Elettra – Lightsources.org

Synchrotron imaging uncovers nano- and microplastic effects in vaginal epithelial cells

2026/04/012026/04/09

Environmental nano- and microplastics (N/MPs) are increasingly detected in human tissues, raising growing concerns about their potential impact on human health. Despite their pervasive presence, their biological effects at the cellular level remain poorly understood. A new multidisciplinary study provides important insights into how polyethylene (PE) N/MPs interact with human vaginal epithelial cells, revealing the induction of oxidative stress, metabolic disruption, and modulation of immune responses.

In this work, researchers exposed VK2 E6/E7 vaginal keratinocytes to a range of environmentally relevant PE N/MPs, spanning from 200 nm to 9 µm. Fluorescently labeled nanoparticles were also employed to enable precise tracking of particle uptake and intracellular localization. By combining advanced transcriptomic profiling with high-resolution imaging, the study offers a comprehensive view of how these particles affect cellular physiology.

Gene expression analysis revealed a significant dysregulation of lipid metabolism and cholesterol biosynthesis pathways, alongside the activation of oxidative stress responses. At the same time, modulation of immune-related genes suggested the onset of an adaptive, potentially tolerogenic response, indicating that cells may attempt to mitigate or adapt to the presence of nanoplastics rather than mounting a purely pro-inflammatory reaction. These findings highlight the complex and multifaceted nature of cellular responses to environmental contaminants.

Crucially, the study employed synchrotron-based soft X-ray imaging at the TwinMic beamline of Elettra Sincrotrone Trieste. Through Scanning Transmission X-ray Microscopy (STXM), researchers were able to directly visualize the internalization and intracellular distribution of nanoplastics at subcellular resolution, providing spatial information that is not accessible with conventional optical or electron microscopy alone, see Figure 1. Complementary Low-Energy X-ray Fluorescence (LEXRF) analysis enabled the mapping of elemental composition within exposed cells, revealing significant alterations in key elements such as carbon, oxygen, sodium, and magnesium. These elemental shifts point to metabolic stress, possible membrane perturbations, and broader changes in cellular homeostasis.

Biomaterials for Improving Ovarian Tissue Transplantation

2025/07/072025/07/10

Cryopreservation of ovarian tissue and its subsequent transplantation represent a big hope to preserve fertility in young women who have defeated cancer. Ovary revascularization is a crucial factor impacting the outcome of the engraftment. Limited oxygenation may have severe consequences on the ovarian reserve, with a significant loss of follicles. New frontiers in reproductive technology aim to reduce the ischemic/hypoxic window following auto-transplantation procedures. Biomaterials supplemented with ovarian-derived endothelial cells could be the solution to enhance vascular regeneration in the transplanted tissue.

In this study, we propose a combined Advanced Therapeutic Medicinal Product (ATMP) obtained from the association of cryopreserved ovarian tissue with a 3D dermal substitute — a biocompatible and bioactive scaffold employed in regenerative medicine — pre-seeded with vascular system cells previously isolated from the same ovarian tissue. This pre-seeding, known as inosculation, is a bioengineering approach aimed at enhancing revascularization by promoting the formation of novel vascular networks within the scaffold prior to implantation. The goal of the research is to demonstrate that a such graft can boost the growth of new vessels (Fig. 1), potentially improving the ovary survival and functionality.

To evaluate the effectiveness of this approach, several techniques were employed including synchrotron radiation-based X-ray phase-contrast microtomography (SR PC-microCT). As a volumetric imaging technique, SR PC-microCT enables three-dimensional visualization of the inner anatomical structures of the proposed ATMP at high spatial and contrast resolution, with the additional advantage of being non-destructive. Scans were carried out at the SYRMEP Imaging beamline of Elettra. The findings obtained by the X-ray images were complemented by histology and immunohistochemical analyses, adhesion and proliferation assays, gene expression and immunofluorescence.

