Transparent microelectrode array in diamond technology

We report on the development of a diamond-on-sapphire microelectrode quadrupole array, substituting the commonly used inert metal electrode material by nanocrystalline diamond (NCD). This allows to combine the transparency (desired for fluorescence analysis) with the properties of an inert quasi-metallically doped diamond electrode. The NCD film was nucleated by BEN (Bias Enhanced Nucleation) on double side polished sapphire substrates and outgrown by hot filament CVD. Early quadrupole results on isolated adrenal chromaffin cells show the detection of amperometric signals corresponding to the quantal release of catecholamines contained in a single nanometric secretory vesicle.