The Experts below are selected from a list of 6129 Experts worldwide ranked by ideXlab platform

R Volkamer - One of the best experts on this subject based on the ideXlab platform.

  • secondary Organic aerosol formation from acetylene c 2 h 2 seed effect on soa yields due to Organic Photochemistry in the aerosol aqueous phase
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: R Volkamer, P Ziemann, Mario J Molina
    Abstract:

    Abstract. The lightest Non Methane HydroCarbon (NMHC), i.e., acetylene (C 2 H 2 ) is found to form secondary Organic aerosol (SOA). Contrary to current belief, the number of carbon atoms, n , for a NMHC to act as SOA precursor is lowered to n =2 here. The OH-radical initiated oxidation of C 2 H 2 forms glyoxal (CHOCHO) as the highest yield product, and >99% of the SOA from C 2 H 2 is attributed to CHOCHO. SOA formation from C 2 H 2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosols, mild acidification with sulphuric acid (SA, 3 Y SOA ) ranged from 1% to 24% and did not correlate with the Organic mass portion of the seed, but increased linearly with liquid water content (LWC) of the seed. For fixed LWC, Y SOA varied by more than a factor of five. Water soluble Organic carbon (WSOC) Photochemistry in the liquid water associated with internally mixed inOrganic/WSOC seed aerosols is found responsible for this seed effect. WSOC Photochemistry enhances the SOA source from CHOCHO, while seeds containing amino acids (AA) and/or SA showed among the lowest of all Y SOA values, and largely suppress the photochemical enhancement on the rate of CHOCHO uptake. Our results give first evidence for the importance of heterogeneous Photochemistry of CHOCHO in SOA formation, and identify a potential bias in the currently available Y SOA data for other SOA precursor NMHCs. We demonstrate that SOA formation via the aqueous phase is not limited to cloud droplets, but proceeds also in the absence of clouds, i.e., does not stop once a cloud droplet evaporates. Atmospheric models need to be expanded to include SOA formation from WSOC Photochemistry of CHOCHO, and possibly other α-dicarbonyls, in aqueous aerosols.

  • secondary Organic aerosol formation from acetylene c 2 h 2 seed effect on soa yields due to Organic Photochemistry in the aerosol aqueous phase
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: R Volkamer, P Ziemann, Mario J Molina
    Abstract:

    Abstract. The lightest Non Methane HydroCarbon (NMHC), i.e., acetylene (C2H2) is found to form secondary Organic aerosol (SOA). Contrary to current belief, the number of carbon atoms, n, for a NMHC to act as SOA precursor is lowered to n=2 here. The OH-radical initiated oxidation of C2H2 forms glyoxal (CHOCHO) as the highest yield product, and >99% of the SOA from C2H2 is attributed to CHOCHO. SOA formation from C2H2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosols, mild acidification with sulphuric acid (SA, 3

Karine Loubiere - One of the best experts on this subject based on the ideXlab platform.

  • a revised 1d equivalent model for the determination of incident photon flux density in a continuous flow led driven spiral shaped microreactor using the actinometry method with reinecke s salt
    Journal of Flow Chemistry, 2021
    Co-Authors: Robbie Radjagobalou, Victoria Dias Da Silva Freitas, Jeanfrancois Blanco, Fabrice Gros, Jeremy Dauchet, Jeanfrancois Cornet, Karine Loubiere
    Abstract:

    Continuous-flow microstructured technologies are now recognized as promising alternatives to batch processing for Organic Photochemistry, especially when light emitting diodes (LEDs) are employed as light sources. To evaluate and optimize productivity and energetic efficiency, the knowledge of the incident photon flux density is crucial. In this context, the objectives of the present work are dual: first, to transfer the classical actinometry method with Reinecke’s salt to a continuous-flow LED-driven spiral-shaped reactor and second, to propose a revised one-dimensional equivalent model for the accurate determination of the incident photon flux density in this microreactor. Experimental measurements were carried out under controlled conditions. The effects of the spectral domain and radiant power emitted, the tubing length, the presence of gas-liquid Taylor flow, and the material of the support plate were especially investigated. An expression was established for the revised one-dimensional Cartesian model, taking into account the diffuse emission of the LED array and the reflection induced by the material of the plate in which the tubing was inserted (i.e. the reflection by the backside of the microreactor wall). In this way, the incident photon flux density could be estimated with an acceptable level of accuracy, which was not the case if the usual 1D model was applied (collimated emission and no reflection).

