The formation of donor-acceptor complexes (DACs) between the electron donor Dibenzotetrathiafulvalene (DBTTF) and the acceptor Hexaazatriphenylenehexacarbonitrile (HATCN) results in a separated phase with a distinctly different crystal structure as well as optical absorption bands below the energy gaps of the two pristine materials. X-ray scattering and atomic force microscopy provide detailed insights into the film structure and morphology by systematic variation of the mixing ratio from pristine DBTTF to pristine HATCN. The measured electrical conductivity of thin films depends in a highly nonmonotonic manner on the composition of the mixture and shows significantly improved charge transport compared to the pristine films. The temperature-dependent conductivity, charge carrier concentration, and mobility were investigated across these compositions. Surprisingly, all compositions exhibited n-type behavior, except for pristine DBTTF. This behavior is explained by the electronic structure of the mixtures, as revealed by ultraviolet photoelectron spectroscopy, which indicates that charge injection and transport occur via the lowest unoccupied molecular orbital of the DAC and HATCN. Additionally, the observed electrical conductivity is strongly influenced by the morphology and structural ordering of the films. These findings offer valuable insights for the design of advanced materials with enhanced electrical performance.

Advances in X-ray and neutron sources, as well as in area-detector technologies, enable the recording of several terabytes of raw two-dimensional detector data in a single experiment. While several efficient integration and conversion tools are available for data collected in transmission geometry, analogous solutions for grazing-incidence diffraction (including grazing-incidence X-ray diffraction and grazing-incidence wide-angle X-ray scattering) experiments have not yet achieved the same level of efficiency. The development of new data analysis tools, including machine-learning-based software for X-ray data, necessitates the establishment of a standardized format for the converted data. To address these challenges, we have developed a new Python library, pygid, which is designed to facilitate fast data processing while providing compatibility with various raw data formats, a standardized data storage format and an intuitive interface for straightforward use. pygid supports three types of coordinate systems and both transmission and grazing-incidence geometries. It is capable of handling large datasets, performing one-dimensional line cuts and simulating expected Bragg peak positions for given structures. The package facilitates sample and experimental metadata curation in accordance with the FAIR principles. As an integral part of the broader mlgid pipeline, pygid serves as the initial step linking raw scattering patterns with machine learning tools for data analysis. The pygid package is accessible at https://github.com/mlgid-project.

Metal-free halide perovskites have recently emerged as promising candidates for optoelectronic applications. However, their synthesis has largely depended on water-based single-crystal growth that limits material diversity, scalability, and practical implementation. Here, we present a mechanochemical route to synthesize N,N-diazabicyclo[2.2.2]octonium (H-DABCO)-based halide perovskites from the (DABCO)(NH4)X3 (X = I, Br) compositions. The structural properties were confirmed by X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy. Thin films were prepared from mechanosynthetic powders by spin-coating and characterized by in-situ grazing incidence wide-angle scattering measurements, as well as by UV-vis absorption and steady-state photoluminescence spectroscopy. This mechanosynthetic strategy provides a scalable, environmentally friendly pathway to broaden the scope of metal-free perovskites and advance their potential in sustainable optoelectronic technologies.

HYPOTHESIS:Electrostatic interactions at aqueous interfaces play a central role in controlling the organization and stability of charged particle-laden films. In particular, the explicit dependence of interfacial electrostatics on ionic strength and ion valence might enable to both finely modulate the structure and properties of charged aqueous surfaces and to better understand the interfacial partitioning of electrolytes. This requires a comprehensive characterization of the electrostatic properties at both the nano and macroscale. EXPERIMENTS:Here, we combine in situ grazing-incidence small-angle X-ray scattering (GISAXS), Langmuir compression isotherms, and vibrating-plate surface potential measurements to investigate the interfacial electrostatics of model negatively charged silica nanoparticles adsorbed at the air-water interface in the presence of mono-, di-, and trivalent electrolytes at various ionic strengths. FINDINGS:We show that nanoparticle monolayers self-regulate their 2D organization to reach a common electrostatic steady state, characterized by a constant interfacial surface potential (ΔV ≈ 150 mV) and a fixed single-particle repulsive energy (U ≈ 2 × 10-23 J), independently of ionic strength and ion identity. Variations in electrolyte composition instead control the nanoparticle surface excess, which adjusts to compensate changes in the interfacial dipolar strength. Further, both the interfacial dipole moment and the effective screening constant follow ion-independent power-law scaling with ionic strength, while ion-specific effects appear only as concentration-independent pre-factors. These results i) demonstrate that electrostatic interactions at the interface are governed by a confined electrolyte environment which deviates from classical bulk mean-field predictions and ii) provide a quantitative framework for predicting and tuning the structure and stability of charged aqueous interfaces.

