Center for Nanoscale Materials , Argonne National Laboratory , Lemont , Illinois 60439 , United States.
Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States.
ACS Nano. 2019 Nov 26;13(11):13264-13270. doi: 10.1021/acsnano.9b06279. Epub 2019 Nov 1.
Semiconducting single-walled carbon nanotubes (SWCNTs) constitute an ideal platform for developing near-infrared biosensors, single photon sources, and nanolasers due to their distinct optical and electrical properties. Covalent doping of SWCNTs has recently been discovered as an efficient approach in enhancing their emission intensities. We perform pump-probe studies of SWCNTs that are covalently doped with quantum defects and reveal strikingly different exciton formation dynamics and decay mechanisms in the presence of the defect sites. We show that, in highly doped SWCNTs, ultrafast trapping of excitons at the defect sites can outpace other photodynamic processes and lead to ground-state photobleaching of the quantum defects. Our fitting of the transient data with a kinetic model also reveals an upper limit in the quantum defect density for obtaining highly luminescent SWCNTs without causing irreversible damage. These findings not only deepen our understanding of the photodynamics in covalently doped SWCNTs but also reveal critical information for the design of bright near-infrared emitters that can be utilized in biological, quantum information, and nanophotonic applications.
半导体单壁碳纳米管（SWCNTs）由于其独特的光学和电学性质，构成了开发近红外生物传感器、单光子源和纳米激光器的理想平台。最近发现，SWCNTs 的共价掺杂是增强其发射强度的有效方法。我们对具有量子缺陷的共价掺杂 SWCNTs 进行了泵浦-探测研究，揭示了在缺陷位置存在时，激子形成动力学和衰减机制的显著差异。我们表明，在高度掺杂的 SWCNTs 中，激子在缺陷位置的超快捕获速度可以超过其他光动力过程，导致量子缺陷的基态光漂白。我们还通过动力学模型对瞬态数据进行拟合，揭示了在不造成不可逆损伤的情况下获得高发光 SWCNTs 的量子缺陷密度的上限。这些发现不仅加深了我们对共价掺杂 SWCNTs 中光动力的理解，还为设计在生物、量子信息和纳米光子学应用中可用的明亮近红外发射器提供了关键信息。
