Two-photon photopolymerization directly initiated by spiropyran photochromic molecules

Here, we report the ability of spiropyrans to initiate two-photon polymerization (TPP) for the first time in the literature. The comparison and synergies between the spiropyran photochromic molecule of interest, namely 6-nitro-BIPS, and well-known photoinitiators of radical photopolymerization have been studied. The spiropyran (SPy) molecule can initiate TPP in the presence of trifunctional acrylic monomers and create true 3D structures. The comparison with Irgacure 819, a well-known Type-I photoinitiator, shows that SPy has a comparable capability for TPP. In addition, the combination of SPy with methyl diethanolamine increased the reactivity of both one- and two-photon polymerizations. In the last section, we discuss which SPy isomer is the active photochromic species capable of generating radicals for initiating two-photon polymerization

Plasmon resonance optical tuning based on photosensitive composite structures

This paper reports a numerical investigation of a periodic metallic structure sandwiched between two quartz plates. The volume comprised between the quartz plates and the metallic structure is infiltrated by a mixture of azo-dye-doped liquid crystal. The exposure to a low power visible light beam modifies the azo dye molecular configuration, thus allowing the wavelength shift of the resonance of the system. The wavelength shift depends on the geometry of the periodic structure and it also depends on the intensity of the visible light beam

In-situ 3D Micro-sensor Model using Embedded Plasmonic Island for Biosensors

The design of the microsensor system for biosensors using the plasmonic island is proposed. The sensor head is formed by the stacked layers of silicon-graphene-gold materials. The dual-mode operations of the sensor can be performed using the relationship of the changes between the electron mobility and optical phase, where the exciting environment can be light intensity (phase), electrical transient, heat, pressure, flavour and smoke, The change in light phase (intensity) in silicon and conductivity (mobility) in gold layers cause change in the output measurands. The design and simulation interpretation of the sensor is presented. The sensor manipulation using the MCM arrangement is simulated and interpreted for biosensor applications 3D imaging can also be applied to the MCM function, where the 3D in situ sensor function is possible. The sensor sensitivity of 2.0 × 10−21 cm2 V−1 s−1 (mW)−1 via simulation is obtained

Nanoporous plasmonic metamaterials

We review different routes for the generation of nanoporous metallic foams and films exhibiting well-defined pore size and short-range order. Dealloying and templating allows the generation of both two- and three-dimensional structures which promise a well defined plasmonic response determined by material constituents and porosity. Viewed in the context of metamaterials, the ease of fabrication of samples covering macroscopic dimensions is highly promising, and suggests more in-depth investigations of the plasmonic and photonic properties of this material system for photonic applications

Label-Free Optical Single-Molecule Micro- and Nanosensors

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordLabel-free optical sensor systems have emerged that exhibit extraordinary sensitivity for detecting physical, chemical, and biological entities at the micro/nanoscale. Particularly exciting is the detection and analysis of molecules, on miniature optical devices that have many possible applications in health, environment, and security. These micro- and nanosensors have now reached a sensitivity level that allows for the detection and analysis of even single molecules. Their small size enables an exceedingly high sensitivity, and the application of quantum optical measurement techniques can allow the classical limits of detection to be approached or surpassed. The new class of label-free micro- and nanosensors allows dynamic processes at the single-molecule level to be observed directly with light. By virtue of their small interaction length, these micro- and nanosensors probe light–matter interactions over a dynamic range often inaccessible by other optical techniques. For researchers entering this rapidly advancing field of single-molecule micro- and nanosensors, there is an urgent need for a timely review that covers the most recent developments and that identifies the most exciting opportunities. The focus here is to provide a summary of the recent techniques that have either demonstrated label-free single-molecule detection or claim single-molecule sensitivity.Living Systems Institute, University of Exete

Diffusion Raman exaltée de surface (aspects fondamentaux et détection de la molécule unique)

