Biosensors are powerful tools for modern basic research and biomedical diagnostics. Their development requires substantial input from the chemical sciences. Sensors or probes with optical readout such as fluorescence offer rapid, minimally invasive sensing of analytes with high spatial and temporal resolution. The near infrared (NIR) is beneficial because of the reduced background and scattering of biological samples (tissue transparency window) in this range. In this context, single-walled carbon nanotubes (SWCNT) have emerged as versatile NIR fluorescent building blocks for biosensors. Here, we review advances of SWCNT-based NIR fluorescent molecular sensors. We review chemical design strategies for diverse analytes and summarize insights into photophysics and molecular recognition. Furthermore, different application areas are discussed from chemical imaging of cellular systems and diagnostics to in vivo applications and perspectives for the future.
