Fractal Structures and Excitation Energy Relaxation in Molecular Assemblies

有机分子一般以自组装的形式存在。典型的例子是囊泡、LB膜和液晶，其中客体分子的取向和空间分布决定了这些组装体的宏观形态。在这项研究中，结构的顺序进行了研究，通过与皮秒时间分辨荧光光谱监测分子之间的激发能量转移。研究了聚合物和LB膜中分子的空间分布，这些分布可以用分形来表示。发现分形维数取决于分子的类型和分子间的相互作用：在硅胶微晶的表面，d = 1.7;在菁染料和罗丹明染料的LB膜中，d = 1.3 - 1.7;激发能弛豫的动力学性质的特点是能量略有不同的网站之间的跳跃迁移。

Organic molecules in general form self-assembled organizates. Typical examples are vesicles, Langmuir-Blodgett (LB) monolayr films and liquid crystals, in which some structural orders appear with respect to molecular orientation and spatial distribution of guest molecules, and determine the macroscopic morphology of these assemblies. In this study, the structural orders have been investigated by means of the excitation energy transfer between molecules monitored with a picosecond time-resolved fluorescence spectroscopy. The spatial distribution of molecules, which can be expressed in terms of "fractal", was investigated for polymers and LB films. It was found that the fractal dimension depends on (d) types of molecules, molecular inteaction : d = 1.7 in a surface of silicagel microcrystals, d = 1.3 - 1.7 in LB films of cyanine and rhodamine dyes, and d = 1.0 - 1.4 in hydrophobic plymers. The dynamical properties of excitation energy relaxation are characterized by the energy hopping migration among sites of slightly different energies.