In situ Generated Iridium Nanoparticles as Hydride Donors in Photoredox-Catalyzed Hydrogen Isotope Exchange Reactions with Deuterium and Tritium Gas.

We have studied the photoredox-catalyzed hydrogen isotope exchange (HIE) reaction with deuterium or tritium gas as isotope sources and in situ formed transition metal nanoparticles as hydrogen atom transfer pre-catalysts. By this means we have found synergistic reactivities applying two different HIE mechanisms, namely photoredox-catalyzed and CH-functionalization HIE leading to the synthesis of highly deuterated complex molecules. Finally, we adopted these findings successfully to tritium chemistry.

Self-catalyzed InAs nanowires grown on Si: the key role of kinetics on their morphology.

Integrating self-catalyzed InAs nanowires on Si(111) is an important step toward building vertical gate-all-around transistors. The complementary metal oxide semiconductor (CMOS) compatibility and the nanowire aspect ratio are two crucial parameters to consider. In this work, we optimize the InAs nanowire morphology by changing the growth mode from Vapor-Solid to Vapor-Liquid-Solid in a CMOS compatible process. We study the key role of the Hydrogen surface preparation on nanowire growths and bound it to a change of the chemical potential and adatoms diffusion length on the substrate. We transfer the optimized process to patterned wafers and adapt both the surface preparation and the growth conditions. Once group III and V fluxes are balances, aspect ratio can be improved by increasing the system kinetics. Overall, we propose a method for large scale integration of CMOS compatible InAs nanowire on silicon and highlight the major role of kinetics on the growth mechanism.

An Improved STEM/EDX Quantitative Method for Dopant Profiling at the Nanoscale.

In this paper, an improved quantification technique for STEM/EDX measurements of 1D dopant profiles based on the Cliff-Lorimer equation is presented. The technique uses an iterative absorption correction procedure based on density models correlating the local mass density and composition of the specimen. Moreover, a calibration and error estimation procedure based on linear regression and error propagation is proposed in order to estimate the total measurement error in the dopant density. The proposed approach is applied to the measurement of the As profile in a nanodevice test structure. For the calibration, two crystalline Si specimens implanted with different As doses have been used, and the calibration of the Cliff-Lorimer coefficients has been carried out using Rutherford Back Scattering measurements. The As profile measurement has been carried out on an FinFET test structure, showing that quantitative results can be obtained in the nanometer scale and for dopant atomic densities lower than 1%. Using the proposed approach, the measurement error and detection limit for our experimental setup are calculated and the possibility to improve this limit by increasing the observation time is discussed.

Engineering Iron-Nickel Nanoparticles for Magnetically Induced CO2 Methanation in Continuous Flow.

Induction heating of magnetic nanoparticles (NPs) is a method to activate heterogeneous catalytic reactions. It requires nano-objects displaying high heating power and excellent catalytic activity. Here, using a surface engineering approach, bimetallic NPs are used for magnetically induced CO2 methanation, acting both as heating agent and catalyst. The organometallic synthesis of Fe30 Ni70 NPs displaying high heating powers at low magnetic field amplitudes is described. The NPs are active but only slightly selective for CH4 after deposition on SiRAlOx owing to an iron-rich shell (25 mL min-1 , 25 mT, 300 kHz, conversion 71 %, methane selectivity 65 %). Proper surface engineering consisting of depositing a thin Ni layer leads to Fe30 Ni70 @Ni NPs displaying a very high activity for CO2 hydrogenation and a full selectivity. A quantitative yield in methane is obtained at low magnetic field and mild conditions (25 mL min-1 , 19 mT, 300 kHz, conversion 100 %, methane selectivity 100 %).

Magnetically Induced CO2 Methanation Using Exchange-Coupled Spinel Ferrites in Cuboctahedron-Shaped Nanocrystals.

Magnetically induced catalysis can be promoted taking advantage of optimal heating properties from the magnetic nanoparticles to be employed. However, when unprotected, these heating agents that are usually air-sensitive, get sintered under the harsh catalytic conditions. In this context, we present, to the best of our knowledge, the first example of air-stable magnetic nanoparticles that: 1) show excellent performance as heating agents in the CO2 methanation catalyzed by Ni/SiRAlOx, with CH4 yields above 95 %, and 2) do not sinter under reaction conditions. To attain both characteristics we demonstrate, first the exchange-coupled magnetic approach as an alternative and effective way to tune the magnetic response and heating efficiency, and second, the chemical stability of cuboctahedron-shaped core-shell hard CoFe2 O4 -soft Fe3 O4 nanoparticles.

Multiple Site Hydrogen Isotope Labelling of Pharmaceuticals.

