Electron Microscopy Of Samples Research Articles

Surface potential distribution of resist exposed by electron beam and the non-charging exposure conditions.

In this study, we experimentally analyzed the charging phenomenon when an insulating resist film on a conductive layer formed on bulk glass is irradiated by electron beams (EBs). To quantify the charging potential induced, an electrostatic force microscope device was installed in the scanning electron microscope sample chamber, and potential distributions formed under various exposure conditions were obtained. Based on the results obtained, a model for charge accumulation within the sample, explaining positive and negative charging and their transitions, was developed. At an EB acceleration voltage of 30 kV, the following observations were made: 'global charging' could be avoided by applying -5 V to the sample. Regarding 'local charging' near the exposure area of the EB, at low exposure doses, emission of secondary electrons from the sample surface induced positive charging, while the accumulation of incident electrons within the sample induced negative charging. At exposure doses where the effects of both are balanced, the sample exhibited zero potential, revealing the appearance of the 'first zero-cross exposure dose'. At higher exposure doses, the sample transitions from negative to positive as the exposure dose increases due to the electron-beam-induced conduction, resulting in the so-called second zero-cross exposure dose. The exposure dose dependence of the charging potential distribution at various acceleration voltages was obtained. In particular, we found that at an acceleration voltage of 0.6 kV, the sample surface is not charged even when exposed to small to very large doses of EBs.

Influence of Initial Film Properties in UVO-Mediated Patterning of an Elastomeric Film Using a TEM Grid.

Ultraviolet irradiation of a cross-linked polydimethylsiloxane (PDMS) Sylgard 184 film in the presence of atmospheric oxygen (UVO) through a bare transmission electron microscope (TEM) sample holding grid is a rather simple and widely utilized technique for creating micropatterned surfaces. The surface oxidation of a Sylgard 184 film due to UVO exposure is associated with densification and the formation of a silica-like surface layer, which under a TEM grid happens only over the exposed areas of the film, resulting in a physicochemical pattern. It is known that the depth (hD) of the features depends on the duration of UVO exposure (tE). In this article, we show for the first time that hD also depends on the initial film thickness (hF) and the cross-linker percentage (CL, ratio of part A to part B) in a Sylgard 184 thin film. We show that for a specific tE, hD progressively decreases with the reduction in hF. On the other hand, hD shows a nonmonotonic dependence with CL, resulting in patterns with maximum depth for CL ≈ 10.0%. We attribute this observation to the combined effect of resistance against the penetration of the propagation front by the rigid substrate as well as stress relaxation within the exposed parts of the film below the propagating front in films with higher CL values leading to the variation of hD. The observation reported here would allow the potential fabrication of polymer films with physicochemical patterns with feature height on demand by a one-step, facile technique.

Operando Liquid-cell Transmission Electron Microscope Sample Holder with Bulk Reference and Counter Electrodes for Electrocatalysis Applications

Operando Liquid-cell Transmission Electron Microscope Sample Holder with Bulk Reference and Counter Electrodes for Electrocatalysis Applications

Pre- and Postembedding Immunoelectron Microscopy to Analyze the Central Nervous System.

Immunocytochemistry, a method of delineating the subcellular localization of target proteins, was developed from immunohistochemistry. In principle, proteins are labeled using an antigen-antibody reaction. In order to observe under an electron microscope, the reaction product must scatter the electron beam with sufficient contrast while it is necessary to have an amplifying label that can withstand the observation. We have some detailed tips on making electron microscope samples to achieve this objective, and we would be happy to help you.

