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Characteristics of the Metal–Metal Oxide Reaction Matrix
Published in Anthony Peter Gordon Shaw, Thermitic Thermodynamics, 2020
The lightest chalcogen is oxygen, and oxygen-transfer reactions are the primary topic of this book. The other chalcogens include sulfur, selenium, tellurium, and polonium. The last member of the group, polonium, is highly radioactive. Sulfur, selenium, and tellurium can function as fuels and as oxidizers in pyrotechnic compositions. These elements combine with oxygen to form dioxides. Sulfur dioxide is a gas at room temperature, whereas SeO2 and TeO2 are solids. Sulfur, selenium, and tellurium also react with electropositive metals to form sulfides, selenides, and tellurides.
Literature review
Published in Joyabrata Mal, Microbial Synthesis of Chalcogenide Nanoparticles, 2018
Chalcogens are the chemical elements of the group 16 of the periodic table such as oxygen, sulfur (S), selenium (Se), tellurium (Te) and polonium (Po). The metalloid chalcogens such as S, Se and Te are used in semiconductors and in the preparation of MeCh. Among the various colloidal semiconductor nanoparticles, MeCh NPs such as CdS, ZnS, CdSe, and CdTe have attracted considerable attention due to their quantum confinement effects and size dependent photoemission characteristics (Joo et al., 2003). The fluorescent MeCh NPs are superior to organic fluorophores in terms of narrow absorption and emission spectra, quantum yield and photostability (Mussa & Valizadeh, 2012). The photooptical and photovoltaic properties of MeCh are particularly suited for their use in solar cells and optoelectronic sensors (Gaponik et al., 2002; Trindade et al., 2001). QDs are widely used in the field of biology and medicine for imaging, sensing (Gao et al., 2010a; Gao et al., 2004; Medintz et al., 2005; Michalet et al., 2005; Park et al., 2011; Sapsford et al., 2006; Smith et al., 2008) and tracking particles or cells (Chang et al., 2008; Maa et al., 2014) including fluorescent biolabelling and cancer detection (Jie et al., 2011).
The Future of Electronics
Published in John D. Cressler, Silicon Earth, 2017
Stop #3: Phase change memory. Phase-change memory (Chalcogenide RAM or C-RAM) is a new type of nonvolatile memory. C-RAMs exploit the unique properties of so-called “chalcogenide glasses.” Say what?! Recall: The chalcogens are the chemical elements in Group XVI (16) of the periodic table and consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po). Chalcogenide glasses (C-glasses) are glasses that contain one or more chalcogens. Duh! C-glasses that are useful for memory apps include: GeSbTe and AgInSbTe. In phase change memory, heat produced by the passage of a current through a heating element is used either to: (1) quickly heat and thus quench the glass, making it amorphous, or (2) to hold it in its crystallization temperature range, thereby switching it to a crystalline state (Figure 13.41) [33]. That is, we change the resistance of the C-glass layer via a phase change! Quite clever. C-RAM also has the ability to achieve a number of distinct intermediary states (i.e., intermediate phase states), thereby having the ability to hold multiple bits in a single memory cell, which is quite novel (and useful!).
DFT analysis of the active site in catalytic metabolic redox reactions of mononuclear molybdenum enzymes
Published in Journal of Coordination Chemistry, 2018
The chalcogen elements (i.e. elements of group 16 of the periodic table)—oxygen, sulfur and selenium—fulfill a wide range of essential biological functions. All three elements are constituents of functional groups in biomolecules that participate in redox reactions [1, 2]. There are close similarities but also striking differences between sulfur and selenium in terms of their chemistry and biochemistry. Both S and Se are present in proteins as constituents of the natural amino acids cysteine, methionine, selenocysteine and selenomethionine [3] and also occur as substrates, e.g. for the sulfite oxidase and selenate reductase enzymes, respectively. These are mononuclear molybdenum enzymes. All mononuclear molybdoenzymes contain a molybdenum cofactor, Moco, which consists of either one or two organic moieties of metallopterin (MPT) or some of its nucleotide variants, coordinated to Mo through an enedithiolate motif. Based on the active site composition, i.e. the number of MPT and type of additional ligands, these enzymes are generally grouped into three families (Figure 1); the xanthine oxidase (XO) family [4–7], the sulfite oxidase (SO) family [4, 8–10], and the dimethylsulfoxide reductase (DMSOR) family [4, 11–13].
Applications and challenges of elemental sulfur, nanosulfur, polymeric sulfur, sulfur composites, and plasmonic nanostructures
Published in Critical Reviews in Environmental Science and Technology, 2019
Yong Teng, Qixing Zhou, Peng Gao
Sulfur atoms as redox-active cysteine residues were incorporated into proteins during the period of rising oxygen concentration in the Earth’s atmosphere, and antioxidant molecules such as thioredoxin, glutathione, and glutaredoxin appeared (Nagahara & Wróbel, 2017). Methionine, cysteine, homocysteine, and taurine are the common sulfur-containing amino acids, but only methionine and cysteine are incorporated into proteins (Brosnan & Brosnan, 2006). Sulfur accompanied with oxygen and selenium belongs to the chalcogen elements and are constituents of functional groups in biomolecules exerting a wide range of essential biological functions (Jacob et al., 2003).
In-plane magnetic penetration depth in FeSe1-xSx (x = 0, 0.04, 0.09) and FeTe1-xSex (x = 0.40) single crystals
Published in Phase Transitions, 2019
G. Purohit, A. Pattanaik, P. Nayak
Among the layered superconductors, the “chalcogenides” are one of the notable groups because of the variety of materials and observation of exotic superconductivity. Sulfur (S), selenium (Se) and tellurium (Te) are categorized as chalcogens. One of the notable characteristics of chalcogenides is the crystallization of a simple layered structure with Van der Waals gaps. In such structures, the ions can be easily intercalated in the interlayer sites and dramatically change the physical properties of the chalcogenide layers. The most remarkable layered chalcogenides are the Fe chalcogenides, FeSe and FeTe, which are the simplest Fe-based superconductors. FeSe exhibit superconducting transition temperature Tc around 10 K and shows a marked increase of Tc up to 37 K under high pressure [16]. Superconductivity in layered Fe chalcogenides was initially found in FeSe by Hsu et al. [10]. On the other hand, even though FeTe has also a simple structure (PbO) compared to that of the former one, it is not superconducting rather the physical properties of FeTe are different from those of FeSe [17,18]. It exhibits antiferromagnetic ordering associated with a lattice distortion at 70 K. This family is very interesting because the physical properties markedly change on the substitution of S, Se and Te. A partial substitution of Te by S or Se suppresses the antiferromagnetic ordering and induces superconductivity. Recently, superconductivity above 40 K has been observed in metal or molecule intercalated FeSe [16]. Due to these observations, researchers believe that the study of Fe-based chalcogenide superconductors is important not only for fundamental physics but also for their applications. FeTe possesses excess Fe (7–25%) at the interlayer sites. However, partial Se substitutions suppress the low-temperature structural/magnetic phase transition and reduce excess Fe, thereby inducing superconductivity [11,19,20]. The most mysterious property here is not even the pressure or strain induces to increase the Tc value (the cuprates have already shown the tendency of increased Tc with reduction of the dimensionality), but a giant enhancement of the superconductivity at the Fe/SrTiO3 interface, where SrTiO3 (STO) has nothing in common with magnetic interaction [21]. Although FeSe system possesses many attractive features, the investigation of its physical properties is still in infancy.