Quantifying the number of chromophores and the kinetics of exciton diffusion in nanoparticles with picosecond time-resolved photon antibunching (psTRAB)

通过研究单量子系统的荧光，如有机发色团或量子点，光的粒子性质变得最明显。假设没有双激子物质形成，在一个激发周期中不超过一个单光子被发射，即光子反聚束出现在光子统计中。在多发色团粒子中，例如捕光复合物和共轭聚合物，光子统计隐藏了关于能量转移和随后的激子湮灭过程的重要信息，但是在没有关于粒子的进一步知识（例如发色团的大小或数量）的情况下不可能解释。然而，能量转移是一个依赖于时间的过程，因此其特征必须隐藏在光子流中。我们将采用并进一步发展我们的皮秒时间分辨光子反聚束（psTRAB）技术来解开这样的签名，并证明在定义明确的multichromophoric DNA折纸结构和定义明确的multichromophoric分子，确实可以测量多个染料分子之间的能量转移过程。在第二步中，我们将把这种技术应用于各种定义不清的多发色纳米颗粒，如单一共轭聚合物链和介观共轭聚合物聚集体，它们具有不同的电子聚集行为，例如H型和J型聚集，以及不同的尺寸，以揭示这类重要材料中能量转移的性质和效率。最后，我们还想冒险进入有趣的一类单层过渡金属二硫属化物（TMDC），并研究使用psTRAB研究二维材料中激子-激子湮灭的可能性。单分子光谱学，或者更确切地说，单粒子光谱学，是显而易见的技术，因为静态和动态不均匀性都可以解决。

The particle nature of light becomes most evident by studying the fluorescence of single quantum systems, such as organic chromophores or quantum dots. Provided that there is no biexcitonic species formed, not more than one single photon is emitted in one excitation cycle, i.e. photon antibunching appears in the photon statistics. In multichromophoric particles, such as light-harvesting complexes and conjugated polymers, the photon statistics hides important information regarding energy transfer and subsequent exciton annihilation processes but is impossible to interpret without further knowledge about the particles, e.g. the size or number of chromophores. However, energy transfer is a time-dependent process and therefore the signatures thereof must be hidden in the photon stream. We will employ and further develop our technique of picosecond time-resolved photon antibunching (psTRAB) to unravel such signatures and demonstrate on well-defined multichromophoric DNA-origami structures and well-defined multichromophoric molecules that energy transfer processes between multiple dye molecules can indeed be measured. In a second step, we will apply this technique to various poorly defined multichromophoric nanoparticles, such as single conjugated polymer chains and mesoscopic conjugated polymer aggregates with distinct electronic aggregation behaviour, e.g. H- and J-type aggregation, and with different sizes to unravel the nature and efficiency of energy transfer in this important class of materials. Finally, we also want to venture into the interesting class of monolayer transition metal dichalcogenides (TMDCs) and investigate the possibility of using psTRAB to study exciton-exciton annihilation in 2D materials. Single-molecule spectroscopy, or rather single-particle spectroscopy, is the obvious technique for this because both static and dynamic heterogeneities can be resolved.