Utilizing magnetic xanthan gum nanocatalyst for the synthesis of acridindion derivatives via functionalized macrocycle Thiacalix[4]arene

An effective method for synthesizing acridinedione derivatives using a xanthan gum (XG), Thiacalix[4]arene (TC4A), and iron oxide nanoparticles (IONP) have been employed to construct a stable composition, which is named Thiacalix[4]arene-Xanthan Gum@ Iron Oxide Nanoparticles (TC4A-XG@IONP). The process used to fabricate this nanocatalyst includes the in-situ magnetization of XG, its amine modification by APTES to get NH2-XG@IONP hydrogel, the synthesis of TC4A, its functionalization with epichlorohydrine, and eventually its covalent attachment onto the NH2-XG@IONP hydrogel. The structure of the TC4A-XG@IONP was characterized by different analytical methods including Fourier-transform infrared spectroscopy, X-Ray diffraction analysis (XRD), Energy Dispersive X-Ray, Thermal Gravimetry analysis, Brunauer–Emmett–Teller, Field Emission Scanning Electron Microscope and Vibration Sample Magnetomete. With magnetic saturation of 9.10 emu g−1 and ~ 73% char yields, the TC4As-XG@IONP catalytic system demonstrated superparamagnetic property and high thermal stability. The magnetic properties of the TC4A-XG@IONP nanocatalyst system imparted by IONP enable it to be conveniently isolated from the reaction mixture by using an external magnet. In the XRD pattern of the TC4As-XG@IONP nanocatalyst, characteristic peaks were observed. This nanocatalyst is used as an eco-friendly, heterogeneous, and green magnetic catalyst in the synthesis of acridinedione derivatives through the one-pot pseudo-four component reaction of dimedone, various aromatic aldehydes, and ammonium acetate or aniline/substituted aniline. A combination of 10 mg of catalyst (TC4A-XG@IONP), 2 mmol of dimedone, and 1 mmol of aldehyde at 80 °C in a ethanol at 25 mL round bottom flask, the greatest output of acridinedione was 92% in 20 min.This can be attributed to using TC4A-XG@IONP catalyst with several merits as follows: high porosity (pore volume 0.038 cm3 g−1 and Pore size 9.309 nm), large surface area (17.306 m2 g−1), three dimensional structures, and many catalytic sites to active the reactants. Additionally, the presented catalyst could be reused at least four times (92–71%) with little activity loss, suggesting its excellent stability in this multicomponent reaction. Nanocatalysts based on natural biopolymers in combination with magnetic nanoparticles and macrocycles may open up new horizons for researchers in the field.

Exploring the Potential Mechanism of Action of Piperine against Candida albicans and Targeting Its Virulence Factors.

Plant-derived compounds have proven to be a source of inspiration for new drugs. In this study, piperine isolated from the fruits of Piper nigrum showed anti-Candida activity. Furthermore, the mechanisms of action of piperine and its impact on virulence factors in Candida albicans, which have not been comprehensively understood, were also assessed. Initially, piperine suppressed the hyphal transition in both liquid and solid media, hindered biofilm formation, and resulted in observable cell distortions in scanning electron microscope (SEM) samples, for both fluconazole-sensitive and fluconazole-resistant C. albicans strains. Additionally, the morphogenetic switches triggered by piperine were found to rely on the activity of mutant C. albicans strains. Secondly, piperine treatment increased cell membrane permeability and disrupted mitochondrial membrane potential, as evidenced by propidium iodine and Rhodamine 123 staining, respectively. Moreover, it induced the accumulation of intracellular reactive oxygen species in C. albicans. Synergy was obtained between the piperine and the fluconazole against the fluconazole-sensitive strain. Interestingly, there were no hemolytic effects of piperine, and it resulted in reduced cytotoxicity on fibroblast cells at low concentrations. The results suggest that piperine could have a dual mode of action inhibiting virulence factors and modulating cellular processes, leading to cell death in C. albicans.

FIB-shield: a structure to safely transfer and precisely mount beam-sensitive TEM specimens under focused ion beam

Focused ion beam (FIB) has been adopted extensively for transmission electron microscope (TEM) sample preparation during the past decades. However, ion beam- and deposition-induced damage during transferring and mounting of the sample cannot be effectively avoided, limiting the application of FIB in ion-beam illumination-sensitive samples. A transferring device called the FIB shield is designed and fabricated to greatly reduce the damage and contamination of the sample during transfer and mounting under Ga+ beam imaging, milling and Pt deposition. Nearly damage-free transfer and precise positioning and attachment of beam-sensitive in situ TEM nanoindentation samples are achieved. The effectiveness of the shielding plate to block Ga+ radiation damage during Ga+ beam imaging and milling and that of the buffer region to alleviate sputtering damage during Pt deposition are verified by corresponding experiments.

