One-pot incorporation of quantum defects into single-walled carbon nanotubes with arylazo sulfonates

Single-walled carbon nanotubes (SWCNTs) consist of a carbon monolayer and fluoresce in the near infrared (NIR, 800-2500 nm) region. Introduction of sp3 quantum defects (QDs) creates novel NIR emission features, which promise huge potential for (bio)photonics. However, so far defect chemistry based on diazonium salts is mainly limited to benzene derivatives. The reaction side products also quench SWCNT fluorescence and impair additional surface chemistry. Here, we introduce a photochemical strategy based on arylazo sulfonates to a) create more complex aromatic QDs and b) avoid side products that adsorb and quench. We show that this way coumarin and other QDs are incorporated, which increases overall NIR emission by more than 90 % without purification. These materials can be non-covalently modified with biocompatible polymers (polyethyleneglycoles, DNA) without a change in photophysical properties and we demonstrate mechanical (viscosity) and chemical (neurotransmitter dopamine) sensing. This one-pot approach creates QDs in SWCNTs and provides access to advanced hybrid materials for photonic applications.