Transmission Electron Microscopy Techniques Research Articles

Electron Ptychography for Atom-by-Atom Quantification of 1D Defect Complexes in Monolayer MoS2.

Defect complexes can induce beneficial functionalities in two-dimensional (2D) semiconductors. However, understanding their formation mechanism with single-atom sensitivity has proven to be challenging for light elements using conventional transmission electron microscopy (TEM) techniques. Here, we demonstrate the atom-resolved formation of various one-dimensional (1D) defect complexes─consisting of rhenium dopants, sulfur interstitials, and sulfur vacancies─in monolayer MoS2 by applying electron ptychography to our four-dimensional scanning transmission electron microscopy (4D-STEM) data sets. Our image resolution of 0.35 Å and a spatial precision of 2 pm allow us to achieve accurate matching between experimental structures and density functional theory (DFT) simulations at the atomic level. Additionally, we utilize out-of-focus ptychography to observe defect formation processes at dose rates comparable to those used in conventional TEM imaging, while maintaining a large field of view. This study demonstrates the systematic application of electron ptychography to extensive 4D-STEM data sets for quantitative defect imaging in 2D materials. We provide direct, atomically precise evidence that critical defect densities govern the formation of extended 1D defect complexes. For instance, we show that sulfur single-vacancy lines form when the vacancy density reaches 5 × 1013 cm-2 and transform into double-vacancy lines beyond 8 × 1013 cm-2. Rhenium-dopant lines emerge at a dopant concentration higher than 3 × 1013 cm-2, where metastable sulfur interstitial-vacancy lines also form as the cumulative electron dose reaches 3 × 105 e/Å2, initiating a local nucleation of the 1T' phase. Our results highlight the potential of electron ptychography for high-precision defect characterization and engineering in ultrathin 2D materials.

Native state structural and chemical characterisation of Pickering emulsions: A cryo-electron microscopy study.

Transmission electron microscopy can be used for the characterisation of a wide range of thin specimens, but soft matter and aqueous samples such as gels, nanoparticle dispersions, and emulsions will dry out and collapse under the microscope vacuum, therefore losing information on their native state and ultimately limiting the understanding of the sample. This study examines commonly used techniques in transmission electron microscopy when applied to the characterisation of cryogenically frozen Pickering emulsion samples. Oil-in-water Pickering emulsions stabilised by 3 to 5nm platinum nanoparticles were cryogenically frozen by plunge-freezing into liquid ethane to retain the native structure of the system without inducing crystallisation of the droplet oil cores. A comparison between the droplet morphology following different sample preparation methods has confirmed the effectiveness of using plunge-freezing to prepare these samples. Scanning transmission electron microscopy imaging showed that dry droplets collapse under the microscope vacuum, changing their shape and size (average apparent diameter: ∼342nm) compared to frozen samples (average diameter: ∼183nm). Cryogenic electron tomography was used to collect additional information of the 3D shape and size of the emulsion droplets, and the position of the stabilising nanoparticles relative to the droplet surface. Cryogenic energy dispersive X-ray and electron energy loss spectroscopy were used to successfully obtain elemental data and generate elemental maps to identify the stabilising nanoparticles and the oil phase. Elemental maps generated from spectral data were used in conjunction with electron tomography to obtain 3D information of the oil phase in the emulsion droplets. Beam-induced damage to the ice was the largest limiting factor to the sample characterisation, limiting the effective imaging resolution and signal-to-noise ratio, though careful consideration of the imaging parameters used allowed for the characterisation of the samples presented in this study. Ultimately this study shows that cryo-methods are effective for the representative characterisation of Pickering emulsions.

Integration of p-Type PdPc and n-Type SnZnO into Hybrid Nanofibers Using Simple Chemical Route for Enhancement of Schottky Diode Efficiency

