A stellar stream remnant of a globular cluster below the metallicity floor.

Stellar ejecta gradually enrich the gas out of which subsequent stars form, making the least chemically enriched stellar systems direct fossils of structures formed in the early Universe1. Although a few hundred stars with metal content below 1,000th of the solar iron content are known in the Galaxy2-4, none of them inhabit globular clusters, some of the oldest known stellar structures. These show metal content of at least approximately 0.2% of the solar metallicity [Formula: see text]. This metallicity floor appears universal5,6, and it has been proposed that protogalaxies that merged into the galaxies we observe today were simply not massive enough to form clusters that survived to the present day7. Here we report observations of a stellar stream, C-19, whose metallicity is less than 0.05% of the solar metallicity [Formula: see text]. The low metallicity dispersion and the chemical abundances of the C-19 stars show that this stream is the tidal remnant of the most metal-poor globular cluster ever discovered, and is significantly below the purported metallicity floor: clusters with significantly lower metallicities than observed today existed in the past and contributed their stars to the Milky Way halo.

3D Core-Shell TiO2@MnO2 Nanorod Arrays on Microcantilevers for Enhancing the Detection Sensitivity of Chemical Warfare Agents.

Nanostructured microcantilevers have shown promise for sensing application of molecules in the vapor phase. Nanostructures have improved the molecule capture ability of microcantilevers by highly enhancing the surface of capture. Here, to improve the sensitivity and selectivity of a commercial microcantilever without functionalization, we developed 3D core-shell titanium dioxide@manganese dioxide (TiO2@MnO2) nanorod arrays on a microcantilever, which exhibited a high enhancement in the sensing performance beyond that of 1D nanostructures for the detection of dimethyl methylphosphonate, a simulant of sarin.

Double-side microcantilevers as a key to understand the adsorption mechanisms and kinetics of chemical warfare agents on vertically-aligned TiO2 nanotubes.

Microgravimetric sensor platforms with physico- or chemo-selective interfaces offer promising sensing properties. They are widely used to detect chemical warfare agents (CWAs). However, a comprehensive insight into adsorption mechanisms and interactions between low concentrations of these adsorbates and low-mass adsorbents is still lacking. In this study, we report a complete and detailed analytical method to model the adsorption processes of low traces of vapor-phase DiMethyl MethylPhosphonate (DMMP), a conventional simulant of CWAs, on a double-side nanostructured microcantilever coated with vertically-aligned titanium dioxide nanotubes (TiO2-NTs). We find that the geometrical configuration of NTs plays an important role in the diffusion regimes of molecules during the adsorption. This study shines light on the adsorption and kinetic mechanisms of low-traces DMMP offering opportunities to have a better insight of the adsorption of CWAs on complex nanostructures and to improve microcantilever sensors.

DNA Origami for Silicon Patterning.

Desoxyribonucleic acid (DNA) origami architectures are a promising tool for ultimate lithography because of their ability to generate nanostructures with a minimum feature size down to 2 nm. In this paper, we developed a method for silicon (Si) nanopatterning to face up current limitations for high-resolution patterning with standard microelectronic processes. For the first time, a 2 nm-thick 2D DNA origami mask, with specific design composed of three different square holes (with a size of 10 and 20 nm), is used for positive pattern transfer into a Si substrate using a 15 nm-thick silicon dioxide (SiO2) layer as an intermediate hard mask. First, the origami mask is transferred onto the SiO2 underlayer, by an HF vapor-etching process. Then, the Si underlayer is etched using an HBr/O2 plasma. Each hole is transferred in the SiO2 layer and the 20 nm-sized holes are transferred into the final stack (Si). The resulting patterns exhibited a lateral resolution in the range of 20 nm and a depth of 40 nm. Patterns are fully characterized by atomic force microscopy, scanning electron microscopy, focused ion beam-transmission electron microscopy, and ellipsometry measurements.

Double side nanostructuring of microcantilever sensors with TiO2-NTs as a route to enhance their sensitivity.

