How mobile is the water in the reverse micelles? A 2DIR study with an ultrasmall IR probe

Mora, Aruna K.; Singh, Prabhat; Nadkarni, Shirish A.; Nath, Sukhendu

doi:10.1016/j.molliq.2020.114819

Cited by 6 publications

(4 citation statements)

References 32 publications

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“…The absolute zero is determined from the field auto-correlation. The change in the shape and tilt of the processed 2D-IR spectra has been analyzed by nodal line slope analysis …”

Section: Methodsmentioning

confidence: 99%

“…The details of the 2D-IR spectrometer have been explained elsewhere. , In brief, the 2D-IR spectrometer, in a pump–probe geometry, has been designed and constructed around a Ti-sapphire amplified laser system. The current setup has been upgraded with the use of an MCT array detector (2X 32, CDP Inc., Russia) instead of the previously used single-element MCT detector.…”

Section: Methodsmentioning

confidence: 99%

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2D-IR Spectroscopy of Nitrosyl Stretch of Sodium Nitroprusside Reveals the Elusive Two Anomalous Regions in the DMSO–Water Mixture

et al. 2023

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DMSO−water mixtures provide an intriguing hydrogen-bonding environment which has been a subject of various theoretical and experimental investigations. The structural dynamics of aqueous DMSO solutions has been investigated, using nitrosyl stretch of sodium nitroprusside (SNP, Na 2 [Fe(CN) 5 NO]) as a local vibrational probe, with the help of infrared (IR) absorption spectroscopy, vibrational pump−probe spectroscopy, and two-dimensional IR spectroscopy (2D-IR). Fourier transform infrared spectra of the nitrosyl stretch of SNP reveals that both the peak position and spectral broadening are very sensitive to the composition of the DMSO−water mixture and the subsequent structural changes occurring due to the addition of DMSO to water. The vibrational lifetime of the nitrosyl stretch displays two different linear variation regimes as a function of mole fraction of DMSO which has been assigned presumably to two different predominant structures at these compositions. However, the rotational depolarization measurements show that the reorientational times follow a bell-shaped profile, imitating the changes in the composition-dependent physical properties (viscosity) of DMSO−water solvent mixtures. To get a holistic picture of the system, 2D-IR spectroscopy of the NO stretch of SNP has been employed to study time scales of hydrogen-bond reorganization dynamics existing at different compositions. The analysis of frequency−frequency correlation function (FFCF) decay times reveal that the dynamics gets slower in intermediate DMSO concentrations than that of pure DMSO or pure water. A careful analysis reveals two anomalous regions of hydrogen-bond dynamics: X DMSO ∼0.2 and 0.4, which indicates that different hydrogen-bonded structures exist in these regions that can be effectively probed by SNP which has remained mostly elusive to previous vibrational probe-based investigations.

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“…The absolute zero is determined from the field auto-correlation. The change in the shape and tilt of the processed 2D-IR spectra has been analyzed by nodal line slope analysis …”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

2D-IR Spectroscopy of Nitrosyl Stretch of Sodium Nitroprusside Reveals the Elusive Two Anomalous Regions in the DMSO–Water Mixture

et al. 2023

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“…Infrared spectroscopy is highly sensitive to the electrostatic environment surrounding a vibrational probe. − In particular, carbonyl stretching line shapes are sensitive to H-bond populations; an H-bond red-shifts the carbonyl frequency compared to the free carbonyl (Figure ). Characterizing interfacial effects on confined environments necessitates a molecular understanding of the relationship between composition, interfacial charge, localization, and their effects on interfacial environments. , Solvation dynamics at the interface are essential for a complete description of interfacial environments. , Ultrafast infrared spectroscopy offers the ability to probe the interfacial dynamics at the RM interface, resolving the changes introduced between the aqueous core of the RM and charged encapsulants. , This study leverages two-dimensional infrared spectroscopy (2D IR) to probe the Span-60 ester carbonyl and measure the effects of heterogeneous surfactant composition and charge–charge interactions between the interface and PEI on water dynamics on the subpicosecond time scale. The ester carbonyls (Figure A) are precisely located in the region between the hydrophilic headgroup region and the hydrophobic tails and are therefore ideal probes for the interfacial environment.…”

Section: Introductionmentioning

confidence: 99%

“…43,44 Ultrafast infrared spectroscopy offers the ability to probe the interfacial dynamics at the RM interface, resolving the changes introduced between the aqueous core of the RM and charged encapsulants. 45,46 This study leverages two-dimensional infrared spectroscopy (2D IR) to probe the Span-60 ester carbonyl and measure the effects of heterogeneous surfactant composition and charge−charge interactions between the interface and PEI on water dynamics on the subpicosecond time scale. The ester carbonyls (Figure 1A) are precisely located in the region between the hydrophilic headgroup region and the hydrophobic tails and are therefore ideal probes for the interfacial environment.…”

Section: ■ Introductionmentioning

confidence: 99%

Forced Interactions: Ionic Polymers at Charged Surfactant Interfaces

2023

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Characterizing electrostatic interactions at heterogeneous interfaces is critical for developing a fundamental description of the dynamic processes at charged interfaces. Water-in-oil reverse micelles (RMs) offer a high degree of tunability across composition, polarity, and temperature, making them ideal systems for studying interactions at heterogeneous liquid−liquid interfaces. In the present study, we use a combination of ultrafast two-dimensional infrared spectroscopy and molecular dynamics (MD) simulations to determine the picosecond interfacial dynamics in RMs containing binary compositions of sorbitan monostearate and anionic or cationic cosurfactants, which are used to tune the ratio of charged to nonionic surfactants at the interface. The positively charged polyethylenimine (PEI) polymer is encapsulated within the RMs, and the carbonyl stretching mode of sorbitan monostearate reports on the interfacial hydrogen-bond populations and dynamics. The results show that hydrogen-bond populations are altered through the inclusion of both negatively and positively charged cosurfactants. Charged surfactants increase interfacial water penetration into the surfactant layer, and the surface localization of polymers decreases water penetration. Local hydrogen-bond dynamics undergo a slowdown with the inclusion of charged surfactants, and the encapsulation of polymers results in similar effects, irrespective of the charge.

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Recent advances in understanding the interfacial activity of antioxidants in association colloids in bulk oil

Wang,

Chen,

McClements

et al. 2024

Advances in Colloid and Interface Science

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How mobile is the water in the reverse micelles? A 2DIR study with an ultrasmall IR probe

Cited by 6 publications

References 32 publications

2D-IR Spectroscopy of Nitrosyl Stretch of Sodium Nitroprusside Reveals the Elusive Two Anomalous Regions in the DMSO–Water Mixture

2D-IR Spectroscopy of Nitrosyl Stretch of Sodium Nitroprusside Reveals the Elusive Two Anomalous Regions in the DMSO–Water Mixture

Forced Interactions: Ionic Polymers at Charged Surfactant Interfaces

Recent advances in understanding the interfacial activity of antioxidants in association colloids in bulk oil

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