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Heteroanionic materials show promising potential as 2D semiconductors due to their tunable band gaps, making them excellent candidates for photocatalytic water splitting applications. We conducted detailed theoretical and experimental analysis of two selected materials by synthesizing crystals through chemical vapor transport and investigating the impact of anion variation on crystal structure and properties. Using powder X-ray diffraction and convergent beam electron diffraction, we elucidated the non-centrosymmetric space groups of these compounds. Thermochemical studies revealed the influence of the crystal structure on the decomposition points of both compounds. Theoretical investigations predict that both materials are indirect bandgap semiconductors, which is confirmed by electron energy loss spectroscopy and photoluminescence studies. [ABSTRACT FROM AUTHOR]

The self‐assembly of anisotropic nanocrystals (stabilized by organic capping molecules) with pre‐selected composition, size, and shape allows for the creation of nanostructured materials with unique structures and features. For such a material, the shape and packing of the individual nanoparticles play an important role. This work presents a synthesis procedure for ω‐thiol‐terminated polystyrene (PS‐SH) functionalized gold nanooctahedra of variable size (edge length 37, 46, 58, and 72 nm). The impact of polymer chain length (Mw: 11k, 22k, 43k, and 66k g⋅mol−1) on the growth of colloidal crystals (e. g. mesocrystals) and their resulting crystal structure is investigated. Small‐angle X‐ray scattering (SAXS) and scanning transmission electron microscopy (STEM) methods provide a detailed structural examination of the self‐assembled faceted mesocrystals based on octahedral gold nanoparticles of different size and surface functionalization. Three‐dimensional angular X‐ray cross‐correlation analysis (AXCCA) enables high‐precision determination of the superlattice structure and relative orientation of nanoparticles in mesocrystals. This approach allows us to perform non‐destructive characterization of mesocrystalline materials and reveals their structure with resolution down to the nanometer scale. [ABSTRACT FROM AUTHOR]

Aims: Testicular germ cell tumours are the most common solid malignancies in young men of age 14–44 years. It is generally accepted that both seminomas and non‐seminomas arise from a common precursor, the germ cell neoplasia in‐situ, which itself is the result of a defective (primordial) germ cell development. The stem cell‐like population of the non‐seminomas, the embryonal carcinoma, is capable of the differentiation of all three germ layers (teratomas) and extra‐embryonic tissues (yolk‐sac tumours, choriocarcioma) into cells. In contrast, seminomas are thought to have a limited differentiation potential. Nevertheless, several studies have highlighted their ability to undergo reprogramming to an embryonal carcinoma or differentiation into other non‐seminomatous entities. Here, we demonstrate that in approximately 5% of seminomas, the yolk‐sac tumour driver gene FOXA2 is detectable at the protein level, indicative of an occult yolk‐sac tumour subpopulation that putatively arose from seminoma cells, as the presence of other GCT entities could be excluded. The presence of these subpopulations might render the tumour more aggressive and argue for an adjustment of the therapeutic concept. We used our data to update the model of germ cell tumour pathogenesis, especially regarding the developmental potential of seminomas. Additionally, we suggest to include detection of FOXA2 into standard routine diagnosis of seminomas. [ABSTRACT FROM AUTHOR]

Chiral effects originate from the lack of inversion symmetry within the lattice unit cell or sample's shape. Being mapped onto magnetic ordering, chirality enables topologically non-trivial textures with a given handedness. Here, we demonstrate the existence of a static 3D texture characterized by two magnetochiral parameters being magnetic helicity of the vortex and geometrical chirality of the core string itself in geometrically curved asymmetric permalloy cap with a size of 80 nm and a vortex ground state. We experimentally validate the nonlocal chiral symmetry breaking effect in this object, which leads to the geometric deformation of the vortex string into a helix with curvature 3 μm−1 and torsion 11 μm−1. The geometric chirality of the vortex string is determined by the magnetic helicity of the vortex texture, constituting coupling of two chiral parameters within the same texture. Beyond the vortex state, we anticipate that complex curvilinear objects hosting 3D magnetic textures like curved skyrmion tubes and hopfions can be characterized by multiple coupled magnetochiral parameters, that influence their statics and field- or current-driven dynamics for spin-orbitronics and magnonics. Chiral interactions in magnetic systems enable topologically nontrivial magnetic textures, most notably topological solitons such as skyrmions. Here Volkov et al study the magneto-chiral interactions in a small asymmetric magnetic cap, and show how the geometric asymmetry influence the chiral spin- textures. [ABSTRACT FROM AUTHOR]

