Stochastic formation of quantum defects in carbon nanotubes

16 March 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Small perturbations in the structure of materials significantly affect their properties. One example are 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 determine their photophysics. However, the presence of multiple chiralities in typical SWCNT samples complicates the identifica-tion 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 pinpoints to low numbers of defects. For bulk samples the bandgap emission (E11) of monochiral (6,5)-SWCNTs decreases and the defect related emission feature (E11*) increas-es with diazonium salt concentration and represents a proxy for the defect number. The high purity of monochiral sam-ples from ATPE allows us to image NIR fluorescence contributions (E11 = 986 nm, and E11* = 1140 nm) on the single SWCNT level. Interestingly, we observe a stochastic (Poisson) distribution of quantum defects. SWCNTs have most-likely 1 to 3 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 for the optical properties of SWCNTs. These results show that there can be a large discrepancy between ensemble and single particle experiments/properties of nanomateri-als.

Keywords

Carbon nanotubes
Quantum defects
fluorescence
microscopy

Supplementary materials

Title
Description
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Title
Stochastic formation of quantum defects in carbon nanotubes
Description
The Supporting Information contains additional absorbance and fluorescence spectra, single particle behaviors analysis.
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S1_video_SWCNT_defect reaction in E11 channel
Description
The SWCNT fluorescent intensity changes in E11 channel during quantum defect reaction
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S1_video_SWCNT_defect reaction in E11* channel
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The SWCNT fluorescent intensity changes in E11* channel during quantum defect reaction
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