A sensitive electrochemical nitrate sensor based on polypyrrole coated palladium nanoclusters

•The Pd NCs-PPy were synthesized by direct reduction of palladium cations.•The performance of Pd NCs-PPy toward nitrate sensing at pH 7 was investigated.•The calibration curve showed two linear segments of nitrate concentration.•The sensitivity of the low concentration of the calibration curve was 0.124 μA μM−1 cm−2.•The LOD of low and high concentration was 0.744 and 0.453 μM, respectively.

This study examines the synthesis and characterization of polypyrrole coated palladium nanocluster (Pd NCs-PPy) composites and their application in nitrate detection at pH = 7.0. The synthesis was performed via the direct reduction of an aqueous solution of Pd (CH3COO)2 in the presence of pyrrole monomers in NaOH. X-ray diffraction and field emission scanning electron microscopy observations showed that the Pd cations were completely reduced to Pd with the formation of Pd NCs-PPy cluster morphology, respectively. Electrochemical properties of the Pd NCs-PPy electrode were studied by differential pulse voltammetry (DPV), cyclic voltammetry and electrochemical impedance spectroscopy. From the DPV results, the estimated limit of detection, limit of quantification (S/N = 3) for the two linear segments (lower and higher concentration of nitrate) are 0.7444, 2.4815 and 0.4535, 1.5117 μM, respectively. The sensitivity of these two linear segments is 0.124 and 0.204 μA μM−1 cm−2, respectively. Results from the reproducibility experiments show that the Pd NCs-PPy is feasible for the quantitative determination of certain concentration ranges of nitrate.