292 research outputs found
Electrochemical polymerisation of phenol in aqueous solution on a Ta/PbO2 anode
No full textThis paper deals with the treatment of aqueous phenol solutions using an electrochemical technique. Phenol can be partly eliminated from aqueous solution by electrochemically initiated polymerisation. Galvanostatic electrolyses of phenol solutions at concentration up to 0.1 mol dm−3 were carried out on a Ta/PbO2 anode. The polymers formed are insoluble in acidic medium but soluble in alkaline. These polymers were filtered and then dissolved in aqueous solution of sodium hydroxide (1 mol dm−3). The polymers formed were quantified by total organic carbon (TOC) measurement. It was found that the conversion of phenol into polymers increases as a function of initial concentration, anodic current density, temperature, and solution pH. The percentage of phenol polymerised can reach 15%
Synthesis and structural studies of cyclopalladated complexes of secondary benzylamines
No full textDi-nuclear cyclopalladated acetato-bridged complexes derived from secondary benzylamines, [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-OAc)2] (R = Et (1), R = t-Bu (2)) were obtained by refluxing of corresponding benzylamines and Pd(OAc)2 in a 1:1 M ratio. Complex 1 was also prepared by heating the bis-amine complex [Pd(OAc)2(PhCH2NH(Et))2] (3) in toluene at 60 °C. Complex 3 reacted with an excess of NaCl to give [Pd(Cl)2(PhCH2NH(Et))2] (4). Metathetical reaction of 1 and 2 with an excess of NaCl or NaBr afforded the corresponding dimers [Pd2{(C,N)-C6H4CH2NH(R)}2(μ-X)2] (X = Cl, R = Et (5); X = Cl, R = t-Bu (6); X = Br, R = t-Bu (7)). The cationic complex [Pd(C,N)-C6H4CH2NH(Et)(phen)]BF4 (8) can be obtained by reacting chloro bridge dimer 5 with AgBF4 and 1,10-phenanthroline (phen). Neutral ligands split the halide bridges in 6 and 7 to give monomeric complexes [Pd(C,N)-C6H4CH2NH(t-Bu)X(L)] (X = Cl, L = PPh3 (9); X = Br, L = Me3Py (10)). Complexes 1–10 were fully characterized by elemental analysis, IR and NMR spectroscopies. In addition, the crystal structures of 2, 3, 4, 8, 9 and 10 were determined by single-crystal X-ray diffraction analysis. In all these structures, the palladium atom shows a distorted or slightly distorted square-planar geometry
Ground state structures of molecules prepared for phototautomerization: 2,2?-bipyridyl-3,3?-diol and 2,2?-bipyridyl-3-ol
No full textPartial in Situ Reduction of Copper(II) Resulting in One-Pot Formation of 2D Neutral and 3D Cationic Copper(I) Iodide-Pyrazine Coordination Polymers : Structure and Emissive Properties
No full textOn the way to copper(I) iodide coordination polymers with specific luminescent properties, the in situ reduction of Cu(II) in the presence of KI and bidentate N-heteroatomic ligand, either pyrazine (pyz) or 4,4'-bipyridine (bpy), resulted in one two-dimensional and two three-dimensional new coordination networks. Starting from Cu(NO3)2·3H2O in the presence of pyz, successive precipitation of known yellow [(Cu(I)I)2(pyz)]n, new orange [Cu(I)I(pyz)]n, and new dark blue [Cu(I)(pyz)2]·I5n polymeric solids was observed. Starting from the same salt in the presence of bpy resulted in the successive precipitation of known yellow [(Cu(I)I)2(bpy)]n and new brown [Cu(II)(NO3)(bpy)2]·I3·(dmf·H2O)n coordination polymers. By using either Cu(CH3COO)2·H2O or Cu(BF4)2 as starting materials, both known forms, yellow [(Cu(I)I)2(bpy)]n and orange [Cu(I)I(bpy)]n, precipitated successively. The new solids were characterized by IR spectroscopy and X-ray analysis. [Cu(I)I(pyz)]n represents the missing member in the row of two-dimensional coordination networks with general formula [Cu(I)X(pyz)]n (X = Cl, Br, I). Its steady state and time-resolved characterization together with DFT and TDDFT calculations revealed that the emission at room temperature is mainly delayed fluorescence originating from mixed singlet metal-to-ligand charge transfer and halide-to-ligand charge transfer states, while that at 77 K is phosphorescence, associated with the small singlet-triplet energy differences (ΔE = 70 meV)
Enhancement of cyclosporine aqueous solubility using alpha- and hydroxypropyl beta-cyclodextrin mixtures
No full textCyclodextrins (CDs) are cyclic oligosaccharides that form inclusion complexes with lipophilic molecules through their hydrophobic central cavity. In this study, the effect of alpha-CD, hydroxylpropyl-beta-CD (HP-beta-CD) and mixtures of these two CDs on the aqueous solubility of cyclosporine A (CyA) was investigated. Infrared spectroscopy and thermal analysis were used to confirm CyA-CD complex formation. CyA aqueous solubility was increased by 10 and 80 fold in the presence of alpha-CD and HP beta-CD, respectively. The phase-solubility profile for HP-beta-CD was linear while that for alpha-CD had positive deviation from linearity. In the presence of constant concentration of alpha-CD (15% w/v), aqueous solubility of CyA was further increased upon addition of HP-beta-CD up to a concentration of 20% w/v. At higher HP-beta-CD concentrations, aqueous solubility of CyA was observed to decrease. Addition of sodium acetate (up to 5% w/v) to aqueous solutions containing 20% w/v HP-beta-CD and increasing concentrations of alpha-CD resulted in a significant reduction in CyA solubility. Complex formation between CyA and both alpha-CD and HP-beta-CD was confirmed by differential scanning calorimetry (DSC). No significant changes were observed in the IR spectra of either CyA or CD following complex formation suggesting chemical interaction between CyA and the CD was unlikely. Phase-solubility studies showed that alpha-CD had a much greater effect on the solubility of CyA than HP-beta-CD. Addition of HP-beta-CD to aqueous solutions of alpha-CD affected the solubility of CyA in these systems. A mixture of 15% w/v alpha-CD and 20% w/v HP-beta-CD was optimal for increasing aqueous solubility of CyA
