@article { ISI:000256743300032, title = {Insight into the micellization of dodecyldimethylethylammonium bromide (DDAB) in the presence of bovine serum albumin (BSA)}, journal = {Journal of Colloid and Interface Science}, volume = {323}, number = {2}, year = {2008}, month = {JUL}, pages = {426-434}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

in this work, we report the effect of concentration of bovine serum albumin (BSA) on the micellization of a cationic surfactant, doclecyldimethylethylammonium bromide (DDAB). Several samples covering a wide range of concentrations of protein and surfactant have been investigated. The interactions between the moieties are investigated by measuring fluorescence quenching of BSA molecules. The aggregation number of DDAB micelles is found to be small in the presence of BSA. The formation of DDAB-BSA complex is confirmed by FTIR. Absorbance spectroscopy indicates that at higher concentration, the conformational stability of BSA in DDAB is higher. The viscosity data for protein-surfactant systems confirm conformational changes in protein chains induced by the surfactant. The cmc values for DDAB increase with increasing concentration of BSA. At higher temperatures the micellization-complexation becomes enthalpy-dominated. (c) 2008 Elsevier Inc. All rights reserved.

}, keywords = {Aggregation number, BSA, conductivity, conformational stability, DDAB, FFIR, fluorescence, UV-visible, viscosity}, issn = {0021-9797}, doi = {10.1016/j.jcis.2008.04.026}, author = {Mehta, S. K. and Bhawna and Bhasin, K. K. and Kumar, Anil} } @article { ISI:000264326100007, title = {Dramatic change in viscosities of pure ionic liquids upon addition of molecular solvents}, journal = {Journal of Solution Chemistry}, volume = {38}, number = {5}, year = {2009}, month = {MAY}, pages = {589-600}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Viscosities of binary mixtures of pyridinium based ionic liquids (1-butyl pyridinium tetrafluoroborate, [BP][BF(4)], 1-butyl 3-methyl pyridinium tetrafluoroborate [3-MBP][BF(4)], 1-butyl 4-methyl pyridinium tetrafluoroborate, [4-MBP][BF(4)]), and phosphonium based ionic liquids, (tetrabutyl phosphonium alaninate, [TBP][Ala]; tetrabutyl phosphonium valinate, [TBP][Val]) with the molecular solvents, water, methanol and dichloromethane, have been measured at 298.15 K. A Brookfield ultra-rheometer was employed to measure the reported viscosities. The drop in viscosity in the close vicinity of pure ionic liquid is more prominent in polar solvents like water compared to less polar solvents. The temperature dependence of this observation was also studied for binary mixtures of [4-MBP][BF(4)] with water in range of 298.15-323.15 K. The Vogel-Fulcher-Tamman (VFT) equation was employed to investigate the temperature dependence of the viscosities of pure pyridinium-based ionic liquids in the temperature range from 298.15-323.15 K.

}, keywords = {ionic liquids, Molecular solvents, VFT equations, viscosity}, issn = {0095-9782}, doi = {10.1007/s10953-009-9390-7}, author = {Khupse, Nageshwar D. and Kumar, Anil} } @article { ISI:000268923200029, title = {Solubilization and conformational behavior of zein in aqueous solution of dodecyldimethylethylammonium bromide (DDAB)}, journal = {Colloids and Surfaces A-Physicochemical and Engineering Aspects}, volume = {346}, number = {1-3}, year = {2009}, month = {AUG}, pages = {195-201}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The solubilization and conformational behavior of Zein in the presence of cationic surfactant, dodecyldimethylethylammonium bromide (DDAB) have been studied. The colloidal properties of DDAB in the absence and presence of Zein have also been investigated using physico-chemical and spectroscopy methods. The surfactant appears to bind to Zein at concentrations below the critical micelle concentration (cmc) and the binding becomes weaker at concentrations above the cmc. The interaction between DDAB and Zein depends on the chemical structure and molecular parameters (conformation, molar mass, charge) of the protein. The schematic sketches of the molecular mechanisms of the complex formation between like-charged proteins and surfactants have been proposed. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Absorbance spectroscopy, Aggregation number, conductivity, DDAB, FT-IR, Surface tension, viscosity, Zein}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2009.06.016}, author = {Mehta, S. K. and Bhawna and Bhasin, K. K. and Kumar, Anil} } @article { ISI:000279017900002, title = {Ionic liquids: new materials with wide applications}, journal = {Indian Journal of Chemistry Section A-Inorganic Bio-Inorganic Physical Theoretical \& Analytical Chemistry}, volume = {49}, number = {5-6, SI}, year = {2010}, month = {MAY}, pages = {635-648}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

Ionic liquids have emerged as possible substitutes for volatile organic solvents and have found many applications in a variety of research areas. In this review, an effort has been made to discuss the special properties of ionic liquids that render these unique solvent media useful in chemical transformations, electrochemical applications, extractions, etc.

