Orientational relaxation and vibrational excitation transfer in methanol–carbon tetrachloride solutions

Gaffney, Kelly J.; Piletic, Ivan R.; Fayer, M. D.

doi:10.1063/1.1534580

Cited by 99 publications

(125 citation statements)

References 55 publications

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“…These two types of OH stretches are frequently observed in alcohol/CCl 4 solutions. 19,20 In the crystal or on the surface of nanoparticles, the sharp free OH stretch peak almost completely disappears. Only the broad band exists.…”

Section: Resultsmentioning

confidence: 99%

Molecular Conformations and Dynamics on Surfaces of Gold Nanoparticles Probed with Multiple-Mode Multiple-Dimensional Infrared Spectroscopy

Bian

Chen

et al. 2012

J. Phys. Chem. C

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Knowledge about molecular conformations and nuclear and electronic motions on surfaces of metal nanomaterials is critical for many applications but extremely difficult to obtain. We demonstrate that valuable information of this sort can be determined using multiple-mode multiple-dimensional vibrational spectroscopy. A model compound, 4-mercaptophenol, on the surface of 3.5 nm gold nanoparticles demonstrates the method. Its 3D molecular conformations and vibrational dynamics on the particle surfaces were determined with the method. The experimental results imply that on the particle surfaces, the ligand molecules cannot form energy-optimized hydrogen bonds because of the surface geometry constraint. The conclusion is supported with experiments on the ligand molecules in the crystalline phase and in a dilute solution. Our experiments also showed that the effect of the particle surface nonadiabatic electron/vibration coupling does not play a significant role in the vibrational relaxation of high-frequency modes (>1000 cm −1 ) about 3 Å away from the surface. Simple theoretical calculations support this observation. The method holds promise as a general tool for the studies of molecular structures and dynamics on the surfaces of nanomaterials. The capability of resolving 3D molecular conformations on nanomaterials surfaces is expected to be helpful for understanding specific intermolecular interactions and conformation-selective reactions (e.g., chirality selectivity) on the surfaces of these materials.

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Section: Resultsmentioning

confidence: 99%

Molecular Conformations and Dynamics on Surfaces of Gold Nanoparticles Probed with Multiple-Mode Multiple-Dimensional Infrared Spectroscopy

Bian

Chen

et al. 2012

J. Phys. Chem. C

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“…First, it is a single local mode, which simplifies the absorption spectrum (24,25). Second, of considerable importance for the time resolved experiments is the fact that measurements on the OD stretch of dilute HOD in H 2 O eliminate vibrational excitation transfer (26). We are interested in the ground-state equilibrium properties of the aqueous solutions.…”

Section: Resultsmentioning

confidence: 99%

Hydrogen bond dynamics in aqueous NaBr solutions

Park

Fayer

2007

Proc. Natl. Acad. Sci. U.S.A.

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295

403

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Hydrogen bond dynamics of water in NaBr solutions are studied by using ultrafast 2D IR vibrational echo spectroscopy and polarization-selective IR pump-probe experiments. The hydrogen bond structural dynamics are observed by measuring spectral diffusion of the OD stretching mode of dilute HOD in H2O in a series of high concentration aqueous NaBr solutions with 2D IR vibrational echo spectroscopy. The time evolution of the 2D IR spectra yields frequency-frequency correlation functions, which permit quantitative comparisons of the influence of NaBr concentration on the hydrogen bond dynamics. The results show that the global rearrangement of the hydrogen bond structure, which is represented by the slowest component of the spectral diffusion, slows, and its time constant increases from 1.7 to 4.8 ps as the NaBr concentration increases from pure water to Ϸ6 M NaBr. Orientational relaxation is analyzed with a wobbling-in-a-cone model describing restricted orientational diffusion that is followed by complete orientational randomization described as jump reorientation. The slowest component of the orientational relaxation increases from 2.6 ps (pure water) to 6.7 ps (Ϸ6 M NaBr). Vibrational population relaxation of the OD stretch also slows significantly as the NaBr concentration increases.ultrafast 2D IR spectroscopy ͉ water dynamics in ionic solutions W ater plays an important role in chemical and biological processes. In aqueous solutions, water molecules dissolve ionic compounds, charged chemical species, and biomolecules by forming hydration shells (layers) around them. Pure water undergoes rapid structural evolution of the hydrogen bond network that is responsible for water's unique properties (1). A question of fundamental importance is how the dynamics of water in the immediate vicinity of an ion or ionic group differ from those of pure water. For monatomic ions, molecular ions, charged groups of large molecules, or charged amino acids on the surfaces of proteins, the basic structure of hydration shells is determined by ion-dipole interactions between water molecules and the charged group (2, 3). Such ion-dipole interactions will influence both the structure and dynamics of water in the proximity of ions. Water dynamics in ion hydration shells play a significant role in the nature of systems such as proteins and micelles (3) and in processes such as ion transport through transmembrane proteins (4).Over the last several years, the application of ultrafast IR vibrational echo spectroscopy (5, 6), particularly 2D IR vibrational echo experiments, (7, 8) combined with molecular dynamics (MD) simulations (9-12) have greatly enhanced understanding of the hydrogen bond dynamics in pure water. These experiments directly examine the dynamics of water rather than study the indirect influence of water dynamics on a probe molecule (13). The ultrafast 2D IR vibrational echo experiments on water (7, 8) and other hydrogen-bonded systems (14) build upon earlier IR pump-probe experiments that have been extensively used to study ...

