Composite Material for Supercapacitors Formed by Polymerization of Aniline in the Presence of Graphene Oxide Nanosheets

The composite material was obtained by the polymerization of aniline in the presence of graphene oxide nanosheets (GONS). The resulting composite PANi (72%) - GONS (28%) was investigated by methods such as XPS, TGA, Raman and IR spectroscopy, and so on. It was established that a partial reduction of graphene oxide takes part in course of the polymerization. Specific capacitance of the PANi-GONS electrode in 1M H2SO4, corresponding to its discharge from 0.700 to 0.052 V, was found to be 547 F/g. But, if in the calculation of the capacitance include a shallow part of the discharge curve (below 0.15 V), one can obtain the value of specific capacity greater than 1200 F/g. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3523

Photocatalytic activity of a new composite material of Fe (III) oxide nanoparticles wrapped by a matrix of polymeric carbon nitride and amorphous carbon

Polymeric carbon nitride was synthesized from urea and doped with Cu and Fe to act as co-catalysts. The material doped with Fe was a new composite material composed of Fe(III) oxides (acting as a co-catalyst) wrapped by the polymer layers and amorphous carbon. Furthermore, the copper doped material was described in a previous report. The photocatalytic degradation of the azo dye direct blue 1 (DB) was studied using as photocatalysts: pure carbon nitride (CN), carbon nitride doped with Cu (CN-Cu) and carbon nitride doped with Fe (CN-Fe). The catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), by X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller method (BET), etc. The adsorption phenomenon was studied using the Langmuir and Freundlich models. For the kinetic study, a solution of 500 mg L-1 of DB1 was treated with each catalyst, visible light and H2O2. The dye concentration was measured by spectrophotometry at the wavelength of 565 nm, and the removal of the total organic content (TOC) was quantified. BET analysis yielded surface areas of 60.029, 20.116 and 70.662 m2g-1 for CN, CN-Cu and CN-Fe, respectively. The kinetics of degradation were pseudo-first order, whose constants were 0.093, 0.039 and 0.110 min-1 for CN, CN-Cu and CN-Fe, respectively. The total organic carbon (TOC) removal reached the highest value of 14.46% with CN-Fe

Mechanistic Aspects on the Electrografting of Carbon Surfaces by Oxidation of Carboxylates Bearing Unsaturated Groups

The anodic oxidation of tetrabutylammonium carboxylates bearing aromatic or unsaturated terminal groups is a reaction that allows the covalent grafting of organic moieties on carbon electrodes in acetonitrile as solvent. The electron transfer step is followed by a fast decarboxylation reaction, which releases the respective unsaturated free radicals, whose transient formation at the interface explain the surface grafting phenomenon, however; the lack of grafting during the oxidation of saturated aliphatic carboxylates is unexpected. Therefore, this work shows that the covalent grafting by oxidation of unsaturated carboxylates is favored for a parallel orientation of the radicals on the electrode surface, which is originated by the positive polarization of the electrode and the partially negative electronic density on the terminal unsaturated groups in the radical structure. This orientation is furthermore the result of a previous similar orientation of the unsaturated carboxylates, which is transitorily retained because of the very high rate of the decarboxylation step. Cyclic voltammetry experiments performed using different saturated and unsaturated alkyl-carboxylates, their respective carboxylic acids, as well as the use of ferrocene derivatives as redox probes were used to indirectly support the main conclusions given here

Annealing impact on emission and phase varying of Nd-doped Si-rich-HfO2 films prepared by RF magnetron sputtering

International audienceHfO2 films doped with Nd and Si atoms were produced by RF magnetron sputtering in argon plasma atmosphere. The effect of annealing treatment on the morphology, crystal structure and light emission of the films was investigated by means of the scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The thermal treatment was performed in the temperature range of TA = 800–1100 °C in horizontal furnace with continuous nitrogen flow. For annealed Si–HfO2:Nd films, the SEM study revealed the formation of the grains with the mean size of about 20–60 nm that show the tendency to enlarge with the TA rise. Besides, the phase separation was observed and tetragonal HfO2 and SiO2 phases were detected by the XRD method for the films annealed at TA > 950 °C. The PL study revealed that both Nd3+ ions and host defects contribute to PL emission whereas their relative contribution depends on the TA and on the crystal phase of host matrix. The highest PL intensity of Nd3+ ions via 4f inner electronic shell levels was detected for TA = 950 °C. The variation of PL intensity of Nd3+ ions was correlated with the change of PL intensity of the band caused by the host defects. These latter participate in the energy transfer towards Nd3+ ions. This statement was confirmed by XPS data, as well as by the shape of PL spectra. It was shown that the bright emission via Nd3+ ions can be achieved for those located in the tetragonal HfO2 matrix

Photocatalytic degradation of 2,4-dichlorophenol with MgAlTi mixed oxides catalysts obtained from layered double hydroxides