Radiolabelling is fundamental in drug discovery and development as it is mandatory for preclinical ADME studies and late-stage human clinical trials. Herein, a general, effective, and easy to implement method for the multiple site incorporation of deuterium and tritium atoms using the commercially available and air-stable iridium precatalyst [Ir(COD)(OMe)]2 is described. A large scope of pharmaceutically relevant substructures can be labelled using this method including pyridine, pyrazine, indole, carbazole, aniline, oxa-/thia-zoles, thiophene, but also electron-rich phenyl groups. The high functional group tolerance of the reaction is highlighted by the labelling of a wide range of complex pharmaceuticals, containing notably halogen or sulfur atoms and nitrile groups. The multiple site hydrogen isotope incorporation has been explained by the in situ formation of complementary catalytically active species: monometallic iridium complexes and iridium nanoparticles.

Air-Stable Anisotropic Monocrystalline Nickel Nanowires Characterized Using Electron Holography.

Nickel is capable of discharging electric and magnetic shocks in aerospace materials thanks to its conductivity and magnetism. Nickel nanowires are especially desirable for such an application as electronic percolation can be achieved without significantly increasing the weight of the composite material. In this work, single-crystal nickel nanowires possessing a homogeneous magnetic field are produced via a metal-organic precursor decomposition synthesis in solution. The nickel wires are 20 nm in width and 1-2 µm in length. The high anisotropy is attained through a combination of preferential crystal growth in the ⟨100⟩ direction and surfactant templating using hexadecylamine and stearic acid. The organic template ligands protect the nickel from oxidation, even after months of exposure to ambient conditions. These materials were studied using electron holography to characterize their magnetic properties. These thin nanowires display homogeneous ferromagnetism with a magnetic saturation (517 ± 80 emu cm-3), which is nearly equivalent to that of bulk nickel (557 emu cm-3). Nickel nanowires were incorporated into carbon composite test pieces and were shown to dramatically improve the electric discharge properties of the composite material.

Hydrodeoxygenation Using Magnetic Induction: High-Temperature Heterogeneous Catalysis in Solution.

Magnetic heating has recently been demonstrated as an efficient way to perform catalytic reactions after deposition of the heating agent and the catalyst on a support. Here we show that in solution, and under mild conditions of mean temperature and pressure, it is possible to use magnetic heating to carry out transformations that are otherwise performed heterogeneously at high pressure and/or high temperature. As a proof of concept, we chose the hydrodeoxygenation of acetophenone derivatives and of biomass-derived molecules, namely furfural and hydroxymethylfurfural. These reactions are difficult, require heterogeneous catalysts and high pressures, and, to the best of our knowledge, have no precedent in standard solution. Here, hydrodeoxygenations are fully selective under mild conditions (3 bar H2 , moderate mean temperature of the solvent). The reason for this reactivity is the fast heating of the particles well above the boiling temperature of the solvent and the local creation of hot spots surrounded by a vapor layer, in which high temperature and pressure may be present. This technology may be practicable for many organic transformations.

Synergism of Au and Ru Nanoparticles in Low-Temperature Photoassisted CO2 Methanation.

Au and Ru nanoparticles (NPs) have been deposited on Siralox® substrate by impregnation and chemical reduction, respectively (Au-Ru-S). The as-prepared material is very active in the selective CO2 methanation to CH4 at temperatures below 250 °C. In addition, Au-Ru-S shows enhanced CH4 production upon irradiation with UV/Vis light starting at temperatures higher than 200 °C, although the contribution of the photoassisted pathway of CH4 production decreases as the temperature increases. Thus, a maximum CH4 production of 204 mmol gRu -1 at 250 °C upon 100 mW cm-2 irradiation was achieved. Control experiments, in which Ru-S and Au-S materials were used, revealed that Ru NPs are the CO2 methanation active sites, while Au NPs contribute by harvesting light, mainly visible as a consequence of the strong Au plasmon band centered at 529 nm. The visible light absorbed by the plasmonic band of Au NPs could make them act ass local heaters of the neighboring Ru NPs, increasing their temperature and enhancing CH4 production.

Concerted Growth and Ordering of Cobalt Nanorod Arrays as Revealed by Tandem in Situ SAXS-XAS Studies.

The molecular and ensemble dynamics for the growth of hierarchical supercrystals of cobalt nanorods have been studied by in situ tandem X-ray absorption spectroscopy-small-angle X-ray scattering (XAS-SAXS). The supercrystals were obtained by reducing a Co(II) precursor under H2 in the presence of a long-chain amine and a long-chain carboxylic acid. Complementary time-dependent ex situ TEM studies were also performed. The experimental data provide critical insights into the nanorod growth mechanism and unequivocal evidence for a concerted growth-organization process. Nanorod formation involves cobalt nucleation, a fast atom-by-atom anisotropic growth, and a slower oriented attachment process that continues well after cobalt reduction is complete. Smectic-like ordering of the nanorods appears very early in the process, as soon as nanoparticle elongation appears, and nanorod growth takes place inside organized superlattices, which can be regarded as mesocrystals.

