1,721,022 research outputs found
XPS surface characterization to unravel nanomaterials properties
No full textThe chemical surface composition of a nanomaterial is fundamental to determine its properties. In this paper different nanomaterials will be discussed in terms of surface speciation and related properties and peculiarities
Valorization of C5 polyols by direct carboxylation to FDCA: Synthesis and characterization of a key intermediate and role of carbon dioxide
No full textReplacing fossil-C based plastics with those derived from renewable-C is one of the goals of the modern polymer industry. 2,5-Furan dicarboxylic acid (2,5-FDCA) is a candidate to substitute terephthalic acid as comonomer for polyesters. 2,5-FDCA is usually produced from C6 sugars. Carboxylation of 2-furancarboxylic acid (2-FCA) to 2,5-FDCA is an alternative synthetic approach to such monomer for polyethene furoate (PEF) preparation. In this work, several inorganic carbonates have been tested in the 2-FCA carboxylation in presence and absence of CO 2 . A key copper intermediate has been synthesized and fully characterized that is able to increase the acidity and, thus, the reactivity of 5-H towards a carbonate species. Carboxylation occurs at 93% yield in absence of CO 2 . The role of metal salts and CO 2 were investigated. The conversion yield of 2-FCA into the dicarboxylic acid is related to the charge density on the metal cation, increasing with lower charge-density
Synthesis and characterization of p-n junction ternary mixed oxides for photocatalytic coprocessing of CO2 and H2O
Full text linkIn the present paper, we report the synthesis and characterization of both binary (Cu2 O, Fe2 O3, and In2 O3 ) and ternary (Cu2 O-Fe2 O3 and Cu2 O-In2 O3 ) transition metal mixed-oxides that may find application as photocatalysts for solar driven CO2 conversion into energy rich species. Two different preparation techniques (High Energy Milling (HEM) and Co-Precipitation (CP)) are compared and materials properties are studied by means of a variety of characterization and analytical techniques UV-Visible Diffuse Reflectance Spectroscopy (UV-VIS DRS), X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Energy Dispersive X-Ray spectrometry (EDX). Appropriate data elaboration methods are used to extract materials bandgap for Cu2 O@Fe2 O3 and Cu2 O@In2 O3 prepared by HEM and CP, and foresee whether the newly prepared semiconductor mixed oxides pairs are useful for application in CO2-H2 O coprocessing. The experimental results show that the synthetic technique influences the photoactivity of the materials that can correctly be foreseen on the basis of bandgap experimentally derived. Of the mixed oxides prepared and described in this work, only Cu2 O@In2 O3 shows positive results in CO2-H2 O photo-co-processing. Preliminary results show that the composition and synthetic methodologies of mixed-oxides, the reactor geometry, the way of dispersing the photocatalyst sample, play a key role in the light driven reaction of CO2 –H2 O. This work is a rare case of full characterization of photo-materials, using UV-Visible DRS, XPS, XRD, TEM, EDX for the surface and bulk analytical characterization. Surface composition may not be the same of the bulk composition and plays a key role in photocatalysts behavior. We show that a full material knowledge is necessary for the correct forecast of their photocatalytic behavior, inferred from experimentally determined bandgaps
Highly dispersed Ni-Ce catalyst over clay montmorillonite K10 in low-temperature CO2 methanation
Full text linkThe Carbon Capture and Utilization (CCU) option can be an efficient solution for CO2 emission mitigation. To this end, we have investigated the carbon dioxide methanation at low temperatures. Highly active, selective, stable, low-cost catalysts are required for energy and carbon balance benefits. Supported nickel-based catalysts result as the most studied and promising candidates showing a good compromise between performance and low preparation costs. The catalyst design role is key to obtaining the best performance, requiring many experiments and optimisation procedures. Herein, the enhanced Montmorillonite MK10-supported Ni(0)Ce(III) catalyst, prepared by consecutive hydrothermal and electrostatic adsorption methods followed by reduction under hydrogen flow, was used in batch CO2 methanation, exhibiting 76 % of CO2 conversion with 100 % CH4 selectivity after 3 h. The catalytic system reveals very high robustness preserving the same activity and selectivity for at least 5 reaction cycles if compared with γ-Al2O3-supported Ni(0)Ce(III) catalyst, the latter showing the same activity but only in the first cycle. EDX, XPS, SEM, TPD, TPR, and BET characterisation techniques were used to elucidate and evaluate the potential synergistic effect of the active metal centre-promoter-support interfaces, highlighting their role in the activity and robustness of the catalyst, comparing the same effect using different alumina and silicate solid supports. The effects of the reaction conditions on the methane yield and selectivity were also evaluated
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
Photocatalytic Disinfection of Selected Waterborne Pathogens by Visible Light-Active Nano Iron-Doped TiO2 Obtained by a Sol-Gel Method
No full textBacterial contamination in drinking water systems poses a serious health risk due to poor hygiene, human activities, and cross-contamination within the water supply. This study examines the potential of iron-doped titanium oxide nanometric powder (Fe-TiO2) for the photocatalytic disinfection of Gram-negative E. coli and Gram-positive S. aureus under visible light. The Fe-TiO2 photocatalyst, with an optimal nominal content of 2.5 wt % Fe, was synthesized using a surfactant-assisted sol-gel method, resulting in a mesoporous nanomaterial composed of anatase nanoparticles with a specific surface area of 123 m2/g. A sample of undoped anatase TiO2, obtained using the same sol-gel method and exhibiting a specific surface area of 116 m2/g, was utilized to confirm the role of Fe-doping in disinfection. The nanopowders were characterized using X-ray diffraction, N2 sorption at −196 °C, diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy, electrophoretic mobility measurements, high-resolution transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy. Photocatalytic disinfection tests were conducted using 1 and 0.5 g/L Fe-TiO2 with varying initial bacterial concentrations, with 1 g/L yielding the most promising results under the experimental conditions employed. After 240 min of treatment with 1 g/L Fe-TiO2, a 99.9% removal of both E. coli and S. aureus was achieved starting from a bacterial concentration of 1 × 106 CFU/mL. A 99.9% removal of E. coli and a 99.8% removal of S. aureus were achieved starting from 1 × 104 CFU/mL. The Fe-TiO2 nanomaterial was effective against high concentrations of both bacteria under visible light. Reusability was studied by recovering the Fe-TiO2 nanoparticles and assessing their performance over three cycles. The photocatalytic disinfection effectiveness of Fe-TiO2 nanoparticles under visible light was validated using an actual tap water sample containing 167 CFU/mL total coliforms and 8 CFU/mL E. coli. The bacteria were photocatalytically inactivated within 30 min
Novel Chitosan nanoparticles for administration of low molecular weight heparin to the lung
No full textAbstracts of paper
Pros and Cons of Sacrificial Anode Electrolysis for the Preparation of Transition Metal Colloids: A Review
No full textElectrochemical synthesis of transition metal nanoparticles (NPs) and related oxides is highly appealing, as it affords nanomaterials with high purity and dimensional control by properly setting only few experimental parameters. The resurgence of electrochemical routes to NPs can be traced back to seminal works by the Reetz's group, about 25 years ago. Despite many advantages, this method has intrinsic limitations, mainly related to the use of organic solvents, which may limit real-life applications of the as-prepared NPs. Therefore, an important current issue in the electrosynthesis of these systems regards the preparation of aqueous and long-lived colloids. In this Review, we provide an overview of the most promising electrosyntheses of colloidal nanomaterials; real-life applications of electrochemically produced NPs will also be commented on
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