Examining the impact of cement on porosity evolution in the upper triassic Kurra Chine Formation of Sirwan valley, Kurdistan region, Iraq: A study integrating cathodoluminescence and scanning electron microscopy

The study of carbonate petrography is essential for understanding reservoir properties and the quality of rock formations. High-resolution cathodoluminescence spectroscopy and optical microscopy were used to determine the impact of cement on the porosity evolution of carbonate rocks of the Kurra Chine Formation at Sirwan Valley, Northern Iraq. This study represents the first-ever attempt to investigate sedimentology at this location. A total, of 183 thin-section slides, 18 X-Ray Diffraction (XRD) samples, 14 Scanning Electron Microscope (SEM) samples, and 6 Cathodoluminescence (CL) samples were analyzed from the outcrop section of the Kurra Chine Formation. Four types of dolomite textures are recognized and classified based on the crystal size distribution and crystal-boundary shape. The porosity within Kurra Chine Formation includes primary and secondary porosity, with the majority of primary porosity being occluded by cementation. Cathodoluminescence analysis revealed two phases of calcite cement in the Kurra Chine Formation. The first phase (C1), is characterized by weak-zoned blocky calcite, displaying a dull luminescence with typical homogenous red color, which fills most of the interparticle and moldic pores. The second type of calcite cement (C2) is ghost-zoned calcite exhibiting red to slight orange luminesces interfingering with dolomite cement. XRD analysis indicated a predominant of calcite and common dolomite. SEM analysis revealed the predominance of secondary porosity occurring within fractures of the dolomite.

Ultrastructural and morphological analysis during progression of Bowen disease reveals a complex interplay between hyperkeratosis, cytokeratin expression, host immunity and amyloid deposition.

Bowen disease, one of the common skin cancers, is defined as squamous cell carcinoma in situ, characterized by atypical keratinocytes occupying the full thickness of the epidermis, and predominantly occurs on sun-protected skin. There is no existing data on the impact of tumour and immune cell interactions or cytokeratin expression on the pathology of Bowen disease. We analysed dynamic changes in cytokeratin expression and immune cell composition during the development and progression of Bowen disease. Analysis was performed using immunohistochemistry and electron microscopy for samples from 140 patients with Bowen disease and 20 patients with invasive squamous cell carcinoma. We evaluated cytokeratin expression, the number of infiltrating immune cells and amyloid deposition by immunohistochemistry, and the ultrastructural relationship between tumour cells and immune cells by electron microscopy. The results showed that the expression of CK14 is associated with tumour progression, keratotic status and amyloid deposition and that the expression of CK10 is associated with accumulation of immune cells in Bowen disease. The findings of electron microscopy indicated repeated battles involving immune cells in response to tumour invasion. The expression of cytokeratins, hyperkeratosis, inflammatory infiltration and amyloid deposition are useful findings indicating the "stage" in Bowen disease.

Parameters, Properties, and Process: Conditional Neural Generation of Realistic SEM Imagery Toward ML-Assisted Advanced Manufacturing

The research and development cycle of advanced manufacturing processes traditionally requires a large investment of time and resources. Experiments can be expensive and are hence conducted on relatively small scales. This poses problems for typically data-hungry machine learning tools which could otherwise expedite the development cycle. We build upon prior work by applying conditional generative adversarial networks (GANs) to scanning electron microscope (SEM) imagery from an emerging advanced manufacturing process, shear-assisted processing and extrusion (ShAPE). We generate realistic images conditioned on temper and either experimental parameters or material properties. In doing so, we are able to integrate machine learning into the development cycle, by allowing a user to immediately visualize the microstructure that would arise from particular process parameters or properties. This work forms a technical backbone for a fundamentally new approach for understanding manufacturing processes in the absence of first-principle models. By characterizing microstructure from a topological perspective, we are able to evaluate our models’ ability to capture the breadth and diversity of experimental scanning electron microscope (SEM) samples. Our method is successful in capturing the visual and general microstructural features arising from the considered process, with analysis highlighting directions to further improve the topological realism of our synthetic imagery.

