Ultrafast chemistry in complex and confined systems

Dutta, Partha; Bhattacharyya, Kankan

doi:10.1007/bf02708207

Cited by 13 publications

(10 citation statements)

References 97 publications

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“…Law [ 15 ] reported that solvent diffusional rotation causes shorter measured lifetimes. Multiexponential relaxation dynamics that were dominated by solvent relaxation constants were also found by Dutta and Bhattacharyya [ 79 ], who reported lifetime constants in the low picosecond range and in the low nanosecond range, whereby the nanosecond range carried significant information about the type of solvent. Hara et al .…”

Section: Engineering Aspects Of Molecular Viscometerssupporting

confidence: 65%

Environment-sensitive behavior of fluorescent molecular rotors

2010

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Molecular rotors are a group of fluorescent molecules that form twisted intramolecular charge transfer (TICT) states upon photoexcitation. When intramolecular twisting occurs, the molecular rotor returns to the ground state either by emission of a red-shifted emission band or by nonradiative relaxation. The emission properties are strongly solvent-dependent, and the solvent viscosity is the primary determinant of the fluorescent quantum yield from the planar (non-twisted) conformation. This viscosity-sensitive behavior gives rise to applications in, for example, fluid mechanics, polymer chemistry, cell physiology, and the food sciences. However, the relationship between bulk viscosity and the molecular-scale interaction of a molecular rotor with its environment are not fully understood. This review presents the pertinent theories of the rotor-solvent interaction on the molecular level and how this interaction leads to the viscosity-sensitive behavior. Furthermore, current applications of molecular rotors as microviscosity sensors are reviewed, and engineering aspects are presented on how measurement accuracy and precision can be improved.

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Section: Engineering Aspects Of Molecular Viscometerssupporting

confidence: 65%

Environment-sensitive behavior of fluorescent molecular rotors

2010

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“…Moving beyond the proximal solvent shells, force field calculations predict that solvent shell structure varies continuously, as a function of distance. − Experimentally mapping out the molecular dynamics over this coordinate is challenging. The archetypal systems to investigate solvent–surface interactions are confined volumes, such as reverse micelles, − porous silica, − and zeolites . 2D-IR studies of water in reverse micelles have shown conclusively that spectral diffusion varies continuously with the volume of the solvent pool and is not well described as a core of bulk-like solvent independent of a shell of surface-like solvent. ,,, However, these measurements invariably probe a vibrational mode on the solvent molecules, which captures spectral diffusion from molecules in all possible environments within the pore rather than providing the information as a function of distance from the wall.…”

Section: Introductionmentioning

confidence: 99%

2D-IR Spectroscopy of Porous Silica Nanoparticles: Measuring the Distance Sensitivity of Spectral Diffusion

et al. 2015

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Two-dimensional infrared spectroscopy (2D-IR) was used to investigate the sensitivity of a vibrational mode to spectral diffusion on the nanometer length scale. A confined volume within a porous silica nanoparticle was used as the model system. Utilizing a novel grafting technique, silane probes were covalently secured to the pore surface for a series of templated mesoporous silica nanoparticles with variable pore sizes. 2D-IR measurements determined that isopropanol exhibited two dominant time scales of ultrafast motions within the pores with time scales of a few picoseconds and tens of picoseconds. The unique perspective of the probe on a surface revealed that the vibrational dynamics of the reporting mode were perturbed by molecules up to ∼5 nm away. The data were modeled well by a 1/d 2 distance dependence for the coupling of solvent dynamics to frequency fluctuations and a logistic radial distribution of fast and slow dynamic populations.

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“…In particular, there have been many studies of time-dependent fluorescence (TDF). [4][5][6][7][8][9][10][11][12] In these experiments, a dye molecule with an electronic charge-transfer transition is excited and the resulting fluorescence is monitored as a function of time. The changes in fluorescence energy with time provide information about the reorganization of the solvent around the dye molecule in response to a change in its dipole moment upon excitation.…”

Section: Introductionmentioning

confidence: 99%

Smoluchowski Equation Description of Solute Diffusion Dynamics and Time-Dependent Fluorescence in Nanoconfined Solvents

Feng

Thompson

2007

J. Phys. Chem. C

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The diffusion dynamics and time-dependent fluorescence of a model dye molecule dissolved in CH 3 I, CH 3 -CN, and CH 3 OH solvents confined in nanoscale cavities and pores of 20-30 Å diameter have been modeled using a Smoluchowski equation approach. The effects of the confining framework geometry (spherical or cylindrical) and size have been investigated. The two-degree-of-freedom free-energy surfaces for the dye molecule ground and excited states are constructed from one-dimensional free-energy curves in the solute position and model force constants for a collective solvent coordinate. Multiple time scales are found in the solute diffusion after excitation and in the time-dependent fluorescence. The origins of these time scales can be understood in terms of solvent reorganization and dye molecule diffusion. The results indicate that the Smoluchowski equation approach has promise for describing time-dependent fluorescence dynamics, and ultimately reaction dynamics, in a wide variety of confined solvent systems.

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Ultrafast chemistry in complex and confined systems

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 13 publications

References 97 publications

Environment-sensitive behavior of fluorescent molecular rotors

Environment-sensitive behavior of fluorescent molecular rotors

2D-IR Spectroscopy of Porous Silica Nanoparticles: Measuring the Distance Sensitivity of Spectral Diffusion

Smoluchowski Equation Description of Solute Diffusion Dynamics and Time-Dependent Fluorescence in Nanoconfined Solvents

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