Michael Oelgemoller - One of the best experts on this subject based on the ideXlab platform.

  • studies in Organic and physical Photochemistry an interdisciplinary approach
    Organic and Biomolecular Chemistry, 2016
    Co-Authors: Michael Oelgemoller, Norbert Hoffmann
    Abstract:

    Traditionally, Organic Photochemistry when applied to synthesis strongly interacts with physical chemistry. The aim of this review is to illustrate this very fruitful interdisciplinary approach and cooperation. A profound understanding of the photochemical reactivity and reaction mechanisms is particularly helpful for optimization and application of these reactions. Some typical reactions and particular aspects are reported such as the Norrish-Type II reaction and the Yang cyclization and related transformations, the [2 + 2] photocycloadditions, particularly the Paterno–Buchi reaction, photochemical electron transfer induced transformations, different kinds of catalytic reactions such as photoredox catalysis for Organic synthesis and photooxygenation are discussed. Particular aspects such as the structure and reactivity of aryl cations, photochemical reactions in the crystalline state, chiral memory, different mechanisms of hydrogen transfer in photochemical reactions or fundamental aspects of stereoselectivity are discussed. Photochemical reactions are also investigated in the context of chemical engineering. Particularly, continuous flow reactors are of interest. Novel reactor systems are developed and modeling of photochemical transformations and different reactors play a key role in such studies. This research domain builds a bridge between fundamental studies of Organic photochemical reactions and their industrial application.

  • solar photochemical synthesis from the beginnings of Organic Photochemistry to the solar manufacturing of commodity chemicals
    Chemical Reviews, 2016
    Co-Authors: Michael Oelgemoller
    Abstract:

    Natural sunlight offers a cost-efficient and sustainable energy source for photochemical reactions. In contrast to the lengthy and small-scale “flask in the sun” procedures of the past, modern solar concentrator systems nowadays significantly shorten reaction times and enable technical-scale operations. After a brief historical introduction, this review presents the most important solar reactor types and their successful application in preparative solar syntheses. The examples demonstrate that solar manufacturing of fine chemicals is technically feasible and environmentally sustainable. After over 100 years, Ciamician's prophetic vision of “the Photochemistry of the future” as a clean and green manufacturing methodology has yet to be realized. At the same time, his warning “for nature is not in a hurry but mankind is” is still valid today. It is hoped that this review will lead to a renewed interest in this truly enlightening technology, that it will stimulate photochemists and photochemical engineers to ...

  • solar photochemical synthesis from the beginnings of Organic Photochemistry to the solar manufacturing of commodity chemicals
    Chemical Reviews, 2016
    Co-Authors: Michael Oelgemoller
    Abstract:

    Natural sunlight offers a cost-efficient and sustainable energy source for photochemical reactions. In contrast to the lengthy and small-scale "flask in the sun" procedures of the past, modern solar concentrator systems nowadays significantly shorten reaction times and enable technical-scale operations. After a brief historical introduction, this review presents the most important solar reactor types and their successful application in preparative solar syntheses. The examples demonstrate that solar manufacturing of fine chemicals is technically feasible and environmentally sustainable. After over 100 years, Ciamician's prophetic vision of "the Photochemistry of the future" as a clean and green manufacturing methodology has yet to be realized. At the same time, his warning "for nature is not in a hurry but mankind is" is still valid today. It is hoped that this review will lead to a renewed interest in this truly enlightening technology, that it will stimulate photochemists and photochemical engineers to "go back to the roots onto the roofs" and that it will ultimately result in industrial applications in the foreseeable future.

  • crc handbook of Organic Photochemistry and photobiology
    2012
    Co-Authors: Axel G Griesbeck, Michael Oelgemoller, Francesco Ghetti
    Abstract:

    With a new editorship of three highly respected scientists, the third edition of this bestselling handbook continues to provide an authoritative and unique resource for those working and studying in the areas of Photochemistry and photobiology. This edition uses the IUPAC glossary of terms for Photochemistry as a guide in the structure of the contents. Leading experts offer enlightening contributions on traditional topics, current trends, and future directions. New and updated topics in this edition include photosensoring, photoimmunology, artificial photosynthetic systems, phototoxicity of drugs, and much more.

Mario J Molina - One of the best experts on this subject based on the ideXlab platform.

