Jones Marcus, Metzger Wyatt K, McDonald Timothy J, Engtrakul Chaiwat, Ellingson Randy J, Rumbles Garry, Heben Michael J
Chemical and Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401-3393, USA.
Nano Lett. 2007 Feb;7(2):300-6. doi: 10.1021/nl0622808. Epub 2007 Jan 23.
We characterized the photoluminescence (PL) decay of 15 different, solubilized single-walled carbon nanotubes with tube diameters that ranged from 0.7 to 1.1 nm using time-correlated single photon counting. Each nanotube species was excited resonantly at the second excited state, E2, and PL was detected at the lowest energy exciton emission, E1. In a 10 ns window, the PL decays were described well by a biexponential fitting function with two characteristic time constants, suggesting that at least two kinetically distinct relaxation processes were observed. The dominant decay component increased from 60 to 200 ps with increasing tube diameter, while the lesser component, which contributed up to 8% of the total decay, increased from 200 ps to 4.8 ns. The observation of the second, longer decay time component is examined in terms of two possible models: an extrinsic behavior that implicates sample inhomogeneity and an intrinsic process associated with interconversion between kinetically distinct bright and dark exciton states. A common conclusion from both models is that nonradiative decay controls the PL decay by a process that is diameter dependent.
我们使用时间相关单光子计数法对15种不同的、可溶解的单壁碳纳米管的光致发光（PL）衰减进行了表征，这些纳米管的直径范围为0.7至1.1纳米。每种纳米管物种在第二激发态E2处被共振激发，并在最低能量激子发射E1处检测到PL。在10纳秒的窗口内，PL衰减通过具有两个特征时间常数的双指数拟合函数得到了很好的描述，这表明观察到了至少两个动力学上不同的弛豫过程。随着管径的增加，主要衰减成分从60皮秒增加到200皮秒，而次要成分（占总衰减的比例高达8%）从200皮秒增加到4.8纳秒。从两个可能的模型角度对第二个较长衰减时间成分的观测进行了研究：一个涉及样品不均匀性的外在行为模型，以及一个与动力学上不同的亮激子态和暗激子态之间相互转换相关的内在过程模型。两个模型的一个共同结论是，非辐射衰减通过一个与直径相关的过程控制着PL衰减。
