Micellization and interfacial behavior of binary and ternary mixtures of model cationic and nonionic surfactants in aqueous NaCl medium

Mixed micelle formation and interfacial properties of aqueous binary and ternary combinations of hexadecyltrimethylammonium bromide (C(16)Br), hexadecylbenzyldimethylammonium chloride (C(16)BzCl) and polyoxyethylene (20) cetyl ether (Brij58) at 25 degrees C in 30 mM aqueous NaCl have been studied in detail employing tensiometric and fluorimetric techniques. The micellar and adsorption characteristics like composition, activity coefficients, mutual interaction parameters and free energy of micellization have been estimated using the theoretical approaches of Clint, Rosen, Rubingh, Blankschtein et al., Rubingh-Holland and Maeda. A comprehensive account of the comparative performance of these models on the selected cationic-cationic-nonionic surfactant mixtures at constant ionic strength has been presented. The Blankschtein model predicted lower synergism than from Rubingh's method because it neglects the contribution due to steric interaction between surfactant head groups of different sizes and charges. Free energy of micellization calculated using Maeda's approach, which employs interaction parameter and micellar mole fraction from Rubingh's model as inputs, shows good correlation with that calculated from commonly used phase separation model. The present study also reveals that the modified Rubingh-Holland method along with the Rosen's model can be applied to analyze the interfacial characteristics of ternary surfactant mixtures with a fair degree of success thereby widening the domain of applicability of this model.     

The Development of Highly Fluorescent Hemicyanine and Dicyanoisophorone Dyes for Applications in Dye-Sensitized Solar Cells

Journal of Fluorescence - Ruthenium-based metal complex dyes have been employed extensively in dye-sensitized solar cells (DSSCs) as photosensitizers, but the cost and toxicity of metal complexes...     

An Overview of the Genetics of Plant Response to Salt Stress: Present Status and the Way Forward

Salinity is one of the major threats faced by the modern agriculture today. It causes multidimensional effects on plants. These effects depend upon the plant growth stage, intensity, and duration of the stress. All these lead to stunted growth and reduced yield, ultimately inducing economic loss to the farming community in particular and to the country in general. The soil conditions of agricultural land are deteriorating at an alarming rate. Plants assess the stress conditions, transmit the specific stress signals, and then initiate the response against that stress. A more complete understanding of plant response mechanisms and their practical incorporation in crop improvement is an essential step towards achieving the goal of sustainable agricultural development. Literature survey shows that investigations of plant stresses response mechanism are the focus area of research for plant scientists. Although these efforts lead to reveal different plant response mechanisms against salt stress, yet many questions still need to be answered to get a clear picture of plant strategy to cope with salt stress. Moreover, these studies have indicated the presence of a complicated network of different integrated pathways. In order to work in a progressive way, a review of current knowledge is critical. Therefore, this review aims to provide an overview of our understanding of plant response to salt stress and to indicate some important yet unexplored dynamics to improve our knowledge that could ultimately lead towards crop improvement.     

Numerical spectral examination of EMHD mixed convective flow of second-grade nanofluid towards a vertical Riga plate using an advanced version of the revised Buongiorno’s nanofluid model

Journal of Thermal Analysis and Calorimetry - Present communication aims to determine the impact of Cattaneo–Christov model and convective boundary on second-grade nanofluid flow alongside a...     

Effect of Different Counterions of the Manganese Salt as Catalyst on the Kinetics of Resorcinol‐Based Belousov–Zhabotinsky Reaction

Kinetic studies on the Belousov–Zhabotinsky (BZ) system with various metal ions as catalysts have been carried out for a long time, but the effect of counteranions associated with the metal ion solution used as the catalyst in the BZ reaction has not been explored. Thus, we have chosen some metal salts as catalysts having the metal ion (Mnⁿ⁺) but with various anions to study the role of different anionic moieties of catalyst on the oscillatory behavior of the resorcinol‐based BZ reaction system. It is found that organic‐type anionic moieties marginalize the role of organic substrates in the reaction system. On the other hand, the inorganic counterions of the catalyst show salting out effects, thereby increasing the ionic strength, which affects the mobility (diffusion) of the ions in our system performed under batch conditions.     

Time-dependent three-dimensional flow and mass transfer of elastico-viscous fluid over unsteady stretching sheet

This article studies the three-dimensional boundary layer flow of an elasticoviscous luid over a stretching surface. Velocity of the stretching sheet is assumed to be ime-dependent. Effect of mass transfer with higher order chemical reaction is further onsidered. Computations are made by the homptopy analysis method (HAM). Convergence f the obtained series solutions is explicitly analyzed. Variations of embedding arameters on the velocity and concentration are graphically discussed. Numerical computations f surface mass transfer are reported. Comparison of the present results with he numerical solutions is also given.     

Effect of self‐assemblies of various surfactants in their single and mixed states on the BZ oscillatory reaction

Micelles of different surfactants are well known to affect chemical equilibria and reactivities by selectively sequestering the reagent substrates through electrostatic and hydrophobic interactions. In this article, the effects of micelles of various surfactants on different parameters of the Ce(IV)‐catalyzed Belousov–Zhabotinsky (BZ) oscillatory reaction at 35°C in nonstirred closed conditions are studied by employing spectrophotometry and tensiometry. Surfactants used in this study are the cationics hexadecyltrimethylammonium bromide (CTAB) and pentamethylene‐1,5‐bis(N‐hexadecyl‐N,N‐dimethylammonium)bromide gemini (Gemini), anionic sodium dodecylbenzene sulfonate (SDBS), and nonionic Brij58, whereas the binary surfactant systems used are cationic–nonionic CTAB+Brij58 and anionic–nonionic SDBS+Brij58. The results revealed that the induction period shows a definite variation with increasing concentration of different surfactants above their critical micelle concentration (cmc). The amplitudes of oscillation and absorbance maxima and minima are enhanced in the presence of micelles of CTAB and Gemini surfactants, whereas micelles of SDBS and Brij58 have almost no effect on the nature of the oscillations. However, mixed micelles of CTAB+Brij58 and SDBS+Brij58 binary mixtures show a quite different effect on the overall behavior of the oscillations. The enhanced effect of CTAB and Gemini surfactants on the overall nature of oscillations has been attributed to the positive charge on the surface of their micelles and to some extent on the presence of nitrogen in their head group. The effect of mixed binary micelles may be attributed to their synergistic nature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 659–668, 2010     

Chemical synthesis of deuterium-labeled and unlabeled very long chain polyunsaturated fatty acids

First syntheses of a deuterium-labeled very long C34-containing polyunsaturated fatty acid, 34:5n5, and three other unlabeled very long chain C30-32 containing polyunsaturated fatty acids are reported. These syntheses were achieved by coupling chemically modified C22- and C20-containing polyunsaturated fatty acids with carbanions derived from arylalkyl sulfones, followed by sodium amalgam-mediated desulfonylation.