The optical absorbance and fluorescence of single-wall carbon nanotubes have peaks that represent band-gap absorbance and photoluminescence (PL). Peak location (and intensity for PL) in the spectrum is very sensitive to the local environment, a solvatochromic effect. We use this effect to study the kinetics of displacing biological molecules from the surface of CNTs.
Roxbury, Daniel, Shao-Qing Zhang, Jeetain Mittal, William F. DeGrado, and Anand Jagota. “Structural Stability and Binding Strength of a Designed Peptide-Carbon Nanotube Hybrid.” The Journal of Physical Chemistry C (2013).
We have also used such spectroscopy to quantify DNA/SWCNT solvation differences using Aqueous Two Phase Separation.
Yang, Yoona, Akshaya Shankar, Thibault Aryaksama, Ming Zheng, and Anand Jagota. “Quantification of DNA/SWCNT Solvation Differences by Aqueous Two-Phase Separation.” Langmuir 34, no. 5 (2018): 1834-1843.
See pictures below: