1,721,003 research outputs found
Synthesis, magnetic, spectroscopic and electrochemical studies of mixed pyrimidine-2-thiolate/triphenylphosphine rhenium(V) and rhenium(III) complexes
No full textEquimolar amounts of trans-[ReOX2(OEt)(PPh3)2] (XCl, Br, I) precursors and potentially bidentate N,S-donor pyrimidine-2(1H)-thione (pymSH) react in refluxing acetone to give mononuclear octahedral paramagnetic trans-[ReIIIX2(pymS)(PPh3)2](XCl, Br, I) species. Starting from a metal–ligand molar ratio of 1:3, in the presence of N(C2H5)3 as deprotonating agent inrefluxing ethanol, the same reaction proceeds stepwise, affording octahedral [ReO(pymS)3] or [ReO(pymS)3] and pentagonalbipyramidal[Re(pymS)3PPh3] complexes as a function of the reaction time. The compounds were characterized by elementalanalysis, magnetic susceptibility, UV–Vis–NIR, IR and 1H NMR spectroscopy and by cyclovoltammetric measurements.Reaction pathways and physico-chemical properties of the complexes are discussed
Mechanical activation of raw materials in the synthesis of Fe2O3-ZrSiO4 inclusion pigment
No full textThe traditional ceramic industry has recently witnessed increasing interest in the obtainment of inclusion pigments to stabilize at firing temperature and in the action of molten glass unstable chromospheres such as hematite or cadmium sulphoselenide.This work focuses in the introduction, before the calcination step, of a high energy milling step (mechanosynthesis) to improve the inclusionefficiency of hematite into the zircon matrix by solid state reaction. In particular the synthesis of hematite–zircon inclusion pigment was optimized through an accurate control of the raw material milling time and calcination temperature. The mechanical activation modifies the conditions in which chemical reactions usually take place changing the reactivity of as-milled solids by increase of reaction rates and lowering the reaction temperatures of ground powders
S-containing molecules films: characterization and use in direct electrochemistry of redox proteins
No full textThe S-containing molecules show a great affinity towards metal surfaces, particularly Au, Pt, Ag and Cu. The interaction of the metal with the solution of these molecules gives rise to the formation of an adsorbed self assembled monolayer (SAM). The preparation and structural characterization of monolayers assemblies supported on gold electrode are of great interest in the studi of the interfacial phenomena and in particular the direct electrochemistry of redox proteins
Synthesis, crystal and molecular structure, spectroscopic and electrochemical studies of trichloro-oxo(4,6-dimethypyrimidine-2(1H)-thione)(triphenylphosphine oxide) rhenium(V) complex.
No full textReaction of 4,6-dimethylpyrimidine-2(1H)-thione (Me2pymSH) with mer-[ReOCl3(Me2S)(OPPh3)] synthon in 1:1 molar ratio inrefluxing acetone, results in the replacement of the Me2S ligand to form the mer-[ReOCl3(Me2pymSH)(OPPh3)] species. X-raydiffraction shows that the structure of the title compound consists of monomeric units with a distorted octahedral coordinationaround the rhenium(V) centre which includes the axial ReO and ReOPPh3 bonds, and in which three Cl− ions and aS-monodentate neutral Me2pymSH ligand act as equatorial ligands. The compound was also characterised using electrochemicalmeasurements and UV–Vis–NIR and IR spectroscopy
Chemical-Physical characterization of the Au-C6H5SSCH3 SAM through the electrochemical study of the surface
No full textThe Au-C6H5SSCH3 SAM bahaviour has been studied through linear voltammetry
Redox thermodynamics of cytochrome c adsorbed on mercaptoundecanol monolayer electrodes
No full textThe redox potentials E-0 ́ of bovine cytochrome c adsorbed on an 11-mercapto-1-undecanol/Au self-assembled monolayer electrode were studied through direct electrochemistry as a function of the temperature in non-isothermal experiments carried out in the presence of different anions and changes of the ionic strength. The thermodynamic parameters for protein reduction (DeltaH(rc)(0 ́) and DeltaS(rc)(0 ́)) re were determined for adsorbed and solution cytochrome and the differences in E-0 ́ discussed in terms of the enthalpic and entropic contributions. The adsorption process seems to remove the ability of perchlorate anion to bind to the protein surface, while a certain direct interaction is still retained in the case of chloride and phosphate. A moderate increase in E-0 ́ of adsorbed cytochrome was measured at increasing ionic strength and discussed in the light of the opposite effect observed for solution protein
