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Long-range correlations measured between water molecules

The configuration of water molecules in an aqueous solution transitions from a long-range stacked pattern to a short-range radial pattern when salt is added.

In this article, published in the journal Physical Review Letters, Julien Duboisset (Institut Fresnel, Marseille) and Pierre-François Brevet (Institut Lumière Matière, Lyon) describe nonlinear optical experiments in the liquid phase determining the orientation correlation of water molecules. These experiments show that water molecules are organized over much greater distances than is usually accepted. They demonstrate indeed that the molecules are orientationnally arranged over distances of several tens of nanometers in a spatial azimuthal distribution. This work also show that when salt is added, a transition occurs where water molecules abruptly change their initial organisation into a short scale radial distribution centered on the salt ions.
This discovery, published in the journal Physical Review Letters and selected by the editor as a highlight, challenges the classic view of liquids and their organization of molecules at the nanoscale.

Left : Illustration of long range correlations between water molecules. In red, water molecules, in blue salts.
Right : lenght of correlations as function of salt concentration.

Reference :
Salt-induced Long-to-Short Range Orientational Transition in Water, Julien Duboisset and Pierre-François Brevet, Phys. Rev. Lett. 120, 263001 (2018) - Consulter l’article on-line

Contact Researchers :

- Julien Duboisset, Institut Fresnel - UMR7249, Aix Marseille Univ, CNRS, Centrale Marseille, 13013 Marseille, France (INSIS)
julien.duboisset chez fresnel.fr
Tél : 04 91 28 80 49

- Pierre-François Brevet, Institut Lumière Matière – UMR 5306, Université Lyon1, CNRS, 69622 Villeurbanne, France (INP)
pierre-francois.brevet chez univ-lyon1.fr


"Enhancing magnetic light emission with all-dialectric optical nanoantennas"

Article published in Nano Letters, september 2018

Des chercheurs ont élaboré une nanostructure capable d’accroître le champ magnétique d’une onde lumineuse, ouvrant la possibilité d’observer l’interaction entre cette composante magnétique de la lumière, et la matière.

Ces travaux ont été menés par des physiciens de l’Institut des nanosciences de Paris (CNRS/Sorbonne Université) et l’Institut de Ciencies Fotoniques, en collaboration avec :
- le Laboratoire de physique et d’études des matériaux (CNRS/ESPCI Paris/Sorbonne Université),
- l’IBM Almaden Research Center (USA),
- l’Institut Fresnel (CNRS/AMU/Centrale Marseille),
- le Laboratoire de physique de la matière condensée (CNRS/X
- l’Institut Langevin (CNRS/ESPCI Paris/Univ. Paris Diderot/Inserm/Sorbonne Université)

Reference :
Enhancing magnetic light emission with all-dielectric optical nanoantennas
M. Sanz-Paz, C. Ernandes, J. Uriel Esparza, G. W. Burr, N. F. van Hulst, A. Maitre, L. Aigouy, T. Gacoin, N. Bonod, M. F. Garcia-Parajo , S. Bidault et M. Mivelle,
Nano Letters (2018)
doi:10.1021/acs.nanolett.8b00548


Développement d’un technique d’imagerie moléculaire des tissus pour des applications médicales "SRGold"
Projet de maturation de la SATT Sud-Est en collaboration avec le CNRS et HORIBA France

Grâce à une avancée majeure en microscopie Raman stimulée, des chercheurs de l’équipe MOSAIC proposent désormais de réaliser en quelques minutes une image des molécules présentes dans un échantillon biologique. Les perspectives sont donc de pouvoir produire une nouvelle génération d’instruments hospitaliers afin de mieux identifier les tissus cancéreux.