Two Heusler compounds NiRh2Sb and CuRh2Sb were synthesized for the first time and their crystal structures were determined by combined X-ray diffraction and high-resolution electron microscopy. Two synthesis routes were applied: a one-pot polyol reduction of metal cations at 280–290 °C under microwave radiation yielded nanocrystalline particles of 3–6 nm, whereas intergrown microcrystalline samples were obtained by conventional high-temperature synthesis at 700 °C starting from the elements. NiRh2Sb is an orthorhombic Heusler compound that crystallizes in space group Cmcm with lattice parameters a = 6.9188(1) Å, b = 5.7917(1) Å and c = 5.7374(1) Å. CuRh2Sb is dimorphic; depending on the synthesis conditions, it either adopts the cubic space group Fm3¯m with a lattice parameter of a = 6.1235(1) Å, or the tetragonal space group I4/mmm with lattice parameters a = 4.1859(1) Å and c = 6.6375(1) Å. The transition between the cubic and tetragonal structures of CuRh2Sb is attributed to a reversible band Jahn–Teller distortion as suggested by density functional theory-based calculations. Electrical resistivities evidence metallic behavior for both compounds in accordance with the computed band structures and the density-of-states. Both compounds are Pauli paramagnetic and show no magnetic ordering between room temperature and 2 K. The electrocatalytic performances of the nano-scale intermetallics were tested with the electrolysis of water, and both were found to greatly reduce the overpotential of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with a large electrochemically active surface area. [ABSTRACT FROM AUTHOR]

Magnetic force microscopy (MFM) is a scanning microscopy technique that is commonly employed to probe the sample's magnetostatic stray fields via their interaction with a magnetic probe tip. In this work, a quantitative, single-pass MFM technique is presented that maps one magnetic stray-field component and its spatial derivative at the same time. This technique uses a special cantilever design and a special high-aspect-ratio magnetic interaction tip that approximates a monopole-like moment. Experimental details, such as the control scheme, the sensor design, which enables simultaneous force and force gradient measurements, as well as the potential and limits of the monopole description of the tip moment are thoroughly discussed. To demonstrate the merit of this technique for studying complex magnetic samples it is applied to the examination of polycrystalline MnNiGa bulk samples. In these experiments, the focus lies on mapping and analyzing the stray-field distribution of individual bubble-like magnetization patterns in a centrosymmetric [001] MnNiGa phase. The experimental data is compared to calculated and simulated stray-field distributions of 3D magnetization textures, and, furthermore, bubble dimensions including diameters are evaluated. The results indicate that the magnetic bubbles have a significant spatial extent in depth and a buried bubble top base. A quantitative magnetic force microscopy technique is presented that maps one magnetic stray-field component and its spatial derivative at the same time. Furthermore, this technique is applied to investigate individual circular magnetic nano-domains in MnNiGa bulk samples providing bubble diameters and the spatial extent in depth. [ABSTRACT FROM AUTHOR]

The combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane‐formed whispering‐gallery‐mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions. [ABSTRACT FROM AUTHOR]

The synthesis of 2D layered double hydroxides (LDHs) monolayer remains a major challenge for energy conversion and storage. Herein, a one‐pot strategy is reported to synthesize nitrate‐intercalated nickel–iron LDHs (NiFe LDHs_NO3−) by using hexamethylenetetramine as a hydrolysis reagent. The NiFe LDHs monolayers can be facilely dispersed in water within 10 s by hand shaking because the NiFe LDHs_NO3− bulk owns an enlarged interlayer spacing up to 8.2 Å. Critical information on the structure, prerequisite, and universality of this strategy is obtained by advanced characterization methods, for example, transmission electron microscopy, atomic force microscopy, X‐ray diffraction pattern, Fourier‐transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. As a proof of concept application, the NiFe LDHs monolayer is employed as an electrocatalyst for oxygen evolution reaction and displays much superior performance to the bulk LDHs and RuO2. This facile strategy paves the way for designing other LDHs monolayers for highly active electrocatalysts. [ABSTRACT FROM AUTHOR]