Ionic and molecular adsorption at the single crystal surfaces of platinum and gold
No full textElectrochemical, thermodynamic and spectroscopic techniques were employed to investigate the adsorption of anions at the Pt(111) surface and the adsorption of a neutral molecule on the Au(110) surface. This thesis consists of three subprojects. First, chronocoulometry was used to describe chloride adsorption at the Pt(111) surface. Chloride forms a chemisorption bond with platinum. The charge numbers at constant potential and at constant chloride concentration are close to unity. The highest packing density of chloride determined corresponds to 0.43 of a monolayer. At negative potentials, co-adsorption of C1 and hydrogen atoms has a synergistic character. The adsorption of chloride and OH - at positive potentials has a competitive nature. Second, the origins of the anomalous wave known as the "butterfly peak" in the cyclic voltammogram of Pt(111) in sulfuric acid solutions, were investigated with 'in situ' FTIR spectroscopy. The results indicated that depending on the potential and pH, both sulfate and bisulfate could be the predominant adsorbing species. The pKa values for adsorbed bisulfate range between 4.1 and 4.6. On the Pt(111) surface, adsorption of bisulfate is more favorable than adsorption of sulfate. The anomalous "butterfly peak" is caused predominantly by the adsorption of bisulfate. The characteristic butterfly shape of the peak is caused by the phase transition between the disordered and ordered bisulfate adsorbate. Finally, the 'in situ' FTIR technique was employed to investigate the adsorption of pyridine on the Au(110) surface. The FTIR data provided direct spectroscopic proof that pyridine molecules adsorb vertically with the nitrogen atom directed toward the Au(110) surface in the whole range of potentials studied. The rigidity of the film is strongly affected by the field at the metal-solution interface. At small electric fields, the adsorbed molecules display a significant waving motion. When the field increases, the motion of the molecules decreases as a result of the dielectric saturation phenomenon. In the presence of large electric fields, the adsorbed molecules are effectively immobilized and the monolayer may be considered as "frozen"
Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy Characterization of Oxide Ores during Thiosulfate Mediated Gold Leaching
No full textThis is the pre-peer reviewed version of the following article: Scott R. Smith, Janet Y. Baron, Yeonuk Choi, Jacek Lipkowski. Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy Characterization of Oxide Ores during Thiosulfate Mediated Gold Leaching. Journal of Raman Spectroscopy, 2017,48,197-203., which has been published in final form at https://doi.org/10.1002/jrs.5011. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions."An applied approach for in situ characterization of oxide ore samples exposed to a thiosulfate-based leaching solution with shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) is discussed. Differences in passive layer growth during thiosulfate leaching were observed in the SHINERS spectra between the untreated and pressure oxidation (POX)-treated oxide ore samples received from Barrick Gold Corporation. The SHINERS spectra revealed that the passive layer at the untreated oxide ore–electrolyte interface contains metal sulfides and significant quantities of polysulfide chains urn:x-wiley:03770486:media:jrs5011:jrs5011-math-0001 of variable lengths after longer exposure to the leaching solution. However, the passive layer observed with the POX-treated sample was found to be predominantly metal sulfides with only a small quantity of polysulfide chains. From these results, it was concluded that the POX pretreatment process may successfully destroy or inactivate minerals found in the ore that are responsible for catalysing thiosulfate decomposition into polysulfides which results in low gold extraction efficiencies.Barrick Gold CorporationNatural Sciences and Engineering Research Council of Canad
Development and characterization of the scaffolded vesicle as a potential nutraceutical carrier
No full textA recently proposed scaffolded vesicle carrier system, in which a phospholipid membrane is supported by a hydrogel core, may be considered as a future technology in nutraceutical transport. The usage of a hydrogel provides a relatively macroscopic system that can potentially carry a much larger dose than current technologies. Refinements in the preparation method were evaluated by monitoring Tb3+ efflux from the scaffolded vesicle in order to determine the relative permeability of the system. Amplified fluorescence from the TbDPA33- complex was monitored over time and evaluated with a first order kinetics model. Furthermore, the percent coverage of the hydrogel by the lipid coating was calculated from the efflux results. A lipid coating containing DPhPC was observed to provide the most impermeable scaffolded vesicles compared to other coating compositions. Furthermore, the permeability profile obtained at varying temperatures demonstrated that the structure of the coating was similar to that of lipid vesicles
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