2018
Permanent URI for this collectionhttps://hdl.handle.net/1807/81041
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Item Open Access Thermodynamic analysis of the copper (I) homogeneous and heterogeneous speciation in ammonium thiosulfate leaching systems(Canadian Science Publishing, 2018-12-13) Povar, Igor; Ubaldini, Stefano; Spinu, Oxana; Lupascu, TudorThe paper presents a new thermodynamic approach to studying mixed ligand complex formation reactions in the multicomponent two-phase system â cuprous oxide - ammoniacal copper (I) thiosulfate aqueous solutionâ under real conditions. The quintessence of developed approach consists in the thermodynamic analysis of concurrent reactions in the heterogeneous system Cu(I) - NH3 â S2O32- - H2O on the basis of the introduced notion of generalized reaction equations. A detailed thermodynamic analysis in ammonium thiosulfate leaching systems has considered the formation of mixed ligand complex species . The new feature is to focus on the chemical description of the overall process of complex formation consisting of a series of concurrent reactions, where the nature and ratio of the concentrations of chemical species, formed in such reactions, depend on the ratio of the concentrations of the metal Cu+ and ligands, temperature and other thermodynamic parameters. On the basis of the selected thermodynamic data for involved species, the thermodynamic stability areas of solid phase as well as the repartition of soluble and insoluble chemical species towards the solution pH and a number of total reagent concentrations in heterogeneous mixtures have been investigated. The diagrams of heterogeneous and homogeneous chemical equilibria are used for the graphical representation of complex equilibria and distribution of soluble and insoluble species in examined systems. The used approach utilizes thermodynamic relationships coupled with original mass balance constraints, where the solid phases are explicitly expressed. The obtained results are useful for optimization of the overall scheme of thiosulfate leaching in gold hydrometallurgy in order to minimize reagent consumption and maximize gold extraction.Item Open Access Personal Reflections on Fifty Years of Funding Via the Canadian Academic Research Grant System(Canadian Science Publishing, 2018-08-30) Steer, Ronald RPS2019 marks the fiftieth anniversary of the authorâ s first application for federal grant funds to support his independent academic research program at the University of Saskatchewan. Scientific and funding milestones are highlighted; a few personal observations are included.Item Open Access Polybenzimidazole/ BaCe0.85Y0.15O3-δ nanocomposites with enhanced proton conductivity for high temperature PEMFC application(Canadian Science Publishing, 2018-10-16) Salehi Artimani, Javad; Ardjmand, Mehdi; Enhessari, Morteza; Javanbakht, MehranThe present work reports the synthesis of polybenzimidazole ﴾PBI) / BaCe0.85Y0.15O3-δ nanocomposite membrane. The obtained membranes were investigated to use as novel electrolytes in high temperature proton exchange fuel cells. The PBCYx membranes were prepared with dispersing BaCe0.85Y0.15O3-δ into the polyimidazole membrane by solution casting method. The obtained membranes were used as novel proton conductors. The thermal stability and structural properties were investigated. The conductivity and morphology of the obtained materials were studied using impedance spectroscopy AC ﴾IS) and scanning electron microscope ﴾SEM) equipped with energy dispersive X-ray spectroscopy ﴾EDX). The maximum phosphoric acid adsorption ﴾175%) and protonic conductivity ﴾ 0.092 S/cm at 180 ̊C in dry condition) were observed for all of the PBI nanocomposite membranes containing 5 wt.