}, keywords = {Chemical processes, Electrochemical devices, ionic liquids, Physicochemical properties, Solvent properties, viscosity}, issn = {0376-4710}, author = {Khupse, Nageshwar D. and Kumar, Anil} } @article { ISI:000275937400001, title = {Solvent-induced viscosity changes in ionic liquids - a review}, journal = {Proceedings of the National Academy of Sciences India Section A-Physical Sciences}, volume = {80}, number = {1}, year = {2010}, month = {JAN}, pages = {1-12}, publisher = {NATL ACAD SCIENCES INDIA}, address = {5 LAJPATRAI RD, ALLAHABAD 211002, INDIA}, abstract = {

The high viscosity of several ionic liquids is an undesirable property for their applications in a variety of chemical reactions and electrochemical devices. Addition of a solvent in an ionic liquid is known to reduce its high viscosity to a great extent. In this review, an attempt has been made to examine the published data on the reduction in viscosities of many ionic liquids upon the addition of molecular solvents, including water. A tentative description has been provided for the drop in viscosities under these conditions. Analysis of the viscosity data with the help of empirical equations has been summarized. This critical review also outlines the future outlook of the required studies that might be useful to those who are interested in using ionic liquids for a variety of applications.

}, keywords = {ionic liquids, solvent, viscosity}, issn = {0369-8203}, author = {Khupse, Nageshwar D. and Kumar, Anil} } @article { ISI:000279017900010, title = {Temperature dependent viscosity of mixtures of ionic liquids at different compositions}, journal = {Indian Journal of Chemistry Section A-Inorganic Bio-Inorganic Physical Theoretical \& Analytical Chemistry}, volume = {49}, number = {5-6, SI}, year = {2010}, month = {MAY}, pages = {727-730}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

This work presents experimental investigations of viscosities of the mixtures of ionic liquids, viz., [bmim][BF(4)] + [bmim][PF(6)] and [hmim][BF(4)] + [hmim][PF(6)] at different temperatures. The temperature dependence of viscosities of these mixtures has been analysed in the light of Vogel-Fulcher-Tammann (VFT) equation with excellent accuracy. The viscosities of the mixtures have been analysed using a simple mixing rule.

}, keywords = {ionic liquids, viscosity}, issn = {0376-4710}, author = {Khupse, Nageshwar D. and Kurolikar, Shabana R. and Kumar, Anil} } @article { ISI:000292011000004, title = {Eutectic mixture-directed kinetics of Diels-Alder reaction}, journal = {Indian Journal of Chemistry Section A-Inorganic Bio-Inorganic Physical Theoretical \& Analytical Chemistry}, volume = {50}, number = {6}, year = {2011}, month = {JUN}, pages = {788-792}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

In the search for environmentally benign solvent media, a new class of solvents composed of mixtures of carbohydrates with urea or methylated urea has been noted to be effective in enhancing the reaction rates of a bimolecular organic reaction like the Diels-Alder reaction of cyclopentadiene with methyl acrylate. The viscosity of these media appears to be an important parameter in controlling the second order kinetics.

}, keywords = {carbohydrates, Cycloaddition, Diels-Alder reaction, Dimethylurea, kinetics, Reaction rates, solvent effects, Urea, viscosity}, issn = {0376-4710}, author = {Nagare, Amit S. and Kumar, Anil} } @article { ISI:000307351500021, title = {High viscosity of ionic liquids causes rate retardation of Diels-Alder reactions}, journal = {Science China-Chemistry}, volume = {55}, number = {8, SI}, year = {2012}, month = {AUG}, pages = {1633-1637}, publisher = {SCIENCE PRESS}, address = {16 DONGHUANGCHENGGEN NORTH ST, BEIJING 100717, PEOPLES R CHINA}, abstract = {

Second order rate constants, k (2) have been determined for three bi-molecular Diels-Alder reactions to demonstrate that the high viscosity of ionic liquids can be a detrimental property in carrying out Diels-Alder reactions, if ionic liquids are employed as solvent media. It is possible to enhance the reaction rates of the reaction if a co-solvent is mixed in pure ionic liquid used as a solvent.