Complex Nano-objects Displaying Both Magnetic and Catalytic Properties: A Proof of Concept for Magnetically Induced Heterogeneous Catalysis.

Addition of Co2(Co)9 and Ru3(CO)12 on preformed monodisperse iron(0) nanoparticles (Fe(0) NPs) at 150 °C under H2 leads to monodisperse core-shell Fe@FeCo NPs and to a thin discontinuous Ru(0) layer supported on the initial Fe(0) NPs. The new complex NPs were studied by state-of-the-art transmission electron microscopy techniques as well as X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. These particles display large heating powers (SAR) when placed in an alternating magnetic field. The combination of magnetic and surface catalytic properties of these novel objects were used to demonstrate a new concept: the possibility of performing Fischer-Tropsch syntheses by heating the catalytic nanoparticles with an external alternating magnetic field.

Magnetically Induced Continuous CO2 Hydrogenation Using Composite Iron Carbide Nanoparticles of Exceptionally High Heating Power.

The use of magnetic nanoparticles to convert electromagnetic energy into heat is known to be a key strategy for numerous biomedical applications but is also an approach of growing interest in the field of catalysis. The heating efficiency of magnetic nanoparticles is limited by the poor magnetic properties of most of them. Here we show that the new generation of iron carbide nanoparticles of controlled size and with over 80 % crystalline Fe2.2 C leads to exceptional heating properties, which are much better than the heating properties of currently available nanoparticles. Associated to catalytic metals (Ni, Ru), iron carbide nanoparticles submitted to magnetic excitation very efficiently catalyze CO2 hydrogenation in a dedicated continuous-flow reactor. Hence, we demonstrate that the concept of magnetically induced heterogeneous catalysis can be successfully applied to methanation of CO2 and represents an approach of strategic interest in the context of intermittent energy storage and CO2 recovery.

Isoprene Polymerization on Iron Nanoparticles Confined in Carbon Nanotubes.

The confinement of air-protected metallic magnetic nanoparticles in the inner cavity of carbon nanotubes (CNTs) should offer an interesting perspective for biomedical applications or for controlling CNT alignment in composites. Because the direct confinement of polymer-precoated nanoparticles in CNTs could be restricted by diffusion limitations, we developed a process based on: 1) the confinement of iron nanoparticles surface-modified with an iron polymerization catalyst in the cavity of CNTs and 2) the polymerization of isoprene on the confined nanoparticles. The resulting material consists in CNT-confined iron nanoparticles coated with a polyisoprene air barrier. This approach constitutes a proof of concept for the development of smart materials for use in medicine or composites.

Monitoring the coordination of amine ligands on silver nanoparticles using NMR and SERS.

Low size dispersity silver nanoparticles (ca. 6 nm) have been synthesized by the hydrogenolysis of silver amidinate in the presence of hexadecylamine. Combining NMR techniques with SERS and DFT modeling, it is possible to observe an original stabilization mechanism. Amidine moiety is strongly coordinated to the Ag(0) nanoparticles surface whereas HDA ligand is necessary to prevent agglomeration, although it is only weakly interacting with the surface.

Metallic Nanoalloys on Vertical GaAs Nanowires: Growth Mechanisms and Shape Control of Ni-GaAs Compounds.

GaAs nanowires are promising candidates for emerging devices in a broad field of applications (e.g., nanoelectronics, photodetection, or photoconversion). These nanostructures benefit greatly from a vertical integration, as it allows for the exhibition of the entire nanowire surface. However, one of the main challenges related to vertical integration is the conception of an efficient method to create low resistive contacts at nanoscale without degrading the device performance. In this article, we propose a complementary metal-oxide-semiconductor (CMOS)-compatible approach to form alloyed contacts at the extremities of vertical GaAs nanowires. Ni-based and Pd-based alloys on different vertical GaAs nanostructures have been characterized by structural and chemical analyses to identify the phase and to study the growth mechanisms involved at the nanoscale. It is shown that the formation of the Ni3GaAs alloy on top of nanowires following the epitaxial relation Ni3GaAs(0001)∥GaAs(111) leads to a pyramidal shape with four faces. Finally, guidelines are presented to tune the shape of this alloy by varying the initial metal thickness and nanowire diameters. It will facilitate the fabrication of a nanoalloy structure with tailored shape characteristics to precisely align with a designated application.

