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Benichou O.,CNRS Condensed Matter Physics Laboratory | Voituriez R.,CNRS Condensed Matter Physics Laboratory | Voituriez R.,University Pierre and Marie Curie
Physics Reports | Year: 2014

We present a general theory which allows one to accurately evaluate the mean first-passage time (FPT) for regular random walks in bounded domains, and its extensions to related first-passage observables such as splitting probabilities and occupation times. It is showed that this analytical approach provides a universal scaling dependence of the mean FPT on both the volume of the confining domain and the source-target distance in the case of general scale invariant processes. This analysis is applicable to a broad range of stochastic processes characterized by scale-invariance properties. The full distribution of the FPT can be obtained using similar tools, and displays universal features. This allows to quantify the fluctuations of the FPT in confinement, and to reveal the key role that can be played by the starting position of the random walker. Applications to reaction kinetics in confinement are discussed. © 2014 Elsevier B.V.

Detcheverry F.,CNRS Condensed Matter Physics Laboratory | Bocquet L.,CNRS Condensed Matter Physics Laboratory
Physical Review Letters | Year: 2012

We explore the impact of thermal fluctuations on nanofluidic transport. We develop a generic description of the stochastic motion of a fluid confined in a nanopore, on the basis of the fluctuating hydrodynamics framework. The center of mass of the confined fluid is shown to perform a non-Markovian random walk, whose diffusion coefficient depends on the nanopore geometrical characteristics and boundary slip at its surface. We discuss the implications of this Brownian-like motion of hydrodynamic degrees of freedom in two different contexts. First, we show that hydrodynamic fluctuations can lead to a strongly enhanced diffusion of particles confined in a nanopore. Second, we extend our results to account for the hydrodynamic contribution to electrical noise in charged nanopores. © 2012 American Physical Society.

Bellanger H.,CNRS Condensed Matter Physics Laboratory | Darmanin T.,CNRS Condensed Matter Physics Laboratory | Taffin De Givenchy E.,CNRS Condensed Matter Physics Laboratory | Guittard F.,CNRS Condensed Matter Physics Laboratory
Chemical Reviews | Year: 2014

A study was conducted to demonstrate chemical and physical pathways for the preparation of superoleophobic surfaces and related wetting theories. The investigations revealed that the wettability of a surface was characterized by the ability of a liquid droplet to spread. The static behavior was characterized by measuring the apparent contact angle of a liquid droplet deposited on the surface. The dynamic behavior was characterized by considering various data. Two different surfaces claimed to be superoleophobic without repelling the same oil, and it was important to always specify the oil used to characterize the surface wettability. It was also possible to evaluate the contact angle of porous, granulated, powder, and fiber materials using the transformed Washburn equation in conjunction with special instruments.

Bocquet L.,CNRS Condensed Matter Physics Laboratory | Charlaix E.,CNRS Condensed Matter Physics Laboratory
Chemical Society Reviews | Year: 2010

Nanofluidics has emerged recently in the footsteps of microfluidics, following the quest for scale reduction inherent to nanotechnologies. By definition, nanofluidics explores transport phenomena of fluids at nanometer scales. Why is the nanometer scale specific? What fluid properties are probed at nanometric scales? In other words, why does 'nanofluidics' deserve its own brand name? In this critical review, we will explore the vast manifold of length scales emerging for fluid behavior at the nanoscale, as well as the associated mechanisms and corresponding applications. We will in particular explore the interplay between bulk and interface phenomena. The limit of validity of the continuum approaches will be discussed, as well as the numerous surface induced effects occurring at these scales, from hydrodynamic slippage to the various electro-kinetic phenomena originating from the couplings between hydrodynamics and electrostatics. An enlightening analogy between ion transport in nanochannels and transport in doped semi-conductors will be discussed (156 references). © 2010 The Royal Society of Chemistry.

Darmanin T.,CNRS Condensed Matter Physics Laboratory | Guittard F.,CNRS Condensed Matter Physics Laboratory
Journal of Materials Chemistry A | Year: 2014

This review gives an overview of recent advances in the potential applications of superhydrophobic materials. Such properties are characterized by extremely high water contact angles and various adhesion properties. The conception of superhydrophobic materials has been possible by studying and mimicking natural surfaces. Now, various applications have emerged such as anti-icing, anti-corrosion and anti-bacterial coatings, microfluidic devices, textiles, oil-water separation, water desalination/purification, optical devices, sensors, batteries and catalysts. At least two parameters were found to be very important for many applications: the presence of air on superhydrophobic materials with self-cleaning properties (Cassie-Baxter state) and the robustness of the superhydrophobic properties (stability of the Cassie-Baxter state). This review will allow researchers to envisage new ideas and industrialists to advance in the commercialization of these materials. This journal is © the Partner Organisations 2014.

