Beam-induced Effects Research Articles

Proton beam-induced radiosensitizing effect of Ce0.8Gd0.2O2-x nanoparticles against melanoma cells in vitro

Proton beam-induced radiosensitizing effect of Ce0.8Gd0.2O2-x nanoparticles against melanoma cells in vitro

The AUREX cell: a versatile operando electrochemical cell for studying catalytic materials using X-ray diffraction, total scattering and X-ray absorption spectroscopy under working conditions.

Understanding the structure-property relationship in electrocatalysts under working conditions is crucial for the rational design of novel and improved catalytic materials. This paper presents the Aarhus University reactor for electrochemical studies using X-rays (AUREX) operando electrocatalytic flow cell, designed as an easy-to-use versatile setup with a minimal background contribution and a uniform flow field to limit concentration polarization and handle gas formation. The cell has been employed to measure operando total scattering, diffraction and absorption spectroscopy as well as simultaneous combinations thereof on a commercial silver electrocatalyst for proof of concept. This combination of operando techniques allows for monitoring of the short-, medium- and long-range structure under working conditions, including an applied potential, liquid electrolyte and local reaction environment. The structural transformations of the Ag electrocatalyst are monitored with non-negative matrix factorization, linear combination analysis, the Pearson correlation coefficient matrix, and refinements in both real and reciprocal space. Upon application of an oxidative potential in an Ar-saturated aqueous 0.1 M KHCO3/K2CO3 electrolyte, the face-centered cubic (f.c.c.) Ag gradually transforms first to a trigonal Ag2CO3 phase, followed by the formation of a monoclinic Ag2CO3 phase. A reducing potential immediately reverts the structure to the Ag (f.c.c.) phase. Following the electrochemical-reaction-induced phase transitions is of fundamental interest and necessary for understanding and improving the stability of electrocatalysts, and the operando cell proves a versatile setup for probing this. In addition, it is demonstrated that, when studying electrochemical reactions, a high energy or short exposure time is needed to circumvent beam-induced effects.

Beam Effects in Synchrotron Radiation Based Operando Characterization of Battery Materials: XRD and XAS Study of LiNi0.33Mn0.33Co0.33O2 and LiFePO4 Electrodes

Operando synchrotron radiation-based characterization techniques applied to energy storage materials are becoming a widespread characterization tool as they allow for non-destructive probing of materials with various depth sensitivities through spectroscopy, scattering, and imaging techniques. Moreover, they allow for faster acquisition rates, variable penetration depths, higher spectral or spatial resolution, or access to techniques that are only possible with a continuous tuneable source over a wide photon energy range. Compatibility between the electrochemical cell designs and the experimental setups may force some specific design features and care must be taken to ensure that these do not perturb the electrochemical response of the materials under investigation. The use of operando techniques has intrinsic advantages, as they enable the detection of metastable intermediates, if any, and ensure characterization under real conditions avoiding the risk of ex situ sample evolution during its preparation. However, they do not come with the extent of risks. The interaction between synchrotron radiation and samples, particularly within the intricate milieu of an operational electrochemical cell, can induce unexpected effects in the sample at the measurement spot, thereby jeopardizing the experiment's reliability and biasing data interpretation. While beam-induced effects are well-recognized for their critical impact on characterizing biological samples, macromolecules, or soft matter, they have, until recently, received scant attention within the battery research community, being vaguely referenced and incompletely understood. With the aim of contributing to this ongoing debate, a systematic investigation into these phenomena was carried out conducting a root cause analysis of beam-induced effects during the operando characterization of two commercially employed positive electrode materials: LiNi0.33Mn0.33Co0.33O2 and LiFePO4. The study spans across diverse experimental conditions involving various cell types, absorption and scattering techniques and seeks to correlate beam effects with factors such as radiation energy, photon flux, exposure time, and other parameters associated with radiation dosage. As a conclusion, a set of guidelines and recommendations are provided to evaluate and mitigate beam-induced effects that can affect the outcome of battery operando experiments.

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS

Electron Beam-Induced Effects on a Ni-Rich Layered Cathode Material: A Comprehensive Investigation Using STEM and EELS

Beam Effects in Synchrotron Radiation Operando Characterization of Battery Materials: X-Ray Diffraction and Absorption Study of LiNi0.33Mn0.33Co0.33O2 and LiFePO4 Electrodes.