A bovine collagen-based scaffold, Integra®, was selected among various dermal substitute materials tested and was used as a support for ovarian transplantation in subsequent in vivo experiments on mouse models. Histology clearly demonstrates the presence of endothelial cells within the Integra^® matrix, exhibiting a tendency to form vascular structures. Red-blood cells can be also observed inside the developing vessels (Fig. 2a). Similarly, Fig. 2b shows a virtual slice obtained by X-ray PC microCT of a sample region at the interface between the ovarian tissue and the Integra^® support. In agreement with the histological data, the X-ray image shows a massive accumulation of dense structures within the scaffold, which may be attributed to a high concentration of endothelial cells. Notably, SR PC microCT enables the cells distribution within the scanned blocks to be tracked, revealing a migration of the endothelial cells from the matrix into the tissue with a preferential side of accumulation. Supplementary videos are available on the full paper website (please follow the link at bottom of this page).

Spin-Charge Conversion in Sb2Te3-based heterostructures

2025/06/242025/06/24

Spin-charge interconversion (SCIC) refers to the conversion of pure charge currents into pure spin currents and vice versa. These fundamental phenomena can be exploited to generate and manipulate electronic states for use in spin-based logic and memory devices. A wide variety of materials with high spin-orbit coupling, including topological insulators (TIs), are emerging as promising candidates for the implementation of SCIC devices. Although TIs are insulating in the bulk, they exhibit spin-polarized conductive electronic states localized on their surfaces. These states, known as topological surface states (TSSs), exhibit spin-momentum locking, meaning their spin and momentum directions are mutually orthogonal in reciprocal space. This property of TIs makes them particularly attractive for the design of efficient SCIC devices. TSSs are robust against nonmagnetic disorders, such as defects and impurities, but are disrupted by the proximity of magnetic materials, which are essential parts of SCIC device. To practically utilize TI in devices, it is necessary to devise a method to separate the TI from the magnetic material while keeping the TSS properties unaffected.

In this study, we explored Au and Al metals, which are widely used in the electronics industry, as spacer materials between a TI (Sb₂Te₃) and a magnetic (Co) film. Both materials have large spin diffusion lengths and, therefore, are suitable for supporting spin-polarized currents. Spin-pumped ferromagnetic resonance imaging (SP-FMR) studies showed that a high rate of spin-to-charge conversion is detected in a device based on the Sb₂Te₃/Au/Co heterostructure, while no conversion is observed when considering the Sb₂Te₃/Al/Co heterostructure.

To understand this difference in functional behavior, we analyzed the electronic and chemical properties of the interface between the TI and the Au and Al layers by performing angle-resolved photoemission spectroscopy (ARPES) experiments and core-level analysis at the high-resolution VUV-Photoemission beamline of Elettra. Au and Al were thermally evaporated under ultrahigh vacuum conditions onto in-situ exfoliated Sb₂Te₃ single crystals.

Uncovering hidden light-matter interactions at the nanoscale

2025/06/032025/06/06

Progress in nanoscience increasingly depends on our ability to control light at spatial and temporal scales matching those characteristic of nanostructures. In particular, controlling the polarization of light is essential for investigating materials whose properties depend not only on how much light they absorb, but also on the specific orientation of the electric field. Such polarization-sensitive effects are central to the behavior of magnetic and chiral materials, which are of great interest across condensed matter physics, chemistry, and materials science.

At visible wavelengths, artificial structures with dimensions comparable or smaller than the wavelength of the light can be used to shape its intensity or polarization with nanoscale precision. However, in the extreme ultraviolet (EUV), where the wavelengths are much shorter, no comparable tools exist. To overcome this limitation, an international team led by researchers at the TIMER beamline of the FERMI free-electron laser (FEL) has developed a breakthrough method. By combining their unique instrument with a tailored configuration of the FEL, they created a novel type of transient grating in which it is not the intensity, but the polarization of the light that varies periodically. Imagine this as a series of stripes where the electric field rotates in opposite directions from one stripe to the next, with inter-stripe spacing as small as 43 nanometers. Unlike artificial structures, this grating is not static, but exists for the same time duration of the FEL pulses, enabling the ultrafast dynamics of the material illuminated by the light pulse to be probed.

