Flexible screen-printed nitrate sensors with Cu nanoclusters: a comparative analysis on the effect of carbon nanotubes

In this work, we present a novel flexible amperometric sensor for nitrate detection, based on a silver (Ag) working electrode modified with single-walled carbon nanotubes (SWCNTs) and copper (Cu). A simple and low-cost fabrication technique combining printing and electrochemical deposition was used: after spray deposition of SWCNTs on the screen-printed Ag working electrode, Cu was electrodeposited. The electrochemical performance of our sensors was analyzed and compared to reference sensors fabricated without SWCNTs (Cu/Ag), proving the capability of SWCNTs to improve the sensitivity and the performance of the sensors thanks to the increased electroactive surface area. In fact, the Cu/SWCNTs/Ag sensors showed higher catalytic activity towards the electro-reduction of nitrate (sensitivity: 18.19 µA/mM), as well as a lower limit of detection (LOD: 0.281 nM) in comparison to the Cu/Ag sensors (sensitivity: 12.19 µA/mM and LOD: 0.381 nM). Full sensor functionality after repetitive mechanical bending to 5 mm radius was also proven.