Distribution of trace elements in flowing surface waters: Effect of seasons and anthropogenic practices in India

This study reports the distribution of Cr, Ni, Cu and Pb in waters, sediments, macrophytes and fish of the Yamuna River’s patch in Delhi (India). This is one of the most polluted stretches of rivers in the world. Water from this river is used fosr irrigation, industrial and domestic purposes, including drinking water. The effects of season and anthropogenic practices were identified. Almost zero dissolved oxygen and high levels of lead and phosphate indicate the polluted state of the aquatic system. The enrichment factors in sediments (with respect to reference site) vary in the range of 0.60–82.9% (Cr), 1.40–90.5% (Ni), 1.00–85.3% (Cu) and 3.80–86.6% (Pb). The toxic effects due to Ni and Pb could frequently be visible in aquatic life as their values fall above the probable effect level (36 mg Kg^?1 for Ni and 91.3 mg Kg^?1 for Pb). The metal contents in the macrophyte (Eichhornia crassipes) and the fish (Oreochromis niloticus) generally increase in the summer season. Cu and Pb accumulate preferentially in E. crassipes. The fish from these waters is unsuitable for human consumption as the levels of Cr, Cu and Pb are above the recommended limits. Significant spatial variations in parameters of water and sediments were confirmed via one-way analysis of variance. The Pearson’s correlation analysis suggests a common source of some of the metals. Principal component analysis highlighted domestic, and industrial waste and coal-fired thermal power plants as the metal sources. This study might act as a benchmark for other investigations focused on similarly affected surface aquatic systems due to agricultural and industrial activities.     

Behaviour of ‘free-standing’ hollow Au nanocages at finite temperatures: a BOMD study

Finite-temperature behaviour of a hollow golden cage (HGC) plays a crucialrole in its potential applications as a catalyst, drug delivery agent, contrasting agent and so on. This physico-chemical property of HGCs is not well understood so far. In that context, Born–Oppenheimer molecular dynamics (BOMD) simulations are performed on a well-known ‘free-standing’ HGC. The cluster considered in this study is the ground state Au₁₈ cluster (a cage with a diameter of about >5.5 Å). The results thus obtained are compared with the BOMD simulation results reported earlier on Au₃₂ icosahedron cage, a conformation with a diameter of nearly. The sphericity of both the clusters is studied using a shape deformation parameter as a function of time and temperature. These results are supplemented by radial distribution function at various temperatures. The observations and analysis of results indicate that, both the clusters retain an HGC conformation from 300 to 400 K, admitting structural fluxionality by the Au₁₈ cluster. Remarkably, the Au₁₈ cluster is able to maintain its hollowness and sphericity up to a high temperature of 1000 K. Underlying structural and electronic properties influencing the individualistic behaviour of cages are highlighted. Composition of the frontier molecular orbitals and the charge distribution play a crucial role in the finite-temperature behaviour of the Au cages. The conclusions are supplemented by supporting calculations on another degenerate ground state Au₁₈ hollow cage and a well-known pyramidal Au₁₈ cage at 300 and 400 K.     

SYNTHESIS OF SOME SULFUR-CONTAINING SPIROINDOLE DERIVATIVES

Abstract

The synthesis of some new sulfur-containing spiroindole derivatives is reported. Fluorinated 3′-aryl-2′-phenylimino-spiro[3H-indole-3,6′[4,5′-pyrazolin][4,3-d]thiazolo]2(1H)-ones were prepared by the reaction of 5-(2-oxo-3-indolinylidene)-3-aryl-2-phenylimino-4-thiazolidinones with hydrazine hydrate. The compounds have been characterized on the basis of elemental and spectral studies.     

