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

2017 ◽  
Vol 19 (43) ◽  
pp. 29402-29408 ◽  
Author(s):  
Kateřina Tomanová ◽  
Martin Precek ◽  
Viliam Múčka ◽  
Luděk Vyšín ◽  
Libor Juha ◽  
...  
Keyword(s):  
Ultraviolet Radiation ◽  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Radiation Chemistry ◽  
Quantum Yields ◽  
Oh Radicals

We provide evidence on the formation of ˙OH radicals via 253.7 nm photolysis of aqueous solutions, determine their quantum yields, and apply the knowledge to photo-induced formation of phospholipid hydroperoxides.

scholarly journals EPR study of the production of oh radicals in aqueous solutions of uranium irradiated by ultraviolet light

2009 ◽  
Vol 74 (6) ◽  
pp. 651-661 ◽  
Author(s):  
Marko Dakovic ◽  
Milos Mojovic ◽  
Goran Bacic
Keyword(s):  
Aqueous Solutions ◽  
Hydroxyl Radicals ◽  
Fluorescence Decay ◽  
Uranyl Acetate ◽  
Oh Radicals ◽  
Solution Ph ◽  
Trapping Method ◽  
Wide Ph Range ◽  
Ph Range ◽  
Epr Spin Trapping

The aim of the study was to establish whether hydroxyl radicals (?OH) were produced in UV-irradiated aqueous solutions of uranyl salts. The production of ?OH was studied in uranyl acetate and nitrate solutions by an EPR spin trap method over a wide pH range, with variation of the uranium concentrations. The production of ?OH in uranyl solutions irradiated with UV was unequivocally demonstrated for the first time using the EPR spin-trapping method. The production of ?OH can be connected to speciation of uranium species in aqueous solutions, showing a complex dependence on the solution pH. When compared with the results of radiative de-excitation of excited uranyl (+22*UO ) by the quenching of its fluorescence, the present results indicate that the generation of hydroxyl radicals plays a major role in the fluorescence decay of + 22 *UO . The role of the presence of carbonates and counter ions pertinent to environmental conditions in biological systems on the production of hydroxyl radicals was also assessed in an attempt to reveal the mechanism of +22*UO de-excitation. Various mechanisms, including ?OH production, are inferred but the main point is that the generation of ?OH in uranium containing solutions must be considered when assessing uranium toxicity.

The radiation chemistry of aqueous solutions - I. The effect of changing linear energy transfer along a polonium α -particle track

1962 ◽  
Vol 265 (1323) ◽  
pp. 407-421 ◽  
Keyword(s):  
Aqueous Solutions ◽  
Sulphuric Acid ◽  
Hydroxyl Radicals ◽  
Chemical Change ◽  
Radiation Chemistry ◽  
Track Length ◽  
Particle Track ◽  
Ferrous Ions ◽  
Ceric Sulphate ◽  
Local Value

Absolute G values for chemical change when various aqueous solutions are irradiated with α -particles from an external polonium source have been determined for different fractions ( x ) of the α -particle track spent within the solution. G(Fe 3+ ) for an aerated solution containing 1 mM ferrous ions and 0.1N sulphuric acid decreases from 5.0 at x =0.02 through a minimum value 3.65 at 0.11 x 0.01 and then increases to 5.94 at x = 0.525. The local value G(Fe 3+ ), defined as G(Fe 3+ ) for an element of track length a distance x R from the end of the track, where R is the range of the whole track in water, shows a similar but more pronounced dependence on x which is strongly reminiscent of the inverted Bragg curve for l. e. t. plotted against x in this medium, having a minimum of 3.2 5 ± 0.1 5 at x= 0.085±0.015. As x is increased G(Ce 3+ ) for an aerated 200 μM solution of ceric sulphate in 0.1 N sulphuric acid shows no minimum but increases from 1.0 at x =0.04 to 3.0 at x=0.25 and 4. 05 at x = 0.525. Thallous ions have no effect on G(Ce 3+ ) for x ≤ 0.45. G(H 2 O 2 ) for aerated water was found to be 1.22 ±0.06. It is concluded that very few hydroxyl radicals are available and that the intra-track reactions between H 2 O 2 and H as well as OH are very important and vary in extent as x is varied.

