Smith Trevor A, Ghiggino Kenneth P
School of Chemistry, University of Melbourne, 3010 Victoria, Australia.
Methods Appl Fluoresc. 2015 Apr 28;3(2):022001. doi: 10.1088/2050-6120/3/2/022001.
Time-resolved fluorescence anisotropy measurements (TRAMs) are widely used to probe the dynamics of the various processes that can lead to the depolarisation of emission following photoselection by polarised excitation. The most commonly investigated of these emission depolarising phenomena is molecular rotational motion, but TRAMs are very useful for determining the kinetics of a host of other processes. In this paper we review several examples for which we have observed in our laboratories initially unexpectedly complex temporal behaviour of the time-resolved fluorescence anisotropy signal from relatively 'simple' chemical systems. In certain circumstances the anisotropy (i) decays on timescales when superficially it might be thought it should remain constant, (ii) shows marked 'dip and rise' behaviour in its intensity, or (iii) can change sign as the anisotropy evolves in time. Fundamentally simple processes, including molecular rotational motion, energy migration and excited state photophysics, can cause such behaviour.
时间分辨荧光 anisotropy 测量（TRAMs）被广泛用于探究各种过程的动力学，这些过程会导致在偏振激发光选后发射的去极化。这些发射去极化现象中最常研究的是分子旋转运动，但 TRAMs 对于确定许多其他过程的动力学非常有用。在本文中，我们回顾了几个例子，在我们的实验室中，最初观察到来自相对“简单”化学系统的时间分辨荧光 anisotropy 信号具有出乎意料的复杂时间行为。在某些情况下，anisotropy（i）在表面上可能认为它应该保持恒定的时间尺度上衰减，（ii）在其强度上表现出明显的“下降和上升”行为，或者（iii）随着 anisotropy 随时间演变可以改变符号。包括分子旋转运动、能量迁移和激发态光物理在内的基本简单过程会导致这种行为。
