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Issue 5, 2011
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Probe dependence of spatially heterogeneous dynamics in supercooled glycerol as revealed by single molecule microscopy

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Abstract

Spatially heterogeneous dynamics in supercooled glycerol over the temperature range 198 K (1.04Tg) − 212 K (1.12Tg) is investigated using widefield single molecule (SM) fluorescence microscopy. Measurements are performed using three different perylenedicarboximide probes to investigate whether probe size and probe–host interactions affect breadth of heterogeneity reported in the glassy host by such SM experiments. Rotational relaxation times of single probe molecules are measured, and for all probes, log-normal distributions of relaxation times are found. No significant change in relaxation time distribution as a function of temperature is evident for a given probe. However, across probes, probe rotational relaxation time is correlated with breadth of heterogeneous dynamics reported. Molecules that undergo changes in dynamics are identified using two complementary approaches that interrogate time scales between 103 and 106τα,with τα the structural relaxation time of glycerol. Exchange is found on the shortest time scales probed (∼30 τc, with τc the rotational correlation time of the probe) and is relatively temperature and probe independent. No evidence is found for additional exchange occurring on the longest time scales interrogated. Taken together with the fact that probes that rotate the fastest report the greatest breadth of spatially heterogeneous dynamics in the system, this indicates that exchange times reported from analysis of SM linear dichroism trajectories as described here are upper bounds on the average exchange time in the system.

Graphical abstract: Probe dependence of spatially heterogeneous dynamics in supercooled glycerol as revealed by single molecule microscopy

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Publication details

The article was received on 18 Sep 2010, accepted on 29 Oct 2010 and first published on 26 Nov 2010


Article type: Paper
DOI: 10.1039/C0CP01860K
Citation: Phys. Chem. Chem. Phys., 2011,13, 1786-1799
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    Probe dependence of spatially heterogeneous dynamics in supercooled glycerol as revealed by single molecule microscopy

    S. A. Mackowiak, L. M. Leone and L. J. Kaufman, Phys. Chem. Chem. Phys., 2011, 13, 1786
    DOI: 10.1039/C0CP01860K

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