Electrochemical Impedance Spectroscopy at Nanowires for DNA Detection

Electrochemical Impedance Spectroscopy (ElS) is a method used to characterize electron-transfer reactions by perturbing the system in a sinusoidal manner over a wide range of frequencies. This method, which is very sensitive to the properties of the electrode interface, provides information regarding electron-transfer kinetics, diffusion of charged species, charging/discharging, and system conductance. 

Very recently Chen and coworkers [56] demonstrated the use of ElS for label-free electrochemical detection of DNA sequences relevant to anthrax lethal factor on gallium nitride (GaN) nanowires. The GaN nanowires were grown on a silicon substrate coated with Au catalyst using Ga as the source material and NH3 as the reactant gas in a tubular furnace via air pressure chemical vapor deposition. ElS measurements of the as grown GaN nanowires, observed in the Nyquist plot in Fig. 14.12A, exhibited a semicircle and a straight vertical line, indicative of finite impedance at the GaN/electrol3Ae 

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