Palladium phthalocyanine (PdPc) and palladium phthalocyanine integrated with tin–zinc oxide (PdPc:SnZnO) were prepared using a simple chemical approach, and their structural and morphological properties were identified using X-ray diffraction, energy dispersive X-ray analysis, scanning electron microscopy, and transmission electron microscopy techniques. The PdPc:SnZnO nanohybrid revealed a polycrystalline structure combining n-type metal oxide SnZnO nanoparticles with p-type organic PdPc molecules. The surface morphology exhibited wrinkled nanofibers decorated with tiny spheres and had a large aspect ratio. The thin film revealed significant optical absorption within the ultraviolet and visible spectra, with narrow band gaps measured at 1.52 eV and 2.60 eV. The electronic characteristics of Al/n-Si/PdPc/Ag and Al/n-Si/PdPc:SnZnO/Ag Schottky diodes were investigated using the current–voltage dependence in both the dark conditions and under illumination. The photodiodes displayed non-ideal behavior with an ideality factor greater than unity. The hybrid diode showed considerably high rectification ratio of 899, quite a low potential barrier, substantial specific photodetectivity, and high enough quantum efficiency, found to be influenced by dopant atoms and the unique topological architecture of the nanohybrid. The capacitance/conductance–voltage dependence measurements revealed the influence of alternative current signals on trapped centers at the interface state, leading to an increase in charge carrier density.

Polymer/phytochemical mediated eco-friendly synthesis of Cu/Zn doped hematite nanoparticles revealing biological properties and photocatalytic activity

Abstract Unique magnetically recoverable copper/zinc-doped hematite nanoparticles, were synthesized by using a co-precipitation process with polymer polyvenylpyrodine and an aqueous extract of the Azadirachta indica plant serving as the capping and stabilizing agent. Hematite nanoparticles are the most stable form of iron oxide at room temperature, the presented work concentrated on the effects and comparisons of chemically and green synthesized doped materials that serve a dual role as reducing agents: supporting biomedical application and catalyzing environmental cleanup through photocatalysis. The prepared nanoparticles were characterized using X-ray diffraction, UV–vis spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, vibrating-sample magnetometry, scanning electron microscopy, and transmission electron microscopy techniques to examine the produced material. The average grain size for doped hematite nanoparticles was found to be 13.33–19.90 nm based on X-ray diffraction measurements. The Fourier-transform infrared spectroscopy spectrum demonstrates the function of the biomolecules in the extract in capping the nanoparticles. The ferrimagnetic character of the produced nanoparticles demonstrated by the Vibrating-sample magnetometer investigation showed dependence at 300 K. According to the phytochemical study, A. indica has components that enhance its photocatalytic and antioxidant activity. In comparison, chemical/green synthesized doped hematite nanoparticles demonstrated noticeably higher photocatalytic activity for the oxidative breakdown of hazardous organic dyes Rhodamine blue and Congo red. Additionally, the photocatalyst displayed outstanding stability for the reaction. Radical scavenger assays 2,2-diphenyl-1-picrylhydrazyl and 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) were used to measure antioxidant capability. Based on the assay, the bran and husk fractions displayed higher levels of antioxidant activity. This research is regarded as a novel step in the production of doped hematite nanoparticles with particular photocatalytic and biological characteristics for wide use in environmental, and agricultural areas.

Highly Green Fluorescent Carbon Dots from Gallic Acid: A Turn-On Sensor toward Pb2+ Ions.

Carbon dots (CDs) are emerging novel fluorescent sensing nanomaterials owing to their tunable optical properties, biocompatibility, and eco-friendliness. Herein, we report a facile one-pot hydrothermal route for the synthesis of highly green fluorescent CDs using gallic acid (GA) as a single carbon source in N,N-dimethylformamide (DMF) solvent, which serves as a nitrogen source and reaction medium. The optical properties of the synthesized GA-DMF CDs were systematically characterized by using UV-vis and photoluminescence spectroscopy, revealing strong green fluorescence. Further, to gain insights into their size and structural, elemental, and chemical composition, Fourier transform infrared, dynamic light scattering, high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction, and X-ray photoelectron spectroscopy characterization techniques were performed. HR-TEM analysis confirmed the formation of uniformly spherical GA-DMF CDs with an average particle size of 16 ± 6.1 nm. Notably, the GA-DMF CDs exhibited a highly selective and turn-on fluorescent response to Pb2+ ions in aqueous solutions, which was attributed to a chelation-enhanced fluorescence mechanism. The detection limit for Pb2+ ions was determined to be as low as 7.15 × 10-7 M, with a broad linear detection range of 30-130 μM, underscoring their sensitivity and practical application in water quality monitoring. This study introduces a novel, sustainable approach for synthesizing nitrogen-doped CDs with outstanding optical properties and highlights their unprecedented selectivity toward Pb2+ ions, advancing the development of efficient and eco-friendly sensing platforms for heavy metal detection.

