scholarly journals Reactivity control of a photocatalytic system by changing the light intensity

2019 ◽  
Vol 10 (48) ◽  
pp. 11023-11029 ◽  
Author(s):  
Christoph Kerzig ◽  
Oliver S. Wenger
Keyword(s):  
Light Intensity ◽  
Reaction Mechanisms ◽  
Photochemical Reactions ◽  
Two Photon ◽  
Photocatalytic System

By using simple optics such as a lens, switching between one- and two-photon driven reaction mechanisms became feasible, which allows the control over the main products of photochemical reactions.

A renewable photocatalytic system with dramatic photocatalytic activity for H2 evolution and constant light energy utilization: Eosin Y sensitized ZnWO4 nanoplates loaded with CuO nanoparticles

2021 ◽  
Author(s):  
Xiaoluo Bao ◽  
Xiaokun Wang ◽  
Xiangqing Li ◽  
Lixia Qin ◽  
Taiyang Zhang ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Light Intensity ◽  
Incident Light ◽  
Cuo Nanoparticles ◽  
Energy Utilization ◽  
Limited Attention ◽  
Eosin Y ◽  
H2 Evolution ◽  
Incident Light Intensity ◽  
Photocatalytic System

It is necessary for the commercialization of sunlight-driven H2 evolution to develop an efficient photocatalytic system whose energy utilization is independent on incident light intensity. Unfortunately, limited attention has been...

scholarly journals Photochemical reactions of methyl and ethyl nitrate: a dual role for alkyl nitrates in the nitrogen cycle

2011 ◽  
Vol 8 (6) ◽  
pp. 529 ◽  
Author(s):  
Shuzhong He ◽  
Zhongming Chen ◽  
Xuan Zhang
Keyword(s):  
Air Quality ◽  
Nitrogen Cycle ◽  
Laboratory Study ◽  
Reaction Mechanisms ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
Reactive Nitrogen ◽  
Alkyl Nitrates ◽  
Nitrogen Exchange ◽  
High Yields

Environmental contextAlkyl nitrates are considered to be important intermediates in the atmospheric hydrocarbons–nitrogen oxides–ozone cycle, which significantly determines air quality and nitrogen exchange between the atmosphere and the Earth’s surfaces. The present laboratory study investigates reaction products of alkyl nitrates to elucidate their photochemical reaction mechanisms in the atmosphere. The results provide a better understanding of the role played by alkyl nitrates in the atmospheric environment. AbstractAlkyl nitrates (ANs) are important nitrogen-containing organic compounds and are usually considered to be temporary reservoirs of reactive nitrogen NOx (NO2 and NO) in the atmosphere, although their atmospheric fates are incompletely understood. Here a laboratory study of the gas-phase photolysis and OH-initiated reactions of methyl nitrate (CH3ONO2) and ethyl nitrate (C2H5ONO2), as models of atmospheric ANs, is reported with a focus on elucidating the detailed photochemical reaction mechanisms of ANs in the atmosphere. A series of intermediate and end products were well characterised for the first time from the photochemical reactions of methyl and ethyl nitrate conducted under simulated atmospheric conditions. Notably, for both the photolysis and OH-initiated reactions of CH3ONO2 and C2H5ONO2, unexpectedly high yields of HNO3 (photochemically non-reactive nitrogen) were found and also unexpectedly high yields of peroxyacyl nitrates (RC(O)OONO2, where R = H, CH3, CH3CH2,…) (reactive nitrogen) have been found as CH3C(O)OONO2 in the C2H5ONO2 reaction or proposed as HC(O)OONO2 in the CH3ONO2 reaction. Although the yields of HNO3 from the ANs under ambient conditions are likely variable and different from those obtained in the laboratory experiments reported here, the results imply that the ANs could potentially serve as a sink for reactive nitrogen in the atmosphere. The potential for this dual role of organic nitrates in the nitrogen cycle should be considered in the study of air quality and nitrogen exchange between the atmosphere and surface. Finally, an attempt was made to estimate the production of HNO3 and peroxyacyl nitrates derived from NOx by ANs as intermediates in the atmosphere.

Application of two-photon chromophore excitation to laser scanning microscopy

1991 ◽  
Vol 49 ◽  
pp. 404-405
Author(s):  
David W. Piston ◽  
James H. Strickler ◽  
Watt W. Webb
Keyword(s):  
Laser Scanning ◽  
Uv Light ◽  
Excited Electronic State ◽  
Laser Scanning Confocal Microscopy ◽  
Photochemical Reactions ◽  
Laser Scanning Microscopy ◽  
Scanning Confocal Microscopy ◽  
Two Photon ◽  
Photon Excitation ◽  
Two Photon Excitation

The non-linear optical technique of two-photon excitation of fluorescence and photochemical reactions makes possible new applications that are not possible using linear one-photon excitation in laser scanning confocal microscopy. The two-photon excitation effect arises from the simultaneous absorption of two red photons, which causes the transition to an excited electronic state with its normal absorption in the ultraviolet. In our fluorescence experiments, this excited state is the same singlet state, S1, that is populated during a conventional fluorescence experiment, and thus exhibits the same emission properties (e.g. wavelength shifts, environmental sensitivity) that are observed in typical biological microscopy studies. Likewise, photochemical reactions such as light induced polymerization and photolytic uncaging that are normally catalyzed by UV light can be generated using two-photon excitation. In practice, twophoton excitation is made possible by the very high local instantaneous intensity that is provided by a combination of the diffraction limited focusing in the microscope and the temporal concentration of a subpicosecond mode-locked laser.

