Amperometric detection of dopamine based on tyrosinase-SWNTs-Ppy composite electrode

A novel 3-dimensional single wall carbon nanotubes (SWNTs)-polypyrrole (Ppy) composite was prepared as an electrode by chemically polymerizing polypyrrole onto SWNTs using a LiClO(4) oxidant. This composite electrode was characterized by scanning electron microscopy (SEM) and cyclic voltammetry with 1 mM [Fe(CN)(6)](-3)/[Fe(CN)(6)](-4). The SWNTs were thickly coated with chemically polymerized polypyrrole and the composite had many surface pores and crevices which could enhance mass transfer. The SWNTs-Ppy composite electrode showed a large specific surface area (30 m(2)/g) and a good reproducible current response, at about 100 times the peak current of a glassy carbon electrode (GCE). The diffusion coefficient was calculated to be 4.81x10(-6) cm(2)/s. As a biosensor application, tyrosinase was immobilized on the functionalized SWNTs and tyrosinase-SWNTs-Ppy composite was prepared in the same manner. This tyrosinase-SWNT-Ppy composite electrode was used for amperometric detection of dopamine in the presence of ascorbic acid and showed high sensitivity (467 mA/M cm(2)) and lower detection limit (5 microM) compared to previous reports.