Ion Microscopy Research Articles

Flipping electric dipole in the vibrational wave packet dynamics of carbon monoxide

Recently, Rydberg atom-ion-bound states have been observed using a high-resolution ion microscope [Nature 605, 453 (2022)] and the corresponding vibrational dynamics has been spectroscopically analyzed. The atom-ion bond is created by an avoided crossing, which involves a flipping molecular dipole. Motivated by the discovery of the flipping dipole moment in this highly excited Rydberg system covering large spatial scales and long time scales, we address here the question of whether a flipping dipole could also occur in ground-state diatomic molecules on much smaller scales. Specifically, we investigate the vibrational wave packet dynamics within the 1 Σ g + electronic ground-state of carbon monoxide (CO). The latter shows a zero crossing of its dipole moment function close to its equilibrium. Via the time-evolution of a vibrational wave packet approximating a coherent state, we demonstrate that indeed a flipping, i.e. oscillating, dipole with a non-zero time-averaged value is obtained and its dynamics can be controlled to some extent. Varying the coherent state parameter we explore different regions of the vibrational excitation spectrum thereby tuning the time scales of the rapid oscillatory motion of the relevant observables, their decay and revivals as well as the transition to a regime of irregular dynamics.

The Dynamic Atom-Probe: Past, Present, and Perspectives.

The present communication aims at demonstrating the wealth of information accessible by 1D-atom probe experiments using pulsed field desorption mass spectrometry (PFDMS), ultimately combined with video-field ion microscopy, while subjecting metallic samples to elevated gas pressures and studying surface reaction kinetics. Two case studies are being presented here: (a) the microkinetics of nickel tetracarbonyl (Ni(CO)4) formation through reaction of carbon monoxide with nickel and (b) the nitric oxide decomposition and reaction with hydrogen on platinum at variable steady electric fields mimicking electrocatalytic conditions. In both cases, surface areas with 140-150 atomic sites of the stepped Ni (001) and Pt (111) sample surfaces were probed. Under (a), we demonstrate variable repetition frequencies of field pulses to inform kinetic and mechanistic details of the surface reaction while under (b), we reveal the occurrence of field-induced processes impacting the surface reaction mechanism of nitric oxide with hydrogen and therefore opening new pathways not available under purely thermal conditions (in the absence of electric fields). Some aspects of PFDMS technical achievements will be discussed as they may provide clues for designing dynamic atom probe tomography instrumentation.

Flat dispersion at large momentum transfer at the onset of exciton polariton formation

Excitons are quasiparticles, comprised of an electron excited from the valence band and attracted to the hole left behind, that govern transport properties in transition metal dichalcogenides. Excitonic coherence specifically needs to be understood to realise applications based on Bose-Einstein condensation and superfluidity. Here we used momentum-resolved electron energy-loss spectroscopy to obtain the complete energy-momentum dispersion of excitons in thin film and monolayer WSe2 across the entire Brillouin zone, including outside of the light cone and for a large energy-loss range (1.5–4 eV). The measured dispersion of the modes was found to be flat. This suggests that the excitations are at the onset of polaritonic mode formation, propagating in the confinement of nanometer thin and monolayer WSe2. In combination with helium ion microscopy nanopatterning it was possible to probe and control these excitonic modes in thin film WSe2 by modifying the local geometry through nanosized cuts.

Stacking Fault Segregation Imaging With Analytical Field Ion Microscopy.

Stacking faults (SFs) are important structural defects that play an essential role in the deformation of engineering alloys. However, direct observation of SFs at the atomic scale can be challenging. Here, we use the analytical field ion microscopy, including density functional theory-informed contrast estimation, to image local elemental segregation at SFs in a creep-deformed solid-solution single-crystal alloy of Ni-2 at% W. The segregated atoms are imaged brightly, and time-of-flight spectrometry allows for their identification as W. We also provide the first quantitative analysis of trajectory aberration, with a deviation of approximately 0.4 nm, explaining why atom probe tomography could not resolve these segregations. Atomistic simulations of substitutional W atoms at an edge dislocation in face-centered cubic Ni using an analytic bond-order potential indicate that the experimentally observed segregation is due to the energetic preference of W for the center of the SF, contrasting with, for example, Re segregating to partial dislocations. Solute segregation to SF can hinder dislocation motion, increasing the strength of Ni-based superalloys. Yet, direct substitution of Re by W, envisaged to lower the superalloys' costs, requires extra consideration in alloy design since these two solutes do not have comparable interactions with structural defects during deformation.

