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Debi D Pant - One of the best experts on this subject based on the ideXlab platform.
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interaction of Quinine Sulfate with anionic micelles of sodium dodecylSulfate a time resolved fluorescence spectroscopy at different ph
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015Co-Authors: Sunita Joshi, Debi D PantAbstract:Abstract Photophysical behavior and rotational relaxation dynamics of Quinine Sulfate (QS) in anionic surfactant, sodium dodecylSulfate (SDS) at different pH have been studied using steady state and time resolved fluorescence spectroscopy. It has been observed that the cationic form of Quinine Sulfate (at pH 2) forms a fluorescent ion pair complex with the surfactant molecules at lower concentrations of surfactant. However, for higher concentrations of SDS, the probe molecules bind strongly with the micelles and reside at the water–micelle interface. At pH 7, QS is singly protonated in bulk aqueous solution. At lower concentrations of SDS aggregation between probe and surfactant molecules has been observed. However, for higher concentrations of SDS, an additional fluorescence peak corresponding to dicationic form of QS appears and this has been attributed to double protonation of the QS molecule in micellar solution. At pH 7, in the presence of SDS micelles, the photophysical properties of QS showed substantial changes compared to that in the bulk water solution. At pH 12, an increase in fluorescence intensity and lifetime has been observed and this has been attributed to the increase in radiative rate due to the incorporation of QS at the micelle–water interface. The local pH at micellar surface has been found different from the pH of bulk solution.
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dynamic fluorescence quenching of Quinine Sulfate dication by chloride ion in ionic and neutral micellar environments
SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013, 2014Co-Authors: Sunita Joshi, Tej Varma Y, Debi D PantAbstract:Fluorescence quenching of Quinine Sulfate dication (QSD) by chloride-ion (Cl−) in micellar environments of anionic, sodium dodecyl Sulfate (SDS), cationic, cetyltrimethylammonium bromide (CTAB) and neutral, triton X-100 (TX-100) in aqueous phase has been investigated by time-resolved and steady- state fluorescence measurements. The quenching follows linear Stern-Volmer relation in micellar solutions and is dynamic in nature.
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steady state and time resolved fluorescence spectroscopy of Quinine Sulfate dication bound to sodium dodecylSulfate micelles fluorescent complex formation
Journal of Luminescence, 2014Co-Authors: Sunita Joshi, Debi D PantAbstract:Interaction of Quinine Sulfate dication (QSD) with anionic, sodium dodecylsulphate (SDS) surfactant has been studied at different premicellar, micellar and postmicellar concentrations in aqueous phase using steady state, time-resolved fluorescence and fluorescence anisotropy techniques. At premicellar concentrations of SDS, the decrease in absorbance, appearance of an extra fluorescence band at lower wavelengths and tri-exponential decay behavior of fluorescence, are attributed to complex formation between QSD molecules and surfactant monomers. At postmicellar concentrations the red shift in fluorescence spectrum, increase in quantum yield and increase in fluorescence lifetimes are attributed to incorporation of solute molecules to micelles. At lower concentrations of SDS, a large shift in fluorescence is observed on excitation at the red edge of absorption spectrum and this is explained in terms of distribution of ion pairs of different energies in the ground state and the observed fluorescence lifetime behavior corroborates with this model. The temporal fluorescence anisotropy decay of QSD in SDS micelles allowed determination of restriction on the motion of the fluorophore. All the different techniques used in this study reveal that the photophysics of QSD is very sensitive to the microenvironments of SDS micelles and QSD molecules reside at the water-micelle interface.