MgAl and MgAlTi mixed oxides were obtained from the thermal treatment of LDH materials synthesized by the sol-gel method; these materials were characterized by N2 physisorption, XRD, UV-vis, XPS, EDS-SEM and TEM techniques. According to the results, Ti was incorporated in the LDH layer when content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60min. According to the results, Ti was incorporated in the LDH layer when the content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP with the MgAl and MgAlTi mixed oxides, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60min. © 2013 Elsevier B.V

Photoluminescence of europium-activated hydroxyapatite nanoparticles in body fluids

MgAl and MgAlTi mixed oxides were obtained from the thermal treatment of LDH materials synthesized by the sol-gel method; these materials were characterized by N2 physisorption, XRD, UV-vis, XPS, EDS-SEM and TEM techniques. According to the results, Ti was incorporated in the LDH layer when content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60min. According to the results, Ti was incorporated in the LDH layer when the content in the material was low. The MgAl and MgAlTi mixed oxides were evaluated in the photo-degradation of 2,4-dichlorophenol (2,4-DCP) in the presence of UV light. A superior efficiency in the photo-degradation of 2,4-DCP with the MgAl and MgAlTi mixed oxides, in comparison with the Degussa P-25 TiO2 reference catalyst was observed, reaching a total decomposition of the 2,4-DCP molecule in less than 60min. " 2013 Elsevier B.V.",,,,,,"10.1016/j.jhazmat.2013.09.047",,,"http://hdl.handle.net/20.500.12104/43592","http://www.scopus.com/inward/record.url?eid=2-s2.0-84888202780&partnerID=40&md5=3c33781bca326f3d040824f9063ceb0a",,,,,,,,"Journal of Hazardous Materials",,"6

Sorption of Gold by Naked and Thiol-Capped Magnetite Nanoparticles: An XPS Approach

Iron oxide nanoparticles are promising materials for many technological and environmental applications due to their versatile functionalization and magnetic properties that allow a facile remote control, separation and analyte recovery. In this contribution, the results of gold­(III) sorption by naked and DMSA-capped (DMSA = m-2,3,dimercapto succinic acid) magnetite nanoparticles are discussed. Magnetite nanoparticles of 8 nm diameter were first synthesized by thermal decomposition of iron­(III) oleate followed by a ligand exchange reaction to substitute oleic acid (OA) molecules by DMSA. Such systems of coated magnetite nanoparticles were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and magnetic measurements. FT-IR spectroscopy suggests that in Fe₃O₄@DMSA the organic coating is not homogeneous and it interacts with surface iron cations either through the carboxylate groups (by forming bridging bidentate complexes) or through disulfide bonds after oxidation of thiol groups. The magnetic measurements show that the nanoparticles are in the superparamagnetic range at room temperature despite the presence of dipolar interactions. The gold­(III) adsorption isotherms for both bare Fe₃O₄ and Fe₃O₄@DMSA nanoparticles were fitted with the Langmuir and Freundlich models. The better fit for the second model suggests the heterogeneous nature of the surface and the multilayer nature of gold adsorption. XPS spectra reveal that the adsorption of Au­(III) ions comprises mostly its reduction to Au⁰ by disulfide groups, although there is a fraction of these gold ions that is reduced directly onto the bare surface of the iron oxide leading to Fe­(II) oxidation. According to the recorded optical absorption spectra, gold clusters of metallic character are also formed at the nanoparticle surface, a fraction of them forming subnanometer aggregates. The magnetic recovery of gold by this nanosystem could be extendable to other heavy metals

Pd and Pd@PdO core–shell nanoparticles supported on Vulcan carbon XC-72R: comparison of electroactivity for methanol electro-oxidation reaction

International audienceNanomaterials based on Pd nanoparticles supported on Vulcan carbon (XC-72R) were prepared by the organometallic approach in one-pot and mild conditions (3 bar hydrogen and room temperature) using Pd(dba)2 (bis (dibenzylideneacetone) palladium (0)) as metal source and hexadecylamine (HDA) as stabilizer. High-resolution transmission electron microscopy (HR-TEM) evidenced the presence of well-dispersed Pd nanoparticles of ca. 4.5 nm mean size onto the carbon support (Pd/HDA/C). Scanning and transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) allowed to determine the chemical composition of the nanomaterials. When the Pd/HDA/C nanomaterial was submitted to heating treatment (ht) at 400 °C under air (referred as Pd/HDA/C@air-ht), X-ray photoelectron spectroscopy (XPS) and HR-TEM/STEM-EELS analyses suggested the presence of interactions between PdO and Pd(0) as a result of the formation of Pd@PdO core–shell nanoparticles. The highest oxidation current magnitude during methanol oxidation reaction is ascribed to the heat-treated material, linked with a better electron and mass transfer processes at the electrode interface. This can be attributed to electronic interactions at the core–shell formed, which might promote different redox processes at the electrode interface during CH3OH deprotonation in the alkaline electrolyte