}, keywords = {Diels-Alder reactions, ionic liquids, kinetics, viscosity}, issn = {1674-7291}, doi = {10.1007/s11426-012-4684-9}, author = {Kumar, Anil and Pawar, Sanjay S.} } @article { ISI:000327418000001, title = {Unusual salting effects in ionic liquid solutions}, journal = {Indian Journal of Chemistry Section A-Inorganic Bio-Inorganic Physical Theoretical \& Analytical Chemistry}, volume = {52}, number = {11}, year = {2013}, month = {NOV}, pages = {1377-1382}, publisher = {NATL INST SCIENCE COMMUNICATION-NISCAIR}, address = {DR K S KRISHNAN MARG, PUSA CAMPUS, NEW DELHI 110 012, INDIA}, abstract = {

Unusual salting effects of salting-out agents like LiCl and NaCl and salting-in agents like LiClO4 and NaClO4 in ionic liquid solutions are reported. It is observed that the salting behavior in water can be altered in the presence of ionic liquids. It is demonstrated that the salting-in agents in the presence of the ionic liquids with higher alkyl chain can display unusual fall and rise in the viscosity of the systems. On the other hand, no change in the behavior of the salting-out agents is noted in these ionic liquids. A tentative explanation is proposed for the observed viscosity data in these systems.

}, keywords = {Cationic ring, ionic liquids, Salting effects, viscosity}, issn = {0376-4710}, author = {Nanda, Raju and Kumar, Anil} } @article { ISI:000362834600003, title = {Experimental signature of microheterogeneity in ionic liquid-H2O systems and their perturbation by adding Li+ salts: a pulsed gradient spin-echo NMR approach}, journal = {Chemphyschem}, volume = {16}, number = {14}, year = {2015}, month = {OCT}, pages = {2936-2941}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Distinct microheterogeneity has been observed in the [OMIM]Br-H2O system, which is interestingly perturbed by the addition of Li+ salts, indicating unusual diffusivity of [OMIM]Br and H2O molecules. However, the diffusional dynamics of water clusters show contrasting salting behavior at higher concentrations of Li+ salts, following the classical salting phenomenon in lower amounts. In contrast, the existing microheterogeneity in the [BMIM]Br-H2O system is weak enough to show any perturbation caused by the Li+ salts on the NMR time scale.

}, keywords = {ionic liquids, lithium, microheterogeneity, salt effect, viscosity}, issn = {1439-4235}, doi = {10.1002/cphc.201500503}, author = {Nanda, Raju and Rajamohanan, P. R. and Kumar, Anil} } @article { ISI:000353289100023, title = {Interesting viscosity changes in the aqueous urea-ionic liquid system: effect of alkyl chain length attached to the cationic ring of an ionic liquid}, journal = {Journal of Solution Chemistry}, volume = {44}, number = {3-4, SI}, year = {2015}, month = {APR}, pages = {742-753}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

In the present article, we demonstrate the effect of urea on the structure of the ionic liquids in their aqueous solutions through viscometric methods. We unravel the structure altering effect of urea in its aqueous solutions of ionic liquids possessing higher alkyl chains. The finding is an attempt to discern the anomalous behavior of urea as shown in the past with the help of many techniques. Interestingly, in the aqueous solutions of the imidazolium based ionic liquids having substitution of -C4H9 and -C6H13 groups on the imidazolium ring, urea exhibits kosmotropic behavior. Further increase in the substituted alkyl group such as -C8H17 alters the urea behavior to be chaotropic.

}, keywords = {Alkyl chain length, ionic liquids, Structure-breaker, Structure-maker, Urea, viscosity}, issn = {0095-9782}, doi = {10.1007/s10953-015-0320-6}, author = {Nanda, Raju and Rai, Gitanjali and Kumar, Anil} } @article { ISI:000365445500001, title = {Water-promoted diels-alder reaction in quaternary ammonium salts}, journal = {Journal of Physical Organic Chemistry}, volume = {28}, number = {11}, year = {2015}, month = {NOV}, pages = {665-673}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

{Prevailing classification of salts based on their effect in solubility and stability of proteins in aqueous solution predicts that tetraalkylammonium salts, guanidinium chloride (GnCl), LiClO4 act as salting-in (S/I) and LiCl, NaCl act as salting-out (S/O) in aqueous conditions. In the same context the behaviour of GnCl, LiClO4 and LiCl are contradictory in polar solvents like ethylene glycol and formamide. In these solvents, expected salt effect shows just opposite nature from their usual expectation. However, in the aqueous solution salts like tetraalkylammonium halide (R4NX

}, keywords = {Delta G(solvation), Diels-Alder reaction, k(s), kinetic study, solubility, tetraalkylammonium salts, viscosity}, issn = {0894-3230}, doi = {10.1002/poc.3469}, author = {Nagare, Amit S. and Manna, Arpan and Sonawane, Pramod D. and Kumar, Anil} }