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首页> 外文学位 >Energy transfer dynamics in novel macrocyclic polymers: A comparative study of depolarization and exciton annihilation using ultrafast time resolved spectroscopy.
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Energy transfer dynamics in novel macrocyclic polymers: A comparative study of depolarization and exciton annihilation using ultrafast time resolved spectroscopy.

机译：新型大环聚合物中的能量转移动力学：使用超快时间分辨光谱的去极化和激子an灭的比较研究。

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摘要

It has been predicted that by the end of the century the global demand for energy will triple. Currently fossil fuels, which are an infinite source of energy, supply the majority of energy consumed globally. It has therefore been a priority for several years to find alternative energy sources. Solar energy is one such source. It is one of the most under utilized natural energy resources today. Photosynthesis is a natural biological process that utilizes the sun's energy to power vital mechanisms in plants and some species of bacteria. Uncovering and replicating the molecular level mechanism of natural photosynthesis will lead to new platforms for artificial molecular solar devices.;The dynamics and spectroscopy of a novel molecular architecture have been characterized that mimics bacterial light harvesting using a 2-D macrocyclic homopolymer. This synthetic structure has chromophore molecules pendent to a polymer backbone that are arranged in a similar cyclic topology to the biological design. The technique of ultrafast spectroscopy is used to probe the dynamics in these novel polymer systems. The results indicate the pathways and timescales for energy flow in the polymer systems.;We have characterized two independent techniques (depolarization and annihilation) that allow us to look at energy transfer dynamics over large length scales within these novel macrocyclic systems. Depolarization measurements are sensitive to the local environment of the polymer (e.g. angles between transition dipole moments) and therefore give details on the local architecture of the macrocycle. Annihilation measurements, however are sensitive to migration of two excitations over the larger chromophore array and thus provides evidence on connectivity and how energy transfer scales with the polymer size. Both techniques provide complementary evidence of the occurrence of energy transfer and the specific rates at which they occur within these macrocyclic polymer systems as well as how these time scales compare to those of natural photosynthetic systems.;The effect of excimer formation on energy transfer in the macrocyclic polymers have also been studied using time resolved fluorescence measurements. It is found that macrocycles display different excimer photophysics from their linear analogs. Further, it has been shown that excimer formation in fluorene based macrocycles was substantially reduced compared to naphthalene based macrocycles.
机译：据预测，到本世纪末，全球能源需求将增长三倍。当前，矿物燃料是一种无限的能源，它提供了全球消耗的大部分能源。因此，寻找替代能源多年来一直是优先事项。太阳能就是其中一种。它是当今使用最多的自然能源之一。光合作用是一种自然的生物过程，它利用太阳的能量来驱动植物和某些细菌物种的重要机制。揭示和复制自然光合作用的分子水平机制将为人造分子太阳能设备提供新的平台。新型分子结构的动力学和光谱学已被表征为模仿使用二维大环均聚物的细菌光收集。该合成结构具有与聚合物主链相连的生色团分子，其以与生物学设计相似的环状拓扑结构排列。超快光谱技术用于探测这些新型聚合物系统中的动力学。结果表明了聚合物系统中能量流动的途径和时标。我们已经表征了两种独立的技术（去极化和an灭），这些技术使我们能够研究这些新型大环系统中大尺度上的能量传递动力学。去极化测量对聚合物的局部环境（例如跃迁偶极矩之间的角度）敏感，因此提供了有关大环的局部结构的详细信息。然而，灭测量对两个激发在较大的生色团阵列上的迁移很敏感，因此提供了关于连通性以及能量转移如何随聚合物尺寸变化的证据。两种技术都提供了互补的证据，证明了这些大环聚合物体系中能量转移的发生以及它们发生的特定速率，以及这些时间尺度与自然光合系统的时间尺度相比如何。准分子形成对能量传递的影响还使用时间分辨荧光测量法研究了大环聚合物。发现大环与其线性类似物表现出不同的准分子光物理性质。此外，已经表明，与基于萘的大环相比，在基于芴的大环中准分子的形成显着减少。

著录项

  • 作者

    Johnson, Jerainne Michelle-Anne.;

  • 作者单位

    University of Southern California.;

  • 授予单位 University of Southern California.;
  • 学科 Chemistry Physical.;Chemistry Polymer.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 201 p.
  • 总页数 201
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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