Photochemical Decomposition Of Hydrogen Peroxide Research Articles

Reactive Oxygen Species in Emulated Martian Conditions and Their Effect on the Viability of the Unicellular Alga Scenedesmus dimorphus.

Formation of oxygen-based free radicals from photochemical decomposition of hydrogen peroxide (H2O2) on Mars may be a key factor in the potential survival of terrestrial-like organisms on the red planet. Martian conditions that generate reactive oxygen species involve the decomposition of H2O2 at temperatures of around 278 K under relatively high doses of C-band ultraviolet radiation (UVC). This process is further amplified by the presence of iron oxides and perchlorates. Photosynthetic organisms exhibit a number of evolutionary traits that allow them to withstand both oxidative stress and UVC radiation. Here, we examine the effect of free radicals produced by the decomposition of H2O2 under emulated martian conditions on the viability of Scenedesmus dimorphus, a unicellular alga that is resistant to UVC radiation and varying levels of perchlorate and H2O2, both of which are present on Mars. Identification and quantification of free radicals formed under these conditions were performed with Electron Paramagnetic Resonance spectroscopy. These results were correlated with the viability of S. dimorphus, and the formation of oxygen-based free radicals and survival of the alga were found to be strongly dependent on the amount of H2O2 available. For H2O2 amounts close to those present in the rarefied martian environment, the products of these catalytic reactions did not have a significant effect on the algal population growth curve.

Catalytic Properties of Cadmium Sulfide Nanoparticles Obtained via Precipitation from Solutions

The catalytic properties of cadmium sulfide nanoparticles in the photochemical decomposition of hydrogen peroxide are studied. It is shown that in aqueous H2O2 solutions of any concentration, cadmium sulfide accelerates the reaction and does not change its order. The quantum yield of the reaction is 1 and does not depend on the concentration of hydrogen peroxide. The scattering of light by particles and an increase in their concentration reduces the quantum yield.

Hydrogen peroxide in artificial photosynthesizing systems

From the point of view of the concepts of hydrogen peroxide as a source of photosynthetic oxygen (hydrogen) coordination and photochemical properties of chlorophyll and its aggregates towards hydrogen peroxide were considered. The binding energy of H2O and H2O2 with chlorophyll and chlorophyllide depending on their form (monomers, dimers and trimers) was estimated by quantum chemical calculations. It is shown that at an increase of the degree of the pigment aggregation binding energy of H2O2 was more than the energy of H2O. Analysis of experimental results of the photochemical decomposition of hydrogen peroxide using chlorophyll was carried out. Estimates of the thermodynamic parameters (deltaG degrees and deltaH degrees) of the formation of organic compounds from CO2 with water and hydrogen peroxide were compared. The interaction of CO2 with H2O2 requires much less energy consumption than with water for all considered cases. The formation of organic products (formaldehyde, alcohols, carboxylic and carbonylic compounds) and simultaneous production of O2 under the influence of visible light in the systems of inorganic carbon--hydrogen peroxide--chlorophyll (phthalocyanine) is detected by GC/MS method, FTIR spectroscopy, and chemical analysis.

Antioxidant and radical-scavenging activities of Slovak honeys – An electron paramagnetic resonance study

The antioxidant properties of 15 honey samples from different floral sources and various Slovak regions were investigated by means of electron paramagnetic resonance spectroscopy. Cation radical of ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt), DPPH (1,1-diphenyl-2-picrylhydrazyl) and hydroxyl radicals generated by the photochemical decomposition of hydrogen peroxide were used as oxidants. The antioxidant activities found with ABTS+, expressed as trolox equivalent antioxidant capacity (TEAC), ranged from 0.15 to 1.14mmolkg−1, and those determined with DPPH, from 0.04 to 0.32mmolkg−1. TEAC values correlated well with results found by elimination of DPPH, and both values revealed a linear relationship with the concentration of phenolics obtained with the Folin–Ciocalteu phenol test (expressed as gallic acid equivalents, GAE). The colour coordinates (CIE L∗a∗b∗), as well as reflectance spectra determined for original honeys using a white background, demonstrated that the colour difference (ΔE∗) and coordinate b∗ interrelate with TEAC values. The radical-scavenging capacities (RSC) of the honey samples determined in the experiments with photochemically decomposed hydrogen peroxide, generating reactive OH radicals in the presence of spin trapping agent, differ from those found with ABTS+ and DPPH. Here, probably, the reactive OH radicals, having higher redox potential, are scavenged by a variety of compounds not effective with ABTS+ and DPPH (e.g., saccharides, proteins).

Photochemical decomposition of hydrogen peroxide (H2O2) and formaldehyde (HCHO) in artificial snow

AbstractLaboratory-made snow doped with either hydrogen peroxide (H2O2) or formaldehyde (HCHO) was exposed to radiation in the ultraviolet and visible range, resulting in a decomposition of both compounds. These experiments demonstrate that, besides the photolysis of nitrate, further photochemical reactions of atmospheric relevant compounds can take place in snow. Under similar conditions the decomposition of H2O2 is more efficient than that of HCHO. Since the decompositions in the experiments follow first-order reaction kinetics, we suggest that the same products as in photolysis reactions in the liquid phase are produced. If similar reactions also take place in natural snow covers, these reactions would have several important consequences. The reactions could represent pathways for the generation of highly reactive radicals in the condensed phase, enhancing the photochemical activity of surface snow and modifying the oxidation capacity of the atmospheric boundary layer. The photolysis could also constitute an additional sink for H2O2 and HCHO in surface snow, which should be taken into account for the reconstruction of atmospheric concentrations of both compounds from concentration profiles in surface snow and ice cores.