Au cours des deux dernières décennies, il y a eu un intérêt accru pour la recherche de nouveaux dispositifs de type capteurs pour la détection de très petites quantités de molécules, par exemple, d'intérêt biologique. Les critères importants de tels capteurs sont principalement la grande sensibilité et la sélectivité. Dans ce contexte, la diffusion Raman exaltée de surface (DRES) est considérée comme une technique spectroscopique très sensible et spécifique pour détecter la signature vibrationnelle de molécules, à condition que celles-ci soient absorbées à la surface de nanoparticules métalliques tels que l'or, l'argent ou le cuivre. De telles nanoparticules présentent une résonance plasmon de surface localisée. Les nanoparticules métalliques peuvent être fabriquées par lithographie par nanosphère (LN), par lithographie par faisceau d'électrons (LFE), et par synthèse chimique en solution acqueuse. Les méthodes lithographiques, LN et LFE, permettent de définir précisément la géométrie de la particule. Cependant, l'étape d'évaporation du métal fournit une structure métallique polycristalline, contrairement à la plupart des particules monocristallines fabriquées par synthèse chimique. L'influence de la structure cristalline et de la rugosité de la surface de nanoparticules métalliques sur leurs propriétés optiques reste ainsi une question ouverte, alors que son impact a été clairement établi dans certains cas, par la comparaison de structures fabriquées par synthèse chimique et LFE. Dans ce travail, nous allons présenter une étude détaillée sur l'influence des nano-rugosités de surface de nanoparticules fabriquées par lithographie lectronique sur leurs propriétés optiques (sondé par spectroscopie d'extinction UV-visible), et sur leur réponse optique en champ proche par effet DRES. Bien que les échantillons lithographiques soient de très bons modèles pour l'étude des mécanismes DRES, ils ne sont pas le meilleur candidat pour la détection de molécules uniques. Pour être en mesure de détecter quelques molécules, voire la molécule unique, celles-ci doivent être situées à des endroits de forte exaltation du champ électrique, dits points chauds. Les points chauds sont par nature, très inhomogènes. Généralement moins de 1 % des molécules sont observés, ce qui n'est pas adapté pour les applications de détection. Dans ce travail, nous proposons une stratégie, basé sur l'adsorption sélective de la molécule cible uniquement sur les points chauds, qui nous permet de montrer qu'il est possible de faire de la détection de la molécule unique par effet DRES.Over the two last decades, there has been an increased interest in finding new devices that provide ultrasensitive sensors detection of very small amounts of molecules. Important criteria on such sensors mainly deal with sensitivity and selectivity. In this context, Surface enhanced Raman scattering (SERS) is considered as a very sensitive and selective technique for the detection of the vibrational signature of the molecules provided they are adsorbed at the surface of metallic nanoparticles such as gold, silver or copper. Such kind of nanoparticles differs strongly from the respective bulk material in their optical response for they can exhibit localized surface plasmon resonance (LSPR). Fabrication methods for metal nanoparticles include nanosphere lithography (NL), electron beam lithography (EBL) and the chemical synthesis in liquid media. The lithographie methods, NL and EBL, employ a masking structure to first define the geometry of the nanoparticles that are then grown by, e.g., vacuum deposition of the metal. This process results in a polycrystalline metal structure, in contrast to the mostly single-crystalline particles fabricated by chemical synthesis. The influence of the crystalline structure and surface roughness of metal nanoparticles on their optical properties remains however to some extent a matter of speculation, while its drastic impact was made clear in some cases by the comparison between chernically synthesized and EBL fabricated structures. In this work, we will present a detailed study on the influence of the nanometric surface roughness (NSR) on the far-field optical response of "realistic" lithographie particles, probed by UV-visible extinction spectroscopy, and the near-field response monitored by SERS intensity. Although the lithographie samples are very good models for the investigation of the SERS mechanisms, they are not the best candidate when single (or few) molecules detection is required. To be able to detect only a few molecules, they have to be located at the position of highest enhancements, so called hot-spots (HS). HS are by nature, very inhomogeneous. As a result, typically less than 1% of molecules are observed, which is of course not suitable for sensing applications. In this work, we propose a simple scheme based on selective adsorption of the analyte at the hot-spots only, which in principle allows the detection of every single target molecules.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF