Nanoporous copper microdisc arrays for non-enzymatic detection of nitrate in acidic aqueous solutions.

This work details the development of a highly sensitive, non-enzymatic nitrate sensor utilising a nanoporous copper (NPC) modified microdisc array (MDA). Fabricated via photolithography and selective electrochemical dealloying, the 3D NPC architecture provides an ultra-high electrocatalytic surface area, while the MDA confines the structure to ensure steady-state radial diffusion and actively mitigate surface fouling. Sensor performance was evaluated in an optimised acidified electrolyte (0.1 M Na2SO4, pH 2.5). The platform exhibited a distinct dual linear response: a highly sensitive diffusion-controlled regime from 1 to 100 µM (26.06 µA µM-1 cm-2) and a kinetically limited regime from 100 to 1,000 µM (10.43 µA µM-1 cm-2), achieving a low limit of detection of 2.71 µM. The sensor demonstrated robust selectivity against the majority of common drinking water interferents, though specific matrix management is required for chloride and carbonate. Finally, ageing studies revealed that while the sensor degrades in ambient air due to copper oxidation, controlled storage in acetone extends its functional lifetime to 7 days.