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steady state and time resolved fluorescence spectroscopy of Quinine Sulfate dication in ionic and neutral micelles effect of micellar charge on photophysics
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013Co-Authors: Sunita Joshi, Tej Varma Y, Debi D PantAbstract:Steady state and time-resolved fluorescence studies have been carried out to investigate the effects of micellar surface charge on the photophysics of a well known fluorescent molecule Quinine Sulfate dication (QSD) in cationic, cetyltrimethylammonium bromide (CTAB), anionic, sodium dodecylsulphate (SDS) and neutral, triton X-100 (TX100) surfactants at concentrations above the critical micelle concentrations (c.m.c) in aqueous phase. Edge excitation red shift (EERS) in fluorescence maximum of QSD has been observed in all the surfactant solutions studied. The magnitude of observed EERS is less in anionic SDS surfactant solution compared to the EERS in CTAB and TX100 surfactants. The magnitude of EERS in CTAB and TX100 is almost the same as in bulk water solution. The EERS has been ascribed in terms of solvent relaxation process. The observed multi-exponential decay of fluorescence is due to the different locations of QSD in micellar systems. In SDS surfactant system, due to heterogeneous restricted motion of solvent molecules the solvent relaxation rate decreases which results in a decrease in net magnitude of EERS and fluorescence decay components fit in three exponentials. Following the two step and wobbling in a cone model for the analysis of the temporal fluorescence anisotropy decay of QSD in SDS micelles allows determination of restriction on the motion of fluorophore. Further, we have shown that the extraordinary capability to sense the surrounding environment makes QSD molecule very efficient for surface and interface studies and can also be used as a probe to investigate the mobility of solvent molecules around the excited molecules.
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ground and excited state dipole moments of Quinine Sulfate dication solvatochromic shift of absorption and fluorescence spectra
Journal of Molecular Liquids, 2012Co-Authors: Sunita Joshi, Debi D PantAbstract:Abstract Electronic absorption and fluorescence spectra of Quinine Sulfate dication (QSD) have been recorded at room temperature in a wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas a red shift in fluorescence emission maximum was observed. The ground-state dipole moment of QSD was obtained from quantum mechanical calculations and the first excited singlet state dipole moment of QSD was obtained from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. Very high value of dipole moment is observed for excited state as compared to the corresponding ground state value and this is attributed to the more polar excited state of QSD. Compared to the dipole moment of Quinine Sulfate, both the ground and excited state dipole moments of QSD are lower.
Sunita Joshi - One of the best experts on this subject based on the ideXlab platform.
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interaction of Quinine Sulfate with anionic micelles of sodium dodecylSulfate a time resolved fluorescence spectroscopy at different ph
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015Co-Authors: Sunita Joshi, Debi D PantAbstract:Abstract Photophysical behavior and rotational relaxation dynamics of Quinine Sulfate (QS) in anionic surfactant, sodium dodecylSulfate (SDS) at different pH have been studied using steady state and time resolved fluorescence spectroscopy. It has been observed that the cationic form of Quinine Sulfate (at pH 2) forms a fluorescent ion pair complex with the surfactant molecules at lower concentrations of surfactant. However, for higher concentrations of SDS, the probe molecules bind strongly with the micelles and reside at the water–micelle interface. At pH 7, QS is singly protonated in bulk aqueous solution. At lower concentrations of SDS aggregation between probe and surfactant molecules has been observed. However, for higher concentrations of SDS, an additional fluorescence peak corresponding to dicationic form of QS appears and this has been attributed to double protonation of the QS molecule in micellar solution. At pH 7, in the presence of SDS micelles, the photophysical properties of QS showed substantial changes compared to that in the bulk water solution. At pH 12, an increase in fluorescence intensity and lifetime has been observed and this has been attributed to the increase in radiative rate due to the incorporation of QS at the micelle–water interface. The local pH at micellar surface has been found different from the pH of bulk solution.
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dynamic fluorescence quenching of Quinine Sulfate dication by chloride ion in ionic and neutral micellar environments
SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013, 2014Co-Authors: Sunita Joshi, Tej Varma Y, Debi D PantAbstract:Fluorescence quenching of Quinine Sulfate dication (QSD) by chloride-ion (Cl−) in micellar environments of anionic, sodium dodecyl Sulfate (SDS), cationic, cetyltrimethylammonium bromide (CTAB) and neutral, triton X-100 (TX-100) in aqueous phase has been investigated by time-resolved and steady- state fluorescence measurements. The quenching follows linear Stern-Volmer relation in micellar solutions and is dynamic in nature.
