Polypyrrole-Silver Composite Nanowire Arrays by Cathodic Co-Deposition and Their Electrochemical Properties

A simple electrochemical one-step method of synthesis of polypyrrole-silver (PPy-Ag) nanowire arrays is presented. The method is based on simultaneous cathodic polymerization and silver electrodeposition in the nanopores of homemade porous anodic aluminum oxide (AAO) templates. The synthesized 80 nm in diameter PPy nanowires have embedded Ag nanoparticles. The nanowires are characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet-visible-near-infrared absorption spectroscopy, and electrochemical techniques. The morphology, chemical structure, and optical, electrochemical, and catalytic properties of the synthesized PPy-Ag nanowires are examined and compared with those of PPy nanowires. The effect of annealing the PPy-Ag nanowires above the glass transition temperature of polypyrrole on properties of the nanowires is studied. A surface segregation/aggregation of silver nanoparticles and degradation of polymer chain integrity occur during annealing. The as-prepared PPy-Ag and annealed PPy-Ag nanowire arrays possess enhanced catalytic activity toward electroreduction of hydrogen peroxide and can be used as novel and inexpensive sensors for its determination. The highest sensing activity is exhibited by the freshly prepared and annealed PPy-Ag nanowire electrode because of accumulation of catalytic centers on the surface of the nanowires (segregation of silver). However, the sensitivity of amperometric determination of H2O2 for the annealed PPy-Ag nanowire array decreases dramatically after storage. On the other hand, the as-prepared PPy-Ag nanowire arrays provide a stable in time sensing activity toward reduction of hydrogen peroxide. This can be attributed to a distribution of active Ag nanoparticles deep within the polymer matrix.