... JUNE 1995 Volumetric and transport properties in microemulsions and the point of view of perc... more ... JUNE 1995 Volumetric and transport properties in microemulsions and the point of view of percolation theory S. K. Mehta* and Kiran Bala Department of Chemistry, Panjah University, Chandigarh ... Con-Page 3. S734 S. K. MEHTA AND KIRAN BALA S1 18— lOggp & ...
Ultrasonic speed u and dilatometric measurements of excess volume VE have been carried out for mi... more Ultrasonic speed u and dilatometric measurements of excess volume VE have been carried out for mixtures of pyrrolidin-2-one (PY) with acetonitrile (ACN), propionitrile (PN), butyronitrile (BN), valeronitrile (VN), acrylonitrile (ACRN) and benzonitrile (BEN) at 303.15K over the entire composition range. All the mixtures exhibit negative excess volumes, the curves being nearly symmetrical. The magnitude of the minimum increases steadily with
Journal of Colloid and Interface Science, Mar 15, 2010
Synthesis of silver nanoparticles in homogeneous aqueous solutions of the precursors silver nitra... more Synthesis of silver nanoparticles in homogeneous aqueous solutions of the precursors silver nitrate and three saccharides (two mono saccharides i.e. glucose and fructose and one disaccharide such as sucrose) has been performed. These Ag-nanoparticles can be derivatized by other surface treatments, as required. The anionic surfactant SDS was tested to investigate its effect on the dependence of size, growth rate, photoluminescence (PL) emission and polydispersity of the nanoparticles. The time evolution of UV-vis absorbance suggested that nucleation and growth rate markedly vary in a first order fashion w.r.t. Ag(+) salt concentration. The differences in the reducing ability of the saccharides were discussed with reference to their structure dependent adsorption behavior onto the particles. Changes in UV-vis, PL and FT-IR spectra during nucleation and growth of the nanoparticles were used to establish plausible mechanisms for the adsorption of surfactant on the particle surface, so as to restrict the growth. The results revealed a simple and easy strategy for synthesizing metal nanoparticles with well controlled shapes, sizes and structures.
Journal of Colloid and Interface Science, Oct 15, 2008
The effect of the addition of cyclodextrins (CD) viz., α-, β-, HPβ-and γ -CD to the aqueous solut... more The effect of the addition of cyclodextrins (CD) viz., α-, β-, HPβ-and γ -CD to the aqueous solutions of the most widely prescribed anti-inflammatory drug, diclofenac sodium (DS), has been fully investigated by means of spectroscopic (UV-vis, steady-sate fluorescence, 1 H NMR and ROESY) and thermodynamic (conductivity) techniques. The global picture of the results indicates that diclofenac sodium penetrates the CD cavity. The apparent association constants for all the inclusion complexes were estimated from fluorescence data. Conductivity measurements of aqueous solutions of diclofenac sodium were performed both as a function of DS concentration and CD concentration, at different temperatures ranging from 15 to 40 • C. Results suggested the existence of 1:1 complex between DS and CD. The thermodynamics of the system was discussed in terms of change in Gibbs free energy. Free energy of the DS/W system was found to decrease on addition of cyclodextrin, which points towards the energetically favorable interactions between drug and cyclodextrin molecules in solution phase. 1 H NMR chemical shift changes and ROESY spectra provide powerful means for probing CD:DS interactions.
In recent years, there has been increasing concern about the usage of a broad range of organic su... more In recent years, there has been increasing concern about the usage of a broad range of organic substances, heavy metals and aromatic compounds in the aquatic environment due to their wide distribution and potential adverse health effects. The presence of toxic contaminants in water effluent, even at very low concentrations, is extremely harmful and undesirable. Various treatment processes have been investigated to reduce these toxic pollutants from wastewater. Because of the chemical stability of the contaminants, these technologies have proved to be ineffective for handling waste effluents. Nanotechnology offers the possibility of efficient removal of pollutants as nanoparticles have a smaller size and higher adsorptive surface area. From the past few years, nanoscale iron oxides such as magnetite, maghemite, and hematite have been used for the separation and removal of organic and inorganic contaminants. In this review we summarize the use of iron oxide nanomaterials performed over the last few years for the removal of dyes, heavy metals and aromatic compounds.
