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Correlative scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM) imaging of the same region of a multi-walled carbon nanotube (CNT) specimen. a: 2 keV secondary electron (SE)-SEM overview image, (b) high-magnification 30 keV SE-SEM image from the region marked with a white frame in (a), (c) 30 keV bright field (BF)-STEM image, and (d) 30 keV high-angle annular dark field (HAADF)-STEM image. The inset in (c) shows a high-resolution BF-STEM image taken from the area marked with a black rectangle.
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Transmission electron microscopy (TEM) with low-energy electrons has been recognized as an important addition to the family of electron microscopies as it may avoid knock-on damage and increase the contrast of weakly scattering objects. Scanning electron microscopes (SEMs) are well suited for low-energy electron microscopy with maximum electron ene...
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... scanning electron columns of two DualBeam instruments (FEI Strata 400S and FEI Helios G4 FX, DualBeam, Frankfurt/ Main, Germany) equipped with a field-emission gun were used in this work. The images in Figures 2, 3, 5, 7 were taken in the FEI Helios G4 FX. Imaging of the magnetic steel sample (Fig. 6) was performed with the FEI Strata 400S. ...
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... overview SE-SEM image of multi-walled CNTs deposited on a holey carbon film is shown in Figure 2a. Increasing the magnification in the region marked with the white frame gives an impression of the surface topography and three-dimensional arrangement of the CNTs (Fig. 2b). ...
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... overview SE-SEM image of multi-walled CNTs deposited on a holey carbon film is shown in Figure 2a. Increasing the magnification in the region marked with the white frame gives an impression of the surface topography and three-dimensional arrangement of the CNTs (Fig. 2b). Due to their small thickness, multi-walled CNTs are semi-transparent in the 30 keV SE-SEM images. The BF-STEM image (Fig. 2c) from the same region clearly reveals the inner CNT structure. It shows the presence of NPs (black arrows in Figs. 2c, 2d) which were used as catalysts for CNT fabrication. The particles are Ni, as revealed by ...
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... deposited on a holey carbon film is shown in Figure 2a. Increasing the magnification in the region marked with the white frame gives an impression of the surface topography and three-dimensional arrangement of the CNTs (Fig. 2b). Due to their small thickness, multi-walled CNTs are semi-transparent in the 30 keV SE-SEM images. The BF-STEM image (Fig. 2c) from the same region clearly reveals the inner CNT structure. It shows the presence of NPs (black arrows in Figs. 2c, 2d) which were used as catalysts for CNT fabrication. The particles are Ni, as revealed by energy-dispersive X-ray spectroscopy. The position of the catalyst particles is indicated by arrows in Figure 2b to point out ...
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... white frame gives an impression of the surface topography and three-dimensional arrangement of the CNTs (Fig. 2b). Due to their small thickness, multi-walled CNTs are semi-transparent in the 30 keV SE-SEM images. The BF-STEM image (Fig. 2c) from the same region clearly reveals the inner CNT structure. It shows the presence of NPs (black arrows in Figs. 2c, 2d) which were used as catalysts for CNT fabrication. The particles are Ni, as revealed by energy-dispersive X-ray spectroscopy. The position of the catalyst particles is indicated by arrows in Figure 2b to point out the absence of SE-contrast, which clearly demonstrates that the particles are not located at the upper CNT surface. ...
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... particles are Ni, as revealed by energy-dispersive X-ray spectroscopy. The position of the catalyst particles is indicated by arrows in Figure 2b to point out the absence of SE-contrast, which clearly demonstrates that the particles are not located at the upper CNT surface. Diffraction-contrast features are visible in the BF-STEM image Figure 2c. ...
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... position of the catalyst particles is indicated by arrows in Figure 2b to point out the absence of SE-contrast, which clearly demonstrates that the particles are not located at the upper CNT surface. Diffraction-contrast features are visible in the BF-STEM image Figure 2c. Bragg diffraction and overlapping Bragg diffraction disks on the BF-detector segment are mandatory prerequisites for obtaining high-resolution BF-STEM images. ...
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... 2c. Bragg diffraction and overlapping Bragg diffraction disks on the BF-detector segment are mandatory prerequisites for obtaining high-resolution BF-STEM images. This corresponds to phase-contrast imaging in the STEM. Lattice fringes with a distance of 3.7 Å are indeed resolved for the inner-shell distance in the multiwalled CNTs (cf. insert in Fig. 2c) in agreement with TEM results (Belin & Epron, 2005). HAADF-STEM images are sensitive to the average atomic number and the local thickness of the specimen (Howie, 1979). The high image intensity of the particles confirms that they consist of a material with substantially higher atomic number than carbon. Locally enhanced intensity is ...
