Characterization of Nanodiamond Seeded Interdigitated Electrodes using Impedance Spectroscopy of Pure Water

Abstract

We have recently demonstrated enhancement in sensitivity of an impedance biosensor by seeding detonation nanodiamonds (DNDs) at the interdigitated electrodes (IDEs). Here, impedance spectroscopy of pure water is carried out at such IDEs to reveal the role of the DNDs. The impedance data is fit to an equivalent circuit model consisting of a geometrical resistance in series with a distributed element for Havriliak-Negami (HN) relaxation, and in parallel with a geometrical capacitance. Concurrently, the motion of charges across the IDEs is modeled as Plank-Nerst-Poisson anomalous diffusion across two partially blocking conductive electrodes. Results show that the DNDs (having a positive zeta potential) at the IDEs reduce the geometrical resistance to less than half, and the time constant for the HN relaxation to less than one-fourth. These changes propose doubled diffusion coefficient and mobility of the charged species, and reduced dielectric relaxation time constant. The diffusion modeling suggests insignificant increase in charged mobile species upon DND seeding. It is hypothesized that the DNDs, which have a positive zeta potential, when seeded on gold and oxide surfaces with a negative zeta potential, reduce the electrostatic force acting on the diffuse layer ions, and increase their mobility.