The surface conifined interaction between TPT and dsDNA at the surface of SWCNT-PGEs was then investigated by using electrochemical impedance spectroscopy (EIS), which was a useful techique especially for the surface charactrization. The complex impedance is presented as the sum of the real and imginary components. The value of the charge transfer resistance Rct depens on the dielectric and insulating features at the electrode/electrolyte interface. A simple equivalent circuit model also used to fit the impedance data. In the nYQUIST PLOT OF IMPEDANCE SPECTRA, THE semicircle section at higher frequencies characterize the electron transfer limited process and the linear section seen at lower frequencies may be attributed to the diffusion.