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“…The OD hydroxyl stretch of dilute HOD in H 2 O is studied rather than pure H 2 O or D 2 O to eliminate vibrational excitation transfer (33,34). Vibrational excitation transfer changes the spatial location of the excitation causing the decay of the transition dipole anisotropy (35), which interferes with orientational relaxation measurements and will artificially contribute to chemical exchange.…”

Section: Resultsmentioning

confidence: 99%

Ion–water hydrogen-bond switching observed with 2D IR vibrational echo chemical exchange spectroscopy

Moilanen

Wong

Rosenfeld

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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233

318

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The exchange of water hydroxyl hydrogen bonds between anions and water oxygens is observed directly with ultrafast 2D IR vibrational echo chemical exchange spectroscopy (CES). The OD hydroxyl stretch of dilute HOD in H 2O in concentrated (5.5 M) aqueous solutions of sodium tetrafluoroborate (NaBF 4) displays a spectrum with a broad water-like band (hydroxyl bound to water oxygen) and a resolved, blue shifted band (hydroxyl bound to BF 4 ؊ ).At short time (200 fs), the 2D IR vibrational echo spectrum has 4 peaks, 2 on the diagonal and 2 off-diagonal. The 2 diagonal peaks are the 0 -1 transitions of the water-like band and the hydroxylanion band. Vibrational echo emissions at the 1-2 transition frequencies give rise to 2 off-diagonal peaks. On a picosecond time scale, additional off-diagonal peaks grow in. These new peaks arise from chemical exchange between water hydroxyls bound to anions and hydroxyls bound to water oxygens. The growth of the chemical exchange peaks yields the time dependence of anionwater hydroxyl hydrogen bond switching under thermal equilibrium conditions as T aw ‫؍‬ 7 ؎ 1 ps. Pump-probe measurements of the orientational relaxation rates and vibrational lifetimes are used in the CES data analysis. The pump-probe measurements are shown to have the correct functional form for a system undergoing exchange.2D IR spectroscopy ͉ hydration of ions ͉ hydrogen bond dynamics ͉ ion hydrogen bonds chemical exchange ͉ ionic solutions W ater interacting with ions occurs in a wide variety of systems ranging from ocean salt water to water interacting with charged amino acids at the surfaces of proteins (1). The properties of pure liquid water are determined by the nature of its hydrogen bond network. A water molecule can have as many as 4 hydrogen bonds with other water molecules, forming an approximately tetrahedral structure. The pure water hydrogen bond network is constantly evolving with a range of time scales from tens of femtoseconds to picoseconds (2-5). Hydrogen bonds are continually forming and breaking through concerted hydrogen bond rearrangements (6). These dynamical processes can be observed on the time scale they occur in considerable detail by using ultrafast infrared spectroscopy. Measurements of spectral diffusion, described in terms of the frequencyfrequency correlation function (FFCF), by using ultrafast 2D IR vibrational echo spectroscopy (3,7,8) as well as other ultrafast IR techniques (4, 5) have determined the multiple time scales for the hydrogen bond dynamics. The slowest time component of the FFCF (1.7 ps) is associated with the randomization of the hydrogen bond network through concerted hydrogen bond rearrangements. The orientational relaxation time of pure water (2.6 ps) (2, 5) is also assigned to concerted hydrogen bond rearrangement via jump reorientation (6).In aqueous salt solutions the structure of water is modified in the vicinity of the ions as the water oxygens preferentially solvate the cations and the water hydroxyls solvate the anions (9, 10). The structures of the hyd...

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Orientational relaxation and vibrational excitation transfer in methanol–carbon tetrachloride solutions

Cited by 99 publications

References 55 publications

Molecular Conformations and Dynamics on Surfaces of Gold Nanoparticles Probed with Multiple-Mode Multiple-Dimensional Infrared Spectroscopy

Molecular Conformations and Dynamics on Surfaces of Gold Nanoparticles Probed with Multiple-Mode Multiple-Dimensional Infrared Spectroscopy

Hydrogen bond dynamics in aqueous NaBr solutions

Ion–water hydrogen-bond switching observed with 2D IR vibrational echo chemical exchange spectroscopy

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