Journal of Colloid and Interface Science, Oct 15, 2007
The well-characterized, monodisperse nature of reverse micelles formed by sodium bis-(2-ethylhexy... more The well-characterized, monodisperse nature of reverse micelles formed by sodium bis-(2-ethylhexyl)sulfosuccinate/water/isooctane and their usefulness in assimilating compounds of varied interests have been exploited to investigate the effect of acetyl modified amino acids (MAA) viz., N -acetyl-L-glycine (NAG), N-acetyl-L-aspartic acid (NAA) and N -acetyl-L-cysteine (NAC), on the water pool and physiochemical properties. Non-invasive techniques such as FTIR and UV-vis absorption spectroscopy have been employed to analyze the interactions of MAA with core water and the AOT headgroup. The micropolarities on both sides of AOT interface have further been investigated by UV-vis absorption probes, methyl orange (MO) and methylene blue (MB). The dynamics of water and temperature induced percolation process have also been studied. The MAA molecules have been found to assist the process with the increase in water content where as a contrary behavior has been observed with the increase in temperature. Conductivity results have been further rationalized in terms of scaling equations, which delineate the dynamic nature of the percolation process. The results have also been analyzed in the light of activation energy of the percolation process and thermodynamics of droplet clustering.
Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Apr 1, 1999
We report here results concerning nonaqueous microemulsions containing sodium bis(2-ethylhexyl)su... more We report here results concerning nonaqueous microemulsions containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT)+hexane+nonaqueous polar component, i.e., ethyleneglycol/2-pyrrolidinone/glycerol/methanol, over a wide range of volume fraction (φ) of dispersed phase at 30 °C. The influence of such nonaqueous systems on conductivity, dynamic viscosity, density, and ultrasonic velocity have been investigated. Electrical conductivity (σ) and viscosity (η) data show the existence of a percolation threshold. An excellent agreement between the (σ/φ)expt and (σ/φ)calc calculated from the prediction of the droplet charge fluctuation model has been observed. The aggregation number (n), core radius (rn), and surface number density of the surfactant molecules at the interface (αs) have also been computed. Droplet size in the case of the AOT+hexane+methanol system primarily depends on the molar ratio ω, according to rn=0.545(+/-0.021)+0.366(+/-0.006)ω. The phase behavior showing the realm of existence of microemulsion for the systems AOT+hexane+ethyleneglycol/methanol has been delineated at 30 °C.
Http Dx Doi Org 10 1081 Scc 120016362, Aug 17, 2006
ABSTRACT A number of methyl substituted 2,2′-dipyridyl diselenides and -ditellurides have been pr... more ABSTRACT A number of methyl substituted 2,2′-dipyridyl diselenides and -ditellurides have been prepared. Effect of the solvent and the substituents on the rate of these reactions have also been studied. The preparation of 2-methylseleno/telluro picolines by reductive cleavage of the diselenides and ditellurides and by one pot reaction using n-BuLi at −78°C in THF is reported.
We exploited the added degree of compositional freedom provided by mixed AOT/lecithin surfactants... more We exploited the added degree of compositional freedom provided by mixed AOT/lecithin surfactants in reverse isooctane microemulsion to demonstrate that a small amount of added lecithin significantly enhances the solubility of organodiselenides over that in AOT reverse isooctane microemulsions alone. Conductivity results show that the added lecithin significantly increases the solubility of four different organodiselenides and raises the temperature required to induce percolation. FTIR, (1)H NMR, and UV-visible techniques were utilized to gain insight into the interactions of organodiselenides, AOT and lecithin headgroups with water in the micellar core. The information obtained from these experiments was used to design a novel synthetic route for preparing 4-chloro-2-(naphthalen-2-ylselanyl) pyrimidine in reverse microemulsion.