Direct Observation of Dipole Interlocking Effect Occurrence in Two-Dimensional Ferroelectricity.

The electric dipole in materials is closely associated with their electronic transport, optical properties, and mechanical behavior. Here, we have employed the differential phase contrast (DPC) technique of the scanning transmission electron microscopy technique (STEM) to directly analyze the local electric dipole at the sub-Angstrom scale. By utilizing DPC-STEM technology, we successfully visualized the ferroelectric polarization of van der Waals material 3R α-In2Se3 and directly confirmed the dipole interlocking effect (DIE) between in-plane (IP) and out-of-plane (OOP) polarizations. Through density functional theory (DFT) calculations and structural analysis, we discovered that this DIE is caused by the central asymmetry of the middle Se atoms of each monolayer and that the reversal of polarization is accompanied by the emergence of an intermediate phase, β-In2Se3. Leveraging the DIE, we developed a multidirectional ferroelectric memristor that can effectively modulate the IP polarization by applying an OOP pulse voltage.

Silver Nanoparticles-Functionalized Textile against SARS-CoV-2: Antiviral Activity of the Capping Oleylamine Molecule.

COVID-19 disease, triggered by SARS-CoV-2 virus infection, has led to more than 7.0 million deaths worldwide, with a significant fraction of recovered infected people reporting postviral symptoms. Smart surfaces functionalized with nanoparticles are a powerful tool to inactivate the virus and prevent the further spreading of the disease. Literature reports usually focus on the role of nanomaterial composition and size dispersion in evaluating their efficacy against SARS-CoV-2. Here, the anti-SARS-CoV-2 activity of oleylamine (OAm) used as a capping agent of silver nanoparticles is quantified for the first time. Spherical hydrophobic nanoparticles with 8 ± 2 nm diameter were prepared and characterized by Fourier transform infrared, dynamic light scattering, and transmission electron microscopy techniques. Biological assays showed that microgram amounts of nanoparticles, deposited on nonwoven textile obtained from surgical masks, efficiently inactivated up to 99.6(2)% of the virus with just 2 min of exposure. The virucidal activity of the corresponding amount of free OAm has been determined as well, reaching up to 67(1)% of activity for an exposure time of 10 min. Inductively coupled plasma optical emission spectrometry results pointed out a low leaching out of the nanoparticles in contact with water or culture medium. All in all, these results propose the capping molecules as an important chemical variable to be taken into account in the design of fast, efficient, and long-lasting anti-SARS-CoV-2 coatings.

Direct Evidence of Anomalous Peierls Transition-Induced Charge Density Wave Order at Room Temperature in Metallic NaRu2O4.

In the field of quantum materials, understanding anomalous behavior under charge degrees of freedom through bond formation is of fundamental importance, with two key concepts: Dimerization and charge order at different cation sites. The coexistence of both dimerization and charge ordering is unusually found in NaRu2O4, even in its metallic state at room temperature. Our work unveils the origin of the interplay of these effects within metallic single-crystalline NaRu2O4. Employing advanced transmission electron microscopy techniques, we probe the lattice order of NaRu2O4 as a function of temperature and provide direct microscopic evidence of a Peierls-type transition. This transition is accompanied by a pronounced dimerization of the ruthenium chains, resulting in a distinctive twofold superstructure along the b axis below the critical transition temperature of ∼535 K, coinciding with a charge order. In situ heating experiments confirm the reversibility of this first-order phase transition, and periodic lattice displacement maps depict atomic-scale displacements linked to dimerization.

Green Synthesis of Metal Oxide Nanoparticles Using Plumbago zeylanica Root Extract, Spectrochemical Characterization, and Antibacterial Activity Against Common Pathogen

