1,721,177 research outputs found
Preparation and characterisation of some nano-structured catalytic materials for low-temperature oxidation of carbon monoxide
No full textThis project is focused on the synthesis, modification and characterization of rhodium based catalysts supported on MCM-41 mesoporous silica to produce well-defined active sites for catalysis of CO oxidation at low-temperature. The Rh catalysts were prepared by incipient wetness impregnation (IWI) then modified by the inclusion of different transition metal oxides (ca. CeOx, ZrOx, CrOx, Ce0.5Zr0.5Ox and Ce0.5Cr0.5Ox) via two different routes. The first was achieved by pre-modification of MCM-41 support during its synthesis using the inorganic precursors of the promoter oxides followed by the addition of the specified Rh precursor (0.5 - 2.5 wt%), i.e. post-synthesis of Rh catalysts. The second route was performed by the post addition of the promoters using their non-inorganic sources [ca. Ce(acac)3, Zr(acac)4 and bis(benzene)chromium] by the controlled surface modification (CSM) method. The catalysts were characterized by using TGA, FT-IR, N2 physisorption analysis, PXD, SEM-EDX, TEM, DR UV/Vis spectroscopy and XPS. Furthermore, the structure-performance relationship and the dependence of the preparation method towards CO oxidation were also investigated by in situ QEXAFS-MS spectroscopy in the temperature range of 300 - 573 K. The combination of soft and hard X-ray absorption edges was applied to in situ structural studies. In addition to the Rh K-edge, the Ce L3, Zr K or Cr K-edges were used as probes of the catalysts as a function of temperature (300 - 573 K) under of different ambient gases (He, 10% H2/He, 10% O2/He and 10% CO/O2/He) during activation and reaction conditions. As a result, the fractions of Rh active species, coordination numbers and atom-to-atom distances were extracted from analysis of XANES and EXAFS results. In addition, the turnover frequency (TOF) values and CO conversion% over these catalysts were also calculated. The results revealed that Rh species and/or the promoter oxides prepared by both two methods were well confined into the mesoporous framework of silica support in amorphous nano-sized scale. However, the distribution of the Rh atoms and/or the promoter oxides depends mainly on the preparation method with much more homogeneity and local vicinity in those prepared by the CSM method. Furthermore, the preparation method played a crucial rule not only in the local structure, but also in the catalysts performance towards CO oxidation with high activity for catalysts prepared by CSM
Dataset supporting the publication "Structural selectivity of supported Pd nanoparticles: Selective ethanol ammoxidation to acetonitrile"
No full textDataset supporting the publication "Structural selectivity of supported Pd nanoparticles: Selective ethanol ammoxidation to acetonitrile" in EES Catalysis, https://doi.org/10.1039/D4EY00044G
Data is supporting the figures in the main text and ESI is presented in excel files. The data is zipped into Figures.zip file.
The data is accessible via CC BY licence.
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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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Facile synthesis and grafting of N<sub>2</sub>O<sub>2</sub>-Cu(II) Schiff base complex onto graphene oxide surface: aspects of its antimicrobial, anticancer, antiCOVID-19 and photodegradation of methylene blue
No full textIn this study, a facile synthesis and grafting method is reported for tetradentate Cu(II) Schiff base complex onto the surface of graphene oxide (GO). The Schiff base Cu-complex was synthesized through the condensation reaction between 2,3-diamino pyridine and 2-hydroxy-1-naphthaldehyde, followed by the addition of Cu(II) ion to afford N2O2-Cu(II) complex. The GO was prepared through a modified Hummers’ method and characterized using various spectroscopic and microscopic techniques. The Schiff base Cu-complex was then grafted onto the surface of GO via a simple solution-phase reaction, resulting in the formation of N2O2-Cu(II) Schiff base/GO composite. The fabricated composite was characterized using FTIR spectroscopy, UV–vis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Importantly, the prepared N2O2-Cu(II) Schiff base complex exhibited excellent DNA interaction as well as efficient antimicrobial and anticancer activities. Additionally, it demonstrated potent anticancer activity against hepatocellular carcinoma cells (HepG-2), and colon cancer cells (HCT-116) and exhibited promising activity against the COVID-19 receptor (PDB ID: 6LU7) along with the human DNA receptor (PDB ID: 1BNA). Furthermore, this fabricated heterogeneous catalyst showed enhanced photodegradation of MB with ≈92% conversion and four times recyclability. The overall results suggest that the Cu(II) Schiff base/GO composite has potential applications in various medical and environmental fields, including photodegradation/elimination of harmful organic dyes for water treatment applications.</p
Lithium manganite anchored on mesoporous ceria photocatalyst for removal of Hg(II) ions from aqueous solution under visible illumination