Thin film deposition on weakly interacting substrates exhibits a unique growth mode characterized by initially strong island formation and rapidly increasing roughness, which reaches a maximum and subsequently decreases as the film returns to a smooth morphology. Here we show this rough-to-smooth growth mode experimentally for two molecular systems with substantially different geometries, namely, the effectively spherical buckminsterfullerene (C_{60}) and the disk-like 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile. This growth mode is explained by a geometrical model that captures the basic mechanisms of multilayer island growth, island coalescence, and formation of a continuous film. Additionally, kinetic Monte Carlo simulations with minimal ingredients demonstrate that this mode generally occurs for weakly interacting substrates, providing quantitative estimates of parameters that characterize adsorbate-adsorbate and adsorbate-substrate interactions. Both the model and simulations accurately describe the experimental data and highlight the generic nature of the phenomenon, independently of the details of the interactions and the molecular flux, which opens up a path for controlling nanoscale film roughness.

Powder X-ray diffraction (PXRD) and X-ray absorption near-edge structure (XANES) spectroscopy are complementary techniques for probing cobalt-based (Co-based) Fischer–Tropsch synthesis (FTS) catalyst structures. PXRD reveals crystalline composition, while XANES provides information on coordination geometry and oxidation state. We developed a fast, automated measurement method, based on rapid selection of X-ray beam energy and a dedicated sample environment at beamline ID10 (ESRF), to combine in situ PXRD and XANES in a single experiment. This approach enables simultaneous monitoring of structural and electronic changes in Co-based FTS catalysts under in situ conditions up to 60 bar, offering a comprehensive view of catalyst dynamics.

The design of supramolecular assemblies based on phospholipid-porphyrinoid conjugates has attracted growing attention in recent years, particularly for biomedical applications. Here, we report two novel amphiphilic conjugates, ZnPor(PL)4 and ZnPc(PL)4, obtained by coupling four molecules of 1-myristoyl-2-(14-carboxymyristoyl)-sn-glycero-3-phosphocholine to zinc(II)-tetraaminophenylporphyrin or zinc(II)-tetraaminophthalocyanine, respectively. Their interfacial behavior, their supramolecular assemblies in aqueous media, and photophysical properties were systematically investigated. Monolayer studies at the air/buffer interface revealed distinct molecular orientations. ZnPor(PL)4 formed a compact and ordered monolayer with the porphyrin core pushed upward between lipid chains, whereas ZnPc(PL)4 exhibited expanded and less ordered monolayer due to the higher rigidity and planarity of the phthalocyanine macrocycle. In solution, ZnPor(PL)4 self-assembled into chiral nanofibers stabilized by π-π stacking and hydrogen bonding, whereas ZnPc(PL)4 generated planar bilayer-like membrane patches. Both assembled conjugates exhibited strong fluorescence quenching; notably, ZnPor(PL)4 displayed pronounced tetrasignate circular dichroism signals consistent with right-handed helical H-aggregates. Molecular dynamics simulations corroborated these findings and demonstrated that hydrogen bonding and intrinsic chirality of phospholipid headgroups govern the supramolecular helicity. Overall, this work highlights how chromophore structure controls interfacial orientation and self-assembly in lipid-porphyrinoid conjugates, offering design principles for light-responsive nanostructures with potential applications in photodynamic and photothermal therapies.

Two-dimensional (2D) hexagonal boron nitride (hBN) is a key dielectric for van der Waals nanoelectronics, however, its controlled synthesis by chemical vapor deposition remains challenging and poorly understood. In this context, the growth of hBN on liquid metal catalysts is promising, as the atomically flat liquid surfaces are assumed to promote high-quality 2D growth, an expectation largely informed by graphene. Here, we implement an involved operando methodology to monitor and quantify hBN growth on molten copper (Liq-Cu) and re-solidified single-crystal copper (SC-Cu) under near-ambient-pressure conditions, enabling real-time identification of growth stages, morphology, and interfacial structure. Contrary to expectation, Liq-Cu promotes multilayer and three-dimensional domain formation, whereas SC-Cu predominantly yields monolayer-limited growth. This substrate-phase dependence correlates with a larger adsorption height of hBN on Liq-Cu than on SC-Cu, as determined by X-ray reflectivity and supported by machine-learning-accelerated molecular dynamics simulations. Direct comparison with graphene on Cu further reveals a distinct directional bonding character at the hBN/Cu interface, which rationalizes the observed adsorption-height trends. More generally, these trends across 2D materials and substrates identify the resulting interfacial stabilization, together with macroscopic factors such as precursor solubility, as a complementary design parameter governing mono- vs. multilayer growth in 2D material synthesis.