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steady state and time resolved fluorescence spectroscopy of Quinine Sulfate dication bound to sodium dodecylSulfate micelles fluorescent complex formation
Journal of Luminescence, 2014Co-Authors: Sunita Joshi, Debi D PantAbstract:Interaction of Quinine Sulfate dication (QSD) with anionic, sodium dodecylsulphate (SDS) surfactant has been studied at different premicellar, micellar and postmicellar concentrations in aqueous phase using steady state, time-resolved fluorescence and fluorescence anisotropy techniques. At premicellar concentrations of SDS, the decrease in absorbance, appearance of an extra fluorescence band at lower wavelengths and tri-exponential decay behavior of fluorescence, are attributed to complex formation between QSD molecules and surfactant monomers. At postmicellar concentrations the red shift in fluorescence spectrum, increase in quantum yield and increase in fluorescence lifetimes are attributed to incorporation of solute molecules to micelles. At lower concentrations of SDS, a large shift in fluorescence is observed on excitation at the red edge of absorption spectrum and this is explained in terms of distribution of ion pairs of different energies in the ground state and the observed fluorescence lifetime behavior corroborates with this model. The temporal fluorescence anisotropy decay of QSD in SDS micelles allowed determination of restriction on the motion of the fluorophore. All the different techniques used in this study reveal that the photophysics of QSD is very sensitive to the microenvironments of SDS micelles and QSD molecules reside at the water-micelle interface.
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steady state and time resolved fluorescence spectroscopy of Quinine Sulfate dication in ionic and neutral micelles effect of micellar charge on photophysics
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2013Co-Authors: Sunita Joshi, Tej Varma Y, Debi D PantAbstract:Steady state and time-resolved fluorescence studies have been carried out to investigate the effects of micellar surface charge on the photophysics of a well known fluorescent molecule Quinine Sulfate dication (QSD) in cationic, cetyltrimethylammonium bromide (CTAB), anionic, sodium dodecylsulphate (SDS) and neutral, triton X-100 (TX100) surfactants at concentrations above the critical micelle concentrations (c.m.c) in aqueous phase. Edge excitation red shift (EERS) in fluorescence maximum of QSD has been observed in all the surfactant solutions studied. The magnitude of observed EERS is less in anionic SDS surfactant solution compared to the EERS in CTAB and TX100 surfactants. The magnitude of EERS in CTAB and TX100 is almost the same as in bulk water solution. The EERS has been ascribed in terms of solvent relaxation process. The observed multi-exponential decay of fluorescence is due to the different locations of QSD in micellar systems. In SDS surfactant system, due to heterogeneous restricted motion of solvent molecules the solvent relaxation rate decreases which results in a decrease in net magnitude of EERS and fluorescence decay components fit in three exponentials. Following the two step and wobbling in a cone model for the analysis of the temporal fluorescence anisotropy decay of QSD in SDS micelles allows determination of restriction on the motion of fluorophore. Further, we have shown that the extraordinary capability to sense the surrounding environment makes QSD molecule very efficient for surface and interface studies and can also be used as a probe to investigate the mobility of solvent molecules around the excited molecules.
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ground and excited state dipole moments of Quinine Sulfate dication solvatochromic shift of absorption and fluorescence spectra
Journal of Molecular Liquids, 2012Co-Authors: Sunita Joshi, Debi D PantAbstract:Abstract Electronic absorption and fluorescence spectra of Quinine Sulfate dication (QSD) have been recorded at room temperature in a wide range of solvents of different polarities. The absorption maximum remains almost unchanged with the increase in solvent polarity, whereas a red shift in fluorescence emission maximum was observed. The ground-state dipole moment of QSD was obtained from quantum mechanical calculations and the first excited singlet state dipole moment of QSD was obtained from Bakhshiev's and Bilot–Kawski's equations by means of solvatochromic shift method. Very high value of dipole moment is observed for excited state as compared to the corresponding ground state value and this is attributed to the more polar excited state of QSD. Compared to the dipole moment of Quinine Sulfate, both the ground and excited state dipole moments of QSD are lower.
T A King - One of the best experts on this subject based on the ideXlab platform.
