Accueil >
Production scientifique
(83) Production(s) de STOCCO A.
|
|
Enhanced active motion of Janus Colloids at the water surface
Auteur(s): Wang X., In M., Blanc C., Nobili M., Stocco A.
Conference: 23e Congres general de la Societe Francaise de Physique (Strasbourg, FR, 2015-08-24)
Ref HAL: hal-01257720_v1
Exporter : BibTex | endNote
Résumé: Active colloids are an emerging and promising class of colloidal particles, which are designed to perform autonomous motion as biological microswimmers by transforming chemical or other form of energies into work and propulsion. When the particle size is about a micrometer or smaller, the directional propulsion competes with the translational and rotational Brownian motion. Here we explore the possibility of enhancing the directional motion of self-propelled Janus colloids by slowing down their rotational diffusion.We have investigated the active motion of self-propelled colloids confined at the air-water interface. The two dimensional motion of micron-sized Silica-Platinum Janus colloids has been experimentally measured by particle tracking video-microscopy under increasing concentration of the catalytic fuel, i.e. H2O2. Comparing to the motion in bulk, a dramatic enhancement of both the persistence length of trajectories and the speed has been observed. The interplay of colloid self-propulsion, due to an asymmetric catalytic reaction occurring on the colloid, and interfacial frictions controls the enhancement of the directional movement. The slowing down of the rotational diffusion at the interface, also measured experimentally, plays a pivotal role in the control and enhancement of active motion.
|
|
The active motion of Janus colloids at the surface of water
Auteur(s): Stocco A.
(Séminaires)
Le Laboratoire Ondes et Matière d’Aquitaine, LOMA (Bordeaux, FR), 2015-12-08 |
|
|
The Influence of Long-Range Surface Forces on the Contact Angle of Nanometric Droplets and Bubbles
Auteur(s): Stocco A., Moehwald H.
(Article) Publié:
Langmuir, vol. 31 p.11835–11841 (2015)
Texte intégral en Openaccess :
Ref HAL: hal-01225317_v1
DOI: 10.1021/acs.langmuir.5b02922
WoS: 000364354800011
Exporter : BibTex | endNote
9 Citations
Résumé: For a droplet or a bubble of dimensions below 100 nm, long-range surface forces such as long-range van der Waals forces can compete with capillarity, which leads to a size dependence of the contact angle. This is discussed in this work, where we also show that the effect cannot simply be described by a normalized line tension. We calculate interfacial profiles for typical values of van der Waals forces and discuss the role of long-range surface forces on the contact angle of nanobubbles and nanodrops.
|
|
|
Enhanced active motion of Janus colloids at the water surface
Auteur(s): Wang X., In M., Blanc C., Nobili M., Stocco A.
(Article) Publié:
Soft Matter, vol. 11 p.7376-7384 (2015)
Texte intégral en Openaccess :
Ref HAL: hal-01216307_v1
DOI: 10.1039/c5sm01111f
WoS: WOS:000361550000018
Exporter : BibTex | endNote
51 Citations
Résumé: We have investigated the active motion of self-propelled colloids confined at the air–water interface and explored the possibility of enhancing the directional motion of self-propelled Janus colloids by slowing down their rotational diffusion. The two dimensional motion of micron-sized silica–platinum Janus colloids has been experimentally measured by particle tracking video-microscopy at increasing concentrations of the catalytic fuel, i.e. H2O2. Compared to the motion in the bulk, a dramatic enhancement of both the persistence length of trajectories and the speed has been observed. The interplay of colloid self-propulsion, due to an asymmetric catalytic reaction occurring on the colloid, surface properties and interfacial frictions controls the enhancement of the directional movement. The slowing down of the rotational diffusion at the interface, also measured experimentally, plays a pivotal role in the control and enhancement of active motion.
|
|
|
Brownian diffusion of a partially wetted colloid
Auteur(s): Boniello G., Blanc C., Fedorenko D., Medfai Mayssa, Ben Mbarek Nadia, In M., Gross M., Stocco A., Nobili M.
(Article) Publié:
Nature Materials, vol. 14 p.908 (2015)
Ref HAL: hal-01202128_v1
DOI: 10.1038/NMAT4348
WoS: 000360192000024
Exporter : BibTex | endNote
74 Citations
Résumé: The dynamics of colloidal particles at interfaces between two fluids plays a central role in microrheology, encapsulation, emulsification, biofilm formation, water remediation and the interface-driven assembly of materials. Common intuition corroborated by hydrodynamic theories, suggests that such dynamics is governed by a viscous force lower than that observed in the more viscous fluid. Here, we show experimentally that a particle straddling an air/water interface feels a large viscous drag that is unexpectedly larger than that measured in the bulk. We suggest that such a result arises from thermally activated fluctuations of the interface at the solid/air/liquid triple line and their coupling to the particle drag through the fluctuation–dissipation theorem. Our findings should inform approaches for improved control of the kinetically driven assembly of anisotropic particles with a large triple-line-length/particle-size ratio, and help to understand the formation and structure of such arrested materials.
|
|
Nanoparticles, Polymers and fluid Interfaces by ellipsometry
Auteur(s): Stocco A.
(Séminaires)
University of Twente (Twente, NL), 2015-01-12 |
|
|
Droplet Liquid/Liquid Interfaces Generated in a Microfluidic Device for Assembling Janus Inorganic Nanohybrids
Auteur(s): Hassan Natalia, Stocco A., Abou-Hassan Ali
(Article) Publié:
The Journal Of Physical Chemistry C, vol. 119 p.10758–10765 (2015)
Ref HAL: hal-01163692_v1
DOI: 10.1021/acs.jpcc.5b02527
WoS: 000354912200069
Exporter : BibTex | endNote
22 Citations
Résumé: One among other remarkable methods to produce multifunctional assemblies with different spatial organizations is the use of liquid–liquid (L–L) interfaces. Herein, a droplet microfluidic-based method is reported as a strategy for the assembly of asymmetrical inorganic nanohybrid structures. As a proof of concept and motivated by their wide applications in different fields, we studied the assembly of two building nanoblocks, which are fluorescent silica (160 nm diameter) and gold nanoparticles (15 nm diameter). In this strategy, droplets of an aqueous solution of citrated gold nanoparticles are generated in a continuous flow of amine functionalized fluorescent silica nanoparticles dispersed in cyclohexane using the microdevice. The electrostatic attraction between the two nanoparticles confined at the water/cyclohexane interface to form a Pickering emulsion allowed their assembly. We show that Janus nanohybrids can only be observed when the residence time in the microdevice was less than 30 min, thus avoiding the formation of solid shells for longer residence times. Transmission and scanning electron microscopies, optical microscopies, and UV–vis spectroscopy were used to characterize the resulting assemblies. The results were compared to experiments in bulk which showed that microfluidics offers a higher control over the assembly and reduces the time for their elaboration. Moreover, an analytical model based on transport of nanoparticles and their adsorption onto interfaces is used to rationalize our observations. Both flow recirculation inside and outside the droplets in the microchannel and the confinement effect seem to be relevant for the enhanced nanoparticle transport to the interfaces.
|