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Solvation of Coumarin 480 within nano-confining environments: Structure and dynamics
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10.1063/1.4861586
/content/aip/journal/jcp/140/3/10.1063/1.4861586
http://aip.metastore.ingenta.com/content/aip/journal/jcp/140/3/10.1063/1.4861586

Figures

Image of FIG. 1.
FIG. 1.

Atom numbering used for Coumarin 480. The dipole moment vectors corresponding to the ground (S) and excited (S) states are also displayed on top of the molecule.

Image of FIG. 2.
FIG. 2.

Schemes of the three different confining systems in which the coumarin C480 was studied: (a) Inverse micelle CTAB/isooctane/1-hexanol/water; (b) direct CTAB micelle in water; and (c) cylindrical silica pore with CTAB and water. Typical snapshots captured during the MD simulations are shown on the right side.

Image of FIG. 3.
FIG. 3.

Local density profiles of different species for the three systems investigated: (a) Inverse micelle CTAB/isooctane/1-hexanol/water; (b) direct CTAB micelle in water; and (c) silica nanopore with CTAB and water. The coumarin densities have been multiplied by a factor of 40 for better visualization; the water densities displayed in panels (a) and (b) are divided by a factor of 10. (Notice that the water bulk value at ambient conditions is ρwat = 0.033 Å−3.) On panel (c), the dark-grey density peak corresponds to the hydrogen sites of SiOH groups at the internal surface of the pore; and the profile of CTA+ tails is multiplied by 10 for better visualization.

Image of FIG. 4.
FIG. 4.

Time evolution of the center-of-mass radial position of the coumarin, for the systems: (a) Inverse micelle; (b) direct micelle; and (c) silica pore. Note the expanded temporal scale on panel (c). The shaded regions represent the radial layer occupied by surfactant head groups. The radial distances to sites C5 (circles) and O19 (squares) of C480 are also plotted in panel (c).

Image of FIG. 5.
FIG. 5.

Time evolution of the tilt angle cos θ for the systems studied: (a) Inverse micelle; (b) direct micelle; and (c) silica pore. Note the longer scale for the -axis on panel (c).

Image of FIG. 6.
FIG. 6.

Second-rank single dipole time correlation function of Coumarin 480 in the studied systems (with symbols). Solid lines represent the fitting functions. The inset shows the curve corresponding to the SP system, on a larger time scale of 10 ns.

Image of FIG. 7.
FIG. 7.

Short-time solvation response function (), for Coumarin 480 in different environments, obtained from 500 nonequilibrium independent trajectories for each system. Dashed lines represent the fitting functions.

Image of FIG. 8.
FIG. 8.

Normalized contributions from different species, (), to the total solvation response of C480 trapped in a direct micelle (a) and in a silica nanopore (b).

Image of FIG. 9.
FIG. 9.

Comparison between the computed solvation response before [(), circles] and after convolution with a Gaussian function representing the instrument time resolution [ conv() with squares, Eq. (15) ], for (a) the direct micelle and (b) the silica pore cavity. Symbols correspond to the computed responses and lines, to the fitting functions. The Gaussian is centered at = 10 ps for the DM and at = 50 ps in the SP.

Tables

Generic image for table
Table I.

Details of the simulations.

Generic image for table
Table II.

Fitting parameters for the second-rank single-dipole TCF of C480, , and rotational times (τ) obtained by time integration of . Experimental data are also included, when available. Times are given in ps.

Generic image for table
Table III.

Solvation fitting parameters, , and solvation times (τ) obtained by time integration of (). Experimental and convoluted solvation times are also listed when available (see text). Times are given in ps.

Generic image for table
Table IV.

Solvation parameters for the solvation of C480 confined within different environments.

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/content/aip/journal/jcp/140/3/10.1063/1.4861586
2014-01-16
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Solvation of Coumarin 480 within nano-confining environments: Structure and dynamics
http://aip.metastore.ingenta.com/content/aip/journal/jcp/140/3/10.1063/1.4861586
10.1063/1.4861586
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