La technique de Spectroscopie Raman Stimulée (SRS) permet de localiser dans un échantillon certaines espèces chimiques, identifiées par le type de liaisons qu’elles contiennent. Cette méthode appliquée à la microscopie de tissus biologiques permettra notamment de distinguer les tissus qui ont un caractère cancéreux. Or, les signaux Raman des molécules recherchées (collagène, acides aminés, ADN...) sont faibles et masqués par des signaux parasites. Des chercheurs de notre laboratoire ont donc résolu ces difficultés en améliorant le dispositif de microscopie SRS.

Baptisé SRGold pour "Stimulated raman gain opposite loss detection", ce système breveté en copropriété entre le CNRS et Aix Marseille Université (AMU) a pour effet d’annuler les signaux parasites, tout en multipliant par deux l’intensité du signal des molécules recherchées dans un tissu. Ces résultats sont obtenus grâce à un troisième faisceau laser, qui s’ajoute aux deux lasers qui équipent déjà un dispositif SRS traditionnel.

Le projet de maturation de la SATT Sud-Est, en collaboration avec le CNRS, a pour objectif de montrer l’apport de la technologie SRGold dans un contexte hospitalier. Ce projet est mené en collaboration avec l’Institut Paoli-Calmettes pour la détection de cancers du tube digestif et avec l’Hôpital de la Timone pour la détection de tumeurs cérébrales.

La technologie SRGold devrait permettre d’obtenir des images d’histologie moléculaire d’un tissu cancéreux en quelques minutes, au lieu de 24 heures avec l’histologie standard, et sans avoir recours à aucun marqueur explique Hervé Rigneault, responsable de l’équipe MOSAIC à l’origine de ce projet.

La société HORIBA France est enfin partenaire de ce projet de maturation, qui débouchera sur une licence d’exploitation exclusive concédée par la SATT Sud-Est. A plus long terme, la technologie SRGold étant adaptable à une fibre optique, des applications à l’endoscopie devraient également être envisagées.

Contact : Hervé RIGNEAULT


On the scattering directionality of a dielectric particle dimer of High Refractive Index

"Open access" Article on https://www.nature.com/articles/s41598-018-26359-8

Low-losses and directionality effects exhibited by High Refractive Index Dielectric particles make them attractive for applications where radiation direction control is relevant. For instance, isolated metallo-dielectric core-shell particles or aggregates (dimers) of High Refractive Index Dielectric particles have been proposed for building operational switching devices. Also, the possibility of using isolated High Refractive Index Dielectric particles for optimizing solar cells performance has been explored. Here, we present experimental evidence in the microwave range, that a High Refractive Index Dielectric dimer of spherical particles is more efficient for redirecting the incident radiation in the forward direction than the isolated case. In fact, we report two spectral regions in the dipolar spectral range where the incident intensity is mostly scattered in the forward direction. They correspond to the Zero-Backward condition (also observed for isolated particles) and to a new condition, denoted as “near Zero-Backward” condition, which comes from the interaction effects between the particles. The proposed configuration has implications in solar energy harvesting devices and in radiation guiding.


Two particles to scatter the energy in the forward direction when a single particle behaves as a reflector


Revealing the crystalline details of a biomineral shell structure
Towards the understanding of biomineralization thanks to a new x-ray microscopy

Biomineralization processes, which produce outstandingly complex mineralized structures in living organisms, are still poorly understood. Thanks to 3D Bragg ptychography, a recently proposed x-ray microscopy, new structural features of a paradigmatic calcareous biomineral have been revealed, allowing supporting recently proposed biomineralization models [1].

In many living organisms, biomineralization processes regulate the production of the mineralized tissues such as bones, teeth, shells… Deciphering these mechanisms is of crucial importance for materials science, as it will provide bio-inspired strategies for the synthesis of nanostructured inorganic materials using soft chemistry and environmentally friendly processes. Strong impacts are also expected in paleoclimatology that uses biomineral proxies to perform paleoclimate reconstructions. Among the existing biominerals, calcium carbonate biomineral is one of the most striking examples : while it is clear that theories arising from classical crystallization (involving monomer-by-monomer addition) can not explain the production of highly regulated calcareous crystalline biomineral structures as the ones observed in sea urchin or pearl oyster, for instance, the production of this major constituent of the Earth’s crust is still poorly understood.