Autologous Fat Grafting in Reconstructive Breast Surgery: Clinically Relevant Factors Affecting the Graft Take.

Autologous fat grafting is an effective tool for soft tissue augmentation in reconstructive breast surgery. Despite the major advantages of this minimally invasive approach, the unpredictability of graft survival presents challenges. No clear consensus on the optimal technique has yet been published and well-defined prospective studies investigating impairing factors are lacking. This aim of this study was to generate valuable fundamental data. Ten female patients undergoing elective autologous fat grafting after nipple-sparing mastectomy were enrolled. Punch biopsies and lipoaspirates were collected from the harvest site for histologic, gene expression, and scanning electron microscopic analysis. Noninvasive Lipometer measurements determining the subcutaneous adipose tissue thickness at the graft site were used to calculate the respective take rate. Patient- and surgery-related data were acquired and correlated with the take rate. A statistically relevant correlation between the take rate and the existing mean subcutaneous adipose tissue thickness at the grafted breast prior to surgery was observed. An approximate correlation was identified regarding the number of previous grafting sessions, body weight, and BMI. No statistically significant correlation was demonstrated for age, harvest site, or the mean adipocyte size. A lower level of cell damage was observed in scanning electron microscopic samples of washed lipoaspirates; and a strong indirect correlation with the expression of the adipocyte markers FABP4 and PLIN1 was apparent. Factors correlating to the take rate were identified. Future studies investigating the clinical relevance of each impairing factor are essential to contribute to the optimization of this valuable method.

Strain states and unique properties in cold-rolled TiNi shape memory alloys

Martensitic transformation (MT), strain glass transition (SGT) and the corresponding stress-strain responses in cold-rolled Ti49.2Ni50.8 shape memory alloys (SMAs) at various amounts of cold-rolling deformation are investigated. A phase diagram describing all the strain states and transitions among them is established in the temperature – deformation space. It shows a normal sharp, strong first-order B2 to B19′ MT at low deformation levels (cold-rolling thickness reduction εp < 27%), but a continuous B2 to B19′ SGT at high deformation levels (εp ≥ 27%) upon cooling. Superelasticity with small hysteresis, tunable modulus and functional-fatigue resistance properties are achieved by altering the transition behavior from MT to SGT at εp ≥ 27%. Nanodomains of single variant B19′ martensite at the atomic scale are observed by using aberration-corrected scanning transmission electron microscopy in samples with εp = 27%. Further in-situ loading synchrotron-based high energy X-ray diffraction technique shows that the quasi-linear superelasticity associated with the SGT can be attributed to stress-induced continuous growth of B19′ nanodomains. Geometrical phase analysis of high-resolution transmission electron microscopy image reveals a nanoscale network of severe lattice distortion associated with the accumulated high-density of defects at εp ≥ 27%, which is the microstructural origin of the B19′ strain glass state. This work provides a detailed explanation for the longstanding puzzle of unique quasi-linear superelastic response in plastically deformed TiNi SMAs, and may shed light on achieving novel mechanical properties through defect engineering.

Effects of Electron Microscope Parameters and Sample Thickness on High Angle Annular Dark Field Imaging.

Scanning transmission electron microscopy (STEM) developed into a very important characterization tool for atomic analysis of crystalline specimens. High-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) has become one of the most powerful tools to visualize material structures at atomic resolution. However, the parameter of electron microscope and sample thickness is the important influence factors on HAADF-STEM imaging. The effect of convergence angle, spherical aberration, and defocus to HAADF imaging process has been analyzed through simulation. The applicability of two HAADF simulation software has been compared, and suggestions for their usage have been given.

Using Xe Plasma FIB for High-Quality TEM Sample Preparation.

