  
Christopher J. Cramer ◽  
...  
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Infrared Laser ◽  
Computational Studies ◽  
Time Resolved ◽  
Nitrenium Ions ◽  
Arylnitrenium Ions

scholarly journals Kinetic studies of C1 and C2 Criegee intermediates with SO2 using laser flash photolysis coupled with photoionization mass spectrometry and time resolved UV absorption spectroscopy

2018 ◽  
Vol 20 (34) ◽  
pp. 22218-22227 ◽  
Author(s):  
N. U. M. Howes ◽  
Z. S. Mir ◽  
M. A. Blitz ◽  
S. Hardman ◽  
T. R. Lewis ◽  
...  
Keyword(s):  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Kinetic Studies ◽  
Laser Flash ◽  
Major Product ◽  
Time Resolved ◽  
Photoionization Mass Spectrometry ◽  
Criegee Intermediates ◽  
Wide Range ◽  
Kinetics Of

Kinetics of CH2OO + SO2 confirmed over a wide range of [SO2]. Acetaldehyde observed as a major product of the reaction of CH3CHOO + SO2.

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