Photooxidation of organic and inorganic substrates during UV photolysis of nitrite anion in aqueous solution

Bilski, Piotr; Chignell, Colin F.; Szychlinski, J.; Borkowski, Andrzej; Oleksy, E.; Reszka, Krzysztof J.

doi:10.1021/ja00028a023

Cited by 73 publications

(68 citation statements)

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“…4, 9, 10) represents a highly reactive nitrogen species (31). 2 NO  radical was detected previously at room temperature by the EPR spin trapping in strong alkaline media using the nitromethane aci anion ( -22 CH =NO ) (18,21). The corresponding spin-adduct, dinitromethyl radical dianion ( --22 O N-CH=NO  ) is characterized by the spin Hamiltonian parameters corresponding to the interaction of an unpaired electron with two equivalent nitrogen nuclei and one hydrogen nucleus (a N (2N) = 0.960 mT, a H = 0.420 mT; g = 2.0055) (18,21).…”

Section: Resultsmentioning

confidence: 99%

“…2 NO  radical was detected previously at room temperature by the EPR spin trapping in strong alkaline media using the nitromethane aci anion ( -22 CH =NO ) (18,21). The corresponding spin-adduct, dinitromethyl radical dianion ( --22 O N-CH=NO  ) is characterized by the spin Hamiltonian parameters corresponding to the interaction of an unpaired electron with two equivalent nitrogen nuclei and one hydrogen nucleus (a N (2N) = 0.960 mT, a H = 0.420 mT; g = 2.0055) (18,21). The concentration of dinitromethyl radical dianion monitored upon UV irradiation of nitrite in alkaline solutions (pH in the range 12.9-13.9) containing NM was proportional to the nitrite concentration, consequently the quantitative EPR spin trapping method was suggested previously for the determination of 2 NO  and -2 NO from energetic materials (21).…”

Section: Resultsmentioning

confidence: 99%

“…The aerated aqueous nitrite solutions and TiO 2 suspensions represent systems producing reactive radical species upon UVA-photoactivation, consequently the EPR spin trapping technique using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap was successfully applied to monitor the photoinduced  OH generation in both systems (17)(18)(19)(20). Additionally, the formation of nitrogen dioxide radical during nitrite UVA photolysis ( = 360 nm) was monitored in alkaline media (pH > 12) using another spin trapping agent nitromethane (NM) (18,21).…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, the formation of nitrogen dioxide radical during nitrite UVA photolysis ( = 360 nm) was monitored in alkaline media (pH > 12) using another spin trapping agent nitromethane (NM) (18,21).…”

Section: Introductionmentioning

confidence: 99%

“…Despite a number of EPR spin trapping studies on the formation of reactive paramagnetic intermediates upon UVA-photoactivation of nitrite in the aerated aqueous solutions (18,21), analogous experiments in the irradiated TiO 2 suspensions are missing in the literature. Our EPR investigations are oriented on the application of different spin trapping agents to monitor the effect of nitrite on the spin-adduct formation, and on the photocatalytic reduction of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) cation radical (ABTS + ) in the aqueous titania suspensions.…”

Section: Introductionmentioning

confidence: 99%

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UVA-Induced Processes in the Aqueous Titanium Dioxide Suspensions Containing Nitrite (An EPR Spin Trapping Study)

Brezová

Barbieriková

Dvoranová

et al. 2016

Journal of Advanced Oxidation Technologies

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Abstract:Application of TiO 2 photocatalytic systems for water purification and remediation is based on the generation of short-lived reactive oxygen species able to destroy a variety of contaminants, upon the ultra-bandgap irradiation of TiO 2 particles in the aerated aqueous media. However the recently more profound presence of inorganic nitrogen compounds can affect these processes due to the complex photochemical behavior of the nitrite and nitrate in aqueous solutions. The effect of the nitrite present in the titanium dioxide suspensions was monitored via the reactive radical intermediates detected by EPR spin trapping technique. Various spin trapping agents were applied to follow the changes in the behavior of the system caused by the nitrite upon UVA irradiation and the limits of the spin trapping technique itself were also considered. The competition reaction of the photogenerated holes and hydroxyl radicals with the nitrite was revealed as the dominant process occurring in the studied systems.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