Tunable electromagnets and corresponding devices, such as magnetic lenses or stigmators, are the backbone of high-energy charged particle optical instruments, such as electron microscopes, because they provide higher optical power, stability, and lower aberrations compared to their electric counterparts. However, electromagnets are typically macroscopic (super-)conducting coils, which cannot generate swiftly changing magnetic fields, require active cooling, and are structurally bulky, making them unsuitable for fast beam manipulation, multibeam instruments, and miniaturized applications. Here, we present an on-chip microsized magnetic charged particle optics realized via a self-assembling micro-origami process. These micro-electromagnets can generate alternating magnetic fields of about ±100 mT up to a hundred MHz, supplying sufficiently large optical power for a large number of charged particle optics applications. That particular includes fast spatiotemporal electron beam modulation such as electron beam deflection, focusing, and wave front shaping as required for stroboscopic imaging. Electron beam manipulation is important for their application in microscopes, lithography instruments, and colliders. Here the authors report a wafer scale, self-assembled, microcoil electrically-driven magnetic charge particle optic device that can be implemented into different configurations for controlling of electron beams. [ABSTRACT FROM AUTHOR]

Recently a zoology of non-collinear chiral spin textures has been discovered, most of which, such as skyrmions and antiskyrmions, have integer topological charges. Here we report the experimental real-space observation of the formation and stability of fractional antiskyrmions and fractional elliptical skyrmions in a Heusler material. These fractional objects appear, over a wide range of temperature and magnetic field, at the edges of a sample, whose interior is occupied by an array of nano-objects with integer topological charges, in agreement with our simulations. We explore the evolution of these objects in the presence of magnetic fields and show their interconversion to objects with integer topological charges. This means the topological charge can be varied continuously. These fractional spin textures are not just another type of skyrmion, but are essentially a new state of matter that emerges and lives only at the boundary of a magnetic system. The coexistence of both integer and fractionally charged spin textures in the same material makes the Heusler family of compounds unique for the manipulation of the real-space topology of spin textures and thus an exciting platform for spintronic and magnonic applications. Skyrmions and anti-skyrmions are magnetic textures that have garnered much interest due to their stability. Here, Jena et al demonstrate the existence of fractional spin textures at the edges of Heusler alloy sample, which can have continuous variable topological charges. [ABSTRACT FROM AUTHOR]

In this chapter, different strategies to study statics and dynamics of magnetic textures on curved nano- and micro-architectures will be discussed. The methods will include not only top-view imaging using conventional scanning or full-fieldmicroscopes (forcemicroscopes and optical microscopes) but also neutronbased, electron-based and X-ray-based (soft and hardX-rays) holography and tomography techniques. The fundamentals of vector field tomography will be provided. Specific examples will be introduced. Challenges and outlook to further development of the methodology will be given. [ABSTRACT FROM AUTHOR]

Hybrid metallic nanoparticles (NPs) encapsulated in oxide shells are currently intensely studied for plasmonic applications in sensing, medicine, catalysis, and photovoltaics. Here, a method for the synthesis of Au@Ag@SiO2 cubes with a uniform silica shell of variable and adjustable thickness in the nanometer range is introduced and their excellent, highly reproducible, and tunable optical response is demonstrated. Varying the silica shell thickness, the excitation energies of the single NP plasmon modes can be tuned in a broad spectral range between 2.55 and 3.25 eV. Most importantly, a strong coherent coupling of the surface plasmons is revealed at the silver–silica interface with Mie resonances at the silica–vacuum interface leading to a significant field enhancement at the encapsulated NP surface in the range of 100% at shell thicknesses t ≃ 20 nm. Consequently, the synthesis method and the field enhancement open pathways to a widespread use of silver NPs in plasmonic applications including photonic crystals and may be transferred to other non‐precious metals. [ABSTRACT FROM AUTHOR]

Chains of coupled metallic nanoparticles are of special interest for plasmonic applications because they can sustain highly dispersive plasmon bands, allowing strong ballistic plasmon wave transport. Whereas early studies focused on homogeneous particle chains exhibiting only one dominant band, heterogeneous assemblies consisting of different nanoparticle species came into the spotlight recently. Their increased configuration space principally allows engineering multiple bands, bandgaps, or topological states. Simultaneously, the challenge of the precise arrangement of nanoparticles, including their distances and geometric patterns, as well as the precise characterization of the plasmonics in these systems, persists. Here, the surface plasmon resonances in heterogeneous AgAu nanoparticle chains are reported. Wrinkled templates are used for directed self‐assembly of monodisperse gold and silver nanospheres as chains, which allows assembling statistical combinations of more than 109 particles. To reveal the spatial and spectral distribution of the plasmonic response, state‐of‐the‐art scanning transmission electron microscopy coupled with electron energy loss spectroscopy accompanied by boundary element simulations is used. A variety of modes in the heterogeneous chains are found, ranging from localized surface plasmon modes occurring in single gold or silver spheres, respectively, to modes that result from the hybridization of the single particles. This approach opens a novel avenue toward combinatorial studies of plasmonic properties in heterosystems. [ABSTRACT FROM AUTHOR]

The emergence of topological insulators (TIs) raised high expectations for their application in quantum computers and spintronics. Being bulk semiconductors, their nontrivial topology at the electronic bandgap enables dissipation-free charge and spin transport in protected metallic surface states. For application, crystalline thin films are requested in sufficient quantity. A suitable approach is the liquid phase exfoliation (LPE) of TI crystals that have layered structures. Bi2TeI is a weak 3D TI, which leads to protected edge states at the side facets of a crystal, as well as a topological crystalline insulator, which is responsible for protected states at the top and bottom faces. We developed an effective, scalable protocol for LPE of freestanding nanoflakes from Bi2TeI crystals. By heat treatment and sonication in isopropyl alcohol and poly(vinylpyrrolidone), crystalline Bi2TeI sheets with a thickness of ~50 nm were obtained and can therefore be considered for further processing toward microelectronic applications. [ABSTRACT FROM AUTHOR]

The layered salt Bi14Rh3I9 is a weak three‐dimensional (3D) topological insulator (TI), that is, a stack of two‐dimensional (2D) TIs. It has a wide non‐trivial band gap of 210 meV, which is generated by strong spin‐orbit coupling, and possesses protected electronic edge‐states. In the structure, charged layers of ∞2[ (Bi4Rh)3I]2+ honeycombs and ∞1[ Bi2I8]2− chains alternate. The non‐trivial topology of Bi14Rh3I9 is an inherent property of the 2D intermetallic fragment. Here, the exfoliation of Bi14Rh3I9 was performed using two different chemical approaches: (a) through a reaction with n‐butyllithium and poly(vinylpyrrolidone), (b) through a reaction with betaine in dimethylformamide at 55 °C. The former yielded few‐layer sheets of the new compound Bi12Rh3I, while the latter led to crystalline sheets of Bi14Rh3I9 with a thickness down to 5 nm and edge‐lengths up to several ten microns. X‐ray diffraction and electron microscopy proved that the structure of Bi14Rh3I9 remained intact. Thus, it was assumed that the particles are still TIs. Dispersions of these flakes now allow for next steps towards the envisioned applications in nanoelectronics, such as the study of quantum coherence in deposited films, the combination with superconducting particles or films for the generation of Majorana fermions, or studies on their behavior under the influence of magnetic or electric fields or in contact with various materials occurring in devices. The method presented generally allows to exfoliate layers with high specific charges and thus the use of layered starting materials beyond van der Waals crystals. [ABSTRACT FROM AUTHOR]

We introduce a three-step seed-mediated synthesis for single crystalline gold nanoparticles (Au NPs) stabilized by hexadecylpyridinium chloride (CPC) in variable sizes with an independently adjustable ratio of the cubic and octahedral facets. The effect of KBr and ascorbic acid (AA) on shape and growth kinetics is systematically investigated. The kinetic data were evaluated using the minimalistic Finke–Watzky autocatalytic two-step mechanism, which allows to estimate the rate constants of the "pseudoelementary" reactions. The proposed surface-mediated mechanism of reduction of gold ions and Au NP growth allows to explain the effect of gradual increase of bromide ion concentration on switching the Au NP morphology from cubic to octahedral. The plasmonic properties of single particles of different facetings and their assemblies are investigated. [ABSTRACT FROM AUTHOR]

An often-overlooked property of transition metal oxide thin films is their microscopic surface structure and its effect on the electronic properties in the ultrathin limit. Contrary to the expected conservation of the perovskite stacking order in the (001) direction, heteroepitaxially grown SrIrO3 films on TiO2-terminated SrTiO3 are found to exhibit a terminating SrO surface layer. The proposed mechanism for the self-organized conversion involves the adsorption of excess oxygen ions at the apical sites of the IrO2-terminated surface and the subsequent decomposition of the IrO6 octahedra into gaseous molecular IrO3 and the remaining SrO-terminated surface. Whereas the ab initio calculated electronic structure of SrO-terminated SrIrO3 in the monolayer limit exhibits a striking similarity to bulk Sr 2 IrO 4 , the broken octahedral symmetry at the IrO2-terminated surface would mix the otherwise crystal field split eg and t 2 g states, resulting in distinctly different low-energy electronic states. [ABSTRACT FROM AUTHOR]

In the present work, different synthesis procedures have been demonstrated to fill carbon nanotubes (CNTs) with Fe1-xNix alloy nanoparticles (x = 0.33, 0.5). CNTs act as templates for the encapsulation of magnetic nanoparticles, and provide a protective shield against oxidation as well as prevent nanoparticles agglomeration. By variation of the reaction parameters, the purity of the samples, degree of filling, the composition and size of filling nanoparticles have been tailored and therefore the magnetic properties. The samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Bright-field (BF) TEM tomography, X-ray powder diffraction, superconducting quantum interference device (SQUID) and thermogravimetric analysis (TGA). The Fe1-xNix-filled CNTs show a huge enhancement in the coercive fields compared to the corresponding bulk materials, which make them excellent candidates for several applications such as magnetic storage devices. [ABSTRACT FROM AUTHOR]

Static electromagnetic stray fields around nanowires (NWs) are characteristic for a number of important physical effects such as field emission or magnetic force microscopy. Consequently, an accurate characterization of these fields is of high interest and electron holographic tomography (EHT) is unique in providing tomographic 3D reconstructions at nm spatial resolution. However, several limitations of the experimental setup and the specimen itself are influencing EHT. Here, we show how a deliberate restriction of the tomographic reconstruction to the exterior of the NWs can be used to mitigate these limitations facilitating a quantitative 3D tomographic reconstruction of static electromagnetic stray fields at the nanoscale. As an example, we reconstruct the electrostatic stray field around a GaAs-AlGaAs core shell NW and the magnetic stray field around a Co2FeGa Heusler compound NW. [ABSTRACT FROM AUTHOR]

Electron holography at medium resolution simultaneously probes projected electrostatic and magnetostatic potentials as well as elastic and inelastic attenuation coefficients with a spatial resolution of a few nanometers. In this work, we derive how the elastic and inelastic attenuation can be disentangled. Using that result, we perform the first three dimensional tomographic reconstruction of potential and (in)elastic attenuation in parallel. The technique can be applied to distinguish between functional potentials and composition changes in nanostructures, as demonstrated using the example of a GaAs--Al0.33Ga0.67As core-shell nanowire. [ABSTRACT FROM AUTHOR]

For the characterization of light materials using transmission electron microscopy, a low electron acceleration voltage of 80 kV or even 60 kV is attractive due to reduced beam damage to the specimen. The concomitant reduction in resolving power of the microscope can be restored when using spherical aberration ( Cs) correctors, which for the most part are only available in the latest and most expensive microscopes. Here, we show that upgrading of existing TEMs is an attractive and cost-effective alternative. We report on the low-voltage performance on graphitic material of a JEOL JEM-2010F built in the early 1990s and retro-fitted with a conventional imaging Cs corrector and a probe Cs corrector. The performance data show Cs retro-fitted instruments can compete very favourably against more modern state-of-the-art instruments in both conventional imaging (TEM) and scanning (STEM) modes. [ABSTRACT FROM AUTHOR]

Strain engineering enables modification of the properties of thin films using the stress from the substrates on which they are grown. Strain may be relaxed, however, and this can also modify the properties thanks to the coupling between strain gradient and polarization known as flexoelectricity. Here we have studied the strain distribution inside epitaxial films of the archetypal ferroelectric PbTiO3, where the mismatch with the substrate is relaxed through the formation of domains (twins). Synchrotron X-ray diffraction and high-resolution scanning transmission electron microscopy reveal an intricate strain distribution, with gradients in both the vertical and, unexpectedly, the horizontal direction. These gradients generate a horizontal flexoelectricity that forces the spontaneous polarization to rotate away from the normal. Polar rotations are a characteristic of compositionally engineered morphotropic phase boundary ferroelectrics with high piezoelectricity; flexoelectricity provides an alternative route for generating such rotations in standard ferroelectrics using purely physical means. [ABSTRACT FROM AUTHOR]