% of BaCe0.85Y0.15O3-δ in the membrane matrix. The polarization and power density curves were studied at 150 and 180 ̊C operation temperature. The power density of about 0.42 W/cm2 and current density of about 0.84 A/cm at 0.5 V and 180 ̊C were achieved in dry condition. The data obtained from our studies showed that the physicochemical properties of the novel nanocomposites were enhanced for using in the high temperature proton transfer fuel cells.Item Open Access Rhodium-Catalyzed Regioselective Ortho-Allylation of 2,4-Diarylquinazolines with Allylic Acetate(Canadian Science Publishing, 2018-10-25) Gao, Wei; Yu, Dongbo; Liu, Deming; Xu, Linchu; Ding, Qiuping; Peng, YiyuanIn this paper, a rhodium-catalyzed high regioselective reaction of 2,4-diarylquinazolines with allylic acetate is described, leading to allylated quinazoline derivatives with high efficiency and good tolerance of functional groups. By switching to 2-arylquinazolin-4-ones, tandem C-H activation and aza-Michael addition are involved, leading to 1,6-dimethyl-5H-isoquinolino[1,2-b]quinazolin-8(6H)-one derivatives with high efficiency.Item Open Access Molecular dynamics simulation on the morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) affected by dimethyl sulfoxide (DMSO) and temperature(Canadian Science Publishing, 2018-12-10) Lan, Guachao; Jin, Shaohua; Li, Jing; Lu, Zhiyan; Ruan, Jian; Chen, Minglei; Li, LijieAttachment energy (AE) model is adopted to research the influence of dimethyl sulfoxide (DMSO) and temperature on the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7). FOX-7 crystal habits in DMSO at different temperatures simulated by AE model have apparently changed compared with the vacuum morphology, indicating that the solvent and temperature can affect FOX-7 morphology. Moreover, the influence of model dimension on the attachment energy has been studied, and a reasonable model size is obtained based on the model dimension study results. Besides, the radial distribution function analysis shows that the solvent molecules adsorb on the FOX-7 surfaces mainly via the solvent-crystal interface interactions of van der Waals forces (vdW) and Coulomb interactions. The analysis of diffusion coefficient of DMSO molecules on the crystal growth surfaces shows that the growth habit is also influenced by the diffusion capacity of DMSO molecules. These simulation results of this study can provide some guidance for the crystallization process of FOX-7.Item Open Access Simultaneous determination of three sulfanilamide artificial sweeteners in foodstuffs by capillary electrophoesis coupled with contactless conductivity detection based on porous aromatic frameworks enhanced solid phase extraction(Canadian Science Publishing, 2018-10-24) Xia, Shaige; Yin, Dan; Chen, Yanlong; Yang, Zhicong; Miao, Ying; Zhang, Wenfen; Chen, Sheng; Zhao, Wuduo; Zhang, ShushengIn this paper, a simple and easy-operating method of solid phase extraction (SPE) followed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) is evaluated as a novel approach for the simultaneously determination of acesulfame-K (ACE), sodium saccharin (SAC) and sodium cyclamate (CYC) in foodstuffs without derivatization. In order to reduce the complex matrix interference resulting from the constituents of samples and enrich targets, porous aromatic frameworks (PAFs) enhanced SPE, a suitable sample pretreatment procedure was introduced. Several factors affecting extraction efficiency and electrophoretic separation were investigated. Additionally, The interaction mechanisms of host (PAF–6)–guests (ACE/SAC/CYC) were further studied. Under the optimum conditions, three sulfanilamide artificial sweeteners were baseline separated within 8 min, exhibiting a linear calibration over three orders of magnitude (R2>0.995); The limits of detection (LOD) and quantification (LOQ) were considered better than those usually obtained by CE with UV and C4D detection. The proposed SPE–CE–C4D method has been successfully applied to analyse beverage samples and candied fruits with recoveries in the range of 78.89–92.00%.Item Open Access Oxidative Ring-Opening of Benzothiazole Derivatives(Canadian Science Publishing, 2018-12-14) Moreira, Ryan; Sinclair, Geoffrey S.; Schipper, DerekAn oxidative ring opening of benzothiazole to an acylamidobenzene sulfonic ester using alcohol solvents and magnesium monoperxoyphthalate hexahydrate has been described. Under the established conditions, the reaction produces synthetically significant yields with a variety of benzothiazole derivatives. A sulfinic ester intermediate suggests that the reaction proceeds via thiazole ring opening followed by thiol oxidation.Item Open Access Novel chiral proline-based organocatalysts with amide and thiourea-amine units for highly efficient asymmetric aldol reaction in saturated brine without additives(Canadian Science Publishing, 2018-12-31) Xu, Enjie; Song, Yan; Wei, Zhonglin; Wang, Rui; Duan, Haifeng; Lin, Yingjie; Yang, Qingbiao; Li, YaoxianA series of novel proline-based organocatalysts with amide and thiourea-amine units (7a-f) were developed and evaluated in the asymmetric aldol reaction of 4-nitrobenzaldehyde with cyclohexanone. The organocatalyst 7c or 7d of 5 mol% exhibited efficient catalytic activity to afford aldol products in high diastereoselectivity (up to >99:1), enantioselectivity (up to >99%), and yield (up to >96%) at 0°C in saturated brine without adding an acid. Worth to mention that aldol products of benzaldehyde derivatives almost universally provided high diastereoselectivity and enantioselectivity.Item Open Access Formation and Application of Electrochemically Active Cross-Linked Triarylamine-Siloxane Films Using the Piers-Rubinsztajn Reaction.(Canadian Science Publishing, 2018-08-25) Kamino, Brett; Szawiola, Anjuli; Plint, Trevor; Bender, TimCross-linked triarylamine-siloxane hybrid thin film have been formed using Piers-Rubinsztajn chemistry. Key to this approach was the use of a ring-opening reaction to prevent the evolution of volatile small molecules. A representative cyclic ether containing biphenyl triarylamine compound was synthesized and upon ring-opening was shown to form a smooth, glassy and electroactive films by cross-linking with tetrakis(dimethylsiloxy)silane (QM*4). It was found that the films were electrochemically active with low glass transition temperatures. Cross-linked films were incorporated into organic light emitting diodes (OLEDs) under various conditions, a functionality within OLEDs was confirmed. Finally, the resistance of the system to dissolution (orthogonality) was considered by casting F8T2, a p-type emitting polymer, from solution on top of the cross-linked film which formed a working OLED. Un film mince hybride de triarylamine-siloxane réticulé a été formé en utilisant la chimie de Piers-Rubinsztajn. La clé de cette approche était l'utilisation d'une réaction d'ouverture de cycle pour empêcher l'évolution de petites molécules volatiles. Un éther cyclique représentatif contenant un composé de biphényl triarylamine a été synthétisé et lors de l'ouverture du cycle, il s'est avéré former des films lisses, vitreux et électroactifs par reticulation avec du tétrakis (diméthylsiloxy) silane (QM * 4). Il a été trouvé que les films étaient électrochimiquement actifs avec de basses températures de transition vitreuse. Des films réticulés ont été incorporés dans des diodes électroluminescentes organiques (OLED) dans diverses conditions, une fonctionnalité au sein des OLED a été confirmée. Enfin, la résistance du système à la dissolution (orthogonalité) a été prise en compte par la coulée de F8T2, un polymère émetteur de type p, à partir d'une solution sur le film réticulé qui formait un OLED actifItem Open Access Canada’s Early contributions to Plasmonics(Canadian Science Publishing, 2018-11-22) Moskovits, MartinThe field of plasmonics -- the study of collective electrons excitation in nanostructured metal and other conductors -- is currently highly active with research foci in a number of related fields including plasmon-enhanced spectroscopies, and plasmon-mediated photochemical and photocatalytic processes through which the energy stored temporarily as plasmons can be used to enable and/or accelerate photochemistry. This enhancement is accomplished either by the action of the large optical fields produced in the vicinity of plasmonic nanostructures, or mediated by the energetic electrons and holes surviving transiently following the dephasing of the plasmon. This article traces the early contributions to the foundation of the current field of plasmonics by two scientists working in Canada in the early 1970â s: J. P. Marton at McMaster University, and Welwyn Corporation; and the current author while he was at the University of Toronto.Item Open Access Elucidation of the Mechanism and Energy Barrier for Anesthetic Triggered Membrane Fusion in Model Membranes(Canadian Science Publishing, 2018-12-29) Nguyen, Trinh; Cramb, DavidMembrane fusion a vital for cellular function and is generally mediated via fusogenic proteins and peptides. The mechanistic details and subsequently the transition state dynamics of membrane fusion will be dependent on the type of the fusogenic agent. We have previously established the potential of general anesthetics as a new class of fusion triggering agents in model membranes. We employed two-photon excitation fluorescence cross-correlation spectroscopy (TPE-FCCS) to report on vesicle association kinetics and steady-state fluorescence dequenching assays to monitor lipid mixing kinetics. Utilizing halothane to trigger fusion in 110 nm diameter dioleoylphosphatidylcholine (DOPC) liposomes, we found that lipid rearrangement towards the formation of the fusion stalk was rate limiting. The activation barrier for halothane induced membrane fusion in 110 nm vesicles was found to be ~40 kJmol-1. We calculated the enthalpy and entropy of the transition state to be ~40 kJmol-1 and ~180 Jmol-1K-1, respectively. We have found that the addition of halothane effectively lowers the energy barrier for membrane fusion in less curved vesicles largely due to entropic advantages.Item Open Access Assessment of boron nitride nanotube materials using X-ray photoelectron spectroscopy(Canadian Science Publishing, 2018-12-18) Jakubinek, Michael; Kim, Keun Su; Homenick, Christa; Kodra, Oltion; Walker, Steven; Simard, BenoitWith increasing prevalence of boron nitride nanotubes (BNNTs) the need for routine and reliable assessment methods is becoming more critical both for research studies and for quality-control in nanotube manufacturing. The assessment of BNNT materials using X-ray photoelectron spectroscopy (XPS) is described here through analysis of raw-BNNT materials and three case studies showing modification of BNNTs by purification or chemical functionalization. Metrics indicative of the BN content of the material, with the simplest being the B:N ratio, are described and tracked to show evolution of BNNT materials during processing. Along with changes in the elemental composition and the content of BN, high-resolution spectra of the B 1s region also show clear evolution as BNNT materials are modified, which can be used as a measure of boron nitride content/quality to assess BNNT production, purification and functionalization.Item Open Access Identifying absolute configurations of PCB atropisomers by comparison of their experimental specific rotations with their DFT calculated values(Canadian Science Publishing, 2018-12-15) Daramola, Oluwadamilola; Cullen, John McKayNineteen enantiomer pairs of polychlorinated biphenyls (PCBâ s) with three or four chloro substituents about the central carbon-carbon bond form a stable subclass of compounds whose biological effects vary with their chirality. Optical rotations for this group of PCBâ s were determined from density functional calculations employing extended atomic orbital gauge invariant basis sets. A comparison of these results with the experimental ones found from the literature for nine of the pairs enabled the identification of their absolute configurations as analytes in gas chromatography studies.Item Open Access Microfluidic Encapsulation of SN-38 in Block Copolymer Nanoparticles: Effect of Hydrophobic Block Composition on Loading and Release Properties(Canadian Science Publishing, 2018-11-18) Jensen, Danica; Cao, Yimeng; Lu, Changhai; Wulff, Jeremy E.; Moffitt, MatthewA gas-liquid microfluidic reactor was used to prepare polymer nanoparticles (PNPs) containing the drug 7-ethyl-10-hydroxy camptothecin (SN-38) from a series of poly(methyl caprolactone-co-caprolactone)-b-poly(ethylene oxide) (P(MCL-co-CL)-b-PEO) amphiphilic block copolymers with variable MCL content in the hydrophobic block. All three copolymers formed spheres with ~20-nm core diameters by TEM although some rigid rodlike aggregates were also formed by the PMCL-50 and PMCL-75 copolymers. SN-38 encapsulation efficiencies (EE = 2.7-3.0%) and loading levels (DL = 2.0-2.9%) were similar for the three copolymers. In vitro release kinetics became significantly slower as the MCL content increased, with release half times increasing monotonically from 3.4 to 6.2 h as the MCL content of the hydrophobic block increased from 50% to 100%. The ability to systematically tune release half times via controlled variation in the hydrophobic block composition, while maintaining constant PNP size and loading levels, represents an intriguing