Cellular targets of cytotoxic copper phenanthroline complexes: a multimodal imaging quantitative approach in single PC3 cells.

Metal complexes are emerging as promising alternatives to traditional platinum-based cancer treatments, offering reduced side effects. However, understanding their cellular uptake and distribution and quantify their presence at the single cell level remains challenging. Advanced imaging techniques, including transmission electron microscopy (TEM), synchrotron radiation X-ray fluorescence (SR-XRF) and energetic ion beam-based nuclear microscopy (STIM, scanning transmission ion microscopy; PIXE, particle-induced X-ray emission; EBS, elastic backscattering spectrometry), allow detailed high-resolution visualization of structure and morphology, high sensitivity for elemental detection with quantification within single cells, and the construction of three-dimensional (3D) models of metal distribution, positioning them as powerful tools for assessing the cellular uptake and compartmentalisation of complexes. Three Cu(II) complexes [Cu(phen)2(H2O)](NO3)2 (1), [Cu(Me2phen)2(NO3)]NO3 (2) and [Cu(amphen)2(H2O)](NO3)2 (3), (phen = 1,10-phenanthroline, Me2phen = 4,7-dimethyl-1,10-phen, amphen = 5-amino-phen) were investigated for Cu uptake and distribution in PC3 prostate cancer cells. All complexes show significant Cu-uptake regardless of media concentration. Cu-concentrations in cytoplasm and nucleus are similar between treatments. Complexes 1 and 3 concentrate Cu in the nuclear region and show a vesicle-like pattern around the nucleus, while 2 shows a dispersed cytoplasmic pattern with large vesicles. The 3D models confirm that Cu is not retained at the plasma membrane, with complex 1 targeting the nucleus and 2 remaining in the cytoplasm. These results highlight the importance of quantifying metal distribution and correlating it with structural changes to understand the relevance of the ligand in the mechanisms of cellular uptake and targeting, crucial for the development of effective metal-based cancer therapies.

Isolation and characterization of bacteriophages specific to Streptococcus equi subspecies zooepidemicus and evaluation of efficacy ex vivo.

Streptococcus (S.) equi subspecies (subsp.) zooepidemicus is an important facultative pathogen in horses and can cause severe infections in other species including humans. Facing the post-antibiotic era, novel antimicrobials are needed for fighting bacterial infections. Bacteriophages (phages) are the natural predators of bacteria and discussed as a promising antimicrobial treatment option. The objective of this study was to isolate and characterize S. equi subsp. zooepidemicus-specific phages for the first time and to evaluate their efficacy in vitro and ex vivo. In total, 13 phages with lytic activity were isolated and host ranges were determined. Two phages with broad host ranges and high efficiency of plating (vB_SeqZP_LmqsRe26-2 (lytic activity: 30/37 bacterial isolates) and vB_SeqZP_LmqsRe26-3 (lytic activity: 29/37 bacterial isolates)) and one phage with relatively low efficiency of plating (vB_SeqZP_LmqsRe26-1) were selected for further characterization, including electron microscopy and whole genome sequencing. In in vitro planktonic killing assays at two tested multiplicities of infection (MOI 1 and MOI 10), significant bacterial growth reduction was observed when the phages vB_SeqZP_LmqsRe26-2 and vB_SeqZP_LmqsRe26-3 were added. These phages were subsequently co-incubated with clinical S. equi subsp. zooepidemicus isolates in an equine endometrial explant model but did not achieve bacterial growth reduction at MOI 1 and MOI 10. However, helium ion microscopy revealed presence of particles adherent to the bacteria on the explant after incubation (25 h), suggesting possible phage-bacteria interactions. In conclusion, phages against S. equi subsp. zooepidemicus were successfully isolated and characterized. Promising results were observed in in vitro but no significant reduction was detected in ex vivo experiments, requiring additional investigations. However, after further adaptations (e.g., optimization of MOIs and phage administration or use of phage-antibiotic combination), phages could be a potential antimicrobial tool for future therapeutic use in S. equi subsp. zooepidemicus infections, although the available results do not currently support the therapeutic usage.

