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Merits of Selecting Metal-Organic Frameworks as Sensors
Published in Ram K. Gupta, Tahir Rasheed, Tuan Anh Nguyen, Muhammad Bilal, Metal-Organic Frameworks-Based Hybrid Materials for Environmental Sensing and Monitoring, 2022
Harmeet Kaur, Amit L Sharma, Akash Deep
Although MOFs are inherently insulating, several approaches have been developed to introduce conductivity in these materials. The commonly used strategies include: i) Doping with conductive guest molecules, and ii) Composite formation with conducting polymers. The doping of MOFs with conductive guest molecules enables their interactions with open metal sites in the MOFs, resulting in the creation of conductive pathways for electron transfer. Dopants employed are generally small-sized molecules that form π-bonding with linkers and result in increased electronic conductivity through the redox process. During composite formation, the combination of MOFs with conductive molecules like graphene, polyaniline, and the like, result in synergistic interactions integrating the redox properties of MOFs with the electron transfer properties of the conductive molecules. The charge transport in MOFs is governed by spatial or energetic orbital overlapping and an increase in this overlapping improves the overall charge mobility. The electroactive MOFs are increasingly being used in electrochemical sensing platforms due to the dual attributes of enhanced intrinsic selectivity and augmented electrochemical activity especially for applicability in pollutant and molecular sensing [21, 22]. Besides enhanced electrical conductivity MOFs, low conductivity MOFs have also been employed in active layers for impedance or capacitive sensing, for example, a MOF-based capacitive sensor on an interdigitated electrode for detection of hydrogen disulfide (H2S) [23].
Metabolism and Toxicity of Occupational Neurotoxicants: Genetic, Physiological, and Environmental Determinants
Published in Lucio G. Costa, Luigi Manzo, Occupatinal Neurotoxicology, 2020
Stefano M. Candura, Luigi Manzo, Anna F. Castoldi, Lucio G. Costa
Although the exact mechanism(s) by which carbon disulfide (CS2) causes peripheral neuropathy and other neurotoxic effects (retinopathy, hearing loss to high-frequency tones) are yet to be determined, it is believed that CS2 toxicity is, at least in part, mediated by metabolic activation.15 Following exposure to CS2, very little of the parent compound is excreted unchanged. Most of the absorbed dose is eliminated as sulfur-containing urinary metabolites, some of which are shown in Figure 3. P450-mediated oxidative desulfuration of CS2 yields elemental sulfur and carbonyl sulfide, which in turn is hydrated to monothiocarbonic acid (Figure 3). The latter decomposes to hydrogen disulfide (H2S) and C02. Additional H2S is produced by sulfur reduction in the strong reducing environment of the cell. Dithiocarbamates formed as metabolites of CS2 may contribute to neurotoxicity, possibly by interfering with distribution of essential metals, such as copper and zinc.15,16
Protein Adhesives
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
Charles R. Frihart, Linda F. Lorenz
The association of proteins becomes very important during the aqueous gelation process in water, which links the proteins together to form a large macromolecular structure [31]. Heat gelation is very important in the food industry and has been well studied. Gelation is probably driven more by hydrophobic interactions, because stable polar interactions are less likely to form in an aqueous environment. A useful model for globular proteins is a string of beads with branch points to give a three-dimensional gel that traps a lot of water [29,31]. These larger aggregates probably provide the cohesive strength for protein adhesives. Hydrogen, disulfide, and acid–base bonds may also provide additional strength between the individual protein molecules for the adhesive bond strength.
Physicochemical properties of high-content rubber modified bio-asphalt using molecular simulation
Published in Petroleum Science and Technology, 2023
Asphalt is a kind of complex compound and the three components model is usually used to describe the molecular structure of asphalt in molecular simulations. The three components (the molar of asphaltene: 1,7-dimethylnaphthalene: n-C22 is 5:27:41) of asphalt molecular model was proposed and used widely (Zhou et al. 2020a) and it is shown in Figure 2a. Bio-oil is derived from biomass pyrolysis and its molecular model can be used single component molecular model (Yang et al. 2018), as shown in Figure 2b. Waste rubber powder consists of the sulfur cross-linked natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) (Jiao, Pan, and Che 2022). Sulfur and hydrogen disulfide are used as the vulcanizing agent during vulcanization process for rubber. The detailed molecular model of waste rubber powder is shown in Figure 2c. The waste rubber molecular model consists of 5 NR molecule, 3 SBR molecule, and 2 BR molecule. In order to modeling purposes, the degree of polymerization of NR, SBR, and BR was set as 10 because the systems energy is stable when the the degree of polymerization is 10. The contents of waste tire rubber in HRMBA are 20, 25, 30, 35, and 40%, respectively, and the corresponding molecular numbers are 1, 2, 3, 4, and 5, respectively. The bio-oil contents is constant and 20%. The molecule bulk models of HRMBA with different rubber contents are seen in Figure 2d. The molecular structures of HRMA and bio-oil have been used by many researchers and their reliability has been also verified (Zhou and Adhikari 2019; Zhou et al. 2020a).
Prediction of product gas composition from biomass gasification by the method of Gibbs free energy minimization
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Ruta Khonde, Shubham Hedaoo, Samir Deshmukh
In the MS-Excel worksheet, carbon dioxide, carbon monoxide, hydrogen, methane, hydrogen disulfide, nitrogen, water and tar (C10H8) components are considered as N1, N2, N3, N4, N5, N6, N7, and N8, respectively. In the incomplete carbon conversion, it is assumed that some carbon is present in the ash and this carbon component is taken as N9; whereas in the complete carbon conversion, it is assumed that there is no carbon present in the ash, so N9 is not considered. The composition of these components is predicted with two situations, i.e. conversion of carbon (complete or incomplete) and variation in temperature (600°C, 700°C, 800°C, and 900°C). The thermodynamic coefficients of each gaseous component and each element are available for the operating temperature <1000 K and for >1000 K in NASA technical memorandum 4513 (McBride, Gordon, and Reno 1993) given in Tables 3 and 4. Using above algorithm, the product gas composition in volume% are predicted at different operating temperatures and compared with the literature (Guan et al. 2009). For solving Equation (5) and (6), a modified form of equation (3) is used to avoid Solver errors by putting n = en’. The predicted values are finally validated by comparing with literature data.
Shift of the H2S paradigm
Published in Journal of Sulfur Chemistry, 2022
The first ‘swallow' – a harbinger of the inevitable contradiction, was the detection of H2S2 (disulfane, hydrogen disulfide) as a product of H2S dimerization on sulfide catalysts, resulted in desorption of hydrogen in the gas phase at room temperature [11,12].