Hybrid hierarchical patterns of gold nanoparticles and poly(ethylene glycol) microstructures

Hybrid surface micro-patterns composed of topographic structures of polyethylene glycol (PEG)-hydrogels and hierarchical lines of gold nanoparticles (Au NPs) were fabricated on silicon wafers. Micro-sized lines of Au NPs were first obtained on the surface of a silicon wafer via “micro-contact deprinting”, a method recently developed by our group. Topographic micro-patterns of PEG, of both low and high aspect ratio (AR up to 6), were then aligned on the pre-patterned surface via a procedure adapted from the soft lithographic method MIMIC (Micro-Molding in Capillaries), which is denoted as “adhesive embossing”. The result is a complex surface pattern consisting of alternating flat Au NP lines and thick PEG bars. Such patterns provide novel model surfaces for elucidating the interplay between (bio)chemical and physical cues on cell behavior

In Situ Formed “Sn1–XInX@In1–YSnYOZ” Core@Shell Nanoparticles as Electrocatalysts for CO2 Reduction to Formate

Electrochemical reduction of CO2 (CO2RR) driven by renewable energy has gained increasing attention for sustainable production of chemicals and fuels. Catalyst design to overcome large overpotentials and poor product selectivity remains however challenging. Sn/SnOx and In/InOx composites have been reported active for CO2RR with high selectivity toward formate formation. In this work, the CO2RR activity and selectivity of metal/metal oxide composite nanoparticles formed by in situ reduction of bimetallic amorphous SnInOx thin films are investigated. It is shown that during CO2RR the amorphous SnInOx pre‐catalyst thin films are reduced in situ into Sn1–XInX@In1–YSnYOz core@shell nanoparticles composed of Sn‐rich SnIn alloy nanocores (with x < 0.2) surrounded by InOx‐rich bimetallic InSnOx shells (with 0.3 < y < 0.4 and z ≈ 1). The in situ formed particles catalyze the CO2RR to formate with high faradaic efficiency (80%) and outstanding formate mass activity (437 A gIn+Sn−1 @ −1.0 V vs RHE in 0.1 m KHCO3). While extensive structural investigation during CO2RR reveals pronounced dynamics in terms of particle size, the core@shell structure is observed for the different electrolysis conditions essayed, with high surface oxide contents favoring formate over hydrogen selectivity.DFG, 53182490, EXC 314: Unifying Concepts in CatalysisBMBF, 03X5524, EDELKAT - Hydrophobe Nanoreaktor Templatierung - Eine Tool-Box für optimierte ElektrokatalysatorenBMBF, 01FP13033F, Förderung der Vorgriffsprofessur im Fach "Anorganische Funktionsmaterialien" im Rahmen des Professorinnenprogramms II an der Albert-Ludwigs-Universität FreiburgEC/H2020/101006701/EU/Renewable Electricity-based, cyclic and economic production of Fuel/EcoFue

Répercussion professionnelles du syndrome post-commotionnel secondaire à un traumatisme cranien léger (étude prospective sur six mois)

But: Rechercher l'existence de répercussions d'un syndrome post-commotionnel (SPC) secondaire à un traumatisme crânien léger (TCL) sur l'activité professionnelle. Méthode: Etude prospective descriptive sur six mois par questionnaires pour rechercher l'existence d'un SPC et d'éventuelles difficultés au travail. Résultats: Analyse sur 70 patients. SPC pour 48% (n=34) à 1 mois, pour 38% (n=27) à 3 mois, à l'origine pour 39% (n=26) de difficultés au travail. 7 sujets n'ont pas trouvé de stratégies de compensation et sont gênés dans leur travail. A mois, 4 sujets n'ont pas repris leur travail (2 directement à cause du SPC), 2 ont changé de poste dont 1 transitoirement, et 2 ont diminué leur temps de travail de façon temporaire. Conclusion: Le SPC est fréquent après un TCL mais ne semble pas être un obstacle majeur à la poursuite d'une activité professionnelle, la majorité des victimes de notre étude continue à travailler dans les conditions identiques à la situation pré-traumatique.RENNES1-BU Santé (352382103) / SudocSudocFranceF

