Palladium hydride is a model system for studying metal-hydrogen interactions. Yet, its bulk electronic structure has proven difficult to directly probe, with most studies to date limited to surface-sensitive photoelectron spectroscopy approaches. This work reports the first in situ ambient-pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) study of hydrogen incorporation in Pd thin films, providing direct access to bulk chemical and electronic information at elevated hydrogen pressures. Structural characterization by in situ X-ray diffraction and neutron reflectometry under comparable conditions establishes a direct correlation between hydrogen loading, lattice expansion, and electronic modifications. Comparison with density functional theory (DFT) reveals how hydrogen stoichiometry and site occupancy govern the density of occupied states near the Fermi level. These results resolve long-standing questions regarding PdH and establish AP-HAXPES as a powerful tool for probing the bulk electronic structure of metal hydrides under realistic conditions.

Organic-inorganic alkylammonium halides of the A 5 B 2 X 11 form exhibit ferroic behaviour that is strongly dependent on their crystal symmetry, yet the role of the organic A-site and the bioctahedral connectivity governing this behaviour remains poorly understood. Here, a new A 5 B 2 X 11 compound, formamidinium bismuth bromide FA 5 Bi 2 X 11 (FA = CH(NH 2 ) 2 ) has been synthesised using a counter diffusion crystal growth (CDCG) method in silica gel. Structural analysis from single crystal X-ray diffraction reveals that FA 5 Bi 2 Br 11 belongs to the Pnnm orthorhombic space group. The effect of formamidinium as the organic cation and its effect on the structural symmetry within the A 5 B 2 X 11 family is explored. The connectivity of bioctahedral [BiBr 11 ] 5- via equitiorial Br - ions and increased orientational freedom of the formamidinium ion in its cation cavity stabilise centrosymmetry, suppressing polar distortion at room temperature. Electrical measurements confirm the structural predication of suppressed ferroelectricity due to preservation of inversion symmetry. This establishes a structure-property relationship and the role of the A-site cation in crystal symmetry and ferroic behaviour for these complex organic-inorganic halides.

Degradation of near surface nitrogen vacancy (NV) centers in diamond under optical illumination has restricted their deployment in applications such as scanning NV magnetomety, particularly under harsh environment such as low temperatures and vacuum. Previously, alumina passivation of planar diamond samples has been shown to reduce the degradation of near surface ensemble NV centers in vacuum. Here, we expand this study to incorporate photonic nanostructures by analyzing the single photon emission characteristics of NV centers embedded in an array of alumina-coated diamond nanopillars in high vacuum and low temperature (6K, high vacuum) environments under non-resonant (522 nm) laser exposure. We find that, in contrast to the oxygen-terminated diamond nanopillars, NV centers in the alumina-coated nanopillars demonstrate negligible change in the single photon purity and brightness over the course of laser exposure in vacuum. At low temperature, NV centers under alumina termination demonstrate stable single photon emission, whereas under oxygen termination the single photon purity degrades under high intensity laser exposure. Alumina surface passivation is therefore shown as a viable path toward the realization of robust NV-diamond based nanoscale sensing under non-ambient atmospheric environments, including using diamond scanning probes.

Amino acids are essential building blocks of life, yet our understanding of their chemistry and electronic structure in the solid state remains limited. This is particularly important because amino acids in the solid state are relevant to biological and pharmaceutical processes. X-ray photoelectron spectroscopy provides a powerful experimental probe of chemical states and occupied electronic structure; however, most spectroscopy studies of amino acids focus on gas-phase species or surface adsorbates, while crystalline amino acids remain underexplored, largely because of experimental challenges associated with radiation damage. Additionally, the spectra are often complex and difficult to interpret, motivating a combined experimental-theoretical approach. This study combines X-ray photoelectron spectroscopy and density functional theory calculations to systematically investigate the core, semi-core, and valence states of 20 proteinogenic amino acids as well as selenomethionine which can be incorporated during protein synthesis and deliver the essential nutrient, Se, required by humans. Calculated relative core binding energies show excellent agreement with experiment and enable reliable assignments. Projections of the density of states provide insight into the influence of local coordination and extended crystal structure, yielding a systematic understanding of the electronic structure and bonding in solid-state AAs. The insights gained from this study enhance the understanding of crystalline amino acids and validate the robustness of an integrated experiment–theory framework.

