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Amsterdam-Zuidoost, Netherlands

Svrcek V.,Japan National Institute of Advanced Industrial Science and Technology | Dohnalova K.,Van der Waals Zeeman Institute | Mariotti D.,University of Ulster | Trinh M.T.,Van der Waals Zeeman Institute | And 6 more authors.
Advanced Functional Materials | Year: 2013

Substantial improvements of the absolute photoluminescence quantum yield (QY) for surfactant-free silicon nanocrystals (Si-ncs) by atmospheric pressure microplasma 3-dimensional surface engineering are reported. The effect of surface characteristics on carrier multiplication mechanisms is explored using transient induced absorption and photoluminescence QY. Surface engineering of Si-ncs is demonstrated to lead to more than 120 times increase in the absolute QY (from 0.1% up to 12%) within an important spectral range of the solar emission (2.3-3 eV). The Si-ncs QY is shown to be stable when Si-ncs are stored in ethanol at ambient conditions for three months. Dramatic improvements in the absolute photoluminescence quantum yield (QY) and stability of surfactant-free 3D surface- engineered silicon nanocrystals (Si-ncs) within an important spectral region are demonstrated. The microplasma-induced 3D surface engineering results in more than 120 times enhancement QY for low energy photons (<2.7 eV) and ≈15 times higher for high energy photons (3.5-4.8 eV). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aytouna M.,Van der Waals Zeeman Institute | Bartolo D.,ESPCI ParisTech | Wegdam G.,Van der Waals Zeeman Institute | Bonn D.,Van der Waals Zeeman Institute | And 3 more authors.
Experiments in Fluids | Year: 2010

We study the impact and subsequent retraction of aqueous surfactant-laden drops upon high-speed impact on hydrophobic surfaces. Without surfactants, a rapid expansion of the drop due to the fluid inertia is followed by a rapid retraction, due to the wetting incompatibility. With surfactants, the retraction can be partly or completely inhibited. We provide quantitative measurements showing that both the expansion and the retraction dynamics depend not only on the equilibrium surface tension (ST) but also on the dynamic tension of the surfactant solutions; the latter varies significantly between different surfactants. © 2009 The Author(s).

Pan Z.,Van der Waals Zeeman Institute | De Cagny H.,Van der Waals Zeeman Institute | Weber B.,Van der Waals Zeeman Institute | Bonn D.,Van der Waals Zeeman Institute
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We study the rheological behavior of concentrated granular suspensions of simple spherical particles. Under controlled stress, the system exhibits an S-shaped flow curve (stress vs shear rate) with a negative slope in between the low-viscosity Newtonian regime and the shear thickened regime. Under controlled shear rate, a discontinuous transition between the two states is observed. Stress visualization experiments with a fluorescent probe suggest that friction is at the origin of shear thickening. Stress visualization shows that the stress in the system remains homogeneous (no shear banding) if a stress is imposed that is intermediate between the high- and low-stress branches. The S-shaped shear thickening is then due to the discontinuous formation of a frictional force network between particles upon increasing the stress. © 2015 American Physical Society.

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