Towards Reliable and Quantitative Surface‐Enhanced Raman Scattering (SERS): From Key Parameters to Good Analytical Practice

Experimental results obtained in different laboratories world‐wide by researchers using surface‐enhanced Raman scattering (SERS) can differ significantly. We, an international team of scientists with long‐standing expertise in SERS, address this issue from our perspective by presenting considerations on reliable and quantitative SERS. The central idea of this joint effort is to highlight key parameters and pitfalls that are often encountered in the literature. To that end, we provide here a series of recommendations on: a) the characterization of solid and colloidal SERS substrates by correlative electron and optical microscopy and spectroscopy, b) on the determination of the SERS enhancement factor (EF), including suitable Raman reporter/probe molecules, and finally on c) good analytical practice. We hope that both newcomers and specialists will benefit from these recommendations to increase the inter‐laboratory comparability of experimental SERS results and further establish SERS as an analytical tool.Peer Reviewe

Charge Transfer and Tunable Ambipolar Effect Induced by Assembly of Cu (II) Binuclear Complexes on Carbon Nanotube Field Effect Transistor Devices

International audienceAssembly of paramagnetic Cu2 complexes with a Schiff base scaffold possessing extended electron delocalization together with a quasi-planar structure onto carbon nanotubes induces a diameter-selective charge transfer from the complex to the nanotubes leading to an interestingly large and tunable ambipolar effect. We used complementary techniques such as electron paramagnetic resonance, absorption spectroscopy, and photoluminescence to ensure the success of the assembly process and the integrity of the complex in the nanohybrid. We carried out density functional theory type calculations to rationalize the experimental results,evidencing the selective enhanced interaction of the metal complexes with one type of nanotube

The Dichotomous Pattern of IL-12R and IL-23R Expression Elucidates the Role of IL-12 and IL-23 in Inflammation

IL-12 and IL-23 cytokines respectively drive Th1 and Th17 type responses. Yet, little is known regarding the biology of these receptors. As the IL-12 and IL-23 receptors share a common subunit, it has been assumed that these receptors are co-expressed. Surprisingly, we find that the expression of each of these receptors is restricted to specific cell types, in both mouse and human. Indeed, although IL-12Rβ2 is expressed by NK cells and a subset of γδ T cells, the expression of IL-23R is restricted to specific T cell subsets, a small number of B cells and innate lymphoid cells. By exploiting an IL-12- and IL-23-dependent mouse model of innate inflammation, we demonstrate an intricate interplay between IL-12Rβ2 NK cells and IL-23R innate lymphoid cells with respectively dominant roles in the regulation of systemic versus local inflammatory responses. Together, these findings support an unforeseen lineage-specific dichotomy in the in vivo role of both the IL-12 and IL-23 pathways in pathological inflammatory states, which may allow more accurate dissection of the roles of these receptors in chronic inflammatory diseases in humans

Comparative transcriptomics of drought responses in Populus: a meta-analysis of genome-wide expression profiling in mature leaves and root apices across two genotypes

<p>Abstract</p> <p>Background</p> <p>Comparative genomics has emerged as a promising means of unravelling the molecular networks underlying complex traits such as drought tolerance. Here we assess the genotype-dependent component of the drought-induced transcriptome response in two poplar genotypes differing in drought tolerance. Drought-induced responses were analysed in leaves and root apices and were compared with available transcriptome data from other <it>Populus </it>species.</p> <p>Results</p> <p>Using a multi-species designed microarray, a genomic DNA-based selection of probesets provided an unambiguous between-genotype comparison. Analyses of functional group enrichment enabled the extraction of processes physiologically relevant to drought response. The drought-driven changes in gene expression occurring in root apices were consistent across treatments and genotypes. For mature leaves, the transcriptome response varied weakly but in accordance with the duration of water deficit. A differential clustering algorithm revealed similar and divergent gene co-expression patterns among the two genotypes. Since moderate stress levels induced similar physiological responses in both genotypes, the genotype-dependent transcriptional responses could be considered as intrinsic divergences in genome functioning. Our meta-analysis detected several candidate genes and processes that are differentially regulated in root and leaf, potentially under developmental control, and preferentially involved in early and long-term responses to drought.</p> <p>Conclusions</p> <p>In poplar, the well-known drought-induced activation of sensing and signalling cascades was specific to the early response in leaves but was found to be general in root apices. Comparing our results to what is known in arabidopsis, we found that transcriptional remodelling included signalling and a response to energy deficit in roots in parallel with transcriptional indices of hampered assimilation in leaves, particularly in the drought-sensitive poplar genotype.</p

Purification de Nanotubes de Carbone Mono Paroi. Greffage d'Objets Magnétiques pour des Applications en Spintronique.