The tear film lipid layer (TFLL) is the outermost layer of the tear film and forms a barrier between the eye and the environment. While the TFLL is important in maintaining ocular surface health, there remains a curtain of mystery surrounding its structure and function on the molecular level. This is the result of the complex composition of the lipid film, the challenging dynamic environment in which it is present and missing molecular level information on the properties displayed by its lipid constituents. We recently assessed whether state-of-the-art surface X-ray scattering techniques can be employed to study the properties of films formed by individual tear film lipids and found this approach to bear significant potential in addressing the current unknown parameters of these substrates. Herein, we perform a follow-up study utilizing an expanded library of molecules in order to uncover general trends displayed by distinct tear film lipid classes. Through the use of grazing incidence X-ray diffraction and X-ray reflectivity techniques, we determine the lattice distances, molecular tilt angles and film thickness of representative lipids featuring variations in branching patterns and chain lengths and take an important step toward a deeper understanding of the molecular level structure and function of individual tear film lipids.

A crucial aspect of the fabrication of optoelectronic devices based on organic small molecules is the understanding of the growth and the postgrowth effects in thin films of these molecules. One of the factors that can negatively impact the performance of a given material despite its suitability in terms of electrical and optical properties is the dewetting of the produced film. The present work reveals the growth behavior and the postgrowth effects in thin films of dibenzoselenadiazoloquinoxaline (dbSeQ), a new organic semiconductor, thin films of which tend to dewet on Si/SiO x substrates. To overcome this limiting feature, we deposited thin films of dbSeQ in combination with well-studied organic semiconductors, namely, diindenoperylene (DIP) and pentacene (PEN) at room and low substrate temperatures (RT and LT, respectively). Using X-ray scattering techniques, i.e. grazing-incidence small-angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR), we characterized the growth and the annealing of thin films in situ in real time. The combination of atomic force microscopy (AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS) and UV-Vis absorption spectroscopy provides additional important information about the morphology, structure and optical properties of the deposited films ex situ. We found that in thin films grown at RT, dbSeQ molecules predominantly adopt an edge-on orientation, which leads to formation of pronounced islands on the substrate. This growth mode of dbSeQ was also observed in bilayer and codeposited films with DIP and PEN. In case of LT growth, dbSeQ molecules adopt a lying orientation that in turn results in a very smooth dbSeQ layer. Further findings reveal pronounced structural and morphological changes in LT-grown films during their annealing to RT. These results are of great importance for understanding the growth of organic semiconductors incorporating fused 1,2,5-selenadiazoles and the factors that influence it, which can be used for the future development of thin film-based devices.

Nanoporous Cu produced by chemical dealloying is a promising catalyst for electrochemical CO2 reduction owing to its tunable chemistry, morphology, and surface defect sites. However, how dealloying controls the atomic-scale structure of Cu ligaments and how these features govern catalytic behavior remain unclear, particularly in nanostructured catalysts under realistic operating conditions. Here, we synthesize nanoporous Cu by dealloying Cu20Zn80 in H3PO4 at different temperatures, enabling control over ligament sizes from the nanoscale to the microscale. Nanoporous Cu outperforms polycrystalline Cu for CO reduction, with the sample dealloyed at 15 °C reaching 60

In recent years, liquid metal catalysts have emerged as a compelling choice for the controllable, large-scale, and high-quality synthesis of two-dimensional materials. At present, there is little mechanistic understanding of the intricate catalytic process, though, of its governing factors or what renders it superior to growth at the corresponding solid catalysts. Here, we report on a combined experimental and computational study of the kinetics of graphene growth during chemical vapor deposition on a liquid copper catalyst. By monitoring the growing graphene flakes in real time using in situ radiation-mode optical microscopy, we explore the growth morphology and kinetics over a wide range of CH4-to-H2 pressure ratios and deposition temperatures. Constant growth rates of the flakes' radius indicate a growth mode limited by precursor attachment, whereas methane-flux-dependent flake shapes point to limited precursor availability. Large-scale free energy simulations enabled by an efficient machine-learning moment tensor potential trained to density-functional theory data provide quantitative barriers for key atomic-scale growth processes. The wealth of experimental and theoretical data can be consistently combined into a microkinetic model that reveals mixed growth kinetics that, in contrast to the situation at solid Cu, is partly controlled by precursor attachment alongside precursor availability. Key mechanistic aspects that directly point toward the improved graphene quality are a largely suppressed carbon dimer attachment due to the facile incorporation of this precursor species into the liquid surface and a low-barrier ring-opening process that self-heals 5-membered rings resulting from remaining dimer attachments.