The researchers then tested how a thin film of a magnetic alloy (CoGd) responds to this polarization-modulated grating, comparing it with the response induced by an intensity-modulated grating. In the case of intensity-modulated gratings, the signal was dominated by thermal effects, such as heat-induced vibrations (Fig. 1a). In contrast, the polarization grating suppressed this thermo-elastic background, revealing an otherwise hidden signal (Fig. 1b). Numerical simulations showed that this signal can be attributed to helicity-dependent magnetic effects, that is, to changes in the magnetization directly induced by the circular polarization of light. This suggests that polarization-modulated gratings can be used to selectively trigger and monitor non-thermal, ultra-fast magnetic dynamics that were previously inaccessible.

By enabling precise control of light polarization on nanometer length and femtosecond time scales, this new methodology opens exciting opportunities for studying a wide range of materials. These include systems with complex magnetic structures, topological phases, or valley-dependent properties — fields of growing interest in materials science. This approach adds a powerful new tool to the expanding field of ultrafast EUV and X-ray spectroscopy and paves the way for investigating fundamental processes in condensed matter physics with unprecedented precision.

Exploring how tiny particles affect our lungs

2025/05/212025/05/22

Very small particles — either naturally occurring in the air or engineered for industrial purposes — can penetrate deep into our lungs because they are smaller than 100 nanometers (about 1,000 times thinner than a human hair). These particles can cause serious long-term health problems, such as inflammation, and tissue damage, which can lead to fibrosis or even cancer.

To assess the health risks of these nanoparticles and predict how they might affect us, it is essential to understand exactly how they interact with lung cells at the molecular level — from the moment they come into contact with lung tissue. Such a detailed investigation requires sophisticated imaging techniques that can reveal both the structure and function of these tiny interactions. One powerful method is Correlated Light and Electron Microscopy (CLEM), which combines different types of microscopes to provide a more complete picture. Thanks to recent advances in resolution and sensitivity, CLEM has become an important tool in biological research.

In our study, we developed a new, expanded CLEM approach that combines several advanced imaging techniques to better understand how lung cells respond to a specific type of nanoparticle: titanium dioxide nanotubes (TiO₂ NTs), which are known to cause inflammation and are considered potentially carcinogenic. Our approach integrates a wide range of complementary tools, providing a morpho-functional assessment of the studied interface (Fig. 1):

Confocal Laser-Scanning Microscopy (CLSM), together with Fluorescence Lifetime Imaging Microscopy (FLIM) and Hyperspectral Fluorescence Imaging (fHSI) to study live cells at the organelle and nanoscopic scales.
Scanning Electron Microscopy (SEM) and Helium Ion Microscopy (HIM) for extremely detailed surface imaging.
Synchrotron-based X-ray Fluorescence (SR μXRF) combined with Scanning Trasnmission X-ray Microscopy (STXM) for analyzing the chemical elements in and around the cells at submicrometric length scales.

Among these, SR μXRF has crucial importance, as it provides chemical sensitivity. Together, these methods allowed us to study interactions across many scales — from whole cells down to individual molecules.

Scanning transmission X-ray Microscopy (STXM) combined with low energy micro-X-ray Fluorescence (LE-μXRF) were carried out at the TwinMic beamline of Elettra. These measurements were complemented by Correlative light,electron and ion microscopy, namely fluorescence lifetime imaging microscopy (FLIM), hyperspectral fluorescence imaging (fHSI), scanning electron microscopy (SEM) and ultra-high resolution helium ion microscopy (HIM).

A novel fullerene structure on a topological insulator surface

2025/02/062025/02/10

The so-called Buckminster fullerene (C₆₀) has a spherical shape and assembles into a cubic structure at all temperatures. At room temperature, the fullerenes can spin around their axes and hence, the molecules are randomly oriented. At lower temperature, this spinning motion is frozen and all the C₆₀ molecules are orientationally ordered in a certain direction. The transition to ordered structure with cooling is typically observed as first order structural transition from face-centered-cubic to simple cubic structure below 260 K. While thick layers of fullerenes on metal and semiconductor substrates have been studied previously, the C₆₀ structural transition in single layer and its impact on substrate surface electronic properties are still unexplored.

