Which probes can report intrinsic dynamic heterogeneity of a glass forming liquid?
Which probes can report intrinsic dynamic heterogeneity of a glass forming liquid?
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DOI：
10.1063/1.5047215
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发表时间：
2018-10-28
影响因子：
4.4
通讯作者：
Kaufman, Laura J.
中科院分区：
文献类型：
--
作者：
Paeng, Keewook;Kaufman, Laura J.
使用外源性探针研究宿主系统依赖于探针准确报告所研究的宿主性质的能力。长期以来，探针一直被用来表征动态不均匀性，即接近玻璃化转变的液体表现出作为时间和位置函数的不同动力学现象，彼此在纳米范围内的分子表现出可能按数量级变化的动力学。动态异质性的空间和时间特性要求使用严格的标准来选择探针，它们的大小和动态。在这份报告中，我们研究了动态异质性的原型分子玻璃前邻三联苯通过调查单分子旋转的两个不同大小的二萘嵌苯二甲酰亚胺探针分子，并比较这与以前获得的结果与探针BODIPY 268。据发现，探针的能力，准确地报告动态异质性邻三联苯取决于是否报告的动态分布重叠与主机的内在动力学，这是自然相关的内在动力学的宽度和探针动态相对于主机的动态偏移的幅度。我们发现，一个探针，旋转约15倍更慢的内在动力学的主机o-terphenyl感测最慢的约5%的完整的动态异质性，而一个旋转约65倍更慢的主机未能报告动态异质性的主机。由AIP出版社出版。
Using extrinsic probes to study a host system relies on the probes' ability to accurately report the host properties under study. Probes have long been used to characterize dynamic heterogeneity, the phenomenon in which a liquid near its glass transition exhibits distinct dynamics as a function of time and position, with molecules within nanometers of each other exhibiting dynamics that may vary by orders of magnitude. The spatial and temporal characteristics of dynamic heterogeneity demand the selection of probes using stringent criteria on their size and dynamics. In this report, we study the dynamic heterogeneity of the prototypical molecular glass former o-terphenyl by investigating single molecule rotation of two perylene dicarboximide probe molecules that differ in size and comparing this to results obtained previously with the probe BODIPY268. It is found that a probe's ability to accurately report dynamic heterogeneity in o-terphenyl depends on whether the reported distribution of dynamics overlaps with the intrinsic dynamics of the host, which is naturally related to the width of the intrinsic dynamics and the magnitude of dynamical shift in probe dynamics relative to the host. We show that a probe that rotates approximate to 15 times more slowly than the intrinsic dynamics of the host o-terphenyl senses the slowest approximate to 5% of the full dynamic heterogeneity whereas one that rotates approximate to 65 times more slowly than the host fails to report dynamic heterogeneity of the host. Published by AIP Publishing.