Operando synchrotron radiation-based techniques are a precious tool in battery research, as they enable the detection of metastable intermediates and ensure characterization under realistic cycling conditions. However, they do not come exempt of risks. The interaction between synchrotron radiation and samples, particularly within an active electrochemical cell, can induce relevant effects at the irradiated spot, potentially jeopardizing the experiment's reliability and biasing data interpretation. With the aim of contributing to this ongoing debate, a systematic investigation into these phenomena was carried out by conducting a root cause analysis of beam-induced effects during the operando characterization of two of the most commonly employed positive electrode materials in commercial Li-ion batteries: LiNi0.33Mn0.33Co0.33O2 and LiFePO4. The study spans across diverse experimental conditions involving different cell types and absorption and scattering techniques and seeks to correlate beam effects with factors such as radiation energy, photon flux, exposure time, and other parameters associated with radiation dosage. Finally, it provides a comprehensive set of guidelines and recommendations for assessing and mitigating beam-induced effects that may affect the outcome of battery operando experiments.

Understanding charge transfer dynamics in blended positive electrodes for Li-ion batteries

This paper investigates the electrochemical behavior of binary blend electrodes comprising equivalent amounts of lithium-ion battery active materials, namely LiNi0.5Mn0.3Co0.2O2 (NMC), LiMn2O4 (LMO), LiFe0.35Mn0.65PO4 (LFMP) and LiFePO4 (LFP)), with a focus on decoupled electrochemical testing and operando X-ray diffraction (XRD). All possible 50:50 blend combinations were studied and the distribution of current between blend components was followed during continuous and pulsed charge and discharge processes. The results demonstrate the significant impact of the voltage profiles of individual materials on the current distribution, with the effective C-rate of each component varying throughout the State of Charge (SoC). Pulsed decoupled electrochemical testing reveals the exchange of charge between blend components during relaxation, showcasing the "buffer effect", which has also been captured through time-resolved operando XRD experiments in real blends carefully considering beam-induced effects. The directionality and magnitude of the charge transfer were found to depend on the nature of the components and the cell SoC, being also influenced by temperature. These dependencies can be rationalized considering both thermodynamics (voltage profile) and reaction kinetics of the blend constituents. These findings contribute to advancing the understanding of internal dynamics in blended electrodes, offering valuable insights for the rational design of blends to meet the diverse operational demands of lithium-ion batteries.

Graphene sandwich–based biological specimen preparation for cryo-EM analysis

High-quality specimen preparation plays a crucial role in cryo-electron microscopy (cryo-EM) structural analysis. In this study, we have developed a reliable and convenient technique called the graphene sandwich method for preparing cryo-EM specimens. This method involves using two layers of graphene films that enclose macromolecules on both sides, allowing for an appropriate ice thickness for cryo-EM analysis. The graphene sandwich helps to mitigate beam-induced charging effect and reduce particle motion compared to specimens prepared using the traditional method with graphene support on only one side, therefore improving the cryo-EM data quality. These advancements may open new opportunities to expand the use of graphene in the field of biological electron microscopy.

Electron beam-induced brownmillerite–perovskite phase transition in La0.6Sr0.4CoO3− δ

The electron beam, during high-resolution transmission electron microscopy, was employed to induce a phase transition in La0.6Sr0.4CoO2.5 (LSC) from a brownmillerite ordering to an oxygen deficient perovskite structure. Prior to irradiation, a strongly alternating out-of-plane lattice parameter was observed, reflecting electrostatic interactions between AO and BO/BO2 planes in the brownmillerite ordering. During electron beam irradiation for one hour, the oxygen vacancy ordering vanished gradually, and a uniform cubic perovskite structure prevailed. To exclude beam-induced heating effects, in situ heating experiments were performed, revealing a stable brownmillerite ordering in the relevant temperature range (up to at least 500 °C). Thus, we conclude that the phase transition is caused by knock-on processes that affect oxygen vacancies in terms of a transition from structural vacancies toward extremely high concentrations of randomly distributed point defects in the ABO3 structure.

Development of a jet gas target system for the Felsenkeller underground accelerator

For direct cross section measurements in nuclear astrophysics, in addition to suitable ion beams and detectors, also highly pure and stable targets are needed. Here, using a gas jet as a target offers an attractive approach that combines high stability even under significant beam load with excellent purity and high localisation. Such a target is currently under construction at the Felsenkeller underground ion accelerator lab for nuclear astrophysics in Dresden, Germany. The target thickness will be measured by optical interferometry, allowing an in-situ thickness determination including also beam-induced effects. The contribution reports on the status of this new system and outlines possible applications in nuclear astrophysics.

Thermal effects of beam profiles on X-ray photon correlation spectroscopy at megahertz X-ray free-electron lasers.

X-ray free-electron lasers (XFELs) with megahertz repetition rates enable X-ray photon correlation spectroscopy (XPCS) studies of fast dynamics on microsecond and sub-microsecond time scales. Beam-induced sample heating is one of the central concerns in these studies, as the interval time is often insufficient for heat dissipation. Despite the great efforts devoted to this issue, few have evaluated the thermal effects of X-ray beam profiles. This work compares the effective dynamics of three common beam profiles using numerical methods. Results show that under the same fluence, the effective temperatures increase with the nonuniformity of the beam, such that the Gaussian beam profile yields a higher effective temperature than the donut-like and uniform profiles. Moreover, decreasing the beam sizes is found to reduce beam-induced thermal effects, in particular the effects of beam profiles.