An efficent and fast analytical procedure for the bromine determination in waste electrical and electronic equipment plastics
No full textn this study, X-ray fluorescence (XRF) spectroscopy was used, in combination with micro-Raman spectroscopy, for a fast determination of bromine concentration and then of brominated flame retardants (BFRs) compounds in waste electrical and electronic equipments. Different samples from different recycling industries were characterized to evaluate the sorting performances of treatment companies. This investigation must be considered of prime research interest since the impact of BFRs on the environment and their potential risk on human health is an actual concern. Indeed, the new European Restriction of Hazardous Substances Directive (RoHS 2011/65/EU) demands that plastics with BFRs concentration above 0.1%, being potential health hazards, are identified and eliminated from the recycling process. Our results show the capability and the potential of Raman spectroscopy, together with XRF analysis, as effective tools for the rapid detection of BFRs in plastic materials. In particular, the use of these two techniques in combination can be considered as a promising method suitable for quality control applications in the recycling industry
Chromium electrodeposition from Cr(VI) low concentration solutions
No full textThis work presents a study of a hard chromiumplating process using low concentration H2CrO4 baths. Inparticular, the effect of different values of CrO3/H2SO4 ratioon coating properties such as adhesion, hardness, surfaceroughness, apparent density and microstructure were considered.To increase the solution conductivity, avoiding longdeposition times and low throwing power typical of dilutesolutions, the behaviour of various inorganic compoundswas investigated. Specifically, the compounds suitable forobtaining brighter coatings with lower surface roughnessvalues than those obtained using Fink’s solutions wereNa2SO4 and Al2(SO4)3 9 18H2O. A bath composition wasidentified, with a limited use of Cr(VI) in a solution able toproduce coatings with a better surface roughness than thoseof conventional industrial baths
Stabilization of bismuth ferrite suspensions in aqueous medium with sodium polyacrylate characterized by different molecular weights
No full textElectrostatic stabilization of bismuth ferrite BiFeO3 (BFO) single phase micronized particles suspended for the first time in aqueous medium, using sodium polyacrylate (Na-PAA) as suspending agent, was investigated to form homogeneous films through electrophoretic deposition technique. The dispersion efficiency was evaluated in terms of the zeta potential trend as a function of pH and sediment percentage, employing a fast and easy spectrophotometric method. All the tests were performed using three suspending agents characterized by the same polyacrylate functional group (-COONa) but with different molecular weights (Na-PAA Mw = 2100, 5100, and 20 000). The effect of BFO particles concentration (wt%), suspending agent concentration (wt%), suspending agent molecular weight and sonication time have been evaluated. The results showed that for all the experiments carried out the electrostatic stabilization of the BFO micronized particles in aqueous medium is accomplished in high basic pH range (8.5-9 or 9-11) depending on the molecular weight of the polyacrylate additive
Electrochemical behavior of diphenyl disulfide and thiophenol on glassy carbon and gold electrodes in aprotic media
No full textThe investigation of the electrochemical reduction processes of C6H5SSC6H5 and C6H5SH in CH3CN using cyclic voltammetry indicates a different behavior on GC and Au electrodes. On GC surface adsorption phenomena are absent, the electrochemical reduction process is irreversible and diffusion controlled. For both the starting molecules the same species, C6H5S-, is formed upon reduction. The Edegrees values of the reduction processes were determined by convolution method and the standard free energy of the S-S bond of C6H5SSC6H5 estimated. On Au surface instead, a self-assembled monolayer of C6H5SAuads originated after the S-S or S-H bond breaking can be observed by simply dipping the electrode in solution of C6H5SSC6H5 and C6H5SH, respectively. The properties of the SAM were investigated by electrochemical reduction of the adsorbed thiolates. On Au electrode the reduction processes involve C6H5SAuads, and give rise to desorbed C6H5S-. A neutral radical is obtained by. electrochemical oxidation of thiolate anion. It reacts rapidly with the electrode surface to give the S-Au bond again
- …