ABSTRACTThe root extract of Plumbago zeylanica was used to produce iron oxide (FeO), zinc oxide (ZnO), and copper oxide (CuO) nanoparticles. These metal oxides are easy to produce, inexpensive, and ecologically friendly, with considerable antibacterial activity against common infections. The purpose of this work is to explore a sustainable synthesis method and to investigate the comparative antibacterial activity of these nanoparticles. The nanoparticles were characterized using a variety of techniques, including energy‐dispersive X‐ray (EDX), transmission electron microscopy (TEM), ultraviolet‐visible (UV‐vis) spectrophotometry, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The XRD patterns revealed the crystalline structures of the produced metal oxide nanoparticles by displaying prominent, intense peaks. Morphological investigation utilizing SEM and TEM techniques revealed the nanoparticles’ shapes and sizes, with an average particle size ranging from 9 to 36 nm. EDX spectra verified the presence of an oxide layer on all three metal oxide nanoparticles. UV‐vis and FTIR spectroscopy revealed additional optical characteristics. The antibacterial activities of FeO, ZnO, and CuO nanoparticles were tested using disk diffusion assays against Salmonella enterica, Staphylococcus aureus, and Escherichia coli. The results showed that the antibacterial efficiency of these nanoparticles varied according to the type of bacteria. ZnO nanoparticles had the highest antibacterial activity against both Gram‐positive and Gram‐negative bacteria, while FeO nanoparticles had the lowest antibacterial efficacy. These data imply that ZnO nanoparticles, in particular, have antibacterial properties.

Dependency of mechanical properties in Ti-7Mo-3Al-3Cr-3Nb alloy on the β phase stability: Regulating primary α phase

In this study, the modification of the β-phase stability of Ti-7Mo-3Al-3Cr-3Nb alloy has been achieved by heat treatment at different temperatures. The synergy effects of primary α-phase and β-phase stability on the deformation behavior and mechanical properties were systematically studied based on these samples, combining the electron backscattering diffraction and transmission electron microscopy techniques. The content of the primary α-phase and stability of the β-phase increase when the heat treatment temperature is lowered from 860°C to 770°C, which increases the yield strength of the alloys. When the content of primary α-phase is less than 9%, high strength and ultra-high work-hardening rates can be simultaneously achieved, with maximum work-hardening reaching 12.75GPa and the ultimate tensile strengths reaching 846MPa. Stress-induced α′′ martensitic (SIM α′′) transformation is observed in all experimental samples during tensile deformation, and the trigger stress of martensitic transformation decreases with the decrease of β-phase stability. When the stability of the β-phase decreases, the quantity of SIM α′′ increases, while martensitic variants and twinned martensite increase to coordinate local strains. Meanwhile, as the strain increases, the martensite laths grow into martensite domains, which trigger martensite twins during deformation, and the interaction of the primary α-phase and β-phase deformation products will achieve different work-hardening rates. This study provides a possible strategy for the design and modification of new high-strength and 、work-hardening rate titanium alloys.

Clusterin induced by OPC phagocytosis blocks IL-9 secretion to inhibit myelination in a model of Alzheimer's disease.

Variants in the CLUSTERIN gene have been identified as a risk factor for late-onset Alzheimer's disease and are linked to decreased white matter integrity in healthy adults. However, the specific role for clusterin in myelin maintenance in the context of Alzheimer's disease remains unclear. We employed a combination of immunofluorescence and transmission electron microscopy techniques, primary culture of OPCs, and an animal model of Alzheimer's disease. We found that phagocytosis of debris such as amyloid beta, myelin, and apoptotic cells, increases clusterin expression in oligodendrocyte progenitors. We further discovered that exposure to clusterin inhibits differentiation of oligodendrocyte progenitors. Mechanistically, clusterin blunts production of IL-9 and addition of exogenous IL-9 can rescue clusterin-inhibited myelination. Lastly, we demonstrate that clusterin deletion in mice prevents myelin loss in the 5XFAD model. Our data suggest that clusterin could play a key role in Alzheimer's disease myelin pathology.

On the crystallography of plastic flow instabilities in FCC metals during impact loading: a study modelled on copper single crystals

Abstract The formation of shear bands (SBs) at high strain rates directly precedes the fracture of metals. Their appearance in the microstructure signals a reduction or complete loss of the load-bearing properties of a metallic parts. This paper analyses the crystallographic aspects of the mechanism responsible for the occurrence of this form of unstable metal flow under model conditions. The study examined Cu single crystals with unstable orientations close to C{112}<111> and S{123}<634>, which were deformed to logarithmic strains of 0.9 in a channel-die, with the punch driven by explosive energy to achieve a strain rate of 4 × 105 s−1. Microstructure and texture evolutions were characterized across a wide range of scales, primarily using scanning and transmission electron microscopy techniques. In both orientations analysed, the extremely high strain rate leads to intense deformation twinning, on all four {111} planes. The appearance of compact twin bundles of two generation, directly precedes the formation of SB. In each of the analysed cases, the rigid-body rotation of the crystal lattice in the band region, along with twinning in the reoriented matrix platelets, increases the density of texture components around the G{110}<001> orientation.

