Transition énergétique

In a collaboration within the network of the Swiss Nanoscience Institute, the formation of free-standing molecular monolayers using self-assembly processes has been demonstrated. The results of the study have been published in the February 2019 issue of Science Advances.

Controlling the assembly of colloids in dispersion is a fundamental approach toward the production of functional materials. Nanocrystalline cellulose (NCC) is a charged nanoparticle whose colloidal interactions can be modulated from repulsive to attractive by increasing ionic strength.

We propose a method to accelerate small-angle scattering experiments by exploiting spatial correlation in two-dimensional data. We applied kernel density estimation to the average of a hundred short scans and evaluated noise reduction effects of kernel density estimation (smoothing).

Theories predict that some electrons in the kagome materials have exotic, so-called topological behaviors and others behave somewhat like graphene, another material prized for its potential for new types of electronics. 

We explore two methods for single-crystal growth of the theoretically proposed magnetic Weyl semimetals RAlGe (R = Pr, Ce), which prove that a floating-zone technique, being both crucible- and flux-free, is crucial to obtain perfectly stoichiometric RAlGe crystals. In contrast, the crystals grown by a flux-growth technique tend to be Al-rich. We further present both structural and elemental analyses, along with bulk magnetization and electrical resistivity data on the crystals prepared by the floating-zone technique. Both systems with the intended 1:1:1 stoichiometry crystallize in the anticipated polar I41md (No. 109) space group, although neither displays the theoretically expected ferromagnetic ground state.

Scientists have demonstrated in a combined theoretical and experimental effort that the new ligand-field density functional theory method (LF-DFT) can be used to calculate the X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) of lanthanide compounds from purely structural input.

Electronic systems with flat bands are predicted to be a fertile ground for hosting emergent phenomena including unconven- tional magnetism and superconductivity, but materials that manifest this feature are rare. Here, we use scanning tunnelling microscopy to elucidate the atomically resolved electronic states and their magnetic response in the kagome magnet Co₃Sn₂S₂.

The resonantly stabilized xylyl radicals (C₈H₉•) distinctively influence the combustion chemistry and, therefore, ultimately determine the performance of combustion engines. At that, the three different isomers (methyl group in ortho, para or meta position) exhibit notable differences at elevated temperatures. We have tracked down these dynamics on a femtosecond timescale by monitoring the response to preparation of a well-defined electronic and vibrational state.

Understanding and controlling the electronic structure of thin layers of quantum materials is a crucial first step towards designing heterostructures where new phases and phenomena, including the metal-insulator transition (MIT), emerge. Here, we demonstrate control of the MIT via tuning electronic bandwidth and local site environment through selection of the number of atomic layers deposited.

Magnetic monopoles, proposed as elementary particles that act as isolated magnetic south and north poles, have long attracted research interest as magnetic analogs to electric charge. In solid-state physics, a classical analog to these elusive particles has emerged as topological excitations within pyrochlore spin ice systems. We present the first real-time imaging of emergent magnetic monopole motion in a macroscopically degenerate artificial spin ice system consisting of thermally activated Ising-type nanomagnets lithographically arranged onto a pre-etched silicon substrate. factors are observed.

The binary Re_1−xMo_x alloys, known to cover the full range of solid solutions, were successfully synthesized and their crystal structures and physical properties investigated via powder x-ray diffraction, electrical resistivity, magnetic susceptibility, and heat capacity. By varying the Re/Mo ratio, we explore the full Re_1−xMo_x binary phase diagram, in all its four different solid phases: hcp-Mg (P63/mmc), α-Mn (I43m), β-CrFe (P42/mnm), and bcc-W (Im3m), of which the second is non-centrosymmetric with the rest being centrosymmetric. All Re_1−xMo_x alloys are superconductors, whose critical temperatures exhibit a peculiar phase diagram, characterized by three different superconducting regions.

The link between Pd nanoparticle structure and surface reactivity for NH3 abatement was found using operando X-ray absorption fine structure spectroscopy, diffuse reflectance infrared Fourier-transformed spectroscopy and on-line mass spectrometry.

In this paper, we use dynamic light scattering in polarized and depolarized modes to determine the translational and rotational diffusion coefficients of concentrated rodlike cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1–5 wt %), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by polarized light microscopy and viscosity measurements.

We show, by solving Maxwell’s equations, that an electric charge on the surface of a slab of a linear magnetoelectric material generates an image magnetic monopole below the surface provided that the magnetoelectric has a diagonal component in its magnetoelectric response. The image monopole, in turn, generates an ideal monopolar magnetic field outside of the slab.

Photoelectrochemical (PEC) solar water splitting is a promising approach to convert solar energy into sustainable hydrogen fuel using semiconductor electrodes. Owing to their visible light absorption properties, oxynitrides have shown to be attractive photocatalysts for this application. In this study, the influence of the preparation method of CaNbO₂N particles on their morphological and optical properties, and thereby their PEC performance, is investigated. The best performing CaNbO₂N photoanode is produced by ammonolysis of Nb-enriched calcium niobium oxide.

This work presents a new approach for synthesizing Fe-based oxygen reduction reaction (ORR) catalysts using sodium carbonate (Na₂CO₃) as an inexpensive but effective pore-inducing agent offering microporosity control.