Photochemical bleaching of chemical pulps catalyzed by titanium dioxide

A two-stage process for photochemical bleaching of cellulosic pulps is presented. The first, based on the generation of oxygen active species by the photocatalytic action of TiO 2, and the second on the photochemical decomposition of hydrogen peroxide. Both stages are carried out under alkaline pH and at 85°C in aqueous suspension at a consistency of 5%. The experiments were performed on kraft ( Eucalyptus grandis, Pinus pinaster and Picea mariana), acesolv ( E. grandis) and peroxyformic acid ( E. grandis) pulps. The presence of TiO 2 as photocatalyst showed several advantages, such as reduction of reaction time, preservation of the pulp viscosity, increase of the selectivity during the photobleaching and decrease of the consumption of the bleaching chemicals. UV/Vis and FTIR spectroscopies indicate a decrease of the coniferaldehyde structures during the TiO 2 photocatalyzed stage, whereas quinones entities were found to remain in the residual lignin even after the final hydrogen peroxide stage. TiO 2-photocatalyzed sequence was found to degrade more efficiently the chromophores, especially carbonyl groups, than the sequence carried out in its absence.

The photochemical decomposition of hydrogen peroxide in surface waters of the eastern Caribbean and Orinoco River

The photochemical decomposition of hydrogen peroxide has been studied in surface waters collected on a transect from the Atlantic Ocean north of Puerto Rico through the eastern Caribbean Sea to the mouth of the Orinoco River. Absolute rates of photochemical decomposition were measured by adding 18O labelled H2O2 to the water samples and irradiating with a shipboard solar simulator. Photochemical decomposition was measurable at all station locations. Decomposition rates increased along the transect towards the Orinoco and were directly proportional to photochemical production rates, which also increased. Photodecomposition rates were also linearly related to the intensity of absorption of samples at 300 nm. Decomposition rates were generally ∼5% of formation rates, indicating that photochemical decomposition is probably a minor sink for H2O2 in the mixed layer compared to biological decomposition. In all seawater samples, photodecomposition led exclusively to 18O2, indicating that reaction with photochemically produced oxidants was the dominant reaction mechanism. The oxidizing species are not the best known photooxidants in seawater, singlet oxygen and OH and O2 radicals. Unidentified oxidants with formation rates ∼5% of the H2O2 formation flux are required. In contrast, H218O2 decomposition in unfiltered samples of Orinoco River water led solely to H218O2, indicating reaction with a photochemically produced reductant was the dominant mechanism. Further experiments indicated that the reductant was probably Fe(II) produced by photoreduction of particulate Fe(III), a known process. This pathway would produce an equivalent flux of OH radical: Fe(II) + HOOH → Fe(III) + OH + OH−.

Hydrogen peroxide photolysis. Mechanism of photocatalytic effect of transition metals

The photochemical decomposition of hydrogen peroxide depends on the presence of transition metal ions in the reaction system. Photochemical reduction of the poorly catalytically active ions with higher oxidation states produces catalytically active ions of lower oxidation states which catalyze the thermal reaction. The quantum yield of hydrogen peroxide photolysis is proportional to the number of catalytic cycles occurring on the photochemically generated catalyst.

Ozone and Ozonide Production and Stabilization in Water

Evidence is presented showing that ozone and ozonide are produced by the photochemical decomposition of hydrogen peroxide and sodium persulfate in water made alkaline with sodium hydroxide. Their yields and lifetimes are increased by increase in base and molecular oxygen, the increase with base being much greater in the case of ozone. Consideration is given to the reaction mechanism.

The Photochemical Decomposition of Hydrogen Peroxide in Aqueous Solutions of Allyl Alcohol at 2537 Å.1

The Photochemical Decomposition of Hydrogen Peroxide in Aqueous Solutions of Allyl Alcohol at 2537 Å.¹

The Photochemical Decomposition of Hydrogen Peroxide. Quantum Yields, Tracer and Fractionation Effects

The Photochemical Decomposition of Hydrogen Peroxide. Quantum Yields, Tracer and Fractionation Effects

The Absorption Spectrum and the Dissociation of H2O2

Although Holt, McLane, and Oldenberg state that they were unable to observe a sharp cut in the absorption spectrum of hydrogen peroxide vapor, it is shown that their measurements indicate a rather abrupt increase of the absorption coefficient at 1920A. It is doubtful that the dissociation energy of hydrogen peroxide can be derived from its absorption spectrum. However, it seems possible that the photo-chemical decomposition of hydrogen peroxide gives an upper limit for its dissociation energy. Our measurements of the absorption coefficient of hydrogen peroxide agree well with the results of Holt, McLane, and Oldenberg.

Photochemical Decomposition of Hydrogen Peroxide in Aqueous Solutions in Presence of Sodium Nitroprusside. I

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemical Decomposition of Hydrogen Peroxide in Aqueous Solutions in Presence of Sodium Nitroprusside. IM. QureshiM. QureshiMore by M. QureshiCite this: J. Phys. Chem. 1931, 35, 2, 656–658Publication Date (Print):February 1, 1931Publication History Published online1 May 2002Published inissue 1 February 1931https://doi.org/10.1021/j150320a025RIGHTS & PERMISSIONSArticle Views66Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (170 KB) Get e-Alerts

The Photochemical Decomposition of Hydrogen Peroxide, II

The Photochemical Decomposition of Hydrogen Peroxide, II

The Photochemical Decomposition of Hydrogen Peroxide I

The Photochemical Decomposition of Hydrogen Peroxide I