Direct Evidence of Anomalous Peierls Transition-Induced Charge Density Wave Order at Room Temperature in Metallic NaRu2O4.

In the field of quantum materials, understanding anomalous behavior under charge degrees of freedom through bond formation is of fundamental importance, with two key concepts: Dimerization and charge order at different cation sites. The coexistence of both dimerization and charge ordering is unusually found in NaRu2O4, even in its metallic state at room temperature. Our work unveils the origin of the interplay of these effects within metallic single-crystalline NaRu2O4.

Boosting Amino Acid Synthesis with WO Sub-Nanoclusters.

The conversion of nitrate-rich wastewater and biomass-derived blocks into high-value products using renewably generated electricity is a promising approach to modulate the artificial carbon and nitrogen cycle. Here, a new synthetic strategy of WO sub-nanoclusters is reported and supported on carbon materials as novel efficient electrocatalysts for nitrate reduction and its coupling with α-keto acids. In acidic solutions, the NH-NHOH selectivity can also optimized by adjusting the potential, with the total FE exceeding 80% over a wide potential range.

Preparation of High-Quality Samples for MEMS-Based In-Situ (S)TEM Experiments.

A novel focused ion beam (FIB)-based methodology for the preparation of clean and artifact-free specimens on micro-electro-mechanical-system (MEMS)-based chips for in-situ electrical and electro-thermal experiments in a (scanning) transmission electron microscope ((S)TEM) is introduced. Owing to an alternative geometry, the lamellae are attached to a MEMS-based chip directly after the lift-out procedure and afterward further treated or thinned to electron transparency. The quality of produced lamellae on a chip resembles the quality of a classical FIB-prepared sample that is here demonstrated by high-resolution STEM imaging and analytical techniques.

Electron Ptychographic Phase Imaging of Beam-sensitive All-inorganic Halide Perovskites Using Four-dimensional Scanning Transmission Electron Microscopy.

Halide perovskites (HPs) are promising candidates for optoelectronic devices, such as solar cells or light-emitting diodes. Despite recent progress in performance optimization and low-cost manufacturing, their commercialization remains hindered due to structural instabilities. While essential to the development of the technology, the relation between the microscopic properties of HPs and the relevant degradation mechanisms is still not well understood.

Multi-scale characterization of Developmental Defects of Enamel and their clinical significance for diagnosis and treatment.

Developmental Defects of Enamel (DDE) such as Dental Fluorosis (DF) and Molar Incisor Hypomineralization (MIH) are a major public health problem. Their clinical aspects are extremely variable, challenging their early and specific diagnosis and hindering progresses in restorative treatments. Here, a combination of macro-, micro- and nano-scale structural and chemical methods, including, among others, Atom Probe Tomography recently applied on tooth enamel, were used to study and compare MIH, DF and healthy teeth from 89 patients.

Synthesis, Characterization, and Electronic Properties of ZnO/ZnS Core/Shell Nanostructures Investigated Using a Multidisciplinary Approach.

ZnO/ZnS core/shell nanostructures, which are studied for diverse possible applications, ranging from semiconductors, photovoltaics, and light-emitting diodes (LED), to solar cells, infrared detectors, and thermoelectrics, were synthesized and characterized by XRD, HR-(S)TEM, and analytical TEM (EDX and EELS). Moreover, band-gap measurements of the ZnO/ZnS core/shell nanostructures have been performed using UV/Vis DRS. The experimental results were combined with theoretical modeling of ZnO/ZnS (hetero)structures and band structure calculations for ZnO/ZnS systems, yielding more insights into the properties of the nanoparticles.

Crystalline Lattice-Confined Atomic Pt in Metal Carbides to Match Electronic Structures and Hydrogen Evolution Behaviors of Platinum.

Platinum-based catalysts occupy a pivotal position in diverse catalytic applications in hydrogen chemistry and electrochemistry, for instance, the hydrogen evolution reactions (HER). While adsorbed Pt atoms on supports often cause severe mismatching on electronic structures and HER behaviors from metallic Pt due to the different energy level distribution of electron orbitals. Here, the design of crystalline lattice-confined atomic Pt in metal carbides using the Pt-centered polyoxometalate frameworks with strong PtO-metal covalent bonds is reported.

Synergistic use of gradient flipping and phase prediction for inline electron holography.

