Nanostructured Cuprous-Oxide-Based Screen-Printed Electrode for Electrochemical Sensing of Picric Acid

The sensitive and selective electrochemical detection of picric acid (PA), a toxic, harmful environmental pollutant and an explosive, using different morphologies of cuprous oxide (Cu2O) is reported. The different Cu2O morphologies, synthesized by a hydrothermal method for 8h, 10h, and 12h, were characterized using various techniques to confirm their morphological, optical, compositional, and structural properties. Sensors, fabricated in the form of screen-printed electrodes using these different morphologies of Cu2O, were used to study the electrochemical sensing capabilities of the nanomaterials for PA (7.8 mu M to 10.0 mM). Cyclic voltammetry studies revealed a distinct change in the redox peak current as a function of PA concentration, which was further confirmed by electrochemical impedance spectroscopy studies, as the charge-transfer resistance increased with an increase in PA concentration. Scan rate studies showed that the electrochemical sensing of PA is a surface-controlled process, involving rapid electron transfer. Among the different morphologies, Cu2O synthesized for 8h showed a reproducible and reliable sensitivity of 130.4 mu A mM(-1)cm(-2) with a limit of detection of 39 mu M and good linearity over a wide range of PA concentrations. Interference studies with other phenolic compounds revealed the presence of distinct peaks corresponding to PA, indicating that the fabricated sensor shows specificity and selectivity for PA.