Field Ion Microscopy of Tungsten Nano-Tips Coated with Thin Layer of Epoxy Resin

This paper presents an analysis of the field ion emission mechanism of tungsten–epoxy nanocomposite emitters and compares their performance with that of tungsten nano-field emitters. The emission mechanism is described using the theory of induced conductive channels. Tungsten emitters with a radius of 70 nm were fabricated using electrochemical polishing and coated with a 20 nm epoxy resin layer. Characterization of the emitters, both before and after coating, was performed using electron microscopy and energy-dispersive X-ray spectroscopy (EDS). The Tungsten nanocomposite emitter was tested using a field ion microscope (FIM) in the voltage range of 0–15 kV. The FIM analyses revealed differences in the emission ion density distributions between the uncoated and coated emitters. The uncoated tungsten tips exhibited the expected crystalline surface atomic distribution in the FIM images, whereas the coated emitters displayed randomly distributed emission spots, indicating the formation of induced conductive channels within the resin layer. The atom probe results are consistent with the FIM findings, suggesting that the formation of conductive channels is more likely to occur in areas where the resin surface is irregular and exhibits protrusions. These findings highlight the distinct emission mechanisms of both emitter types.

Surface plasmons on silver gratings transform pyrolytic carbon into luminescent graphitized carbon dots.

Plasmonic catalysis holds the promise of opening new reaction pathways that are inaccessible thermally or via direct UV-vis electronic transitions. Here, energetic carriers produced via the decay of surface plasmons excited by visible light at 532nm (2.33eV, green) on a Ag-grating-bearing pyrolytic carbon residue drive its transformation into light-emitting graphitized carbon dots. The pyrolytic carbon residue is detectable via high-magnification surface-enhanced Raman scattering but cannot be directly observed using optical, electron, atomic force, or helium ion microscopy. When a Ag-grating-bearing pyrolyzed residue is introduced into a high-purity O2-depleted gas environment (Ar, N2, and CO2) and excited with 532nm light, bright yellow luminescence emerges and is readily observed. Light emission is not observed without the pyrolytic carbon, without the excitation of plasmons, or in air or an Ar/O2 gas mixture. This process, driven by visible light and a nanostructured Ag surface bearing pyrolytic carbon, will be of interest to researchers involved in plasmonic catalysis, catalytic processes involving carbon, and luminescent plasmonic surfaces.

Doped multi-walled carbon nanotubes and nanoclay based-geopolymer concrete: An overview of current knowledge and future research challenges

This in-depth review aims to shed light on the application of nanoclay and multi-walled carbon nanotubes in geopolymer concrete. It comprehensively examines the profound impact of these nanomaterials on the physical, chemical, and mechanical properties of geopolymer concrete. The review delves into the intricate details of the properties exhibited by nanoclay and multi-walled carbon nanotubes, providing valuable insights into their unique physical and chemical characteristics. It also explores the methodologies adopted for their dispersion and the underlying functionalities within geopolymer composite. The review highlights advanced imaging and characterization techniques essential for understanding surface and mechanical properties. The review compares imaging techniques (scanning electron microscopy, transmission electron microscopy, helium ion microscopy, and atomic force microscopy), emphasizing their importance in characterizing mechanical properties of nanocomposites. A detailed discussion on the fresh and hardened mechanical properties, specifically compressive and flexural strength, of geopolymer concrete incorporating nanoclay and multi-walled carbon nanotubes is also included. Addressing key challenges and offering perspectives on future developments in the realm of geopolymer concrete, this review serves as a comprehensive exploration of the subject.