The present study developed by an interdisciplinary French team lead by Institut Fresnel was motivated by an apparent contradiction observed in biomineral structures : while calcareous crystallizing species present a remarkable architectural diversity at the macro and micro-scales, their sub-micrometric scale is characterized by the consistent observation of a granular, but crystalline, structure. Hence, a proper description of the crystalline features at this mesoscale level, i.e., over a few sub-micrometric (50-500nm) granules, is a key to building realistic scenarios of biomineralization. However, none of the currently used experimental approaches (electron- or x-ray-based diffraction microscopies) is able to provide access to the detailed 3D crystalline granule arrangement.

In 2011, scientists from Institut Fresnel have proposed a new approach, named Bragg ptychography, to image in 3D the crystalline properties of complex materials [2]. This cutting-edge synchrotron-based x-ray microscopy was implemented at a synchrotron source (ESRF-ID13 beamline) and used to reveal the details of the mesocrystalline organization in calcite prisms, the generic mineral units of the pearl oyster shell (Figure). While these prisms are usually described as single-crystal, the 3D image proves the existence of large iso-oriented and iso-strained crystalline domains, slightly different one from the other (Figure). These original results call for specific non-classical crystallization pathways : the highlighted mesocrystalline properties support recent biomineralization models, involving partial fusion of oriented attached nanoparticle assembly and/or liquid droplet precursors.

This study has been performed in the framework of a 4-year ANR grant. It constitutes the starting point of an ERC project, aiming at defining the physical, chemical and biological conditions needed to produce synthetic biominerals, on demand. We expect that the unique properties of the forthcoming synchrotron sources combined to the new (and fast) Bragg ptychography microscopy [3] will enable them to achieve this goal.

Figure : 3D image of the crystalline properties of a biomineral. (A) Optical image of the investigated pearl oyster shell (Pinctada margaritifera) highlighting the investigated region (white rectangle). (B) Zoom-in view of the shell border showing its microscopic structure, composed of juxtaposed calcite prisms. (C) The probed volume (in yellow-grey) represents a small portion of a whole prism. (D) 3D Rotation and (E) strain maps, showing the existence of crystalline domains within the “single-crystalline” like biomineral. Adapted from F. Mastropietro et al., Nature Materials (2017).

References :
[1] F. Mastropietro, P. Godard, M. Burghammer, C. Chevallard, J. Daillant, J. Duboisset, M. Allain, P. Guenoun, J. Nouet, V. Chamard, Revealing crystalline domains in a mollusc shell “single-crystalline” prism, Nature Materials (à paraître).
[2] P. Godard et al., Nature Communications 2, 568 (2011).
[3] S. O. Hruszkewycz, et al., Nature Materials 16, 244 (2017).

Link to other CNRS articles :
- www.cnrs.fr/insis/recherche/actualites/cristal-ptychographie.htm
- www.cnrs.fr/insis/recherche/actualites/2016/12/nanostructures-cristallines.htm->www.cnrs.fr/insis/recherche/actualites/2016/12/nanostructures-cristallines.htm]
- www.cnrs.fr/insis/international-europe/erc/consolidator/virginie-chamard.htm

Partners :
Institut Fresnel (CNRS Marseille), NIMBE (CEA-CNRS Gif-Sur-Yvette), GEOPS (Université Paris Saclay), Synchrotron Soleil (Gif-Sur-Yvette), ESRF (Grenoble).