A direct comparison between electron transparent transmission electron microscope (TEM) samples prepared with gallium (Ga) and xenon (Xe) focused ion beams (FIBs) is performed to determine if equivalent quality samples can be prepared with both ion species. We prepared samples using Ga FIB and Xe plasma focused ion beam (PFIB) while altering a variety of different deposition and milling parameters. The samples’ final thicknesses were evaluated using STEM-EELS t/λ data. Using the Ga FIB sample as a standard, we compared the Xe PFIB samples to the standard and to each other. We show that although the Xe PFIB sample preparation technique is quite different from the Ga FIB technique, it is possible to produce high-quality, large area TEM samples with Xe PFIB. We also describe best practices for a Xe PFIB TEM sample preparation workflow to enable consistent success for any thoughtful FIB operator. For Xe PFIB, we show that a decision must be made between the ultimate sample thickness and the size of the electron transparent region.

Development of an atmospheric plasma jet device for versatile treatment of electron microscope sample grids

Atmospheric-pressure plasmas have been widely applied for surface modification and biomedical treatment because of their ability to generate highly reactive radicals and charged particles. In negative-stain electron microscopy (Neg-EM) and cryogenic electron microscopy (cryo-EM), plasmas have been used to generate hydrophilic surfaces and eliminate surface contaminants to embed specimens onto grids. In addition, plasma treatment is a prerequisite for negative-stain and Quantifoil grids, whose surfaces are coated with hydrophobic amorphous carbon. Although the conventional glow discharge system has been used successfully in this purpose, there has been no further effort to take an advantage from the recent progress in the plasma field. Here, we developed a nonthermal atmospheric plasma jet system as an alternative tool for treatment of surfaces. The low-temperature plasma is a nonequilibrium system that has been widely used in biomedical area. Unlike conventional glow discharge systems, the plasma jet system successfully cleans and introduces hydrophilicity on the grid surface in the ambient environment without a vacuum. Therefore, we anticipate that the plasma jet system will have numerous benefits, such as convenience and versatility, as well as having potential applications in surface modification for both negative-stain and cryo-EM grid treatment.

Influence of Ce3+ on the Structural, Morphological, Magnetic, Photocatalytic and Antibacterial Properties of Spinel MnFe2O4 Nanocrystallites Prepared by the Combustion Route

The present work describes the effect of Ce3+ ion doping on the structural, morphological, and magnetic properties of spinel manganese ferrite (MnFe2O4) nanocrystallites (NCs) using various instrument techniques. Rare earth element (REE) Cerium (Ce3+) doped MnFe2O4 NCs were prepared by a simple microwave combustion technique. In the present scenario, ferrites are widely used for photocatalytic dye degradation and antibacterial applications. Aiming to achieve this, we prepared Ce3+ doped MnFe2O4 NCs by microwave combustion method and urea as burning agent and the obtained powder samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high resolution scanning electron microscope (HR-SEM), high resolution transmission electron microscope (HR-TEM) and vibration sample magnetometer (VSM) techniques. The pure spinel phase formation was confirmed by XRD analysis. FTIR spectra show two prominent absorption bands under 1000 cm−1, which confirms the formation of the spinel structure. HR-SEM and HR-TEM pictures demonstrated a sphere-shaped morphology and also expose the combination and agglomeration of grains, which are mostly due to the magnetic characteristics of the samples. The magnetic properties of the synthesized MnCexFe2−xO4 (x = 0.0, 0.1, 0.3, and 0.5) NCs were studied by VSM analysis at room temperature (RT) shows ferromagnetic behavior. The photodegradation results showed that MnFe2O4 and Ce doped MnFe2O4 NCs have a higher potential to degrade methylene blue (MB) and the sample MnCe0.3Fe1.7O4 NCs showed superb photocatalytic performance (91.53%) compared to other samples. The antibacterial activities of Gram-positive S. aureus, B. subtilis and Gram-negative K. pneumonia and E. coli were investigated using pure and Ce3+ substituted MnFe2O4 NCs and a higher activity for MnCe0.3Fe1.7O4 NCs than other samples was observed, which indicated that they can be used in biomedical applications.

Microstructure of a Damascene sabre after annealing

Abstract X-ray phase analysis combined with high-resolution electron microscopy of samples taken from a genuine Damascus sabre after annealing for 24 hat 400 °C and 800 °C followed by slow cooling down to room temperature has led to a better insight into the nature of cementite nanowires, which have been discovered recently. According to the present study, nanowires remained after 400 °C annealing, but disappeared after heat treatment at 800 °C and subsequent cooling down. On the other hand, perlitic cementite has been retained qualitatively after the same treatment. Knowing that the exceptional mechanical properties of Damascene blades disappear after annealing, the present results suggest a significant influence of the nanowires upon these features.