In this work, Pandeya et al. studied the growth of single layer long-range crystalline order of a single layer fullerene film on a novel substrate. Since the expected effect of C₆₀ on the substrate is rather small because of the van der Waals interaction, a topological insulator (TI), Bi₄Te₃, with spin-polarized electronic states located at the surface was chosen as substrate. The sample was grown at Forschungszentrum Jülich (Germany) by molecular beam epitaxy and capped with a protective layer so that it could be safely transported to Elettra synchrotron. The surface character of the topological insulator electronic states made it possible to study the interaction with adsorbed fullerenes.

To probe the electronic structure of both topological insulator surface and the C₆₀ thin film, high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements were carried out at the BaDElPh beamline of Elettra, taking advantage of high brightness, high energy resolution, photon energy tunability, and most importantly polarization tunability of the photon source. The study was conducted at two different temperatures: room temperature, at which the fullerenes are spinning, and 30 K, at which the spinning motion is frozen out. Careful analysis of the ARPES data (see Figure 1) enabled the research team to identify a significant electron transfer to the TI surface state from C₆₀ layer at room temperature without affecting substrate surface and thin film electronic properties. Interestingly, at low temperature where C₆₀ molecules are frozen, a negligible charge transfer to TI surface was observed, indicating that both the substrate and thin films preserve the pristine electronic properties.

Coherent control of strongly driven quantum dynamics using FERMI shaped pulses

2024/12/282025/01/07

The interaction of light with matter provides indispensable insight into the quantum mechanical world of atoms and molecules on their intrinsic time and length scale. Compared to the macroscopic world, these scales are extreme: about 10 fs for the motion of the nuclei, about 10 as for the motion of the electrons; 0.2 nm is the typical length of a chemical bond. A major objective in science is the control of the nanoscopic processes on their extreme scales, which remains a challenge. Based on the concepts of quantum mechanics, specially tailored light fields can be used to address this problem. Here, the electromagnetic wave-character of light is exploited. By shaping the amplitude, phase and polarization of the electromagnetic waves, fields can be sculpted that enhance certain quantum processes while suppressing others, resulting in a net control of the system. The prerequisite is the ability to shape the electromagnetic field of ultrashort laser pulses with durations of just a few femtoseconds. Such pulses enabled scientists for the first time to trigger and control the atomic and molecular processes on their natural time scale.

In the visible range of the spectrum the spectro-temporal shaping of ultrashort laser pulses is a mature technique. Potential applications can be found in physics, chemistry and material science, for instance in the control of chemical reactions, efficient qubit manipulation, the exploration of complex reaction pathways, and the emergence of new spectroscopy concepts. To date, corresponding concepts in the extreme ultraviolet (XUV) and X-ray regime are hardly explored. The short-wavelength domain provides a perspective to access shorter time and length scales. Extremely short laser pulses with attosecond duration are available in this range, and highly localized inner-shell electrons can be addressed at these photon energies. Thus, extending spectro-temporal pulse shaping to the short-wavelength regime promises the quantum control of matter on unprecedented short time scales and with chemical sensitivity.

Image: photoelectron spectrum showing the split-up of the energy level in helium and the control of the relative population by shaping the phase of the XUV pulses. Adapted from the original paper, licensed under a Creative Commons Attribution 4.0 International License

An innovative platform for NO₂ detection for cleaner air and safer cities

2024/11/272024/12/09

An international collaboration involving scientists from Italy, China, Czech Republic, Romania, Taiwan has highlighted how indium sulfide (InS), with its moderate band gap and layered structure, holds great promise for NO₂ gas sensing.

