The photoluminescence of single-walled carbon nanotubes may facilitate quantification of analytes within complex environments. To design quantitative sensors using carbon nanotubes, greater understanding of the optical modulation of their photoluminescence is necessary. On exploring the modulation of nanotubes, we found new methods to enable unprecedented control over the shifting of emission wavelength towards both red and blue wavelengths, facilitated by adsorbed species including biomacromolecules and polymers that allow for switchable modification of surface coverage and charge on the nanotube surface.