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Engineering, Norway

Sundman O.,Umea University | Nordgard E.L.,Ugelstad Laboratory | Grimes B.,Ugelstad Laboratory | Sjoblom J.,Ugelstad Laboratory

The acid/base properties, critical micelle concentrations (cmcs), and. pH-dependent solubility of five synthetic tetraacids have been studied at several ionic strengths (20-600 mM NaCl) and in the pH range of 1.5-11 using high precision Potentiometrie titrations, tensiometer measurements, and. UV spectroscopy, respectively. The molecular weight of the tetraacids ranged, between 478 and. 983 g/mol. The Potentiometrie titration data was evaluated, in terms of thermodynamic equilibrium models, developed in the light of relevant solubility data, Langmuir monolayer compressions and cmc of the different tetraacids. The results indicate that for two of the tetraacids, called BP5 and BP7, two chemical forms fully dominate the speciation of the monomers; the insoluble fully protonated form, and the soluble fully deprotonated form, The partly protonated species, only play a very minor role in the speciation of these tetraacids. For the other tetraacids the results are more complicated; for the smallest tetraacid, called BPl, all species seem to play important roles, and for the most hydrophobic, BP10, the formation of micelles and aggregates severely complicates the evaluation of the speciation. For the tetraacid BP3 one of the partly deprotonated forms seems to be important, thus confirming the structure to properties relationship. In spite of the complicated micelle formation chemistry, and although not actually measured, the acid/base properties for the monomers of BPlO were interpreted by means of surface charge densities of the micellar aggregates. The modeling indicates an increase of the aggregation number of the micelle upon acidification, a result of formation of mixed micelles incorporating the fully protonated and deprotonated species. An intrinsic pKa of 5.4 for BP5 was used, to model the monomer pk a of BP10, and corresponded well with a monolayer acidity constant pks a of 5.5 obtained from, surface collapse pressures of Langmuir monolayers as a function ofpH. ©2010 American Chemical Society. Source

Sundman O.,Umea University | Simon S.,Ugelstad Laboratory | Nordgard E.L.,Ugelstad Laboratory | Sjoblom J.,Ugelstad Laboratory
Energy and Fuels

The previously presented synthetic tetra-acid model compound BP10 was used to investigate the chemistry behind the formation of metal naphthenate deposits. The interactions between BP10 and the cations Ba 2+, Ca 2+, H +, Mg 2+, and Sr 2+ were investigated using potentiometric titrations, metal ion depletion by inductively coupled plasma-atomic emission spectrometry (ICP-AES), pH measurements, and elemental analysis of precipitates, in 20-600 mM NaCl ionic medium. The interactions of BP10 with the monovalent Na + are discussed on the basis of a previous study. The data given indicate that Ca 2+ shows the strongest affinity toward BP10 and Ba 2+, and Sr 2+ form approximately equally stable solid phases with BP10, while Mg 2+ is less tightly bound to the tetra-acid. H + interacts more strongly than the Me 2+ ions, and Na + shows a rather small affinity for BP10. No soluble complexes could be detected, and all products in the chemical reactions are therefore believed to be solid materials. We suggest that BP10 show the following preference of cations: H + ≫ Ca 2+ > Ba 2+ ≈ Sr 2+ > Mg 2+ ≫ Na +. This order could be due to the hydration state and size of the cations. In comparison to typical concentrations found of each in saline water, it is proposed that the dominance of Ca 2+ in naphthenate deposits is dependent upon both availability and selectivity. © 2010 American Chemical Society. Source

Bandyopadhyay S.,Ugelstad Laboratory | Singh G.,Ugelstad Laboratory | Sandvig I.,Norwegian University of Science and Technology | Sandvig A.,Norwegian University of Science and Technology | And 5 more authors.
Applied Surface Science

Fe@Au core-shell nanoparticles (NPs) exhibit multiple functionalities enabling their effective use in applications such as medical imaging and drug delivery. In this work, a novel synthetic method was developed and optimized for the synthesis of highly stable, monodisperse Fe@Au NPs of average diameter ∼24nm exhibiting magneto-plasmonic characteristics. Fe@Au NPs were characterized by a wide range of experimental techniques, including scanning (transmission) electron microscopy (S(T)EM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS) and UV-vis spectroscopy. The formed particles comprise an amorphous iron core with a crystalline Au shell of tunable thickness, and retain the superparamagnetic properties at room temperature after formation of a crystalline Au shell. After surface modification, PEGylated Fe@Au NPs were used for in vitro studies on olfactory ensheathing cells (OECs) and human neural stem cells (hNSCs). No adverse effects of the Fe@Au particles were observed post-labeling, both cell types retaining normal morphology, viability, proliferation, and motility. It can be concluded that no appreciable toxic effects on both cell types, coupled with multifunctionality and chemical stability make them ideal candidates for therapeutic as well as diagnostic applications. © 2014 Elsevier B.V. All rights reserved. Source

Meysam N.,Ugelstad Laboratory | Tichelkamp T.,Ugelstad Laboratory | Oye G.,Ugelstad Laboratory
2nd International Conference on Engineering Geophysics

Many definitions of the capillary number currently used in petroleum science neglect the contact angle or set it equal to zero by assuming strongly water-wet reservoir conditions. Nonetheless mixed-wet and oil-wet reservoirs are more common than water-wet ones. In those studies in which the contact angle or its cosine, respectively, is considered, wettability alterations are often treated independent of the water-oil interfacial tension. However, drastic reductions of the latter, which have been in the focus of studies on surfactant flooding for several years, should not be thought to leave the contact angle unchanged. Also, to the knowledge of the authors, the vertical component of water-oil interfacial tension and its effect on the capillary number have not been discussed in petroleum science by now. This value, described extensively by Kern and Müller (1991), is considered to be of some relevance in the mathematical treatment of microscopic wetting phenomena. Taking the vertical component of the interfacial tension into account, a new expression of the capillary number was derived to explain the connection between contact angle, oil-rock surface tension, water-rock surface tension and water-oil interfacial tension. Source

Benmekhbi M.,Ugelstad Laboratory | Benmekhbi M.,Innovation Norway | Simon S.,Ugelstad Laboratory | Simon S.,Innovation Norway | And 2 more authors.
Journal of Dispersion Science and Technology

The adsorption characteristics of Span 80 at liquid/liquid interfaces were investigated. The equilibrium interfacial tension values were successfully fitted with a Langmuir isotherm resulting in the determination of a mean molecular area from 25 to 35 Å2/mol. The measured interfacial tension values and deduced adsorption parameters depend on the experimental technique used to obtain them, either Du Noüy ring or profile analysis tensiometry. Two possible explanations to such phenomenon are provided. Adsorption kinetics of Span 80 at liquid/liquid interfaces were studied, and it was concluded that the diffusion of Span 80 molecules from the bulk is the rate determining step of the adsorption. Finally the interfacial rheology properties were investigated and compared to the Lucassen-van den Tempel model. A good match was obtained when the isotherm parameters determined by profile analysis tensiometry were used. © 2014 Copyright Taylor & Francis Group, LLC. Source

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