A simple chemical route toward monodisperse iron carbide nanoparticles displaying tunable magnetic and unprecedented hyperthermia properties.

We report a tunable organometallic synthesis of monodisperse iron carbide and core/shell iron/iron carbide nanoparticles displaying a high magnetization and good air-stability. This process based on the decomposition of Fe(CO)(5) on Fe(0) seeds allows the control of the amount of carbon diffused and therefore the tuning of nanoparticles magnetic anisotropy. This results in unprecedented hyperthermia properties at moderate magnetic fields, in the range of medical treatments.

l-Lysine Stabilized FeNi Nanoparticles for the Catalytic Reduction of Biomass-Derived Substrates in Water Using Magnetic Induction.

The reduction of biomass-derived compounds gives access to valuable chemicals from renewable sources, circumventing the use of fossil feedstocks. Herein, we describe the use of iron-nickel magnetic nanoparticles for the reduction of biomass model compounds in aqueous media under magnetic induction. Nanoparticles with a hydrophobic ligand (FeNi3 -PA, PA=palmitic acid) have been employed successfully, and their catalytic performance is intended to improve by ligand exchange with lysine (FeNi3 -Lys and FeNi3 @Ni-Lys NPs) to enhance water dispersibility. All three catalysts have been used to hydrogenate 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan with complete selectivity and almost quantitative yields, using 3 bar of H2 and a magnetic field of 65 mT in water. These catalysts have been recycled up to 10 times maintaining high conversions. Under the same conditions, levulinic acid has been hydrogenated to γ-valerolactone, and 4'-hydroxyacetophenone hydrodeoxygenated to 4-ethylphenol, with conversions up to 70 % using FeNi3 -Lys, and selectivities above 85 % in both cases. This promising catalytic system improves biomass reduction sustainability by avoiding noble metals and expensive ligands, increasing energy efficiency via magnetic induction heating, using low H2 pressure, and proving good reusability while working in an aqueous medium.

Water-soluble NHC Pd/Ni bimetallic nanoparticles for H/D exchange in aromatic amino-acids.

Labelling of amino-acids is important for the production of deuterated proteins. However, aromatic amino-acid reduction is a common undesired process with noble-metal nanocatalysts. In this work, we describe a new NHC-stabilized water-soluble Pd/Ni system able to perform H/D exchange reactions in an enantiospecific fashion without reducing the aromatic ring of phenylalanine and tyrosine thanks to a synergetic Pd-Ni effect.

Induction heating: an efficient methodology for the synthesis of functional core-shell nanoparticles.

Induction heating has been applied for a variety of purposes over the years, including hyperthermia-induced cell death, industrial manufacturing, and heterogeneous catalysis. However, its potential in materials synthesis has not been extensively studied. Herein, we have demonstrated magnetic induction heating-assisted synthesis of core-shell nanoparticles starting from a magnetic core. The induction heating approach allows an easy synthesis of FeNi3@Mo and Fe2.2C@Mo nanoparticles containing a significantly higher amount of molybdenum on the surface than similar materials synthesized using conventional heating. Exhaustive electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy characterization data are presented to establish the core-shell structures. Furthermore, the molybdenum shell was transformed into the Mo2C phase, and the catalytic activity of the resulting nanoparticles tested for the propane dry reforming reaction under induction heating. Lastly, the beneficial role of induction heating-mediated synthesis was extended toward the preparation of the FeNi3@WOx core-shell nanoparticles.

Magnetically Induced CO2 Methanation In Continuous Flow Over Supported Nickel Catalysts with Improved Energy Efficiency.

A new selective and efficient catalytic system for magnetically induced catalytic CO2 methanation was developed, composed of an abundant iron-based heating agent, namely a commercial iron wool, combined with supported Nickel nanoparticles (Ni NPs) as catalysts. The effect of metal oxide support was evaluated by preparing different 10 wt % Ni catalyst (TiO2 , ZrO2 , CeO2 , and CeZrO2 ) via organometallic decomposition route. As-prepared catalysts were thoroughly characterized using powder X-ray diffraction, electron microscopy, elemental analysis, vibrating sample magnetometer, and X-ray photoelectron spectroscopy techniques. High conversion and selectivity toward methane were observed at mid-temperature range, hence improving energy efficiency of the process with respect to the previous results under magnetic heating conditions. To gain further insight into the catalytic system, the effects of the synthesis method and of 0.5 wt % Ru doping were evaluated. Finally, the dynamic nature of magnetically induced heating was demonstrated through fast stop-and-go experiments, proving the suitability of this technology for the storage of intermittent renewable energy through P2G process.