Search results for "voltammetry"
showing 10 items of 404 documents
Quantitation of Metal Ions in Archaeological Glass by Abrasive Stripping Square-Wave Voltammetry Using Graphite/Polyester Composite Electrodes
2003
A method for identifying Co, Cu, Sb, Sn, Fe, Zn, and Zr pigments in glasses using square-wave voltammetry as the detection mode is described. It is based on the abrasive attachment of glass microsamples to graphite/polyester composite electrodes. Sample amounts less than 1 μg are used allowing for the study of archaeological samples. In all cases well-defined anodic stripping peaks corresponding to the oxidation of metal deposits generated at potentials ranging from −0.6 to −1.6 V (vs. SCE) are obtained. This response is in agreement with that displayed by the corresponding metal oxides. Quantitative estimates of the relative population of metal ions in glasses are obtained from peak area m…
Synthesis of phosphine derivatives of [Fe2(CO)6(μ-sdt)] (sdt = SCH2SCH2S) and investigation of their proton reduction capabilities
2023
The reactions of [Fe2(CO)6(μ-sdt)] (1) (sdt = SCH2SCH2S) with phosphine ligands have been investigated. Treatment of 1 with dppm (bis(diphenylphosphino)methane) or dcpm (bis(dicyclohexylphosphino)methane) affords the diphosphine-bridged products [Fe2(CO)4(μ-sdt)(μ-dppm)] (2) and [Fe2(CO)4(μ-sdt)(μ-dcpm)] (3), respectively. The complex [Fe2(CO)4(μ-sdt)(κ2-dppv)] (4) with a chelating diphosphine was obtained by reacting 1 with dppv (cis-1,2-bis(diphenylphosphino)ethene). Reaction of 1 with dppe (1,2-bis(diphenylphosphino)ethane) produces [{Fe2(CO)4(μ-sdt)}2(μ-κ1-dppe)] (5) in which the diphosphine forms an intermolecular bridge between two diiron cluster fragments. Three products were obtaine…
Physical chemical properties and kinetics of redox processes in water/soybean oil microemulsions
2008
Microemulsoes de agua em oleo (ME w/o) constituidas de agua, oleo de soja, SDS (dodecil sulfato de sodio) e diversos alcoois de cadeia curta foram caracterizadas sob o ponto de vista fisico-quimico e de propriedades eletroanaliticas. Foram testados diferentes co-surfactantes e razoes surfactante:cosurfactante, sendo a ME com a composicao mais favoravel utilizada para estudar a cinetica de processos redox. Para tanto, realizaram-se medidas de voltametria ciclica utilizando como eletrodo de trabalho um ultramicroeletrodo de disco de Pt e, como eletrodo de referencia e auxiliar, foram usados Ag/AgCl e Pt, respectivamente, e ferroceno como uma sonda. Verificou-se que a estabilidade termodinâmic…
Adsorption of gelatin during electrodeposition of copper and tin-copper alloys from acid sulfate electrolyte
2014
International audience; An acid Cu–Sn deposition bath was developed, and copper and copper–tin coatings were electrodeposited on polycrystalline platinum. The effect of gelatin on copper and copper–tin electrodeposition from acid sulfate solutions has been investigated by a variety of electrochemical methods (voltammetric studies and electrochemical quartz crystal microbalance) as well as by morphologic technique (scanning electron microscopy). The electrochemical results have shown that the overpotential is required when gelatin is added, indicating the presence of interaction between the additive and the coating. From the results of X-ray photoelectron spectroscopy, PM-IRRAS and cyclic vo…
On the physicochemical properties of pyridohelicenes.
2014
A comprehensive study on the physicochemical properties of a series of mono- and diaza[5]helicenes as well as mono- and diaza[6]helicenes is reported. Through the use of both computational and experimental methods, these helically chiral pyridohelicenes with the nitrogen atom(s) in various positions are characterised according to their inversion barriers, protonation constants and redox potentials. By using DFT calculations, kinetic measurements, UV/Vis titrations, cyclic voltammetry and EPR spectroscopy, a self-contained picture of their behaviour under conventional treatment by heat, acids and oxidising/reducing agents is provided.
Electrochemical characterization of cobalt cordierites attached to paraffin-impregnated graphite electrodes
2004
The electrochemistry of α, β and μ cobalt-containing cordierites (Co2Al4Si5O18) attached to paraffin-impregnated graphite electrodes has been studied by linear scan and cyclic voltammetries in HCl+NaCl and NaOH electrolytes. This electrochemistry is compared with that of vitreous cobalt cordierite, cobalt(II) oxide and cobalt spinel aluminate (CoAl2O4), the two last taken as reference materials. Electrochemical processes involve the site-characteristic reduction of Co(II) species to cobalt metal near to −0.5 V vs. SCE and their oxidative dissolution near +0.3 V, accompanied by solid state interconversion between Co(II) and Co(III) at potentials above +0.45 V. Cordierite-modified electrodes …
Synthesis, Characterization, and Cu(2+) Coordination Studies of a 3-Hydroxy-4-pyridinone Aza Scorpiand Derivative.
2016
The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows …
Investigation of Activities for Pt-M Bimetallic Nanoparticles Catalysts on the Oxygen Reduction Reaction
2015
Bi-metallic Pt3Ni/C and Pt3Co/C electrocatalysts were successfully synthesized by a solvent free chemical vapour deposition method with a narrow particle size distribution. The results showed that the electrochemical surface area was increased by adding the additional Ni or Co to a pure Pt catalyst. Pt3Ni/C catalyst exhibited a significant enhancement of oxygen reduction reaction activity. The catalysts were characterized by EDS, XRD, HRTEM and electrochemical activity was determined using cyclic voltammetry.
Determination of the Boron/Lead Ratio in Ceramic Materials Based on Electrochemical Quartz Crystal Microbalance
2004
A method for quantitatively determining the relationship boron/lead in ceramic materials is presented. It is based on the attachment of microsamples of ceramic frits to an electrochemical quartz crystal microbalance (EQCM). After a reductive deposition step in the � 0.25 to � 0.85 V (vs. AgCl/Ag) potential range, well-defined stripping peaks are recorded in 0.10 M NaCl plus 0.10 M mannitol. The deposition of boron and lead from suspensions of solid materials, and its subsequent oxidative dissolution can be monitorized at the EQCM. The quotient between the maximum mass gain and the corresponding charge passed enables for a direct quantitation of the boron/lead molar ratio in ceramic material…
Determination of toxic elements by cathodic-stripping-voltammetry
1981
The DPCSV determination of arsenic, selenium and tellurium in the sub-ng/ml range is discussed. After electrolytic deposition of the elements as intermetallic compounds with copper on the electrode surface, the determination is carried out by cathodic stripping. The simultaneous determination of selenium and tellurium or of selenium and arsenic is possible. Problems which occur in the application of these methods are discussed.