No full textThe development of effective photocatalysts is critical for the photo/redox reaction of noxious Hg(II) ions and Hgo in environmental engineering and purification. In this contribution, Li2MnO3 nanoparticles (NPs) were anchored mesoporous CeO2 networks to design photocatalysts with high harvest of visible light, and the obtained Li2MnO3/CeO2 nanocomposites were utilized for photoreduction of Hg(II) ions under visible illumination. The TEM and XRD results showed the formation of Li2MnO3 and CeO2 with the monoclinic and cubic fluorite structures, and the particle size is about 10–20 nm. The enhancement of light absorption of Li2MnO3/CeO2 nanocomposites could create considerable photoinduced carriers during the photocatalytic reactions. The incorporation of Li2MnO3 and CeO2 NPs demonstrated outstanding photocatalytic performance compared with pristine CeO2 NPs, and the optimum 9%Li2MnO3/CeO2 nanocomposite achieved 98 % of the reduction Hg(II) ability within 60 min. The rate constant for 9 % Li2MnO3/CeO2 photocatalyst is ∼ 6.47 and 3.85 times greater than Li2MnO3 and CeO2 NPs. The superior photocatalytic performance of Li2MnO3/CeO2 nanocomposites was ascribed to the efficient separation of photocarriers due to the formation of S-scheme heterojunction, the large surface area, and mesoporous structures. The obtained Li2MnO3/CeO2 nanocomposite was highly stable and efficient for the Hg(II) photoreduction runs up to five successive experiments under similar conditions. Moreover, the possible mechanism over heterojunctions Li2MnO3/CeO2 nanocomposites toward the reduction of Hg(II) ions is examined as well. The formation of S-scheme heterojunction photocatalyst provides better photocatalytic applications in terms of air purification, hydrogen production, and water treatment.</p
Home-made chemical vapor deposition-based synthesis of binder-free nanostructured magnesium-molybdenum-sulfide electrode materials for supercapacitor application
No full textMolybdenum disulfides (MoS2) is considered as promising electrode materials (E-M) for high electrochemical performance (ECP) of lithium-ion batteries and supercapacitors due to their layered nanostructures. Herein, MoS2, MgS and hetrostructure MgS/MoS2 E-Ms comprising of nano-particles/sheets/needles like structures are synthesized on Nickel foam (Ni–F) by a simple home-made chemical vapor deposition (CVD) technique. The XRD analysis confirmed the formation of MoS2, MgS and MgS/MoS2 polycrystalline E-Ms growing along different directions. The FESEM analysis is confirmed that the addition of MgS layer over the surface of MoS2 change the surafce morphology from nano-particles to nano-needles. The change in structural and microstructural features is indicated the appearance of defects, micro-strain and dislocations density which are fruitful for excellent ECP. The cyclic voltammetry analysis is indicated the pseudocapacitive nature of the synthesized E-Ms. The maximum specific capacitance values for MoS2/Ni–F, MgS/Ni–F and MgS/MoS2/Ni–F E-Ms are 1273, 1688 and 3934 F/g at 1 A/g respectively. Moreover, the addition of MgS layer over MoS2/Ni–F is revealed the excellent cyclic stability of 98.76 % at current density of 10 A/g after 4000 cycles, energy density values are ranged from 79 to 136 W h/kg with homologous power density of 250–2500 W/kg and very small charge transfer resistance. The simulations of Power's Law and Dunn's model is confirmed that the excellent ECP is due to both capacitive and diffusive controlled contributions of heterostructured MgS/MoS2/Ni–F E-Ms. Additionally, MgS/MoS2/Ni–F E-Ms have both battery and pseudocapacitive nature due to unique nano-needles like morphology. The excellent electrochemical properties of MgS/MoS2/Ni–F E-Ms substantiate their potential applications in portable energy storage devices.</p
Al-doped Fe<sub>2</sub>O<sub>3</sub>as a support for molybdenum oxide methanol oxidation catalysts
Full text linkWe have made high surface area catalysts for the selective oxidation of methanol to formaldehyde. This is done in two ways-(i) by doping haematite with Al ions, to increase the surface area of the material, but which itself is unselective and (ii) by surface coating with Mo which induces high selectivity. Temperature programmed desorption (TPD) of methanol shows little difference in surface chemistry of the doped haematite from the undoped material, with the main products being CO2 and CO, but shifted to somewhat higher desorption temperature. However, when Mo is dosed onto the haematite surface, the chemistry changes completely to show mainly the selective product, formaldehyde, with no CO2 production, and this is little changed up to 10% Al loading. But at 15 wt% Al, the chemistry changes to indicate the presence of a strongly acidic function at the surface, with additional dimethyl ether and CO/CO2 production characteristic of the presence of alumina. Structurally, X-ray diffraction (XRD) shows little change over the range 0-20% Al doping, except for some small lattice contraction, while the surface area increases from around 20 to 100 m2 g-1. Using X-ray absorption spectroscopy (XAS) it is clear that, at 5% loading, the Al is incorporated into the Fe2O3 corundum lattice, which has the same structure as α-alumina. By 10% loading then it appears that the alumina starts to nano-crystallise within the haematite lattice into the γ form. At higher loadings, there is evidence of phase separation into separate Al-doped haematite and γ-alumina. If we add 1 monolayer equivalent of Mo to the surface there is already high selectivity to formaldehyde, but little change in structure, because that monolayer is isolated at the surface. However, when three monolayers equivalent of Mo is added, we then see aluminium molybdate type signatures in the XANES spectra at 5% Al loading and above. These appear to be in a sub-surface layer with Fe molybdate, which we interpret as due to Al substitution into ferric molybdate layers immediately beneath the topmost surface layer of molybdena. It seems like the separate γ-alumina phase is not covered by molybdena and is responsible for the appearance of the acid function products in the TPD. </p
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