Citations
... The sample-processing method described by Cheng et al. [17] was adopted. A volume of 1 mL of fermentation broth was extracted and transferred to a 2 mL centrifuge tube. ...
In recent years, magnetic fields have emerged as a non-thermophysical treatment with a significant impact on microbial fermentation processes. Brassica trispora is a microorganism known for its industrial-scale production of lycopene and high yield of single cells. This study aimed to investigate the impact of low-frequency magnetic fields on lycopene synthesis by Brassica trispora and elucidate the underlying mechanism for enhancing lycopene yield. The results indicate that both the intensity and duration of the magnetic field treatment influenced the cells. Exposing the cells to a 0.5 mT magnetic field for 48 h on the second day of fermentation resulted in a lycopene yield of 25.36 mg/g, representing a remarkable increase of 244.6% compared to the control group. Transcriptome analysis revealed that the alternating magnetic field significantly upregulated genes related to ROS and the cell membrane structure, leading to a substantial increase in lycopene production. Scanning electron microscopy revealed that the magnetic field treatment resulted in a rough, loose, and wrinkled surface morphology of the mycelium, along with a few micropores, thereby altering the cell membrane permeability to some extent. Moreover, there was a significant increase in intracellular ROS content, cell membrane permeability, key enzyme activity involved in lycopene metabolism, and ROS-related enzyme activity. In conclusion, the alternating frequency magnetic field can activate a self-protective mechanism that enhances lycopene synthesis by modulating intracellular ROS content and the cell membrane structure. These findings not only deepen our understanding of the impact of magnetic fields on microbial growth and metabolism but also provide valuable insights for developing innovative approaches to enhance carotenoid fermentation.
... STEM images can also be obtained by SEM and TEM. 47 However, it is usually obtained by TEM because it requires the sample to be thin. In order to improve the resolution of ultrahigh resolution electron microscopy, it uses a sample table that can place the sample inside the objective lens. ...
High performance dielectric capacitors are ubiquitous components in the modern electronics industry, owing to the highest power density, fastest charge-discharge rates, and long lifetime. However, the wide application of dielectric capacitors is limited owing to the low energy density. Over the past decades, multiscale structures of dielectric ceramics have been extensively explored and many exciting developments have been achieved. Despite the rapid development of energy storage properties, the atomic structure of dielectric materials is rarely investigated. In this paper, we present a brief overview of how scanning transmission electron microscopy (STEM) is used as a tool to elucidate the morphology, local structure heterogeneity, atomic resolution structure phase evolution and the correlation with energy storage properties, which provides a powerful tool for rational design and synergistic optimization.
... 14 Alternative acquisition modes, such as annular dark-field scanning TEM were examined, for example, in Pfaff et al. (2011) and Sun et al. (2018). 15 Note that this violates the assumptions underlying BL law that yield linear log-ratio dependence of intensities on t. 16 The magnitude of the deviation from linear log-ratio dependence observed here indicates that spectrometer background alone (Egerton & Crozier, 1989) can not explain the nonlinearity and saturation. ...
Energy-filtering transmission electron microscopy (TEM) and bright-field TEM can be used to extract local sample thickness $t$ and to generate two-dimensional sample thickness maps. Electron tomography can be used to accurately verify the local $t$ . The relations of log-ratio of zero-loss filtered energy-filtering TEM beam intensity ( $I_{{\rm ZLP}}$ ) and unfiltered beam intensity ( $I_{\rm u}$ ) versus sample thickness $t$ were measured for five values of collection angle in a microscope equipped with an energy filter. Furthermore, log-ratio of the incident (primary) beam intensity ( $I_{\rm p}$ ) and the transmitted beam $I_{{\rm tr}}$ versus $t$ in bright-field TEM was measured utilizing a camera before the energy filter. The measurements were performed on a multilayer sample containing eight materials and thickness $t$ up to 800 nm. Local thickness $t$ was verified by electron tomography. The following results are reported:
• The maximum thickness $t_{{\rm max}}$ yielding a linear relation of log-ratio, $\ln ( {I_{\rm u}}/{I_{{\rm ZLP}}})$ and $\ln ( {I_{\rm p}}/{I_{{\rm tr}}} )$ , versus $t$ .
• Inelastic mean free path ( $\lambda _{{\rm in}}$ ) for five values of collection angle.
• Total mean free path ( $\lambda _{{\rm total}}$ ) of electrons excluded by an angle-limiting aperture.
• $\lambda _{{\rm in}}$ and $\lambda _{{\rm total}}$ are evaluated for the eight materials with atomic number from $\approx$ 10 to 79.
The results can be utilized as a guide for upper limit of $t$ evaluation in energy-filtering TEM and bright-field TEM and for optimizing electron tomography experiments.
