Sensitive Dopamine Biosensor Based on Polypyrrole-Coated Palladium Silver Nanospherical Composites

We report a facile synthesis of polypyrrole-coated palladium silver nanospherical (PdAg NSPs-PPy) composites via direct reduction of Pd2+ and Ag+ in the presence of pyrrole monomers from an aqueous solution of Pd(CH3COO)2, AgNO3, and NaOH. The nanocomposites were synthesized with different ratios of Pd and Ag (2:1, 1:1, and 1:2). X-ray diffraction shows that the Pd2+ and Ag+ were completely reduced to Pd and Ag, respectively, during the formation of PdAg NSPs-PPy. The modified glassy carbon electrode with the Pd2Ag1 NSPs-PPy demonstrated excellent electrochemical activity toward dopamine oxidation compared with the bare GCE, Pd1Ag1 NSPs-PPy, and Pd1Ag2 NSPs-PPy. From the differential pulse voltammetry results, the estimated limit of detection (S/N = 3) and limit of quantification (S/N = 10) for the linear segment (0.001–200 μM of dopamine) are 0.0258 and 0.0860 μM, respectively.