Search results for "O2"
showing 10 items of 1115 documents
Sol-gel synthesis and photocatalytic activity of ZnO-SnO2 nanocomposites
2014
Abstract ZnO–SnO 2 nanocomposites were synthesized by a facile sol–gel synthesis route and characterized through X-ray diffraction, BET specific surface area analysis, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy. The photocatalytic activity of the samples was tested using the degradation of 4-nitrophenol under UV light as model reaction. The ZnO/SnO 2 molar ratio was varied in order to study its influence on the photoefficiency of the samples. The ZnO–SnO 2 nanocomposites showed higher photoactivity than the pure oxides and in particular the sample with ZnO/SnO 2 mol…
Photocatalytic behaviour of metal-loaded TiO2 aqueous dispersions and films
2007
Abstract Titanium dioxide nanoparticles loaded with Ce, Co, Eu, Sm, W and Yb species were prepared by coprecipitation in mild conditions using TiCl 4 as precursor with the aim to enhance the photocatalytic activity, especially under visible light irradiation. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (SSA) determination and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the powders of pure and loaded TiO 2 was investigated by employing the photodegradation of 4-nitrophenol as probe reaction in a liquid–solid system. Loading with suitable amounts of W, Co and Sm resulted in a significan…
Electro- and Photo-driven Reduction of CO 2 by a trans -(Cl)-[Os(diimine)(CO) 2 Cl 2 ] Precursor Catalyst: Influence of the Diimine Substituent and A…
2016
A series of [OsII(NN)(CO)2Cl2] complexes where NN is a 2,2′-bipyridine ligand substituted in the 4,4′ positions by H (C1), CH3 (C2), C(CH3)3 (C3), or C(O)OCH(CH3)2 (C4) has been studied as catalysts for the reduction of CO2. Electrocatalysis shows that the selectivity of the reaction can be switched toward the production of CO or HCOO− with an electron-donating (C2, C3) or -withdrawing (C4) substituent, respectively. The electrocatalytic process is a result of the formation of an Os0-bonded polymer, which was characterized by electrochemistry, UV/Visible and EPR spectroscopies. Photolysis of the complexes under CO2 in DMF+TEOA produces CO as a major product with a remarkably stable turnover…
Calcification is not the Achilles'heel of cold-water corals in an acidifying ocean
2015
Ocean acidification is thought to be a major threat to coral reefs: laboratory evidence and CO2 seep research has shown adverse effects on many coral species, although a few are resilient. There are concerns that cold-water corals are even more vulnerable as they live in areas where aragonite saturation (Omega ara) is lower than in the tropics and is falling rapidly due to CO2 emissions. Here, we provide laboratory evidence that net (gross calcification minus dissolution) and gross calcification rates of three common cold-water corals, Caryophyllia smithii, Dendrophyllia cornigera, and Desmophyllum dianthus, are not affected by pCO2 levels expected for 2100 (pCO2 1058 µatm, Omega ara 1.29),…
The Existence of Nitrate Radicals in Irradiated TiO 2 Aqueous Suspensions in the Presence of Nitrate Ions
2018
Evidence of the existence of nitrate radical in irradiated aqueous TiO2 suspensions in the presence of nitrate ions are reported for the first time. The joint use of UV/Vis and EPR spectroscopy showed that nitrate radicals are formed by hole induced oxidation of nitrate ions. Photocatalytic degradation of a model alkene compound allowed to highlight the presence of an intermediate organic nitrate deriving from nitrate radical attack to the double bond of the substrate. These results not only allow deeper understanding of photocatalytic processes, but open the route to new green photocatalytic syntheses initiated by nitrate radicals and to new insights in the field of atmospheric chemistry.
Luminescence of gamma-radiation-induced defects in alpha-quartz
2004
Optical transitions associated with gamma-radiation-induced defects in crystalline a-quartz were investigated by photoluminescence excited by both pulsed synchrotron radiation and steady-state light. After a 10 MGy gamma-dose we observed two emissions at 4.9 eV (ultraviolet band) and 2.7 eV (blue band) excitable in the range of the induced absorption band at 7.6 eV. These two luminescence bands show a different temperature dependence: the ultraviolet band becomes bright below 80 K; the blue band increases below 180 K, but drops down below 80 K. Both emissions decay in a timescale of a few ns under pulsed excitation, however the blue band could also be observed in slow recombination processe…
Comment réduire les émissions de CO2 du transport de fret en France ? Evaluation socio-économique de trois politiques publiques
2018
France must implement voluntarist policies in order to reduce CO2 emissions, which raises questions regarding the effectiveness of competing options and their costs, for both public finances and society. This paper estimates abatement costs of one ton of CO2 from three scenarios aimed at softening the environmental impacts of freight moved by trucks. Hybrid trucks may generate large CO2 savings (5.7 Mt/year in 2030), at a moderate discounted abatement cost (88 €/t). The option based on natural gas for vehicles leads to a similar abatement cost and to lower environmental gains (3.2 Mt/year in 2030). Whilst inducing small CO2 savings (0.2 Mt/year in 2030), megatrucks present a negative discou…
EUROPA 2020 IN SICILIA: SPIN-OFF DI RICERCA, DISTRETTI HIGH-TECH E STRATEGIE DI INNOVAZIONE ISTITUZIONALE
2014
Gli indicatori di posizione che quantificano le priorità della strategia Europa 2020 denunciano un ritardo nello sviluppo della Sicilia rispetto alle altre regioni italiane. Per ridurre tali divari si propongono strategie trainate dall`innovazione quali ad esempio distretti tecnologici e spin-off di ricerca. Dopo un excursus di letteratura volto a mettere a confronto queste due forme di innovazione tecnologica ed organizzativa, viene proposto un esercizio empirico che intende verificare quanto la creazione di imprenditorialità da parte dell’Università può contribuire alla riduzione dei divari di sviluppo. Si intende proporre alcune suggerimenti di policy per aumentare la loro efficacia nell…
Impact of geogenic degassing on C-isotopic composition of dissolved carbon in karst systems of Greece
2022
The Earth C-cycle is complex, where endogenic and exogenic sources are interconnected, operating in a multiple spatial and temporal scale (Lee et al., 2019). Non-volcanic CO2 degassing from active tectonic structures is one of the less defined components of this cycle (Frondini et al., 2019). Carbon mass-balance (Chiodini et al., 2000) is a useful tool to quantify the geogenic carbon output from regional karst hydrosystems. This approach has been demonstrated for central Italy and may be valid also for Greece, due to the similar geodynamic settings. Deep degassing in Greece has been ascertained mainly at hydrothermal and volcanic areas, but the impact of geogenic CO2 released by active tect…
Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue-Caviahue Volcanic Complex (Argentina)
2015
Fil: Chiodini, Giovanni. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna. Bologna, Italia. Fil: Cardellini, Carlo. Università degli Studi di Perugia, Dipartimento di Fisica e Geologia. Perugia, Italy. Fil: Lamberti, María C. Universidad de Buenos Aires. Instituto de Estudios Andinos. Buenos Aires, Argentina. Fil: Agusto, Mariano. Universidad de Buenos Aires. Instituto de Estudios Andinos. Buenos Aires, Argentina. Fil: Caselli, Alberto Tomás Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro. Argentina. Fil: Liccioli, Caterina. Universidad de Buenos Aires. Instituto de Estudios Andinos. Buenos Aires, Argentina. Fil: Tambure…