Flexible Screen-Printed Amperometric Sensors Functionalized With Spray-Coated Carbon Nanotubes and Electrodeposited Cu Nanoclusters for Nitrate Detection

In this work, we present a novel, sensitive, easy-to-fabricate, flexible amperometric sensor constituted by screen-printed silver (Ag) electrodes functionalized with a copper (Cu) film electrodeposited on top of a spray coated network of single-walled carbon nanotubes (SWCNTs). The Cu/SWCNTs/Ag electrode showed excellent catalytic activity towards the electro-reduction of nitrate ions at neutral pHwith a significant increasein cathodicpeak currents incomparison with the electrode without SWCNTs (Cu/Ag). The developed Cu/SWCNTs/Ag sensor showed a wide linear detection range from
$0.5~ \mu \rm{M}$
to 6.0 mM (0.31 mg/l to 372.02 mg/l) with good sensitivity (18.39
$\mu$
A/mM) and a calculated limit of detection (LOD) of 0.166 nM(10.29
$\mu$
g/l). It also showed a good selectivity (maximum standard deviation (SD) was 3.25
$\mu$
A) towards different interfering ions (Fe2+, Na+, Cu2+, SO2−4, CH3COO−, Cl−, NO−2 and HCO−3), as well as good reproducibility,mechanical durability, time and temperature stability. In real sample analysis (tap and river water), the sensor exhibited good agreement with the compared outcome of high-performance liquid chromatography (HPLC) measurements, proving to be a promising analytical tool for the detection of nitrate in water.