with indium tin oxide (ITO) top contacts. Constant-current electrical stress reveals that ITO-contacted devices exhibit chaotic conductance fluctuations and a single-phase transient in which the slow decay is suppressed, unlike the smooth, two-phase rise-and-decay response of devices with Au/Ti contacts. Through X-ray photoelectron spectroscopy depth profiling, spectroscopic evidence is provided that proton-driven electrochemical reduction of the ITO electrode decouples the two processes that the gold-contacted transient superimposes, leaving the initial con- ductance increase attributed to bulk oxide changes while suppressing the slow decay phase normally observed in gold-contacted devices. Binding energy shifts in indium (∼0.9 eV) and accelerated interfacial etch rates in stressed devices suggest sub-stoichiometric ITO formation. By suppressing the slow proton screening that masks it in gold-contacted devices, the ITO contact exposes the underlying trap-discharge relaxation, which is dispersive (stretched-exponential exponent β = 0.54± 0.17) with a field-free discharge time of a few seconds. These findings reveal that nanoscale electrode material selection critically determines the physical mechanisms governing conductance dynamics in memristive devices, with implications for neuromorphic computing and reliable nanoelectronic design.

MAX phases are a class of compounds known for having both metallic and ceramic properties, such as good electrical conductivity, oxidation resistance, and high hardness. The bulk of the research on their properties focuses on those with titanium at the M-site and metals from groups 13 to 15, e.g., aluminum, at the A-site. Here, we expand the properties repertoire with new arsenic-containing A-site solid solutions, V2(As1-x P x )C and V2(As1-x Ge x )C. The structure and elemental composition of the solid solutions were resolved with powder X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and hard X-ray photoelectron spectroscopy. The electrical resistivity measurements show that both full series are metallic with the parent phases being the most conductive. Thermal analyses show V2GeC is the most oxidation resistant and V2AsC is the least, while substitutions decrease thermal stability, as oxidation resistance of the intermediate compositions shifts toward that of V2AsC. The V2(As1-x Ge x )C series shows little variation in hardness across compositions, while the incorporation of phosphorus noticeably increases hardness.

X-ray beam in a standard XPS measurement can rapidly trigger the PVDF degradation, which will trigger the subsequent formation of LiF on pristine, uncycled cathode surfaces.

Crystals of formamidinium antimony, halides, FA3Sb2X9 {FA = [CH(NH2)2]+; X = Br- and I-} {or triformamidinium nonahalidodiantimony, (CH5N2)3[Sb2X9]}, have been synthesized using a counter diffusion crystal growth (CDCG) method in silica gel and their structures determined from single-crystal X-ray diffraction data. FA3Sb2Br9 belongs to the trigonal space group P3m1, which is known as the Cs3Bi2Br9 structure type, and FA3Sb2I9 belongs to the hexagonal space group P63/mmc, called the Cs3Cr2Cl9 structure type. The change of the anion type from bromide to iodide results in the change of the structure type and the connectivity of the Sb-X octahedra. These structures are described and compared to the crystal types known for vacancy-ordered triple-perovskites.

This work presents a comprehensive investigation of the electronic structure and many-body photoemission effects in metallic platinum using reflection high-energy electron energy-loss spec- troscopy (RHEELS), soft X-ray photoelectron spectroscopy (SXPS), and hard X-ray photoelectron spectroscopy (HAXPES), supported by ab initio calculations. Shallow and deep core state spectra enable the systematic characterisation of intrinsic line-shape asymmetries and satellite structures. Correlation of photoelectron satellites with RHEELS loss features allows the assignment of inter- band transitions, surface and bulk plasmons, plasmonic overtones, and semi-core ionisation losses across the Pt spectrum. Several previously unresolved satellite features and spin-orbit splittings are identified and discussed. Comparison of experimental valence band spectra with orbital-projected densities of states calculated using ab initio density functional theory (DFT) and G0W0 approaches, with and without spin-orbit coupling, demonstrates the critical role of relativistic effects in reproducing the Pt valence electronic structure. Together, these results establish a unified, internally consistent spectroscopic reference for metallic platinum, providing a robust framework for interpreting photoelectron spectra of Pt-containing catalysts, electronic materials, and related 5d transition metal systems.

