Synthesis, characterization, and application of Au–Ag alloy nanoparticles for the sensing of an environmental toxin, pyrene

Bimetallic alloy nanoparticles (NPs) of two coinage metals, Au and Ag, were successfully synthesized by a co-precipitation method. These NPs were prepared by a chemical method involving the reduction of HAuCl 4 and AgNO 3 in an aqueous solution of 2 % hydrazine as a reducing agent, iso-octane as a co-precipitator, cetyl trimethyl ammonium bromide as a capping agent, and deionized water as a solvent. The newly synthesized bimetallic alloy NPs were characterized by electronic absorption spectroscopy. The NPs were further characterized by scanning electron microscopy, transmission electron microscopy (TEM), and energy-dispersive spectroscopy. TEM evidenced the formation of NPs with a diameter ranging from 25 to 35 nm. For the development of electrochemical sensor, glassy carbon electrode (GCE) was modified with potentiodynamic polymerization of pyrrole, called polypyrrole (PPy). PPy was over-oxidized in order to increase its sensitivity toward polyaromatic hydrocarbons. The electrode was further modified with Au–Ag bimetallic alloy NPs. The fabricated GCE was successfully applied to detect an environmental toxin, pyrene. The electrochemical behavior of pyrene at the composite electrode (PPyox/Au–Ag NPs/GCE) was optimized by changing the atomic ratio of Au and Ag in Au–Ag bimetallic alloy NPs. At the Au and Ag ratio of 1:3, pyrene was detected with a detection limit of 0.1 µM.