We observed a similar product conversion for mixtures that were illuminated with light matching the excitation of SWCNTs and those that were stored in the dark (Figure ). This suggests that a potential oxidation of the TMB by an excited state of the SWCNT is not likely. Next, we repeated the reaction with different HRP concentrations (Figure ). As expected, we observed a concentration dependent decrease of the fluorescence. As for the PPD reactions, we observed a non-linear dependency between the responses generated with the classical and the NIR translated read-out. Based on the absorption spectra (Figure ), we first excluded the presence of TMB-I. Consequently, we assumed that only TMB and TMB-II modify the SWCNT fluorescence. Assuming substrate saturation, the TMB-II concentration [A] depends on the conversion rate (k) and the enzyme concentration [HRP]: