Wong Bryan M
Materials Chemistry Department, Sandia National Laboratories, Livermore, California 94551.
J Phys Chem C Nanomater Interfaces. 2009 Dec 31;113(52):21921-21927. doi: 10.1021/jp9074674. Epub 2009 Dec 10.
The electronic structure and size-scaling of optoelectronic properties in cycloparaphenylene carbon nanorings are investigated using time-dependent density functional theory (TDDFT). The TDDFT calculations on these molecular nanostructures indicate that the lowest excitation energy surprisingly becomes larger as the carbon nanoring size is increased, in contradiction with typical quantum confinement effects. In order to understand their unusual electronic properties, I performed an extensive investigation of excitonic effects by analyzing electron-hole transition density matrices and exciton binding energies as a function of size in these nanoring systems. The transition density matrices allow a global view of electronic coherence during an electronic excitation, and the exciton binding energies give a quantitative measure of electron-hole interaction energies in the nanorings. Based on overall trends in exciton binding energies and their spatial delocalization, I find that excitonic effects play a vital role in understanding the unique photoinduced dynamics in these carbon nanoring systems.
利用含时密度泛函理论（TDDFT）研究了环对亚苯基碳纳米环中光电性质的电子结构和尺寸缩放。对这些分子纳米结构的TDDFT计算表明，最低激发能随着碳纳米环尺寸的增加而惊人地增大，这与典型的量子限制效应相反。为了理解它们不同寻常的电子性质，我通过分析这些纳米环系统中作为尺寸函数的电子 - 空穴跃迁密度矩阵和激子结合能，对激子效应进行了广泛研究。跃迁密度矩阵提供了电子激发过程中电子相干性的全局视图，而激子结合能给出了纳米环中电子 - 空穴相互作用能的定量度量。基于激子结合能及其空间离域的总体趋势，我发现激子效应在理解这些碳纳米环系统中独特的光诱导动力学方面起着至关重要的作用。