Bachelard N.,ESPCI ParisTech | Gigan S.,ESPCI ParisTech | Noblin X.,CNRS Condensed Matter Physics Laboratory | Sebbah P.,ESPCI ParisTech
Nature Physics | Year: 2014

A laser is not necessarily a sophisticated device: pumping an amplifying medium randomly filled with scatterers makes a perfectly viable â ̃ random laserâ ™. The absence of mirrors greatly simplifies laser design, but control over the emission wavelength and directionality is lost, seriously hindering prospects for this otherwise simple laser. Recently, we proposed an approach to tame random lasers, inspired by coherent light control in complex media. Here, we implement this method in an optofluidic random laser where modes are spatially extended and overlap, making individual mode selection impossible, a priori. We show experimentally that control over laser emission can be regained even in this extreme case. By actively shaping the optical pump within the random laser, single-mode operation at any selected wavelength is achieved with spectral selectivity down to 0.06 nm and more than 10 dB side-lobe rejection. This method paves the way towards versatile tunable and controlled random lasers as well as the taming of other laser sources. © 2014 Macmillan Publishers Limited. All rights reserved.

Bouzigues C.,French Institute of Health and Medical Research | Gacoin T.,CNRS Condensed Matter Physics Laboratory | Alexandrou A.,French Institute of Health and Medical Research
ACS Nano | Year: 2011

Biomedicine and cell and molecular biology require powerful imaging techniques of the single molecule scale to the whole organism, either for fundamental science or diagnosis. These applications are however often limited by the optical properties of the available probes. Moreover, in cell biology, the measurement of the cell response with spatial and temporal resolution is a central instrumental problem. This has been one of the main motivations for the development of new probes and imaging techniques either for biomolecule labeling or detection of an intracellular signaling species. The weak photostability of genetically encoded probes or organic dyes has motivated the interest for different types of nanoparticles for imaging such as quantum dots, nanodiamonds, dye-doped silica particles, or metallic nanoparticles. One of the most active fields of research in the past decade has thus been the development of rare-earth based nanoparticles, whose optical properties and low cytotoxicity are promising for biological applications. Attractive properties of rare-earth based nanoparticles include high photostability, absence of blinking, extremely narrow emission lines, large Stokes shifts, long lifetimes that can be exploited for retarded detection schemes, and facile functionalization strategies. The use of specific ions in their compositions can be moreover exploited for oxidant detection or for implementing potent contrast agents for magnetic resonance imaging. In this review, we present these different applications of rare-earth nanoparticles for biomolecule detection and imaging in vitro, in living cells or in small animals. We highlight how chemical composition tuning and surface functionalization lead to specific properties, which can be used for different imaging modalities. We discuss their performances for imaging in comparison with other probes and to what extent they could constitute a central tool in the future of molecular and cell biology. © 2011 American Chemical Society.

Darmanin T.,CNRS Condensed Matter Physics Laboratory | De Givenchy E.T.,CNRS Condensed Matter Physics Laboratory | Amigoni S.,CNRS Condensed Matter Physics Laboratory | Guittard F.,CNRS Condensed Matter Physics Laboratory
Advanced Materials | Year: 2013

This review is an exhaustive representation of the electrochemical processes reported in the literature to produce superhydrophobic surfaces. Due to the intensive demand in the elaboration of superhydrophobic materials using low-cost, reproducible and fast methods, the use of strategies based on electrochemical processes have exponentially grown these last five years. These strategies are separated in two parts: the oxidation processes, such as oxidation of metals in solution, the anodization of metals or the electrodeposition of conducting polymers, and the reduction processed such as the electrodeposition of metals or the galvanic deposition. One of the main advantages of the electrochemical processes is the relative easiness to produce various surface morphologies and a precise control of the structures at a micro- or a nanoscale. This review reports most of the processes reported in the literature to produce superhydrophobic surfaces based on electrochemical processes. These strategies usually use low-cost, reproducible and fast methods in order to produce various surface morphologies and to control precisely the structures at a micro- or a nanoscale. The review is divided in two parts: the oxidation processes and the reduction processes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The study compared the accuracy of several model-fitting methods for the computation of compensation parameters. Two methods were presented for the model-free computation of the pre-exponential factor dependency using kinetic compensation parameters and isoconversional methods. These methods give accurate results for both single and multi-step kinetics. Once the pre-exponential factors have been evaluated in a model-free way, three model-free methods were proposed to compute the values of the mathematical function that describes the reaction mechanism for multi-step kinetics. These methods can be preferred according to the type of data available (i.e. differential or integral). Accurate results were obtained for both single and multi-step kinetics using two sets of simulated data and an experimental example. Copyright © 2013 Published by Elsevier B.V. All rights reserved.

Grebenkov D.S.,CNRS Condensed Matter Physics Laboratory
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

We study the probability distribution of the time-averaged mean-square displacement of a discrete Gaussian process. An empirical approximation for the probability density is suggested and numerically validated for fractional Brownian motion. The optimality of quadratic forms for inferring dynamical and microrheological quantities from individual random trajectories is discussed, with emphasis on a reliable interpretation of single-particle tracking experiments. © 2011 American Physical Society.

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