Occurrence, behavior and effects of nanoparticles in the environment.

Recent advances in transition metal catalyzed oxidation of organic substrates with molecular oxygen.

The oxidative environment and protein damage

Marine dissolved organic matter (DOM) is a complex mixture of molecules found throughout the world's oceans. It plays a key role in the export, distribution, and sequestration of carbon in the oceanic water column, posited to be a source of atmospheric climate regulation. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, focuses on the chemical constituents of DOM and its biogeochemical, biological, and ecological significance in the global ocean, and provides a single, unique source for the references, information, and informed judgments of the community of marine biogeochemists. Presented by some of the world's leading scientists, this revised edition reports on the major advances in this area and includes new chapters covering the role of DOM in ancient ocean carbon cycles, the long term stability of marine DOM, the biophysical dynamics of DOM, fluvial DOM qualities and fate, and the Mediterranean Sea. Biogeochemistry of Marine Dissolved Organic Matter, Second Edition, is an extremely useful resource that helps people interested in the largest pool of active carbon on the planet (DOC) get a firm grounding on the general paradigms and many of the relevant references on this topic. * Features up-to-date knowledge of DOM, including five new chapters* The only published work to synthesize recent research on dissolved organic carbon in the Mediterranean Sea* Includes chapters that address inputs from freshwater terrestrial DOM

Biogeochemistry of marine dissolved organic matter

The remarkable achievement by Fujishima and Honda (1972) in the photo-electrochemical water splitting results in the extensive use of TiO 2 nanomaterials for environmental purification and energy storage/conversion applications. Though there are many advantages for the TiO 2 compared to other semiconductor photocatalysts, its band gap of 3.2 eV restrains application to the UV-region of the electromagnetic spectrum ( λ  ≤ 387.5 nm). As a result, development of visible-light active titanium dioxide is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in the strategies for the visible light activation, origin of visible-light activity, and electronic structure of various visible-light active TiO 2 photocatalysts are discussed in detail. It has also been shown that if appropriate models are used, the theoretical insights can successfully be employed to develop novel catalysts to enhance the photocatalytic performance in the visible region. Recent developments in theory and experiments in visible-light induced water splitting, degradation of environmental pollutants, water and air purification and antibacterial applications are also reviewed. Various strategies to identify appropriate dopants for improved visible-light absorption and electron–hole separation to enhance the photocatalytic activity are discussed in detail, and a number of recommendations are also presented.

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Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments

Incorporation of C60 into artificial lipid membranes

The oxidative degradation of chlorinated ethanes proceeds practically via the same mechanism in [gamma]-radiolysis and photocatalysis at TiO[sub 2] surfaces, respectively. C-centered radicals generated via hydroxyl radical induced C-H bond cleavage and peroxyl radicals derived therefrom after oxygen addition are the key radical intermediates in these processes. The main molecular products identified and isolated in both the [gamma]-radiolytic and photocatalytic experiments are organic (mostly chlorinated) acids, HCl, and CO[sub 2]. Other products formed in minor yields are aldehydes and HCOOH. Photocatalytic degradation of these product acids and nonionic substrates leads eventually to complete mineralization. The results strongly suggest that the photocatalytic degradation is initiated by an oxidation of the chlorinated compounds through TiO[sub 2]-surface-adsorbed hydroxyl radicals. Only some acids, like trichloroacetic acid and oxalic acid, seem to be oxidized primarily by valence band holes via a photo-Kolbe process. Several rate constants are reported on the oxidation of chlorinated ethanes and acids by free and surface-adsorbed hydroxyl radicals and on the overall photocatalytic degradation of the chlorinated compounds. The paper also includes a discussion of the material balance. The study demonstrates the value of radiation chemical investigations for the understanding of the details in the photocatalytic mineralization process of halogenated organicmore » compounds.« less

Identification of organic acids and other intermediates in oxidative degradation of chlorinated ethanes on titania surfaces en route to mineralization: a combined photocatalytic and radiation chemical study

Redox and alkylation (radical addition) reactions with C[sub 60] have been investigated by means of radiation chemical methods, particularly time-resolved radiolysis measurements. All experiments were conducted in solutions at room temperature. The primary radical products, namely, the C[sub 60][sup [sm bullet][minus]] radical anion, the C[sub 60][sup [sm bullet]+] radical cation and radical adducts (C[sub 60]-R)[sup [sm bullet]], exhibit distinct absorption bands in the IR at 1080, 980 (corroborating earlier low-temperature matrix and photochemical experiments), and around 900 nm, respectively. Reductions, to yield the C[sub 60][sup [sm bullet][minus]] radical anion (and at longer steady-state irradiations also more highly reduced states), could be achieved by solvated electrons and (CH[sub 3])[sub 2]C(OH)[sup [sm bullet]] radicals in 2-propanol solutions and toluene/acetone/2-propanol mixtures with rate constants of [ge]10[sup 10] and 8.5 x 10[sub 8] M[sup [minus]1] s[sup [minus]1], respectively. The reaction of a water-soluble C[sub 60]-[gamma]-cyclodextrin complex (C[sub 60]/[gamma]-CD) with [alpha]-hydroxyalkyl radicals also involves electron transfer, as indicated by the dependence of the rate constants on the redox potential of the reducing radicals: 2.7 [times] 10[sup 8] M[sup [minus]1] s[sup [minus]1] for (CH[sub 3])[sub 2]C(OH)[sup [sm bullet]], 1.4 [times] 10[sup 8] M[sup [minus]1] s[sup [minus]1] for CH[sub 3]CH(OH)[sup [sm bullet]], and 0.5 [times] 10[sup 8]more » M[sup [minus]1] s[sup [minus]1] for [sup [sm bullet]]CH[sub 2](OH). 44 refs., 9 figs., 2 tabs.« less

Redox processes and alkylation reactions of fullerene C60 as studied by pulse radiolysis

Effet des substituants inducteurs d'electrons R sur la stabilite de (R 2 S...SR 2 ) + , (RS...SR) − et R 2 S...B 2 . L'etude est faite par radiolyse pulsee

Substituent effects on the stability of three-electron-bonded radicals and radical ions from organic sulfur compounds

The sulfoxide yield in the . OH radical-induced oxidation of dimethylsulfide in aqueous solution is dramatically enhanced by admission of molecular oxygen. Various possible mechanistic pathways leading to sulfoxide can now be eliminated from speculation as a result of a detailed study on the influence of sulfide concentration, pH, isotope effects, radical cation stability and deprotonation kinetics, and electron-transfer reactions from transient radicals to special additives. The major route to sulfoxide is demonstrated to involve a 2σ/1σ * three-electron-bonded radical cation, (>S.-.S S(OH)S-<

Klaus Dieter Asmus

Papers

Incorporation of C60 into artificial lipid membranes

Identification of organic acids and other intermediates in oxidative degradation of chlorinated ethanes on titania surfaces en route to mineralization: a combined photocatalytic and radiation chemical study

Redox processes and alkylation reactions of fullerene C60 as studied by pulse radiolysis

Substituent effects on the stability of three-electron-bonded radicals and radical ions from organic sulfur compounds

Mechanism of oxidation of aliphatic thioethers to sulfoxides by hydroxyl radicals. The importance of molecular oxygen