chemical handle for the optimization of SN-38 nanomedicines.Item Open Access Ruthenium-Catalyzed Ring-Opening Reaction of a 3-Aza-2-oxabicyclo[2.2.1]hept-5-ene with Amines(Canadian Science Publishing, 2018-12-28) Tait, Katrina; Koh, Samuel; Blanchard, Nicolas; Tam, WilliamThe ruthenium-catalyzed ring-opening reaction of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with amines was investigated. In the presence of an amine and a ruthenium catalyst, the N-O bond is cleaved, forming a ring-opened allylic alcohol product. Through a possible ruthenium-catalyzed redox isomerization, the allylic alcohol is transformed into a saturated carbonyl product. This unexpected mode of ruthenium-catalyzed ring-opening reaction of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene leads to the formation of a cyclopentanone derivative in moderate yields.Item Open Access The effect of phenolic compounds on salicylaldimine nickel-catalyzed ethylene oligomerization(Canadian Science Publishing, 2018-11-29) Wang, Jun; Xie, Junyi; Wang, Libo; Jiang, Yan; Zhang, NaAbstract A salen nickel complex has been prepared in good yield with ethylenediamine, salicylaldehyde and NiCl2¡6H2O as raw materials. The structure of complex was characterized by FT-IR, 1H NMR, UV, and ESI-MS. Upon activation with methylaluminoxane (MAO), the precatalyst showed high activity for ethylene oligomerization. In order to reduce the simultaneous production of insoluble polymers during the nickel-catalyzed ethylene oligomerization, a series of phenolic compounds were introduced as modifiers for the production of linear Îą-olefins. The researched result showed that the phenolic compounds have a significant impact on the selectivity of oligomers and the concentration of polymers. With the increase of phenolic compounds, the content of polymers decreased and the distribution of oligomers was gradually shifted toward lighter olefins. Especially, sterically hindered 4-tert-butyphenol was proved to be an efficient polymer-retarding modifier among the studied phenolic compounds in this work. Furthermore, the retarding effect of phenolic compounds toward insoluble polymers may be mainly related to their interaction with MAO, giving rise to larger MAO aggregates.Item Open Access Response surface methodological optimization of batch Cu(II) sorption onto succinic acid functionalized SiO2 nanoparticles(Canadian Science Publishing, 2018-11-24) Yakout, Amr A; Shaker, Medhat A; Elwakeel, Khalid Z.; Alshitari, WaelFunctionalizing nanosilica (n-SiO2) particles with suitable active organic moiety leads to the formation of surfaces with precisely controlled physical and chemical characteristics. In this work, a novel nanosorbent (31±2.4 nm) namely succinic acid functionalized nanosilica (n-SiO2@SA) was synthesized via a simple protocol using microwave irradiation to remove Cu(II) ions from aqueous media. The successful functionalization of n-SiO2 was confirmed by FTIR while the thermal stability of n-SiO2@SA is investigated by TGA study. Other techniques including, HRTEM, DLS and zeta-potential were utilized to investigate the chemical, surface and morphological properties of the fabricated n-SiO2@SA. The response surface methodology (RSM) combined with 3-level, 3-factorial Box–Behnken design (BBD) were applied to optimize the multivariable sorption system using data obtained from 17 batch runs to reach 98.9% of Cu(II) ion removal. The predicted optimal conditions were: contact time = 30 min, pH = 7.1, initial Cu(II) concentration = 317.5 mg L−1 and sorbent dose = 15 mg at which the maximum sorption capacities for n-SiO2 and n-SiO2@SA were 209.3 and 386.4 mg g−1, respectively at 25 oC supporting the validity of functionalization process. Non-linear regression and linear least-squares methods confirm the suitability of Langmuir model to describe the experimental endothermic, feasible and chemisorption data, while the normalized standard deviation Δq% recommends the pseudo second-order kinetic model to represent the kinetic data. Real Cu-contaminated wastewaters were used to examine n-SiO2@SA nanosorbent for removing Cu(II) ions.Item Open Access Theoretical Study on Polyglycerine Polynitrates for Potential High Energy Plasticizers of Propellants(Canadian Science Publishing, 