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Université de Fribourg

Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Conley, Gaurasundar M. ; Aebischer, Philippe ; Nöjd, Sofi ; Schurtenberger, Peter ; Scheffold, Frank

In: Science Advances, 2017, vol. 3, no. 10, p. e1700969

Tuning the solubility of fuzzy polymer microgels by external triggers, such as temperature or pH, provides a unique mechanism for controlling the porosity and size of colloidal particles on the nanoscale. As a consequence, these smart microgel particles are being considered for applications ranging from viscosity modifiers and sensing to drug delivery and as models for the glass and the...

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 ; Grobety, Bernard ; Hirt, Ann M. ; Dietsch, Hervé ; Schurtenberger, Peter

In: Nanoscale, 2017, vol. 9, 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

Superresolution microscopy of the volume phase transition of pNIPAM microgels

Conley, Gaurasundar M. ; Nöjd, Sofi ; Braibanti, Marco ; Schurtenberger, Peter ; Scheffold, Frank

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2016, vol. 499, p. 18–23

Hierarchical polymer structures such as pNIPAM microgels have been extensively studied for their ability to undergo structural and physical transformations that can be controlled by external stimuli such as temperature, pH or solvent composition. However, a direct three-dimensional visualization of individual particles in-situ has so far been hindered by insufficient resolution, with optical...

Université de Fribourg

Characterizing nanoparticles in complex biological media and physiological fluids with depolarized dynamic light scattering

Balog, Sandor ; Rodriguez-Lorenzo, Laura ; Monnier, Christophe A. ; Obiols-Rabas, Marc ; Rothen-Rutishauser, Barbara ; Schurtenberger, Peter ; Petri-Fink, Alke

In: Nanoscale, 2015, p. -

Light scattering is one of the few techniques available to adequately characterize suspended nanoparticles (NPs) in real time and in situ. However, when it comes to NPs in multicomponent and optically complex aqueous matrices – such as biological media and physiological fluids – light scattering suffers from lack of selectivity, as distinguishing the relevant optical signals from the...

Université de Fribourg

Hard sphere-like glass transition in eye lens α-crystallin solutions

Foffi, Giuseppe ; Savin, Gabriela ; Bucciarelli, Saskia ; Dorsaz, Nicolas ; Thurston, George M. ; Stradner, Anna ; Schurtenberger, Peter

In: Proceedings of the National Academy of Sciences, 2014, vol. 111, no. 47, p. 16748–16753

We study the equilibrium liquid structure and dynamics of dilute and concentrated bovine eye lens α-crystallin solutions, using small-angle X-ray scattering, static and dynamic light scattering, viscometry, molecular dynamics simulations, and mode-coupling theory. We find that a polydisperse Percus–Yevick hard-sphere liquid-structure model accurately reproduces both static light scattering...

Université de Fribourg

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

Malik, Vikash ; Grobety, 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

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

Unexpected Decoupling of Stretching and Bending Modes in Protein Gels

Gibaud, Thomas ; Zaccone, Alessio ; Gado, Emanuela Del ; Trappe, Véronique ; Schurtenberger, Peter

In: Physical Review Letters, 2013, vol. 110, no. 5, p. 058303

We show that gels formed by arrested spinodal decomposition of protein solutions exhibit elastic properties in two distinct frequency domains, both elastic moduli exhibiting a remarkably strong dependence on volume fraction. Considering the large difference between the protein size and the characteristic length of the network we model the gels as porous media and show that the high and low...

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

Generic pathways to stability in concentrated protein mixtures

Voets, Ilja K. ; Trappe, Veronique ; Schurtenberger, Peter

In: Physical Chemistry Chemical Physics, 2012, vol. 14, no. 8, p. 2929-2933

We present a series of experimental results that disclose the crucial role of ionic strength and partial volume fractions in the control of the phase behaviour of binary protein mixtures. Our findings can be understood as that the ionic strength determines the relative contribution of the entropy of the protein counter-ions to the overall thermodynamics of the system. Associative phase separation...