Issue 5, 2011

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

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

Supplementary files

Article information

Article type
Paper
Submitted
18 Sep 2010
Accepted
29 Oct 2010
First published
26 Nov 2010

Phys. Chem. Chem. Phys., 2011,13, 1786-1799

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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