Molecular mechanism of action of tetracycline-loaded calcium phosphate nanoparticle to kill multi-drug resistant bacteria.

In earlier communications we reported about nanonization of the antibiotic tetracycline (Tet) by entrapping it within the biocompatible and highly membrane penetrating nano-carrier molecule - calcium phosphate nanoparticle (CPNP). The synthesized Tet-CPNP killed different Tet-resistant bacteria in vitro as well as in vivo (in mice). Moreover, such nanonized tetracycline had bactericidal mode of action, in contrast to bacteriostatic mode of action of bulk tetracycline. The present study unveils the molecular mechanism of action of Tet-CPNP. This study was conducted to investigate the mode of interaction of Tet-CPNP/Tet with intact 70S bacterial ribosome by the techniques of spectrophotometry, spectrofluorimetry, circular dichroism, gel electrophoresis and transmission electron microscopy. Experimental observations revealed that (i) binding affinity of Tet-CPNP was higher than that of only tetracycline with ribosome and (ii) binding of Tet-CPNP, but not of tetracycline, loosened ribosome conformation, finally disrupting and degrading ribosome. Bactericidal action of Tet-CPNP was rooted from degradation of cellular ribosomes and thereby blockage of protein translation phenomenon. Therefore, the problem of obsolescence of tetracycline, a cheap, first-generation, broad-spectrum antibiotic, due to generation of huge tetracycline-resistant bacteria, can be removed by the Tet-CPNP.

Bimetallic PdPt nanoparticle-incorporated PEDOT:PSS/guar gum-blended membranes for enhanced CO2 separation.

To address the escalating demand for efficient CO2 separation technologies, we introduce novel membranes utilizing natural polymer guar gum (GG), conjugate polymer (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) PEDOT:PSS, and bimetallic PdPt nanoparticles. Bimetallic PdPt nanoparticles were synthesized using the wet chemical method and characterized using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. The morphologies, chemical bonds, functional groups, and mechanical properties of the fabricated membranes were characterized using various techniques. Through meticulous fabrication and characterization, the binary blended membranes demonstrated enhanced homogeneity and smoothness in their structure, attributed to the interaction between the polymers, and superior CO2 permeability due to the amphiphilic nature of the PEDOT:PSS polymer. Gas separation experiments performed using H2, N2, and CO2 gases confirmed that the 20% PEDOT:PSS/GG blended membranes showed the best performance with sufficient mechanical properties. Moreover, the results demonstrated an increase of 172% in CO2 permeability and 138% in CO2/H2 selectivity, respectively. Furthermore, integrating bimetallic PdPt nanoparticles provided an additional 197% increase in CO2/H2 selectivity, owing to the unique catalytic activities of noble metal nanoparticles. The study not only underscores the transformative potential of polymer blending and noble metal engineering, but also highlights the significance of using natural polymers for sustainable environmental solutions.

Dry reforming of methane and interaction between NiO and CeZrPrOx oxide in different crystallographic plane

Methane dry reforming (DRM) holds promise as a pathway for converting methane into valuable synthesis gas (syngas) and high-value chemicals. In this study, we investigate the crystallographic plane interactions between nickel oxide (NiO) and a modified ceria-zirconia-praseodymium oxide support (CeZrPrOx) to elucidate their influence on catalytic activity in methane dry reforming. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) techniques were employed to characterize the catalyst. Our findings reveal that specific crystallographic planes significantly impact the catalytic performance of NiO/CeZrPrOx catalyst. The (111), (110), and (100) facets of the support material are examined for their interactions with NiO. We observe that the (110) plane of the support exhibits strong interaction with NiO, leading to enhanced catalytic activity. This interaction facilitates superior anchoring of Ni nanoparticles, lowering sintering and promoting a strong metal-support interaction effect (SMSI). Additionally, our analysis suggests that the (110) interface is particularly favorable for methane dry reforming. Overall, this study highlights the importance of crystallographic plane interactions in NiO/CeZrPrOx catalysts and offers valuable insights for optimizing catalyst design for methane conversion processes.