Nitrogen dioxide, a harmful gas linked to respiratory and cardiovascular issues, is particularly challenging to detect due to the need for sensors that combine high sensitivity, precise selectivity, and stability under diverse conditions. Traditional materials, such as metal-oxide semiconductors, are widely used but often lack the required sensitivity and selectivity, especially for NO₂ detection. In contrast, InS meets these requirements, also showing an evolution of its surface under oxidative conditions (e.g., in the air), implying chemical transformations that improve sensing performance. The sub-stoichiometric metal oxide formed upon oxidation results to be ideal for gas adsorption, with the ultimate obtainment of an ultrasensitive NO₂ detection. Moreover, when exfoliated into nanosheets, 2D InS gets an intrinsically higher amount of active sites that enhances interaction with gases, making it particularly suitable for selective detection of NO₂ in real-time air quality monitoring applications, as demonstrated by gas-sensing tests carried out with an operation temperature of 350°C.

To investigate chemical transformations in InS under oxidative conditions, Scanning Photoemission Microscopy (SPEM) at the ESCA Microscopy beamline of Elettra allowed real-time observation of the material as it actively interacted with NO₂. Under these operando conditions, the surface of InS develops an oxygen-deficient In₂O₃-x layer, with nanometric thickness detected by transmission electron microscopy, through a sulfur abstraction process. This reaction, which removes sulfur atoms from the structure, creates highly active sites on the InS surface. The high spatial resolution of SPEM enabled direct observation of these nanoscale chemical changes on the surface of InS nanosheets, providing real-time visualizations of active sites as they formed.

Scientific discoveries: Acynodon between Technology and Palaeontology

2024/09/232024/10/17

A major study conducted at the paleontological site of Villaggio del Pescatore, in Friuli-Venezia Giulia, has revealed new information on the appearance of the Italian territory at the time of the dinosaurs. This project, a collaboration between the Municipality of Trieste and Zoic s.r.l., led to the extraction and preparation of numerous fossil finds, including those of the rare crocodile Acynodon, a semi-aquatic reptile that lived during the Cretaceous period.
Cooperation with Elettra revealed previously unseen details of Acynodon’s skull that were impossible to obtain before without damaging the fossil. Although similar to a small crocodile, its teeth are surprising: the front teeth are adapted to grasp small prey, while the massive, rounded rear teeth shred shells. This unique adaptation suggests that the Cretaceous crocodiles at the Fisherman’s Village were very different in size, shape and diet to those of today. The results of the research were published in the scientific journal The Anatomical Record (Muscioni et al., 2024).

Fundamental spatial limits of all-optical magnetization switching

2024/07/292024/08/06

Modern magnetic hard drives can store more than one terabit of data per square inch, which means that the smallest unit of information can be encoded on an area smaller than 25 nanometers by 25 nanometers. Therefore, to realize the full potential of laser-based all-optical switching (AOS), particularly in terms of faster write/erase cycles and improved power efficiency, we need to understand whether a nanoscale magnetic bit can still be all-optically reversed.

For AOS to occur, the magnetic material has to be heated up to high temperatures in order to reduce its magnetization close to zero. Only then can its magnetization reverse. The twist in AOS is that it is sufficient to heat the electrons of the material while leaving the lattice of atoms cold. This is exactly what an optical laser pulse does: it primarily interacts with the electrons, allowing much higher electron temperatures to be reached with very low power levels. However, since hot electrons cool down very rapidly by scattering with the cold atoms, the magnetization must be reduced within the characteristic time scale of such a cooling process, i.e., AOS relies on a careful balance between the evolution of the (electron) temperature and the loss of magnetization. It is easy to see that this balance is altered when the excitation is confined to the nanoscale: electrons cannot only lose energy by interacting with cold atoms but also by diffusing out of the nanometer-small hot regions. At the nanoscale, all these processes occur on comparable and ultrafast time scales: for instance, the electrons may cool down too quickly, the magnetization is not sufficiently decreased, and AOS breaks down.

An international team of researchers from the Max Born Institute in Berlin, Germany, the Instituto de Ciencia de Materiales in Madrid, Spain, and the free-electron laser facility FERMI in Trieste, Italy, has successfully addressed for the first time the question: how small can AOS work?

