Semiconducting single-walled carbon nanotubes (SWCNTs) fluoresce in the near-IR and are promising as optical sensors when functionalized to enable analyte recognition. SWCNT sensors with enhanced fluorescence emission have been hypothesized to have greater sensitivities, and reductive brightening reagents, such as dithiothreitol (DTT) and Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), enhance SWCNT brightness. The authors examine the effect of Trolox and DTT on the sensitivity of a nitric oxide (NO) sensor and report that the NO sensitivity is reduced. The NO adsorption rate decreases from 0.0007 ± 0.00003 to 0.000 3± 0.00003 and 0.0004 ± 0.0001 s-1 μM-1 upon pretreatment of 1 mM Trolox and 1 mM DTT, resp. These results are consistent with a model where Trolox and DTT are competitive binding agents with NO, occupying one of a finite no. of available SWCNT binding sites and altering the NO binding strength. In the use of brightening agents, a trade-off is predicted between signal intensity and analyte sensitivity. [on SciFinder(R)]