Inline holography in the transmission electron microscope is a versatile technique which provides real-space phase information that can be used for the correction of imaging aberrations, as well as for measuring electric and magnetic fields and strain distributions. It is able to recover high-spatial-frequency contributions of the phase effectively but suffers from the weak transfer of low-spatial-frequency information, as well as from incoherent scattering. Here, we combine gradient flipping and phase prediction in an iterative flux-preserving focal series reconstruction algorithm with incoherent background subtraction that gives extensive access to the missing low spatial frequencies.

Hybrid Graphene-Supported Aluminum Plasmonics.

Controlled fabrication of devices for plasmonics on suspended graphene enables obtaining tunable localized surface plasmon resonances (LSPRs), reducing the red-shift of LSPRs, and creating hybrid 3D-2D systems promising for adjustable dipole-dipole coupling and plasmon-mediated catalysis. Here, we apply a low-cost fabrication methodology to produce patterned aluminum nanostructures (bowties and tetramers) on graphene monolayers via electron-beam lithography and trap platinum (Pt) nanoclusters (NCs) within their hotspots by thermal annealing. We reveal the LSPRs of aluminum plasmonics on graphene using electron energy-loss spectroscopy (EELS) and energy-filtered transmission electron microscopy (EFTEM) in a monochromated scanning transmission electron microscope (STEM).

Uncovering the Evolution of Low-Energy Plasmons in Nanopatterned Aluminum Plasmonics on Graphene.

We report adjusting the charge-transfer-plasmon (CTP) resonances of aluminum (Al) bowties on suspended monolayer graphene via controlled nanofabrication and focused electron-beam irradiation. CTP resonances of bowties with a conductive junction blue-shift with an increase in junction width, whereas their 3λ/2 and λ resonances barely red-shift. These plasmon modes are derived and confirmed by an LC circuit model and electromagnetic simulations performed with boundary-element and frequency-domain methods.

Coexisting commensurate and incommensurate charge ordered phases in CoO.

The subtle interplay of strong electronic correlations in a distorted crystal lattice often leads to the evolution of novel emergent functionalities in the strongly correlated materials (SCM). Here, we unravel such unprecedented commensurate (COM) and incommensurate (ICOM) charge ordered (CO) phases at room temperature in a simple transition-metal mono-oxide, namely CoO. The electron diffraction pattern unveils a COM ([Formula: see text]=[Formula: see text] and ICOM ([Formula: see text]) periodic lattice distortion.

Hollow Mesoporous Carbon Spheres for High Performance Symmetrical and Aqueous Zinc-Ion Hybrid Supercapacitor.

Zinc-ion hybrid supercapacitors are a promising energy storage device as they simultaneously combine the high capacity of batteries and the high power of supercapacitors. However, the practical application of Zinc-ion hybrid supercapacitors is hindered by insufficient energy density and poor rate performance. In this study, a symmetrical zinc-ion hybrid supercapacitor device was constructed with hollow mesoporous-carbon nanospheres as electrode materials, and aqueous ZnSO adopted as an electrolyte.

Multiwavelength-Steerable Visible-Light-Driven Magnetic CoO-TiO Microswimmers.

While current light-driven microswimmers require high-intensity light, UV light, or toxic fuels to propel them, powering them with low-intensity UV-free visible light without fuels is essential to enable their potential high-impact applications. Therefore, in this study, a new material for light-driven microswimmers in the form of CoO is introduced. Janus CoO-TiO microswimmers powered with low-intensity, UV-free visible light inside water without using any toxic fuels like HO is proposed.

Secondary-Phase-Assisted Grain Boundary Migration in CuInSe_{2}.

Significant structural evolution occurs during the deposition of CuInSe_{2} solar materials when the Cu content increases. We use in situ heating in a scanning transmission electron microscope to directly observe how grain boundaries migrate during heating, causing nondefected grains to consume highly defected grains. Cu substitutes for In in the near grain boundary regions, turning them into a Cu-Se phase topotactic with the CuInSe_{2} grain interiors.

Radiation of Dynamic Toroidal Moments.

Dynamic toroidal dipoles, a distinguished class of fundamental electromagnetic sources, receive increasing interest and participate in fascinating electrodynamic phenomena and sensing applications. As described in the literature, the radiative nature of dynamic toroidal dipoles is sometimes confounded, intermixing with static toroidal dipoles and plasmonic dark modes. Here, we elucidate this issue and provide proof-of-principle experiments exclusively on the radiation behavior of dynamic toroidal moments.

