At the crossroad of photochemistry and radiation chemistry: formation of hydroxyl radicals in diluted aqueous solutions exposed to ultraviolet radiation

0508701 - ÚFP 2020 RIV GB eng J - Článek v odborném periodiku
Tomanová, K. - Přeček, M. - Můčka, V. - Vyšín, L. - Juha, Libor - Čuba, V.
At the crossroad of photochemistry and radiation chemistry: formation of hydroxyl radicals in diluted aqueous solutions exposed to ultraviolet radiation.
Physical Chemistry Chemical Physics. Roč. 19, č. 43 (2017), s. 29402-29408. ISSN 1463-9076. E-ISSN 1463-9084
Institucionální podpora: RVO:61389021
Klíčová slova: coumarin-3-carboxylic acid * photolysis * phospholipids * fluorescence * mechanism * lipids * yield * uv
Obor OECD: Physical chemistry
Impakt faktor: 3.906, rok: 2017
Způsob publikování: Omezený přístup
https://pubs.rsc.org/en/content/articlelanding/2017/CP/C7CP05125E#!divAbstract

Formation yields of center dot OH radicals were precisely determined in aqueous solutions of coumarin-3-carboxylic acid and ferrous sulfate (i.e., Fricke dosimeter) exposed to 253.7 nm radiation delivered from a continuous source. Quantum yield of center dot OH radicals was determined as similar to 0.08, i.e., roughly one out of twelve photons, efficiently absorbed in UV-illuminated solutions, produced one center dot OH radical. Energetically, a water molecule should undergo a correlated action of at least two 4.9 eV photons delivering enough energy for direct H-OH dissociation (5.0-5.4 eV). We suggest a mechanism based on an interaction of two water molecules, both in long-living triplet states. An intermolecular transfer of excitation energy provided a sufficient amount of energy for the dissociation of one water molecule into center dot OH and H center dot radicals. In an aqueous solution of phospholipids, quantum yields of hydroperoxides formed under these irradiation conditions decreased with total effectively absorbed energy (i.e. a dose), similar to the radiation chemical yields obtained during an exposure to ionizing radiation, such as gamma rays from radionuclide sources. Under 253.7 nm irradiation, one center dot OH radical causes a peroxidation of 34 phospholipid molecules. This implicates chain mechanism of the reaction.
Trvalý link: http://hdl.handle.net/11104/0299536