Vibrational Energy Transfer Across a Reverse Micelle Surfactant Layer

Deàk, John; Pang, Yoonsoo; Sechler, Timothy D.; Wang, Zhaohui; Dlott, Dana D.

doi:10.1126/science.1102074

Cited by 120 publications

(134 citation statements)

References 23 publications

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“…This picture of heat diffusion out of the reverse micelles, thereby causing the long-lived signal to decay, is consistent with observations of hydrogen-bond dissociation and reformation dynamics of methanol oligomers in CCl 4 . 78 It is interesting to contrast these results with those presented by Dlott and co-workers, 45 who examined the vibrational cascade of the excited OH stretch of H 2 O in AOT reverse micelles. The experiments measure the vibrational relaxation of two different fundamental transitions: the OD stretch of HOD in the experiments described in this paper and the OH stretch of H 2 O in the work presented by Dlott and co-workers.…”

Section: Resultsmentioning

confidence: 87%

“…A qualitative comparison of the vibrational relaxation shows that similar trends are observed in the two experiments. Dlott and co-workers 45 reported a factor of 2.5 increase in the vibrational lifetime of the OH stretch when confined to a w 0 ) 2 reverse micelle. We observe a factor of 4 difference when comparing the lifetime of HOD in bulk water versus HOD in the w 0 ) 2 reverse micelle.…”

Section: Resultsmentioning

confidence: 95%

“…We observe a factor of 4 difference when comparing the lifetime of HOD in bulk water versus HOD in the w 0 ) 2 reverse micelle. The experiments presented here do not examine what fraction of the vibrational energy following relaxation goes into the water, relative to the headgroups/surfactants, and Dlott and co-workers 45 do not address the dynamics of the energy that Figure 3. Long-time pump-probe scans for w0 ) 10, 5, and 2 AOT reverse micelles.…”

Section: Resultsmentioning

confidence: 99%

“…The experiments measure the vibrational relaxation of two different fundamental transitions: the OD stretch of HOD in the experiments described in this paper and the OH stretch of H 2 O in the work presented by Dlott and co-workers. 45 Hence, direct comparisons cannot be made, because the vibrational relaxation process is dependent on the details of lower-frequency modes that are coupled to the initial vibrational excitation. The OH stretch of H 2 O can have a fundamentally different relaxation pathway than the OD stretch of HOD.…”

Section: Resultsmentioning

confidence: 99%

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Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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The dynamics of water in nanoscopic pools 1.7-4.0 nm in diameter in AOT reverse micelles were studied with ultrafast infrared spectrally resolved stimulated vibrational echo and pump-probe spectroscopies. The experiments were conducted on the OD hydroxyl stretch of low-concentration HOD in the H 2 O, providing a direct examination of the hydrogen-bond network dynamics. Pump-probe experiments show that the vibrational lifetime of the OD stretch mode increases as the size of the reverse micelle decreases. These experiments are also sensitive to hydrogen-bond dissociation and reformation dynamics, which are observed to change with reverse micelle size. Spectrally resolved vibrational echo data were obtained at several frequencies. The vibrational echo data are compared to data taken on bulk water and on a 6 M NaCl solution, which is used to examine the role of ionic strength on the water dynamics in reverse micelles. Two types of vibrational echo measurements are presented: the vibrational echo decays and the vibrational echo peak shifts. As the water nanopool size decreases, the vibrational echo decays become slower. Even the largest nanopool (4 nm, ∼1000 water molecules) has dynamics that are substantially slower than bulk water. It is demonstrated that the slow dynamics in the reverse micelle water nanopools are a result of confinement rather than ionic strength. The data are fit using time-dependent diagrammatic perturbation theory to obtain the frequency-frequency correlation function (FFCF) for each reverse micelle. The results are compared to the FFCF of water and show that the largest differences are in the slowest time scale dynamics. In bulk water, the slowest time scale dynamics are caused by hydrogen-bond network equilibration, i.e., the making and breaking of hydrogen bonds. For the smallest nanopools, the longest time scale component of the water dynamics is ∼10 times longer than the dynamics in bulk water. The vibrational echo data for the smallest reverse micelle displays a dependence on the detection wavelength, which may indicate that multiple ensembles of water molecules are being observed.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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“…Recent MD simulations and ultrafast infrared spectroscopy measurements have indeed shown position-dependent water dynamics as water molecules were distributed in different parts of reverse micelles. [116][117][118] …”

Section: Surfactant Assembliesmentioning

confidence: 99%

Ultrafast dynamics of solvation: the story so far

Nome¹

2010

J. Braz. Chem. Soc.

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A presença de moléculas de solvente na vizinhança de um soluto afeta uma variedade de processos em química e biologia, e por isso é interessante obter uma descrição física de como funciona a solvatação. Embora existam muitas ferramentas espectroscópicas estruturalmente sensíveis para a investigação do papel de moléculas de solvente em processos químicos, a medida em tempo real da dinâmica de solvatação somente tornou-se possível após o desenvolvimento de espectroscopias a laser pulsado com resolução temporal de femtossegundos. Esta revisão descreve aplicações da espectroscopia ultra-rápida ao estudo da dinâmica de solvatação. A nível de terceira ordem, discutimos a dinâmica de solvatação com técnicas ressonantes e não-ressonantes, com um foco no estudo de líquidos simples e complexos. Espectroscopias Raman de quinta ordem também são apresentadas, sendo que o enfoque dá-se no novo entendimento que estas técnicas fornecem com relação ao papel do solvente em reações químicas e à natureza anarmônica do estado líquido.The presence of solvent molecules in the vicinity of a solute affects a variety of processes in chemistry and biology, and thus one would like to have a physical picture of how solvation works. Although there are many structurally sensitive spectroscopic tools to investigate the role of solvent molecules in chemical processes, real time measurements of the dynamics of solvation had to wait for the development of pulsed laser spectroscopies with femtosecond time-resolution. This review describes applications of ultrafast spectroscopy to the study of solvation dynamics. At third order, we review resonant and non-resonant probes of solvation dynamics, with a focus on the study of simple and complex liquids. Fifth-order Raman spectroscopies are also reviewed, focusing on the insights these techniques give into the role of the solvent in chemical reactions and the anharmonic nature of the liquid state.

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A Demulsification–Crystallization Model for High‐Quality Perovskite Nanocrystals

et al. 2022

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A room‐temperature technique with all‐nonpolar‐solvent, which circumvents the sensitivity of ionic perovskite to polar solvent, has become attractive for the synthesis of metal halide perovskite nanocrystals (PNCs). However, the lack of understanding of the inner mechanism, especially for the state of the precursor and the crystallization process of the PNCs, hinders further development of this technique. Here, through systematic study of the Pb precursor and in situ characterization of the PNCs, it is revealed that the reverse micelle nature of the Pb precursor exactly creates a novel demulsification‐crystallization (D–C) model, namely, a two‐stage nucleation is divided by a demulsification process for the PNCs. On this basis, a top efficiency for green light‐emitting diodes based on PNCs is obtained with a maximum external quantum efficiency of 22.5% through tailoring the D–C model using a multiple‐acid‐anion synergistic assisted strategy to obtain high‐quality PNCs. Beyond the high efficiency, the work paves the way for diverse ideas in PNC synthesis.

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Vibrational Energy Transfer Across a Reverse Micelle Surfactant Layer

Cited by 120 publications

References 23 publications

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

Ultrafast dynamics of solvation: the story so far

A Demulsification–Crystallization Model for High‐Quality Perovskite Nanocrystals

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