High-pressure synthesis of carbonic acid polymorphs from carbon dioxide clathrate hydrate

2024/07/142024/07/19

Carbon dioxide (CO₂) is largely present in diverse astrochemically relevant environments, quite often co-existing with water (H₂O) ices. Their simultaneous presence has triggered a great interest regarding the stabilization of CO₂ clathrate hydrates and the possible formation of adducts under various thermodynamic conditions. Amongst these adducts, solid carbonic acid (H₂CO₃) remains elusive. All the synthetic routes followed up to now for its production required quite drastic conditions (from high energy protonation of solid CO₂ to laser heating at high pressure on fluid mixtures of CO₂ and H₂O).

In our study, we discovered a highly reproducible, simpler and effective way to synthesize two diverse carbonic acid crystal structures upon the fast, cold compression of pristine CO₂ clathrate hydrates. We found that the products of this reaction strictly depend on the starting pressures, resulting in three different reaction pathways. In the first pathway, for pressures lower than 2.7 GPa, pristine CO₂ clathrate hydrate simply decomposes into its constituents, as expected from previous studies. For intermediate pressures (between 2.7 and 4.8 GPa), a first crystalline phase is observed, characterized by a well-defined lattice phonon region (see Figure 1a, green spectrum) and a specific diffraction pattern. For pressures exceeding 4.8 GPa, the formation of an amorphous product is observed, characterized by a broad, unstructured band in the lattice phonon region (see Figure 1a, black spectrum). Both the two products feature an intense, quite broad Raman band at about 1050 cm^-1, a reported signature band for carbonate-based systems and, also, carbonic acid (see Figure 1b). We found that the high pressure, amorphous product (called a-ε) transformed upon decompression down to 4.8 GPa or heating at higher pressures into a distinct, much more structured crystalline phase characterized by 10 lattice phonons (see Figure 1a, red spectrum) and sharper internal Raman bands (Figure 1b, red spectrum). This structure was found to be that already reported by Abramson and co-authors in a recent paper, where it was obtained in much more drastic conditions (from fluid CO₂ and H₂O upon resistive heating): we called this phase ε-H₂CO₃.

Enhancing FEL imaging resolution with OAM and ptychography

2024/06/262024/07/22

The broad research fields of microscopy and computational imaging actively seek higher resolution, better quality, faster acquisition, versatile and easy-to-operate instrumentation to accommodate as many scientific applications as possible. Ptychography is one of the computational microscopy techniques based on diffraction imaging principles, where algorithms are used to reconstruct a high-fidelity image of the sample without the use of magnifying lenses. While powerful, ptychography’s effectiveness can, however, be limited by the characteristics of the probing light, particularly in the case of samples exhibiting a high degree of symmetry.

In this study, researchers at the DiProi beamline explored the use of Extreme Ultraviolet light carrying Orbital Angular Momentum (OAM), often referred to as “twisted light” to enhance ptychographic imaging resolution. Unlike conventional (Gaussian) beams, OAM light has a helical phase structure, which combined with the structured illumination of the beam profile, allows for a selective amplification of high-frequency spatial component in the diffraction process. The net effect is an increase in the amount of information (spatial resolution) that can be captured about the sample.

The experiments were conducted using the FERMI seeded free-electron laser (FEL) source, which provides a highly coherent and intense beam of light. By pairing state-of-the-art ptychography reconstruction algorithms designed by the Scientific Computing Team with the high-quality characteristics of the source, the researchers were able to reliably use the OAM beam to improve the spatial resolution of the reconstructed images.

A closer look at the toxicity mechanisms of erionite, a major natural carcinogen

2024/06/102024/06/13

Erionite is a naturally occurring zeolite, a crystalline material characterized by a framework of silicon/aluminium-centred tetrahedra, joined together by means of the oxygen atoms at the vertices. The open framework contains channels and cavities (micropores) that accommodate varying amounts of exchangeable H₂O molecules and extra-framework cations, such as sodium, calcium, magnesium, potassium.