Contact :
Virginie Chamard, Equipe Comix (Institut Fresnel)
Tel 04 91 28 28 37 – virginie.chamard chez fresnel.fr

Corinne Chevallard, NIMBE (CEA-CNRS)
Tel 01 69 08 52 23 – corinne.chavallard chez cea.fr


A new plasma assisted electron beam deposition machine in Espace Photonique

Within the framework of a project financed by the city of Marseille, the Thin Film Research team of Institut Fresnel has just installed a new Plasma assisted electron beam deposition machine (Bühler SYRUSpro 710) within the Espace Photonique. This AMU technological platform is already equipped with several state-of-the-art machines (e.g. Bühler HELIOS and Bühler SYRUSpro 710) and this new acquisition will help for the development of new and innovative thin film-based components. This machine will be dedicated to the deposition thin films made of infrared materials and to the development of thin layers made of unconventional materials such as phase changing materials (e.g. chalcogenides). In particular, it will enable us to develop broadband antireflection coatings [1.5-15] μm (R&T CNES project), volume structured components (DGA thesis) or optical metasurfaces (Multiwave-funded CIFRE thesis).

Contact RCMO Team : Julien Lumeau
Contact Marseille CityHall : Christophe VOLPE, Office "Immobilier d’Entreprises et Enseignement Supérieur Recherche, Ville de Marseille" - www.marseille.fr


Researchers of the MOSAIC team at Institut Fresnel have demonstrated the possibility to image, at sub-second time scales, the orientational dynamics of lipids in artificial and cell membranes, without the use of any fluorescence labels.
The gain in imaging rate with respect to other techniques is of a few orders of magnitude ; those methods required indeed minutes to form an orientational image of a few hundreds of micrometers in size.

Figure

The optical microscopy method used in the present work records nonlinear coherent Raman scattering signals, in the form of stimulated Raman scattering (SRS) or coherent anti-Stokes Raman scattering (CARS). Those signals originate from the resonant interaction of two pulsed beams with molecular vibrations, here targetting the CH bonds of membrane lipids. Matthias Hofer, Naveen Kumar Balla and Sophie Brasselet have used the lock-in detection method usually implemented for detecting modulated signals in SRS, which exploits modulation transfer from one of the applied incident beam to the other. Here they provided an incident modulation, not anymore in intensity, but rather in polarization. Polarized signals are sensitive to molecular orientations, therefore the obtained modulation is now the signature of molecules being aligned. This scheme has permitted to determine, for each pixel of the image at a rate of 50 microsecond per pixel, both angular distribution width and mean orientation, which are characteristics of molecular organization in the measured lipid membranes at the sub-micrometric scale.

Those signals are rich in information for fundamental and applied biomedical purposes, in particular in tissues such as myelin, a multilayer lipid structure which surrounds and protects our axons. This layered structure is highly perturbed when neurodegenerative diseases develop, such as in Alzheimer’s or multiple sclerosis. This technique could provide early detection of myelin membranes loss of adhesion and detachment, well before they can be visualized at a macroscopic scale. A demonstration of feasability has been recently performed in myelin in the mouse spinal cord, in a work submitted in collaboration with Franck Dbarbieux, INT Marseille.

Reference : M. Hofer, N.K. Balla, S. Brasselet, High speed polarization resolved Coherent Raman Scattering imaging, Optica Vol. 4, Issue 7, pp. 795-801 (2017) https://doi.org/10.1364/OPTICA.4.000795

See also : P. Gasecka, A. Jaouen, F.-Z. Bioud, H. Barbosa de Aguiar, J. Duboisset, P. Ferrand, H. Rigneault, N. Balla, F. Debarbieux, S. Brasselet, Degradation of molecular organization of myelin lipids in autoimmune demyelination probed by polarization resolved nonlinear vibrational microscopy, BioRxiV : https://doi.org/10.1101/105965

Contact : Sophie Brasselet- MOSAIC, sophie.brasselet chez fresnel.fr


Deux lauréats ERC Consolidator pour l’Institut Fresnel


L’appel ERC Consolidator Grants du Conseil européen de la recherche récompense des chercheurs d’excellence ayant entre sept à douze ans d’expérience après leur thèse. Deux chercheurs de l’Institut Fresnel viennent d’obtenir ce financement s’élevant à environ 2 millions d’euros pour une période de cinq ans.

