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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.

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.

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.

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.

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.

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