Erionite is found in nature in the form of bundles of very thin fibres (Figure 1), the appearance of which resembles a wad of wool (“erion” in Greek means wool) and, much more rarely, as individual needle-like fibres. Erionite has caused exceptional cancer (malignant mesothelioma) morbidity in some areas of Cappadocia (Turkey) and is now classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen. In fact, erionite’s high biopersistence—its ability to remain in the body without breaking down—combined with its unique ion-exchange properties, makes it one of the major natural hazards.A collaboration between Elettra, the Universities of Modena and Reggio Emilia, Genova and Parma, and the Italian National Research Council has made significant strides in understanding the toxicity mechanisms of erionite. In a groundbreaking study, the team employed cutting-edge synchrotron-based micro-X-ray fluorescence (micro-XRF) and micro-X-ray absorption spectroscopy to investigate how erionite-Na interacts with human macrophages, the immune cells responsible for engulfing and digesting foreign particles.

The study revealed that when macrophages engulf erionite fibres, there is a significant disruption in the balance of intracellular calcium and sodium ions. This disruption is crucial as it triggers harmful cellular responses, potentially leading to cancer-promoting adverse effects.Surprisingly, the anticipated major role of erionite’s ion-exchange capacity in toxicity was found to be less significant than previously thought. Instead, the internalization of iron-rich particles associated with erionite fibres and the subsequent cellular stress play a more critical role. These findings help clarify why erionite is much more potent in causing malignant mesothelioma than other mineral fibres like asbestos. The study employed soft X-ray microscopy combined with low energy sub-micro-XRF mapping at the TwinMic beamline of Elettra Sincrotrone Trieste complemented by measurements taken at the ID21 beamline of ESRF Synchrotron in Grenoble, France.

Image: High resolution TEM image of an erionite bundle

Credit: E. Mugnaioli

Ultrafast dynamics in a molecular photoswitch

2024/04/042024/04/11

Molecules that undergo photoinduced isomerization reactions and are capable of storing the absorbed light as chemical energy, releasing it as thermal energy on demand, are referred to as molecular solar thermal energy storage (MOST) or solar thermal fuels (STF). An ideal model system for such technologically important applications is the photoswitchable pair of isomers quadricyclane (QC, a highly strained multicyclic hydrocarbon), and its lower-energy isomer norbornadiene (NBD). The isomers, shown in Figure 1, interconvert upon photoabsorption in the deep ultraviolet (UV) range. An experiment performed at FERMI sheds new light on the mechanism of the reverse interconversion, QC → NBD, which is of both fundamental photochemical interest and practical importance since it represents the undesired UV-induced photoreversion process in MOST systems based on the QC/NBD pair.

Using time-resolved photoelectron spectroscopy (TRPES) with extreme ultraviolet (XUV) probe pulses at the Low Density Matter end-station of the seeded FEL FERMI, along with non-adiabatic molecular dynamics simulations, an international collaboration led by Prof. Daniel Rolles and Dr. Kurtis D. Borne from Kansas State University, Prof. Adam Kirrander from the University of Oxford, and Prof. Caterina Vozzi from Politecnico di Milano succeeded in tracking the two competing pathways by which electronically excited quadricyclane molecules relax to the electronic ground state.

Image: Schematic of the QC ⇄ NBD interconversion.

Zn-air batteries: how working conditions impact cathode stability

2024/02/132024/04/11

Electrically rechargeable alkaline zinc-air batteries (RZAB) hold immense promise for future energy storage, offering a sustainable and cost-effective solution for both stationary and mobile applications. Zinc-air batteries operate on the coupled electrochemistry of zinc and oxygen. Reversible oxygen redox is enabled by a bifunctional gas-diffusion-electrode (GDE), that drives oxygen reduction during discharge and oxygen evolution during recharge. With present-day technologies, the alternation of these processes leads to the accumulation of damage, causing durability issues that still hamper implementation in real-life devices.

