A Surface Network Based on Polytyramine/ Gold Nanoparticles: Characterization, Kinetics, Thermodynamics and Selective Determination of Norepinephrine : A SURFACE NETWORK BASED ON POLYTYRAMINE/GOLD NANOPARTICLES

A solid-state sensor was fabricated by a spontaneous electrochemical deposition of polytyramine (Ptyr) film onto a glassy carbon electrode (GCE) which was further peripherally supported by gold nanoparticles (AuNPs). The surface materials of the developed sensor (AuNPs.Ptyr-GCE) were characterized by X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The rate constant of charge transfers (kct) of the as-prepared sensor (8.77 × 10-4 cm/s) was evaluated by fitting the charge transfer resistance (Rct) data in the presence of ferric-ferrous hexacyanide redox couple solution, [Fe(CN)6]3-/4-. The voltammetric behavior of norepinephrine (NOR) was confirmed to follow an irreversible reaction mechanism at which the estimated diffusion coefficient value was 7.39 × 10-5 cm2/s. The sensor showed a large enhancement on NOR oxidation and comparatively lowered its detection limit (DL3s) to 0.130 mM (22 ppb). It was also applied for selective determination of NOR in the presence of high concentrations of ascorbic acid (AA) and uric acid (UA). The interference study highlighted the great stability of the proposed sensor by generating a similar sensitivity as in the pure NOR solution. The analytical performance of the proposed system was validated successfully for pharmaceutical and biological samples with tolerable recovery percentages

Fabrication and surface characterization of poly(4-aminodiphenylamine) film modified electrode and its application for lead and cadmium determination

Poly(4-aminodiphenylamine), Padpa, film was synthesized electrochemically on a glassy carbon electrode by potentiodynamic repetitive cycling of 4‑aminodiphenylamine (4adpa) in 1.0 M HCl. The mechanistic steps involved the oxidation of the protonated monomer to  diimine species which underwent dimerization process to form the mono-charged radical intermediate which was considered as the initiation step for the progress of polymerization. The electrochemical properties and surface morphology of the film modified electrode were characterized using electrochemical and various surface scanning techniques. The XPS data demonstrated the existence of (=N-) bonding responsible for polymer formation, while the AFM image revealed a uniform and symmetrical fiber structure with low energy dissipation. The modified electrode was primarily applied as an environmental sensor for the simultaneous and selective determination of Cd2+ and Pb2+ ions in water samples. The detection limit for Cd2+ and Pb2+ ions was found 25 and 14 mg L-1, respectively