Influence of Chain Length of Alcohols on Stokes’ Shift Dynamics in Catanionic Vesicles

Sarma, N. V.; Borah, Jayanta M.; Mahiuddin, Sekh; Gazi, Harun Al Rasid; Guchhait, Biswajit; Biswas, Ranjit

doi:10.1021/jp201402h

Cited by 32 publications

(16 citation statements)

References 123 publications

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“…Note that all the calculated average times in these panels show non-monotonic composition dependence to varying degrees. This is not surprising as several earlier time-resolved fluorescence measurements have already reported nonlinear composition dependence of various relaxation rates in bulk aqueous solutions of alcohols and other amphiphilic molecules. − The interesting aspect of this general observation is, however, the emergence of this non-monotonicity in simulations of composition-dependent H-bond fluctuation dynamics, where coarse-grained classical interaction potentials have been employed. This reflects that these model interaction potentials are capable of qualitatively capturing the solution structure of these binary mixtures although the composition at which the abrupt change in the slope of the average relaxation times occurred differs between simulations and dynamic fluorescence measurements.…”

Section: Resultsmentioning

confidence: 77%

Does Confinement Modify Preferential Solvation and H-Bond Fluctuation Dynamics? A Molecular Level Investigation through Simulations of a Bulk and Confined Three-Component Mixture

Baksi

Biswas

2020

J. Phys. Chem. B

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Exploring the local environment around a dissolved solute in a bulk aqueous solution of alcohol and assessing the impact of confinement on the solvation structure is an important topic yet is much less studied. Such a study is important because it can provide critical information regarding the miscibility of an amphiphilic drug after delivery at a designated nanoscopic site and the subsequent release. The present molecular dynamics simulation study reports an in-depth investigation of the composition-dependent solvation structure around a dissolved hydrophobic solute, coumarin 153 (C153), in ambient binary mixtures of methanol and water in both bulk and under confinement. The confinement is a spherical sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle with a diameter of 55 Å. Inter- and intraspecies H-bond fluctuation dynamics have been monitored and compared with those from the corresponding bulk binary mixtures. A systematic comparison of both solvation structure and H-bond dynamics between confined and bulk binary mixtures reveals modulation of both preferential solvation and H-bond relaxation times inside a nanoscopic environment. More specifically, confinement accentuates the preferential solvation phenomenon and facilitates di-mixing of mixture components. In addition, the present study reveals that the tetrahedral H-bond network of neat liquid water becomes severely affected upon addition of methanol, which becomes further distorted under confinement. Confinement severely affects the interspecies hydrogen bonds and makes the corresponding continuous hydrogen bonds much shorter-lived. Interestingly, structural hydrogen bond relaxation timescales become longer in confined binary mixtures than those in bulk binary mixtures.

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Section: Resultsmentioning

confidence: 77%

Does Confinement Modify Preferential Solvation and H-Bond Fluctuation Dynamics? A Molecular Level Investigation through Simulations of a Bulk and Confined Three-Component Mixture

Baksi

Biswas

2020

J. Phys. Chem. B

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“…[66][67][68] The geometric factor (G) was obtained by tail matching the collected I para (t) and I perp (t) decays at time longer than the anticipated rotation time. Normalized r(t) decays, like the S(t) decays, were also found to be bi-exponentials and average rotation times were obtained as follows:…”