Molecular spintronics is an emerging field of molecular electronics that addresses the matter of encoding informations with spins instead of charges. To date, a few devices obtained by break junction techniques have been reported. They allow the investigation of interesting phenomena such as Kondo effect or quantum tunneling of the magnetization. However, quantitative explanation of the transport properties are often limitated by incertainities on the nature of the species within the junction and their relative orientation to the leads. Recently, the use of carbon nanotubes as molecular wire for spintronics transistors has attracted much attention because of their large spin coherence length. The present work aimed at designing adducts based on magnetic objects and single-wall carbon nanotubes for spintronics applications. Their properties have been extensively characterized in bulk material in order to get a detailed picture of the magnetic objects to be assembled in future transistors. To obtain such adducts and study their magnetic properties, one needs to masterize a high quality purification of the carbon nanotubes, that contain about 20% of magnetic impurities in the raw material. We achieved such a purification and suggested a mechanism for the removing of the magnetic impurities. The purified carbon nanotubes have then been functionnalized by magnetic objects, following non-covalent interaction schemes that preserve the electronic properties of the molecular wire. Three magnetic systems have been selected, including polyoxometalate, coordination nanoparticles and complexes bearing large aromatic moieties. In some cases, an electronic communication between the nanotube and the grafted object has been evidenced, leading to a modulation of its magnetic properties. We therefore believe that the adducts we developped in this work are promising systems for spintronics devices.La spintronique moléculaire est un domaine émergeant de l'électronique moléculaire qui s'attache à encoder l'information non plus sous forme de charges électriques mais sous forme de spin. A ce jour, quelques dispositifs magnétiques à base de jonction à cassure ont été décrits. Ils ont permis l'observation de phénomènes intéressants tels que le renversement de l'aimantation d'une molécule aimant ou l'effet Kondo. Cependant, il subsiste généralement des incertitudes sur la nature exacte de l'espèce présente dans la jonction et son orientation relative par rapport aux électrodes, compliquant de ce fait l'interprétation quantitative de ces phénomènes. Récemment, les nanotubes de carbone ont suscité un vif intérêt en tant que composants pour la spintronique moléculaire, du fait de leur grande cohérence de spin. Au cours de ce travail, nous nous sommes attachés à concevoir des adduits nanotube monoparoi – objets magnétiques pour des applications en spintronique. Leurs propriétés ont été extensivement caractérisées afin de connaître avec précision les caractéristiques des objets à introduire dans les futurs transistors. Les nanotubes de carbone commerciaux contiennent environ 20% d'impuretés magnétiques. Pour synthétiser ces adduits et déterminer leurs propriétés magnétiques, nous avons développé une méthode de purification conduisant à de très hauts taux de pureté, et permettant la détection du signal magnétique de molécules greffées sur les nanotubes. Un mécanisme rendant compte de l'élimination des impuretés magnétiques a été proposé. Les nanotubes purifiés ont été fonctionnalisés suivant des schémas non covalents qui préservent l'intégrité des propriétés électroniques des nanotubes. Trois systèmes magnétiques ont été sélectionnés et comprennent des polyoxométalates, des nanoparticules de réseau de coordination et des complexes comportant un large groupement aromatique. Dans certains cas, une communication électronique entre le nanotube et la molécule greffée a pu être mise en évidence, conduisant à une modulation de ses propriétés magnétiques. Ces systèmes constituent des candidats très prometteurs à des applications en spintronique

Purification de Nanotubes de Carbone Mono Paroi. Greffage d'Objets Magnétiques pour des Applications en Spintronique.

Molecular spintronics is an emerging field of molecular electronics that addresses the matter of encoding informations with spins instead of charges. To date, a few devices obtained by break junction techniques have been reported. They allow the investigation of interesting phenomena such as Kondo effect or quantum tunneling of the magnetization. However, quantitative explanation of the transport properties are often limitated by incertainities on the nature of the species within the junction and their relative orientation to the leads. Recently, the use of carbon nanotubes as molecular wire for spintronics transistors has attracted much attention because of their large spin coherence length. The present work aimed at designing adducts based on magnetic objects and single-wall carbon nanotubes for spintronics applications. Their properties have been extensively characterized in bulk material in order to get a detailed picture of the magnetic objects to be assembled in future transistors. To obtain such adducts and study their magnetic properties, one needs to masterize a high quality purification of the carbon nanotubes, that contain about 20% of magnetic impurities in the raw material. We achieved such a purification and suggested a mechanism for the removing of the magnetic impurities. The purified carbon nanotubes have then been functionnalized by magnetic objects, following non-covalent interaction schemes that preserve the electronic properties of the molecular wire. Three magnetic systems have been selected, including polyoxometalate, coordination nanoparticles and complexes bearing large aromatic moieties. In some cases, an electronic communication between the nanotube and the grafted object has been evidenced, leading to a modulation of its magnetic properties. We therefore believe that the adducts we developped in this work are promising systems for spintronics devices.La spintronique moléculaire est un domaine émergeant de l'électronique moléculaire qui s'attache à encoder l'information non plus sous forme de charges électriques mais sous forme de spin. A ce jour, quelques dispositifs magnétiques à base de jonction à cassure ont été décrits. Ils ont permis l'observation de phénomènes intéressants tels que le renversement de l'aimantation d'une molécule aimant ou l'effet Kondo. Cependant, il subsiste généralement des incertitudes sur la nature exacte de l'espèce présente dans la jonction et son orientation relative par rapport aux électrodes, compliquant de ce fait l'interprétation quantitative de ces phénomènes. Récemment, les nanotubes de carbone ont suscité un vif intérêt en tant que composants pour la spintronique moléculaire, du fait de leur grande cohérence de spin. Au cours de ce travail, nous nous sommes attachés à concevoir des adduits nanotube monoparoi – objets magnétiques pour des applications en spintronique. Leurs propriétés ont été extensivement caractérisées afin de connaître avec précision les caractéristiques des objets à introduire dans les futurs transistors. Les nanotubes de carbone commerciaux contiennent environ 20% d'impuretés magnétiques. Pour synthétiser ces adduits et déterminer leurs propriétés magnétiques, nous avons développé une méthode de purification conduisant à de très hauts taux de pureté, et permettant la détection du signal magnétique de molécules greffées sur les nanotubes. Un mécanisme rendant compte de l'élimination des impuretés magnétiques a été proposé. Les nanotubes purifiés ont été fonctionnalisés suivant des schémas non covalents qui préservent l'intégrité des propriétés électroniques des nanotubes. Trois systèmes magnétiques ont été sélectionnés et comprennent des polyoxométalates, des nanoparticules de réseau de coordination et des complexes comportant un large groupement aromatique. Dans certains cas, une communication électronique entre le nanotube et la molécule greffée a pu être mise en évidence, conduisant à une modulation de ses propriétés magnétiques. Ces systèmes constituent des candidats très prometteurs à des applications en spintronique

