Orientational behavior of molecular liquids in restricted geometries

Warnock, J.; Dd, Awschalom; Shafer, M. W.

doi:10.1103/physrevb.34.475

Cited by 87 publications

(61 citation statements)

References 9 publications

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“…The main focus in these investigations has been on rotational diffusion [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and solvation dynamics 20-32 employing different techniques like NMR, 5,7,[33][34][35][36] Rayleigh wing spectroscopy, 9 Raman spectroscopy, 6,14 optical Kerr effect ͑OKE͒ spectroscopy, 8,[10][11][12][15][16][17] and time resolved luminescence. The main focus in these investigations has been on rotational diffusion [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and solvation dynamics 20-32 employing different techniques like NMR, 5,7,[33]…”

Section: Introductionmentioning

confidence: 99%

Solvation dynamics of nile blue in ethanol confined in porous sol–gel glasses

Baumann

Ferrante

Deeg

et al. 2001

The Journal of Chemical Physics

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We report on solvation dynamics measurements of the chromophore nile blue in ethanol confined to sol-gel glasses with 50 Å and 75 Å average pore size and compare them with the dynamics of the respective bulk solution. Both the amplitude of the dynamic Stokes shift as well as the dynamics of the solvation process are drastically changed upon confinement. In both confined solutions the dynamic Stokes shift is reduced by a factor of about 2. As the large majority of the chromophores is adsorbed at the inner pore surfaces the solute molecules interact with only a ''half-space'' of solvent molecules. In a first approximation this decreases the stabilization energy by a factor of 2. The solvation dynamics in the confined solutions show nonexponential behavior comparable to the bulk. However, the whole solvation process slows down and the single decay time constants characterizing it increase with decreasing pore size of the sol-gel glass. We have introduced two phenomenological models to rationalize this behavior. The enhanced polarization field model takes into account the confinement and predicts a strengthening of the solvent's polarization field in an extended solvation cage induced by the electrical field of the chromophore. The steric hindrance model focuses on the interaction of the liquid with the surface reducing molecular mobility resulting in longer relaxation times. Probably both effects are of relevance in the confined solutions investigated. Confinement affects the steady-state spectra as well leading to a redshift of the absorption and a blueshift of the fluorescence. Additional data on the reorientational dynamics of the chromophore are consistent with the fact that the molecules are predominantly adsorbed at the pore surfaces.

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Section: Introductionmentioning

confidence: 99%

Solvation dynamics of nile blue in ethanol confined in porous sol–gel glasses

Baumann

Ferrante

Deeg

et al. 2001

The Journal of Chemical Physics

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“…Interest in nanometer confinement also arises from the prospect of advancing our knowledge in the field of glassforming liquids, i.e., disordered materials in their highly viscous liquid state near the glass transition temperature T g [5,6]. Because the sluggish dynamics of highly supercooled liquids are associated with inherent length scales of several nanometers [7,8], these liquids are particularly sensitive to finite size and surface effects.Porous silica glasses have been employed extensively in order to study the behavior of liquids in restricting geometries [9][10][11][12]. Jackson and McKenna have discovered that nanometer scale geometrical confinement affects the calorimetric T g of molecular glass-forming materials [13].…”

mentioning

confidence: 99%

“…Porous silica glasses have been employed extensively in order to study the behavior of liquids in restricting geometries [9][10][11][12]. Jackson and McKenna have discovered that nanometer scale geometrical confinement affects the calorimetric T g of molecular glass-forming materials [13].…”

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confidence: 99%

Intramicellar Glass Transition and Liquid Dynamics in Soft Confinement

Wang

Richert

2004

Phys. Rev. Lett.

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We explore the dynamics of viscous propylene glycol (PG) near its glass transition for the case of soft spatial confinement. The supercooled liquid is geometrically restricted by the reverse micelles of a glass-forming PG/AOT/decalin microemulsion, with the intramicellar dynamics being probed by triplet state solvation dynamics. While hard confinement by porous solids is known to result in slower dynamics and an increased glass transition temperature T(g) of PG, the nanodroplets suspended in a more fluid environment display faster structural relaxation, equivalent to a reduction of T(g) as observed in freestanding polymer films.

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“…In general terms, the orientational dynamics of wetting liquids at interfaces is expected to present important deviations with respect to the bulk behavior [1]. The pioneering results of Warnock et al studying the orientational dynamics of nitrobenzene in the pores of silica solgel glasses [12] pointed towards a biphasic behavior of the confined solvent that they separated into a bulk-like component and an interfacial one which exhibited about three times slower dynamics. Shortly after, the NMR measurements of Jonas and co-workers, also performed in silica glasses with deuterated acetonitrile and other polar solvents, also supported this shell/bulk-like core picture [37,38].…”

Section: Acetonitrilementioning

confidence: 98%

“…In order to probe the interfacial behavior using this technique, the liquids can be studied confined in nanoporous media, which provide a large and controllable surface-to-volume ratio. OKE studies performed on this kind of systems, have already proven to be a powerful tool for determining the dynamic and even structural properties of liquids at interfaces [1,[12][13][14][15]. However, these studies have been restricted so far to liquids embedded in a reduced number of silica sol-gel glasses.…”

Section: Introductionmentioning

confidence: 97%