Downsizing FeNb11O29 anode material through ultrafast solid-state microwave-assisted synthesis for enhanced electrochemical performance

International audienceWadsley-Roth oxide FeNb11O29 powder samples are successfully prepared using a simple, cost-effective, and ultrafast microwave-assisted solid-state synthesis for the first time. While conventional solid-state route in furnace requires hours of high-temperature treatment, both monoclinic and orthorhombic polymorphs of FeNb11O29 were obtained in minutes under microwave heating. Combining such short heat treatment with submicrometric oxide precursors enables to limit particle growth during the synthesis. The electrochemical benchmark clearly shows that FeNb11O29 powder samples obtained rapidly from submicrometric oxide precursors exhibit enhanced cycling performance. For example, the monoclinic polymorph prepared in only 5 min offers a high capacity of 179 mAh g-1 (90 % retention) after 500 cycles at 2 A g-1, approximately 20 % more than with conventional synthesis protocol. Electrochemical analysis demonstrates that the extra capacity is gained at low voltage and is probably induced by an easier ionic diffusion occurring in smaller particles. This work confirms the interest of solid-state microwave heating to design of electrode materials with limited particle growth and better cycling performance

Structurally Ordered Intermetallic Cobalt Stannide Nanocrystals for High-Performance Electrocatalytic Overall Water-Splitting

International audienceThe synthesis of structurally ordered non-noble intermetallic cobalt stannide (CoSn2) nanocrystals and their utilization for high-performance electrocatalytic overall water-splitting is presented. The structurally and electronically beneficial properties of the tetragonal CoSn2 exhibit a considerably low overpotential for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on fluorine-doped tin oxide (FTO) and Ni foam (NF). Loss of Sn from the crystal lattices and oxidation of Co under strongly alkaline conditions furnishes highly disordered amorphous active CoOx(H), the catalytically active structure for OER. The Co0 atoms in the CoSn2 act as active sites for HER and the presence of Sn provides efficient electrical conductivity.T his intermetallic phase is an ovel type of cost-effective and competitive bifunctional electrocatalysts and predestinated for overall water-splitting devices:A two-electrode electrolyzer with CoSn2 on NF delivers ac ell voltage of merely 1.55 Va t 10 mA cm-2 maintaining long-term stability

Copper-Substituted NiTiO3 Ilmenite-Type Materials for Oxygen Evolution Reaction

International audienceSingle Ni1−xCuxTiO3 (0.05 ≤ x ≤ 0.2) Ilmenite-type phases were successfully prepared through a solid-state reaction route using divalent metal nitrates as precursors and characterized. Their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media is presented. The Cu content was determined (0.05 ≤ x ≤ 0.2) by X-ray diffraction. A thorough powder neutron diffraction study was carried out to identify the subtle changes caused by copper substitution in the structure of NiTiO3. The evolution of the optical and magnetic properties with the Cu content was also investigated on the raw micrometer-sized particles. A reduction in particle size down to ≈15 nm was achieved by ball-milling the raw powder prepared by the solid-state reaction. The best catalytic activity for OER was obtained for nanometer-sized particles of Ni0.8Cu0.2TiO3 drop-casted on the Cu plate. For this electrode, a current density of 10 mA cm −2 for oxygen production was generated at 345 and 470 mV applied overpotentials with 1 and 0.1 M NaOH solutions as electrolytes, respectively. The catalyst retained this OER activity at 10 mA cm −2 for long-term electrolysis with a faradic efficiency of 90% for O2 production in a 0.1 M NaOH electrolyte

Investigation of Amorphous Mixed-Metal (Oxy)Fluorides as a New Class of Water Oxidation Electrocatalysts