Shifting shapes: Density variations and physicochemical characteristics from spheres to rods

This work extensively explores purifying cetyltrimethylammonium bromide (CTAB)-stabilized gold nanorods, focusing on efficiently separating spheres and rods to achieve a rod-rich suspension in one cycle. Utilizing UV–vis spectroscopy and Helium ion microscopy, the study delves into nanorods' spectral traits across different aspect ratios (AR 3–6). Results show centrifugation greatly influences gold nanorods' spectral features, indicating a link between CTAB-coated nanorod density and absorbance levels post-centrifugation. This quantitative evaluation enhances understanding of purification dynamics, highlighting effects on purity and density while offering insights for future refinements. Emphasizing centrifugation's role in reducing byproducts, nanoparticle density changes, and absorbance variations, the study's consistent spectral profiles affirm the effectiveness of purification parameters for stability and nanoparticle density maintenance. By quantitatively analyzing centrifugation duration's impact on spectral properties and shape separation dynamics, the research provides an empirical foundation for optimizing gold nanorod suspension purification processes. Additionally, a clear correlation between AR and absorbance-to-density ratios pre- and post-centrifugation underscores AR's relevance in comprehending nanorods' optical traits amidst centrifugation, benefiting purification strategies.

Theoretical and experimental perspectives on localized plasmons in gold nanospheroids

Theoretical frameworks play a pivotal role in comprehending the optical characteristics of gold nanorods, providing valuable perspectives on the factors that impact their optical properties. These frameworks play a key role in anticipating how nanorods will perform under different circumstances and in validating experimental findings against theoretical projections. Through the utilization of theoretical frameworks, scientists can efficiently delve into creative nanostructure designs, ultimately enriching our understanding of how gold nanorods react optically for both academic research and practical implementations. The optical behavior of elongated gold spheroids was extensively analyzed using both the quasi-static approximation (QSA) and the Modified Long Wavelength Approximation (MLWA) to gauge their effectiveness in projecting experimental results. While the QSA proves beneficial in specific scenarios, its accuracy tends to be overshadowed by empirical data obtained from UV–visible spectroscopy and helium ion microscopy (HIM). In contrast, the MLWA exhibits a stronger alignment with empirical findings, thus providing a more accurate theoretical groundwork. This alignment implies that the MLWA considers intricacies and variables overlooked by the QSA, establishing it as a more dependable approach for envisaging the optical conduct of such nanostructures. The juxtaposition emphasizes the significance of selecting appropriate theoretical frameworks in the realm of nanoscale optics, with the MLWA emerging as the preferred option for investigations concerning elongated gold spheroids.

Rubidium and Cesium Ion-Induced Electron and Ion Signals for Scanning Ion Microscopy Applications.

Scanning ion microscopy applications of novel focused ion beam (FIB) systems based on ultracold rubidium (Rb) and cesium (Cs) atoms were investigated via ion-induced electron and ion yields. Results measured on the Rb+ and Cs+ FIB systems were compared with results from commercially available gallium (Ga+) FIB systems to verify the merits of applying Rb+ and Cs+ for imaging. The comparison shows that Rb+ and Cs+ have higher secondary electron (SE) yields on a variety of pure element targets than Ga+, which implies a higher signal-to-noise ratio can be achieved for the same dose in SE imaging using Rb+/Cs+ than Ga+. In addition, analysis of the ion-induced ion signals reveals that secondary ions dominate Cs+ induced ion signals while the Rb+/Ga+ induced signals contain more backscattered ions.

Abstract P213: Mechanisms of Renin-Angiotensin System-Mediated Nitric Oxide Signaling in Podocytes