  • secondary Organic aerosol formation from acetylene c 2 h 2 seed effect on soa yields due to Organic Photochemistry in the aerosol aqueous phase
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: R Volkamer, P Ziemann, Mario J Molina
    Abstract:

    Abstract. The lightest Non Methane HydroCarbon (NMHC), i.e., acetylene (C 2 H 2 ) is found to form secondary Organic aerosol (SOA). Contrary to current belief, the number of carbon atoms, n , for a NMHC to act as SOA precursor is lowered to n =2 here. The OH-radical initiated oxidation of C 2 H 2 forms glyoxal (CHOCHO) as the highest yield product, and >99% of the SOA from C 2 H 2 is attributed to CHOCHO. SOA formation from C 2 H 2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosols, mild acidification with sulphuric acid (SA, 3 Y SOA ) ranged from 1% to 24% and did not correlate with the Organic mass portion of the seed, but increased linearly with liquid water content (LWC) of the seed. For fixed LWC, Y SOA varied by more than a factor of five. Water soluble Organic carbon (WSOC) Photochemistry in the liquid water associated with internally mixed inOrganic/WSOC seed aerosols is found responsible for this seed effect. WSOC Photochemistry enhances the SOA source from CHOCHO, while seeds containing amino acids (AA) and/or SA showed among the lowest of all Y SOA values, and largely suppress the photochemical enhancement on the rate of CHOCHO uptake. Our results give first evidence for the importance of heterogeneous Photochemistry of CHOCHO in SOA formation, and identify a potential bias in the currently available Y SOA data for other SOA precursor NMHCs. We demonstrate that SOA formation via the aqueous phase is not limited to cloud droplets, but proceeds also in the absence of clouds, i.e., does not stop once a cloud droplet evaporates. Atmospheric models need to be expanded to include SOA formation from WSOC Photochemistry of CHOCHO, and possibly other α-dicarbonyls, in aqueous aerosols.

  • secondary Organic aerosol formation from acetylene c 2 h 2 seed effect on soa yields due to Organic Photochemistry in the aerosol aqueous phase
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: R Volkamer, P Ziemann, Mario J Molina
    Abstract:

    Abstract. The lightest Non Methane HydroCarbon (NMHC), i.e., acetylene (C2H2) is found to form secondary Organic aerosol (SOA). Contrary to current belief, the number of carbon atoms, n, for a NMHC to act as SOA precursor is lowered to n=2 here. The OH-radical initiated oxidation of C2H2 forms glyoxal (CHOCHO) as the highest yield product, and >99% of the SOA from C2H2 is attributed to CHOCHO. SOA formation from C2H2 and CHOCHO was studied in a photochemical and a dark simulation chamber. Further, the experimental conditions were varied with respect to the chemical composition of the seed aerosols, mild acidification with sulphuric acid (SA, 3

Robbie Radjagobalou - One of the best experts on this subject based on the ideXlab platform.

  • a revised 1d equivalent model for the determination of incident photon flux density in a continuous flow led driven spiral shaped microreactor using the actinometry method with reinecke s salt
    Journal of Flow Chemistry, 2021
    Co-Authors: Robbie Radjagobalou, Victoria Dias Da Silva Freitas, Jeanfrancois Blanco, Fabrice Gros, Jeremy Dauchet, Jeanfrancois Cornet, Karine Loubiere
    Abstract:

    Continuous-flow microstructured technologies are now recognized as promising alternatives to batch processing for Organic Photochemistry, especially when light emitting diodes (LEDs) are employed as light sources. To evaluate and optimize productivity and energetic efficiency, the knowledge of the incident photon flux density is crucial. In this context, the objectives of the present work are dual: first, to transfer the classical actinometry method with Reinecke’s salt to a continuous-flow LED-driven spiral-shaped reactor and second, to propose a revised one-dimensional equivalent model for the accurate determination of the incident photon flux density in this microreactor. Experimental measurements were carried out under controlled conditions. The effects of the spectral domain and radiant power emitted, the tubing length, the presence of gas-liquid Taylor flow, and the material of the support plate were especially investigated. An expression was established for the revised one-dimensional Cartesian model, taking into account the diffuse emission of the LED array and the reflection induced by the material of the plate in which the tubing was inserted (i.e. the reflection by the backside of the microreactor wall). In this way, the incident photon flux density could be estimated with an acceptable level of accuracy, which was not the case if the usual 1D model was applied (collimated emission and no reflection).