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effect of pmma impregnation on the fluorescence quantum yield of sol gel glasses doped with Quinine Sulfate
Optical Materials, 2001Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, M Torrescisneros, T A KingAbstract:Abstract The fluorescence quantum yield of Quinine Sulfate in sol–gel and PMMA impregnated glasses is measured. The observed quantum yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the fluorescence yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
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Effect of PMMA impregnation on the fluorescence quantum yield of sol–gel glasses doped with Quinine Sulfate
Optical Materials, 2001Co-Authors: Marco-antonio Meneses-nava, Oracio Barbosa-garcía, Luis A. Diaz-torres, S Chávez-cerda, Miguel Torres-cisneros, T A KingAbstract:Abstract The fluorescence quantum yield of Quinine Sulfate in sol–gel and PMMA impregnated glasses is measured. The observed quantum yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the fluorescence yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
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free volume effects on the fluorescence characteristics of sol gel glasses doped with Quinine Sulfate
Optical Materials, 1999Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, T A KingAbstract:Abstract The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of Quinine Sulfate doped sol–gel glasses, before and after PMMA polymer impregnation, are investigated at different concentrations. The fluorescence decay of the Quinine Sulfate doped samples does not fit to a single exponential, as it does in ethanol solutions. We found that a double exponential gives a good fit to the obtained results. Introduction of solvent to fill the pores of the matrix does not only have the same effect as the polymer, but also reveals the strong attachment of the molecules to the pore walls and the influence of the interaction with the cage.
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Free volume effects on the fluorescence characteristics of sol–gel glasses doped with Quinine Sulfate
Optical Materials, 1999Co-Authors: Marco-antonio Meneses-nava, Oracio Barbosa-garcía, Luis A. Diaz-torres, S Chávez-cerda, T A KingAbstract:Abstract The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of Quinine Sulfate doped sol–gel glasses, before and after PMMA polymer impregnation, are investigated at different concentrations. The fluorescence decay of the Quinine Sulfate doped samples does not fit to a single exponential, as it does in ethanol solutions. We found that a double exponential gives a good fit to the obtained results. Introduction of solvent to fill the pores of the matrix does not only have the same effect as the polymer, but also reveals the strong attachment of the molecules to the pore walls and the influence of the interaction with the cage.
M A Menesesnava - One of the best experts on this subject based on the ideXlab platform.
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effect of pmma impregnation on the fluorescence quantum yield of sol gel glasses doped with Quinine Sulfate
Optical Materials, 2001Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, M Torrescisneros, T A KingAbstract:Abstract The fluorescence quantum yield of Quinine Sulfate in sol–gel and PMMA impregnated glasses is measured. The observed quantum yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the fluorescence yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
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free volume effects on the fluorescence characteristics of sol gel glasses doped with Quinine Sulfate
Optical Materials, 1999Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, T A KingAbstract:Abstract The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of Quinine Sulfate doped sol–gel glasses, before and after PMMA polymer impregnation, are investigated at different concentrations. The fluorescence decay of the Quinine Sulfate doped samples does not fit to a single exponential, as it does in ethanol solutions. We found that a double exponential gives a good fit to the obtained results. Introduction of solvent to fill the pores of the matrix does not only have the same effect as the polymer, but also reveals the strong attachment of the molecules to the pore walls and the influence of the interaction with the cage.
S Chavezcerda - One of the best experts on this subject based on the ideXlab platform.
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effect of pmma impregnation on the fluorescence quantum yield of sol gel glasses doped with Quinine Sulfate
Optical Materials, 2001Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, M Torrescisneros, T A KingAbstract:Abstract The fluorescence quantum yield of Quinine Sulfate in sol–gel and PMMA impregnated glasses is measured. The observed quantum yield improvement in the sol–gel matrix, compared to ethanol, is interpreted as a reduction of non-radiative relaxation channels by isolation of the molecules by the cage of the glass. PMMA impregnated sol–gel glasses show an extra improvement of the fluorescence yield, which is interpreted as a reduction of the free space and the rigid fixation of the molecules to the matrix.
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free volume effects on the fluorescence characteristics of sol gel glasses doped with Quinine Sulfate
Optical Materials, 1999Co-Authors: M A Menesesnava, O Barbosagarcia, L A Diaztorres, S Chavezcerda, T A KingAbstract:Abstract The broadening of the absorption and fluorescence spectra and the red shift of the fluorescence maximum of Quinine Sulfate doped sol–gel glasses, before and after PMMA polymer impregnation, are investigated at different concentrations. The fluorescence decay of the Quinine Sulfate doped samples does not fit to a single exponential, as it does in ethanol solutions. We found that a double exponential gives a good fit to the obtained results. Introduction of solvent to fill the pores of the matrix does not only have the same effect as the polymer, but also reveals the strong attachment of the molecules to the pore walls and the influence of the interaction with the cage.