Introduction: The renin-angiotensin system (RAS) is a crucial cardiovascular and renal function regulator. Podocytes, glomerular epithelial cells that play a pivotal role in maintaining the renal filtration barrier, are key targets for RAS peptides. Our findings showed that RAS can promote calcium (Ca 2+ ) and nitric oxide (NO) signaling in podocytes. Moreover, a decrease in NO bioavailability directly correlates with glomerular filtration barrier damage, Ca 2+ overload, and the development of salt-sensitive hypertension. We hypothesized that RAS-mediated NO production is crucial for Ca 2+ control and cytoskeletal rearrangements in podocytes, contributing to glomerular filtration regulation. Methods: We performed live confocal imaging on human podocytes and freshly isolated rat glomeruli to detect the production of NO (DAF-FM) and Ca 2+ (Fluo-8). RAS peptides (Ang II, III, IV, 1-7, 1-9, and TRV120027) were used to stimulate cells, and NO and Ca 2+ production were measured. Blockers for Ang II Type 1 (AT1R), Ang II Type 2 (AT2R), and MAS receptors were used to identify the pathways involved in NO production. The dynamic changes in podocyte cytoskeleton mediated by RAS-NO intracellular signaling were detected using rhodamine-phalloidin staining and scanning ion microscopy. The NOS isoform-specific blockers were used to determine the source of NO in podocytes. ANOVA with post-hoc was used for comparisons. Results: Angiotensins II and III generate the most profound increases in NO levels in podocytes. Ang II, Ang III, and Ang 1-7 promote NO production by activating AT2R (n ≥ 20, p < 0.01). Interestingly, the increase in NO modulates AT1R- and β-arrestin-mediated Ca 2+ signaling (n ≥ 20, p < 0.05), suggesting the role of the NO/AT2R axis in Ca 2+ control in podocytes. NO production correlates with podocyte volume increase, and scanning ion microscopy experiments further confirmed that AT2R activation and corresponding NO elevation are responsible for the protrusion of podocyte's lamellipodia. Finally, we found that in podocytes, NOS1 is responsible for NO bioavailability, accounting for 69±5% of the total NO response, while the remaining NO levels are generated by NOS2 (39±5%). Conclusion: Our data show that RAS activation promotes NO production in podocytes, mainly via the AT2R pathway. NO is crucial for Ca 2+ control in podocytes and lamellipodia formation, suggesting the essential role of NO in glomerular filtration barrier function.

Gold nano densities: Relationship with drying parameters

Gold nanorod stain deposits have been studied using helium ion microscopy (HIM). The multilayer thick deposits can become well-organized monolayers when the density drops, as demonstrated by the density fluctuation of nanosuspension. However, once the density of nanoparticles approaches certain extremely low values, this tendency has disappeared. The difference in density associated with the liquid crystalline (LC) phases that have developed on the surface. There is a correlation between the density of nanoparticles in suspension and the relationship between droplet volume and UV-Vis absorbance. The physical characteristics that affect and generate such LC phases are contrasted and examined with the assembly method. To highlight noteworthy aspects, a quantitative comparison between the HIM analysis and the SEM is also made. Analyzing the correlation between the coffee stain range, nanoparticle density, and droplet contact angle is essential. It is possible to quantify the difference in the ring stains from the outside to the midle and from the midle to the inner boundary. HIM is typically useful when attempting to determine the true composition of surface deposits. The aim of this work is to investigate the effects of particle density on liquid crystalline superstructures and the coffee stain effect.

Hierarchical Incorporation of Reduced Graphene Oxide into Anisotropic Cellulose Nanofiber Foams Improves Their Thermal Insulation.

Anisotropic cellulose nanofiber (CNF) foams represent the state-of-the-art in renewable insulation. These foams consist of large (diameter >10 μm) uniaxially aligned macropores with mesoporous pore-walls and aligned CNF. The foams show anisotropic thermal conduction, where heat transports more efficiently in the axial direction (along the aligned CNF and macropores) than in the radial direction (perpendicular to the aligned CNF and macropores). Here we explore the impact on axial and radial thermal conductivity upon depositing a thin film of reduced graphene oxide (rGO) on the macropore walls in anisotropic CNF foams. To obtain rGO films on the foam walls we developed liquid-phase self-assembly to deposit rGO in a layer-by-layer fashion. Using electron and ion microscopy, we thoroughly characterized the resulting rGO-CNF foams and confirmed the successful deposition of rGO. These hierarchical rGO-CNF foams show lower radial thermal conductivity (λr) across a wide range of relative humidity compared to CNF control foams. Our work therefore demonstrates a potential method for improved thermal insulation in anisotropic CNF foams and introduces versatile self-assembly for postmodification of such foams.

