Author: Baagi Thema Mmereki
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494026014
Category :
Languages : en
Pages : 328
Book Description
We have also measured the kinetics and products of a reaction between gas-phase ozone and anthracene adsorbed at the air-aqueous interface. The reactions at the "uncoated" air-water interface and at an interface consisting of a monolayer of various organic compounds were studied. In all the cases, the reaction follows a Langmuir-Hinshelwood mechanism, in which ozone first adsorbs to the air-aqueous interface, and then reacts with adsorbed anthracene. For typical atmospheric ozone concentrations, the estimated reactive uptake coefficient ranges from 2 x 10-8 to 3 x 10-7 depending on the nature of the air-aqueous interface. Smaller (C4, C6) carboxylic acids at the interface inhibit the reaction (compared to the "clean" water surface); 1-octanol enhances it. Under some circumstances, oxidation by ozone on aqueous surfaces may be more important in the atmosphere than gas phase oxidation by OH radicals. The fate of atmospheric semi-volatile organic compounds (SOCs) such as polycyclic aromatic hydrocarbons (PAHs) depends, in part, on their distribution between the gas phase and particulate phases, and oxidation reactions. In the daytime troposphere, photochemically produced OH radicals dominate these reactions, whereas chlorine atoms may contribute to the oxidation of certain PAHs in coastal areas. In the dark, oxidation by nitrate radicals (NO3) may also be important, whereas ozone can contribute to the oxidation both during the day and at night. We have developed a laser-induced fluorescence (LIF) method to study adsorption and oxidation of PAHs at the air-aqueous interface. This method allows to directly probe the mechanisms and extent of PAH uptake on aqueous surfaces. The kinetics of the adsorption of anthracene and pyrene onto "pure" water and water coated with an organic film were measured. The surface uptake coefficients of both PAHs are estimated to be on the order of 10-5, and increase by a factor of 2--3 for uptake to the 1-octanol coated water surface. However, the surface uptake of pyrene to a hexanoic-acid-coated aqueous surface does not display this enhancement. Resolved fluorescence spectra of pyrene adsorbed onto 1-octanol-coated surfaces indicate that pyrene is in a less polar environment than when adsorbed at the hexanoic-acid-coated surfaces.
Laser Induced Fluorescence Study of the Heterogeneous Interaction of Polycyclic Aromatic Hydrocarbons with Aqueous Surfaces [microform] : Adsorption and Reaction with Gas-phase Ozone
Author: Baagi Thema Mmereki
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494026014
Category :
Languages : en
Pages : 328
Book Description
We have also measured the kinetics and products of a reaction between gas-phase ozone and anthracene adsorbed at the air-aqueous interface. The reactions at the "uncoated" air-water interface and at an interface consisting of a monolayer of various organic compounds were studied. In all the cases, the reaction follows a Langmuir-Hinshelwood mechanism, in which ozone first adsorbs to the air-aqueous interface, and then reacts with adsorbed anthracene. For typical atmospheric ozone concentrations, the estimated reactive uptake coefficient ranges from 2 x 10-8 to 3 x 10-7 depending on the nature of the air-aqueous interface. Smaller (C4, C6) carboxylic acids at the interface inhibit the reaction (compared to the "clean" water surface); 1-octanol enhances it. Under some circumstances, oxidation by ozone on aqueous surfaces may be more important in the atmosphere than gas phase oxidation by OH radicals. The fate of atmospheric semi-volatile organic compounds (SOCs) such as polycyclic aromatic hydrocarbons (PAHs) depends, in part, on their distribution between the gas phase and particulate phases, and oxidation reactions. In the daytime troposphere, photochemically produced OH radicals dominate these reactions, whereas chlorine atoms may contribute to the oxidation of certain PAHs in coastal areas. In the dark, oxidation by nitrate radicals (NO3) may also be important, whereas ozone can contribute to the oxidation both during the day and at night. We have developed a laser-induced fluorescence (LIF) method to study adsorption and oxidation of PAHs at the air-aqueous interface. This method allows to directly probe the mechanisms and extent of PAH uptake on aqueous surfaces. The kinetics of the adsorption of anthracene and pyrene onto "pure" water and water coated with an organic film were measured. The surface uptake coefficients of both PAHs are estimated to be on the order of 10-5, and increase by a factor of 2--3 for uptake to the 1-octanol coated water surface. However, the surface uptake of pyrene to a hexanoic-acid-coated aqueous surface does not display this enhancement. Resolved fluorescence spectra of pyrene adsorbed onto 1-octanol-coated surfaces indicate that pyrene is in a less polar environment than when adsorbed at the hexanoic-acid-coated surfaces.