HYPOTHESIS:Graphene oxide-based nanotechnology has aroused a great interest due to its applications in the biomedical and optoelectronic fields. The wide use of these materials makes it necessary to study its potential toxicity associated with the inhalation of Graphene Oxide (GO) nanoparticles and its interaction with the lung surfactant. Langmuir monolayers have proven to be an excellent tool for studying the properties of the lung surfactant and the effect of intercalation of nanoparticles on its structure and properties. Therefore, to know the origin of the phospholipids/GO interaction and the structure of the lipid layer with GO, in this work we study the effect of the insertion of GO sheets on a Langmuir film of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC).EXPERIMENTS:Surface pressure-area isotherms, Neutron (NR) and X-ray Reflectivity (XRR) and Grazing Incidence X-ray Diffraction (GIXD) measurements of hydrogenated and deuterated DPPC monolayers with and without GO have been carried out.FINDINGS:The results outline a strong interaction between the GO and the zwitterionic form of DPPC and prove that GO is in three regions of the DPPC monolayer, the aliphatic chains of DPPC, the head groups and water in the subphase. Comparison between results obtained with hydrogenated and deuterated DPPC allows concluding that both, electrostatic attractions, and dispersion forces are responsible of the interaction GO/DPPC. Results also demonstrated that the insertion of GO into the DPPC aliphatic chains does not induce significant changes on unit cell of DPPC.

In this study, we investigated the self-ordering process in Langmuir films of polydisperse iron oxide nanoparticles on a water surface, employing in situ x-ray scattering, surface pressure-area isotherm analysis, and Brewster angle microscopy. X-ray reflectometry confirmed the formation of a monolayer, while grazing incidence small-angle x-ray scattering revealed short-range lateral correlations with a characteristic length equal to the mean particle size. Remarkably, our findings indicated that at zero surface pressure, the particles organized into submicrometer clusters, merging upon compression to form a homogeneous layer. These layers were subsequently transferred to a solid substrate using the Langmuir-Schaefer technique and further characterized via scanning electron microscopy and polarized neutron reflectometry. Notably, our measurements revealed a second characteristic length in the lateral correlations, orders of magnitude longer than the mean particle diameter, with polydisperse particles forming circular clusters densely packed in a hexagonal lattice. Furthermore, our evidence suggests that the lattice constant of this mesocrystal depends on the characteristics of the particle size distribution, specifically the mean particle size and the width of the size distribution. In addition, we observed internal size separation within these clusters, where larger particles were positioned closer to the center of the cluster. Finally, polarized neutron reflectometry measurements provided valuable insights into the magnetization profile across the layer.

Liquid metal catalysts (LMCats), primarily molten copper, have demonstrated their efficiency in the chemical vapour deposition (CVD) approach for synthesising highquality, large-area graphene. However, their high melting temperatures limit broader applications. Reducing the temperature of graphene production on LMCats would lead to a more efficient and cost-effective process. Here, we investigated the effects of alloying copper with a low-melting temperature metal on graphene growth in real -time. We examined a set of liquid copper-gallium alloy systems using two complementary in situ techniques: radiation -mode optical microscopy and synchrotron X-ray reflectivity (XRR). The microscopy observations revealed reduced catalytic activity and graphene quality degradation in compositions with gallium domination. The XRR confirmed the formation of single-layer graphene on alloys with up to 60 wt% of gallium. Furthermore, we detected a systematic increase in adsorption height on the alloys' surface, indicating weaker adhesion of graphene on gallium. These findings suggest that a trade -off between layer quality and cost reduction in production is feasible. Our results provide insights into the CVD synthesis of graphene on bimetallic liquid surfaces and underscore the potential of gallium-copper alloys for enabling the direct transfer of graphene from a liquid substrate, thereby addressing the limitations imposed by the high melting temperatures of conventional LMCats.

