1,720,984 research outputs found
Effect of the electrolyte cations on photoinduced charge transfer at TiO2
No full textThis work focuses on the effect of electrolyte cations on the behaviour of a probe photocatalytic system comprising 2-propanol and 4-nitrobenzaldehyde (O2NC6H4CHO) as the hole and electron scavenger, respectively. Photo-reductionofthe latter occurs via a stepwise pathway involving 4-aminobenzaldehyde (H2NC6H4CHO) as the stable intermediate and 4-aminobenzyl alcohol (H2NC6H4CH2OH) as the final product. 2-propanol photo-oxidation produces protons at the surface. The complete reduction of O2NC6H4CHO to H2NC6H4CH2OH needs photo-charging. Excess negative charge is compensated by cations adsorption and by lattice insertion. In the case of bulky K+ and TEA+ (tetraethylammonium ions) that apparently are not inserted, protons are inserted instead. In contrast, Li+ (and to a lesser degree Na+) ions favour selective reduction of O2NC6H4CHO to H2NC6H4CHO. Electrochemical measurements in the dark provide evidence of a strong interaction of 2-propanol with the surface and of the influence exerted by cations thereon. Additionally, electron paramagnetic resonance (EPR) spin trapping spectroscopy gives information about the formation of radicals intermediates from the alcohol photo-oxidation. Repeated illumination/dark runs showed that alkoxy (R-O•) radicals always formed when the electrolyte contains K+ or TEA+. Conversely, in prolonged experiments, Li+ favours the formation of hydroxyalkyl radicals (R-C•HOH), which indicates a non-dissociative interaction of 2-propanol with the surface. This weaker interaction can be reasonably ascribed to the know ability of TiO2 inserted Li+ to cause the formation of a new phase of the type LixTiO2
N-TiO2 Photocatalysts highly active under visible irradiation for NOX abatement and 2-propanol oxidation
Full text linkN-doped TiO2 powders were prepared by two different sol–gel methods. Samples were characterised
by X-ray diffraction (XRD), BET specific surface area measurements (SSA), scanning electron microscopy
(SEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Electron Paramagnetic
Resonance (EPR). XPS measurements revealed a signal at 400 eV assignable to nitrogen in the
form of Ti N O. EPR signals are attributed to molecular NO trapped with cavities/defects possibly interacting
with oxygen vacancies. The photocatalytic activity under UV and visible light was determined
following the abatement of NOx and the photodegradation of 2-propanol in gas–solid systems. N-doped
TiO2 showed a higher activity compared with the pristine commercial and home prepared samples
under visible light irradiation. A good photoactivity in the abatement of both NOx and 2-propanol is
also observed for mechanical dispersions of N-TiO2 in CaCO3 serving as a model in view of perspective
application in photocatalytically active construction and architectural materials
“Tetralkylammonium and sodium decatungstate heterogenized on silica: Effects of the nature of cations on the photocatalytic oxidation of organic substrates”
No full textTHERMAL AND PHOTOCHEMICAL BEHAVIOR OF ORGANOTETRARUTHENIUM CLUSTERS: SOLUTION STRUCTURES AND DYNAMICS OF PHOSPHINE-SUBSTITUTED DERIVATIVES
No full text
Photocatalytic formation of a carbamate through ethanol-assisted carbonylation of p-nitrotoluene
No full textThe nitroarene p-nitrotoluene is converted with a selectivity higher than 85% to the corresponding carbamate at room temperature and atmospheric pressure, using photoexcited particles of TiO2 as catalyst and EtOH as carbonylating species
Preparation, Characterisation, and Photocatalytic Behaviour of Co-TiO2 with Visible Light Response
Full text linkThe preparation of cobalt-modified TiO2 (Co-TiO2) was carried out by the incipient impregnation method starting from commercial TiO2 (Degussa, P-25) and cobalt acetate. XPS data show that cobalt is incorporated as divalent ion, and it is likely present within few subsurface layers. No appreciable change in structural-morphologic properties, such as surface area and anatase/rutile phase ratio, was observed. Conversely, Co addition brings about conspicuous changes in the point of zero charge and in surface polarity. Diffuse reflectance spectra feature a red shift in light absorption that is dependent on the amount of cobalt. The influence of cobalt addition on the performance of TiO2 as a photocatalyst in the degradation of 4-chlorophenol and Bisphenol A is investigated. The results show that the modified oxide presents a higher photoactivity both for illumination with UV-visible (λ>360 nm) and visible light (λ>420 nm; λ>450 nm), and that this enhancement depends on the amount of the added species and on the final thermal treatment in the preparation step. We also show that Co-TiO2 is a more active catalyst than pure TiO2 for the reduction of O2 in the dark, which is an important reaction in the overall photocatalytic processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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