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494026014
Category :
Languages : en
Pages : 328
Book Description
We have also measured the kinetics and products of a reaction between gas-phase ozone and anthracene adsorbed at the air-aqueous interface. The reactions at the "uncoated" air-water interface and at an interface consisting of a monolayer of various organic compounds were studied. In all the cases, the reaction follows a Langmuir-Hinshelwood mechanism, in which ozone first adsorbs to the air-aqueous interface, and then reacts with adsorbed anthracene. For typical atmospheric ozone concentrations, the estimated reactive uptake coefficient ranges from 2 x 10-8 to 3 x 10-7 depending on the nature of the air-aqueous interface. Smaller (C4, C6) carboxylic acids at the interface inhibit the reaction (compared to the "clean" water surface); 1-octanol enhances it. Under some circumstances, oxidation by ozone on aqueous surfaces may be more important in the atmosphere than gas phase oxidation by OH radicals. The fate of atmospheric semi-volatile organic compounds (SOCs) such as polycyclic aromatic hydrocarbons (PAHs) depends, in part, on their distribution between the gas phase and particulate phases, and oxidation reactions. In the daytime troposphere, photochemically produced OH radicals dominate these reactions, whereas chlorine atoms may contribute to the oxidation of certain PAHs in coastal areas. In the dark, oxidation by nitrate radicals (NO3) may also be important, whereas ozone can contribute to the oxidation both during the day and at night. We have developed a laser-induced fluorescence (LIF) method to study adsorption and oxidation of PAHs at the air-aqueous interface. This method allows to directly probe the mechanisms and extent of PAH uptake on aqueous surfaces. The kinetics of the adsorption of anthracene and pyrene onto "pure" water and water coated with an organic film were measured. The surface uptake coefficients of both PAHs are estimated to be on the order of 10-5, and increase by a factor of 2--3 for uptake to the 1-octanol coated water surface. However, the surface uptake of pyrene to a hexanoic-acid-coated aqueous surface does not display this enhancement. Resolved fluorescence spectra of pyrene adsorbed onto 1-octanol-coated surfaces indicate that pyrene is in a less polar environment than when adsorbed at the hexanoic-acid-coated surfaces.
An in Situ Laser-induced Fluorescence System for Polycyclic Aromatic Hydrocarbon-contaminated Sediments
Author: Timothy Grundl
Publisher:
ISBN:
Category : Contaminated sediments
Languages : en
Pages : 54
Book Description
Publisher:
ISBN:
Category : Contaminated sediments
Languages : en
Pages : 54
Book Description
Laser-induced Fluorescence of Pyrene and Other Polycylic Aromatic Hydrocarbons (PAH) in Seawater
Analytical Laser Induced Fluorescence and Phosphorescence Spectrometry of Aromatic Hydrocarbon Derivatives Prepared in Vapor Deposited Parent Molecule Matrices
Author: Charles Finley Pace
Publisher:
ISBN:
Category : Fluorescence spectroscopy
Languages : en
Pages : 516
Book Description
Publisher:
ISBN:
Category : Fluorescence spectroscopy
Languages : en
Pages : 516
Book Description
Fluorescence Study of Polycyclic Aromatic Hydrocarbons and Their Interactions with Bovine Serum Albumin
Author: Steven R. Masuda
Publisher:
ISBN:
Category : Bacteriology
Languages : en
Pages : 194
Book Description
Publisher:
ISBN:
Category : Bacteriology
Languages : en
Pages : 194
Book Description
Laser Induced Fluorescence Studies of Water by Electron Impact
Low Temperature Laser-induced Fluorescence Studies of Chromophores in Soft Solids and Biological Matter
Author: Chen Lin