We reported a new strategy to enhance the sensing performances of a commercial microcantilever with optical readout in dynamic mode for the vapor detection of organophosphorus compounds (OPs). In order to increase significantly the surface area accessible to the molecules in the vapor phase, we nanostructured both sides of the microcantilever with ordered, open and vertically oriented amorphous titanium dioxide nanotubes (TiO2-NTs) in one step by an anodization method. However, due to the aggressive conditions of anodization synthesis it remains a real challenge to nanostructure both sides of the microcantilever. Consequently, we developed and optimized a protocol of synthesis to overcome these harsh conditions which can lead to the total destruction of the silicon microcantilever. Moreover, this protocol was also elaborated in order to maintain a good reflection of the laser beam on one side of the microcantilever towards the position sensitive photodiode and limit the light diffusion by the NTs film. The results related to the detection of dimethyl methylphosphonate (DMMP) showed that TiO2 and the nanostructuring on both sides of the microcantilever with NTs indeed improved the response of the sensor to vapors compared to a microcantilever nanostructured on only one side. The dimensions and morphology of NTs guaranteed the access of molecules to the surface of NTs. This approach showed promising prospects to enhance the sensing performances of microcantilevers.

Detection of Organophosphorous Chemical Agents with CuO-Nanorod-Modified Microcantilevers.

Microcantilevers are really promising sensitive sensors despite their small surface. In order to increase this surface and consequently their sensitivity, we nanostructured them with copper oxide (CuO) nanorods. The synthesis of the nanostructure consists of the oxidation of a copper layer deposited beforehand on the surface of the sample. The oxidation is performed in an alkaline solution containing a mixture of Na(OH) and (NH4)2S2O8. The synthesis procedure was first optimized on a silicon wafer, then transferred to optical cantilever-based sensors. This transfer requires specific synthesis modifications in order to cover all the cantilever with nanorods. A masking procedure was specially developed and the copper layer deposition was also optimized. These nanostructured cantilevers were engineered in order to detect vapors of organophosphorous chemical warfare agents (CWA). The nanostructured microcantilevers were exposed to various concentration of dimethyl methylphosphonate (DMMP) which is a well-known simulant of sarin (GB). The detection measurements showed that copper oxide is able to detect DMMP via hydrogen interactions. The results showed also that the increase of the microcantilever surface with the nanostructures improves the sensors efficiency. The evolution of the detection performances of the CuO nanostructured cantilevers with the DMMP concentration was also evaluated.

Innovative Magnetic Nanoparticles for PET/MRI Bimodal Imaging.

Superparamagnetic iron oxide nanoparticles were developed as positron emission tomography (PET) and magnetic resonance imaging (MRI) bimodal imaging agents. These nanoparticles (NPs), with a specific nanoflower morphology, were first synthesized and simultaneously functionalized with 3,4-dihydroxy-l-phenylalanine (LDOPA) under continuous hydrothermal conditions. The resulting NPs exhibited a low hydrodynamic size of 90 ± 2 nm. The functional groups of LDOPA (-NH2 and -COOH) were successfully used for the grafting of molecules of interest in a second step. The nanostructures were modified by poly(ethylene glycol) (PEG) and a new macrocyclic chelator MANOTA for further 64Cu radiolabeling for PET imaging. The functionalized NPs showed promising bimodal (PET and MRI) imaging capability with high r 2 and r 2* (T 2 and T 2* relaxivities) values and good stability. They were mainly uptaken from liver and kidneys. No cytotoxicity effect was observed. These NPs appear as a good candidate for bimodal tracers in PET/MRI.

Efficient functionalization of magnetite nanoparticles with phosphonate using a one-step continuous hydrothermal process.

For the first time, phosphonate-functionalized magnetite nanoparticles (Fe3O4 NPs) were synthesized using a one-step continuous hydrothermal process. The NP surface was modified using a hydrophilic organic molecule, namely 6-phosphonohexanoic acid (PHA). NPs were fully characterized (TEM, XRD, DLS, ζ-potential, TGA, FTIR, XPS and specific surface area measurements) in order to investigate PHA effect on size, oxidation state, anchoring and colloidal stability. PHA reduced the crystallite size and size distribution and improved greatly colloidal stability when compared with bare Fe3O4 NPs. Moreover, PHA was grafted on the NP surface according to three different conformations: as mononuclear monodendates, as binuclear bidentates or as lying-down complexes. This report is very promising regarding the stabilization and functionalization of Fe3O4 NPs by phosphonate molecules under continuous hydrothermal conditions. The post-grafting of polymers such as polyethylene glycol can be considered owing to the presence of free carboxyl groups (-COOH) on the surface of Fe3O4 NPs.