Virginie Chamard est responsable de l’équipe COMiX. Son projet « 3D-BioMat : Deciphering biomineralization mechanisms through 3D explorations of mesoscale crystalline structure in calcareous biomaterials » propose d’avancer dans la compréhension des processus de biominéralisation grâce au développement d’une nouvelle microscopie aux rayons X, en collaboration avec l’Ifremer (Polynésie Française) et le NIMBE (CNRS/CEA, Saclay).

Site web de l’équipe : COMIX


Jérôme Wenger travaille dans l’équipe MOSAIC. Son projet intitulé « TryptoBoost : Boosting tryptophan fluorescence with optical nanoantennas to watch label-free protein dynamics with single molecule resolution at high concentration » vise à étudier les dynamiques des interactions chimiques de protéines avec de nouveaux outils de microscopie et spectroscopie optiques.

Site web du chercheur : www.jeromewenger.com


Crystalline materials : imaging rapidly and efficiently


A new x-ray microscopy, three-dimensional, quantitative and highly-resolved, x-ray microscopy to explore crystalline nanostructures



Understanding shell growth, controlling the optical properties of semiconductors, or even improving the electrical performance of metallic materials are among the many scientific challenges that require knowing the fine properties of crystals at local scales. Due to their long penetration depth, X-rays allows us to probe the inside of a crystal. But producing a quantitative 3D image - providing crystalline strain field information, for instance - with nano-scale resolution remains extremely difficult as a result of the poor efficiency of the available lenses at these wavelengths.
The new approach developed by a Franco-American team and published in Nature Materials greatly simplifies and speeds up the process.

Over the last several years, a so-called lens-less microscopy has emerged : an image of the crystalline properties is retrieved from the diffracted intensities, and numerical methods are used in place of the lenses. To perform such an experiment, the x-ray beam must be coherent, as in the light delivered by a laser. However, the coherence at even the world’s brightest synchrotron x-ray sources is imperfect, such that the size of the sample that can be imaged with lens-less microscopy is typically of the order of a few microns. This hurdle has been cleared in 2011 by the team of V. Chamard at Institut Fresnel (Marseille, France) by demonstrating the possibility to extend arbitrarily the field of view without degrading the resolution.

This microscopy called Bragg ptychography leverages the spatial dependence of the diffraction patterns measured when a nano-focused x-ray beam is scanned along the sample surface. For each position, the 2D
diffraction pattern is recorded. The scanning step, much smaller than the size of the beam spot, produces a strong redundancy in the collected information that enables robust image reconstructions of the sample with new inversion algorithms. Furthermore, three-dimensional information is gained through a tomographic acquisition of the diffracted intensities. Typically, one must measure several hundreds diffraction measurements finely spaced in angle for each beam position on the sample. However, this approach leads to prohibitive total acquisition times (a few tens of hours),

and imposes strong measurement constraints that require specialized experimental set-ups (which only a few beamlines are able to provide), thus preventing the widespread adoption of Bragg ptychography in the scientific community.

The new approach, proposed jointly by researchers from Institut Fresnel (France) and the Argonne National Laboratory (US) greatly simplifies and speeds up this process. Indeed, a huge quantity of information is encoded by the scanning of the beam along the sample, so much so that it becomes possible to perform the measurement at a single viewing angle provided that the intersection between incident diffracted beams is spatially sufficiently well defined. This is indeed the case in Bragg ptychography. The introduction of a modified inversion algorithm gives access to this 3D information in a new and unique way – two dimensions arise from the diffracted signal and one dimension results from the spatial scanning. The new approach, called back-projection Bragg ptychography, marks a conceptual turning point in x-ray microscopy devoted to crystalline materials. The reduction of the total acquisition time, of about a factor 100, and the simplification of the geometry will enable explorations of complex crystalline materials that were not possible to date over a wide range of research areas such as life science and microelectronics.