X-Ray Induced Chemical Reaction Revealed by In Situ X-Ray Diffraction and Scanning X-Ray Microscopy in 15 nm Resolution

Abstract The detection sensitivity of synchrotron-based X-ray techniques has been largely improved due to the ever-increasing source brightness, which has significantly advanced ex situ and in situ research for energy materials such as lithium-ion batteries. However, the strong beam–material interaction arising from the high beam flux can substantially modify the material structure. The beam-induced parasitic effect inevitably interferes with the intrinsic material property, making the interpretation of the experimental results difficult and requiring comprehensive assessments. Here, we present a quantitative study of the beam effect on an electrode material Ag2VO2PO4 using four different X-ray characterization methods with different radiation dose rates. The material system exhibits interesting and reversible radiation-induced thermal and chemical reactions, further evaluated under electron microscopy to illustrate the underlying mechanism. The work will provide a guideline for using synchrotron X-rays to distinguish the intrinsic behavior from extrinsic structure change of materials induced by X-rays.

Beam-Induced Effects on Platinum Oxidation during Ambient-Pressure X-ray Photoelectron Spectroscopy.

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) is commonly used to identify active phases of Pt-based catalysts. Unavoidable beam-induced chemistry under in situ conditions with high-flux X-rays is important yet has often been disregarded. To evaluate beam effects on Pt oxidation, we revisited surface species on Pt(111) and Pt(110) in O2 environments using APXPS. The observed X-ray-induced phenomena strongly depended on pressure and surface orientation. Below 1 mbar of O2, we found only chemisorbed oxygen species on both surfaces. No significant change in Pt(111) was observed with long-time illumination under ≤2 mbar of O2. Under ∼5 mbar with similar oxygen exposure, beam-induced oxidation was apparent on Pt(111) with the formation of abundant surface oxide and chemisorbed oxygen. However, such beam-induced oxidation was strongly suppressed on Pt(110). Understanding these "pressure gap" and surface orientation-dependent beam-induced phenomena is essential for our interpretation of the in situ X-ray results, particularly for higher-pressure experiments with brighter synchrotron sources.

Beam and sample movement compensation for robust spectro-microscopy measurements on a hard X-ray nanoprobe.

Static and in situ nanoscale spectro-microscopy is now routinely performed on the Hard X-ray Nanoprobe beamline at Diamond and the solutions implemented to provide robust energy scanning and experimental operation are described. A software-based scheme for active feedback stabilization of X-ray beam position and monochromatic beam flux across the operating energy range of the beamline is reported, consisting of two linked feedback loops using extremum seeking and position control. Multimodal registration methods have been implemented for active compensation of drift during an experiment to compensate for sample movement during in situ experiments or from beam-induced effects.

Factors influencing surface carbon contamination in ambient-pressure x-ray photoelectron spectroscopy experiments

Carbon contamination is a notorious issue that has an enormous influence on surface science experiments, especially in near-atmospheric conditions. While it is often mentioned in publications when affecting an experiment’s results, it is more rarely analyzed in detail. We performed ambient-pressure x-ray photoelectron spectroscopy experiments toward examining the build-up of adventitious carbon species (both inorganic and hydrocarbons) on a clean and well-prepared surface using large-scale (50 × 10 mm2) rutile TiO2(110) single crystals exposed to water vapor and liquid water. Our results highlight how various factors and environmental conditions, such as beam illumination, residual gas pressure and composition, and interaction with liquid water, could play roles in the build-up of carbon on the surface. It became evident that beam-induced effects locally increase the amount of carbon in the irradiated area. Starting conditions that are independent of light irradiation determine the initial overall contamination level. Surprisingly, the rate of beam-induced carbon build-up does not vary significantly for different starting experimental conditions. The introduction of molecular oxygen in the order of 10 mbar allows for fast surface cleaning during x-ray illumination. The surface carbon contamination can be completely removed when the oxygen partial pressure is comparable to the partial pressure of water vapor in the millibar pressure range, as was tested by exposing the TiO2(110) surface to 15 mbar of water vapor and 15 mbar of molecular O2 simultaneously. Furthermore, our data support the hypothesis that the progressive removal of carbon species from the chamber walls by competitive adsorption of water molecules takes place following repeated exposure to water vapor. We believe that our findings will be useful for future studies of liquid-solid interfaces using tender x rays, where carbon contamination plays a significant role.

