Hierarchical functionalisation of single-wall carbon nanotubes with DNA through positively charged pyrene

A simple and efficient method to link reversibly DNA to SWNTs via electrostatic interaction is reported. The DNA/nanotube hybrids are characterised by a combination of gel electrophoresis and AFM

Signature of gate-tunable magnetism in graphene grafted with Pt-porphyrins

Inducing magnetism in graphene holds great promises, such as controlling the exchange interaction with a gate electrode and generating exotic magnetic phases. Coating graphene with magnetic molecules or atoms has so far mostly lead to decreased graphene mobility. In the present work, we show that Pt-porphyrins adsorbed on graphene lead to an enhanced mobility and to gate-dependent magnetism. We report that porphyrins can be donor or acceptor, depending on graphene s initial doping. The porphyrins transfer charge and ionize around the charged impurities on graphene, decreasing the graphene doping and increasing its mobility. In addition, ionized porphyrins carry a magnetic moment. Using the sensitivity of mesoscopic transport to magnetism, in particular the superconducting proximity effect and conductance fluctuations, we explore the magnetic order induced in graphene by the interacting magnetic moments of the ionized porphyrins. Among the signatures of magnetism, we find two-terminal-magnetoresistance fluctuations with an odd component, a tell-tale sign of time reversal symmetry breaking at zero field, that does not exist in uncoated graphene sample. When graphene is connected to superconducting electrodes, the induced magnetism leads to a gate-voltage-dependent suppression of the supercurrent, modified magnetic interference patterns, and gate-voltage-dependent magnetic hysteresis. The magnetic signatures are greatest for long superconductor graphene superconductor junctions and for samples with the highest initial doping, compatible with a greater number of ionized and thus magnetic porphyrins. Our findings suggest that long-range magnetism is induced through graphene by the ionized porphyrins magnetic moment. This magnetic interaction is controlled by the density of carriers in graphene, a tunability that could be exploited in spintronic applications

Covalent grafting onto self-adhesive surfaces based on aryldiazonium salt seed layers

International audienceThe chemistry of aryldiazonium salts has been thoroughly used in recent years to graft in a very simple and robust way ultrathin polyphenylene-like films on a broad range of surfaces. We show here that the same chemistry can be used to obtain self-adhesive surfaces. This target was reached in a simple way by coating various surfaces with chemisorbed organic films containing active aryldiazonium salts. These self-adhesive surfaces are then put into contact with various species (molecules, polymers, nanoparticles, nanotubes, graphene flakes, etc.) that react either spontaneously or under activation with the immobilized aryldiazonium salts. Our self-adhesive surfaces were synthesized following a simple aqueous two-step protocol based on p-phenylenediamine diazotisation. The first diazotisation step results in the robust grafting of thin polyaminophenylene (PAP) layers onto the surface. The second diazotisation step changed the grafted PAP film into a poly-aryldiazonium polymer (PDP) film. The covalent grafting between those self-adhesive surfaces and the target species was achieved by direct contact or by immersion of the self-adhesive surfaces in solution. We present in this preliminary work the grafting of multi-wall carbon nanotubes (MWCNTs), flakes of highly oriented pyrolytic graphite (HOPG), various organic compounds and copper nanoparticles. We also tested these immobilized aryldiazonium salts as electropolymerization initiators for the grafting-to process

Near-field imaging of single walled carbon nanotubes emitting in the telecom wavelength range

International audienceHybrid systems based on carbon nanotubes emitting in the telecom wavelength range and Si-photonic platforms are promising candidates for developing integrated photonic circuits. Here, we consider semiconducting single walled carbon nanotubes (s-SWNTs) emitting around 1300 nm or 1550 nm wavelength. The nanotubes are deposited on quartz substrate for mapping their photoluminescence in hyperspectral near-field microscopy. This method allows for a sub-wavelength resolution in detecting the spatial distribution of the emission of single s-SWNTs at room temperature. Optical signature delocalized over several micrometers is observed, thus denoting the high quality of the produced carbon nanotubes on a wide range of tube diameters. Noteworthy, the presence of both nanotube bundles and distinct s-SWNT chiralities is uncovered

Turtle Carapace Anomalies: The Roles of Genetic Diversity and Environment

Background: Phenotypic anomalies are common in wild populations and multiple genetic, biotic and abiotic factors might contribute to their formation. Turtles are excellent models for the study of developmental instability because anomalies are easily detected in the form of malformations, additions, or reductions in the number of scutes or scales. Methodology/Principal Findings: In this study, we integrated field observations, manipulative experiments, and climatic and genetic approaches to investigate the origin of carapace scute anomalies across Iberian populations of the European pond turtle, Emys orbicularis. The proportion of anomalous individuals varied from 3 % to 69 % in local populations, with increasing frequency of anomalies in northern regions. We found no significant effect of climatic and soil moisture, or climatic temperature on the occurrence of anomalies. However, lower genetic diversity and inbreeding were good predictors of the prevalence of scute anomalies among populations. Both decreasing genetic diversity and increasing proportion of anomalous individuals in northern parts of the Iberian distribution may be linked to recolonization events from the Southern Pleistocene refugium. Conclusions/Significance: Overall, our results suggest that developmental instability in turtle carapace formation might be caused, at least in part, by genetic factors, although the influence of environmental factors affecting the developmental stability of turtle carapace cannot be ruled out. Further studies of the effects of environmental factors, pollutants an

DNA Metallization Processes and NanoelectronicsNanopackaging in "From Nanomaterials to the Atomic Scale. Advances in Atom and Single Molecule Machines"

International audienceDNA fascinates for its exceptional assembling properties which make it an ideal candidate to encode instructions for nano-scale assembly. However, to utilize DNA not only as a positioning scaffold but also for electrical interconnections, it is pragmatically envisioned to metallize it. Here, an overview of DNA metallization processes is presente