Transistor characteristics of a biotinylated SWNT FET before (black) and after (red) NeutrAvidin adsorption, measured at pH 3.4 (a) and at pH 6.3 (b). (c) Transfer characteristics of an unfunctionalized device before (black) and after (red) NeutrAvidin adsorption measured at pH 6.5. (d) Normalized sensor response ( I 0 – I P )/ g m of pyrene-biotin-functionalized SWNT FET toward NeutrAvidin (blue) and streptavidin (gray) under different buffer concentrations as a function of buffer pH. The protein response was measured in 1.6–2 mM buffer (triangles) and 0.8–0.9 mM buffer (circles) concentrations. Error bars result from averaging responses of several devices. The solid lines represent sigmoidal Boltzmann fits.
{}