Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
ACS Nano. 2011 Apr 26;5(4):2611-8. doi: 10.1021/nn200427r. Epub 2011 Mar 10.
The optical properties of selectively aggregated, nearly single chirality single-wall carbon nanotubes were investigated by both continuous-wave and time-resolved spectroscopies. With reduced sample heterogeneities, we have resolved aggregation-dependent reductions of the excitation energy of the S(1) exciton and enhanced electron-hole pair absorption. Photoluminescence spectra revealed a spectral splitting of S(1) and simultaneous reductions of the emission efficiencies and nonradiative decay rates. The observed strong deviations from isolated tube behavior are accounted for by enhanced screening of the intratube Coulomb interactions, intertube exciton tunneling, and diffusion-driven exciton quenching. We also provide evidence that density gradient ultracentrifugation can be used to structurally sort single-wall carbon nanotubes by aggregate size as evident by a monotonic dependence of the aforementioned optical properties on buoyant density.
通过连续波和时间分辨光谱研究了选择性聚集的、几乎单一手性的单壁碳纳米管的光学性质。通过减少样品的异质性，我们已经解决了聚集依赖性的 S(1)激子激发能的降低以及增强的电子-空穴对吸收。光致发光光谱揭示了 S(1)的光谱分裂以及发射效率和非辐射衰减率的同时降低。观察到的与孤立管行为的强烈偏离，可以用增强的管内库仑相互作用的屏蔽、管间激子隧穿和扩散驱动的激子猝灭来解释。我们还提供了证据表明，密度梯度超速离心可以通过聚集大小对单壁碳纳米管进行结构分类，正如上述光学性质与浮力密度呈单调依赖关系所证明的那样。