UVA-Induced Processes in the Aqueous Titanium Dioxide Suspensions Containing Nitrite (An EPR Spin Trapping Study)

Brezová

Barbieriková

Dvoranová

et al. 2016

Journal of Advanced Oxidation Technologies

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Thermally initiated radical reactions of K2S2O8: EPR spin trapping investigations

et al. 2000

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The thermally initiated decomposition of K2S2O8 radical initiator coupled with EPR spin trapping represents a very powerful source of reactive free radicals which can be effectively used to initiate and to monitor various radical processes, as we were able to demonstrate in the characterization of the antioxidant properties of wine samples. The spin trapping agent α‐phenyl‐N‐tert‐butylnitrone (PBN) is a very effective trap, but with low selectivity. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide (DMPO), which has higher selectivity and a very pronounced dependence of adduct formation on the temperature (the formal activation energy of ·DMPO–OH formation is 81.1 kJ mol−1), offers more advantages. In pure aqueous solutions, formation of the ·DMPO–OH adduct dominates. In mixed water–ethanol solvents, carbon‐centred DMPO radical adducts are increasingly evident with higher CH3CH2OH ratios, and at very high ethanol ratios the formation of ·DMPO–OOR adduct prevails. Copyright © 2000 John Wiley & Sons, Ltd.

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Fragmentation of Fluorinated Model Compounds Exposed to Oxygen Radicals: Spin Trapping ESR Experiments and Implications for the Behaviour of Proton Exchange Membranes Used in Fuel Cells

2008

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Low-molecular weight model compounds (MCs) for Nafion membranes used in fuel cells were exposed at 300 K to Á OH radicals produced by UV irradiation of aqueous H 2 O 2 solutions. The MCs contained fluorinated and partially fluorinated groups terminated by sulphonic or carboxylic acid groups. The fragmentation process in the MCs was studied by spin trapping electron spin resonance (ESR) methods, using 5,5-dimethylpyrroline-N-oxide (DMPO), N-tert-butyla-phenylnitrone (PBN) and 2-methyl-2-nitrosopropane (MNP) as the spin traps. The objective of these experiments was to assess the effect of the type of ionic groups (sulphonic or carboxylic) and of fluorine substitution on the spin adducts detected. DMPO experiments led to the detection of spin adducts of Á OH and of carbon-centred radicals (CCRs), and allowed the determination of the Á OH attack site on the ionic and/or on the protiated or fluorinated groups. CCR adducts were also detected when using PBN as a spin trap; a key point in the interpretation of the PBN results was, however, the realisation that MNP is formed during PBN exposure to UV irradiation and oxygen or other oxidants such as H 2 O 2 . Experiments with MNP as the spin trap were the most informative in terms of structural details for adducts obtained from each MC. The results allowed the identification of CCRs present as adducts, based on large hyperfine splittings (hfs) from, and the number of, interacting 19 F nuclei; in addition, oxygen-centred radicals (OCRs) as MNP adducts were also identified, with much lower hfs from 19 F nuclei. Taken together, the results deduced by spin trapping suggest that both sulphonic acid and acetic acid groups can be attacked by Á OH radicals and confirm two possible degradation mechanisms in Nafion membranes: initiated at the backbone and at the side chain.

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Photooxidation of organic and inorganic substrates during UV photolysis of nitrite anion in aqueous solution

Cited by 73 publications

References 1 publication

UVA-Induced Processes in the Aqueous Titanium Dioxide Suspensions Containing Nitrite (An EPR Spin Trapping Study)

UVA-Induced Processes in the Aqueous Titanium Dioxide Suspensions Containing Nitrite (An EPR Spin Trapping Study)

Thermally initiated radical reactions of K2S2O8: EPR spin trapping investigations

Fragmentation of Fluorinated Model Compounds Exposed to Oxygen Radicals: Spin Trapping ESR Experiments and Implications for the Behaviour of Proton Exchange Membranes Used in Fuel Cells

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