Towards Monochiral Chemical Sensing with Near Infrared Fluorescent Carbon Nanotubes

Semiconducting single wall carbon nanotubes (SWCNTs) fluoresce in the near infrared (NIR) and the emission wavelength depends on their chirality (n,m). Interactions with the environment affect the fluorescence and can be tailored by functionalizing SWCNTs with biopolymers such as DNA, which is the basis for fluorescent biosensors. So far, such biosensors were mainly assembled from mixtures of SWCNT chiralities with large spectral overlap, which affects sensitivity as well as selectivity and prevents multiplexed sensing. The main challenge to gain chirality pure sensors has been to combine approaches to isolate specific SWCNTs and generic (bio)functionalization approaches. Here, we report several approaches to assemble chirality pure SWCNT-based NIR biosensors, with a major focus on aqueous two-phase extraction (ATPE) assisted purification and novel surface exchange protocols. We study the impact of SWCNT chirality/handedness on chemical sensing and highlight possible applications for detection of neurotransmitters, ROS, bacterial motives of plant metabolites. Finally, we use multiple monochiral/single-color SWCNTs as combined ratiometric/multiplexed nanosensors for NIR detection and imaging.