References :
S. O. Hruszkewycz, M. Allain, M. V. Holt, C. E. Murray, J. R. Holt, P. H. Fuoss and V. Chamard, High-resolution three-dimensional structural microscopy by single-angle Bragg ptychography, Nature Materials 15, December 2016

Contact :
- Virginie Chamard, Institut Fresnel, Equipe Comix

- S. O. Hruszkewycz, Argonne National Laboratory, USA

Other CNRS Links :

- Actualités Scientifiques de l’INSIS, December 20, 2016 - www.cnrs.fr/insis
- "Relations internationales et Europe - ERC", Les Lauréats INSIS 2016 - Consolidator Grants, Virginie Chamard


A new route for looking deeper and brighter in biological tissues

Biological tissues are strongly scattering media, and as such, imaging with high resolution is still remarkably shallow. In particular, multiphoton imaging is strongly based on ballistic light (non-scattered, direction preserved). Because ballistic light intensity decreases exponentially in scattering media, it poses considerable challenges for imaging. Nevertheless, researchers recently found new ways to perform ultradeep imaging, with sub-cellular resolution, by recylcling scattered light itself. Building on these previous work, however exploiting an alternative strategy, we demonstrate record 4000-fold enhancement of nonlinear signal after scattering media, thus enabling highly contrasted nonlinear imaging of biological tissues (collagen fibers).

These remarkable results are possible because of the complex interference pattern arising from multiple scattering phenomena : the speckle. One can “reverse” the complex interference of the speckle into a deterministic shape, e.g. a bright focus. This focus is achieved by using various algorithms which are aided by a feedback mechanism. Traditionally, the feedback for nonlinear imaging is the nonlinear signal itself, which is dim and thus slow. In the new strategy proposed, we exploit the overwhelming linearly scattered light, in opposition to the traditional approach, as a feedback to achieve faster focusing capabilities.

Article :
http://journals.aps.org/pra/abstract/10.1103/PhysRevA.94.043830

Reference :
"Enhanced nonlinear imaging through scattering media using transmission-matrix-based wave-front shaping"

Hilton B. de Aguiar1,*, Sylvain Gigan2, and Sophie Brasselet1,†
Phys. Rev. A 94, 043830 – Published 18 October 2016

1Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249, 13013 Marseille, France
2Laboratoire Kastler Brossel, ENS-PSL Research University, CNRS, UPMC Sorbonne Universités, Collège de France, 24 rue Lhomond, 75005 Paris, France

Contact : h.aguiar chez phys.ens.fr - sophie.brasselet chez fresnel.fr


RCMO


Controlling light scattering and emission with silicon nanoparticles

Light can resonantly interact with subwavelength sized particles, leading to strong enhancements of light scattering and near field intensities in the surrounding of the particles. Metallic nanoparticles have attracted huge efforts over the last 20 years because they host localized surface plasmon resonances, electromagnetic resonances due to the collective oscillation of free electrons. But particles made of insulators can also host electromagnetic resonances, called morphologic or Mie resonances. Theoretical investications carried out at the Institut Fresnel demonstrated that morphologic resonances can yield to the same field enhancements than those yielded by plasmonics particles [1].

