Ma Chen, Schrage C Alexander, Gretz Juliana, Akhtar Anas, Sistemich Linda, Schnitzler Lena, Li Han, Tschulik Kristina, Flavel Benjamin S, Kruss Sebastian
Department of Chemistry, Ruhr-University Bochum, Bochum 44801, Germany.
Analytical Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, Bochum 44801, Germany.
ACS Nano. 2023 Aug 22;17(16):15989-15998. doi: 10.1021/acsnano.3c04314. Epub 2023 Aug 1.
Small perturbations in the structure of materials significantly affect their properties. One example is single wall carbon nanotubes (SWCNTs), which exhibit chirality-dependent near-infrared (NIR) fluorescence. They can be modified with quantum defects through the reaction with diazonium salts, and the number or distribution of these defects determines their photophysics. However, the presence of multiple chiralities in typical SWCNT samples complicates the identification of defect-related emission features. Here, we show that quantum defects do not affect aqueous two-phase extraction (ATPE) of different SWCNT chiralities into different phases, which suggests low numbers of defects. For bulk samples, the bandgap emission (E) of monochiral (6,5)-SWCNTs decreases, and the defect-related emission feature (E*) increases with diazonium salt concentration and represents a proxy for the defect number. The high purity of monochiral samples from ATPE allows us to image NIR fluorescence contributions (E = 986 nm and E* = 1140 nm) on the single SWCNT level. Interestingly, we observe a stochastic (Poisson) distribution of quantum defects. SWCNTs have most likely one to three defects (for low to high (bulk) quantum defect densities). Additionally, we verify this number by following single reaction events that appear as discrete steps in the temporal fluorescence traces. We thereby count single reactions via NIR imaging and demonstrate that stochasticity plays a crucial role in the optical properties of SWCNTs. These results show that there can be a large discrepancy between ensemble and single particle experiments/properties of nanomaterials.
材料结构中的微小扰动会显著影响其性质。一个例子是单壁碳纳米管（SWCNT），它表现出与手性相关的近红外（NIR）荧光。通过与重氮盐反应，它们可以被量子缺陷修饰，这些缺陷的数量或分布决定了它们的光物理性质。然而，典型的SWCNT样品中存在多种手性，这使得识别与缺陷相关的发射特征变得复杂。在这里，我们表明量子缺陷不会影响不同手性的SWCNT在水相两相萃取（ATPE）中进入不同相，这表明缺陷数量较少。对于块状样品，单手性（6,5）-SWCNT的带隙发射（E）降低，与缺陷相关的发射特征（E*）随着重氮盐浓度的增加而增加，并且代表了缺陷数量的一个指标。通过ATPE获得的高纯度单手性样品使我们能够在单根SWCNT水平上成像近红外荧光贡献（E = 986 nm和E* = 1140 nm）。有趣的是，我们观察到量子缺陷的随机（泊松）分布。SWCNT最有可能有一到三个缺陷（对于低到高（块状）量子缺陷密度）。此外，我们通过跟踪在时间荧光轨迹中表现为离散步骤的单个反应事件来验证这个数量。我们由此通过近红外成像对单个反应进行计数，并证明随机性在SWCNT的光学性质中起着至关重要的作用。这些结果表明，纳米材料的整体和单粒子实验/性质之间可能存在很大差异。