A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements f... more A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001-0.004 mg mL À1 for HbA1c with a detection limit of 0.0015 mg mL À1 .
Synthesis and Reactivity in Inorganic Metal Organic and Nano Metal Chemistry, Jan 25, 2013
ABSTRACT Mixed ligand, iso-structural zinc(II), [Zn(L1)2(L2)2] 1 and cadmium(II), [Cd(L1)2(L2)2] ... more ABSTRACT Mixed ligand, iso-structural zinc(II), [Zn(L1)2(L2)2] 1 and cadmium(II), [Cd(L1)2(L2)2] 2, (L1 = CCl3COO−, L2 = N,N,N′,N′-tetramethylethylenediamine (tmen)), trichloroacetate complexes have been prepared and characterized by elemental, spectroscopic (ir, nmr), thermogravimetry, molar conductivity, and X-ray studies in 2. The trichloroacetate acts as a monodentate and tmen ligand L2 functions as a bidentate ligand in both the complexes. The crystal structure of 2 is of monoclinic system, space group P21/n with a = 8.3302(19) Ǻ, b = 17.756(4) Ǻ, c = 18.619(4) Ǻ, β = 100.393(3)°, and V = 2708.8(10) Ǻ3, Z = 4. The geometry around the metal is distorted octahedral.
Colloids and Surfaces a Physicochemical and Engineering Aspects, May 1, 2009
In the present contribution, the effect of presence of glycols on the microstructure of reverse m... more In the present contribution, the effect of presence of glycols on the microstructure of reverse micellar formulation of water/AOT/isooctane is presented. It was found that OH, CO and C-O-C stretching frequency of reverse micelles in FTIR change in the presence of glycols. The microenvironment of the polar core and the interface of reverse micelles have been probed by UV-vis absorption probe, methyl orange. The results reveal that glycols are placed between the water phase and the organic phase penetrating the interfacial layer at low water content values whereas with the increase in water content, it migrates to the core water. The polarity of the interface has been further probed by measuring the empirical polarity index values, which decreases with the increase in water content. The effect of glycols on the variation of conductivity with temperature and water content has also been studied.
Colloids and Surfaces a Physicochemical and Engineering Aspects, Mar 1, 2008
... Micellization behavior of cationic surfactant dodecyldimethylethylammonium bromide (DDAB) in ... more ... Micellization behavior of cationic surfactant dodecyldimethylethylammonium bromide (DDAB) in the presence of papain. SK Mehta Corresponding Author Contact Information , a , E-mail The Corresponding Author , Bhawna a , Khushwinder Kaur a and KK Bhasin a. ...
Novel and synthetically important bis[4-dimethylamino-2-pyrimidyl] dichalcogenides (S, Se, Te) ha... more Novel and synthetically important bis[4-dimethylamino-2-pyrimidyl] dichalcogenides (S, Se, Te) have been prepared and characterized with the help of elemental analysis and various spectroscopic techniques. The methodology employs hydrazine hydrate in dimethylformamide to reduce elemental chalcogen to generate the dichalcogenide anions, E22− (E=S, Se, Te), followed by reaction with 2,4-dichloropyrimidine to afford bis[4-dimethylamino-2-pyrimidyl] dichalcogenides in good yield. It further exploits the
The transformation of gibbsite have been studied under hydrothermal influence. Results of the X-r... more The transformation of gibbsite have been studied under hydrothermal influence. Results of the X-ray diffraction analysis of the samples heated at different temperatures from 170~ to 265~ are also discussed in detail. The percentage of the boehmite phase formed, due to the transformation of the gibbsite, have been determined by comparing the intensity of the most strongest reflection of the boehmite phase with a fully transformed sample. The activation energy value calculated form X-ray diffractograms is almost comparable with the value calculated from main DTA endotherm of gibbsite.
