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Introduction to Heterogeneous Catalysis in Organic Transformation
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Gyandshwar Kumar Rao, Varun Rawat, Ved Prakash Verma, Kaur Navjeet
An electron microscope is a type of microscope that uses a beam of accelerated electrons as a source of illumination. Since an electron’s wavelength can be much shorter than that of visible light photons, as a consequence, electron microscopes have a higher resolving power and can depict the structure of small particles. This method is used to create high-resolution pictures of biological and non-biological specimens. Electron microscopy is a recognized standard tool for nanomaterial characterization and can be used for determining the shape and size of solid catalysts [26]. It can be done in two modes: SEM (scanning electron microscopy) and TEM (transmission electron microscopy). The transmission electron microscope (TEM), the first-ever type of electron microscope, uses a large electron beam to visualize specimens and creates an image of the material. The scanning electron microscope (SEM) generates images by probing the sample with a concentrated electron beam that scans through a rectangular section of the sample. SEM is effective for visualizing catalyst particles (composition) and surfaces (topography) with micrometer diameters, but TEM is helpful for obtaining detailed structural information.
Desalination Membranes
Published in Andreas Sapalidis, Membrane Desalination, 2020
Rund Abu-Zurayk, Mohammed R. Qtaishat, Abeer Al Bawab
Electron microscopy is used to obtain very high-resolution images using a beam of accelerated electrons, which have very short wavelength under vacuum, as the source of illuminating radiation. Two main types of electron microscopy are scanning electron microscope (SEM) and transmission electron microscope (TEM).
Identifying Nanotoxicity at the Cellular Level Using Electron Microscopy
Published in Suresh C. Pillai, Yvonne Lang, Toxicity of Nanomaterials, 2019
Kerry Thompson, Alanna Stanley, Emma McDermott, Alexander Black, Peter Dockery
Nanomaterials and nanoparticles have been used extensively as additives for paint, in water treatment systems, cosmetics, as antimicrobials, as vehicles for drug delivery, and more recently as theranostic, diagnostic, and imaging probes for cells and tissues (Schrand et al., 2012, Lynch et al., 2015). To fully understand the potential effects of nanoparticles on an in vitro or in vivo system, the type and size of nanoparticle under investigation must be considered. Much of the work cited in this chapter refers to the interaction of nanoparticles with epithelial cells – the cells in the body which come into contact with the exterior (external environment) and line the body cavities. Electron microscopy is the sole technique or research tool capable of fully elucidating the ultrastructural alterations that may occur in a biological system after exposure to nanoparticles, therefore helping to shed light on the possible ultrastructural hallmarks of nanotoxicity. As the size of many of these nanomaterials and nanoparticles is similar to or below the wavelength of light, the micron scale of light microscopical observations is often inadequate to resolve and clearly demonstrate their features. The spatial resolution delivered by electron microscopy allows thorough identification and characterisation at the nanoscale via the production of high-magnification high-resolution data.
Colloidal lead in drinking water: Formation, occurrence, and characterization
Published in Critical Reviews in Environmental Science and Technology, 2023
Javier A. Locsin, Kalli M. Hood, Evelyne Doré, Benjamin F. Trueman, Graham A. Gagnon
In some cases, direct visualization of colloids may also be desired, which is impossible in methods previously discussed. Electron microscopes use electrons to produce an image of an object with magnification controlled by electric fields (Fig. 1). Two common electron microscopy methods are scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Since conventional SEM and TEM must be operated under a high vacuum, samples are dried. Thus, sample preparation is critical: the drying process may make it difficult to distinguish between agglomeration due to drying and aggregates already present in the sample or induce the crystallization of salts and structural alteration of colloids (Domingos et al., 2009). In contrast, environmental SEM (ESEM) and liquid TEM allows the in-situ observation of the sample (Daulton et al., 2001; Hülsey et al., 2019). However, they suffer from lower resolution due to electron interactions with the liquid layer (Peckys & de Jonge, 2011).
The dépaysement art of the new media era incorporating the microscopic world
Published in Digital Creativity, 2021
The use of electron microscopy in scientific experiments like nanotechnology may be due to its properties. First, because the electron microscope has a high resolution, it is possible to observe objects at high magnification. The Scanning Electron Microscope (SEM; Figure 5) generally has a magnification capacity of 100,000 times or more (resolution: 3–5 nm), and a high-performance scanning electron microscope of up to one million times (resolution: 0.5–2 nm). Second, the SEM can adjust magnification by changing the current flow through the coil without changing the lens, so it is possible to observe not only at high magnification but also at low magnification of 10–100 times. Therefore, after checking a wide range at low magnification, it is possible to move to a microregion of interest and measure at high magnification. Third, compared to optical microscopes, it has a greater depth of field for the sample (1921). In this study, the product CX-200PLUS of Coxem Co., Ltd. was used, which has a resolution of 3.0 nm at 30 kV and 8.0 nm at 3 kV, and a magnification between 15 and 300,000 times, allowing observation and photography. In order to observe with an electron microscope, it is necessary to coat the surface with a metal with good conductivity using an Ion Coater (Figure 6). In the coating process, a product called SPT-20 from Coxem Co., Ltd., was used. The metal most commonly used as a coating agent for electron microscopy is gold (Au), and the coating time varies depending on the type of object.
Chemical, thermophysical, rheological, and microscopic characterisation of rubber modified asphalt binder exposed to UV radiation
Published in Road Materials and Pavement Design, 2020
Mehdi Zadshir, Desiree Ploger, Xiaokong Yu, Cesare Sangiorgi, Huiming Yin
A Philips FEI (XL20) SEM was used to study the microscopic morphologies of the asphalt binders. Image formation in an electron microscope requires a high vacuum environment. Thus, the drying of samples was a prerequisite for viewing and obtaining good images in normal high vacuum SEM system. A rotary and a diffusion pump were used to vacuum-seal the samples at a maximum vacuum level of 1 × 10−4 torr. The metallisation process was performed using the aluminium coating. Coating of samples is required to make the samples conductive to avoid charging of electrons as well as to reduce thermal damage and improve the secondary electron signal required for topographic examination in the SEM. Therefore, a thin layer of aluminium (with a thickness of about 8 ± 3 Å) was coated on all samples. It should be noted that the increase in temperature during the coating phase is negligible with respect to the heating generated by the electron band during SEM scanning.