Recent advances in application of the graphene-based membrane for water purification

Graphene is an atomic layer thick carbon-based material with unique two-dimensional architecture and extraordinary physiochemical, optical, electrical, and mechanical properties. Graphene and its derivatives show significant promises for the development of nanoporous ultrathin filtration membranes capable of molecular separation properties. Graphene-based nanofiltration membranes featuring distinct laminar structures can offer various novel mass-transport phenomena for purifying water, energy storage and separation, gas separation, and proton conductors. The latest developments in water purification techniques through graphene-based membranes including engineering, design, and fabrication of diverse graphene, graphene-oxide, and graphene-composite membranes are provided here in relation to their application paradigm for purifying water. The critical views on pollutant removal mechanisms for water purification along with optimization measures are specially highlighted. In addition, the challenges, shortcomings, and future prospects are pointed out. The green and large-scale synthesis technology of graphene coupling with advanced membrane fabrication techniques can promote these state-of-the-art nanofiltration membranes for a wide range of applications.     

Slow magnetohydrodynamic flow past a circular cylinder

Oseen’ approximations are used to study the slow motion of a viscous, incompressible, electrically conducting fluid past a circular cylinder in the presence of a uniform aligned magnetic field. Using series truncation method, the analytical solutions for the first three terms in the Fourier sine series expansion of the stream function are obtained. Numerical values of the tangential drag for different values of magnetic interaction parameter and viscous Reynolds number are calculated.     

Palladium-catalyzed regioselective synthesis of benzosultams from functionalized ynamides and benzotriazoles/tetrazoles

Palladium-catalyzed highly regioselective synthesis of benzotriazole appended benzosultams by the tandem-cyclization of functionalized ynamides with benzotriazoles has been accomplished. This transformation involves the formation of both CN and CC bonds in a single step. Donor solvents appear to enhance the yields of the products. The methodology is also applicable for the generation of triazole/tetrazole appended benzosultams.     

Speciation and Multinuclear NMR Spectroscopic Studies of Di- and Trimethyltin(IV) Moieties with MESNA in Aqueous Medium

The interaction of Me₂Sn(IV)²⁺ and Me₃Sn(IV)⁺ with a prodrug, sodium 2-mercaptoethane sulfonate (HSCH₂CH₂SO₃Na, MESNA) abbreviated as (HL), has been studied potentiometrically in aqueous solution (I = 0.1 mol·L^?1 KNO₃, 298 K). The concentration distribution of various species formed in the solution was studied with changes in pH (~3–11). A strong coordination of MESNA with metal through the S atom of thiol group has been found. In the Me₂Sn(IV)–HL system, the species [Me₂Sn(L)]⁺ (53.1–75.6%) is predominant at acidic pH (3.73 ± 0.02) and the species [Me₂Sn(L)₂OH]^? (29.4–38.5%) is predominant at basic pH (10.32 ± 0.08). In contrast, for the Me₃Sn(IV)⁺ system, [Me₃SnL] (37.0–57.4%) is the major species at pH 7.65 ± 0.03 and [Me₃Sn(OH)] (49.9–67.2%) and [Me₃Sn(L)(OH)]^? (30.2–46.5%) are the major species at pH 11.05 ± 0.01. However, at physiological pH (7.01 ± 0.32), in both (1:1) and (1:2) Me₂Sn(IV)–HL systems, the species [Me₂Sn(L)(OH)] (67.2–89.9%) is predominant, whereas for Me₃Sn(IV)–HL (1:1) and (1:2) systems, [Me₃Sn(OH)] (53.5%) and [Me₃SnL] (56.8%) are the respective predominant species. In order to characterize the possible geometry of the proposed complex species, multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR studies were carried out at different pHs. No polymeric species were detected in the experimental pH range.     

Standard molar Gibbs free energy of formation of Pb5CrO8(s), Pb2CrO5(s), and PbCrO4(s)

Standard molar Gibbs free energy of formation of ternary oxides Pb₅CrO₈(s), Pb₂CrO₅(s), and PbCrO₄(s) were determined by measuring equilibrium oxygen partial pressures over relevant phase fields using manometry and solid oxide electrolyte based emf methods and are given by: ${\mathrm{\Delta }}_f{G}_m^{°}{\text{Pb}}_5{\text{CrO}}_8(s)\pm 0.55/(\text{kJ}·{\text{mol}}^{-1})=-1809.4+0.6845(T/\text{K})(837\le T/\text{K}\le 1008)\text{,}$${\mathrm{\Delta }}_f{G}_m^{°}{\text{Pb}}_2{\text{CrO}}_5(\text{s})\pm 0.30/(\text{kJ}·{\text{mol}}^{-1})=-1161.3+0.4059(T/\text{K})(859\le T/\text{K}\le 1021)\text{,}$${\mathrm{\Delta }}_{\text{f}}{G}_m^{°}{\text{PbCrO}}_4(\text{s})\pm 0.17/(\text{kJ}·{\text{mol}}^{-1})=-909.8+0.3111(T/\text{K})(863\le T/\text{K}\le 1093)\text{,}$     

Nanofibrous polyaniline thin film prepared by plasma‐induced polymerization technique for detection of NO2 gas

A nanofibrous polyaniline (PANI) thin film was fabricated using plasma‐induced polymerization method and explored its application in the fabrication of NO₂ gas sensor. The effects of substrate position, pressure, and the number of plasma pulses on the PANI film growth rate were monitored and an optimum condition for the PANI thin film preparation was established. The resulting PANI film was characterized with UV–visible spectrophotometer, FTIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The PANI thin film possessed nanofibers with a diameter ranging from 15 to 20 nm. The NO₂ gas sensing behavior was studied by measuring the change in electrical conductivity of PANI film with respect to NO₂ gas concentration and exposure time. The optimized sensor exhibited a sensitivity factor of 206 with a response time of 23 sec. The NO₂ gas sensor using nanofibrous PANI thin film as sensing probe showed a linear current response to the NO₂ gas concentration in the range of 10–100 ppm. Copyright © 2009 John Wiley & Sons, Ltd.