Yang Jian, Winnik Mitchell A
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
J Phys Chem B. 2005 Oct 6;109(39):18408-17. doi: 10.1021/jp053204g.
We describe Monte Carlo simulations of resonance energy transfer (RET) experiments for immobile donor (D) and acceptor (A) dyes confined to planar, cylindrical, and spherical restricted geometries. We compare values of the quantum efficiency (PhiET) evaluated through consideration of individual donor-acceptor pairs, with values calculated assuming a pre-averaged value of the orientation parameter /kappa/2 = 0.476 appropriate for infinite three dimensional (3D) space. For dyes confined to restricted geometries where the length scale of the confining dimension is less than or equal to the Förster radius R0, the coupling of the orientation parameter and the donor-acceptor distance becomes noticeable. Values of Phi(ET) obtained by proper consideration of the orientation parameter are smaller than those calculated using /kappa/2 = 0.476. We use this Monte Carlo method to reanalyze the fluoresce decay measured from dye-labeled poly(isoprene-b-methyl methacrylate) diblock copolymer with lamellar structure,(1) from which the interface thickness for PI-PMMA lamella can be retrieved. We found the retrieved interface thickness is sensitive to the choice of dipole orientation. If all dipoles in the confined polymer interface have a random orientation, the value of interface thickness was found to be 0.9 +/- 0.2 nm through consideration of individual dipole orientations. Assumption of /kappa/2 = 0.476 in the FRET calculations leads to a larger value of interface thickness (1.3 +/- 0.2 nm) due to the neglect of the coupling between dipole orientation and D-A distance for the dyes confined to lamellar interfaces.
我们描述了针对固定在平面、圆柱和球形受限几何结构中的供体（D）和受体（A）染料的共振能量转移（RET）实验的蒙特卡罗模拟。我们将通过考虑单个供体 - 受体对评估的量子效率（PhiET）值，与假设取向参数/kappa/2 = 0.476的预平均值得出的值进行比较，该值适用于无限三维（3D）空间。对于限制在受限几何结构中的染料，其中限制维度的长度尺度小于或等于福斯特半径R0，取向参数与供体 - 受体距离之间的耦合变得明显。通过适当考虑取向参数获得的Phi(ET)值小于使用/kappa/2 = 0.476计算的值。我们使用这种蒙特卡罗方法重新分析了从具有层状结构的染料标记的聚（异戊二烯 - b - 甲基丙烯酸甲酯）二嵌段共聚物测量的荧光衰减，（1）从中可以获取PI - PMMA薄片的界面厚度。我们发现获取的界面厚度对偶极子取向的选择敏感。如果受限聚合物界面中的所有偶极子具有随机取向，通过考虑单个偶极子取向，发现界面厚度的值为0.9 +/- 0.2 nm。在FRET计算中假设/kappa/2 = 0.476会导致界面厚度值更大（1.3 +/- 0.2 nm），这是因为忽略了限制在层状界面中的染料的偶极子取向与D - A距离之间的耦合。