Comparative electron diffraction analysis of strain relaxation in AlxGa1-xN materials in the microelectronics industry: 4D-STEM approach vs. TEM-based N-PED solution.

Owing to its high spatial resolution and its high sensitivity to chemical element detection, transmission electron microscopy (TEM) technique enables to address high-level materials characterization of advanced technologies in the microelectronics field. TEM instruments fitted with various techniques are well-suited for assessing the local structural and chemical order of specific details. Among these techniques, 4D-STEM is suitable to estimate the strain distribution of a large field of view. This study tends to discuss the viability of using two existing commercial solutions with a low-convergence angle 4D-STEM technique and TEM-based Nanobeam Precession Electron Diffraction (N-PED) methods for strain analysis in an industrial context. In such a framework, strain measurements intend to point out the extent of defects and thus reveal a trend of the stress field, rather than to precisely estimate the absolute values of the deformations. Strain distribution maps have been obtained for AlGaN/GaN HEMT devices using two transmission electron diffraction analysis methods. The performances of 4D-STEM and Nanobeam Precession Electron Diffraction (N-PED) solution for strain mapping have been compared for both a relatively thin (≈ 55 nm) and a thick (≈ 150 nm) TEM cross section specimen. The strain maps obtained with both methods have shown comparable results for a thin sample, with the ability to characterize the deformation induced by a 1 nm-thick layer of AlN spacer grown between the AlGaN barrier and GaN channel forming the 2DEG of the HEMT device. The results presented here also illustrate the limitation of both commercial solutions in the case of a thick sample.

Improving anti-oxidant stress treatment of subarachnoid hemorrhage through self-assembled nanoparticles of oleanolic acid

Subarachnoid hemorrhage (SAH) is a life-threatening acute hemorrhagic cerebrovascular disease, with early brain injury (EBI) being the main cause of high mortality and severe neurological dysfunction. Oxidative stress plays a crucial role in the pathogenesis of EBI. In this study, we synthesized antioxidant stress nanoparticles based on self-assembled oleanolic acid (OA) using the solvent volatilization method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) techniques were employed to analyze and understand the self-assembly mechanism of oleic acid nanoparticles (OA NPs). The TUNEL assay, Nissl staining, and brain water content measurements were conducted to investigate the impact of OA NPs on cortical neuronal injury. Additionally, Western blot analysis was performed to investigate the antioxidant stress mechanism of OA NPs. The result showed that OA NPs exhibited a spherical structure with an average diameter of 168 nm. The application of OA NPs in SAH has been found to contribute to the reduction of keap1 protein levels and an increase in the nuclear level of Nrf2. As a result, the transcription of antioxidant stress proteins, including HO1 and NQO1, is triggered. The activation of the antioxidant stress pathway by OA NPs ultimately leads to a decrease in neuron damage and an improvement in neurological dysfunction. In conclusion, we successfully designed and synthesized OA NPs that can efficiently target the site of SAH. These nanoparticles have demonstrated their potential as antioxidants for the treatment of SAH, offering significant clinical applications.

Morphofunctional Characteristics of the Mouse Small Intestine Mucosa After a sIngle Irradiation with Various Absorbed Doses