... JUNE 1995 Volumetric and transport properties in microemulsions and the point of view of perc... more ... JUNE 1995 Volumetric and transport properties in microemulsions and the point of view of percolation theory S. K. Mehta* and Kiran Bala Department of Chemistry, Panjah University, Chandigarh ... Con-Page 3. S734 S. K. MEHTA AND KIRAN BALA S1 18— lOggp & ...
Ultrasonic speed u and dilatometric measurements of excess volume VE have been carried out for mi... more Ultrasonic speed u and dilatometric measurements of excess volume VE have been carried out for mixtures of pyrrolidin-2-one (PY) with acetonitrile (ACN), propionitrile (PN), butyronitrile (BN), valeronitrile (VN), acrylonitrile (ACRN) and benzonitrile (BEN) at 303.15K over the entire composition range. All the mixtures exhibit negative excess volumes, the curves being nearly symmetrical. The magnitude of the minimum increases steadily with
Journal of Colloid and Interface Science, Mar 15, 2010
Synthesis of silver nanoparticles in homogeneous aqueous solutions of the precursors silver nitra... more Synthesis of silver nanoparticles in homogeneous aqueous solutions of the precursors silver nitrate and three saccharides (two mono saccharides i.e. glucose and fructose and one disaccharide such as sucrose) has been performed. These Ag-nanoparticles can be derivatized by other surface treatments, as required. The anionic surfactant SDS was tested to investigate its effect on the dependence of size, growth rate, photoluminescence (PL) emission and polydispersity of the nanoparticles. The time evolution of UV-vis absorbance suggested that nucleation and growth rate markedly vary in a first order fashion w.r.t. Ag(+) salt concentration. The differences in the reducing ability of the saccharides were discussed with reference to their structure dependent adsorption behavior onto the particles. Changes in UV-vis, PL and FT-IR spectra during nucleation and growth of the nanoparticles were used to establish plausible mechanisms for the adsorption of surfactant on the particle surface, so as to restrict the growth. The results revealed a simple and easy strategy for synthesizing metal nanoparticles with well controlled shapes, sizes and structures.
Journal of Colloid and Interface Science, Oct 15, 2008
The effect of the addition of cyclodextrins (CD) viz., α-, β-, HPβ-and γ -CD to the aqueous solut... more The effect of the addition of cyclodextrins (CD) viz., α-, β-, HPβ-and γ -CD to the aqueous solutions of the most widely prescribed anti-inflammatory drug, diclofenac sodium (DS), has been fully investigated by means of spectroscopic (UV-vis, steady-sate fluorescence, 1 H NMR and ROESY) and thermodynamic (conductivity) techniques. The global picture of the results indicates that diclofenac sodium penetrates the CD cavity. The apparent association constants for all the inclusion complexes were estimated from fluorescence data. Conductivity measurements of aqueous solutions of diclofenac sodium were performed both as a function of DS concentration and CD concentration, at different temperatures ranging from 15 to 40 • C. Results suggested the existence of 1:1 complex between DS and CD. The thermodynamics of the system was discussed in terms of change in Gibbs free energy. Free energy of the DS/W system was found to decrease on addition of cyclodextrin, which points towards the energetically favorable interactions between drug and cyclodextrin molecules in solution phase. 1 H NMR chemical shift changes and ROESY spectra provide powerful means for probing CD:DS interactions.
In recent years, there has been increasing concern about the usage of a broad range of organic su... more In recent years, there has been increasing concern about the usage of a broad range of organic substances, heavy metals and aromatic compounds in the aquatic environment due to their wide distribution and potential adverse health effects. The presence of toxic contaminants in water effluent, even at very low concentrations, is extremely harmful and undesirable. Various treatment processes have been investigated to reduce these toxic pollutants from wastewater. Because of the chemical stability of the contaminants, these technologies have proved to be ineffective for handling waste effluents. Nanotechnology offers the possibility of efficient removal of pollutants as nanoparticles have a smaller size and higher adsorptive surface area. From the past few years, nanoscale iron oxides such as magnetite, maghemite, and hematite have been used for the separation and removal of organic and inorganic contaminants. In this review we summarize the use of iron oxide nanomaterials performed over the last few years for the removal of dyes, heavy metals and aromatic compounds.
