Exploiting the localized surface plasmon modes in gold triangular nanoparticles for sensing applications

In this study we investigate and exploit, for optical sensing, the surface plasmon excitation in gold triangular nanoparticles with high aspect ratios (i.e., the ratio of the edge length of the triangles with the height) prepared by nanosphere lithography. As shown previously, the shape and size of these nanoparticles were used to tune their optical properties, monitored by far field extinction spectroscopy. Interestingly, several localized surface plasmon resonances were detected in the visible and near infrared regions and were attributed to dipole and quadrupole modes. These modes, identified from numerical simulations, "red-shift'' as the aspect ratio of the particles increases. The plasmon modes observed for larger triangles exhibit unexpected sensitivity with a change in the refractive index. From experiments and numerical simulations, this higher sensitivity has been attributed to an increase of the local field enhancement for sharper tips. This new effect can provide important information for the design of particles as building blocks for sensing applications

The centrosome neither persistently leads migration nor determines the site of axonogenesis in migrating neurons in vivo

In vivo analysis of subcellular dynamics in the zebrafish cerebellum provides new insights into centrosome positioning during vertebrate brain differentiation

Surfaces PDMS structurées et/ou décorées par des nanoparticules (vers des propriétés optiques et de mouillage modulables)

Le potentiel du polydiméthylsiloxane (PDMS), élastomère transparent et déformable réversiblement en temps réel, est mis en avant dans ce travail comme substrat fonctionnel dans le domaine de l optique et du mouillage. Dans une première partie, nous avons développé des surfaces de PDMS ridées à l aide d instabilités de flambage, de longueurs d onde ( ) et d amplitude (A) variables et contrôlées, puis nous avons organisé sélectivement des nano-objets sur cette texturation de surface avec afin d en moduler la physico-chimie. Dans une seconde partie, la génération, in situ, de nano-plots/nanoparticules d or et d argent à la surface de verre et de PDMS a été étudiée et caractérisée d un point de vue optique.The polydimethylsiloxane (PDMS), a transparent and stretchable elastomer, is put forward in this work as a functional substrate in the field of optics and wetting. In the first part, we have developed wrinkled PDMS surfaces via controlled buckling instabilities. We were able to tune both the wavelength ( ) and the amplitude (A) of the structuration on a large length scale. We have then selectively organized some nanoparticles the textured surfaces in order to modulate its physical-chemistry. In the second part, in situ generation of gold and silver nanoparticles/plots has been developed and studied both on glass PDMS surfaces and subsequently characterized optically.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Process Migration based on Gobelins Distributed Shared Memory

Clusters are attractive for executing sequential and parallel applications. However, there is a need to design a cluster distributed operating system to provide a Single System Image. A cluster operating system providing both a DSM system and load balancing is attractive for efficiently executing a workload of sequential applications and shared memory parallel applications. Gobelins is a distributed operating system dedicated to clusters that provides both a DSM system and a process migration mechanism to support load balancing. In this paper, we present the implementation of Gobelins process migration mechanism which exploits Gobelins kernel level DSM system. We show that Gobelins DSM allows to implement simply an efficient migration mechanism, that can be used to move processes or threads among cluster nodes. A prototype of Gobelins has been implemented. Some performance results are presented in this paper

Shaping light spectra and field profiles in metal-coated monolayers of etched microspheres

Hybrid colloidal plasmonic-photonic crystals (HPPCs) are known for their interesting optical properties, which are relevant both fundamentally and for their applicative potential. The optical response of HPPCs is easily tunable from the visible to the infraredspectral range, while their fabrication, based on colloidal self-assembly, keeps production costs rather low. Both arguments make HPPCs a class of attractive functional materials. Here, we explore the optical properties of HPPCs obtained by gradual etching of a hexagonal closepacked monolayer of polystyrene microspheres, subsequently covered by a thin metal layer. We analyze the optical transmission characteristics of these etched colloidal crystals and HPPCs as a function of the etching degree. Finite-difference time-domain simulations allowed us to explain the correlations between the observed optical response and morphology. The transmission gap in bare colloidal crystals can be blue-shifted up to at least 50 nm, and its depth increased by more than 20%. In HPPCs on the other hand, it is possible to tune not only the wavelength of the enhanced plasmonic fields, but also their locations within the nanostructure. Thus, both spectra and near-field profiles can be fine-tuned in a controlledmanner by plasma etching in these hybrid plasmonic-photonic structures, expanding the current understanding of the physical working principles of HPPCs and their applications

Nat. Nanotechnol.

Optoelectronic effects differentiating absorption of right and left circularly polarized photons in thin films of chiral materials are typically prohibitively small for their direct photocurrent observation. Chiral metasurfaces increase the electronic sensitivity to circular polarization, but their out-of-plane architecture entails manufacturing and performance tradeoffs. Here, we show that nanoporous thin films of chiral nanoparticles enable high sensitivity to circular polarization due to light-induced polarization-dependent ion accumulation at nanoparticle interfaces. Self-assembled multilayers of gold nanoparticles modified with L-phenylalanine generate a photocurrent under righthanded circularly polarized light as high as 2.41 times higher than under left-handed circularly polarized light. The strong plasmonic coupling between the multiple nanoparticles producing planar chiroplasmonic modes facilitates the ejection of electrons. Concomitantly, a thick layer of enantiopure phenylalanine facilitates their subsequent entrapment at the membrane-electrolyte interface. Demonstrated detection of light ellipticity with equal sensitivity at all incident angles mimics phenomenological aspects of polarization vision in marine animals. The simplicity of self-assembly 2 and sensitivity of polarization detection found in optoionic membranes opens the door to a family of miniaturized fluidic devices for chiral photonics