Abstract We propose a reliable and accurate method that uses ultraviolet–visible–near infrared absorbance to measure the isotropic-cloud point (ICP) of carbon nanotube (CNT)/chlorosulfonic acid (CSA) solutions. This information is necessary to improve understanding of the isotropic-to-nematic transition of CNT/CSA solutions and to guide solution processing and characterization of CNTs. In this method, the ICP of CNT/CSA solutions is defined as the CNT concentration at which the absorbance at 600 nm is saturated. This wavelength was selected as suitable by considering the resonance ratio and mass absorption coefficient. The reliability of the method was tested by comparing the ICPs measured using this method to those measured by a method that uses polarized optical microscopy and by a method that uses centrifugation. The results obtained using the three methods were consistent. An inverse proportionality between the ICP of CNT/CSA solutions and the CNT aspect ratio (AR) was confirmed; this result further confirms the reliability of our method. The AR of unknown CNTs can be predicted from the ICP of a CNT/CSA solution. Hence, this method provides a new tool to estimate the AR of unknown CNTs.

中文翻译：

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使用 UV-vis-NIR 吸收饱和行为测定碳纳米管/氯磺酸溶液的各向同性浊点

摘要 我们提出了一种可靠且准确的方法，该方法使用紫外-可见-近红外吸收来测量碳纳米管 (CNT)/氯磺酸 (CSA) 溶液的各向同性浊点 (ICP)。这些信息对于提高对 CNT/CSA 溶液的各向同性到向列相转变的理解以及指导 CNT 的溶液处理和表征是必要的。在该方法中，CNT/CSA 溶液的 ICP 定义为 600 nm 处吸光度饱和时的 CNT 浓度。通过考虑共振比和质量吸收系数选择合适的波长。该方法的可靠性是通过将使用这种方法测量的 ICP 与使用偏振光学显微镜的方法和使用离心的方法测量的 ICP 进行比较来测试的。三种方法得到的结果是一致的。证实了 CNT/CSA 溶液的 ICP 与 CNT 纵横比 (AR) 之间成反比；这一结果进一步证实了我们方法的可靠性。未知 CNT 的 AR 可以从 CNT/CSA 溶液的 ICP 预测。因此，该方法提供了一种新的工具来估计未知碳纳米管的 AR。