Spray-deposited layers of amidated carbon nanotubes (ACNTs) were characterized using AFM, Raman scattering, and spectroscopic ellipsometry. The layer thickness, diameters, and band gap of ACNTs, as well as the changes in the refractive index (n) at 1319 nm and 1625 nm after H2O and NH3 adsorption in air and H2O in N2 were analyzed in comparison with carboxylated CNTs. Modeling the resonance peak shift due to changes in n for the ACNT-coated Si waveguide microring resonator after NH3 adsorption allows us to propose the use of such a CNT layer set for integrated optical sensors for gas recognition tasks.