Nanodiamond macro- and microelectrode array bio-sensor

A thin-film nanodiamond macro-electrode and a microelectrode array (MEA) with SiO₂ film as the insulator, both on a highly doped silicon substrate were fabricated for biosensing applications. Fe(CN)^3-/4- ₆ redox couple is used for electrochemical characterization of the MEA using cyclic voltammetry, which gives a sigmoidal response consistent with hemispherical diffusion limited mass transport mechanism. Using the nanodiamond MEA, we were also able to detect different concentrations of dopamine in phosphate buffered saline (pH 7.4) without any surface functionalization. The cyclic voltammograms show a steady state response and a linear relationship between the limiting current and dopamine concentration. In contrast, the nanodiamond macro-electrode shows a peak shaped response due to semi-infinite linear diffusion of the analytes. Overall, the nanodiamond MEA has a larger analyte flux and thereby larger current density by virtue of its small area as compared to the macro-electrode making it more sensitive for detection of dopamine and other bio-analytes.