... Standard STEM detectors, which are formed of several segments for imaging in BF and DF modes, consist of many photodiodes. This detector has a wide range of applications, for example, in material analysis [16][17][18][19], in life science [20] and in semiconductors [21]. Conversely, the full annular distribution is not resolved because the signal incident on the inactive areas between the individual segments is lost. ...
The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample.
... For each XY-position on the sample, the multi-segmental STEM detector can yield signal from each of its segments. This is occasionally called multidimensional STEM, where the additional dimension is the angular resolution [4]. The final step was the recent commercialization of 2D-array detectors (also known as pixelated detectors). ...
A modern scanning electron microscope equipped with a pixelated detector of transmitted electrons can record a four-dimensional (4D) dataset containing a two-dimensional (2D) array of 2D nanobeam electron diffraction patterns; this is known as a four-dimensional scanning transmission electron microscopy (4D-STEM). In this work, we introduce a new version of our method called 4D-STEM/PNBD (powder nanobeam diffraction), which yields high-resolution powder diffractograms, whose quality is fully comparable to standard TEM/SAED (selected-area electron diffraction) patterns. Our method converts a complex 4D-STEM dataset measured on a nanocrystalline material to a single 2D powder electron diffractogram, which is easy to process with standard software. The original version of 4D-STEM/PNBD method, which suffered from low resolution, was improved in three important areas: (i) an optimized data collection protocol enables the experimental determination of the point spread function (PSF) of the primary electron beam, (ii) an improved data processing combines an entropy-based filtering of the whole dataset with a PSF-deconvolution of the individual 2D diffractograms and (iii) completely re-written software automates all calculations and requires just a minimal user input. The new method was applied to Au, TbF3 and TiO2 nanocrystals and the resolution of the 4D-STEM/PNBD diffractograms was even slightly better than that of TEM/SAED.
... Electron microscopy (EM) including scanning and transmission electron microscopies has become one of the most attractive cutting-edge analytical techniques thanks to the considerable progress in the development of electron guns and optics, detectors, signal processing and various installations for cryo/in situ/operando studies [118,[145][146][147][148][149][150][151][152][153][154]. ...
Halloysite is a tubular clay nanomaterial of the kaolin group with a characteristic feature of oppositely charged outer and inner surfaces, allowing its selective spatial modification. The natural origin and specific properties of halloysite make it a potent material for inclusion in biopolymer composites with polysaccharides, nucleic acids and proteins. The applications of halloysite/biopolymer composites range from drug delivery and tissue engineering to food packaging and the creation of stable enzyme-based catalysts. Another important application field for the halloysite complexes with biopolymers is surface coatings resistant to formation of microbial biofilms (elaborated communities of various microorganisms attached to biotic or abiotic surfaces and embedded in an extracellular polymeric matrix). Within biofilms, the microorganisms are protected from the action of antibiotics, engendering the problem of hard-to-treat recurrent infectious diseases. The clay/biopolymer composites can be characterized by a number of methods, including dynamic light scattering, thermo gravimetric analysis, Fourier-transform infrared spectroscopy as well as a range of microscopic techniques. However, most of the above methods provide general information about a bulk sample. In contrast, the combination of electron microscopy with energy-dispersive X-ray spectroscopy allows assessment of the appearance and composition of biopolymeric coatings on individual nanotubes or the distribution of the nanotubes in biopolymeric matrices. In this review, recent contributions of electron microscopy to the studies of halloysite/biopolymer composites are reviewed along with the challenges and perspectives in the field.
... The constructs were fixed in 2.5% glutaraldehyde, postfixed with 0.1% osmium tetroxide, dehydrated through an ethanol series, dried in a CO2 dryer, coated with gold, and examined with (SEM). (23) 2-After scarification, the specimens were removed and fixed in 10% neutral buffered formalin. Samples were decalcified using Ethylene Diamine Tetra Acetic acid (EDTA) for histological examination. ...
... Scanning electron microscopes can be equipped with numerous detectors for secondary electron (SE), backscattered electron (BSE) and STEM imaging due to less stringent space restrictions in the sample chamber. Taking STEM and SEM images simultaneously from the same specimen region will be referred to as correlative SEM/low-keV STEM in the following and is shown to provide complementary and comprehensive information from the same sample region [11]. For instance, a modern scanning electron microscope allows to simultaneously obtain topography contrast from SE-SEM images, material contrast from BSE-SEM images, Bragg diffraction contrast from bright-field (BF)-STEM images and mass-thickness contrast from high-angle annular dark-field (HAADF)-STEM images. ...
... One way to simulate STEM intensities is based on solving the analytical transport equation [23] with the scattering distribution of the multiple scattered electrons evaluated numerically by using a series of Legendre polynomials [24]. Within this work, we used the software CeTE 1.4 [11] to support understanding of the experimentally observed HAADF-STEM intensities. In the simulations, screened Rutherford differential cross-sections for elastic electron scattering were used. ...
