Observation of magnetism in Au thin films

Direct magnetization measurements of thin gold films are presented. These measurements integrate the signal from the thin film under study and the magnetic contribution of the film's interface with the substrate. The diamagnetic contribution to the signal from the bulk substrate is of the same order as the noise level. we find that thin gold films can exhibit positive magnetization. The character of their magnetic behavior is strongly substrate dependent.Comment: 9 pages, 4 figure

Itinerant-electron Ferromagnetism in W(Nb)O3-d

The crystal structure and the magnetic properties of the W1-xNbxO3-d, (x<0.03) system have been investigated. In contrast to the orthorhombic diamagnetic WO3, the material with x=0.01 is paramagnetic down to 5 K. Introducing of 2.5 at. % of Nb into WO3 leads to a tetragonal structure and to a weak itinerant ferromagnetic ordering below TC= 225 K. The saturation magnetic moment at 5 K is 1.07*10-3 mB, whereas the paramagnetic effective moment is 0.06 mB per mole. This high ratio indicates itinerant ferromagnetism in W0.975Nb0.025O3-d.Comment: accepted to Physica

Weak links and phase slip centers in superconducting MgB2 wires

MgB2 superconducting wires were produced by the Mg diffusion method. Scanning electron microscopy (SEM), optical microscopy, dispersive x-ray analysis (EDS) and XRD diffraction were used to study the physical structure and content of the wires. Magnetic properties (Tcm, Hc1, Hc2, Jc by the Bean model) were obtained with a SQUID magnetometer, and transport properties (Tcr, Hc2, resistivity and residual resistivity ratio) were measured using a standard four-lead configuration. The V-I characteristics of the wires close to the critical temperature showed a staircase response, which was attributed to the presence of weak links, creating phase slip centers. The origin of those weak links is discussed in relation to their formation and structure.Comment: 7 pages, 7 figures, accepted to Journal of Superconductivit

Magnetization of small lead particles

The magnetization of an ensemble of isolated lead grains of sizes ranging from below 6 nm to 1000 nm is measured. A sharp disappearance of Meissner effect with lowering of the grain size is observed for the smaller grains. This is a direct observation by magnetization measurement of the occurrence of a critical particle size for superconductivity, which is consistent with Anderson's criterion.Comment: 7 pages, 5 figures, Submitted to PR

The suppression of Columnar π-Stacking in 3-Adamantyl-1-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl

3-Adamantyl-1-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (4) crystallizes as chains of radicals where the spin bearing benzotriazinyl moieties are isolated from each other. Magnetic susceptibility studies in the 5–300 K temperature region indicate that radical 4 demonstrates typical paramagnetic behavior stemming from non-interacting S = ½ spins

Selective room-temperature hydrogenation of amides to amines and alcohols catalyzed by a ruthenium pincer complex and mechanistic insight

This research was supported by the European Research Council (ERC AdG 692775). D.M. holds the Israel Matz Professorial Chair of Organic Chemistry. S.K. acknowledges the Sustainability and Energy Research Initiative (SAERI) of the Weizmann Institute of Science for a research fellowship. M.R. acknowledges the Zuckerman STEM Leadership Program for a research fellowship.We report a room-temperature protocol for the hydrogenation of various amides to produce amines and alcohols. Compared with most previous reports for this transformation, which use high temperatures (typically, 100–200 °C) and H2 pressures (10–100 bar), this system proceeds under extremely mild conditions (RT, 5–10 bar of H2). The hydrogenation is catalyzed by well-defined ruthenium-PNNH pincer complexes (0.5 mol %) with potential dual modes of metal–ligand cooperation. An unusual Ru-amidate complex was formed and crystallographically characterized. Mechanistic investigations indicate that the room-temperature hydrogenation proceeds predominantly via the Ru–N amido/amine metal–ligand cooperation.Publisher PDFPeer reviewe

Hydrogenative depolymerization of nylons

This research was supported by the European Research Council (ERC AdG 692775). D. M. holds the Israel Matz Professorial Chair of Organic Chemistry. A. K. is thankful to the Planning and Budgeting Committee of Israel and Feinberg Graduate School for a (senior) postdoctoral fellowship. Y.-Q. Z. acknowledges the Sustainability and Energy ResearchInitiative (SAERI) foundation for a research fellowship. Computations were performed using HPC resources from GENCI-CINES (Grant 2019 AP010811227).The widespread crisis of plastic pollution demands discovery of new and sustainable approaches to degrade robust plastics such as nylons. Using a green and sustainable approach based on hydrogenation, in the presence of a ruthenium pincer catalyst at 150 oC and 70 bar H2, we report here the first example of hydrogenative depolymerization of conventional, widely used nylons, and polyamides in general. Un-der the same catalytic conditions, we also demonstrate the hydrogenation of a polyurethane to produce diol, diamine and methanol. Additionally, we demonstrate an example where monomers (and oligomers) obtained from the hydrogenation process can be dehydrogenated back to a poly(oligo)amide of approximately similar molecular weight, thus completing a closed loop cycle for recycling of poly-amides. Based on the experimental and DFT studies, we propose a catalytic cycle for the process that is facilitated by metal-ligand cooperativity. Overall, this unprecedented transformation, albeit at the proof of concept level, offers a new approach towards a cleaner route to recycling nylons.Publisher PDFPeer reviewe