A research consortium which includes 2 laboratories of Marseille (Institut Fresnel & CINAM) has recently used the morphologic resonances in dielectric particles made of silicon to enhance to detect individual fluorescent molecules and to imprint colored images without pigments on a surface. Individual fluorescent molecules were observed in a 20 nm nanogap separating 2 silicon particles where the light intensity is strongly enhanced. Dielectric antennas were designed at the Institut Fresnel before being fabricated by the technological platforms hosted by the Institut Fresnel (Photonic space) and by CINAM (Planète) for the coating of the silicon layer and for the lithography and etching of the silicon antennas respectively. The coupling between the 2 silicon particles permits to create a detection volume of the fluorescent signal about one hundred zeptolitres (1 zL=10-21 L) (see the figure on the left). The average number of probed molecules in this volume is decreased by 3600× and becomes smaller than unity while the fluorescent signal is increased by more than 200× [2]. The morphologic resonances in silicon particles have also been used to imprint coloured images without pigment. The resonance frequency depending on the size of the shape of the particle, a palette of structural colours was created simply by moddifying the diameter of the particles. The interest of this technique was highlighted by reproducing a Mondrian’s painting at a 1:1200 scale thanks to silicon particles etched on a glass substrate (see the figure on the right) [3].

These recent advances have been performed without exciting surface plasmon resonances, and by using dielectric materials only. Silicon is ubiquitous in microelectronics and these results in nanophotonics pave the way to bridge the gap between resonant nanophotonics and opto-electronic devices based on silicon technology.


Figure : Gauche : Plateforme de détection moléculaire constituée de 2 particules de Si séparées par un interstice de 20 nm permettant d’exalter et de détecter le signal de fluorescence de molécules individuelles. Droite : Toile de Mondrian reproduite à l’aide de particules de Si. La coloration de ces particules résulte de l’interaction résonante avec la lumière. La couleur est contrôlée par la morphologie des particules
Références :
[1] « Plasmonics » with dielectrics, Optics & Photonics News, February 2016.
[2] Nano Lett. 16, 5143–5151 (2016). Doi : 10.1021/acs.nanolett.6b02076
[3] ACS Nano 10, 7761–7767 (2016). Doi : 10.1021/acsnano.6b03207

Contact Chercheur :
Nicolas BONOD – Institut Fresnel – Tel 04 91 28 28 35


Gold nanoparticles to maintain liquid water at 200°C at ambient pressure
Hydrothermal synthesis at ambient pressure using gold nanoparticles as nanosources of heat
Image de synthèse représentant des microcristaux obtenus par voie hydrothermale sur un tapis de nanoparticules d'or agissant comme nanosources de chaleur sous illumination laser.Artistic view of microcrystals obtained by hydrothermal synthesis using a layer of gold nanoparticles acting as nanosources of heat under laser illumination. In chemical synthesis, hydrothermal reactions involve liquid water between 100°C and 200°C as a solvent. In order to maintain a liquid state at such high temperatures, one has to use a pressure chamber, named an autoclave. This very common approach in chemistry suffers from many limitations, in particular because the reaction medium is closed.

Our researchers have demonstrated the possibility to conduct hydrothermal chemical reactions in an open medium, at ambient pressure, without boiling until 200°C. Such experimental conditions have been obtained at the microscopic scale using gold nanoparticles deposited on a glass substrate and locally heated using an optical microscope and a laser illumination. The absence of boiling up to 230°C and the persistence of a metastable state of water come from the natural absence of nucleation centres in the samples (such as microscopic scratches, dust and roughness).

The chemical reaction consists of the formation of microscopic crystals of indium hydroxide from a solution of indium chloride at 200°C in an aqueous solution, a textbook case in hydrothermal synthesis. Apart from the absence of boiling even at 200°C, other singular observations and interesting benefits have been evidenced, such as kinetics that are 1000 to 10000 times faster than in autoclaves.

This new chemical synthesis technique offers several advantages. As the medium is open, it is possible to add reactants during the reaction. Formation of products can also be observed using optical microscopy means. Finally, this techniques makes it possible as well to spatially structure the growth of solid products on a substrate using a laser beam, opening the path for new applications in micro and nanofabrication.

The concept was imagined by Guillaume Baffou, CNRS research scientist, and the experiments have been conducted by Hadrien Robert, Ph.D. student.
The gold nanoparticle samples have been fabricated by the teams of Julien Polleux (Max Plack Institute, Martinsried, Germany) and Romain Quidant (ICFO, Barcelona, Spain).