Purification de nanotubes de carbone mono paroi

La spintronique moléculaire est un domaine émergeant de l électronique moléculaire qui s attache à encoder l information sous forme de spin. A ce jour, quelques dispositifs magnétiques à base de jonction à cassure ont été décrits et ont conduit à l observation de phénomènes intéressants, tels que l effet Kondo. Leur compréhension est cependant entravée par des incertitudes sur la nature des espèces présentes dans la jonction. Les nanotubes de carbone suscitent un vif intérêt en spintronique moléculaire du fait de leur grande cohérence de spin. Ce travail a consisté en la conception d adduits SWNTs objets magnétiques pour des applications en spintronique. Les adduits ont été extensivement caractérisés afin de contôler les propriétés des objets à intégrer dans les futurs transistors. Les SWNTs commerciaux contiennent environ 20% d impuretés magnétiques. Afin d étudier les propriétés magnétiques des adduits, nous avons développé une méthode de purification conduisant à de très hauts taux de pureté, et permettant la détection du signal magnétique de molécules greffées sur les nanotubes. Les SWNTs purifiés ont été fonctionnalisés suivant des schémas non covalents préservant l intégrité des propriétés électroniques des nanotubes. Les systèmes magnétiques considérés comprennent des polyoxométalates, des nanoparticules de réseau de coordination et des complexes comportant un large groupement aromatique. Dans certains cas, une influence des nanotubes sur les propriétés magnétiques des molécules a été mise en évidence. Ces systèmes constituent à ce titre des candidats prometteurs pour applications en spintronique.Molecular spintronics is an emerging field of molecular electronics addressing the encoding of information with spins instead of charges. To date, few devices based on break junction techniques have been reported. They display interesting phenomena such as Kondo effect or quantum tunneling of the magnetization. However, quantitative explanation of the transport properties are often limited by uncertainties on the nature of the species within the junction. Recently, the use of carbon nanotubes as molecular wire for spintronics transistors has attracted much attention because of their large spin coherence length. The present work aimed at assemble magnetic objects on SWNTs for spintronics applications. These assemblies have been extensively characterized in bulk material in order to get a detailed picture of the magnetic objects to be integrated in future transistors. To study their magnetic properties, one needs to achieve a high quality purification of SWNTs, which contain about 20% of magnetic impurities as raw material. We developed such a purification and suggested a mechanism for the removing of magnetic impurities. The purified SWNTs have been functionalized with magnetic objects, following non-covalent schemes that preserve the electronic properties of the molecular wire. Three magnetic systems have been selected, including polyoxometalate, coordination nanoparticles and complexes bearing large aromatic moieties. In some cases, an electronic communication between the nanotube and the grafted object was evidenced, that led to a modulation of its magnetic properties. Hence, the assemblies developed in this work hold great promise for future spintronics devices.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

On the Use of pH Titration to Quantitatively Characterize Colloidal Nanoparticles

International audienceFunctional nanoparticles (NPs) for bioapplications have been achieved, thanks to synthesis providing high quality nanocrystals, efficient procedures for transfer in water, and further conjugation of (bio)active molecules. However, these nanomaterials are still subjected to batch-to-batch variability and investigations of their physicochemical properties and chemical reactivity are still in their infancy. This may be due to lack of a routine, cost-effective, and readily available quantitative method for characterizing functional NPs. In this work, we show that pH titrations can be a powerful tool for investigating the surface properties of charged NPs and quantifying their surface functionalities. We demonstrate how this method can be useful in characterizing the colloidal and chemical stability, composition, and purity of the nanomaterial. The method also shows potential for the optimization of conjugation conditions

How microbial biofilms impact the interactions of Quantum Dots with mineral surfaces?

International audienc