Tuning the Size and Shape of NanoMOFs via Templated Electrodeposition and Subsequent Electrochemical Oxidation.

The control over the size and shape of nanoMOFs is essential for their exploitation in integrated devices such as sensors, membranes for gas separation, photoelectrodes, etc. Here, we demonstrate the synthesis of nanowires and three-dimensionally interconnected nanowire networks of Cu-based metal-organic frameworks (MOFs) by a combination of ion-track technology and electrochemical methods. In particular, Cu nanowires and nanowire networks were electrodeposited inside polymeric etched ion-track membranes and subsequently converted by electrochemical oxidation into different Cu-based MOFs such as the well-known Cu(BTC) (also known as HKUST-1) and the lesser-known MOF Cu(INA).

Silver nanowires with optimized silica coating as versatile plasmonic resonators.

Metal nanoparticles are the most frequently used nanostructures in plasmonics. However, besides nanoparticles, metal nanowires feature several advantages for applications. Their elongation offers a larger interaction volume, their resonances can reach higher quality factors, and their mode structure provides better coupling into integrated hybrid dielectric-plasmonic circuits.

Merging transformation optics with electron-driven photon sources.

Relativistic electron beams create optical radiation when interacting with tailored nanostructures. This phenomenon has been so far used to design grating-based and holographic electron-driven photon sources. It has been proposed recently that such sources can be used for hybrid electron- and light-based spectroscopy techniques.

Efficient first principles simulation of electron scattering factors for transmission electron microscopy.

Electron microscopy is a powerful tool for studying the properties of materials down to their atomic structure. In many cases, the quantitative interpretation of images requires simulations based on atomistic structure models. These typically use the independent atom approximation that neglects bonding effects, which may, however, be measurable and of physical interest.

High dose efficiency atomic resolution imaging via electron ptychography.

Radiation damage places a fundamental limitation on the ability of microscopy to resolve many types of materials at high resolution. Here we evaluate the dose efficiency of phase contrast imaging with electron ptychography. The method is found to be far more resilient to temporal incoherence than conventional and spherical aberration optimized phase contrast imaging, resulting in significantly greater clarity at a given dose.

Structure evolution of h.c.p./c.c.p. metal oxide interfaces in solid-state reactions.

The structure of crystalline interfaces plays an important role in solid-state reactions. The AlO/MgAlO/MgO system provides an ideal model system for investigating the mechanisms underlying the migration of interfaces during interface reaction. MgAlO layers have been grown between AlO and MgO, and the atomic structure of AlO/MgAlO interfaces at different growth stages was characterized using aberration-corrected scanning transmission electron microscopy.

Structural optimization and amorphous calcium phosphate mineralization in sensory setae of a terrestrial crustacean (Isopoda: Oniscidea).

Terrestrial isopods possess large sensory setae on their walking legs. Increased fracture resistance of these elongated structures is of crucial importance, making the exoskeleton forming the setae an interesting durable material that may inspire biomimetic designs. We studied the cuticle of the sensory setae with analytical electron microscopy in order to gain detailed insights into its structure and composition at the nanometer scale and identify features that increase the fracture resistance of these minute skeletal elements.

Exfoliation of a non-van der Waals material from iron ore hematite.

With the advent of graphene, the most studied of all two-dimensional materials, many inorganic analogues have been synthesized and are being exploited for novel applications. Several approaches have been used to obtain large-grain, high-quality materials. Naturally occurring ores, for example, are the best precursors for obtaining highly ordered and large-grain atomic layers by exfoliation.

Structure and chemistry of interfaces between ceria and yttria-stabilized zirconia studied by analytical STEM.

Epitaxial undoped and GdO-doped ceria films were grown by pulsed laser deposition on (1 1 1) faced YO-stabilized zirconia (YSZ). Highly localized cerium reduction at the film-substrate interfaces is revealed by atomically resolved valence EELS mapping using C aberration-corrected scanning transmission electron microscopy. The chemical profiles reveal interdiffusion of Ce, (Gd), Y, Zr, forming an intermixing zone at the interface 7-9 (1 1 1) lattice planes wide.