Radiation-induced intestinal damage is a typical complication of radiation exposure, it can be caused by various sources of radiation. Clinical treatment today consists of symptomatic supportive therapy, as there are no specific treatment strategies. The main target of radiation damage is the epithelial cells of the mucous membrane of the small intestine. The study of morphological changes and mechanisms of damage to epithelial cells is necessary when developing the model of radiation damage to the intestine for further assessment of the severity of pharmacological correction. The purpose of the work is to provide a morphological assessment to the state of the epithelial tissue in the mouse small intestine mucosa on the 9th day after a single exposure to X-ray radiation at various absorbed doses (6.5, 7 and 7.8 Gy). Materials and methods. The study was performed on sexually mature white outbred male mice weighing 18-22 g (n = 50). Acute radiation sickness was simulated using the RUM-17 X-ray therapy unit. The animals of the three experimental groups (n = 15 each) received a single X-ray irradiation with different absorbed doses of 6.5, 7 and 7.8 Gy, respectively. On the 9th day after irradiation, the material was fixed according to a routine technique for transmission electron microscopy. The analysis of semifine sections was carried out using a Scope A1c light microscope with an Axiocam ERc 5s camera and using the ZEN 2.3 morphometric program with further processing using Microsoft Office Excel 2013. Results. When exposed to radiation with different absorbed doses on the mucous membrane of the jejunum in mice, common morphological features were revealed: a decrease in the height and deformation of the mucous membrane villi; a decrease in the height of enterocytes from 32.03±2.21 µm in intact animals to 22.86±0.51 µm (at 7 Gy); in crypts, the height of epithelial cells had no significant changes; single dividing cells were located along the entire depth of the crypts; an increase in the length of the microvilli in the brush border on the apical surface of enterocytes from 0.89±0.01 µm to 1.46±0.03 µm (at 7.8 Gy) was revealed. Sublethal and lethal doses are characterized by a slight expansion of the basal parts of crypts with profiles of actively synthesizing goblet cells, in the absorbed dose of 6.5 Gy, similar changes are more pronounced. In all animals of the experimental groups, the loose connective tissue of the proper mucous plate is abundantly infiltrated by leukocytes. Epithelial cell extrusion zones are weakly expressed on the apical surfaces of the villi. A sharp decrease in the number of Paneth cells was revealed. Conclusions. On the 9th day after a single exposure to X-ray radiation at absorbed doses of 6.5, 7 and 7.8 Gy, reactive changes in the epithelial tissue of the mucous membrane of the small intestine have a non-specific character. The most pronounced of them were noted at an absorbed dose of 6.5 Gy. A decrease in the absorbing surface of the mucous membrane results in disturbances of its basic function.

Tracing the Formation of Femtosecond Laser-Induced Periodic Surface Structures (LIPSS) by Implanted Markers.

The generation of laser-induced periodic surface structures (LIPSS) using femtosecond lasers facilitates the engineering of material surfaces with tailored functional properties. Numerous aspects of their complex formation process are still under debate, despite intensive theoretical and experimental research in recent decades. This particularly concerns the challenge of verifying approaches based on electromagnetic effects or hydrodynamic processes by experiment. In the present study, a marker experiment is designed to conclude on the formation of LIPSS. Well-defined concentration depth profiles of 55Mn+- and 14N+-ions were generated below the polished surface of a cast Mn- and Si-free stainless steel AISI 316L using ion implantation. Before and after LIPSS generation, marker concentration depth profiles and the sample microstructure were evaluated by using transmission electron microscopy techniques. It is shown that LIPSS predominantly formed by material removal through locally varying ablation. Local melting and resolidification with the redistribution of the material occurred to a lesser extent. The experimental design gives quantitative access to the modulation depth with a nanometer resolution and is a promising approach for broader studies of the interactions of laser beams and material surfaces. Tracing LIPSS formation enables to unambiguously identify governing aspects, consequently guiding the path to improved processing regarding reproducibility, periodicity, and alignment.

The Impact of Single Amino Acid Insertion on the Supramolecular Assembly Pathway of Aromatic Peptide Amphiphiles.

Understanding the mechanism of self-assembly driven by non-covalent interactions is crucial for designing supramolecular materials with desired properties. Here we investigate the self-assembly of aromatic peptide amphiphiles, Fmoc-L2QG and Fmoc-L3QG using a combination of spectroscopic, transmission electron and superresolution optical microscopy techniques. Our results show that Fmoc-L2QG leads to concentration-dependent assembly, forming fibrous assemblies at low concentrations and supramolecular droplets via liquid-liquid phase separation (LLPS) at higher concentrations. Mechanical activation using for example ultrasonication triggered the transition from metastable droplets to fibre morphologies of Fmoc-L2QG. In contrast, Fmoc-L3QG followed both on-pathway and off-pathway routes, resulting in the formation of fibrous morphologies regardless of concentration. Seeding experiments revealed that homo-seeds of the same peptide sequence accelerated the on-pathway process, while hetero-seeds of a mismatched peptide sequences accelerated the off-pathway process, highlighting the competing nature of the complex assembly profile. These findings demonstrate the significant impact of single amino acid insertion on the supramolecular assembly process of oligopeptide monomers, and highlight the potential for controlling the structure and dynamics of peptide materials. Pathway engineering of oligopeptide building blocks and multidomain supramolecular monomers will open new avenues in tailor-made and customizable supramolecular biomaterials.