Lipid membranes that are separated from the surface of graphene by DNA tethers were prepared by surface functionalization with pyrene coupled to single-stranded DNA (ssDNA), followed by self-assembly of the mixture of ssDNA-functionalized phospholipid and the matrix phospholipids. The formation of uniform membranes was confirmed by fluorescence microscopy, and the structures of the systems before and after hybridization in the direction perpendicular to the global plane of the membranes were investigated using high-energy X-ray reflectivity. The thickness values of the DNA spacers (15 and 37 bp) calculated from the best-fit results were less than the expected thicknesses of the double-stranded DNA (dsDNA) chains taking the upright conformation, indicating that the DNA spacers are tilted with respect to the direction normal to the surface. The Young's moduli of the DNA-tethered membranes obtained by AFM nanoindentation showed higher values than the membranes with no DNA tethers, which suggests that the DNA layer resists against the compression, lifting up the membrane. Intriguingly, the presence of DNA tethers caused no increase in the yield depth. The smaller thickness values as well as the unchanged yield depth suggest that the dsDNA chains can tilt and rotate, which can be attributed to the flexible pyrene-DNA junction.

We achieved a tripling of the maximum range of perpendicular momentum transfer (q_z) of X-ray scattering from liquid surfaces using a double crystal deflector setup to tilt the incident X-ray beam. This is obtained by using Miller indices of the reflecting crystal atomic planes that are three times higher than usual. We calculate the deviation from the exact Bragg angle condition induced by a misalignment between the X-ray beam axis and the main rotation axis of the double crystal deflector and deduce a fast and straightforward procedure to align them. We show measurements of X-ray reflectivity up to q_z=7A^(-1) on the bare surface of liquid copper and on graphene on liquid copper.

AbstractGraphene is a perfect 2D crystal of covalently bonded carbon atoms and constitutes the building block for all graphitic structures. Its superior properties make it an attractive material for a variety of technological applications. However, mass production does not meet the initial expectations. Chemical Vapor Deposition (CVD) is currently the only available method for large‐scale automated production, but the produced graphene sheets suffer from structural and morphological defects that degrade considerably the mechanical and other physical properties of synthesized graphene. Recently, the use of liquid metal catalysts (LMCat) has been proposed as an alternative platform for facile and high‐quality synthesis of single‐crystal graphene. Herein, simultaneous Raman spectroscopy combined with mechanical testing is adopted confirming that the reinforcing efficiency of the LMCat graphene is greatly improved. In fact, the effective Young's modulus of LMCat graphene has been found ≈630 GPa, which is significantly higher than the graphene grown on solid Cu substrate due to differences in the morphology of Cu substrate. Overall, this work paves the way for the development of defect‐free graphene of quality comparable to exfoliated flakes, and this will have a major technological impact for many applications.

The tear film lipid layer (TFLL) is a unique biological membrane that serves a pivotal role in the maintenance of ocular surface health. Reaching an overarching understanding of the functional principle of the TFLL has been hampered by a lack of insights into the structural and functional roles played by individual lipid classes. To bridge this knowledge gap, we herein focus on studying films formed by principal lipid classes by surface scattering methods. Through grazing incidence X-ray diffraction and X-ray reflectivity studies, we reveal quantitative data about the lattice distances, molecular tilt angles, and mono/multilayer thickness and density profiles for central TFLL lipid classes under close to simulated physiological conditions. In addition, we discuss the correlation of the results to those obtained previously with the natural lipid composition of meibum.

Lipid-porphyrin conjugates are versatile compounds which can self-assemble into liposome-like structures with multifunctional properties. Most of the conjugates that have been described so far, consisted in grafting pyropheophorbide-a (Pyro-a) or other porphyrin derivatives through the esterification of the hydroxyl group in the sn-2 position of a lysophosphatidylcholine. However, despite the versatility of these conjugates, less is known about the impact of the lipid backbone structure on their 2D phase behavior at the air/water interface and more precisely on their fine structures normal to the interface as well as on their in-plane organization. Herein, we synthesized a new lipid-porphyrin conjugate (PyroLSM) based on the amide coupling of Pyro-a to a lysosphingomyelin backbone (LSM) and we compared its interfacial behavior to that of Pyro-a and Pyro-a conjugated lysophosphatidylcholine (PyroLPC) using Langmuir balance combined to a variety of other physical techniques. Our results provided evidence on the significant impact of the lipid backbone on the lateral packing of the conjugates as well as on the shape and size of the formed domains. Compared to Pyro-a and PyroLPC monolayers, PyroLSM exhibited the highest lateral packing which highlights the role of the lipid backbone in controlling their 2D organization which in turn may impact the photophysical properties of their assemblies.