Références :
Light-Assisted Solvothermal Chemistry Using Plasmonic Nanoparticles
H. M. L. Robert, F. Kundrat, E. Bermúdez-Ureña, H. Rigneault, S. Monneret, R. Quidant, J. Polleux, and G. Baffou

ACS Omega

ACS Omega 1, 2 (juillet 2016)
DOI : 10.1021/acsomega.6b00019

Contact : Guillaume BAFFOU, CNRS research scientist MOSAIC group, Médaille de bronze 2015 du CNRS


Far-field diffraction microscopy at λ/10 resolution

Researchers of Institut Fresnel in Marseille and LPN Marcoussis

Published in OPTICA Vol 3, N°6, June 2016
Reference
Ting Zhang, Charankumar Godavarthi, Patrick Chaumet, Guillaume Maire, Hugues Giovannini, Anne Talneau, Marc Allain, Kamal Belkebir and Anne Sentenac
"Far-field diffraction microscopy at λ/10 resolution"

Tomographic diffraction microscopy is a three-dimensional quantitative optical imaging technique in which the sample is numerically reconstructed from tens of holograms recorded under different angles of incidence. We show that combining the measurement of the amplitude, the phase, and the polarization of the field scattered by the sample with an approximate knowledge of the sample permittivity allows reconstruction of spatially complex samples up to 50 nm resolution. This technique should be particularly useful for imaging objects made of known materials.

Optica - June 2016


Contact : Anne Sentenac, Researcher CNRS, SEMO Group - Phone : +334 91 28 27 90


Identify the good vibrations of molecules

Researchers at the Institut Fresnel in Marseille have developed an imaging technique to determine directly the organization of molecules in the material, and so reveal its structure at the molecular level. The measured signal is not only sensitive to the presence of the molecule but also specific in the way it vibrates, providing structural information previously untapped.

In an article published on 18 May 2016 in the journal Nature Communications, they describe how to shape the polarization of electromagnetic fields to specifically stimulate certain molecular vibrational modes. This method is based on the nonlinear coherent Raman process CARS (coherent anti-Stokes Raman scattering) and group theory concepts. Very simple to implement, this advanced technique is another step in label free microscopy. It offers new perspectives in biology and for biomedical diagnostics, areas where the optical microscope is an essential instrument.

Figure : Imaging of carbon-carbon bonds of myelin in a side section of spinal cord.
The circular structures correspond to the myelin sheaths surrounding the dendrites. The brightness of the image corresponds to the density of carbon-carbon bonds, the color scale corresponds to the organization of the bonds : the isotropic vibration are in red, the uni-directional vibration are in blue.
This image is obtained in a single acquisition without fluorescent probes, and thus allows to provide structural information on the organization of molecules in the sample (image 30 × 30 microns).

Reference : Carsten Cleff, Alicja Gasecka, Patrick ferrand, Hervé Rigneault, Sophie Brasselet et Julien Duboisset
Direct imaging of molecular symmetry by coherent anti-Stokes Raman scattering
Nature Communications 7, Article number 11562 (18 mai 2016)

Contact : Julien Duboisset, Maître de Conférences, Aix-Marseille University, Phone : +334 91 28 80 49


Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum

Reference : M. Lequime, S Liukaityte, M. Zerrad, C. Amra, “Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum,” Opt. Express 23, 26863-26878 (2015).
Selected by Advanced in Enginnering as a Key Scientific Article

See also the paper on NKT Photonics website "EXTREME optical metrology : First broadband measurement of a 12 optical density with 1 nm resolution".

More details on INSIS website (CNRS)

Contact : Michel Lequime and Myriam Zerrad


"Three dimensional nanometer localization of nanoparticles to enhance super-resolution microscopy" Nature Communications du 27 juillet 2015


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