Major and Trace Element Composition Differences Revealed in Porcine Intestine by Dynamic Analysis and MeV Ion Microscopy

Physiologically relevant concentrations in biological tissue, in the in vivo, state are of the order of μmol L−1 and mmol L−1. Up to the present, mapping the major elements in the matrix and its thickness has been neglected, despite their importance for quantification of lesser and trace element concentrations. Ryan and Jamieson's dynamic analysis, statistical spectral decomposition approach, is developed to quantitatively measure ex vivo tissue sections cut using a cryomicrotome. This mitigates the problem that physical analysis methods require a vacuum environment. This approach is used to quantitatively image the major matrix elements H, C, N, and O as well as trace maps of Ca, Fe, and Zn in a tissue section of porcine intestine. This sample is selected as it exhibits a complex morphology with multiple tissue compartments (such as muscle and mucosa, as well as void areas from blood vessels, lymph ducts, sinuses crypts, and villi. In the results, it is demonstrated that different tissue types can have a different matrix composition and thickness. Using this information, quantitative maps and elemental molarities for the lesser and trace elements Ca, Fe, and Zn are obtained.

The Behavior of High Scanning Electron Voltage Electron in SEM Due to Mirror Effect

To determine the factors influencing the electron scattering process in a scanning electron microscope caused by the electron mirror, a set of physical and mathematical ideas were used. These equations, which relate the scattering of the input electron with the surface potential energy of the dielectric material under examination using a matched beam ion microscope and scanning electrons, are based on simplified engineering mathematics. After five minutes of charging the insulator to saturation with an acceleration voltage of 30 kV, the accumulated charge was 0.3 nC, from which the surface voltage across the working distance (WD = 15 mm) was determined. The scattering angle (β) was found to be inversely proportional to the incidence angle (θ) in the second stage, when scanning voltages (Vsc=2, 4, and 6 kV) were employed. This was because the angle between the incident and scattered electron (2

Studies of the Morphology of Hematite Synthesized from Waste Iron Sulfate.

Microwave-based reactions have gained traction in recent years due to their ability to enhance reaction rates and yield while reducing energy consumption. Also, according to the conception of 'waste to materials', various waste feeds are intensively sought to be tested. The experimental setup of this study involved varying pH levels, oxidation agents, and precipitation agents to optimize the synthesis process of iron red based on waste iron sulfate. The selection of oxidation and precipitation agents was found to significantly influence the pigment synthesis process. Various oxidizing agents, including hydrogen peroxide and atmospheric air, were evaluated for their effectiveness in promoting the oxidation of ferrous ions to ferric ions, essential for pigment formation. Additionally, different precipitation agents such as sodium hydroxide and ammonia solution were assessed for their ability to precipitate iron hydroxides and facilitate pigment particle formation. The characterization of synthesized pigments revealed promising results in terms of quality and color properties. Helium Ion Microscopy (HIM) analysis confirmed the formation of well-defined pigment particles with controlled morphology. X-ray diffraction (XRD) studies provided insights into the crystalline structure of the pigments, indicating the presence of characteristic iron oxide phases. By improving this technology, waste iron sulfate can be efficiently transformed into valuable iron pigments, offering a sustainable solution for waste management while meeting the growing demand for high-quality pigments.

Shot noise-mitigated secondary electron imaging with ion count-aided microscopy

Modern science is dependent on imaging on the nanoscale, often achieved through processes that detect secondary electrons created by a highly focused incident charged particle beam. Multiple types of measurement noise limit the ultimate trade-off between the image quality and the incident particle dose, which can preclude useful imaging of dose-sensitive samples. Existing methods to improve image quality do not fundamentally mitigate the noise sources. Furthermore, barriers to assigning a physically meaningful scale make the images qualitative. Here, we introduce ion count-aided microscopy (ICAM), which is a quantitative imaging technique that uses statistically principled estimation of the secondary electron yield. With a readily implemented change in data collection, ICAM substantially reduces source shot noise. In helium ion microscopy, we demonstrate 3[Formula: see text] dose reduction and a good match between these empirical results and theoretical performance predictions. ICAM facilitates imaging of fragile samples and may make imaging with heavier particles more attractive.

CLIEMiT (Correlative Light Electron and Ion Microscopy in Tissue)

CLIEMiT (Correlative Light Electron and Ion Microscopy in Tissue)