The development of electrocatalysts for the oxygen evolution reaction (OER) is one of the principal challenges in the area of renewable energy research. Within this context, mixed-metal oxides have recently emerged as the highest performing OER catalysts. Their structural and compositional modification to further boost their activity is crucial to the wide-spread use of electrolysis technologies. In this work, we investigated a series of mixed-metal F-containing materials as OER catalysts to probe possible benefits of the high electronegativity of fluoride ions. We found that crystalline hydrated fluorides, CoFe2F8(H2O)2, NiFe2F8(H2O)2, and amorphous oxyfluorides, NiFe2F4.4O1.8 and CoFe2F6.6O0.7, feature excellent activity and stability for the OER in alkaline electrolyte. Subsequent electroanalytical and spectroscopic characterization hinted that the electronic structure modulation conferred by the fluoride ions aided their reactivity. Finally, the best catalyst of the set, NiFe2F4.4O1.8, was applied as anode in an electrolyzer comprised solely of earth-abundant materials.</p

Photoinduced Magnetism in Core/Shell Prussian Blue Analogue Heterostructures of KjNik[Cr(CN)6]l·nH2O with RbaCob[Fe(CN)6]c·mH2O

International audienceCore/shell and core/shell/shell particles comprised of the Prussian blue analogues KjNik[Cr(CN)6]l.3nH2O (A) and RbaCob[Fe(CN)6]c.3 mH2O (B) have been prepared for the purpose of studying persistent photoinduced magnetization in the heterostructures. Synthetic procedures have been refined to allow controlled growth of relatively thick (50-100 nm) consecutive layers of the Prussian blue analogues while minimizing the mixing of materials at the interfaces. Through changes in the order in which the two components are added, particles with AB, ABA, BA, and BAB sequences have been prepared. The two Prussian blue analogues were chosen because B is photoswitchable, and A is ferromagnetic with a relatively high magnetic ordering temperature, ∼70 K, although it is not known to exhibit photoinduced changes in its magnetic properties. Magnetization measurements on the heterostructured particles performed prior to irradiation show behavior characteristic of the individual components. On the other hand, after irradiation with visible light, the heterostructures undergo persistent photoinduced changes in magnetization associated with both the B and A analogues. The results suggest that structural changes in the photoactive B component distort the normally photoinactive A component, leading to a change in its magnetization

Understanding the bactericidal mechanism of Cu(OH)2 nanorods in water through Mg-substitution: high production of toxic hydroxyl radicals by non-soluble particles

International audienceTo date, there is still a lack of definite knowledge regarding the toxicity of Cu(OH)2 nanoparticles towards bacteria. This study was aimed at shedding light on the role played by released cupric ions in the toxicity of nanoparticles. To address this issue, the bactericidal activity of Cu(OH)2 was at first evaluated in sterile water, a medium in which particles are not soluble. In parallel, an isovalent substitution of cupric ions by Mg2+ was attempted in the crystal structure of Cu(OH)2 nanoparticles to increase their solubility and determine the impact on the bactericidal activity. For the first time, mixed Cu1xMgx(OH)2 nanorods (x ≤ 0.1) of about 15 nm in diameter and a few hundred nanometers in length were successfully prepared by a simple co-precipitation at room temperature in mixed alkaline (NaOH/Na2CO3) medium. For E. coli, 100% reduction of one million CFU per mL (6 log10) occurs after only 180 min on contact with both Cu(OH)2 and Cu0.9Mg0.1(OH)2 nanorods. The entire initial inoculum of S. aureus is also killed by Cu(OH)2 after 180 min (100% or 6 log10 reduction), while 0.01% of these bacteria stay alive on contact with Cu0.9Mg0.1(OH)2 (99.99% or 4 log10 reduction). The bactericidal performances of Cu(OH)2 and the magnesium-substituted counterparts (i.e. Cu1xMgx(OH)2) are not linked to cupric ions they release in water since their mass concentrations after 180 min are much lower than minimal concentrations inhibiting the growth of E. coli and S. aureus. Finally, an EPR spin trapping study reveals how these nanorods kill bacteria in water: only the presence of hydrogen peroxide, a by-product of the normal metabolism of oxygen in aerobic bacteria, allows the Cu(OH)2 and its magnesium-substituted counterparts to produce a lethal amount of free radicals, the majority of which are the highly toxic HO•

Investigation of mixed-metal (oxy)fluorides as a new class of water oxidation electrocatalysts

International audienc