Journal of Colloid and Interface Science, Oct 15, 2007
The well-characterized, monodisperse nature of reverse micelles formed by sodium bis-(2-ethylhexy... more The well-characterized, monodisperse nature of reverse micelles formed by sodium bis-(2-ethylhexyl)sulfosuccinate/water/isooctane and their usefulness in assimilating compounds of varied interests have been exploited to investigate the effect of acetyl modified amino acids (MAA) viz., N -acetyl-L-glycine (NAG), N-acetyl-L-aspartic acid (NAA) and N -acetyl-L-cysteine (NAC), on the water pool and physiochemical properties. Non-invasive techniques such as FTIR and UV-vis absorption spectroscopy have been employed to analyze the interactions of MAA with core water and the AOT headgroup. The micropolarities on both sides of AOT interface have further been investigated by UV-vis absorption probes, methyl orange (MO) and methylene blue (MB). The dynamics of water and temperature induced percolation process have also been studied. The MAA molecules have been found to assist the process with the increase in water content where as a contrary behavior has been observed with the increase in temperature. Conductivity results have been further rationalized in terms of scaling equations, which delineate the dynamic nature of the percolation process. The results have also been analyzed in the light of activation energy of the percolation process and thermodynamics of droplet clustering.
Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Apr 1, 1999
We report here results concerning nonaqueous microemulsions containing sodium bis(2-ethylhexyl)su... more We report here results concerning nonaqueous microemulsions containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT)+hexane+nonaqueous polar component, i.e., ethyleneglycol/2-pyrrolidinone/glycerol/methanol, over a wide range of volume fraction (φ) of dispersed phase at 30 °C. The influence of such nonaqueous systems on conductivity, dynamic viscosity, density, and ultrasonic velocity have been investigated. Electrical conductivity (σ) and viscosity (η) data show the existence of a percolation threshold. An excellent agreement between the (σ/φ)expt and (σ/φ)calc calculated from the prediction of the droplet charge fluctuation model has been observed. The aggregation number (n), core radius (rn), and surface number density of the surfactant molecules at the interface (αs) have also been computed. Droplet size in the case of the AOT+hexane+methanol system primarily depends on the molar ratio ω, according to rn=0.545(+/-0.021)+0.366(+/-0.006)ω. The phase behavior showing the realm of existence of microemulsion for the systems AOT+hexane+ethyleneglycol/methanol has been delineated at 30 °C.
Http Dx Doi Org 10 1081 Scc 120016362, Aug 17, 2006
ABSTRACT A number of methyl substituted 2,2′-dipyridyl diselenides and -ditellurides have been pr... more ABSTRACT A number of methyl substituted 2,2′-dipyridyl diselenides and -ditellurides have been prepared. Effect of the solvent and the substituents on the rate of these reactions have also been studied. The preparation of 2-methylseleno/telluro picolines by reductive cleavage of the diselenides and ditellurides and by one pot reaction using n-BuLi at −78°C in THF is reported.
We exploited the added degree of compositional freedom provided by mixed AOT/lecithin surfactants... more We exploited the added degree of compositional freedom provided by mixed AOT/lecithin surfactants in reverse isooctane microemulsion to demonstrate that a small amount of added lecithin significantly enhances the solubility of organodiselenides over that in AOT reverse isooctane microemulsions alone. Conductivity results show that the added lecithin significantly increases the solubility of four different organodiselenides and raises the temperature required to induce percolation. FTIR, (1)H NMR, and UV-visible techniques were utilized to gain insight into the interactions of organodiselenides, AOT and lecithin headgroups with water in the micellar core. The information obtained from these experiments was used to design a novel synthetic route for preparing 4-chloro-2-(naphthalen-2-ylselanyl) pyrimidine in reverse microemulsion.
