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Université de Fribourg

Catalytic hydrogenation using abnormal N-heterocyclic carbene palladium complexes: catalytic scope and mechanistic insights

Heckenroth, Marion ; Khlebnikov, Vsevolod ; Neels, Antonia ; Schurtenberger, Peter ; Albrecht, Martin

In: ChemCatChem, 2011, vol. 3, no. 1, p. 167-173

Palladium complexes containing abnormally bound C4-bound dicarbene ligands have been exploited for catalytic alkene hydrogenation. Comparison to normally C2-bound homologues indicates that the carbene bonding mode critically influences the catalytic activity. Good catalytic performance in the hydrogenation of cis-disubstituted olefins and non-isomerizable terminal olefins under mild...

Université de Fribourg

Tracer microrheology of γ-dodecalactone induced gelation of aqueous starch dispersions

Heinemann, Cornelia ; Cardinaux, Frédéric ; Scheffold, Frank ; Schurtenberger, Peter ; Escher, Felix ; Conde-Petit, Béatrice

In: Carbohydrate Polymers, 2004, vol. 55, p. 155-161

We have studied the rheological properties of the natural biopolymer system starch in the presence of the gelation inducing flavor compound γ-dodecalactone. From optical microrheology, based on the multiple scattering of laser light (DWS), we deduce the frequency-dependent moduli G(ω) and G″(ω) of the gelling sample over the full frequency range. Our measurements demonstrate the inherent...

Université de Fribourg

Characterization of the pores in hydrous ferric oxide aggregates formed by freezing and thawing

Hofmann, Annette ; Pelletier, Manuel ; Michot, Laurent ; Stradner, Anna ; Schurtenberger, Peter ; Kretzschmar, Ruben

In: Journal of Colloid and Interface Science, 2004, vol. 271, p. 163-173

Hydrous ferric oxides (HFO) are efficient sorbents for inorganic and organic pollutants and therefore have great potentials in environmental science and engineering applications. Freezing and thawing of HFO suspensions leads to the formation of dense HFO aggregates. It facilitates the handling and increases the drying rate of HFO. In this study, we used a combination of pycnometry, gas adsorption...

Université de Fribourg

Oil-continuous microemulsions mixed with an amphiphilic graft copolymer or with the parent homopolymer. Polymer–droplet interactions as revealed by phase behavior and light scattering

Holmberg, Anna ; Piculell, Lennart ; Schurtenberger, Peter ; Olsson, Ulf

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004, vol. 250, p. 325-336

Polymer–droplet interactions have been studied in AOT/water/isooctane oil-continuous microemulsions mixed with an amphiphilic graft copolymer, or with the parent homopolymer (AOT = sodium bis(2-ethylhexyl) sulfosuccinate). The graft copolymer has an oil-soluble poly(dodecyl methacrylate) backbone and water-soluble poly(ethylene glycol) side chains. Pseudo-ternary polymer/droplet/isooctane phase...

Université de Fribourg

Photoinitiated coupling of unmodified monosaccharides to iron oxide nanoparticles for sensing proteins and bacteria

Liu, Li-Hong ; Dietsch, Hervé ; Schurtenberger, Peter ; Yan, Mingdi

In: Bioconjugate Chemistry, 2009, vol. 20, no. 7, p. 1349–1355

We report a versatile approach for the immobilization of unmodified monosaccharides onto iron oxide nanoparticles. Covalent coupling of the carbohydrate onto iron oxide nanoparticle surfaces was accomplished by the CH insertion reaction of photochemically activated phosphate-functionalized perfluorophenylazides (PFPAs), and the resulting glyconanoparticles were characterized by IR, TGA, and TEM....

Université de Fribourg

Hybrid magnetic iron oxide nanoparticles with tunable field-directed self-assembly

Malik, Vikash ; Pal, Antara ; Pravaz, Olivier ; Crassous, Jérôme J. ; Granville, Simon ; Grobéty, Bernard ; Hirt, Ann M. ; Dietsch, Hervé ; Schurtenberger, Peter

In: Nanoscale, 2017, vol. 9, no. 38, p. 14405-14413

We describe the synthesis of hybrid magnetic ellipsoidal nanoparticles that consist of a mixture of two different iron oxide phases, hematite (α-Fe2O3) and maghemite (γ- Fe2O3), and characterize their magnetic field-driven self-assembly. We demonstrate that the relative amount of the two phases can be adjusted in a continuous way by varying the reaction time during the synthesis, leading to...

Université de Fribourg

A closer look at the synthesis and formation mechanism of hematite nanocubes

Malik, Vikash ; Grobéty, Bernard ; Trappe, Veronique ; Dietsch, Herve ; Schurtenberger, Peter

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014, vol. 445, p. 21-29

We have synthesized hematite cube-shaped nanoparticles using different synthesis paths to examine the effect of the intermediate product akaganeite (β-FeOOH) on the size and shape of the final hematite particles. Akaganeite spindles and hematite nanocubes are prepared using forced hydrolysis of iron chloride (FeCl₃) salt. We use a combination of transmission electron microscopy (TEM), high...

Université de Fribourg

Deformable particles with anisotropic interactions: unusual field-induced structural transitions in ultrasoft ionic microgel colloids

Mohanty, Priti S. ; Yethiraj, Anand ; Schurtenberger, Peter

In: Soft MatterSoft Matter, 2012, vol. 8, no. 42, p. 10819-10822

Ionic microgels are intriguing soft and deformable colloids with an effective pair potential that crosses over from Yukawa-like at large distances to a much softer repulsive interaction at short distances. Here we report the effect of adding an anisotropic dipolar contribution to colloids with such “ultra-soft” interactions. We use an alternating electric field to induce a tunable dipolar...

Université de Fribourg

Effective interactions between soft-repulsive colloids: Experiments, theory, and simulations

Mohanty, Priti S. ; Paloli, Divya ; Crassous, Jérôme J. ; Zaccarelli, Emanuela ; Schurtenberger, Peter

In: The Journal of Chemical Physics, 2014, vol. 140, no. 9, p. 094901

We describe a combined experimental, theoretical, and simulation study of the structural correlations between cross-linked highly monodisperse and swollen Poly(N-isopropylacrylamide) microgel dispersions in the fluid phase in order to obtain the effective pair-interaction potential between the microgels. The density-dependent experimental pair distribution functions g(r)’s are deduced from real...

Université de Fribourg

Synthesis and characterization of novel functional electrosterically stabilized colloidal particles prepared by emulsion polymerization using a strongly ionized amphiphilic diblock copolymer

Mohanty, Priti S. ; Dietsch, Hervé ; Rubatat, Laurent ; Stradner, Anna ; Matsumoto, K. ; Matsuoka, H. ; Schurtenberger, Peter

In: Langmuir, 2009, vol. 25, no. 4, p. 1940–1948

Amphiphilic diblock copolymers such as poly(styrene)-block-poly(styrene sulfonate) (PS-b-PSS) (Matsuoka, H.; Maeda, S.; Kaewsaiha, P.; Matsumoto, K. Langmuir 2004, 20, 7412), belong to a class of new polymeric surfactants that ionize strongly in aqueous media. We investigated their self-assembly behavior in aqueous solutions and used them as an emulsifier to...