Palladium nanoparticle-decorated iron nanotubes hosted in a polycarbonate porous membrane: development, characterization, and performance as electrocatalysts of ascorbic acid.

One-dimensional iron metallic nanotubes were prepared by electroless deposition within the pores of polycarbonate (PC) membranes. The longitudinal nucleation of the nanotubes along the pore walls was achieved by mounting the PC membrane between two halves of a U-shaped reaction tube. Palladium nanoparticles were post-deposited on the inner wall of the nanotubes. The composition, morphology, and structure of the Pd/Fe nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. A glassy carbon (GC) electrode modified with the free Pd/Fe bimetallic nanotubes (isolated after the dissolution of the host membranes) showed small improvement on the overpotential oxidation of ascorbic acid in comparison to the bare GC electrode. Alternatively, the Pd/Fe-polycarbonate membrane was covered with a sputtered gold thin layer of 10 nm from one side and mounted in a homemade electrochemical cell acting as the working electrode. The potential use of these functional membranes as catalytic surfaces for the electrochemical monitoring of ascorbic acid was investigated by cyclic voltammetry and amperometry. In the presence of a phosphate buffer solution, pH 7, Pd/Fe-polycarbonate membranes showed excellent electrocatalytic properties toward the oxidation of ascorbic acid even at potentials as low as 0 mV versus a Ag/AgCl reference electrode. In addition to the substantial lower overpotential, these electrodes offered selectivity over acetaminophen and uric acid, and a prolonged working stability without the need for maintenance. The electrodes were kept dry between different working days and retained their original activity for more than 1 week. Pd-polycarbonate and Fe-polycarbonate membranes were also developed for comparison purposes.