Synthesis,Characterization, and Biological Screening of Some Novel Thiazolidin-4-One and α-Aminophosphonate Derivatives

Abstract

Synthesis of some new functionalized thiazolidin-4-ones and α-amino phosphonate derivatives has been reported. The imines were synthesized from the reaction of various substituted anilines with 1-phenyl-3-(pyridine-4-yl)-1H-pyrazole-4-carbaldehyde in ethanol at reflux condition. The corresponding thiazolidin-4-ones and α-aminophosphonates were prepared by reaction of imines with mercaptoacetic acid and triethyl phosphite, respectively. The structures of the newly synthesized compounds were confirmed by IR, ¹H NMR, and mass spectral data and were evaluated for their antimicrobial activities.

GRAPHICAL ABSTRACT      

p-Hydroxybenzoic Acid-Urea-Formaldehyde Copolymers and Their Ion-Exchange Properties

Copolymers (PUF) were synthesized by the condensation of p-hydroxybenzoic acid (P), urea (U), and formaldehyde (F), in the presence of different acidic catalysts and using varied molar ratios of reacting monomers. One of the copolymers having the highest molecular weight was fractionated. Copolymer compositions have been determined on the basis of their elemental analysis and conductometric titrations in the nonaqueous phase. Molecular weights (M_n) have been estimated by VPO. Copolymer prepared by using the stoichiometric properties of the monomers and HCI as catalyst furnished the highest molecular weight (M_n). The viscosity measurements carried out in DMF indicate normal behavior. TGA and DSC data were analyzed to compare the relative thermal stability and estimate the characteristic parameters. IR spectra were studied to elucidate the structure. Chelation ion-exchange properties have also been studied employing the batch equilibration method. The order of selectivity of metal ions by the copolymers is UO₂ ²⁺ > Fe³⁺ >Cu²⁺ > Co²⁺.     

Selected parameters leading to an optimized DSSC performance

Dye Sensitized Solar Cells (DSSC), the third generation of photovoltaic devices, can be considered as most promising among renewable energy sources. Although DSSCs are devices very easy to fabricate, there is a large number of design parameters upon which their performance depends. In this review paper a lay out is given of the various parameters at which research groups focus aiming towards optimum performance of the DSSCs.     

Development of Hydroprocessing Route to Transportation Fuels from Non-Edible Plant-Oils

Catalysts with tunable porosity, crystallinity and acidity can selectively produce aviation fuels and road transportation fuels via hydroprocessing of non-edible oils. Here we discuss several catalyst supports—mesoporous alumina, silica–alumina and hierarchical mesoporous zeolites, developed and used as support for hydroprocessing catalysts (Ni–Mo, Co–Mo, Ni–W), for the selective production of transportation fuels. These developed catalysts were used for the hydroconversion of waste cooking-oil, jatropha-oil, algal-oil and their mixtures with petroleum refinery oils. The physicochemical properties of the catalyst were tuned for optimal performance on the basis of evaluation results on high pressure fixed bed microreactors and pilot scale reactors. These studies targeted the production of transportation fuels (gasoline, kerosene and diesel) by hydroprocessing (hydrotreating or hydrocracking) renewable feed stocks or co-processing with fossil based oils. Modelling and process optimization studies for prediction of kinetic rate parameters and to know the reaction pathways for the conversion of these feed stocks to various range of hydrocarbon fuels, were also carried out. These studies provided the vital information that the reaction pathways were temperature dependent.     

Synthesis of Bioactive Pyrethroid, 3-Phenoxybenzyl 1R-trans-2, 2-Dimethyl-3-(2-chloro-1-propenyl) Cyclopropanecarboxylate

The title compound 1 has been prepared from (+)-3-carene (2) and found to have the same order of activity as its IR-cis isomer 3 reported by us earlier¹ The key intermediate methyl IR-trans-2, 2-dimethyl-3-(2-oxopropyl)cyclopropanecarboxylate (4) has been characterised.     

New Method for the Synthesis of Benzyl Alkyl Ethers Mediated by FeSO4

The synthesis of benzyl alkyl ethers from benzyl bromides and alcohols using FeSO₄ as a recoverable and reusable mediator has been described without use of base and cosolvent under mild conditions.