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Low-temperature laser-induced fluorescence spectroscopy has various applications in analytical, physical, and biophysical chemistry. This technique provides information on the fluorescence origin band, zero-phonon lines and phonon-sidebands, inhomogeneous broadening, electron-phonon coupling strength, and ground- and excited-state vibrational frequencies of studied molecules. Examples discussed in this work include studies of DNA/metabolites and monoclonal antibody (mAb)/antigen interactions. The structural basis for the increased reactivity of BPDE towards guanines at 5-methylcytosine ([superscript]M[superscripte]eC):G sites in DNA was investigated by low temperature laser-based spectroscopy, studying the nature of physical complexes of benzo[a]pyrene tetraol in a series of 5-methylcytosine structural DNA analogs. We found that the presence of a C-5 substituent on cytosine and related structural modifications influences the conformation of BPT in DNA analogs, and could explain the increase in guanine reactivity at [superscript]M[superscript]eC:G sites of the p53 tumor suppressor gene that contains endogenenous 5-([superscript]M[superscript]eC. It has been demonstrated that various mAbs can bind a particular cross-reactant by adopting two distinct "red" and "blue" conformations of its binding sites. We showed that the blue conformation of pyrene in several mAbs (including 4D5 mAb) is consistent with [pi]-cation interactions, underscoring the importance of [pi]-cation interaction in ligand binding. We propose that considerable narrowing of the fluorescence origin band of the ligand in the protein environment could be regarded as a simple indicator of [pi]-cation interactions. It is also shown that time-resolved delta fluorescence line-narrowing ([delta]FLN) spectroscopy, using excitation within the (0,0)-transition band, provides more reliable information of the frequency dependence of the electron-phonon coupling (Huang-Rhys factor, (S
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Low-temperature laser-induced fluorescence spectroscopy has various applications in analytical, physical, and biophysical chemistry. This technique provides information on the fluorescence origin band, zero-phonon lines and phonon-sidebands, inhomogeneous broadening, electron-phonon coupling strength, and ground- and excited-state vibrational frequencies of studied molecules. Examples discussed in this work include studies of DNA/metabolites and monoclonal antibody (mAb)/antigen interactions. The structural basis for the increased reactivity of BPDE towards guanines at 5-methylcytosine ([superscript]M[superscripte]eC):G sites in DNA was investigated by low temperature laser-based spectroscopy, studying the nature of physical complexes of benzo[a]pyrene tetraol in a series of 5-methylcytosine structural DNA analogs. We found that the presence of a C-5 substituent on cytosine and related structural modifications influences the conformation of BPT in DNA analogs, and could explain the increase in guanine reactivity at [superscript]M[superscript]eC:G sites of the p53 tumor suppressor gene that contains endogenenous 5-([superscript]M[superscript]eC. It has been demonstrated that various mAbs can bind a particular cross-reactant by adopting two distinct "red" and "blue" conformations of its binding sites. We showed that the blue conformation of pyrene in several mAbs (including 4D5 mAb) is consistent with [pi]-cation interactions, underscoring the importance of [pi]-cation interaction in ligand binding. We propose that considerable narrowing of the fluorescence origin band of the ligand in the protein environment could be regarded as a simple indicator of [pi]-cation interactions. It is also shown that time-resolved delta fluorescence line-narrowing ([delta]FLN) spectroscopy, using excitation within the (0,0)-transition band, provides more reliable information of the frequency dependence of the electron-phonon coupling (Huang-Rhys factor, (S
Sensitized Fluorescence for the Detection of Polycyclic Aromatic Hydrocarbons
Author: Emmett Matthew Smith
Publisher:
ISBN:
Category : Aromatic compounds
Languages : en
Pages : 28
Book Description
Publisher:
ISBN:
Category : Aromatic compounds
Languages : en
Pages : 28
Book Description
Absorption and Laser Induced Fluorescence Spectra of Some Aromatic Molecules
The Application of Laser Induced Fluorescence to the Study of Electron Impact Excitation of Atoms and Molecules [microform]
Author: Peter W. Zetner
Publisher: National Library of Canada
ISBN: 9780315207486
Category :
Languages : en
Pages : 462
Book Description
Publisher: National Library of Canada
ISBN: 9780315207486
Category :
Languages : en
Pages : 462
Book Description