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 HAuCl4 and AgNO3 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 A mu M.