2018-11-14) Wang, Guixiang; Xu, Yimin; Zhang, Wenjing; Xue, Chuang; Gong, XuedongPolyglycerine polynitrates, such as NG (Nitroglycerine) can be used as energetic plasticizers of propellants. In this study, 29 derivatives of NG are investigated at the B3LYP/6-31G* level of the density functional theory. The corrected theoretical densities (ρ’exps) are predicted and are found to be very close to the experimental values. Detonation properties are calculated using the modified Kamlet-Jacobs equations and the specific impulse (Is) is evaluated according to the maxmium exothermic principle. A new parameter K, which is the product of Is and ρ’exp is proposed to evaluate the overall energetic characteristics of compounds. Thermal stability is discussed by calculating the bond dissociation energies (BDEs) or bond dissociation energy barriers (BDEBs). The O−NO2 bond has the smallest BDE and is the trigger bond for each of the studied compounds. The influence of the −ONO2 and −CH2−O−CH2−CH(ONO2)− groups, which is useful for design of new high energy plasticizers has also been discussed. Comprehensively considering the energetic properties and the stability, DGPN, DGHN, TriGHeptaN, TriGON, TriGNN, TetraGNN, TetraGDeN, TetraGUN and TetraGDoN are possibly better energetic plasticizers of solid propellants than NG.Item Open Access The microstructure and optical property of Na-doped ZnO system by sol-gel method(Canadian Science Publishing, 2018-10-09) Tong, Fan; Zhao, Ye; Wang, Hua MaoPure and Na-doped ZnO (2 at.%, 5 at.% and 10 at.%) films are synthesized by sol-gel method and annealed at 500 °C for 4 h. The as-synthesized nanoparticles are characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). The samples exhibited hexagonal ZnO lattice structure and another Na2O2 phase was detected in the 5 at.% Na-doped ZnO sample. The calculated average crystalline size increases from 42.0 nm to 43.5 nm when Na content increased from 0 to 10 at.%. FESEM and TEM analysis identifies that the average size of the Na-doped ZnO nanoparticles lies in between 50 nm and they appear in spheroid-like or rod-like shape. The transmittance of the sample was above 80% and the results of photocatalytic activity show that Na-doped ZnO nanoparticles exhibit higher photodegradation activity (about 91%) than pure ZnO nanoparticles under UV irradiation.Item Open Access A Spectroscopic Study of a Cyclodextrin-Based Polymer and the “Molecular Accordion” Effect(Canadian Science Publishing, 2018-11-25) Karoyo, Abdalla H; Wilson, Lee DThe formation of host-guest complexes was studied for two hosts; β-cyclodextrin (β-CD) and a cross-linked polymer containing an equimolar ratio of β-CD and hexamethylene diisocyanate (HDI), denoted as HDI-1. The thermodynamics of host-guest binding was studied with 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) using steady-state fluorescence spectroscopy in aqueous solution at variable temperature and ambient pH. The association of 1,8-ANS with β-CD and HDI-1, showed a fluorescence enhancement of ~4 and 12 units, respectively. Greater fluorescence enhancement for the polymer/dye system indicates the presence of multiple binding sites (inclusion vs. interstitial). By contrast, the β-CD/dye system adopt trends that indicate the formation of well-defined inclusion complexes. HDI-1 has inclusion sites (β-CD) and interstitial domains (HDI) that afford dual binding with variable binding affinity. Simplified binding models employed herein address the role of inclusion binding without an explicit account for higher order or secondary binding equilibria. The approximate 1:1 binding constant (K1:1) for CD/1,8-ANS is about two-fold greater over the HDI-1/1,8-ANS system, where HDI-1 displays cooperative effects among the polymer subunits, according to changes in relative fluorescence intensity related to structural transitions and binding site loci. The relative fluorescence intensities of the HDI-1/1,8-ANS system relate to a reversible temperature-driven structural transition (globular ⇌ extended) between 5 ºC and 60 °C of the polymer, in contrast to the β-CD/1,8-ANS complex. The temperature- and guest-driven structural transition, described as the “molecular accordion” effect is supported by new insight provided by complementary fluorescence and 1H NMR spectral results in aqueous solution.