scholarly journals Hydroxyl-radical scavenging activity of hydrogen does not significantly contribute to its biological function

2021 ◽  
Author(s):  
Qinjian Li ◽  
Fei Xie ◽  
Yang Yi ◽  
Pengxiang Zhao ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Hydroxyl Radicals ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Published Data ◽  
Oh Radicals ◽  
Dependent Manner ◽  
Protective Effects ◽  
Beneficial Effects ◽  
Wide Range ◽  
Depth Study

AbstractSince Ohsawa et al. reported a biological antioxidant function of hydrogen in 2007, researchers have now shown it to exert protective effects in a wide range of human and animal disease models. Clinical observations and scientific arguments suggest that a selective scavenging property of H2 cannot adequately explain the beneficial effects of hydrogen. However, there is no experiment challenging the original published data, which suggested that molecular hydrogen dissolved in solution reacts with hydroxyl radicals in cell-free systems. Here we report that a hydrogen-saturated solution (0.6 mM) did not significantly reduce hydroxyl radicals in the Fenton system using 1 mM H2O2. We replicated the same condition as Ohsawa’s study (i.e. 5 μM H2O2), and observed a decrease in •OH radicals in both the H2-rich and N2-rich solutions, which may be caused by a decreased dissolved oxygen concentration. Finally, we determined the effect of hydrogen on a high-valence iron enzyme, horseradish peroxidase (HRP), and found that hydrogen could directly increase HRP activity in a dose-dependent manner. Overall, these results indicate that although H2 and •OH can react, the reaction rate is too low to have physiological function. The target of hydrogen is more complex, and its interaction with enzymes or other macro-molecules deserve more attention and in-depth study.

scholarly journals Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: Uptake kinetics and condensed-phase products

2007 ◽  
Vol 7 (3) ◽  
pp. 6803-6842 ◽  
Author(s):  
I. J. George ◽  
A. Vlasenko ◽  
J. G. Slowik ◽  
J. P. D. Abbatt
Keyword(s):  
Hydroxyl Radicals ◽  
Particle Density ◽  
Organic Aerosols ◽  
Oxidation Products ◽  
Photochemical Oxidation ◽  
Mass Spectrometry Analysis ◽  
Oh Radicals ◽  
Ionization Mass ◽  
Phase Reaction ◽  
Heterogeneous Oxidation

Abstract. The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gas-phase OH radicals were investigated under NOx-free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl) sebacate (BES) particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ0 = 1.26 (±0.04), confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

scholarly journals Potential of Iron Pillared Clay as Active Nanocatalyst for Rapid Decolorization of Methylene Blue

2019 ◽  
Vol 7 (2) ◽  
pp. 46-53
Author(s):  
Lal hmunsiama ◽  
◽  
Seung-Mok Lee ◽  
Keyword(s):  
Methylene Blue ◽  
Iron Oxide ◽  
Aqueous Solutions ◽  
Low Cost ◽  
Analytical Data ◽  
Bentonite Clay ◽  
Pillared Clay ◽  
Oh Radicals ◽  
Heterogeneous Structure ◽  
Iron Oxide Particles

In this study, the iron-pillared clay nanocatalyst (ICN) was employed as a nanocatalyst for decolorization of methylene blue (MB) in aqueous solutions without hydrogen peroxide. The changes in clay structure after the incorporation of iron-oxide particles was studied with the help of XRD analytical data. The SEM micrographs showed higher heterogeneous structure of ICN compared to pristine clay and the specific surface area of ICN (82.54 m2/g) is considerably higher than the unmodified clay (63.41 m2/g). Further, the EDX analytical data indicate the successful incorporation of iron-oxide into bentonite clay. Batch experiments showed that ICN could degrade MB within pH 3.0 to 11.0 and it is efficient even at higher concentrations. The degradation is very fast and more than 90% is removed within 30 mins. A small amount of ICN is effective for degradation of MB and the reusability test showed that ICN can be reuse for several times for the degradation of MB in aqueous solutions. The effect of scavengers studies indicate that the ·OH radicals generated from the ICN are responsible in the degradation of MB. This study indicates that ICN must be low cost and environmentally friendly active nanocatalyst for degradation of MB present in aquatic environment.

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