A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements f... more A one-step homogeneous colorimetric immunoassay format coupled with zeta potential measurements for determination of specific diabetic biomarker glycated hemoglobin (HbA1c) using functionalised gold nanoparticles as bioprobes is reported. The assay exhibited an excellent sensitivity based on absorbance and zeta potential measurements showing the dynamic response range from 0.001-0.004 mg mL À1 for HbA1c with a detection limit of 0.0015 mg mL À1 .
Synthesis and Reactivity in Inorganic Metal Organic and Nano Metal Chemistry, Jan 25, 2013
ABSTRACT Mixed ligand, iso-structural zinc(II), [Zn(L1)2(L2)2] 1 and cadmium(II), [Cd(L1)2(L2)2] ... more ABSTRACT Mixed ligand, iso-structural zinc(II), [Zn(L1)2(L2)2] 1 and cadmium(II), [Cd(L1)2(L2)2] 2, (L1 = CCl3COO−, L2 = N,N,N′,N′-tetramethylethylenediamine (tmen)), trichloroacetate complexes have been prepared and characterized by elemental, spectroscopic (ir, nmr), thermogravimetry, molar conductivity, and X-ray studies in 2. The trichloroacetate acts as a monodentate and tmen ligand L2 functions as a bidentate ligand in both the complexes. The crystal structure of 2 is of monoclinic system, space group P21/n with a = 8.3302(19) Ǻ, b = 17.756(4) Ǻ, c = 18.619(4) Ǻ, β = 100.393(3)°, and V = 2708.8(10) Ǻ3, Z = 4. The geometry around the metal is distorted octahedral.
Colloids and Surfaces a Physicochemical and Engineering Aspects, May 1, 2009
In the present contribution, the effect of presence of glycols on the microstructure of reverse m... more In the present contribution, the effect of presence of glycols on the microstructure of reverse micellar formulation of water/AOT/isooctane is presented. It was found that OH, CO and C-O-C stretching frequency of reverse micelles in FTIR change in the presence of glycols. The microenvironment of the polar core and the interface of reverse micelles have been probed by UV-vis absorption probe, methyl orange. The results reveal that glycols are placed between the water phase and the organic phase penetrating the interfacial layer at low water content values whereas with the increase in water content, it migrates to the core water. The polarity of the interface has been further probed by measuring the empirical polarity index values, which decreases with the increase in water content. The effect of glycols on the variation of conductivity with temperature and water content has also been studied.
Colloids and Surfaces a Physicochemical and Engineering Aspects, Mar 1, 2008
... Micellization behavior of cationic surfactant dodecyldimethylethylammonium bromide (DDAB) in ... more ... Micellization behavior of cationic surfactant dodecyldimethylethylammonium bromide (DDAB) in the presence of papain. SK Mehta Corresponding Author Contact Information , a , E-mail The Corresponding Author , Bhawna a , Khushwinder Kaur a and KK Bhasin a. ...
Novel and synthetically important bis[4-dimethylamino-2-pyrimidyl] dichalcogenides (S, Se, Te) ha... more Novel and synthetically important bis[4-dimethylamino-2-pyrimidyl] dichalcogenides (S, Se, Te) have been prepared and characterized with the help of elemental analysis and various spectroscopic techniques. The methodology employs hydrazine hydrate in dimethylformamide to reduce elemental chalcogen to generate the dichalcogenide anions, E22− (E=S, Se, Te), followed by reaction with 2,4-dichloropyrimidine to afford bis[4-dimethylamino-2-pyrimidyl] dichalcogenides in good yield. It further exploits the
The transformation of gibbsite have been studied under hydrothermal influence. Results of the X-r... more The transformation of gibbsite have been studied under hydrothermal influence. Results of the X-ray diffraction analysis of the samples heated at different temperatures from 170~ to 265~ are also discussed in detail. The percentage of the boehmite phase formed, due to the transformation of the gibbsite, have been determined by comparing the intensity of the most strongest reflection of the boehmite phase with a fully transformed sample. The activation energy value calculated form X-ray diffractograms is almost comparable with the value calculated from main DTA endotherm of gibbsite.
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