Photoisomerization transition state manipulation by entangled two-photon absorption

2021 ◽  
Vol 118 (47) ◽  
pp. e2116868118
Author(s):  
Bing Gu ◽  
Daniel Keefer ◽  
Flavia Aleotti ◽  
Artur Nenov ◽  
Marco Garavelli ◽  
...  
Keyword(s):  
Wave Packet ◽  
Transition State ◽  
Product Yield ◽  
Photochemical Reactions ◽  
Photon Absorption ◽  
Conical Intersection ◽  
Two Photon ◽  
Wave Packet Dynamics ◽  
Photon Excitation ◽  
Two Photon Excitation

We demonstrate how two-photon excitation with quantum light can influence elementary photochemical events. The azobenzene trans → cis isomerization following entangled two-photon excitation is simulated using quantum nuclear wave packet dynamics. Photon entanglement modulates the nuclear wave packets by coherently controlling the transition pathways. The photochemical transition state during passage of the reactive conical intersection in azobenzene photoisomerization is strongly affected with a noticeable alteration of the product yield. Quantum entanglement thus provides a novel control knob for photochemical reactions. The distribution of the vibronic coherences during the conical intersection passage strongly depends on the shape of the initial wave packet created upon quantum light excitation. X-ray signals that can experimentally monitor this coherence are simulated.

A time-resolved EPR study of one- and two-photon processes in the photochemical reactions of benzil

1989 ◽  
Vol 93 (11) ◽  
pp. 4411-4413 ◽  
Author(s):  
Masahiro Mukai ◽  
Seigo Yamauchi ◽  
Noboru Hirota
Keyword(s):  
Photochemical Reactions ◽  
Time Resolved ◽  
Two Photon

scholarly journals A 3D-Printed Open Access Photoreactor Designed for Versatile Applications in Photoredox- & Photoelectrochemical Synthesis

2020 ◽  
Author(s):  
Florian Schiel ◽  
Christoph Peinsipp ◽  
Stefan Kornigg ◽  
Dietrich Böse
Keyword(s):  
Light Intensity ◽  
Large Scale ◽  
High Light Intensity ◽  
Photochemical Reactions ◽  
Catalyst Loading ◽  
Fast Reaction ◽  
Thermoelectric Coolers ◽  
Practical Design ◽  
3D Printed ◽  
Reaction Vessels

Most published photochemical reactions are still not performed under standardized conditions. It is well known that the control of light intensity, the exact reaction temperature and other parameters are crucial for the success of a photochemical reaction. However, for most reactions reported in the literature, these parameters are not precisely controlled and recorded. As a result, the reproduction of these reactions is difficult and the progress in the field of photoredox chemistry is hampered by this limitation. To address this problem, a 3D-printed photoreactor was designed which can be easily replicated with a small number of inexpensive and easily available components. Equipped with thermoelectric coolers, the reactor can access and precisely control the temperature in the range of -17 °C to 80 °C, while reactions under high-intensity irradiation are performed with LED lamps from Kessil or HepatoChem. The practical design of the vial holder allows a versatile use of different reaction vessels - in addition to fast reaction opMost published photochemical reactions are still not performed under standardized conditions. It is well known that the control of light intensity, the exact reaction temperature and other parameters are crucial for the success of a photochemical reaction. However, for most reactions reported in the literature, these parameters are not precisely controlled and recorded. As a result, the reproduction of these reactions is difficult and the progress in the field of photoredox chemistry is hampered by this limitation. To address this problem, a 3D-printed photoreactor was designed which can be easily replicated with a small number of inexpensive and easily available components. Equipped with thermoelectric coolers, the reactor can access and precisely control the temperature in the range of -17 °C to 80 °C, while reactions under high-intensity irradiation are performed with LED lamps from Kessil or HepatoChem. The practical design of the vial holder allows a versatile use of different reaction vessels - in addition to fast reaction optimization with up to eight vials simultaneously, upscaling in batch and flow is easily possible. Due to the high light intensity, the catalyst loading can be reduced to 0.1 mol% for large-scale reactions. The flexibility of the vial holder is demonstrated by combining IKA’s ElectraSyn 2.0 with the photoreactor to perform photoelectrochemical reactions in a reproducible manner.timization with up to eight vials simultaneously, upscaling in batch and flow is easily possible. Due to the high light intensity, the catalyst loading can be reduced to 0.1 mol% for large-scale reactions. The flexibility of the vial holder is demonstrated by combining IKA’s ElectraSyn 2.0 with the photoreactor to perform photoelectrochemical reactions in a reproducible manner.

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