Electrochemical Characterisation of Nanoscale Liquid jLiquid Interfaces Located at Focused Ion BeamMilled Silicon Nitride Membranes

The electrochemical behaviour of single and arrayed nanoscale interfaces between two immiscible electrolyte solutions (single and array nanoITIES) is presented. The interfaces were formed at nanopores fabricated through the focused ion beam (FIB) milling of silicon nitride (SiN) membranes by using nanopores with approximately 30-80nm radii and with pore-to-pore separations to pore radius ratios in the range of 16-32. Electrochemistry was performed through the interfacial transfer of tetrapropylammonium (TPrA(+)) across single and array nanoITIES between water and 1,6-dichlorohexane. The ion-transfer limiting current at the single nanoITIES was in excellent agreement with the current predicted by using an inlaid disc interface model. At nanoITIES arrays, experimental currents were lower than predicted for an array of inlaid interfaces, which is attributed to overlapped diffusion zones. As a result, FIB milling offers an attractive strategy to form nanoITIES for diverse investigations.