Scanning Electron Microscope Observation of Arabidopsis Pollen Under Two Treatment Conditions

We observed pollen in the late development stages of fresh wild Arabidopsis thaliana by scanning electron microscope, using direct spraying of gold and the conventional biological electron microscope sample preparation method, and made comparative analyses. Arabidopsis pollen prepared according to the conventional biological electron microscope sample preparation method can maintain intact and clear outer wall structure under scanning electron microscopy. However, after direct spraying of gold, only mature pollen could be observed relatively clear outer wall structure, and no clear observation results could be obtained for pollen in other stages. Our results showed that the outer wall morphology of the mature pollen can be observed by direct gold spraying with fresh materials. This method is easy to operate and saves time. For the immature pollen, especially the pollen in the later stage of development, direct gold spraying will affect the pollen morphology, so we recommend using the conventional biological electron microscope sample preparation method to obtain the best shooting effect. The results of this study might provide some useful reference for researchers to observe the pollen outer wall structure in the late development stages of Arabidopsis thaliana by scanning electron microscope.

Microstructural refinement by the formation of acicular ferrite on Ti–Mg oxide inclusion in low-carbon steel

In this paper, the mechanical properties and microstructure of hot-rolled low carbon steel containing Ti–Mg oxide inclusions as well as the effect of austenite grain size on acicular ferrite (AF) nucleation and the nucleation mechanism of AF were studied. The results indicated that the dominant inclusions in Ti–Mg deoxidized steel comprised Ti–Mg–Mn–O·MnS, which effectively promoted the nucleation of AF; thus, the microstructure after hot rolling consisted of fine AF and bainite (B). The variety of tensile property of Ti–Mg deoxidized steel was not obvious but the low-temperature impact toughness was significantly improved from 4 J to 126 J at −40 °C compared with Al deoxidized steel. Increasing the austenitizing temperature contributed to the nucleation of AF, and large amounts of fine AF formed in Ti–Mg deoxidized steel when the austenitizing temperature was 1250 °C with an average austenite grain size of ~92 μm. Two kinds of nucleation mechanisms of AF were elucidated: a Nishiyama-Wasserman (N–W) orientation relationship of (100)ferrite‖(110)oxide, [011]ferrite‖[-111]oxide between AF and Ti–Mg–Mn–O oxide, which caused low lattice disregistry, and a Mn-depleted zone (MDZ) around Ti–Mg–Mn–O·MnS inclusions. In order to investigate the reason for the formation of the MDZ, focused ion beam (FIB) was used to prepare the transmission electron microscope (TEM) sample containing a Ti–Mg–Mn–O·MnS inclusion, the specific orientation relationship of (-11-1)MnS‖(11–1)oxide, [-112]MnS‖[011]oxide between MnS and the Ti–Mg–Mn–O oxide was examined, and the atomic image of the Ti–Mg–Mn–O oxide was observed. The precipitation of MnS on the surface of Ti–Mg–Mn–O oxide followed by the absorption of Mn atoms by Ti–Mg–Mn–O oxide resulted in the formation of a MDZ around Ti–Mg–Mn–O·MnS inclusions.

Enhanced Electro-Magnetic Wave Absorbing Properties of Fe3O4-Polyaniline Nano-Composites

Fe3O4-polyaniline (Fe3O4-PANI) binary nano-composites have been prepared by in-situ polymerization of aniline monomer on surface of Fe3O4 magnetic nano-particles. The morphology, structure and magnetic performance are characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM) and vibration sample magnetism (VSM). The electro-magnetic data is tested by vector network analyzer demonstrating that the minimum reflection loss (RLmin) value of Fe3O4-PANI is -26 dB at 17 GHz with 1.5 mm thickness and 3.48 GHz (14.52 GHz~18 GHz) absorbing bandwidth (RL &lt; -10 dB). It is believed that such composites will have a promising application in the future.