Scanning electron microscopy (SEM) is an indispensable characterization technique for materials science. More recently, scanning electron microscopes can be equipped with scanning transmission electron microscopy (STEM) detectors, which considerably extend their capabilities. It is demonstrated in this work that the correlative application of SEM and STEM imaging techniques provides comprehensive sample information on nanomaterials. This is highlighted by the use of a modern scanning electron microscope, which is equipped with in-lens and in-column detectors, a double-tilt holder for electron transparent specimens and a CCD camera for the acquisition of on-axis diffraction patterns. Using multi-walled carbon nanotubes and Pt/Al2O3 powder samples we will show that a complete characterization can be achieved by combining STEM (mass-thickness and diffraction) contrast and SEM (topography and materials) contrast. This is not possible in a standard transmission electron microscope where topography information cannot be routinely obtained. We also exploit the large tilt angle range of the specimen holder to perform 180 degrees STEM tomography on multi-walled carbon nanotubes, which avoids the missing wedge artifacts.
... The latter is favorable to distinguish weakly scattering materials with similar material densities and average atomic numbers. Although STEM resolution in scanning electron microscopes is still lower than in transmission electron microscopes, best instruments meanwhile provide a spatial resolution of ~ 0.34 nm which is sufficient to tackle numerous materials problems [4,5]. Another advantage of scanning electron microscopes is the inherent availability of surface topography imaging by secondary-electron scanning electron microscopy (SE-SEM), which can be correlatively applied in combination with STEM. ...
canning transmission electron microscopy (STEM) at low energies (≤ 30 keV ) in a scanning electron microscope is well suited to distinguish weakly scattering materials with similar materials properties and analyze their microstruc-ture. The capabilities of the technique are illustrated in this work to resolve material domains in PTB7:PC71BM bulk-het-erojunctions, which are commonly implemented for light-harvesting in organic solar cells. Bright-field (BF-) and high-angle annular dark-field (HAADF-) STEM contrast of pure PTB7 and PC71BM was first systematically analyzed using a wedge-shaped sample with well-known thickness profile. Monte-Carlo simulations are essential for the assignment of material contrast for materials with only slightly different scattering properties. Different scattering cross-sections were tested in Monte-Carlo simulations with screened Rutherford scattering cross-sections yielding best agreement with the experimental data. The STEM intensity also depends on the local specimen thickness, which can be dealt with by correlative STEM and scanning electron microscopy (SEM) imaging of the same specimen region yielding additional topography information. Correlative STEM/SEM was applied to determine the size of donor (PTB7) and acceptor (PC71BM) domains in PTB7:PC71BM absorber layers that were deposited from solution with different contents of the processing additive 1,8-diiodooctane (DIO)
(PDF) Imaging of polymer:fullerene bulk-heterojunctions in a scanning electron microscope: methodology aspects and nanomorphology by correlative SEM and STEM. Available from: https://www.researchgate.net/publication/339699538_Imaging_of_polymerfullerene_bulk-heterojunctions_in_a_scanning_electron_microscope_methodology_aspects_and_nanomorphology_by_correlative_SEM_and_STEM [accessed Mar 05 2020].
... This measurement aimed to compare the surface morphologies of frankincense and processed frankincense. SEM has become an indispensable tool and was used for topography imaging of powder samples in this study [28,29]. SEM images of frankincense and processed frankincense exhibited a significantly different status of the powder sample ( Figure 1A,B). ...
Boswellic acids (BAs), as the main components of frankincense, exhibit notable anti-inflammatory properties. However, their pharmaceutical development has been severely limited by their poor oral bioavailability. Traditional Chinese medicinal processing, called Pao Zhi, is believed to improve bioavailability, yet the mechanism is still completely unclear. Previous research suggested that the bioavailability of a drug can be influenced by physical properties. This paper was designed to investigate the physical properties of frankincense and processed frankincense, including the surface morphology, particle size, polydispersity index (PDI), zeta potential (ZP), specific surface area, porosity, and viscosity. The differences in the intestinal absorption characteristics and equilibrium solubilities between frankincense and processed frankincense were determined by an ultra-high-performance liquid chromatography coupled with a triple quadrupole electrospray tandem mass spectrometry (UHPLC-TQ-MS) analysis method. The results showed that vinegar processing can alter the surface morphology, decrease the particle size and PDI, raise the absolute values of the ZP, specific surface area and porosity, and drop the viscosity of frankincense. Meanwhile, the rates of absorption and dissolution of the main BAs were increased after the processing of frankincense. The present study proves that the physical properties were changed after processing, in which case the bioavailability of frankincense was enhanced.