Probing the beam‐induced heating effect inside a transmission electron microscope by nanoparticle labels

Beam-induced heating effect on nanoscale samples is a crucial question, as it strongly influences the interpretation of observed unusual behaviours. This question is currently under debate without a convincing conclusion. Here, using silver nitride (Ag3N) nanoparticles as temperature labels, we perform an investigation on this heating effect inside a transmission electron microscope (TEM) under normal imaging conditions. Combined with experimental measurements and semi-quantitative calculations, a temperature increase of more than 100 K is estimated and confirmed in the graphite carbon nitride (g-C3N4) films. Strong temperature gradients are found to exist in the single-end fixed g-C3N4 films. The influencing factors of heat accumulation are also investigated and discussed. Findings in this study may shed some light on the understanding of the abnormal behaviours of nano-objects observed inside TEM.

Whither Mn Oxidation in Mn-Rich Alkali-Excess Cathodes?

Author(s): Zuba, MJ; Grenier, A; Lebens-Higgins, Z; Fajardo, GJP; Li, Y; Ha, Y; Zhou, H; Whittingham, MS; Yang, W; Meng, YS; Chapman, KW; Piper, LFJ | Abstract: Lithium-rich NMC (LR-NMC) compounds exhibit high capacities beyond the traditional redox, but it remains unclear whether the anomalous charge compensation mechanism is due to oxidized lattice oxygen or migration-assisted Mn oxidation. We compare LR-NMC with a model Mn7+ system (KMnO4) using a combination of resonant inelastic X-ray scattering (RIXS) irradiation studies and operando X-ray absorption spectroscopy/X-ray diffraction (XAS/XRD) to quantify transition metal (TM) migration, Mn oxidization, and beam-induced effects. We reveal how for KMnO4 it is possible to observe beam-induced Mn reduction resulting in trapped molecular oxygen. For LR-NMC, we observe negligible evidence for Mn oxidation while stabilized tetrahedral sites correlate more with a reduced TM environment. Finally, the additional spectroscopic structures observed in oxidized oxygen RIXS for LR-NMC are absent for gas-phase molecular oxygen.

Beam-induced space-charge effects in time projection chambers in low-energy nuclear physics experiments

Tracking capabilities in Time Projection Chambers (TPCs) are strongly dictated by the homogeneity of the drift field. Ion back-flow in various gas detectors, mainly induced by the secondary ionization processes during amplification, has long been known as a source of drift field distortion. Here, we report on beam-induced space-charge effects from the primary ionization process in the drift region in low-energy nuclear physics experiment with Active Target Time Projection Chamber (AT-TPC). A qualitative explanation of the observed effects is provided using detailed electron transport simulations. As ion mobility is a crucial factor in the space-charge effects, the need for a careful optimization of gas properties is highlighted. The impact of track distortion on tracking algorithm performance is also discussed.

Electron Beam-Induced Effects on Bi6S2O15 Nanowires: An Insight into Stability and Applications

Electron Beam-Induced Effects on Bi₆S₂O₁₅ Nanowires: An Insight into Stability and Applications

Ion-beam-induced bending of semiconductor nanowires

The miniaturisation of technology increasingly requires the development of both new structures as well as novel techniques for their manufacture and modification. Semiconductor nanowires (NWs) are a prime example of this and as such have been the subject of intense scientific research for applications ranging from microelectronics to nano-electromechanical devices. Ion irradiation has long been a key processing step for semiconductors and the natural extension of this technique to the modification of semiconductor NWs has led to the discovery of ion beam-induced deformation effects. In this work, transmission electron microscopy with in situ ion bombardment has been used to directly observe the evolution of individual silicon and germanium NWs under irradiation. Silicon NWs were irradiated with either 6 keV neon ions or xenon ions at 5, 7 or 9.5 keV with a flux of 3 × 1013 ions cm−2 s−1. Germanium NWs were irradiated with 30 or 70 keV xenon ions with a flux of 1013 ions cm−2 s−1. These new results are combined with those reported in the literature in a systematic analysis using a custom implementation of the transport of ions in matter Monte Carlo computer code to facilitate a direct comparison with experimental results taking into account the wide range of experimental conditions. Across the various studies this has revealed underlying trends and forms the basis of a critical review of the various mechanisms which have been proposed to explain the deformation of semiconductor NWs under ion irradiation.

Effect of sputtering yield changes on the depth resolution in cluster beam depth-profiling of polymers

The authors present the results of the simulation, by means of a recently introduced transport and reaction model, of the sputter depth profiling of delta layers in a polymer system that undergoes mild modification during the measurement, such as in the case of X-ray photoelectron spectroscopy profiling with large cluster ion beams. They find that, even in the absence of roughening and at constant beam-induced mixing effects, the variations of sputtering yield caused by sample damage produce non-negligible changes in depth resolution.