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Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
There are two principal methods of CNT functionalization: (i) non-covalent and (ii) covalent. Non-covalent methods include encapsulation, physical and chemical adsorption, and hydrophobic interactions. Covalent immobilization of biomolecules on CNTs is implemented by oxidation of CNTs by sonicating (shearing open by high-frequency sound agitation, usually ultrasound) or refluxing (boiling a liquid in a vessel attached to a condenser so that the vapors continuously condense for re-boiling) in concentrated acid solution which results in the formation of carboxylic acid –COOH groups at the ends and sidewalls of the nanotubes. Carboxylic acid groups on the surfaces of CNTs react with amino functional groups (RNH2 or R2NH, or R3N where R is a carbon-containing substituent) of biological receptors through carbodiimide (or methanediimine, a functional group of the formula RN=C=NR formed by dehydration of urea) coupling, e.g., the attachment of bovine serum albumin (BSA) protein (a serum albumin protein used as a carrier protein and as a stabilizing agent in enzymatic reactions) and glucose oxidase (GOx) enzyme on the sidewalls of CNTs via amide (an organic compound that contains the functional group consisting of an acyl group (R–C=O) linked to a nitrogen atom (N)) linkages.
N-Heterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Yu et al. [82] synthesized several 8-methyleneazaspiro[4.5] trienes by intramolecular electrophilic ipso-cyclization (Scheme 25) [83–84]. The iodoirenium intermediate was generated when I2 coordinated with the carbon-carbon triple bond of the compound. The spiro-compounds were produced by intramolecular Friedel-Crafts cyclization followed by loss of proton. The yield of the product was reduced in the presence of a base (sodium bicarbonate). Moreover, analogous amides with methyl group replaced with an acyl group or hydrogen were found unsuitable as substrates. The reaction also failed with terminal acetylenes. Nevertheless, this reaction has also been studied with some examples of additional substituents (such as chloro, methyl, and bromo) on the phenyl ring [80].
Ignition, extinction and oscillatory phenomena
Published in J. F. Griffiths, J. A. Barnard, Flame and Combustion, 2019
J. F. Griffiths, J. A. Barnard
Equations (10.45)—(10.52) are only a skeleton scheme. If the temperature is sufificently low, methyl radical oxidation can yield methylperoxy radicals and, with acetaldehyde able to provide a very labile H atom from the acyl group, methyl hydroperoxide can be formed (section 7.2). A satisfactory mechanism for acetaldehyde oxidation in the temperature range Ta = 500–750 K then becomes very much more complicated than appears to be necessary at first. The non-isothermal phenomena exhibited by acetaldehyde in a CSTR [194, 195] have been simulated from kinetic schemes which the reactions described here and in section 7.2 [137, 212]. Methane is unable to exhibit similar low temperature/low pressure spontaneous ignition and cool flame characteristics because the abstraction of an H atom from it is so difficult.
Removal of heavy metals and dye from water and wastewater using nanofiltration membranes of polyethersulfone modified with functionalized iron-silica nanoparticles
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
shahab Azizi, Ehsan Jafarbeigi, Farhad Salimi
Rambabu et al. (2019) prepared PES membranes with high molecular weight modified with various loads of calcium chloride by the dry-wet phase inversion method. The results showed that the addition of calcium chloride improves the water permeability and mechanical stability of the composite membranes. Fouling analysis indicated that calcium chloride incorporated membranes possessed better antifouling impact. In a study using the phase inversion technique, Krishnamoorthy and Sagadevan (2015) a series of asymmetric PES Ultrafiltration membranes with iron oxide and polyethylene glycol nano-particles. Thermal analysis indicated the better thermal stability of the blended membranes. Dye rejection studies indicated that the blended membranes almost had the same rejection as that of pure polyethersulfone membranes. Velu et al. (2018) synthesized PES composite membranes with different percentages of manganese carbonate as a surface modifier and PES using the phase inversion method. The blended membranes performance was investigated in terms of antifouling property, dye rejection efficiency, and water permeability. Water uptake experiments approved the enhanced porous nature of the PES/PEG/Manganese carbonate blended membranes over the pristine PES membrane. The findings indicated that the 3 wt% manganese carbonate blended membrane possesses an impressive 98% flux recovery ratio. Karki and Ingole (2022) for the first time prepared thin-layer nano-composite membranes by vapor phase surface polymerization method. After synthesis, they combined TiO2 nano-particles functionalized with a carboxylic acid in the thin-film nano-composite membranes while interfacial polymerization using DETA and TMC containing amine and acyl group monomers, respectively to modify the MS. The results showed that combining nano-materials is effective in increasing the anti-fouling tendency and reducing irreversible fouling. In another similar study, Gohain et al. (2020) showed that functionalized metal-organic frameworks and their composites are found one of the best materials to develop thin-film nano-composite membranes efficiently. An et al. (2017) prepared nano-composite membranes with a thin layer of microporous Engelhard titanosilicate-4 for water vapor separation. The intrinsic properties of Engelhard titanosilicate-4 as well as thin film nano-composite membranes were investigated by FE-SEM, EDX, XRD, AFM, and water CA. The impact of Engelhard titanosilicate-4 concentration on selectivity was checked. Results showed that the maximum selectivity of 346 was gained with 1377 GPU in permeance for the thin film nano-composite membrane (DTE-0.5) with Engelhard titanosilicate-4 concentration of 0.5 wt%.