We also compared the ability of the photodiodes to detect intensity changes of SWCNTs in response to an analyte. For this purpose, we measured varying concentrations of the molecule levodopa, ranging from 1 nM to 100 µM, using a SWCNT biosensor functionalized with (GT)10. Despite differences in photocurrent density and SNR, the sensing properties at a SWCNT concentration of 1 nM only slightly differ (Figure ). Both photodiodes show a maximum response of 37 % at a levodopa concentration of 100 µM. For a better comparison and visualization, the data were fitted with a dose-response curve characterizing the interaction between SWCNTs and the analyte (see Equation (3), Experimental Section). The sigmoidal shapes of these curves show a similar trend with comparable dissociation constants (Kd) of 0.9 µM ± 0.4 µM for Si and 0.7 µM ± 0.3 µM for InGaAs PIN photodiodes.