Nickel- and cobalt-based molybdates, AMoO 4 , where A = Ni, Co, or Ni/Co, are of significant interest owing to their temperature-dependent phase behaviour and promising performance in electrochemical applications, particularly glucose...

An investigation of the electronic structure of K 2 SiF 6 based on GW theory and photoelectron spectroscopy reveals that Auger–Meitner decay of K 3p holes is energetically forbidden in this material.

A correlation between depth-resolved defect chemistry and operando electrochemical response is established for compositionally graded gadolinia-doped ceria (GDC)/yttria-stabilized zirconia (YSZ) thin film electrodes.

MAX phases are an extremely versatile family of layered compounds that usually consist of an early to-mid transition metal (M-element), a main group element (mainly groups 13-15) or late transition metal (A-element) and carbon and/or nitrogen (X-element). It is therefore not too surprising that in addition to the roughly 70 compounds with 211 stoichiometry, there exist many solid solutions with mixed elements on the M- and A-site, respectively. Much less common are solid solution phases with mixed elements on both M- and A-site simultaneously (double-site solid solutions), as well as solid solutions on the X-site (carbonitride MAX phases). Challenging these restrictions in the chemical composition space, we present here for the first time (V0.2Cr0.8)2(Ga0.5Ge0.5)(C0.6N0.4) as a new carbonitride member of the MAX phase family, containing solid solutions on all three lattice sites simultaneously. This triple-site solid solution MAX phase is synthesized by high-temperature solid-state methods, and we demonstrate that it is possible to use two different nitrogen-containing precursors (VN and Cr2N), respectively. Structure, morphology and chemical composition are characterized by X-ray powder diffraction (XRD), electron microscopy (SEM/TEM), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (HAXPES).

MAX phases are a class of compounds known for having both metallic and ceramic properties, such as good electrical conductivity, oxidation resistance, and high hardness. The bulk of the research on their properties focuses on those with titanium at the M-site and metals from groups 13 to 15, e.g., aluminum, at the A-site. Here, we expand the properties repertoire with new arsenic-containing A-site solid solutions, V2(As1-xPx)C and V2(As1-xGex)C. The structure and elemental composition of the solid solutions were resolved with powder X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and hard X-ray photoelectron spectroscopy. The electrical resistivity measurements show that both full series are metallic with the parent phases being the most conductive. Thermal analyses show V2GeC is the most oxidation resistant and V2AsC is the least, while substitutions decrease thermal stability, as oxidation resistance of the intermediate compositions shifts toward that of V2AsC. The V2(As1-xGex)C series shows little variation in hardness across compositions, while the incorporation of phosphorus noticeably increases hardness.

Thermal decomposition is a powerful and scalable method for producing highly uniform metal oxide nanoparticles (MONPs). However, the hydrophobic ligands vital for controlling nanocrystal growth prevent MONPs' dispersion in aqueous media, limiting their direct use in biomedical applications. Ligand exchange strategies are commonly employed but typically suffer from inefficiency, limited scalability, and reliance on costly or custom-synthesized ligands. This study presents a facile, rapid, and scalable ligand exchange method for MONPs synthesized via thermal decomposition using sodium tripolyphosphate (STPP), a commercially available, biocompatible ligand with strong affinity for multivalent metal cations. This one-step process achieves effective exchange within 30 min at room temperature and is effective on gram-scale batches of nanoparticles capped with oleylamine, oleic acid, or sodium oleate. The resulting water-dispersible nanoparticles display long-term aqueous colloidal stability, strong surface charge, and retention of their intrinsic magnetic properties. The broad versatility of this method is further demonstrated by applying it to doped iron oxide, manganese oxide, and gadolinium oxide nanoparticles, highlighting its potential as a universal solution for biomedical translation. Finally, facile subsequent functionalization of the hydrophilic MONPs with silica and polydopamine shells provides adaptable platforms for imaging, drug delivery, and other bioapplications.

We report a study of current transient behaviour in silicon oxide memristive devices with indium tin oxide (ITO) top contacts. Constant-current electrical stress reveals that ITO-contacted devices exhibit chaotic conductance fluctuations and a single-phase transient in which the slow decay is suppressed, unlike the smooth, two-phase rise-and-decay response of devices with Au/Ti contacts. Through X-ray photoelectron spectroscopy depth profiling, spectroscopic evidence is provided that proton-driven electrochemical reduction of the ITO electrode decouples the two processes that the gold-contacted transient superimposes, leaving the initial conductance increase attributed to bulk oxide changes while suppressing the slow decay phase normally observed in gold-contacted devices. Binding energy shifts in indium (~0.9 eV) and accelerated interfacial etch rates in stressed devices suggest sub-stoichiometric ITO formation. By suppressing the slow proton screening that masks it in gold-contacted devices, the ITO contact exposes the underlying trap-discharge relaxation, which is dispersive (stretched-exponential exponent β = 0.54 ± 0.17) with a field-free discharge time of a few seconds. These findings reveal that nanoscale electrode material selection critically determines the physical mechanisms governing conductance dynamics in memristive devices, with implications for neuromorphic computing and reliable nanoelectronic design.

The chemical versatility of MAX phases has increased almost exponentially over the last two decades, especially because of the synthesis/discovery of new solid solution phases. Many elements challenge the traditional ternary MAX phase compositions because they can be incorporated into the structure by alloying with another element, despite not forming MAX phases by themselves. Examples are (mid-to-late) transition metals that can adopt the A-site in MAX phases, some even as the sole A-element (Fe through Zn). For solid solutions, Sn has proven to be a willing A-site partner for many transition metals (Mn, Fe, Co, and Ni), even for more than one at a time. Where is the limit of transition metals that form A-site solid solutions? In this work, we demonstrate a screening of all 3d metals, except for Sc, partially substituting Sn in MAX phase Nb2SnC. We show the successful incorporation of up to 40% of V to Zn 3d metals (except for Ti), where V and Cr occupy the A-site of the MAX phase, which is demonstrated for the first time. The full series of solid solution Nb2(Sn1-xAx)C with A = V, & mldr;, Zn is studied in detail by diffraction, microscopy, and spectroscopy techniques, as well as DFT calculations, and the influence of the A-elements on the magnetic properties is discussed.

Applications of transition-metal dichalcogenides (TMDs) are affected by defects and oxidation in air. In this work, we clarify the relationship between oxidation dynamics and O2 availability for highly defective (and therefore reactive) surfaces of WS2 crystals. Grazing incidence Ar+ sputtering was used to induce a significant concentration of S vacancies in the sample, rendering it highly susceptible to oxidative degradation. In this paper we observe that oxidation occurs slowly under low O2 pressures (<10-4 mbar) due to reduced O2-vacancy interactions. At higher O2 pressures, the reaction progresses rapidly, as tracked by changes in the oxidation state of W using XPS. The density functional theory calculations support the experimentally observed changes in the oxidation state of W after sputtering and oxidation. They provide the mechanisms of O2 dissociation on S vacancy clusters, demonstrating that the reaction barrier depends on the coordination of surface W atoms. These results can be useful for protecting samples from degradation in device applications.

MAX phases are a large and growing family of transition metal-based ternary carbides and (carbo)nitrides, that have also attracted significant attention as precursors for a class of two-dimensional materials referred to as MXenes. The ability to partially substitute elements on the M-, A-, and X-sites of the layered crystal structure has expanded MAX phases to over 340 members known to date. They can be exfoliated to form single- and few-layer MXene sheets by removal of the A-element while maintaining the M- and X-elements of the precursor MAX phase. MXenes are extremely interesting materials with properties that are, among other factors, dependent on their chemical composition and offer a wide array of potential applications, for example for energy conversion. Here, we synthesize hitherto unknown solid solution MAX phases, (V1-y Mo y )2AlC (y = 0.0-0.5) and exfoliate all compounds with varying V/Mo ratios into the respective MXenes by hydrothermal treatment with in situ-formed hydrofluoric acid. The delaminated MXenes can be utilized for electrocatalytic reactions, here demonstrated for the hydrogen evolution reaction (HER). As the Mo content within the MXenes increases, electrocatalytic activity for HER improves, peaking at an overpotential of 394 mV at 10 mA cm-2 and a Tafel slope of 129 mV dec-1 for (V0.5Mo0.5)2CT x .