Section: Methodsmentioning

confidence: 99%

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

Guchhait

Das

Daschakraborty

et al. 2014

The Journal of Chemical Physics

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167

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Here we investigate the solute-medium interaction and solute-centered dynamics in (RCONH2 + LiX) deep eutectics (DEs) via carrying out time-resolved fluorescence measurements and all-atom molecular dynamics simulations at various temperatures. Alkylamides (RCONH2) considered are acetamide (CH3CONH2), propionamide (CH3CH2CONH2), and butyramide (CH3CH2CH2CONH2); the electrolytes (LiX) are lithium perchlorate (LiClO4), lithium bromide (LiBr), and lithium nitrate (LiNO3). Differential scanning calorimetric measurements reveal glass transition temperatures (T(g)) of these DEs are ~195 K and show a very weak dependence on alkyl chain-length and electrolyte identity. Time-resolved and steady state fluorescence measurements with these DEs have been carried out at six-to-nine different temperatures that are ~100-150 K above their individual T(g)s. Four different solute probes providing a good spread of fluorescence lifetimes have been employed in steady state measurements, revealing strong excitation wavelength dependence of probe fluorescence emission peak frequencies. Extent of this dependence, which shows sensitivity to anion identity, has been found to increase with increase of amide chain-length and decrease of probe lifetime. Time-resolved measurements reveal strong fractional power dependence of average rates for solute solvation and rotation with fraction power being relatively smaller (stronger viscosity decoupling) for DEs containing longer amide and larger (weaker decoupling) for DEs containing perchlorate anion. Representative all-atom molecular dynamics simulations of (CH3CONH2 + LiX) DEs at different temperatures reveal strongly stretched exponential relaxation of wavevector dependent acetamide self dynamic structure factor with time constants dependent both on ion identity and temperature, providing justification for explaining the fluorescence results in terms of temporal heterogeneity and amide clustering in these multi-component melts.

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“…FWHM of the instrument response function (IRF) was ∼75 ps. Established protocol [40][41][42][43][44][45] was followed to collect the magic angle (54.7 • ) and parallel (I || (t)) and perpendicular (I ⊥ (t)) emission intensity decays and to construct the time-resolved fluorescence anisotropy, r(t),…”

Section: B Data Collection and Analysis For Steady-state Fluorescencmentioning

confidence: 99%

Heterogeneity in (2-butoxyethanol + water) mixtures: Hydrophobicity-induced aggregation or criticality-driven concentration fluctuations?

Indra

Biswas

2015

The Journal of Chemical Physics

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Micro-heterogeneity in aqueous solutions of 2-butoxyethanol (BE), a system with closed loop miscibility gap, has been explored via absorption and time-resolved fluorescence measurements of a dissolved dipolar solute, coumarin 153 (C153), in the water-rich region at various BE mole fractions (0 ≤ XBE ≤ 0.25) in the temperature range, 278 ≤ T/K ≤ 320. Evidences for both alcohol-induced H-bond strengthening and subsequent structural transition of H-bond network have been observed. Analyses of steady state and time-resolved spectroscopic data for these aqueous mixtures and comparisons with the results for aqueous solutions of ethanol and tertiary butanol indicate that alcohol aggregation in BE/water mixtures is driven by hydrophobic interaction with no or insignificant role for criticality-driven concentration fluctuations preceding phase separation. Excitation energy dependence of fluorescence emission of C153 confirms formation of aggregated structures at very low BE mole fractions. No asymptotic critical power law dependence for relaxation rates of the type, k ∝ (|T - Tc|/Tc)(γ), with γ denoting universal critical constant, has been observed for both solute's rotational relaxation and population relaxation rates in these mixtures upon either approaching to critical concentration or critical temperature. Estimated activation energies for rotational relaxation rate of C153 and solution viscosity have been found to follow each other with no abrupt changes in either of them at any mixture composition. In addition, measured C153 rotation times at various compositions and temperatures reflect near-hydrodynamic viscosity coupling through the dependence,〈τr〉∝ (η/T)(p), with p = 0.8-1.0, suggesting solute's orientational relaxation dynamics being, on an average, temporally homogeneous.

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Influence of Chain Length of Alcohols on Stokes’ Shift Dynamics in Catanionic Vesicles

Cited by 32 publications

References 123 publications

Does Confinement Modify Preferential Solvation and H-Bond Fluctuation Dynamics? A Molecular Level Investigation through Simulations of a Bulk and Confined Three-Component Mixture

Does Confinement Modify Preferential Solvation and H-Bond Fluctuation Dynamics? A Molecular Level Investigation through Simulations of a Bulk and Confined Three-Component Mixture

Interaction and dynamics of (alkylamide + electrolyte) deep eutectics: Dependence on alkyl chain-length, temperature, and anion identity

Heterogeneity in (2-butoxyethanol + water) mixtures: Hydrophobicity-induced aggregation or criticality-driven concentration fluctuations?

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