The aim of the present research is to fabricate a durable, efficient and sustainable bifunctional GDE. To achieve this objective, an insightful understanding of the electrode, jointly addressing molecular-level out-of-equilibrium electrochemistry and mesoscale architecture geometry evolution is required. The novel bifunctional GDE features a-MnO₂ nanowires as oxygen reduction electrocatalyst and Ni@NiO core-shell nanoparticles as oxygen evolution electrocatalyst. The fabrication process consists in microwave-assisted hydrothermal synthesis of α-MnO₂ nanowires, formulation of an ink with different contents of Ni/NiO nanoparticles, and spray-coating onto carbon paper, followed by thermal treatment.

Electrochemical performance is assessed using voltammetry, galvanostatic sequences representative of realistic operating conditions, and electrochemical impedance spectroscopy (EIS) in half-cell configuration. The novel GDEs exhibit remarkable oxygen reduction current densities, in excess of 200 mA cm^-2, with improved stability during successive charge-discharge cycles. The addition of Ni@NiO nanoparticles lowers anodic overvoltages, mitigating carbon-support corrosion and enhancing overall GDE stability. However, the presence of Zn²⁺, released to the electrolyte by the anodic process, accelerates GDE failure due to the formation of inactive Zn-Mn-containing phases: this degradation mode is however mitigated by the Ni-based electrocatalyst, showing an anodic contribution also to poisoning.

Electrochemical measurements, combined with morphological SEM and TEM observations and STXM spectromicroscopy, performed at Elettra’s TwinMic beamline, allowed to pinpoint the degradation mechanisms, providing concrete guidance to overcome them. Specifically, electrochemical ageing, on the one hand, targets catalyst stability, triggering cathodic dissolution of Mn and anodic redeposition of MnO₂ in less active forms, and, on the other hand, high anodic overvoltages, due to insufficient Ni-contaning electrocatalyst, favour oxygen bubble formation in the bulk of the active layer architecture, leading to cracking. Chemical degradation of the electrocatalysts causes nanorod agglomeration, growth of amorphous phases and Ostwald ripening of the Ni nanoparticles. Figures 1a and 2a display, respectively, ADHUC Mn L-edge spectra of a selection of samples tested in this study, accompanied by a typical chemical-state map, representative electrochemical results and TEM images. The alteration in the valence state of Mn and its space distribution can be readily inferred from stacks of absorption maps.

Single-spin flat bands in monolayer graphene

2024/02/072024/02/07

In the rapidly evolving landscape of electronic materials and devices, the integration of two-dimensional materials, graphene in particular, with magnetic elements has emerged as a promising frontier. The ability to engineer spin-dependent electronic properties not only expands the horizons of spintronics but also holds the potential to revolutionize a wide array of electronic applications. From ultra-fast data processing to energy-efficient memory storage and beyond, the synergistic interplay between graphene and magnetic layers opens new routes for device miniaturization, aiming at reduced power consumption and enhanced performance.

Along these lines, the realization of topological electronic flattened bands near or at the Fermi level represents a promising avenue for the emergence of exotic electronic and magnetic states. One of the key attributes of flat bands is their facile electrical tunability, allowing for the exploration of correlated phases such as unconventional superconductivity, quantum states, and insulating topological states, all within two-dimensional platforms and without the need for an applied magnetic field.

An alternative approach to generate flat bands in graphene involves exploiting the Spin-Orbit Coupling (SOC) effect induced by the proximity to magnetic and/or heavy-metal layers. Monolayer graphene (Gr) interfaced with 3d-ferromagnetic and 4f-materials presents compelling technological prospects, bridging the realms of spintronics, ultra-fast graphene-based electronics, and photonics. While Gr/3d-ferromagnetic systems exhibit strong hybridization, impacting the electronic properties of graphene, Gr/4f-ferromagnetic interfaces demonstrate a weak interaction that preserves graphene’s electronic structure.

Image: Landscape of the structural and electronic properties upon Eu intercalation in Gr/Co(0001). LEED patterns acquired at a kinetic energy of 69 eV (a, d), 2D momentum maps at the Fermi level (b, e) and ARPES energy vs. momentum maps (c, f) acquired at the K point of the first Brillouin zone for Gr/Co and Gr/Eu/Co, respectively.